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Carijoa riisei is an invasive octocoral whose dispersal in the tropics has increased considerably in recent years. This study evaluated the changes in the benthic fauna assemblages associated with C. riisei growing on rocks from a sea port and on the metal of a submerged shipwreck in the bays of Manzanillo, Colima, in the Mexican Central Pacific. Quarterly samples were collected between April 2021 and January 2022, with the presence or absence of C. riisei. The effect of C. riisei on the benthic fauna according to the type of substrate was evaluated with PERMANOVA models. The presence of C. riisei was found to affect taxonomic diversity. In the absence of the octocoral, 209 species were recorded, whereas in its presence, 190 were found. The decline of taxa occurred at the level of families, genera, and species. The interaction of the presence/absence of C. riisei and substrate generated significant changes in the Shannon (1D) and Simpson (2D) diversity indexes. However, the presence of C. riisei coincided with higher abundances of Ophiothela mirabilis, Ericthonius brasiliensis, and Pseudobranchiomma schizogenica. In conclusion, the snowflake coral favors the dominance of some species and reduces the biological diversity of several taxa, mainly mollusks, polychaetes, sipunculids, and anthozoans, generating significant changes in the structure of benthic communities. This study highlights the need to evaluate species composition in areas where the octocoral grows, to determine whether its presence has an ecological impact and whether control measures are required. [ABSTRACT FROM AUTHOR]

Marine urbanization promotes the addition of hard substrata that barely resembles natural substrate nearby. We manipulated habitat topography in five marinas across one of the most populated regions from the Southwestern Atlantic Ocean to describe the effect of habitat complexity on the diversity of benthic communities across sites with distinct conditions and biotas. The highest biomass was found in the two marinas under high pollution and freshwater disturbances, regardless of habitat complexity. Habitat topography did not affect species richness but determined the structure of sessile communities in all marinas. The structure of mobile communities was affected only in the most diverse site, increasing the abundance of isopods. In general, fragile ascidians, hydrozoans, and non‐calcified polychaetes dominated complex habitats, while structurally defended animals such as barnacles, serpulids, and encrusting bryozoans dominated simple habitats, suggesting that dominant species are selected by habitat complexity based on their morphological traits. However, the final community structure was also determined by differences across marinas, suggesting that the effect of increasing habitat topography is mostly site‐specific. Therefore, strategies to minimize the disparity between natural and artificial habitats must consider historic local community and a multiple stressors scenario. [ABSTRACT FROM AUTHOR]

Several attempts have been made to find universal zonation schemes for the benthic fauna in sandy beaches. Usually, the nature and number of zones are not fixed and depend on the beach type and temporal changes in environmental characteristics. We characterized spatial and temporal variations in the structure of macrobenthic communities on an Amazonian macrotidal sandy beach (Farol Beach, Algodoal‐Maiandeua Island, Brazil). Samples (macrobenthos and sediments) were collected during the rainy (March 2012 and 2013) and dry seasons (September 2011 and 2012) at six equidistant sites (50 m apart) from the high tide water mark to the swash zone. The physical gradients influenced the faunal distribution, with significant seasonal variations. Density and diversity increased seaward, while increasing moisture, organic matter content, and fine grains in sediments. Two faunal zonation schemes were observed. In the dry season, three faunal zones were distinguished: upper‐intertidal, mid‐intertidal, and low‐intertidal, whereas in the rainy season, only two faunal zones were distinguished: upper‐intertidal and low‐intertidal. In the rainy season, the physical gradients along the intertidal appeared to be smooth, allowing the expansion of the upper‐tidal zone. This study provides novel insights into macrobenthic distribution patterns, reinforcing that tropical macrotidal beaches have unique characteristics that strongly influence macrobenthic distribution patterns. [ABSTRACT FROM AUTHOR]

Determining the drivers of key ecological processes of commercial marine species is important to acquire basic and essential knowledge for fisheries management and conservation. Here we report on a long‐term monitoring of the settlement of the European spiny lobster, Palinurus elephas, the most commercially important spiny lobster species in the Mediterranean and north‐eastern Atlantic. Densities of recently settled individuals (early benthic juveniles – EBJs) were recorded annually, as an approximation to annual settlement, from 2000 to 2016 (17 years) in three zones of the north‐western Mediterranean: Catalonia (CAT), the Columbretes Islands (COL), and the Balearic Islands (BAL). Settlement, the end point that integrate most of the variability occurred during dispersion, is a complex ecological process governed by the interaction of biotic and abiotic factors that can be in turn influenced by the atmospheric and oceanographic conditions. Using linear regression of the size structure of EBJs, we demonstrate that settlement occurs synchronously in the three study zones. Densities of EBJs were handled as time series, and regression analysis revealed that CAT and COL covaried significantly, but none of them with BAL. Therefore, CAT and COL were analysed together using generalized linear model and much of their joint variability was explained by the mesoscale oceanographic index IDEA. Settlement in BAL showed a different pattern, explained by the joint effect of the atmospheric oscillations NAO and WEMO. Complexity of P. elephas settlement cannot be fully accounted neither for CAT‐COL nor for BAL because settlement seems be driven by more complex unknown multi‐factorial processes. Therefore, further studies are necessary to gain insight into other factors that allow short‐ or medium‐term predictions of settlement. Expanding the study area across the Mediterranean would also allow establishing a complete knowledge of the ecology of the species applicable to the management of the fishery. [ABSTRACT FROM AUTHOR]

Due to the presence of the complex life cycles involving a benthic adult and a pelagic larval phase, the study of benthic community dynamics cannot ignore investigations of the processes occurring in the water column. Current investigations focus mainly on larval dispersal from an evolutionary and a biogeographic perspective, taking into account also population connectivity, conservation planning and coastal management. In the present paper we underline the need to improve knowledge of the main traits of marine invertebrate life cycles, highlighting the limits and challenges of current approaches. Firstly, we summarized the changing approaches within community studies, following the paradigm shifts found in recent marine ecological research, from supply-side ecology to connectivity, and involving the concepts of open and closed populations. Secondly, we analysed the main larval traits influencing dispersal, paying particular attention to pelagic larval duration in light of the few available data for connectivity studies. The difficulty in estimating many of the main traits of larval ecology make numerical simulation fundamental for a better understanding of the relationship between propagule dispersal and seawater dynamics, both being highly variable. We conclude that some essential biological information is still lacking for the proper integration of the modeling approaches. Thus it is necessary to further investigate the life-cycle traits and physiological and ecological characteristics of each species, an approach known as autecology or natural history. All too frequently modern ecologists ignore such reductionist approaches, although they are essential for a full understanding of processes, such as connectivity and metapopulation dynamics. [ABSTRACT FROM AUTHOR]

The aim of this study was to attempt to fill current knowledge gaps on midlittoral Mediterranean biodiversity at local and regional scales, by using benthic polychaetes as a model taxon. Two different data sets were analysed: (i) a quantitative data set from the two Natural Geography in Shore Areas (Na GISA) study sites in Crete and (ii) a qualitative data set from multiple sites across the Mediterranean. At the local scale, the results provide evidence that (i) discrete species communities are formed in midlittoral Mediterranean habitats, which vary by geographical location and year, depending on the scale of observation; (ii) macrophyte coverage and Chl- a are the only environmental variables associated, albeit weakly, with the above pattern; (iii) although naturally disturbed, the Cretan Na GISA sites do not seem to experience any anthropogenic stress; (iv) environmental heterogeneity and history seem to be much less important in shaping the polychaete communities than inter-specific interactions; however, it is not possible to specify at this stage whether local or regional processes or even their interactions may shape the polychaete communities. At the regional scale, the results indicate that (i) the only factor that seems to be involved in the regional pattern is the identity of the study providing the data sets, which implies variability and bias in how research projects are carried out, from the sampling design through to data collection and analysis; (ii) the Cretan Na GISA sites may be considered as representative of the habitat in the Mediterranean, under certain conditions. [ABSTRACT FROM AUTHOR]

Recurrent climate-induced mass mortality episodes have been recorded in the Mediterranean Sea over the past 15 years, affecting rocky benthic communities. In this study, we provide for the first time a report on the annual mortality events of benthic sessile invertebrates occurring in the eastern part of the Adriatic Sea. Over the course of 14 consecutive years, we studied the sea temperature gradient to a depth of 40 m and found an abnormal summer warming trend and an increased frequency of above-average temperatures. Mortality events were recorded in the summers of 10 observed years, in particular in 2009, when the highest mortality rates were recorded. Late in summer 2009, extensive mass mortality of sessile invertebrates was observed in the entire Eastern Adriatic Sea. We performed an analysis of selected target benthic species associated with mass mortality events with inter-regional differences in hydrological and temperature conditions. We were able to characterize the mortality event by studying five areas covering the northern, central and southern regions of the Eastern Adriatic Sea. The degree of impact on each study area was quantified at 28 sites by estimating the proportion of affected target species. According to the obtained data, the northern sites (Cres area) were the least affected, whereas sites in the Central and Southern Adriatic [Telašćica and Lastovo Nature Parks, Mljet National Park ( NP)] displayed the highest impact. In summer 2009, sea surface temperatures reached values of 28 °C in the Cres area and 30 °C in Mljet NP. These thermal conditions were concomitant with moderate to severe mass mortalities of benthic populations. Mass mortality events reached depths of 45 m in most parts of the affected areas. Amongst studied species, the scleractinian coral and gorgonian populations suffered the most extensive damage during the mass mortality events. [ABSTRACT FROM AUTHOR]

The role of small-scale (<10 km) habitat availability in structuring deep-sea hard substratum assemblages is poorly understood. Epibenthic megafauna and substratum availability were studied on steep slopes at the Mid-Atlantic Ridge from May to July 2010 northwest, northeast, southwest and southeast of the Charlie-Gibbs Fracture Zone ( CGFZ; 48-54°N) at between 2095 and 2601 m depth. Megafauna were six times denser north of the CGFZ compared with the south and differences in density were almost entirely driven by sessile fauna. There was no significant difference in habitat availability amongst sites. Rocky substratum made up 48% of the total area surveyed, with individual transects having between 0% and 82% rock. Assemblage structures were different amongst all superstations. The north was dominated by demospongids and hexactinellids, whereas the southern superstations were dominated by anthozoans and hexactinellids. Differences in megafaunal assemblages north and south of the CGFZ primarily reflected variations in demospongid and anthozoan species composition. With 213-1825 individuals·ha−1, and 7-24 species per superstation, hexactinellids were the most species-rich (36 species) and cosmopolitan taxa at the study site, supporting observations elsewhere along the ridge and in the CGFZ. The absence of significant differences in substrata availability suggested alternative drivers for density or percentage cover. The amount of hard substratum available only limited sessile megafauna density at one transect that was entirely covered with sediments. Species richness was highest for areas with intermediate values of substratum coverage (35-43% rock). [ABSTRACT FROM AUTHOR]

Recent settlers of many marine benthic invertebrates are cryptic, which exposes them to a suite of animals that differs from those they may experience as adults, potentially resulting in interactions causing mortality and/or reducing growth. Previous field experiments have indicated that such is the case with small juvenile green sea urchins Strongylocentrotus droebachiensis but which taxa are responsible for the mortality and reduced growth was not determined. A laboratory study was conducted to examine the effects of small macro-benthic invertebrates, specifically chitons, scaleworms and larger juvenile conspecifics, as well as the full suite of cobble-dwelling organisms, on the mortality, growth and behaviour of small (<3 mm) juvenile sea urchins. The likelihood of survival of small juvenile sea urchins was lower in the presence of larger juvenile sea urchins or with the full suite of cobble-dwelling organisms than in the absence of animals. The small juvenile sea urchins survived and grew the best when they were with chitons and scaleworms. The behaviour of small sea urchins with the full suite of cobble-dwelling organisms was more cryptic than the behaviour of urchins with scaleworms. This study indicates that interactions with the suite of small organisms living amongst cobbles can affect survival, growth and behaviour of small juvenile sea urchins, and that larger juvenile sea urchins can be a source of mortality for smaller conspecifics. [ABSTRACT FROM AUTHOR]

Benthic organisms are among the most diverse and abundant in the marine realm, and some species are a key factor in studies related to bioengineering. However, their importance has not been well noted in biogeographic studies. Macrofaunal assemblages associated with subtidal beds of the ribbed mussel ( Aulacomya atra) along South America were studied to assess the relationship between their diversity patterns and the proposed biogeographic provinces in the Southeastern Pacific and Southwestern Atlantic Oceans. Samples from ribbed mussel beds were obtained from 10 sites distributed from the Peruvian coast (17°S) to the Argentinean coast (41°S). The sampling included eight beds in the Pacific and two in the Atlantic and the collections were carried out using five 0.04 m2 quadrants per site. Faunal assemblages were assessed through classification analyses using binary and log-transformed abundance data. Variation in the size and density of mussels, and in the species richness, abundance and structure of their faunal assemblages were tested using a permutational multivariate analysis of variance. Faunal assemblages showed a north-south latitudinal gradient along both the Pacific and Atlantic coasts. Binary and abundance data showed a difference in the resulting clustering arrangement of Pacific sites between 40°S and 44°S, indicating a pattern of continuity in the species distribution associated with biological substrates. At a regional scale, the distribution of species along the South American coast matched the general provincial pattern shown by prior studies, which show two biogeographic units on the Pacific coast separated by an intermediate (probably transitional) zone and a single province on the Atlantic coast extending up to Northern Argentina. Biological substrates such as ribbed mussel beds play an important ecological role by making a similar habitat type available on a large scale for a variety of invertebrate species. Despite such habitat homogeneity, however, the associated fauna exhibit marked distribution breaks, suggesting strong constraints on dispersal. This therefore suggests that macrofaunal assemblages could possibly be used as biogeographic indicators. [ABSTRACT FROM AUTHOR]

Understanding species distributions and their community structure is increasingly important when taking an ecosystem-based approach to conservation and management. However, knowledge of the distribution and community structure of species in mid-range trophic levels ( e.g. macroinvertebrates) is lacking in most marine ecosystems. Our study aimed to examine the spatial distribution and community-level biogeographic patterns of common kelp forest-rocky reef macroinvertebrates in Southern California and to evaluate the effects of environmental gradients on these communities. Quantitative SCUBA surveys were used to estimate macroinvertebrate densities at 92 sites from 2008-2012. Non-metric multidimensional scaling was used to evaluate spatial patterns of macroinvertebrate communities among Regions. We found that kelp forest-rocky reef macroinvertebrate communities are distinct among different island and mainland regions, and their community patterns exhibited a strong relationship with an environmental gradient ( i.e. sea surface temperature) even after controlling for geographic distance between sites. High abundances of urchin species ( Strongylocentrotus purpuratus and Strongylocentrotus franciscanus) were strong drivers of regional differences. Macroinvertebrate community patterns were driven by characteristic species that were typically more prevalent at warmer or colder sites. Our results provide the first quantitative analysis of macroinvertebrate community structure within the California kelp forest ecosystem. We also describe the distribution and abundance of 92 conspicuous kelp forest-rocky reef macroinvertebrates among nine pre-defined Regions. This study provides important preliminary information on these macroinvertebrate species that will be directly useful to inform management of invertebrate fisheries and spatial protection of marine resources. [ABSTRACT FROM AUTHOR]

Marine benthic surveys and monitoring programs may have several goals. When the aim of such studies is to reveal and describe gradients in species composition, the gain in ecological insight achieved by the study depends on how well the spatial variability of species' occurrence and abundance within the study area is covered by the sampling design. The common practice in such programs is to collect four or five grab samples from each visited site to capture the site's species composition. The rationale for this practice is based on the aim of capturing a large proportion of species at a specific site ( i.e. point). We argue that this practice has been established without taking Iterative approaches into account, such as decreasing the sampling effort at each site and instead increase the number of sites visited. The collection and processing of data from marine sediment ecosystems are time-consuming and, thus, expensive. Therefore, finding the optimal trade-off between the number of sites visited and the number of samples per site is important. We examined this trade-off by exploring how reduction of sampling effort per site affects the stability and recovery of gradients in species composition of marine benthic macrofauna. Our full data set consisted of four grab samples from each of 28 sites from the inner part of the Oslofjord, SE Norway. Procrustes analysis and calculation of Kendall's rank correlation coefficients showed that the main gradient in species composition extracted by detrended correspondence analysis of data sets with reduced per-site sampling effort closely resembled the main gradient extracted for the full data set. Our results therefore suggest that marine benthic surveys that aim to identify the main gradient structure of species composition and relate this structure to main environmental complex gradients are likely to benefit from reducing the sampling effort at each site and, instead, increasing the number of visited sites. We argue that coverage of both the variation in species composition and the environment in the study area will then be improved. Monitoring programs with other aims than to identify the main gradients in species composition may also benefit from the adoption of a many-sites, one-sample sampling strategy. This may be particularly true if additional sampled sites are based on a stratified sampling strategy that ensures that the spatial variability in the study area is accounted for. [ABSTRACT FROM AUTHOR]

Mangroves along the Sudanese Red Sea coast are under constant anthropogenic pressure. To better understand the influence of mangrove clearance on the intertidal benthic community, we investigated the composition, biodiversity and standing stock of the macrofauna communities at high-, mid- and low-water levels in three contrasting habitats: a bare sand flat, a cleared mangrove and an intact mangrove. In addition, a community-wide metric approach based on taxon-specific carbon and nitrogen isotope values was used to compare the trophic structure between the three habitats. The habitats differed significantly in terms of macrofaunal standing stock, community composition and trophic structure. The high- and mid-water levels of the intact mangroves showed a distinct macrofaunal community characterized by elevated densities and biomass, largely governed by higher decapod and gastropod abundances. Diversity was similar for cleared and intact mangroves, but much lower for the bare sand flat. Community-wide metrics indicated highest trophic diversity and community niche breadth in the intact mangroves. Differences between the cleared and intact mangroves can be partly attributed to differences in sediment characteristics resulting from mangrove clearance. These results suggest a significant impact of mangrove clearance on the macrofaunal community and trophic structure. This study calls for further investigations and management actions to protect and restore these habitats, and ensure the survival of this ecologically valuable coastal ecosystem. [ABSTRACT FROM AUTHOR]

The fluctuations in densities or biomass of a number of invading and native polychaete and mollusc species in the Southwest Netherlands were compared over a period of 20 years. For recent invaders a lag phase of 7-10 years occurred after their first appearance, followed by an exponential increase in abundance or biomass for 2 - 3 years. High numbers and biomass then continued for about 5 years, followed by a strong decline. The total sequence from introduction to decline lasted about 15 years. The densities or biomass of invaders appearing decades or even centuries ago in the Delta area have fluctuated in a similar manner to those of native species, indicating that the densities or biomass of invading species after a 15-year period of strong changes become governed largely by the same environmental factors as native species. The conclusion may be that after some decades, invading species can become part of a balanced co-existence with the native species, and that this may yield a net gain in the overall diversity. [ABSTRACT FROM AUTHOR]

The Arabian Sea is characterized by a mid-depth layer of reduced dissolved oxygen ( DO) concentration or oxygen minimum zone ( OMZ - DO concentration <0.5 ml·l−1) at ~150-1000 m depth. This OMZ results from the flux of labile organic matter coupled with limited intermediate depth water ventilation. Generally, benthic animals in the OMZ have morphological and physiological adaptations that maximize oxygen uptake in the limited oxygen availability. Characteristics of OMZ benthos have been described from only a few localities in the Arabian Sea. We measured the bottom water DO and studied the characteristics of infaunal macrobenthos of the Indian western continental shelf by collecting samples at 50, 100 and 200 m in depth from 7° to 22° N. The DO values observed at 200 m (0.0005-0.24 ml·l−1) indicated that this area is lying within an OMZ. Five major taxa, namely Platyhelminthes, Sipunculoidea, Echiuroidea, Echinodermata and Cephalochordata were absent from the samples collected from this OMZ. In general, declines in total macrobenthic density and biomass and polychaete species richness and diversity were observed in this OMZ compared with the shallower depths above it. Community analyses of polychaetes revealed the dominance of species belonging to families Spionidae, Cirratulidae and Paraonidae in this OMZ. Low oxygen condition was more pronounced in the northern continental shelf edge (≤0.03 ml·l−1), where the majority of spionids including Prionospio pinnata and cirratulids were absent; whereas amphipod, isopod and bivalve communities were not impacted. [ABSTRACT FROM AUTHOR]

The present study explores the distribution of the invasive herbivore fish Siganus luridus ( Rüppell 1829) and its relationship to native herbivores and macroalgal assemblages in the shallow sublittoral of the Cyclades Archipelago, Aegean Sea, Greece. In situ underwater surveys of herbivore abundance (fishes and sea urchins) and algal coverage were carried out at 180 sampling sites in 18 islands. Siganus luridus accounted for 17% of the total herbivore abundance, with a decrease in relative abundance from the southeastern to the northwestern islands. In Santorini Island (in the southeast of the study area) S. luridus abundance accounted for 90% of the total herbivore fish abundance, while in Kea Island (at the northwestern limit of the study area), S. luridus was absent. The spatial variation of minimum sea surface temperature is possibly the reason for its distributional pattern. Siganus luridus abundance was found to be positively correlated to the native herbivore Sparisoma cretense ( Linnaeus 1758). A significant negative relationship was found between the abundance of the invasive species and the sum of erect and canopy algae cover ( Dictyotales and Cystoseira spp.), which are the main components of its diet in the region. On the other hand, its occurrence was particularly high in barren sites. The results arising from this study reinforce evidence from studies in the Eastern Mediterranean Basin that the expansion of the invasive species S. luridus may have profound impacts on native communities in the Mediterranean infralittoral zone. [ABSTRACT FROM AUTHOR]

The vertical distribution of macrobenthic fauna, heavy metals, and other physico-chemical and biological characteristics of the sediments were studied in three sediment layers (0-7, 8-14, 15-21 cm) at seven stations in the Ubatuba region, north coast of São Paulo State, Brazil at several temporal and spatial scales. Six stations were located in the inner bay near the riverine run-off, and one was outside the bay, distant from the riverine influence. The samples were collected four times in 1 year, on a seasonal basis. Sediments were basis comprised predominantly of very fine sand and the vertical distribution of grain size was uniform to a depth of 21 cm in all stations. Higher values of total organic matter, organic carbon, sulphur, heavy metals and phaeopigments were recorded at the inner Ubatuba Bay stations, probably due to the riverine influence. C/ N ratios indicated a mixed origin of organic matter with a major contribution of terrestrial material in the inner stations. The vertical distribution of heavy metals showed a slight decline with sediment depth in the inner stations, indicating the present contribution. Most of the macrofauna was found at the surface sediment layer. Biological data showed that in the inner stations of Ubatuba Bay, which are under the influence of urban sewage and are moderately polluted, the fauna was distributed more superficially within the substrate than in St. 7, which is located in the external portion of the bay distant from sewage inputs. The environmental quality of the sites studied varied little throughout the year, at least in relation to the variables considered here. Temporal variation in the vertical distribution of benthic fauna was not evident in the four sampling surveys analysed. Only minor changes in the vertical distribution of the total fauna were detected in the seasonal scale, with the organisms located less deep within the sediment column in summer, indicating some influence of the tourism impact and/or rainy season. [ABSTRACT FROM AUTHOR]

This study describes changes in abundance of hyperbenthic zooplankton (including meroplankton) and benthic colonists at the seasonally hypoxic seabed of Saanich Inlet, British Columbia, Canada. We used the Victoria Experimental Network Under the Sea (VENUS) cabled observatory to measure water properties and to sample hyperbenthos with a sediment trap at 97 m from September 2008 to September 2009. Some faunal groups exhibited seasonal reproduction, and abundance peaked during their reproductive periods. These included larvae of the barnacle Balanus crenatus, and the crabs Petrolisthes eriomerus, Oregonia gracilis, and Lophopanopeus bellus bellus. Other groups were most abundant in spring and summer when food and oxygen levels were highest and temperature was lowest. These included cumaceans, the siphonophore Diphyes sp., the bryozoan Triticella pedicellata, and tintinnids. We also collected benthic colonists, predominantly bryozoans and polychaetes, on colonization plates deployed in spring/summer 2008, fall 2008/winter 2009, and spring/summer 2009. The total abundance of colonists and of bryozoans did not vary seasonally or with substrate complexity, whereas polychaetes were more numerous in spring/summer deployments and on a highly complex substrate. Taxon richness of colonists was higher in spring/summer 2008 than in fall 2008/winter 2009, whereas an anoxic episode in spring/summer 2009 reduced richness to similar values with that of fall 2008/winter 2009 levels. Substrate complexity had no effect on richness. Juvenile squat lobsters, digitally imaged in fall 2008/winter 2009, were most numerous when oxygen levels were lowest and potentially excluding larger predators. Our study illustrates how season, food availability, temperature, and oxygen can interact to shape community structure in a seasonally hypoxic habitat. [ABSTRACT FROM AUTHOR]

Routine monitoring of the quality status of water bodies demands the best cost-benefit relation and sample-size reduction is therefore welcomed. However, great caution is needed because such reduction affects the accuracy and variation of the results. In the present study we tested the influence of sample size (number of replicate samples) on reference condition values and within-sample ecological quality ratio (EQR) variability of six commonly used ecological indices (taxa richness, Shannon-Wiener diversity, AMBI, Medocc index, Bentix and M-AMBI). Analysis of soft-bottom benthic invertebrate data from Slovenian coastal waters showed that sample size influenced the reference condition values of richness/diversity indices (taxa richness and Shannon-Wiener diversity) but not of the sensitivity/tolerance indices (AMBI, Medocc index, Bentix). Increased sample size decreased the within-sample EQR variability and, concomitantly, increased the accuracy of site ecological status classification for all indices. The size of EQR variability differed depending on the index used. EQR variability of M-AMBI, an index composed of metrics with different within-sample EQR variability, was statistically the same as that of the metric with the lowest within-sample EQR variability. Whether this is a common principle for multimetric indices remains to be confirmed. Based on these results, the use of at least three replicates is suggested to obtain reliable measures of reference condition and EQR for the assessment of ecological status. This level of replication is particularly necessary in areas with high diversity and environmental patchiness, and when richness/diversity measures and indices that include these measures are used. [ABSTRACT FROM AUTHOR]

The life cycle of the stoloniferan Cornularia cornucopiae (Pallas, 1766) (Anthozoa: Octocorallia) was studied from March 2009 to October 2010 on the rocky cliff of the Conero Promontory (North Adriatic Sea, 43°34.865′ N, 13°34.320′ E). In this area the species showed unusual high densities never recorded in other sites of the Mediterranean Sea. The density trend of the species showed a marked seasonal cycle, with a winter minimum of about 1000 polyps m−2 and a summer maximum of about 30,000 polyps m−2. In accordance with other Mediterranean literature data, polyps were fertile during spring-summer, from March to August, but the number of eggs per polyp continuously decreased during this span of time. Variations of polyp density were strongly correlated to water temperature, which can be considered the main environmental factor triggering this seasonal behaviour. The possibility, for C. cornucopiae, to face adverse winter conditions is probably related to the presence of a characteristic perisarcal envelope covering the stolon and the calyx of each polyp, which isolates the living tissues from the exterior. During winter, polyps degenerate but the stolons remain dormant inside their envelopes. The perisarc covering represents a morphological convergence of C. cornucopiae with benthic hydrozoans. As the latter, the studied stoloniferans are able to live in habitats characterized by periodic favourable conditions thanks to a seasonal life strategy. A similar trend is shared also by other important components (cnidarians and some sponges) of the filter-feeding community of the North Adriatic Sea. Differently to the Western Mediterranean basin, this area is characterized by high food availability all year around, so benthic organisms are strongly constrained by the very low winter temperatures. [ABSTRACT FROM AUTHOR]

The estimation of the strength of the interaction between species is key for understanding the organization of ecological communities. Although experimental and observational studies have estimated per capita interaction strength for individual consumers, no previous study has used such estimates for predicting the impact of a community of consumers on their prey in the field. Here we evaluate experimental estimates of per capita interaction strength and impact of consumers on prey by comparing our impact predictions with real-time series of prey abundance. We conducted aquarium experiments to estimate the effects of seven herbivore species on survival of early life stages (microscopic sporophytes) of the giant kelp, Macrocystis pyrifera. We also estimated the impact of a community of herbivores on a cohort of kelp sporophytes using time series (1983-2000) of herbivore abundance in the Point Loma, San Diego (California), kelp forest. The underlying assumption was that maximum herbivore impact on microscopic recruits is realized only after a disturbance removes the giant kelp plants and thus releases the recruits. Our model was successful in predicting the prevention of giant kelp recruitment, which occurred when the abundance of weak interactors increased above a threshold. These results indicate that experimental estimates of maximum per capita interaction strength can be used to predict strong consumer impacts. [ABSTRACT FROM AUTHOR]

Onega Bay is the largest bay in the White Sea, characterised by shallow depth, a range of sediment types and strong tidal currents. All these factors provide conditions for high species richness and biomass. This study reviews data from three surveys of sublittoral macrobenthos undertaken by Russian institutes: the benthic survey covering the entire Onega Bay in 1952; the survey performed in the northern part of the area in 1981/90, and a study carried out in 2006 in the eastern part of the bay. In total, data from 107 stations were analysed. The data in different surveys were collected by different grab types. The datasets of both 1981/90 and 2006 overlap the 1952 survey area. The pattern of biomass distribution was consistent between the years of survey and was characterised by the low biomass at the northern periphery of the bay and the highest biomass observed in the coastal waters of the Solovetsky Islands. Bivalves and cirripeds (mostly Modiolus modiolus, Arctica islandica, Balanus balanus and Verucca stroemia) dominated in biomass. Neither the biomass share of dominant species nor the frequency of occurrence of several common species in these groups changed markedly between 1952 and 1981/90. Although the results of the 2006 survey appear somewhat different from the patterns of previous years, this does not indicate major changes in the benthic communities, because the survey in 2006 was designed in a different way and its overlap with the 1952 survey was minimal. However, the dominant species (by biomass) - A. islandica, M. modiolus and V. stroemia- held their leading positions. Results of the multidimensional scaling analysis based on the biomass data for all taxa encountered in the 1952 survey indicate considerable mixing of the samples from all surveys. This may be interpreted as the absence of major shifts in the sublittoral communities of the macrobenthos of Onega Bay at decadal scale. This kind of stability may be explained by an oceanographical regime resilient to climate variation and a relatively low anthropogenic environmental impact when compared to other shallow European seas. [ABSTRACT FROM AUTHOR]

Benthic epifauna was sampled in an area of 10 × 10 nautical miles in the German Bight. Samples were taken in January and July/August from 1998 to 2009. The ecological functioning of the epifaunal community was assessed using biological traits analysis (BTA). Twelve ecological traits of 26 epifaunal species were considered and analysed using non-metric multidimensional scaling (nmMDS). Anomalies in the sea surface temperature (SST) close to the study area were mainly above the long-term mean during the study period. SST was exceptionally high during the autumn months between 2002 and 2006. Additionally, the cold winter of 1995-96 was clearly reflected in strong negative SST anomalies. Trait composition changed in 2002, mainly due to a decreasing trend of traits related to an opportunistic life mode from 1998-2002. Traits related to reproduction showed a much clearer response to the high autumn SST anomalies from 2002 to 2006 than other traits. We concluded that the cold winter resulted in an increase in opportunistic species in the study area followed by characteristic post-disturbance succession stages to the point of an established community in 2002. This indicates a recovery time of epifaunal communities in the German Bight of 7-8 years. Additionally, the results give evidence that climate-induced variability of SST in the German Bight affects mainly the reproduction of epifaunal species rather than other traits such as feeding type. [ABSTRACT FROM AUTHOR]

Recent studies highlight an increase in the frequency and intensity of marine mass mortalities of several species over the past 30-40 years, mainly in tropical and temperate areas. In the Mediterranean Sea these episodes particularly affect benthic suspension feeders, such as sponges and cnidarians. The main objective of this work was to document the loss of one of the main Mediterranean seascapes, Paramuricea clavata forests at the Marine Protected Area of Tavolara Punta Coda Cavallo, Sardinia (Italy), during the summer of 2008. Data regarding colony height, density, level of damage, and microbiological community were collected at two sites. Such parameters help us understand how mass mortality mechanisms act on this ecosystem engineer. We identified a change in size class distribution following a mass mortality that leaves mainly small colonies with a decrease in habitat complexity. Several tests on water chemistry demonstrate that the mortality event was not caused by local contamination. Moreover, microbiological tests on potential pathogenic agents suggest that bacteria belonging to the genus Vibrio are present as an opportunistic and not an etiological cause of P. clavata mortality events. Possible restoration approaches are discussed. [ABSTRACT FROM AUTHOR]

The EC Water Frame Directive (WFD) states that all coastal water bodies must achieve 'good ecological status' by the year 2015. A range of different classification methods have been developed and used to define ecological status to support the WFD. The aim of this study was to compare the effects of using two different mesh sizes of sieve (1.0 and 0.5 mm) on zoobenthic assemblages and on the ecological status of benthic macrofauna (using the Brackish water benthic index, BBI) in three ecologically distinct archipelago areas (Inner, Middle and Outer) in the Åland Islands, Northern Baltic Sea. We performed a biological trait analysis (BTA) to evaluate differences in the functional (trait) diversity of macrofauna collected using different mesh sizes and estimate the ecological relevance of mesh size. The results showed that sieve mesh size had significant effects on the recorded number of species, abundance, and total biomass of the zoobenthos. Small-bodied species and juveniles ( e.g. Macoma balthica) were not observed when using a 1.0-mm mesh. The ecological status ( sensu WFD) was only slightly affected by the mesh size, and all areas had good or high ecological status. BTA showed a difference in trait composition when using 0.5- or 1.0-mm mesh, particularly in the Outer area, where the proportion of small-sized species was high. Our results highlight how biological traits, in addition to species number and biomass, can play a key role when analyzing ecosystem structure for assessment and classification of coastal ecosystems. We show that combining traditional monitoring for the EU WFD with a functional analysis strengthens our ability to interpret environmental quality, and thus increases the precision of our advice for management purposes. [ABSTRACT FROM AUTHOR]

Biological communities on seamounts are widely regarded as being distinct from those in other offshore habitats, but it is unclear what factors drive any differences. We used invertebrate and algal data from the extensive REVIZEE benthic surveys from the continental margin and seamounts in the Southwest Atlantic Ocean off Eastern Brazil to investigate environmental predictors of seamount assemblage composition. We found that seamount summit samples were significantly different from those of the continental shelf for both invertebrates and algae. Invertebrate samples from the shelf showed more spatial variability than those from seamounts, congruent with the increased variability in both sampled sea-floor habitats and oceanographic conditions recorded along the continental margin. The most important environmental predictors of assemblage composition across all habitats were distance from shore, temperature, dissolved oxygen and particulate organic carbon for invertebrates, and distance from shore, nitrate and phosphate concentrations for algae. Only distance from shore for invertebrates, and distance from shore, nitrate and phosphate concentrations for algae were consistently emphasised in analyses restricted to seamount and island samples. We found no support for the hypothesis that seamount assemblages in this region become less species rich with distance from the continental margin. However, algal samples did form a serial gradient of compositional turnover with distance from shore. In summary, the seamounts shared the same species pool as nearby continental margins but samples contained a different, equally rich, assemblage of species. [ABSTRACT FROM AUTHOR]

Seamounts have been described as island habitats harbouring a unique fauna, and as biodiversity hotspots with high rates of endemism. However, recent research suggests that these generalisations are inappropriate and poorly supported, though appropriate on and off seamount comparative data are lacking. This study uses quantitative data derived from video analysis to compare epibenthic megafaunal community composition, diversity and potential species endemism on two seamounts and one bank in the Rockall Trough region of the NE Atlantic. Sample data were standardised for substratum type across all three features and as far as possible for depth and geomorphological variation. The results suggest that under similar environmental conditions, e.g. similar substratum, depth and geomorphology, there is little difference between the communities of the bank and seamounts in the Rockall Trough. Where differences are observed, the ‘guyot’ seamount is as different to the conical seamount as it is to the bank. The seamounts are no more or less diverse than the bank; endemism is low or non-existent. The results are discussed in the context of the common generalisations made concerning seamount communities and the implications for conservation and management of the deep sea. [ABSTRACT FROM AUTHOR]

Seamounts have often been viewed as specialized habitats that support unique communities; this notion has given rise to several hypotheses about how seamount ecosystems are structured. One, the ‘seamount oasis hypothesis’, predicts that invertebrates are more abundant, speciose and attain higher standing stocks on seamounts compared to other deep-sea habitats. Because this hypothesis has remained untested for biomass, we ask two questions: (i) Do seamounts support a higher benthic biomass than nearby slopes at corresponding depths? (ii) If they do, which particular taxa and trophic groups drive observed difference in biomass? Analysis of more than 5000 sea-floor images reveals that the mean biomass of epibenthic megafauna on 20 southwest Pacific seamounts was nearly four times greater than on the adjacent continental slope at comparable depths. This difference is largely attributable to the scleractinian coral Solenosmilia variabilis, whose mean biomass was 29 times higher on seamounts . In terms of trophic guilds, filter-feeders and filter-feeders/predators made up a significantly greater proportion of biomass on seamounts, whereas deposit feeders and those with mixed feeding modes dominated at slope habitats. Notwithstanding support for the seamount oasis hypothesis provided by this study, the hypothesis needs to be critically tested for seamounts in less productive regions, for seamounts with a greater proportion of soft substratum, and in other parts of the oceans where scleractinian corals are not prevalent. In this context, testing of seamount paradigms should be embedded in a broader ecological context that includes other margin habitats ( e.g. canyons) and community metrics ( e.g. diversity and body size). [ABSTRACT FROM AUTHOR]

Benthic communities on seamounts are frequently characterised as being species rich, yet there is considerable variation in observed species richness. Although large-scale patterns of species richness have been described from many marine and terrestrial habitats, their environmental drivers often remain poorly understood. We compared species richness of ophiuroids (brittle-stars) on 60 seamounts throughout the South West Pacific Ocean, and used an information-theoretic approach and generalized linear models to determine the relative importance of predictor variables. Due to high correlation among many environmental variables, we used a reduced set of predictors in an a priori model framework. Temperature was the only environmental predictor of any importance in these models over the bathymetric range of the study. Post-hoc analyses of other potential environmental predictor variables showed that depth, calcite saturation state, temperature range, modelled current velocity and latitude all had some predictive value, but were also highly correlated with temperature or other environmental variables included in the a priori model. Longitude, large-area species richness, habitat suitability for stony corals, and modelled POC flux did not have high predictive value. We hypothesise that temperature affects richness by constraining species distributions; in particular fewer species can tolerate the conditions on relatively warm shallow seamount summits. [ABSTRACT FROM AUTHOR]

Because the nature, tempo and trajectories of biological changes that follow the cessation of trawling are unknown for seamounts, it is unclear whether closing them to trawling will lead to a recovery of the fauna and, if so, over what time scales. This paper reports on a ‘test of recovery’ from repeated towed camera surveys on three seamounts off New Zealand in 2001 and 2006 (5 years apart) and three off Australia in 1997 and 2006 (10 years apart). In each region, seamounts where trawling had ceased were compared to adjacent seamounts where trawling was still active, and to seamounts that had never been trawled. If recovery signals existed, the likelihood of detecting them was high because the seamounts were relatively small and topographically simple, and because quantitative survey methods were employed. Multivariate patterns showed no change in the megafaunal assemblage consistent with recovery over a 5–10 year timeframe on seamounts where trawling had ceased. Results based on the number of species and diversity were equivocal, with some cases of increase and decrease on seamounts where trawling had ceased. A few individual taxa were found at significantly higher abundance in the later surveys where trawling had occurred. We suggest this may have resulted from their resistance to the direct impacts of trawling (two chrysogorgid corals and solitary scleractinians), or from protection in natural refuges inaccessible to trawls (unstalked crinoids, two chrysogorgid corals, gorgonians, and urchins). Alternatively, these taxa may represent the earliest stages of seamount recolonisation. They have potential to be dominant for long periods because the pre-trawling composition of benthic assemblages on seamounts includes taxa that grow slowly and/or have an association with ‘thickets’ of a single keystone stony coral ( Solenosmilia variabilis) that has generated biogenic habitat over millennia. Resilience of seamount ecosystems dominated by corals is low compared to most other marine systems subject to disturbance by bottom trawling because there are no alternative habitats of the same value for supporting associated species, and because trawling typically removes coral habitat from large areas of individual seamounts. Management to conserve seamount ecosystems needs to account for changing oceanographic conditions (ocean acidification), as well as the direct impacts of human activities such as bottom trawling. Networks of spatial closures that include intact habitats over a range of depths, especially <1500 m, and on clusters and isolated seamounts, may be effective by maintaining the resilience of seamount benthic communities. [ABSTRACT FROM AUTHOR]

This study was carried out to test the hypothesis that benthic communities on seamounts are distinct from those of other deep-sea habitats at comparable depths. Analysis of the squat lobster fauna of deep-sea habitats in the Southwestern Pacific revealed that the species composition of assemblages on seamounts was not statistically dissimilar from assemblages on slope and plateau habitat at comparable depths. However, compositional differences were observed between seamount and rise and ridge habitat. Differences in assemblage composition between seamount and ridge habitat were statistically significant for two of the four ridge systems examined. Assemblages on seamounts that were distinct from non-seamount ridge habitat were typically dominated by small-bodied species with an abbreviated larval stage. Various environmental variables were correlated with the observed assemblage patterns observed; depth-related variables may account for differences between seamount and rise assemblages, whilst differences in POC flux likely play a role in determining the assemblage compositional patterns between seamount and non-seamount ridge habitat. Extensive pre-analysis data treatment was required to ensure that multivariate analyses of assemblage data from seamount and non-seamount habitats were robust. Our results confirm the findings of recent studies that found no compositional differences in assemblages from seamount and slope habitats, and support the idea that dissimilarity between seamount assemblages on different ridge systems increases with geographic distance. Further research will be required before the generality of these findings can be confirmed. [ABSTRACT FROM AUTHOR]

Stony (scleractinian) corals are common on seamounts and can form extensive reef-like structures which in turn provide important habitat for associated species. Aggregations of fish also occur on seamounts, which in recent decades have become the target of commercial bottom trawl fisheries that have damaging impacts on benthic communities. Such fisheries occur throughout the world’s oceans, and the majority are located on seamounts about which little is known of their biodiversity or likely fisheries impact. Here we develop an index of risk for stony corals on seamount summits. The index combines a metric of vulnerability measured by the coincidence of seamount summits, target fish ranges and likelihood of coral presence with an assessment of likely fisheries impact derived from a fishing intensity effects study and fishing effort-catch data. We provide spatial maps depicting the locations of vulnerable seamount features, and those at particular risk to bottom trawling. Application of the risk index may help to provide guidance to fisheries or environmental managers faced with balancing fisheries management and habitat conservation. [ABSTRACT FROM AUTHOR]

The importance of suspension-feeding mussels is particularly apparent in benthic communities; however, the role of this feeding strategy on the development of macroalgal and associated invertebrate communities is in general poorly known. The effect of suspension-feeding mussels Mytilus trossulus on benthic communities was studied in an in situ factorial field experiment in the Northern Baltic Sea over one ice-free season. The experiment was performed under different regimes of wave exposure (low and moderate) and on different sedimentary habitats (soft bottom with high organic content, soft bottom with low organic content, and hard bottom). In general the presence of mussels was associated with increased biomass of filamentous algae, herbivores and deposit feeders and decreased biomass of charophytes. The effect of M. trossulus interacted with the effect of exposure and substrate. Stronger responses were observed in moderately exposed than in sheltered areas. The presence of M. trossulus affected charophytes and deposit feeders on sand with low content of organic matter and filamentous algae on pebbles but not on other substrate types. The magnitude of the effects varied between months. The results suggest that (i) even in dynamic coastal systems the biodeposits and excretions of mussels are at least partly assimilated locally and are not flushed away to the open sea, (ii) the accumulation of faecal material induced elevated growth of deposit feeders, (iii) mussels enhanced the growth of ephemeral macroalgae and reduced the growth of perennial macroalgae, and (iv) together with increasing benthic primary production, mussels indirectly increase the production of herbivores. [ABSTRACT FROM AUTHOR]

Combining field experiments with the biomass distribution data of dominant suspension feeders we compared the benthic and pelagic suspension feeding rates in shallow non-tidal brackish water coastal habitats. We found that pelagic grazing exceeded benthic grazing in almost all cases, on average from 14 to 4819 times depending on the site. Benthic grazing rates were related to site-specific environmental parameters and showed no relationship with water chlorophyl a (Chl a) content, whereas pelagic grazing rates varied both spatially and temporally and were related to water Chl a content. Our results indicate that in several shallow coastal habitats, pelagic suspension feeding substantially exceeds benthic suspension feeding. This suggests that pelagic recycling is higher than the amounts of energy redirected from pelagic to benthic food webs by benthic suspension feeders. These results increase our knowledge of the energy flows in coastal ecosystems. [ABSTRACT FROM AUTHOR]

The day–night cycle is one of the strongest geophysical cycles modulating species’ behavioral rhythms. However, in deep-water continental margins, where light intensity decreases over depth, interspecific competition may alter behavioral responses to day–night cycles. The burrowing decapod crustacean Nephrops norvegicus is a large-size predator in benthic communities, exerting despotic territorial behavior. In this study, we analysed how the effect of light intensity cycles on decapod behavioral rhythms is reduced as one moves from shelves to slopes. In the Western Mediterranean, the predatory behavior and interspecific competition for substrate use of Nephrops increases moving from the shelf (100–110 m) to the slope (400–430 m). Vector fitting and generalized additive models were used to assess the effect of light intensity and behavioral rhythms of N. norvegicus on the temporal variation of prey decapods co-occurring in trawl tow catches carried out on the shelf and the slope during October 1999 and June 2000. The combination of diel variations in light intensity and N. norvegicus abundance influences the activity rhythms of prey decapods in a depth- and seasonal-dependent manner. Light modulation is stronger on the shelf and weaker on the slope, where Nephrops population size is greater. Although present regression analysis does not necessarily imply a direct cause–effect relationship between rhythms of predators and prey, we suggest that Nephrops alters the temporal patterning in the behavior of its prey on the slope, where light intensity is reduced. This alteration is stronger in endobenthic species than in benthopelagic species; the former rely on bottom substrate for the expression of behavioral rhythms, experiencing stronger interspecific competitions with Nephrops at time of activity. [ABSTRACT FROM AUTHOR]

Growth dynamics and bioactivity variation of the Mediterranean demosponges Agelas oroides and Petrosia ficiformis were investigated over 15 months at Paraggi and Colombara within the Marine Reserve of Portofino Promontory (Mediterranean Sea, Ligurian Sea, Italy). For both species, growth rates varied between individuals and were unaffected by initial sponge size. The two species showed a different trend in growth pattern: A. oroides did not vary significantly between seasons, sites and depths; in contrast, some individuals of P. ficiformis showed a seasonal pattern, shrinking during winter as water temperature decreased and growing during summer when water temperature increased. Differences in growth between the two species may result from different reproductive cycles, food availability, species-specific thermophily and patterns of spatial competition. Moreover, spatial competition probably induced sponges to produce bioactive secondary molecules. Spatial and temporal variation of bioactivity of both species was examined for the first time by studying its effect on human neuroblastoma cells. The bioactivity of A. oroides extracts differed significantly between seasons, sites and depths, whereas the cytotoxicity of P. ficiformis differed significantly between seasons and depths (differences for sites were not determined). These results suggest the possible influence of environmental factors on bioactive metabolite biosynthesis. [ABSTRACT FROM AUTHOR]

The three main estuaries in the French Atlantic coast – the Seine, Loire and Gironde, all with high tidal regimes – are interfaces between the continental and the coastal ecosystems. The Seine and Gironde are highly contaminated, whereas the Loire remains in a more natural state. Both the Seine and Gironde have suffered from harbour construction, and as a result, their biological units are extremely compartmentalized. Benthic species and communities have adapted to tolerate temporal physical and chemical changes ( e.g. salinity, substrata, depth, and levels of fine particles and oxygen) and human activities ( e.g. dredging, shipping traffic, and habitat reduction). Although numerous bio-indicators and indices are used to define the ecological quality status (EcoQS) of coastal waters, very few of them were developed specifically for environments with a mosaic of conditions and salinity levels, including freshwater. The main problem appears to be that all the indices for determining anthropogenic stress examine the abundances of stress-tolerant species, which may also be able to tolerate natural stressors such as those occurring in estuaries. This paper takes a look at the development status of the benthic indicators and index approaches used in the three main estuaries along the French Atlantic coast. In addition, it examines the adaptation of the different benthic indicators to the taxonomic sufficiency principle, and the adaptation of the Benthic Opportunistic Polychaetes Amphipods index (BOPA) and the Benthic Opportunistic Annelida Amphipod index (BO2A) for use in the freshwater zones of transitional waters ( i.e. up to the upper limit of the tidal range). Several perspectives are discussed in light of the diverse disturbances and the heterogeneity of such stressed zones, such as the use of multimetric and scoring approaches. [ABSTRACT FROM AUTHOR]

Five exposed microtidal sandy beaches of North-eastern Buenos Aires (Argentina) were analysed to evaluate the influence of coastal dynamics on the abundance of the intertidal clams Donax hanleyanus and Mesodesma mactroides over a 1-year period. The physical characterisation of each beach was performed using 15 environmental variables and six morphodynamic indices. The population densities of both clam species were estimated by the number of individuals per strip-transect. Analysis of similarities revealed a significant multivariate environmental difference among beaches, which could be aggregated into a northern and a southern group. The former group was characterised by an intermediate morphodynamic state and by having, in general, high density values for both clam species. The latter was composed of beaches with an intermediate reflective state and showed, in general, low density values. Beach Index and Area showed the lowest temporal variation. Total density values, as well as density values of recruits and adults of D. hanleyanus and M. mactroides did not follow a north–south latitudinal gradient. Spatial and temporal fluctuations of density values were best explained by changes in individual physical variables rather than by changes in composite indices. [ABSTRACT FROM AUTHOR]

In this paper we looked for the most suitable method for benthic ecological quality status (EcoQS) assessment of the North-western Adriatic Sea. Taking into account the historical and present information, we inter-compared our expectations in terms of EcoQS, with the Bentix, AMBI and M-AMBI classification metrics results, and investigated the sensitivity of these indices to the spatial, seasonal and inter-annual variability of benthic communities. The sampling sites were located at increasing distances with respect to the Po River mouth, along an (inverse) gradient of eutrophication. Moreover, a 2-year monthly monitoring plan (October 2004–September 2006) was carried out at the CEBEB site, located in a central position with respect to the investigated area. The results highlighted that the three indices differed in the sensitivity to spatial and temporal variability of the benthic communities. The strong seasonal and inter-annual changes in the benthic communities had a significant effect on the Bentix, whereas no relevant modifications were observed on the EcoQS assignation obtained using the M-AMBI and AMBI methods. The environmental quality ratios (EQR) values and EcoQS classification obtained by the Bentix and AMBI did not match expectations, as they were not inversely correlated with the site distances with respect to the Po mouth, whereas the M-AMBI clearly discriminated the most and the least eutrophicated sites. It thus appears that the M-AMBI could be considered to be the most valuable method for the ecological-status assessment of the North-western Adriatic Sea benthic ecosystem. [ABSTRACT FROM AUTHOR]

The European Water Framework Directive (WFD, 2000/60/EC) recommends the development of biotic indices for assessing the ecological quality status of water bodies. The Benthic Index based on Taxonomic Sufficiency (BITS) was specifically developed for lagoonal systems, according to the tolerant/opportunistic approach. Macrobenthic data, variables indicative of eutrophication and variables indicative of sedimentary organic matter quality were collected during 18 surveys carried out between 2004 and 2005 in three Adriatic coastal lagoons (Venice Lagoon, Sacca di Goro, Lesina Lagoon). The relationship between environmental variables and biotic indices (AMBI, BENTIX, BITS, BOPA and FINE) was tested using multivariate analyses. Indices based on species classification level appeared to relate better with the variables describing organic matter quality, whereas BITS, which is based on family classification level, seemed related to eutrophication indicative variables, such as sulphide, ammonium, dissolved oxygen and orthophosphate concentrations. The BITS approach reduces the costs associated with sorting and identification of organisms. Providing a rapid assessment of ecological quality, and producing an ecologically relevant classification, BITS seems a promising tool for monitoring programs of Adriatic lagoonal ecosystems. Its sensitivity in reflecting the field conditions elsewhere, however, remains to be assessed. [ABSTRACT FROM AUTHOR]

The regulation and expression of biological rhythms with respect to sex and ontogeny in deep-water benthic decapod crustaceans constitutes an exciting field in marine biology that is far from understood. Liocarcinus depurator, Munida intermedia and Munida tenuimana are ecologically key crustacean decapod species of the Atlantic and Mediterranean shelves and slopes, and their activity rhythms in the field are poorly known. Our aim was to measure the behavioural rhythms of these species, while at the same time defining their type of displacement ( i.e. endobenthic, nektobenthic or benthopelagic). Whether gender and ontogeny modulate the rhythmic behaviour of these decapods is unknown, and we sought to clarify this issue. A temporally scheduled series of trawl hauls and light intensity measures was performed on the western Mediterranean shelf (100–110 m depth) and slope (400–430 m), close to the autumn equinox and the summer solstice. The sex and the size of animals in the catches were analysed. Catch patterns were evaluated through waveform and periodogram analyses. Liocarcinus depurator was captured at night on the shelf, whereas on the slope, animals displayed peaks both in the middle of the day and night. Size-related differences (but no gender differences) were found in its rhythmic behaviour, possibly due to intra-specific competition ( e.g. fighting) between juveniles and adults. Munida intermedia were weakly diurnal in October and both diurnal and nocturnal in June. Munida tenuimana presented no discernible rhythmicity in October, but was nocturnal in June. Both species showed no evident sex or size modulation of their behaviour. Data were interpreted assuming that all tested species present an endobenthic behaviour ( i.e. animals emerge from the substrate during the active phase of their behavioural cycle). [ABSTRACT FROM AUTHOR]

The effects of the freshwater discharge of the Oued Sebou River on the macroinfauna, was studied on the sandy beach of Mehdia through the analysis of the abiotic parameters and of the macrozoobenthos. In autumn 2002 and spring 2003, three beach sites, each with two transects, localized at 50, 3500 and 5720 m from the river mouth respectively, were studied. Positive correlations were recorded for beach slope and pH whereas negative ones were obtained for organic matter content and salinity at increasing distances from the river mouth. Significant differences between beach sites and seasons occurred for median grain size, organic matter content and pH. For each beach site, mean macroinfauna abundance varied between 30 and 100 ind.·m−2 and in spring there was a significant correlation between this parameter and the increasing distance from the river mouth. No significant correlation was instead found between species richness and the increasing distance, although the farthest beach site from the mouth had the highest number of species during both seasons. The results indicated the importance of organic matter content and salinity for the macrofaunal abundance whereas the diversity indices were more affected by beach slope and grain size. The results showed that there was no clear spatial trend in compound indices of the macrofauna across the sampled sites and the influence of the river discharge of Sebou River did not seem to be significant and consistent on the macrobenthos of this mesotidal shore. Comparison with microtidal shores revealed the influence of the tidal excursion and swell characteristics on the response of the benthic structures of sandy beaches to discharges of freshwater. [ABSTRACT FROM AUTHOR]

This paper reviews the available knowledge on sedimentology, hydrodynamics and five major ecosystem components (microphytobenthos, vascular plants, terrestrial arthropods, zoobenthos, and avifauna) of Belgian sandy beaches. It covers the area from the foredunes to the lower foreshore, takes an ecosystem approach to beaches of this specific geographic area. Morphodynamically, Belgian beaches are (ultra-)dissipative, macrotidal, and wide. Characteristic grain sizes are 160–380 μm. The sand becomes coarser, beach slopes steeper and tidal range smaller towards the south-west, where beaches have also been frequently reshaped by human interference such as nourishment. Beach organisms are highly adapted to this unique environment and can reach high numbers. We show that even on a heavily populated coastline subjected to intense recreational and development pressure, beaches provide critical, yet threatened, habitats. Vascular plants growing near the drift line, on the dry beach and in the embryonic dunes are mostly short-lived and thalassochorous; the most common species include sea rocket ( Cakile maritima), prickly saltwort ( Salsola kali subsp. kali), and sea sandwort ( Honckenya peploides). These zones are habitat to a highly diverse suite of terrestrial arthropods of halobiontic, halophilous and haloxene species; prominent members are sandhoppers ( Talitrus saltator) and dipterans (flies). Microphytobenthos, mainly diatoms, is an important primary producer on Belgian beaches but is not well known. The meio- and macrobenthos of Belgian beaches contains specific assemblages such as the Scolelepis squamata–Eurydice pulchra community of the upper intertidal zone. Birds no longer nest on the beaches itself, but Belgian sandy shores continue to function as important resting and foraging areas for birds such as the sanderling Calidris alba. We identify several human pressures on the beach ecosystems arising from recreation, beach management and fisheries. [ABSTRACT FROM AUTHOR]

Several studies have described patterns of distribution and species composition of sessile assemblages from marine caves but few have examined the processes of recruitment and larval settlement in the earlier stages of substrate colonisation. The present study evaluated (i) the distinctness of newly recruited assemblages on the local spatial scale, (ii) how this assemblage distinctness changes over time and (iii) how the recruitment patterns are affected by a different start-time in different positions in the cave. Two sets of 90 baked-clay panels (15 × 15 × 1 cm) were deployed in March (E1) and October 2002 (E2) at three positions in the shallow submarine cave ‘Grotta di Ciolo’ (South-East Italy, Central Mediterranean Sea): entrance (P1) and at 20 m (P2) and 80 m (P3) from the entrance, respectively. Each position was represented by two areas (1.5 × 1.5 m), and three panels from each area were randomly removed after 1, 3, 6, 12 and 24 months. The assemblages of the settled organisms comprised a total of 63 taxa. Different succession patterns were highlighted among assemblages across positions. A recruitment period of 2 years allowed a complete colonisation of panels at P1, where both encrusting algae dominated rocky walls and panels. In contrast, recruitment was very slow at P2 and P3, where the mature benthic community was not replicated on the 2-year panels. Finally, there was a partial convergence towards a common ecological succession in series started at different times. [ABSTRACT FROM AUTHOR]

The effects of marine fishing activities on benthic habitat and communities have become an important environmental issue. In addition to the direct removal of target species, effects include by-catch, damage to benthic organisms and alteration of habitat structure. The growing number of studies on the impact of fishing on bottom habitats indicates that the effects vary with the physical nature of the seabed and with the local natural disturbance regime. Several studies have been conducted on fisheries by-catch and discards off the south coast of Portugal since 1996. The results provide an idea of the impact on biodiversity: more than 60% of the species caught by the trawl fishery are discarded. The crustacean trawl captures the greatest number of species, probably due to the greater fishing depth range. In April 2004, the manned submersible ‘Delta’ (from DELTA Oceanographics, USA) conducted a sea campaign integrated in the SEMAPP programme (Science, Education, and Marine Archaeology Program in Portugal) to directly observe and assess the biological, geological, and archaeological aspects. A total of 15 dives were conducted mainly near the head and in the flanks inside Portimão canyon, down to 300 m. Observations showed variations in bottom type, the sedimentary framework and biological communities. These dives (150–300 m depth) also revealed a heavily trawled canyon bottom and erosion structures leading to changes in habitat structure and biodiversity. Of special interest was the occurrence of low-relief boulder substrates with relatively high densities of demersal finfish and shellfish. These sites served as a refuge for several species, whose abundance here was greater than on the surrounding areas of fine-grained substrates. Strong marks on the bottom are apparently caused by the doors of the trawl nets. Their impact will be examined in greater detail in future studies. [ABSTRACT FROM AUTHOR]

Burrowing and feeding benthic invertebrates generate various biogenic sediment structures. Such bioengineering is associated with a re-location of nutrients and, in most cases, with a disruption of the benthic community. We investigated the effects of different morphotypes of small-scale biogenic structures on the distribution and activity of bacteria in Arctic deep-sea sediments. Bacteria showed highly variable abundances, cellular biomasses and activities (estimated by thymidine and leucine incorporation) as a result of interacting driving forces: (i) Laterally transported organic particles accumulate at small-scale sediment elevations and depressions. (ii) Organic material is left behind crawling organisms as mucus or faeces. (iii) A significant proportion of bacteria is removed by predation or sediment relocation. In this context, the uppermost sediment layer beneath burrows and plough traces contained less bacteria of higher cellular biomass. Any nonconformity with biomass synthesis from organic compounds probably indicates a community shift because of sediment disturbance. Macrofaunal crawling and feeding tracks were shown to favour bacteria, both in abundance and cellular biomass. A high spatial patchiness along the track courses is suggested to depend on the availability of macrobenthic, metabolic products, as confirmed by faecal castings stimulating bacterial activity. This variable and highly complex scenario of microspatial bacterial community dynamics points to the potential of benthic fauna to cause habitat heterogeneity and to create micro-scale ‘hot spots’ at the deep seafloor. [ABSTRACT FROM AUTHOR]

Polychaetes are a key group in marine benthic communities worldwide because they are ubiquitous and generally abundant and diversified at all depths. Their anatomical complexity, however, makes it very difficult and time consuming to identify them correctly to species level, increasing the costs of any study involving them. Thus, the use of higher taxonomic levels in this group is a useful tool in monitoring or pollution-related studies. In this study, we compared the results obtained at both the species and family levels to assess the faunal changes associated to the different environmental conditions in the southern Gulf of Mexico, a large region known for its ecological and economic importance. We collected and identified 5686 polychaetes from 44 families, 95 genera and 206 species at 68 stations. Their relative density varied from 0% to 29.3% (ind. l−1) being higher in the Campeche Bank. The family richness (1–17) and specific richness (1–46) were both higher in the Campeche Bank. The same pattern was found for diversity and evenness at both taxonomic levels analyzed. The absolute diversity values were different using different taxonomic levels, but increased or decreased similarly at both levels. With the non-metric multidimensional scaling analysis, two main groups of stations emerged: Campeche Bank and Campeche Sound, with two less defined groups indicating a transitional sedimentary zone between them. All the groups were consistent both at family and species level, indicating little loss of information when the family level is used instead of the species level. We conclude that, if good previous basic knowledge of that fauna exists, the family level can be used to monitor environmental and pollution effects in these types of bottoms. [ABSTRACT FROM AUTHOR]

Coastal lagoons can be characterised by strong environmental changes along the outer marine-inner brackish gradient, which are reflected in the patterns of distribution of organisms and composition of assemblages. Close to the sea the assemblages are dominated by marine animals, while in the innermost confined areas, there would be estuarine taxa and organisms typical of organically-enriched areas. During the last decades, human impact has been severe in these habitats and has often profoundly altered the distribution of animals and plants along the gradient. In this study we have analysed the distribution of macrofauna along the outer marine-inner brackish gradient in five Italian lagoons, affected by severe human disturbance on the Adriatic, Tyrrhenian and Sardinian coasts. We aimed to measure changes in the composition of assemblages according to the distance from the sea, consistent among lagoons and time, after the occurrence of eutrophication, repeated distrophic crisis and other human interventions. We considered existing data from campaigns done during 1994, 1995 and 1999. We arranged different datasets according to the available data, in order to measure the spatial distribution of macrofauna genera with distance from the sea and through time. Analyses showed differences among assemblages related to the gradient. Nevertheless, the species characterizing the assemblages were all typical of organically-enriched areas, which testified to an impoverishment of diversity and functioning of all these systems. [ABSTRACT FROM AUTHOR]

The major problem in coastal areas of developing countries is disturbance caused by anthropogenic influence. This disturbance can be quantified by analysing the distribution and composition of marine communities using uni- and multivariate techniques and the biotic index. A study of benthic macrofauna was carried out along the São Sebastião Channel, northern coast of São Paulo State, Brazil, in an area with a submarine outfall, a petroleum terminal and a commercial harbour. Sampling was undertaken seasonally, by means of a van Veen grab (0.1 m2) at 15 oceanographic stations, from November 1993 to August 1994. A total of 392 species were identified (129 Polychaeta, 127 Mollusca, 98 Crustacea, 28 Echinodermata and 10 other phyla). The sedimentary pattern recorded for the São Sebastião Channel is very heterogeneous, influenced mainly by strong wind-driven currents, and differs from nearby shelf areas. The study area could be divided into three regions based on sediment texture and fauna: one region dominated by medium and coarse sand with low values of organic carbon; a second area where pelitic fractions were dominant with high values of organic carbon and nitrogen; and a third region characterised by fine and very fine sand, presenting intermediate organic carbon values. No temporal significant variation in abundance and species composition was found, except in autumn. The use of the‘marine Biotic Coefficient’ showed the same ecological trend as the faunal abundance and demonstrated that the central continental region of the channel is affected by human activities. [ABSTRACT FROM AUTHOR]

The benthic recovery after dredging (area: 2625 m²) was studied in a polluted and enclosed area of the harbour of Ceuta, in which the recolonization through the water column (larvae and adult bedload transport) could be limited by the lack of renewal. The benthos was sampled at two sites (control and dredged) using a van Veen grab and adopting a BACI (Before, After, Control, Impacted) approach. Five samplings were conducted after dredging (3, 15, 30, 90, 180 days). The proportion of gravel in the sediment of the dredged site increased after dredging, while the organic matter decreased. The impact on the community was estimated at species level, using both univariate and multivariate analyses. The maximum negative effect on benthic macrofauna was a reduction by 65% for species richness (15 days after dredging) and by 75% for abundance (3 days after dredging). Between 15 and 30 days after dredging, the abundance of some species such as the molluscs Parvicardium exiguum and Retusa obtusa and the polychaete Pseudomalacoceros tridentata increased considerably in the dredged site, while typical 'opportunistic' species such as Capitella capitata were disfavoured by the disturbance. For this small-scale dredging, about 6 months are required for the disturbed area to reestablish a sediment structure and a macrobenthic community similar to the undisturbed area. Small-patch dredging operations are proposed in harbour management whenever possible, since they allow a quick re-adjustment of the initial sediment structure and benthic communities. Keywords: Dredging; recolonization; macrofauna; Pseudomalacoceros tridentata; Capitella capitata; North Africa; Gibraltar area. [ABSTRACT FROM AUTHOR]