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Chondrochelia dubia is regarded as a cosmopolitan tanaidacean with tubicolous lifestyle that is commonly found in shallow waters. The lack of a dispersive larval stage, however, suggests that several endemic cryptic species might exist. Here, we studied C. dubia specimens collected from across 5000 km of distribution in the western Atlantic. We confirm its species complex status and identify five independent species, including C. brasiliensiscomb. nov. Using molecular analyses, we show that the genetic diversity and structure of C. dubia and C. brasiliensis strongly differ from one another, suggesting independent evolution of each lineage with a geographic separation at the Paraguaçu River mouth. The paleodistribution simulation suggests a considerable spatio-temporal expansion for C. dubia and C. brasiliensis since the Last Glacial Maximum (LGM), when the species was restricted to the submerged continental shelf. In summary, we observe that the simplified morphology of the Chondrochelia dubia complex hides a great diversity of species within the western Atlantic, approximately one per ecoregion. Combination of detailed morphological analyses with molecular and ecological data shall further elucidate the systematics of the Chondrochelia dubia complex worldwide. [ABSTRACT FROM AUTHOR]

Hard bottoms can negatively affect the surrounding infauna by hosting predatory fauna and modifying local hydrodynamics and sedimentation rates. Considering that these effects depend on the distance to the hard bottoms, we expected that the infaunal structure and recolonization would change accordingly. We assessed whether the distance from a rocky shore alters infaunal recolonization in a subtropical tidal flat. Sediment was defaunated on sites near and far from a rocky shore and the subsequent faunal recolonization was followed for 40 days. The sites near and far from the rocky shore displayed different assemblage structures, which we attributed to local variation in hydrodynamic conditions. Both the total infaunal abundance and the abundance of the dominant species recovered faster at the near site. We indicate that changes in infaunal recolonization at varying distances from natural rocky shores are primarily driven by the availability of adults. Infaunal recovery took less than 2 weeks, but recolonization rates increased near the rocky shore, as a function of its naturally variable assemblage structure and relatively lower species richness and abundances. We suggest that models of infaunal distribution and recolonization should incorporate landscape features such as the presence and distance from rocky bottoms. [ABSTRACT FROM AUTHOR]

The life histories of species influence the connectivity between populations, for example the dispersal potential, fecundity, and population size. We compare the phylogeography and genetic connectivity of two sandy-beach crustaceans with contrasting dispersal potentials and population traits in Brazil, based on the 16S mitochondrial gene. While the ghost crab Ocypode quadrata possesses high fecundity, long-lived planktonic larvae, and lower population densities of adults, the isopod Excirolana braziliensis is a brooder with low fecundity and higher population densities. Phylogenetic analysis of haplotype networks yielded contrasting results for the two species. Four different lineages were observed for E. braziliensis, while O. quadrata showed a low genetic structure, sharing haplotypes over ~ 7,000 km. For the isopod, the two most frequent lineages (‘North A’ and ‘South A’ lineages) showed distribution range limits that agreed with the tropical-subtropical transition of 22°S, while the others were sympatric, less frequent, and uncommon. While the ‘North A’ showed high haplotype diversity with a high structure, the ‘South A’ showed shared haplotypes and low genetic structure. Our results suggest that the contrasting life histories affect the population connectivity and genetic structure. The genetic patterns of the two species should be considered in the management and conservation of sandy-beach ecosystems. [ABSTRACT FROM AUTHOR]

This study aims to qualify, quantify, and compare the sediment reworking rates induced by the meso- (0.25-1 mm) and macro-infauna (>1 mm) along a mangrove growth gradient in the sedimentary dynamics of the French Guiana coast. The characterization of the role of small-infauna bioturbation in mangroves is new despite their known numerical dominance in tropical environments. Bare sediment, pioneer mangroves, and young mangroves were investigated during the dry season and spring tide to characterize their environment, infaunal functional community structure and sediment reworking rates. The biodiffusion differed significantly between mangrove stages, co-varying mainly with density and functional richness. On the contrary, the non-local transport remained similar, despite the mangrove-age-specificity of infauna functional compositions, which responded to modifications in the nature and content of organic matter. The first mangrove infaunal functional sequence is described: organisms that first colonize deposited mud generate the maximum biodiffusive mixing and induce a total downward particle flux ( BDF) as high as in the young mangroves; in the pioneer mangroves, the infauna variables and BDF are stressed to minimum values. Our study sheds light on the functional contribution of the small infauna in a mangrove coastal area and quantifies its role in particle transport during mangrove development. [ABSTRACT FROM AUTHOR]

Predators affect prey and non-prey communities through consumptive effects (CE) and non-consumptive effects (NCE), with consequences for ecosystem functions. Aquatic sediments are entanglements of particles that house diverse communities of microbes and invertebrates involved in ecosystem functions. In this study, we used experimental sediment cores as microcosms to explore the effects of two predatory flatworm species: Polycelis tenuis and Planaria torva. Flatworms secrete mucus for locomotion. Their motility results in particle displacement, which in turn increases the local availability of labile compounds. In this study we asked: (1) How do predators affect biomass allocation in a comprehensive community? (2) What is the impact of these effects on ecosystem functions? Our results showed that flatworms increased the sediment reworking rate and affected the packaging of biomass in prey (e.g., oligochaetes) and non-prey (e.g., protozoa) organisms through both CE and NCE. Causal links between community structure and ecosystem functions suggested different pathways of predator control: Polycelis indirectly influenced P availability, which increased the biomass of bacteria and protozoa, whereas Planaria elicited a trophic cascade and had a wider ranging diet than Polycelis. Our results support the use of flatworms as models to link the functions of organisms with those of ecosystems. [ABSTRACT FROM AUTHOR]

The effects of droughts on benthic infaunal communities and three epifaunal species were determined in three semi-arid central Texas estuaries with different inflow dynamics and consequent salinity regimes: the Nueces, Lavaca-Colorado, and Guadalupe Estuaries. Periods (months or years) were considered to be in drought if mean salinities were in the upper quartile of historic salinities. This drought classification method was verified by comparing the Palmer Drought Severity Index of the catchments with the drought classifications within each estuary. Droughts have demonstrable effects on estuary water column condition, notably decreases in turbidity, nutrient concentrations, and chlorophyll concentrations. Droughts do not appear to be important drivers of infaunal communities in estuarine regions with normally high salinities (25-32) although they coincide with increased diversity and changes in community composition in estuarine regions that have lower salinities (10-19). Droughts cause decreases in Litopenaeus setiferus (white shrimp) and Callinectes sapidis (blue crab) abundances and spatial extents. This indicates that droughts, especially when combined with water diversions, may negatively affect primary and secondary productions in other semi-arid estuaries of the world. [ABSTRACT FROM AUTHOR]

Negative responses of infauna close to rocky substrates are well known to subtidal bottoms, but there are few studies addressing similar intertidal habitats. We tested the hypothesis that the proximity to rocky shores negatively affects the density and richness of intertidal infauna of tidal flats by assessing infaunal variation across the increasing distances from rocky shores in two tidal flats (Pasto and Limoeiro) of a subtropical estuary in southern Brazil. Total density decreased significantly with the proximity to rocks only in Pasto due to density variations in the two numerically dominant species, the bivalve Anomalocardia flexuosa and the polychaete Armandia hossfeldi. Richness decreased significantly with the proximity to the rocky shores only in Limoeiro. Multivariate analyses revealed significant differences in species and functional groups composition between assemblages near and far from the rocky shores. Assemblage variability patterns were mostly explained by sediment variables. Our hypothesis was partially refuted because negative effects on the infauna were spatially inconsistent, due to differences in species composition between tidal flats, and to distinct responses of individual taxa. Even with the absence of consistent response patterns, the proximity to the rocky shores emerged as a relevant structuring factor of the surrounding intertidal infauna. [ABSTRACT FROM AUTHOR]

The urgency to find efficient indices and indicators to prevent further deterioration of coastal areas is one of the hot topics in today's scientific publication. However, a detailed knowledge of community responses to anthropogenic impacts is essential to sustain those indices. The studies on the response of benthic community to sewage pollution on intertidal rocky shores are generally based on visual census and do not take into account the tidal levels. In order to fulfil this gap in this study: (i) the sampling was performed by destructive sampling, with all individuals identified to the species level; (ii) the sampling was done at all levels of the intertidal (sublittoral fringe, eulittoral, and littoral fringe). Sewage pollution changed the environmental variables and the abundance of macroinvertebrates, being Mytilus galloprovincialis, Melarhaphe neritoides, and Chthamalus montagui the species most responsible for the dissimilarities observed. Effects were different on the three intertidal zones: community structure changed in the sublittoral fringe; suspension-feeders abundances and species richness increased in the eulittoral; no differences were detected in the littoral fringe. Moreover, the results confirm that the presence of sewage discharges tended to benefit suspension feeders, and that the sensitive species were replaced by opportunistic ones. [ABSTRACT FROM AUTHOR]

The aim of this study was to compare the impact of different freshwater inflow volumes on benthic communities and water column dynamics in different estuary classes. Benthic and water column spatial dynamics were contrasted in lagoons (with no direct inflow sources), tidal rivers that empty directly into the Gulf of Mexico, and bar-built bay systems (with direct inflow sources) along the Texas (USA) coast to determine the role of inflow in regulating ecosystem structure and function. Chlorophyll- a and nutrient concentrations were inversely correlated with salinity and were thus highest in the river systems, but lowest in lagoons. All Texas estuary types studied have conservative mixing for silicate and ammonium but are sinks for nitrite plus nitrate and phosphate. Macrobenthic production (abundance and biomass) was lowest in rivers and highest in lagoons. Diversity was low in estuaries with salinities between 1 and 17, but increased with salinities of up to 30, before decreasing in hypersaline conditions. Macrofaunal community structure divided the estuaries into two groups. The first group represented polyhaline communities and contained lagoons (East Matagorda, Matagorda, Christmas, and South Bays). The second group represented oligo-mesohaline community characteristics and contained the secondary bays (Lavaca Bay and Cedar Lakes) and rivers (San Bernard River, Brazos River, and the Rio Grande). The implications of these results for managing freshwater flows is that altered hydrology can change the character of estuarine systems regardless of their classification as bays, lagoons, or tidal rivers. [ABSTRACT FROM AUTHOR]

This article describes the relationship between 10 selected properties of the sediments (chlorophyll a and b, colloidal and total carbohydrate, water concentration, sediment type, organic matter, erosion threshold and erosion rate) and meio- and macrofauna within and among three different habitats in an urbanized intertidal mudflat/mangrove forest in Tambourine Bay, Sydney Harbour, Australia. Many of the biogeochemical variables were significantly different among habitats, often grading from mudflat to mangrove canopy. In contrast to previous studies, patterns of distribution of macrofauna among habitats were weak. For the meiofauna, only copepods showed any significant difference among habitats, with the greatest numbers in the open mudflat habitat and least under the mangrove canopy. There was a gradient in fauna among the habitats; overall macrofauna abundances were greatest under the mangrove canopy and least on the mudflat, while meiofauna abundance was greatest in the pneumatophore habitat and least under the canopy. Correlations between fauna and properties of sediment were generally weak. When the habitats were analysed separately, some correlations were strengthened but relationships were inconsistent. Thus, while some taxa vary significantly among habitats there was not a strong relationship between biogeochemical properties and either macro- or meiofauna. This suggests that localised factors other than the measured properties of the sediments are driving patterns in fauna at these small scales, which requires further investigation to be unravelled. [ABSTRACT FROM AUTHOR]

Coarse particulate organic matter is often broken down by specialist shredder invertebrates in temperate streams. In some tropical streams, larger, non-specialist, omnivorous fauna, (macroconsumers), particularly decapod shrimps and crabs, have been found to process coarse particulate matter. Larger shrimps and fish may also prey on or inhibit smaller invertebrates. Depending on the relative importance of larger and smaller fauna in leaf processing and in predatory interactions, we could expect that exclusion of larger fauna could either result in a decrease in leaf processing (if they were important in shredding or bioturbation) or increase in leaf processing if they negatively affected smaller shredders. We tested this by excluding fauna of different sizes from leaf peaks using bags with different sizes of mesh –0.2 mm (exclusion of most fauna), 2 mm (exclusion of larger fauna), and 10 mm (access to most fauna). Bag effect on leaf processing was minimized by constructing the bags of the same, fine, material, and sewing a relatively small window of the required mesh size. The experiment was conducted on two occasions in three streams of the urban forest of Parque Estadual da Pedra Branca, city of Rio de Janeiro. The three streams differed in larger fauna of shrimps ( Macrobrachium potiuna), crabs, tadpoles, and fish. Packs were incubated for six time intervals and the rate of leaf processing calculated as the exponential rate of loss of leaf material. Rate of leaf processing was faster in bags with the largest mesh size; the rates in the other two mesh sizes were not statistically different. Rates varied between experiments and among streams. We could not attribute the faster leaf processing to any particular component of the larger fauna; the patterns of differences among streams and between experiments were not associated with particular taxa. There was no general trend of fewer smaller fauna in the presence of macroconsumers; the few smaller taxa that were different between mesh sizes were variously less and more abundant in the 10-mm mesh bags compared to the 2-mm. Known shredders were rare in the smaller fauna; the mining chironomid Stenochironomus was common, but was apparently not affected by larger fauna and apparently did not increase leaf processing. We conclude that macroconsumers and not smaller fauna had a positive effect on leaf processing, and this confirms a pattern observed in some other coastal Neotropical streams. [ABSTRACT FROM AUTHOR]

Diurnal changes in the biochemical properties and the benthic macrofaunal assemblage of sediments in urbanised mangrove forests and their adjacent mudflats in Sydney Harbour were investigated. Behavioural and physiological changes in the microphytobenthos between day and night were predicted to cause diurnal changes in the micro-scale depth distribution of chlorophylls a and b and colloidal carbohydrate. In addition, because macrofauna can alter sediment properties, diurnal changes in the macrofaunal assemblages were investigated. The microphytobenthos at the study sites were predominantly filamentous green algae, although diatoms were present. Samples for biochemical analysis were collected from the top 2 mm of sediment using mini-cryolanders, during low tide in the day and at night. Three biochemical properties of the sediments were measured spectrophotometrically: chlorophylls a and b (surrogate for microphytobenthos biomass) and colloidal carbohydrate. The amount of chlorophylls tended to be less at night than during the day, but site to site variability was large and these differences were generally small and not significant. Depth profiles indicated that there was some redistribution of pigments in the surface 2 mm between day and night, possibly due to migration of microphytobenthos or physiological changes. There was no significant difference in chlorophylls between the mangrove forest and adjacent mudflat, with the exception of chlorophyll b at one sampling time, which was larger in the mangrove forest than on the mudflat. Colloidal carbohydrate was significantly larger in the mangrove forest and significantly less on the mudflat during the day at one site at one time, but otherwise showed no significant differences between day and night or between the mangrove forest and mudflat. Whilst there were some differences in the benthic macrofaunal assemblages between day and night, these differences were only significant for spionids and polychaetes at one time. There were, however, significant differences in assemblages of benthic macrofauna between the mangrove forest and mudflat, probably due to structural differences between these habitats such as the presence of pneumatophores, shade and leaf litter. In summary, there was some minor diurnal variation in the measured biochemical properties of the sediment, but not in the macrofaunal assemblage. Diurnal changes should, therefore, be considered when investigating biochemical properties in these habitats, but they are not a major influence. These findings contrast to previous studies on diatom dominated mudflats in Europe, where stronger diurnal changes in biochemical properties were found. Diurnal changes in the macrofauna assemblages were largely insignificant and therefore could not explain the changes in the biochemical properties. Diurnal effects on the macrofauna in these habitats are more likely to be via altered behaviours and this requires further investigation. [ABSTRACT FROM AUTHOR]

Mediterranean coastal areas are characterised by heavily transformed landscapes and an ever-increasing number of ponds are subjected to strong alterations. Although benthic diatoms and macroinvertebrates are widely used as indicators in freshwater ecosystems, little is still known about the diatom communities of lowland freshwater ponds in the Mediterranean region, and, furthermore, there are few macroinvertebrate-based methods to assess their ecological quality, especially in Italy. This article undertakes an analysis of benthic diatom and macroinvertebrate communities of permanent freshwater ponds, selected along a gradient of anthropogenic pressures, to identify community indicators (taxa and/or metrics) useful to evaluate the effect of human impacts. A series of 21 ponds were sampled along Tyrrhenian coast in central Italy. Five of these ponds, in a good conservations status and surrounded by woodland were selected as ‘reference sites’ for macroinvertebrates and epipelic diatoms. The remaining sixteen ponds were located in an agricultural landscape subject to different levels of human impact. The total number of macroinvertebrate taxa found in each pond was significantly higher in reference sites than in both the intermediate and heavily degraded ones, whereas the diatom species richness did not result in a good community variable to evaluate the pond ecological quality. The analysis revealed a substantial difference among the compositions of diatom communities between reference ponds and degraded ponds. The former were characterised by the presence of several species belonging to genera, such as Pinnularia sp., Eunotia sp., Stauroneis sp., Neidium sp., all of which were mostly absent from degraded ponds. Furthermore, the taxonomic richnesses of some macroinvetebrate groups (Odonata, Ephemeroptera, Trichoptera, Coleoptera), and taxa composition attributes of macroinvertebrate communities (total abundance, percentages of top three dominant taxa, percentages of Pleidae, Ancylidae, Hirudinea, Hydracarina) significantly correlated with variables linked with anthropogenic pressures. The results of the investigation suggested that diatoms tended more to reflect water chemistry through changes in community structure, whereas invertebrates responded to physical habitat changes primarily through changes in taxonomic richness. The methodologies developed for the analysis of freshwater benthic diatom and macroinvertebrate communities may have a considerable potential as a tool for assessing the ecological status of this type of water body, complying with the European Union Water Framework Directive 2000/60/EC. [ABSTRACT FROM AUTHOR]

The Black Sea as a whole is subject to considerable anthropogenic and natural pressures, and these can be intensified in enclosed Bays such as those around the city of Sevastopol. The overall biological status of Sevastopol Bay has improved considerably in the last 30 years or so. The number of macrobenthic species in the Bay has increased from just over 20 in 1973 to around 70 in 2000, and there have been similar enrichments in abundance, in biomass and in diversity ( H′). The same pattern is shown in other locations such as the Southern Bay (the most highly polluted of the embayments) from which macrofauna were completely absent in 1976 and 1982. Over the same period oil hydrocarbons in sediments of the Southern Bay have actually increased from 8760 mg kg−1 in 1976 to 12,020 mg kg−1 in 2002, while the levels in the open sea sediments have decreased slightly over the same period (450 mg kg−1 and 280 mg kg−1, respectively). Moreover, this pattern of biological improvement is also seen outside the Bay, suggesting a common factor in the changes. Since the effect of the local factors (i.e. pollution) can be readily seen in the gradient of biological response among sites, yet they have not significantly changed over the period of study, the overall improvement must involve some over-arching driver such as climatic influences. This point is discussed further in relation to the wider changes in the Black Sea system. [ABSTRACT FROM AUTHOR]

Temporal and spatial variation of the macrofaunal community was investigated in seagrass meadows in Akkeshi-ko estuary and coastal area of Akkeshi Bay, northern Japan. We specifically addressed the question of how the salinity gradient in seagrass meadows affects the species richness, abundance and similarity of faunal groups classified based on the degree of association with the seagrasses, i.e. highly motile species that drift in the water column among seagrass blades (drift-fauna, DF group) and less motile species that are tightly associated with seagrass substrates ( seagrass-associated fauna, SA group). A total of 70 species were collected semi-quantitatively using an epibenthic sledge, among which more than one third of the species were captured in all areas, and a quarter of species only in the marine area. Significant spatial variation in species richness, as well as a positive relationship between salinity and species richness was found for most sampling occasions and for both functional groups. Whereas, relationship between salinity and abundance of macrofauna was not clear although significant time and site interactions were found for both functional groups. Patterns of similarity of assemblages varied between the functional groups: clear differences by sampling sites were discerned for DF group but not for SA group. These results provided evidence that the macrofaunal community structures in seagrass beds varied with the salinity gradient, but the pattern differed with time and between functional groups, possibly due to the effect of biotic and abiotic factors that also changed with salinity. [ABSTRACT FROM AUTHOR]

Estuarine intertidal soft-bottom macrobenthic infauna of the Tagus estuary was characterised using different mesh size sieves and sediment sampling depth. The study sampled 105 sites using a hand held 0.01 m2 corer. The top layer (0–5 cm) was sieved through nested 1.0 and 0.5 mm meshes whereas the bottom layer (5–20 cm) was through a 1 mm mesh. The total survey took 26 taxa of more than 5800 individuals and a total wet weight biomass of over 650 g. The top layer, using both sieves, gathered 23 taxa (92% of the total), more than 5600 specimens (96%) but less than 8 g of biomass (1%) whereas the 1.0 mm sieve retained 21 taxa (91%), more than 1700 specimens (31%) and almost 7 g of biomass (1%). Abundance was dominated by small annelids, of which Streblospio shrubsolii was 68%, whereas biomass was dominated by molluscs, with the bivalve Scrobicularia plana representing 98%. Multivariate analyses showed an abundance pattern where the top layer data was very similar to that obtained with both layers. The bottom layer data were needed to accurately represent the total biomass pattern. The macrofaunal spatial pattern identified with the 0.5 mm sieve data differed from that identified by the 1.0 mm and was essential to discriminate a faunal assemblage located along the upper part of the shore. It was concluded that in order to characterize the macrofauna community structure, based on the presence/absence of taxa, the top layer and a 1.0 mm sieve would be sufficient. An abundance-based characterization requires the top layer and a 0.5 mm sieve whereas a biomass-based characterization requires data for both layers but it is sufficient to use the 1.0 mm sieve. [ABSTRACT FROM AUTHOR]

The different components of the benthic community of a sandy microtidal beach (Arenzano) in Liguria (NW Mediterranean) were investigated during late spring (May) 2002 and 2003. Sampling was carried out in two transects, chosen in order to represent the characteristics of the entire beach and their eventual spatial variations. Each transect included two stations: one placed in the swash zone (SW) and one in the surf zone (SF). Although no significant differences were found in the sediment texture over the 2 years ( t-tests p > 0.1 for all the granulometric fractions), notwithstanding an increase in the mean grain size (from 0.8 to 1.1 mm) between the sampling periods, 2002 was characterised by a higher quantity of organic matter (on average 14.4 vs. 3.6 gC m−2 for the sum of proteins, carbohydrates and lipids) and higher bacterial biomass (on average 1.9 vs. 0.9 gC m−2). The metazoan assemblages (meiofauna and macrofauna) were also richer (density = 2.9 × 105 vs. 1.0 × 105 ind. m−2, biomass = 0.09 vs. 0.03 gC m−2 for meiofauna; density = 1988 vs. 739 ind. m−2, biomass = 0.14 vs. 0.03 gC m−2 for macrofauna) in 2002. A significant quantitative reduction ( t-test for proteins, carbohydrates and lipids, at least p = 0.004) in the food supply in 2003 affected the abundance of the metazoans, as confirmed by a multivariate analysis that clearly differentiated the 2 years, and seemed to inhibit their relationships within the benthic food web. The bacterial biomass was always dominant, even under the least favourable trophic conditions, due to the ability of bacteria to adapt to a very harsh environment. Our results suggest that the food supply played an important role in the benthic community structures of the beach during late spring, bacteria being the key organisms within the benthic system. The communities seemed to be bottom-up controlled, while predation seemed to be irrelevant. [ABSTRACT FROM AUTHOR]

The intertidal benthic invertebrate community adjacent to “Parque das Nações”, Tagus estuary, western Portugal, was studied at seven sites between October of 1996 and 2002. Grain size analysis revealed that the area was essentially muddy with total organic matter ranging from 5.4 to 11.4%. Annelida represented more than 85% of the total abundance. The dominant taxa were Oligochaeta, Streblospio shrubsolii, Scrobicularia plana, Hediste diversicolor, Hydrobia ulvae and Cirratulidae. Analysis of abundance revealed high seasonal and interannual heterogeneity, although clear aggregations between winter/spring and summer/autumn sampling periods were detected by multivariate techniques. Paragnathia formica and Dolichopodidae were closely related to winter/spring cluster while S. shrubsolii, Cossura sp., S. plana and Corbula gibba were associated to the summer/autumn aggregation. Although other taxa were abundant in several seasons, constancy in their numbers throughout the year could be observed. Temperature, rainfall and daylight hours were the environmental variables best related to the biological data. Temperature and daylight hours were important for the establishment of the two seasonal aggregations. Rainfall has also shown to be an essential factor on the structuring of this intertidal community, closely related to the abundance increase of Cirratulidade and decrease of Polydora sp., Nephtys spp., Cerastoderma glaucum, Corophium spp. and other Gammaridea. Sediment composition seems to play an important role in changing the community characteristics during the year since some species abundance appear to be favoured by coarser particles and many by fine sediments. [ABSTRACT FROM AUTHOR]

We conducted a microcosm experiment to evaluate the capability of fauna inhabiting or being transported by drifting filamentous algae to colonize defaunated sediment. We expected meiofauna would perform a quicker and more effective re-colonization of disturbed areas by means of the algal mats than their macrofaunal counterparts. Similarly, within meiofauna, we expected more mobile taxa such as ostracods and harpacticoids to colonize the sediment more readily than other more sedentary ones such as nematodes. Naturally drifting algae were collected from the field and placed in 1 l aquaria on top of 5 cm of defaunated sediment. After 3 and 6 days, one core sample (5 cm deep) was taken from each aquarium; the first 2 cm were sliced into 2 mm layers, and the remaining fraction into 1 cm layers. The sediment remaining in the aquaria was sieved through a 0.5 mm sieve to collect the re-colonizing macrofauna. The dominant macrofaunal taxa inhabiting the algae were juvenile bivalves and gastropods, with Cerastoderma glaucum accounting for the majority of the bivalves and Hydrobia sp. for most of the gastropods. After 3 and 6 days, the most abundant macrofaunal taxa colonizing the sediment were Cerastoderma glaucum, Hydrobia sp. and gammarid amphipods. Higher abundances were found after 6 days than after 3, though differences were not significant for any of the major taxa. Meiofauna inhabiting the algae were dominated by rotifers, nematodes, ostracods, chironomid larvae and harpacticoid copepods. Contrary to our predictions, nematode and harpacticoid species inhabiting the drifting algae were not driven to sediment re-colonization but remained in the algae. Our results indicate that some benthic animals may indeed benefit from drifting algal mats as a means of dispersal and re-colonization of previously defaunated sediments in relatively short periods of time. Also, they may contribute to explain some of the trends found in other studies, regarding species increase under drifting algae and the recovery patterns found in areas often exposed to algal conglomerates. [ABSTRACT FROM AUTHOR]

Seasonal variations in invertebrate assemblages at two sites (upstream and downstream) on six central Florida headwater streams were compared by sampling at quarterly intervals with core and dip net samplers. Two of the streams were reclaimed following phosphate mining (∼6 yr prior to this study), two received runoff from mined lands, and two were disturbed by agriculture and/or residential developments. Physical and chemical characteristics of the reclaimed streams differed markedly from those of the non-reclaimed streams; principal differences between the streams were in current velocity, percent organic matter (POM), Mn, conductivity and alkalinity. Annual mean densities of meiofauna and smaller macrofauna for the 12 stream sites ranged from 20 896 to 175 212 m-2 and the mean for all sites was 56 492 m-2. The reclaimed streams and one of the streams influenced by agriculture had annual means of less than 40 000 m-2, 3- to 5-fold lower than the other streams. Fall and winter core densities were ∼2.4-fold greater than those for spring or summer when drought and low dissolved oxygen prevailed. Meiofauna comprised 68–91% of the core sample invertebrates in reclaimed streams but only 43–62% in the non-reclaimed streams; principal functional groups were: gathering collectors – 61.5%, predators – 19.3% and filtering collectors – 15%. The taxonomic composition of the reclaimed streams was predominated by crustaceans (60–71%) while chironomids and annelids were more abundant (71–92%) in the non-reclaimed streams. Dip net sampling added 21 larger macrofauna species (Odonata, Hemiptera and Coleoptera) to our list of taxa, producing a total of 209 species. Species richness and diversity (H′ and N2) indices were lower in the reclaimed streams, but evenness was more variable. The Czekanowski–Dice–Sørensen similarity index showed that the reclaimed stream sites were quite similar to each other, but differed markedly from the other stream types; there was large variation both within and between seasons. For central Florida headwater streams, drought appears to have a larger influence on invertebrates than the type of land use, however this relationship should be confirmed using streams of similar hydrology. [ABSTRACT FROM AUTHOR]

The composition and abundance of the meiofauna and macrofauna were studied in a survey carried out within 6 locations in a mangrove at the Island of Santa Catarina, South Brazil. Nine meiofaunal taxa were registered with densities ranging between 77 and 1589 inds.10 cm-2. The nematodes, composed by 94 putative species (86 genera), largely dominated the meiofauna. The most abundant genera were Haliplectus (Haliplectidae), Anoplostoma (Anoplostomatidae) and Terschillingia (Linhomoidae). Contrary to the meiofauna, the macrofauna showed a low number of taxa (only 17 recorded) and abundance (up 7250 inds.m-2). The macrofauna was mainly composed by deposit feeders, and numerically dominated by oligochaetes and capitellid polychaetes. For both components, differences in the composition and abundance along the sampling sites were significant but not primarily related to the typical variations along estuaries, such as salinity. The results of the stepwise multiple regression analyses showed that the detritus biomass (ash-free dry weight) was the most important predictor of faunal densities and diversity. The clear relationship between detritus and fauna, together with the contrasting community structure of the two component of the benthos suggest that the meiofauna showed a high efficiency in exploiting the micro-habitat created by the presence of the detritus. Yet the macrofauna, potentially the main consumer of the debris, is negatively affected by their low palatability and poor nutritive value. [ABSTRACT FROM AUTHOR]

The mobile component of a community inhabiting a submarine boulder scree/cliff was investigated at Lough Hyne, Ireland at dawn, midday, dusk and night over a 1-week period. Line transects (50 m) were placed in the infralittoral (6 m) and circumlittoral (18 m) zones and also the interface between these two zones (12 m). The dominant mobile fauna of this cliff consisted of echinoderms (6 species), crustaceans (10 species) and fish (23 species). A different component community was identified at each time/depth interval using Multi-Dimensional Scaling (MDS) even though both species diversity (Shannon–Wiener indices) and richness (number of species) remained constant. These changes in community composition provided indirect evidence for migration by these mobile organisms. However, little evidence was found for migration between different zones with the exception of the several wrasse species. These species were observed to spend the daytime foraging in the deeper zone, but returned to the upper zone at night presumably for protection from predators. For the majority of species, migration was considered to occur to cryptic habitats such as holes and crevices. The number of organisms declined during the night, although crustacean numbers peaked, while fish and echinoderms were most abundant during day, possibly due to predator-prey interactions. This submarine community is in a state of flux, whereby, community characteristics, including trophic and energetic relationships, varied over small temporal (daily) and spatial (m) scales. [ABSTRACT FROM AUTHOR]

Four hundred and thirty two suprabenthic hauls with a modified Macer-GIROQ sledge were taken over the period 1988-1996. Fifteen sites within the English Channel were sampled from the Roscoff and Plymouth waters to the Dover Strait, including the Bay of Morlaix, Bay of Saint Brieuc, the Bay of Seine and the Seine Estuary. The main characteristics of the Benthic Boundary Layer (BBL) macrofauna in the English Channel were elucidated from these data. BBL macrofauna was found over the whole water column sampled (10-150 m). Firstly, the number of species collected was very high (up to 116 species for five hauls) exceptin the Seine estuary. Numerically, mysids were the dominant group oforganisms collected with the sledge, followed by amphipods, cumaceans, isopods and decapods. Abundance and biomass of the fauna were veryhigh in the Seine estuary, especially in the mesohaline and oligohaline zones (maximum >216000 ind. 100 m-3; >200 g AFDW 100 m-3) where the specialised mysids Neomysis integer and Mesopodopsis slabberi occurred in very high abundance. At other sites, the abundance and biomass were moderate (100-10000 ind. 100 m-3; 15-2000 mg AFDW 100 m-3). Abundance reached its maximum when mysids or swarms of amphipods of the genus Apherusa were collected, and during the reproduction of the amphipods of the genus Ampelisca, as in June in the Bay of Morlaix. The number of species, abundance and biomass showed seasonal changes in all sites with, in general, lowest values in winter or spring, and highest values in autumn. For the open sea sites, two main geographical gradients were identified: i) in spring, a higher number of species in the western part of the Channel compared with the eastern part of the Channel and, in autumn, a higher number of species in the eastern part of the Channel compared with the western part, and ii) an increasing density gradient from west to east at spring and a decreasing gradient from west to eastdur [ABSTRACT FROM AUTHOR]

Epibenthic macrofauna communities (species composition and densitiesof the dominant species) were investigated at Taiaro Atoll, Tuamotu Archipelago, 22 years after a previous survey. This small atoll is completely closed, has no permanent functional hoa, and is not affectedby direct anthropogenic disturbances since it is a Biosphere Reserve. Ten species were identified in 1994 (5 molluscs, 4 corals, and 1 echinoderm). With the 14 species identified in 1972 (12 molluscs, 1 coral, and 1 echinoderm), a total of 17 species (12 molluscs, 4 corals, and 1 echinoderm) has been recorded for the lagoon. There has been a shift in dominance away from the bivalve Crassostrea cucullata (in 1972) to Pinctada maculata (in 1994). A high mortality of the epibenthic macrofauna affected the central part of the lagoon shortly before 1972 and reached the inner reef flat afterwards. The distance of Taiaro from sources of colonizers, its small size, and the isolation of its lagoonal waters posing a physical barrier to colonization by organisms and leading to harsh environmental conditions (e.g. very high salinities: 42.5-43 psu), are likely to be the major causes of the exceptionally low diversity observed. [ABSTRACT FROM AUTHOR]