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The shifts in soil metabolism as a response to warming and wrack subsidies on Antarctic sedimentary shores have not been studied to date. With this aim, macroalgal deposits, as well as inorganic nutrients and CO2 emission were quantified along the shores of Port Foster, on Deception Island, Antarctic Peninsula. The results indicated a positive relationship between the amount of wrack supplies and sediment metabolism, measured both as CO2 emission through the sediment surface and as amount of inorganic nutrients released to the interstitial pore water. The effect of warming on algal wrack decay was analyzed in a manipulative field experiment where passive open-top chambers (OTCs) were used to increase soil temperature. By doing this, temperature raised by 0.9°C under patches of the red macroalgae Palmaria decipiens, whereas there was an increase of 2.4°C on bare sand. The results indicated that a small warming accelerated mineralization rates of C, N and P of the algal biomass, without significant changes in the bulk of inorganic nutrients released. Over 12 days of experiment, 8.3% of the total C in algal tissues was released as CO2 in the OTC plots, compared to 6.4% at ambient temperature. CO2 emission in bare sand plots warmed with OTCs was three times the amount measured in the ambient plots. Collembola was the dominant soil fauna, with densities negatively affected by warming and positively related to the organic content of sediment. This study confirms the key role of sandy shores in recycling ocean derived organic matter, highlighting the sensitivity of Antarctic ecosystems to a changing scenario of climate change that predicts significant increases in temperature over the next few decades.

The increased frequency of heatwaves expected in the context of global warming will affect socio-ecological systems such as shellfish beds at intertidal seagrass meadows. A mesocosm experiment was performed to assess the effects of a simulated atmospheric heatwave during low tide on the bioturbation indicators and growth of the commercial juvenile native Ruditapes decussatus and the introduced clam R. philippinarum, and on their interactions with the seagrass Zostera noltei. Under the heatwave, heat dissipation at 5 cm depth was significantly greater in the sediments below Z. noltei than below bare sand, the photosynthetic efficiency (Fv/Fm) of Z. noltei decreased and the clams tended to grow less. Furthermore, after the heatwave clams below bare sand tended to burrow deeper than those below Z. noltei, indicating that seagrass provided a refuge for clams. Ruditapes philippinarum grew less, and did not burrow as deeply as R. decussatus, which may imply greater vulnerability to desiccation and heat at low tide. The particle displacement coefficient (PDC) of R. philippinarum indicated lower bioturbation values in Z. noltei than in bare sand and was a suitable bioturbation indicator for juvenile Ruditapes spp. clams. In Z. noltei coexisting with R. philippinarum, the Fv/Fm values were higher than without clams after a recovery period, which may be linked to the assimilation of phosphate excreted by the clams and suggests a facilitative interaction. No such interaction was observed with R. deccusatus, probably because of its deeper burrowing depth. The findings suggest reciprocal facilitative interactions between R. philippinarum and Z. noltei and the potential contribution of Z. noltei to the sustainability of clams under global warming scenarios, which may support management actions aimed at enhancing the coexistence between shellfishing activities and seagrass conservation. Agencia Estatal de Investigación | Ref. RTI2018-095583-B-I00 Xunta de Galicia | Ref. ED431C 2021/42 Xunta de Galicia | Ref. ED481A-2020/199 Universidade de Vigo/CISUG

Biodiversity loss is considered one of the main threats to marine ecosystems. In this framework of biodiversity decline, organisms that provide biogenic habitat play a relevant role by their capacity to structure assemblages and influence ecological processes. The Mediterranean mussel Mytilus galloprovincialis is considered an ecosystem engineer because it alters local environmental conditions maintaining habitat suitability for other organisms, and enhancing local biodiversity. Although it is widely recognized that mussel beds increase diversity, the drivers shaping these assemblages are poorly explored. We investigate whether mussel size homogenisation shapes the abundance, richness and structure of macrobenthic assemblages associated with mussel beds in two shores of the Galician coast (NW Spain). At each shore, two sites, 10 m apart, were selected and at each site, faunal assemblages were compared between mussel clumps showing shells of various sizes (control), and mussel clumps with closely similar-sized mussels, considered as homogenised. Homogenised clumps showed, in general, higher values in total number of individuals and species than control clumps. Regarding the effect of mussel size homogenisation on the multivariate structure of the assemblages, significant differences between control and homogenised clumps were found in three out of the four sites. Most relevant associated species usually reached higher abundances in homogenised clumps than control ones. Therefore, mussel size homogenisation influenced the structure of the macrofaunal assemblages associated with mussel beds but, its effect was context dependent (i.e., varied with sites). Information about the species contribution to dissimilarities among homogenised and control clumps was provided and the potential influence of sediment and algae on mussel clumps was discussed COMPETE 2020, FEDER | Ref. PTDC/CTA-AMB/30181/2017, n. 30181 Fundação para a Ciência e a Tecnologia | Ref. UIDB/ 04423/2020 Fundação para a Ciência e a Tecnologia | Ref. UIDP/04423/2020 Fundação para a Ciência e a Tecnologia | Ref. CEECIND/03893/ 2018

Marine aquaculture releases mollusc shell debris which can accumulate on the seabed. Due to its low degradability, mollusc shell debris becomes integrated into the sediment, modifying both its structure and associated biogeochemical processes. These changes are expected to influence the biological assemblages within the sediment, which play a key role in the biogeochemical processes due to bioturbation. We performed an in-situ experiment to test the effects of mollusc shell-hash on the bioturbation capacity of the macrofaunal assemblages within the sediments affected by marine aquaculture. The aquaculture facilities chosen were a fish farm in an oligotrophic area of the Mediterranean over a sandy sediment, and a mussel farm in the Atlantic located in an estuary over silty sediment. Mollusc shell-hash promoted macrofaunal assemblages with a high bioturbation potential, regardless of the influence of aquaculture. Nevertheless, in the sediment from the mussel-farm, the shell-hash did not have a marked effect on the macrofaunal assemblages. The effect of shell-hash on promoting macrofaunal communities with a high bioturbation potential capacity is therefore dependent on the existing environmental conditions in the area, including the natural organic matter input and grain size of the sediment. Shell-hash could be used a strategy to improve the ecosystem function of sediments as a circular economy-oriented management practice. This research was funded by the project CGL2015-70136-R from the Spanish National Agency for Research (MINECO/FEDER). CS was funded by the University of Alicante (Ref. UATALENTO 17-11).

Temporal variation patterns and bioturbatory activity of polychaete assemblages have been insufficiently studied. Two subtidal fine-sediment sites have been sampled in order to describe and compare polychaete temporal variation patterns. In order to estimate bioturbation potential (BP), a new approach is proposed that aims maximum versatility for comparative studies. Both assemblages differed significantly in terms of temporal variation of sedimentary and faunal attributes. The most exposed site was dominated by species characteristic of muddy-fine sand and presented a seasonal pattern with higher densities and BP values from mid-summer to early winter. The most sheltered and muddy site was dominated by Paradoneis lyra and presented an irregular temporal variation. Signs of moderate organic enrichment were found, particularly in the less exposed site. Spatial and temporal variations appear to be related to sediment features and hydrodynamic stress, which also affect BP of each assemblage. Our results suggest that the bioturbatory activity of polychaetes is more extensive and relevant in finer sediments.

Spatial variability of environmental factors and macrobenthos, using species and functional groups, was examined over the same scales (100s of cm to >100 km) in intertidal sediments of two transitional water systems. The objectives were to test if functional groups were a good species surrogate and explore the relationship between environmental variables and macrobenthos. Environmental variables, diversity and the multivariate assemblage structure showed the highest variability at the scale of 10s of km. However, abundance was more variable at 10s of m. Consistent patterns were achieved using species and functional groups therefore, these may be a good species surrogate. Total carbon, salinity and silt/clay were the strongest correlated with macrobenthic assemblages. Results are valuable for design and interpretation of future monitoring programs including detection of anthropogenic disturbances in transitional systems and propose improvements in environmental variable sampling to refine the assessment of their relationship with biological data across spatial scales.

Due to the economic importance of the mussel Mytilus galloprovincialis in the Spanish aquaculture, there is a growing interest in developing alternative methods to ensure the supply of good-quality biological material and to minimize the uncertainty and variability that might be a source of economic risk for this sector. The aim of this work was to develop a successful cryopreservation protocol for Mytilus galloprovincialis larvae and study long-term effects by assessing survival and development post cryobanking. We evaluated the effect of previously studied cryoprotecting agent, Ethylene glycol (EG) for cryopreservation of trochophore larvae and D-veliger larvae 48 h and 72 h old, following an existing preliminary protocol for M. galloprovincialis mussel trochophores. The protocol selected for cryopreservation consisted on holding at 4 °C for 2 min, then cooling at 1 °C/min to −12 °C, holding for 5 min, then cooling at −35 °C with a rate of 1 °C/min, then plunging into liquid nitrogen for storage. Thawing took place by immersion in 35 °C water bath. With this protocol the initial percentage of short-term developed a D-larvae (48 h incubation post-thaw) was 48.9 ± 7.6% with 10% EG + 0.2 M Trehalose (TRE). This initial test only studied the trochophore larvae until they reached the D-stage (48 h old); in the present experiment experiments, we replicated this study but also carried out a long-term larval rearing with cryopreserved trochophore larvae in comparison to fresh larvae. This experiment allowed a comparative post-freezing analysis of both larval development and survival. Larval settlement was also characterized after 13 days. The data revealed that until settling, the survival of the cryopreserved larvae was slightly lower than the 2.8% reported in the larval rearing for Greenshell™ mussel. Over time, there was an initial difference in size of cryopreserved larvae when compared to controls, but from day 17 onwards the size between both types of larvae began to stabilize. Attending to settlement, we obtained a 64% of success of cryopreserved larvae respect to the control.

DNA metabarcoding provides a rapid and effective identification tool of macroinvertebrate species. The accuracy of species-level assignment, and consequent taxonomic coverage, relies on comprehensive DNA barcode reference libraries, which, due to incompleteness, are currently a recognized limitation for metabarcoding applications. In this study, we assembled a comprehensive reference library of DNA barcodes for Atlantic Iberia marine macroinvertebrate species, assessed gaps in species coverage and examined data ambiguities. Initially, an Iberian species checklist for the three dominant groups of marine macroinvertebrates was compiled, comprising 2827 species (926 Annelida, 638 Crustacea and 1263 Mollusca). A total of 18162 DNA sequences of the cytochrome c oxidase subunit I barcode region (COI-5P) matching the species checklist were compiled in a BOLD dataset, where taxonomic discordances were evaluated and cases of deep intraspecific divergence flagged. Gap-analysis showed that 63% of the Iberian macroinvertebrate species still lack a DNA barcode. Coverage gaps varied considerably across taxonomic groups with Mollusca displaying the highest sequence representation in the dataset (427 species, 49% of the total number of sequences), and Crustacea the highest species coverage with 338 species barcoded (53% of the checklist). In contrast, Polychaeta displayed the lower levels of completion (288 species, 16% of the total number of sequences). In total, 1545 Barcode Index Numbers (BINs) were assigned to 1053 barcoded species, of which 66% were taxonomically concordant, 26% displayed multiple BINs and 8% were discordant. Overall, results show that there is still a large portion of marine invertebrate taxa in this region of Europe pending barcode coverage, even considering only the dominant groups. However, the most notable finding was the relevant proportion of species flagged for significant intraspecific divergence and possible hidden diversity. The annotated reference library and gap-analysis here provided can there, This study was supported by the project The NextSea [NORTE-01-0145-FEDER-000032], under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF). This work was supported by the "Contrato-Programa'' UIDB/04050/2020 funded by national funds through the FCT I.P. SD and PEV work was supported by national funds through the Portuguese Foundation for Science and Technology (FCT, I.P.) in the scope of the project NIS-DNA [PTDC/BIA-BMA/29754/2017]. BRL benefitted from an FCT fellowship PD/BD/127994/2016. MALT benefitted from an FCT fellowship co-financed by European Social Fund (ESF) SFRH/BD/131527/2017.

EASME/EMFF/2016/1.2.1.4/016 Negative impacts of marine invasions include loss of genetic diversity, ecosystem functions/processes, and/or community structure and, consequently, a threat to global biodiversity through biotic homogenization. Recent studies indicate that invasive macroalgae make up a significant proportion of marine invasive species. Marine Protected Areas (MPAs) have been proved to have positive effects on marine biodiversity conservation; however, their role in preventing biological invasions, especially macroalgae, is still poorly understood. In this context, we studied the effects of protection and wave exposure on the abundance of six invasive macroalgae (Grateloupia turuturu, Asparagopsis armata, Colpomenia peregrina, Sargassum muticum, Undaria pinnatifida, and Codium fragile ssp. fragile) at two MPAs of the western Iberian Peninsula, one located along the Spanish coast (Illas Atlánticas) and the other on the Portuguese coast (Berlangas). The results showed opposite effects of protection and wave-exposure at the two MPAs. Greater biomass of invasive macroalgae was found at semiexposed areas outside the reserve in the Spanish MPA, whereas in the Portuguese reserve, biomass (especially of A. armata) was significantly greater inside the reserve, mainly at semiexposed sites. These differences highlight the importance of understanding the functioning of reserves to apply proper conservation management policies in order to preserve the MPAs resilience. info:eu-repo/semantics/publishedVersion

Poor physiological acclimatization to climate change has led to shifts in the distributional ranges of various species and to biodiversity loss. However, evidence also suggests the relevance of non-climatic physical factors, such as light, and biotic factors, which may act in interactive or additive way. We used a mechanistic approach to evaluate the ecophysiological responses of four seaweed species (three dominant intertidal fucoids, Fucus serratus, Ascophyllum nodosum, Bifurcaria bifurcata, and the invasive Sargassum muticum) to different conditions of grazing, light irradiance and ultraviolet (UV) radiation. We performed a large-scale mesocosm experiment with a total of 800 individual thalli of macroalgae. The factorial experimental design included major algal traits, photoacclimation, nutrient stoichiometry and chemical defence as response variables. Few significant effects of the factors acting alone or in combination were observed, suggesting a good capacity for acclimatization in all four species. The significant effects were generally additive and there were no potentially deleterious synergistic effects between factors. Fucus serratus, a species currently undergoing a drastic contraction of its southern distribution limit in Europe, was the most strongly affected species, showing overall lower photosynthetic efficiency than the other species. The growth rate of F. serratus decreased when UV radiation was filtered out, but only in the presence of grazers. Moreover, more individuals of this species tended to reach maturity in the absence of grazers, and the nitrogen content of tissues decreased under full-spectrum light. Only the phlorotannin content of tissues of B. bifurcata and of exudates of A. nodosum, both slow-growing species, were positively affected by respectively removal of UVB radiation and the presence of grazers. The findings for S. muticum, a well-established invasive seaweed across European coasts, suggested similar physiological response of this fast-growing species to different levels of grazing activity and light quality/intensity. As expected, this species grew faster than the other species. Bifurcaria bifurcata and A. nodosum only showed minor effects of light quality and grazing on phlorotannins content, which suggests good resistance of these two long-lived species to the experimental conditions. Mechanistic approaches that are designed to analyse interactive effects of physical and biotic factors provide an understanding of physiological responses of species and help to improve the confidence of predictive distribution models.

The Ria de Vigo is a semi-enclosed bay with high primary productivity due to the influence of coastal upwelling-downwelling dynamics. The area is heavily populated and affected by numerous human activities, which lead to sediment modification. Epibenthic megafauna from the non-estuarine zones of this bay has been studied in order to describe its spatial distribution, testing possible differences between inner and outer areas. With that purpose, 75 sites have been sampled by means of a towing dredge. Megafauna was identified to the lowest taxonomic level possible, and each taxon counted and weighted. 113 different taxa were identified and a high spatial heterogeneity was observed in terms of abundance, biomass, taxa richness, diversity and evenness. Suspension-feeding molluscs dominated the innermost part of the studied area, and were substituted by echinoderms towards the external zones; this spatial pattern was also reflected in the results of multivariate analyses. These shifts in taxonomic and trophic guild composition of the assemblages have been tentatively related to differences in pollution levels and primary productivity along the main axis of the bay.

Antarctic benthos has been a main target in Antarctic research, but very few quantitative studies have been carried out in the littoral zone, which may be seasonally covered by macroalgae. In this work, we studied (1) cover and biomass of the macroalgae Iridaea cordata and Adenocystis utricularis, and (2) composition of macrobenthic assemblage associated with these macroalgal species at three locations at King George Island: Mareograph Beach (1 M), Tank’s Bay (2R) and Ardley Bay (3R). Iridaea cordata was collected by completely detaching the algae from the substrate, while A. utricularis was scraped. Adenocystis utricularis covered more than 80 % of the substrate at all locations, while coverage of Iridaea cordata was below 53 % or absent (3R). Fresh biomass of I. cordata was 0.8–61.4 g/individual and 4.7–93.0 g/100 cm2 for A. utricularis. The assemblage associated with both macroalgae differed significantly between sites. The studied fauna was composed mainly of amphipods, gastropods and bivalves. Species diversity was higher in the community associated with A. utricularis. A total of ~27 ind/g DW were found associated with I. cordata, while ~112 ind/g DW were found associated with A. utricularis. The most abundant groups associated with I. cordata were amphipods at 1 M (57 %) and gastropods at 2R (46 %). Both groups were responsible for the dissimilarity between localities (62.50 %). The most abundant groups associated with A. utricularis were the gastropods at all localities reaching up to 82 % at 1 M. This study provides a first baseline on the diversity and abundance of benthic assemblages associated with intertidal macroalgae in the southwest of King George Island.

Uromunna naherba sp. nov. is described from eelgrass beds (Zostera marina and Z. noltii) of the NW Iberian Peninsula. This is the second species of the genus reported from the NE Atlantic, after U. petiti. The new species was more abundant on rhizomes than on the leaves of the plants. Seasonal samples show that ovigerous females are present throughout the year, but become more abundant in late spring and summer, when adult males decrease in frequency. Ovigerous females appear in only one size class. Owing to the yearly productivity cycle of the eelgrasses, these data suggest that the species is semelparous and completes its lifecycle within 1 year. The taxonomic characters of the genus are discussed.

Subtidal sediments of Isla del Coco (Cocos Island), Costa Rica were described in their grain size, sorting, organic matter, and carbonates from 27 dredge samples (3–75 m), collected in April 2010. The organic matter range between 1.37–3.31% and carbonates presented a mean of 74±17%. The sorting was moderately or poorly. The grain size ranged between 0.1–1.1mm. The pattern is that sediment change from inner to mouth of bays. Carbonates and gravel fractions increased offshore and organic matter have high values inner the bays. Input of vegetal debris and mud was from the rivers of this island covered with rain and cloud forest.

The mollusc assemblages inhabiting two fine-sediment bottoms in the Ria de Aldan (NW Iberian Peninsula) were quantitatively sampled to test hypotheses about influence of sediment in faunal composition, seasonal variation and amensalist relationships. Both trophic guilds and life habits were considered for functional group classifications of the mollusc species found. The two assemblages were found to have differences in both numerically dominant species and general structure. Among numerically dominant species, Kurtiella bidentata was the only one present in numbers at both sites; it was second to Chamelea striatula at the site with the coarsest sediment and the top dominant at the one which had higher organic content, there followed by Thyasira flexuosa. There were significant changes in abundance, number of species and diversity indexes during the study period; maximum values of abundance occurred in autumn. Seasonal variations in univariate faunal parameters and functional groups were also correlated with those in sediment features and sediment heterogeneity was identified as a key factor to explain diversity of the assemblages. The extensive mussel raft culture in the area seemed not to affect negatively either abundance or diversity and might favour higher diversity by increasing the heterogeneity of the sediment through the supply of mussel shells. Hydrodynamic regime of the embayment is suggested to be a relevant factor in determining differences between the structures of assemblages. Seasonal changes in this regime would lead to major changes in the characteristics of the sediment and therefore in the mollusc assemblages. Higher intensity and frequency of these changes seem to promote a closer relationship between the assemblage and the sediment, as well as a tighter coupling between functional and taxonomic structure of the former. The existence of amensalist relationships was dismissed for both assemblages as no negative relationships between trophic guilds were found.

This paper describes the distribution and composition of the syllid fauna inhabiting seagrass meadows in the Ensenada de O Grove (NW Spain). Samples were collected on muddy sediments colonized by either Zostera marina L., Zostera noltei Hornemann or by a mixed meadow with both species. Syllids were dominant (13340 individuals; 37% of total polychaete abundance), including 22 species (12 genera). The mixed meadows housed the highest number of species and the Z. noltei meadow had practically no syllids. The dominant species were Exogone naidina, Parapionosyllis elegans, Parexogone hebes and Prosphaerosyllis campoyi ( > 80% of total abundance). Carnivores (mainly species of Parapionosyllis, Amblyosyllis , and Streptosyllis ) were dominant, especially in muddy sand with either Z. marina or Z. noltei and sandy mud with a mixed meadow. The most important abiotic variables for explaining the composition and distribution of the syllid fauna were bottom water salinity, sorting coefficient and carbonate content. The highest number of species was recorded at sites with a high salinity and carbonate content and the lowest at sites with a high sorting coefficient.

Marine algae are known to provide habitats for a wide range of marine organisms. Populations of marine epiphytal invertebrates are generalists and are less adapted to live in only one macroalga species. However, there are some examples of local adaptation and, in particular, amphipods have shown strong host specificity. Amphitholina cuniculus, an amphipod with an alga-burrowing habit, has been mainly observed in Bifurcaria bifurcata mats on the intertidal rocky shores of the southern region of the Galician coast (NW Spain; 42o11.27′ N, 8o48.25′ W). We designed a laboratory experiment conducted in June 2009 to analyse the association between the amphipod and the macroalga. In particular, we hypothesised that (i) this species would exhibit different behaviour during the day and at night, and (ii) adults of A. cuniculus would prefer B. bifurcata as habitat rather than Fucus vesiculosus or Sargassum muticum. Results supported the hypothesis that adults of A. cuniculus preferred B. bifurcata, although such preferences did not show the day/night variability predicted. This amphipod might be considered a specialist species, at least on rocky intertidal shores along the Galician coast.

Carrion consumption and scavenging are increasingly recognized for their role in community structure and food web dynamics The Pacific mole crab Hippa pacifica (Dana 1852) is a conspicuous scavenger of the swash zone of exposed sandy beaches on islands of the Pacific and Indo-Pacific regions. Our findings on the population structure of this species on Hawaiian beaches differed with the method of sampling used (baited vs. non-baited). The rapid attraction and aggregation of large crabs to bait stations contrasted with the population samples dominated by small crabs collected in the absence of bait. This result suggested that small individuals were excluded by larger crabs when competing for carrion resources. Burrowing velocity (mm s−1) increased with increasing carapace length, meaning that large individuals were more efficient than small crabs in the harsh hydrodynamic environment of the swash. Burrowing assays to exhaustion in laboratory conditions indicated that the ability of the crabs to cope with the harsh environment of the swash zone is a body size-dependent feature, independent of sex or fecundity state. We simulated the potential effect of the hydrodynamic and sediment instability typical of the swash zone of reflective beaches with a consecutive sequence of removals from the sediment. Following this treatment, the burrowing times of the larger crabs were shorter than those of the small individuals. Crab abundance was not related to sand grain size or to beach morphodynamics. Abundance was correlated with the amount of edible organic matter in the sediments, suggesting that H. pacifica is a highly opportunistic species, able to feed on a wider range of potential food sources than expected.

The distribution and composition of molluscan assemblages of seagrass beds in the Ensenada de O Grove (north-western Spain), are described in this paper. The studied bottoms were mostly muddy and colonized predominantly by Zostera marina L., Z. noltei Hornemann, or by both species. Molluscan fauna was dominated by gastropods and bivalves, in terms of both species richness and abundance. A total of 7641 individuals belonging to 68 taxa was identified. The most abundant species were the gastropods Peringia ulvae, Retusa truncatula and Calyptraea chinensis and the bivalves Abra alba, Loripes lucinalis and Kurtiella bidentata. Cluster and multidimensional scaling analyses based on Bray–Curtis similarity coefficient showed two distinct faunal assemblages. Group A comprised intertidal sites colonized either by Z. noltei or by Z. marina and Z. noltei on muddy sand and sandy mud bottoms and subtidal sites exclusively colonized by Z. marina in the outer part of the inlet on muddy sand with the highest values of species richness and diversity. Group B consisted of sites characterized by low values of species diversity and a species composition typical of a ‘reduced Macoma community’. The sorting coefficient and the combination of gravel, sorting coefficient and carbonates content (BIOENV analyses) and the salinity of bottom water and depth (canonical correspondence analyses) were the most important abiotic variables in explaining the structure of the molluscan assemblage.

The lancelet Asymmetron lucayanum complex was collected from subtidal (5–42 m) sandy bottom during a benthic survey designed to describe the biota of Cocos Island National Park (Parque Nacional Isla del Coco), Costa Rica, a World Heritage Site. Taxonomically significant characters of A. lucayanum (number of myotomes, gonads only on the right side of the body, shape of metapleural folds) are discussed. These lancelets were living in poorly sorted and slightly gravelly sand. Although this taxon has a circumtropical distribution, this is the first time it has been collected anywhere in the eastern Pacific.

Apseudopsis latreillii is a common tanaidacean species widely-distributed in the north-east Atlantic, but its diagnostic characters remain unspecified. Furthermore, intraspecific variation in relation to its developmental stages has not been described. Knowledge about this variation is needed owing to the difficulty of identification of the significant number of juvenile specimens within samples, particularly when sympatric with other apseudid species. Specimens from three different localities of the north-east Atlantic have been examined, and the size of 766 individuals has been measured. Study of postmarsupial development shows that the manca II is followed by two juvenile stages before reaching maturity. Males present two possible morphologies. After a preparatory stage, females pass through a sequence of copulatory instars followed by intermediate stages in which the female loses the ovisac after manca release. Characters allowing the distinction of A. latreillii specimens regardless of developmental stage are the combination of a pointed and downturned rostrum, pereonites without apophyses, three ventral spines on the pereopod 1 propodus, and one dorsodistal spine on the merus.

9 páginas, 3 figuras, 2 tablas, The abundance of the bobtail squid Sepiola atlantica was assessed for Areamilla beach at Rı´a de Vigo. Sampling was carried out monthly and simultaneously by two scuba divers at two sandy submersed zones between December 2007 and November 2009. A total of 505 specimens of S. atlantica (204 juveniles, 149 males and 152 females) were collected. The mean annual abundance of the species was 0.0190.01 ind./m2 from December 2007 to November 2008, and 0.0290.01 ind./m2 from December 2008 to November 2009. Abundances were not significantly different between the two depth zones for each year, nor for seasons. However, total abundance was significantly different between seasons. Abundance showed a seasonal pattern with the lowest values in summer. For each season populations were formed by specimens of different size during the two sampling years, as well in both depth zones. Spawning occurs throughout the year. Two peaks of recruitment, one in summer and another in autumn, were observed. Whether seasonal differences in abundance are due to migration of the individuals from shallow to deeper zones related to changes in bottom temperature is discussed., The first author was supported by a financial grant ‘Movilidad de Estudiantes para la Obtencio´n de la Mencio´n Europea en el Tı´tulo de Doctor’ from the Ministerio de Educacio´n (Spain) and a fellowship from the programme Axudas Predoutorais from Universidade de Vigo.

Invasions are common in coastal marine environments where proximity to urban areas should influence the number of non-native organisms due to the likelihood of unintentional introductions from urban centers. Invasive species are widely recognised as important agents of global change, and can colonize new habitats and even cause local extinction of native species. This study was focused on the invasive marine macroalga Sargassum muticum, a problematic invasive species on the West coast of America and in European waters. An intensive survey was carried out along the Galician coast (North West of Spain) from March to August 2008 to determine the current distribution of this species, and its relationship with level of urbanization and native macroalgal diversity. We sampled the presence of S. muticum and native macroalgae in the mid and low intertidal zones of twenty rocky shores distributed along ten rias. Rias were grouped into high and scarcely urbanized based on their population density. Results indicated that S. muticum was present in nine out of the ten rias, confirming its presence in most of the intertidal rocky shores of Galicia twenty years after it was first observed. The presence of S. muticum was not related to the degree of urbanization of the rias, and its distribution and abundance did not seem to be influenced by diversity or functional groups of native algae. In addition, there was a great variability in the percentage cover, number and length of individuals amongst localities and rias suggesting that both large-scale and local processes may play a role in the distribution of this species. This study highlights the importance of future research into the distribution and impact of introduced algae and proves the urgent need for monitoring programmes and increasing efforts to prevent and control new introductions.

After the first report of Undaria pinnatifida in north Portugal (between 1999 and 2007), a rapid spread of this species could be expected due to the presence of a stable population and the favourable environmental conditions proposed by distribution models. However, field surveys showed that U. pinnatifida was not present in most of the rocky shores in north Portugal. It seems that U. pinnatifida cannot outcompete native species outside of marinas in north Portugal. The only population in natural rocky shores was found in Buarcos, where this species was frequent. This study provides density data of U. pinnatifida that will be useful in the future to monitor changes on its abundance and distribution in the centre and south of Portugal.

The Galician rias are singular and complex estuarine systems of great economic importance. Seagrasses are key elements of the ecosystem and favor the maintenance of high species diversity in benthic communities. Nevertheless, the ecological role of seagrass meadows in the Galician rias has been only partially assessed. Peracarid crustaceans are an important component of soft-bottom faunas and have great importance for the structure of benthic assemblages. In this work, species diversity, patterns of distribution and seasonal fluctuations of peracarids (Crustacea, Peracarida) are studied in estuarine sediments colonized by two species of Zostera (Z. marina and Z. noltii) at the O Grove inlet (Ria de Arousa, Galicia, NW Iberian Peninsula). The spatial distribution of peracarid assemblages was characterized by high numerical dominances due to a few species, particularly tanaidaceans. The temporal study at a Z. marina meadow showed a strongly seasonal pattern defined by great fluctuations of the amphipod population, the latter being the dominant group in abundance and number of species. The highest numbers of species and individuals were observed in September, with minimum values in March. Analyses pointed out a high correlation among the granulometric features of the studied bottoms and the faunistic attributes. Nevertheless, the presence of the seagrasses should influence in a major way the hydrodynamic and sedimentary features of the habitat and utterly the spatial and temporal patterns observed in the peracarid assemblage in the O Grove inlet.

article i nfo Sargassum muticum is an invasive alga that affects biodiversity of benthic communities. Its proliferation in recipient communities may be due to several factors including limited grazing effects by native herbivores ("Enemy Release Hypothesis", ERH). Until now, there is no information about grazing preferences exerted by native herbivores over S. muticum and native seaweeds on the Galician coast. The aim of this study was to determine whether or not different grazers preferred S. muticum compared with native seaweeds. The hypothesis tested was that native meso- and macrograzers would prefer native seaweeds rather than the invasive seaweed S. muticum. Concentrations of polyphenols were also examined to see whether or not these compounds correlated with preferences for types of food. Despite variability of responses within and among herbivorous species, results suggested that grazers preferred native seaweeds over the invasive S. muticum. In most cases, the gastropods Littorina littorea and Aplysia punctata preferred to feed on Ulva sp., whereas L. obtusata fed mostly on Fucus vesiculosus. The sea urchin Paracentrotus lividus, however, showed no preference, feeding indiscriminately on different seaweeds. It is also important to highlight that in many cases, grazers did not show any preference (i.e. consumption when a choice was available could not be differentiated from consumption when there was no choice). These results, therefore, partially supported our prediction and reinforced the notion that well-designed experiments and analyses must be done before preference can be inferred. We suggest that the invader S. muticum is not under substantial pressure from grazers in the area of study.

Patterns of distribution and abundance of epifauna often differ markedly among macroalgal species. The hypotheses tested were that (1) assemblages of mobile epifauna associated with Laminaria ochroleuca and Sargassum muticum differed because they have different structure, and (2) assemblages of mobile epifauna associated with S. muticum differed between heights on the shore because tidal height affects physical and biological conditions. We also investigated the effect of epiphytic biomass on the composition of epifaunal assemblages. Hypotheses were tested with measuring and manipulative experiments using natural and artificial algae, and by measuring uni- and multivariate assemblage descriptors. The results indicated that epifaunal assemblages associated with natural L. ochroleuca and S. muticum differed, but only differences in epifaunal densities were likely to be related to the structure of algae since all other variables did not clearly differ between the two algae. Although structure might play an important role, other factors need to be taken into account and further experimental tests are necessary. Epifaunal assemblages associated with S. muticum did vary depending on the height on the shore, but inconsistently over time in the case of natural algae. In addition, epifaunal densities of natural algae were positively related to biomass of epiphytes in both species. Time of sampling, epiphytic load and height on the shore were the most important factors in structuring epifaunal assemblages rather than complexity of the host algae.

In the summer of 1997, 27 subtidal stations were quantitatively sampled in the Ría de Aldán. A total of 81770 individuals were collected, comprising 496 species. The distribution and composition of benthic assemblages was correlated to the sedimentary characteristics which, in turn, depend on the hydrodynamic features; those patterns are reflected in a sedimentary gradient present along the ria, which is characterized by an increasing grain size from the inner margins towards the mouth. Several faunal assemblages were determined through multivariate analyses and their composition is compared with that of several communities or facies previously described from similar sediments. The Venus fasciata community was present in clean coarse sediments of the outer ria, the Venus gallina and Tellina fabula-Tellina tenuis communities in the fine-sand bottoms at the centre and margins of the ria, a transition assemblage between the Venus fasciata and the Venus gallina communities in the medium-sand sediments, and a mix of species from the Syndosmya alba and the Amphiura communities in shallower and muddy sediments in the inner areas. In general, subtidal sediments of the Ría de Aldán showed a high benthic diversity which is related to the great sedimentary heterogeneity and the lack of significant anthropogenic alterations. Durante el verano de 1997, se hicieron muestreos en 27 estaciones submareales de modo cuantitativo en la Ría de Aldán. Se recolectaron un total de 81770 individuos, pertenecientes a 496 especies. Los análisis multivariantes permitieron distinguir varias asociaciones faunísticas cuya composición puede ser referida a comunidades o facies previamente descritas de sedimentos similares: la comunidad de “Venus fasciata” está presente en sedimentos limpios de granulometría gruesa de la parte externa de la ría, las comunidades de “Venus gallina” y “Tellina fabula-Tellina tenuis” aparecen principalmente en arena fina en las áreas marginal y central, una fauna de transición entre las comunidades de V. fasciata y V. gallina se encuentra en fondos de arena media, y los fondos someros fangosos de la zona interna están caracterizados por una mezcla de especies propias de las comunidades de “Syndosmya alba” y “Amphiura”. En general, los sedimentos submareales de la Ría de Aldán presentaron una alta diversidad bentónica relacionada con la gran heterogeneidad sedimentaria y la ausencia de perturbaciones humanas significativas.

The trophic composition of macrobenthic communities in intertidal and subtidal soft-bottoms of the Ensenada de San Simón (north-western Spain) was found to be related to a number of environmental variables. Distribution and abundance of trophic groups have been studied, to provide essential baseline information for monitoring the area, after its designation as a Natura 2000 Special Conservation Zone. Analyses of trophic data showed a numerical predominance of the herbivores in the inner part of the inlet, while sites at the oceanic-influenced area were numerically dominated by surface-deposit feeders. These dominances were mainly due to Hydrobia ulvae in the intertidal area and to polychaetes at the subtidal one. Both univariate and multivariate statistical analyses showed that the sediment composition (organic matter and silt–clay contents) and temperature of the bottom water influenced the benthic macrofauna and were correlated with their trophic composition, abundance and distribution.

Invasion of alien species poses serious threats to many ecosystems. Despite the potential of Sargassum muticum to spread and invade new areas, no attention has been given to the study of variability of structural or morphological features across different spatial scales. We employed a hierarchical sampling design to examine patterns of spatial variability of fertility and morphological variables of S. muticum over different spatial scales (quadrats, sites, locations, rias) ranging from metres to tens of kilometres We repeated the sampling in March, April and July to test for the consistency of patterns through time. There was no variability between rias (tens of kilometres apart), but substantial differences occurred at the other scales examined. Fertility and percent cover varied between locations (1.5-3 km apart), whereas morphological variables varied between sites (tens of metres apart) and quadrats (metres apart). Furthermore, patterns of variation were not consistent over time. The study demonstrated the importance of a multi-scale sampling programme for monitoring seaweed invasion.

Fluctuations in resource availability are a key factor controlling the susceptibility of an environment to invasion by non-indigenous species. Increases in the availability of resources will facilitate the invasion of habitats and assemblages. In this study, we tested experimentally the com- bined effects of intensity and temporal variability of nutrient supply on the invasion of a low intertidal macroalgal assemblage along the rocky shore of Galicia (northwest Spain) by the brown seaweed Sargassum muticum (Yendo). We estimated invasibility by measuring the number of plants, length of plants and biomass of S. muticum. Specifically, we tested the hypothesis that intensity and temporal variation of nutrient addition would affect interactively the invasion of macroalgal assemblages with high temporal variability emphasizing the effects of a high intensity of nutrient addition. Results indi- cated interactive effects between intensity and temporal variability of nutrient addition on the num- ber and length of plants of S. muticum. Moreover, temporal variability of nutrient addition had an effect on biomass of S. muticum. In addition, intensity of nutrient enrichment and temporal variabil- ity to some extent affected native assemblages, with intensity of nutrients being mainly an important driver of the percentage cover of the most abundant functional groups.

Two new trochids of the genus Antimargarita, A. powelli and A. bentarti, from the Antarctic waters are described here. A. powelli, from the Bellingshausen Sea, is distinguished by its rounded whorls, numerous spiral cords, a radula with seven lateral teeth at each side of the rachidian, and an epipodium with eight pairs of tentacles. A. bentarti, from the South Shetland Islands, is characterized by having a shell outline gradated by prominent primary spiral cords, a radula with five lateral teeth at each side of the rachidian and an epipodium with six tentacles on the left side. The diagnostic features for Antimargarita are redefined considering both shell and anatomical features and its suprageneric placement is discussed.

Macrobenthic polychaete distributions were studied along the soft-bottoms of the Ensenada de San Simón (Galicia, NW Spain). Results suggest that the distribution and abundance of polychaetes in the inlet were highly dependent on depth, sediment characteristics (grain size, organic matter and calcium carbonate content) and bottom water temperature. In the inner area of the inlet, intertidal bottoms colonised by the seagrasses Zostera marina and Z. noltii were dominated by spionids and capitellids, and showed low species number and diversity. Shallow muddy bottoms of central areas were mostly dominated by ampharetids, terebellids and cirratullids. These families along with paraonids, maldanids and syllids were the most abundant families in the deeper subtidal muddy bottoms at the mouth of the inlet. These sediments also showed the highest number of species, diversity and density of individuals., La distribución de los poliquetos macrobentónicos ha sido estudiada en los fondos blandos de la Ensenada de San Simón (Galicia, NO España). La profundidad, las características del sedimento (granulometría, contenido en materia orgánica y carbonatos) y la temperatura del agua del fondo fueron los principales factores que determinaron la distribución y abundancia de los poliquetos en la ensenada. En la zona más interna, los fondos intermareales colonizados por las fanerógamas Zostera marina y Z. noltii estuvieron dominados numéricamente por espiónidos y capitélidos, y mostraron bajos valores de diversidad y número de especies. Los fondos fangosos someros del área central presentaron una fauna de poliquetos dominada principalmente por anfarétidos, terebélidos y cirratúlidos. Asimismo, estas familias estuvieron presentes en los fondos más profundos de la boca de la ensenada, donde paraónidos, maldánidos y sílidos mostraron una dominancia numérica importante. Los máximos valores de diversidad, número de especies y densidad de individuos se registraron en estos fondos submareales fangosos.

Peracarids (Crustacea: Peracarida) are an important component of soft-sediment faunas and are considered good indicators of quality of water and sediments. Nevertheless, little is known about diversity of peracarid crustaceans on the shallow subtidal sediments of Playa America, a sandy beach in the Ensenada de Baiona (Galicia, NW Spain). Therefore, the peracarid fauna of its shallow subtidal zone was studied in a fine-sand site at 4-m depth from February 1996 to February 1997. Monthly sampling yielded a total of 4753 individuals belonging to 60 species. Amphipods were dominant in number of individuals and species followed by cumaceans. The assemblage showed a stable composition in species through the year and was numerically dominated by a few species, namely the amphipods Siphonoecetes kroyeranus and Microprotopus maculatus and the cumacean Pseudocuma longicorne. These species showed large monthly fluctuations in abundance, with maximal values between summer and autumn.

Although frequent studies have been made on the benthos assemblages living in the Southern Ocean, few studies have dealt with molluscan assemblages and ecology. During the research programmes BENTART carried out in austral summers of 2003 and 2006 in a study area including Low Island, West Antarctic Peninsula, Bellingshausen Sea and Peter I Island, 45 stations were sampled using quantitative box-corer, Agassiz trawl, epibenthic sledge and rock dredge, at depths of 53–3,304 m. These data were used to search and analyse the malacological assemblages. A total of 2,889 living specimens of molluscs belonging to 139 species of shelled Gastropoda, Bivalvia and Scaphopoda were recoded. Gastropods were the best-represented in species richness, but the bivalves accounted the major abundance and Cyamiocardium denticulatum (460 individuals) was the most abundant species. Species richness varied from 1 to 37 species and diversity showed great variations at different stations. Four groups of stations of low similarities and some differences in faunistic composition were observed: one that gathers the Antarctic Peninsula and Peter I Island, one that also includes the Low Island, and two composed by stations of Bellingshausen Sea.

Peracarid crustaceans inhabit many marine benthic habitats and are good indicators of environmental conditions. There is, however, a lack of information about diversity and distribution of peracarid crustaceans on the shallow subtidal sediments of the Galician rias. In the summer of 1997, 27 subtidal stations were sampled in the Ria de Aldan, a ria on the southern margin of the mouth of the Ria de Pontevedra (Galicia, NW Spain). A total of 16,191 peracarid individuals were collected, comprising 125 species belonging to five orders. Amphipods were dominant in number of species and individuals, followed by isopods and cumaceans. Multivariate analyses of these data indicated that depth and sediment granulometry were major determinants of distribution and composition of peracarid assemblages in the ria.

Depth-related zonation and diversity patterns are important topics in the study of deep-sea fauna, at both species and assemblage levels. These patterns may be attributed to complex and combined physical and/or biological factors. The lack of information about the West Antarctic deep sea is an important handicap to understanding the global-scale benthic diversity patterns. Detailed studies of the bathymetric distributions and diversity of deep-sea species in the Antarctic are needed to elucidate the factors contributing to global-scale benthic patterns. This study, based on a large data set, examined the bathymetric distribution, patterns of zonation and diversity–depth trends of gastropods and bivalves in West Antarctica, from the South Shetland Islands to the Bellingshausen Sea, a very poorly known area. A total of 647 individuals of gastropods belonging to 82 species and a total of 2934 individuals of bivalves belonging to 52 species were collected. Most gastropods showed discrete depth distributions, whereas most bivalves showed broader depth ranges. Replacement of species with depth was more gradual for bivalves than gastropods. Nevertheless, three bathymetric boundaries could be recognized: (1) a continental shelf zone from 0 to 400 m with a gradual rate of succession, (2) an upper slope zone from 400 to 800 m and (3) a lower slope zone from 800 to 2000 m, extending to 3300 m for bivalves. Diversity patterns were complex for both groups with no significant trends with depth. r 2007 Elsevier Ltd. All rights reserved.

The composition and spatial distribution of the polychaete fauna on the subtidal soft sediments of the Ría de Aldán (Galicia, north-western Spain) were studied by means of quantitative sampling and multivariate analysis. The faunal distribution was mainly conditioned by a sediment gradient defined by decreasing grain size, from the mouth towards the inner margins of the ría. The coarse and medium sand fauna was mainly dominated by pisionids, spionids and syllids. Finer sediments (fine sand to mud) showed a greater abundance of paraonids, spionids and cirratulids and deposit feeding species. The greatest number of species and diversity were found in coarse sediments.

Distribution and abundance of the macrobenthic fauna was studied in the intertidal and subtidal soft-bottoms of the Ensenada de San Simón (north-western Spain). Depth and grain size were the most important factors in determining patterns of distribution of the macrozoobenthos. A reduced Macoma community was present in the inner area of the inlet structured in two facies subdivision in the community that does not affect its qualitative composition: the first one was in intertidal areas associated with meadows of the sea grasses Zostera noltii and Z. marina and defined by the dominance of Hydrobia ulvae; the second facies in intertidal sediments was characterized by the dominance of Tubificidae and nematodes and Pseudopolydora paucibranchiata. The poverty of these bottoms in number of species can be due to salinity fluctuations and human activities developed in the area. Subtidal bottoms were characterized by a Syndosmya(=Abra)alba community. Two facies were detected: one facies located in shallow subtidal bottoms with H. ulvae and Thyasira flexuosa as characteristic species, and a second facies in deeper areas, characterized by the polychaetes Ampharete finmarchica, P. paucibranchiata, Aphelochaeta marioni, Melinna palmata and Paradoneis lyra.

The structure and spatial distribution of the macrofauna community of the Bellingshausen Sea in the western sector of Antarctica was studied during the ‘BENTART–06’ oceanographic expedition. This is one of the least explored Antarctic seas. A total of 20 box cores were sampled at 11 stations ranging from 157 to 3,304 m depth, using an USNEL-type box corer (BC) dredge. Representatives of 25 higher taxa of invertebrates were collected. Deeper sampling sites were less rich in taxa (4–7 taxa), whereas the figures were higher at shallower sites (up to 17 taxa). Faunal density on the sea bottom revealed a horizontal spatial gradient from the western sites with extremely low figures (90 indiv./m2) towards the eastern ones with the highest figures (1,360 indiv./m2) close to the Antarctic Peninsula. Several abiotic factors (depth, redox, organic matter, carbonates and particle size of surficial sediments) were measured simultaneously on the sea floor to characterise the substrate preferences of the fauna. Positive correlations were found between the faunal distribution and a combination of depth, redox values, and organic matter content of sediments. This indicates decreasing availability of food in the deeper bottoms of the Bellingshausen Sea with a prevalence of depauperated bottoms dominated almost exclusively by a foraminiferans community., Sí

Peracarida are an important component of soft sediment faunas and are considered good indicators of the quality of water and sediments. Nevertheless, little is known about the diversity and distribution of peracarid crustaceans on the shallow subtidal sediments of the Galician Rias (N.W. Spain), and about the Ensenada de Baiona in particular. Therefore, the peracarid fauna of this inlet was studied at 21 subtidal sites in December 1995. Sampling yielded 5749 individuals belonging to 91 different taxa. The number of species was particularly high when compared to values recorded from similar geographical areas. Amphipods were dominant in numbers of individuals and species. By means of multivariate analyses, several assemblages were determined whose species composition was related to the distribution of sediments in the inlet. Los Peracarida constituyen un componente importante de la fauna en fondos blandos marinos y son considerados un buen indicador de la calidad del agua y los sedimentos. Sin embargo, existe poca informacion sobre la diversidad y distribucion de los crustaceos peracaridos en los sedimentos submareales de las Rias de Galicia en general, y en particular de la Ensenada de Baiona (N.W. Espana). Debido a ello, la fauna de peracaridos de esta ensenada fue estudiada en 21 estaciones de muestreo submareales en Diciembre de 1995. Se obtuvieron 5749 individuos pertenecientes a 91 taxones diferentes. El numero de especies total fue particularmente alto en comparacion a los referidos de otras areas geograficas similares. Los anfipodos constituyeron el grupo dominante en numero de individuos y de especies. Los analisis multivariante permitieron distinguir varias asociaciones de peracaridos coincidentes a grandes rasgos con la distribucion de los sedimentos en la ensenada.