Soft-bottom Macrofauna Research Articles

Decapod Crustacean Records from A Collection of Marine Soft-Bottom Macrofauna of the Italian Waters Supporting the Update of Checklists and Registers of the Mediterranean Basin

Decapod crustaceans are important components of the fauna of soft-bottom habitats. In this work, the records of decapod crustaceans are provided through the analysis of a large soft-bottom benthic macroinvertebrates dataset of the Central Mediterranean Sea. Decapod crustacean assemblages were collected in the last twenty years by a Van Veen grab in 42 study sites located along the Italian coasts at depths ranging from 1 up to 120 m. The spatial distribution of the crustaceans examined, which include 120 species belonging to 40 families, was investigated according to the biogeographical zones identified in the Italian seas. The spatial distribution of 36 species was updated, comparing the ISPRA decapod crustacean dataset with the most recent Italian checklists. For the species updated, the number of specimens, the year and season of sampling, and environmental data, such as the bathymetric range and habitat details, are provided for each site investigated. Data are discussed and compared with the existing literature, also referring to what is reported in the World Register of Marine Species (WoRMS), with the aim of contributing to the knowledge of the biodiversity of the marine species and supporting the updating of checklists and registers in the Mediterranean Basin.

Effects of Organic Enrichment on Bioturbation Attributes: How Does the Macrofauna Community Respond in Two Different Sedimentary Impacted Areas?

We assessed the influence of different organic matter (OM) inputs associated with terrigenous/freshwater allochthonous and sewage derive on bioturbation and irrigation potential community indices (BPc and IPc) of the soft-bottom macrofauna community. The macrofauna was sampled from two different sedimentary impacted areas, in front of the Po River Delta (northern Adriatic Sea) and sewage discharge diffusion zone (Gulf of Trieste). The highest values of BPc and IPc were observed at the northward sampling stations of the prodelta and the stations 25 m distance in front of the main sewage outfall. Species richness showed high values in the prodelta likely due to the OM positive effect from the delta, and it increased with increasing distance from the pipeline due to the effect of OM from the sewage discharge. The bioturbation indices differed due to the presence of surface deposit feeders and the injection depth (from 2 to 5 cm) with limited movement at the station located northwards in the prodelta and 25 m distance in the diffusion zone. We infer that the difference in bioturbation indices was likely due to the effects of grain-size composition and the degree of organic enrichment in both study areas.

Impact of and recovery from seabed trawling in soft-bottom benthic communities under natural disturbance of summer hypoxia: A case study in subtropical Hong Kong

Bottom trawling has widespread impact on the structure and composition of benthic communities. In this study, soft-bottom macrofauna in a heavily trawled area and an adjacent marine park that has been closed to bottom trawling for more than ten years were sampled, allowing to investigate the impact of and recovery from trawling. Both areas were equally affected by seasonal summer hypoxia. Polychaetes were the most abundant at trawled (78-86%) and non-trawled (85-94%) sites in both summer and winter. The non-trawled sites inside the marine park area had a lower level of species composition and abundance as compared to the trawled sites in summer, whereas in winter the benthic communities at these trawled and non-trawled sites appeared much similar with the majority of the identified taxa being dominated by new recruiting juveniles in both sampling areas. Results of permutational multivariate analysis of variance (PERMANOVA) on transformed infaunal abundance and biomass data revealed significant differences (p<0.05) between trawled and non-trawled treatments and seasons, as well as their interactions. Pair-wise a posteriori PERMANOVA further indicated significant differences for the abundance and biomass data in summer but insignificant differences in winter. PERMANOVA of the biological traits of infauna weighted with transformed biomass also confirmed significant difference for seasons only. Such findings imply that the effect of season was more important than that of trawling especially on the biological trait structure of the benthic communities. In addition, bottom trawling may contribute to a higher level of dissolved oxygen when the area suffered from hypoxia, resulting a higher biodiversity in the trawled area in summer. By comparing data taken prior to closure of the marine park from trawling, the recovery of infaunal community has been slow over the 12 years as a trawl-free area. Apart from natural disturbance of summer hypoxia, such recovery could also be complicated with the presence of artificial reefs deployed within the marine park, which may affect the hydrodynamics of the benthic environment and modify the community structure and function.

Positive effects of the decrease of hydraulic dredging due to the SARS-CoV-2 pandemic on benthic fauna and clam harvesting in the northern Adriatic (Mediterranean Sea)

The Northern Adriatic Sea is historically subjected to intensive bottom trawling and hydraulic dredging for clam harvesting, which are known to have deleterious effects on benthic habitats. In order to gather information on the destructive impact of hydraulic dredging, we investigated the abundance and assemblage composition of soft-bottom macrofauna in a coastal area of the North Adriatic Sea (Mediterranean Sea), by comparing the year before and the year after the reduction of the fishing effort imposed by the SARS-CoV-2 pandemic. Our results indicate that macrofaunal assemblages changed significantly in abundance and composition. While bivalves doubled their abundance, other opportunistic scavenger taxa decreased or disappeared. Despite dredging intensity decreased more than 50% in 2020, the harvesting of Chamelea gallina increased from 18,706 tons in 2019 to 19,092 tons in 2020. Overall, it could be concluded that the decrease in clam fishing effort imposed by the lockdown resulted in an increase of the yearly clam harvesting. Our study points out that the recovery of soft-bottom macrofaunal assemblages due to the long-term decrease of clam harvesting has potentially important benefits, and that the establishment of long fishing stops, or of fishery restricted areas / marine protected areas could lead to a more sustainable fishery and the potential increase of the clam fishery yields.

Assessing the sewage discharge effects on soft-bottom macrofauna through traits-based approach

We assessed the effect of sewage-derived materials on the structural and functional attributes of the soft-bottom macrofauna at an increasing distance from the entire diffusion area. Our results showed clear spatial changes of macrofaunal density and biomass along the distance gradient from the main outfall. High values of biodiversity, species composition, and species linked to organic enrichment near the duct suggested that moderate organic stress affected this community. The traits analysis abundance-based, compared to biomass-based one, distinguished most clearly sewage contamination conditions. Functional diversity displayed spatial patterns with higher values in the less impacted sites and was significantly related to species numbers and the biotic indices (like M-AMBI). This approach is ideal for detecting macrofaunal functional changes due to sewage contamination. Thus, we infer that traits analyses could offer great potential for environmental assessment and monitoring of coastal areas influenced by human activities.

An artificial reef at the edge of the deep: An interdisciplinary case study

Just nearby the largest submarine canyon in Europe – off the western coast of Portugal – is located the Nazaré artificial reef (NAR) deployed in 2010 and the first of its kind in this coast. NAR aimed to improve social and economic resilience of the local communities, mainly by creating a safer and closer area for fishing and to enhance commercially exploitable marine resources. The innovative part of this research lies on the fact that for the first time was developed a multidisciplinary approach for NAR. Scientific evidence from fieldwork shows that in 2015 the reef was already mature and colonized by abundant and diversified macrobenthic assemblages. No evidence of negative impacts of NAR on the soft bottom macrofauna was observed, as assemblage composition in the NAR area and in the vicinity areas is similar. In relation to the primary producers that support the subsequent food chain, there also seems to be a balance between NAR and the surrounding area since phytoplankton was equally abundant throughout the area. Experimental fisheries and underwater visual census results on ichthyofaunal communities in the reef revealed high abundance and low levels of species richness, pouting, Trisopterus luscus Linnaeus, 1758 being the most common fish species found. Concerning NAR socio-economic impact, results from direct site observations (DSOs) showed that only some small-scale fishing vessels were eligible to operate on the NAR area. Thus, comparatively to non-AR areas nearby reef use by fishing vessels differs according to spatial and temporal strata. In what perception was concerned, the NAR has contributed to fish aggregation, though being populated mostly by small fish. Fishers have stated that some factors seemed to have changed after reef deployment. Notwithstanding, the NAR may have been a valuable contribution to an apparently overall socio-economic positive impact on the local fishing community that can be corroborated by the presence of good biological indicators.

Soft-bottom macrofauna along the coast of Bahía de Los Ángeles, Gulf of California, during the summer and winter

This work constitutes an effort to evaluate benthic biodiversity in Bahía de Los Ángeles, Gulf of California, Mexico. To characterize macrofauna at the family level, 2 sampling campaigns took place during summer 2013 and winter 2014 at 6 coastal stations. A total of 18,403 invertebrates were collected, 7,880 in summer and 10,523 in winter. These invertebrates were grouped into 6 phyla and 110 families, comprising 39 mollusks, 33 crustaceans, 30 polychaetes, 5 echinoderms, 2 cnidarians, and 1 cephalochordate. In both sampling periods, mollusks were the dominant group, especially in summer, followed by polychaetes and crustaceans, which were more abundant in winter. Ten new records were established for the area. The most abundant trophic groups were deposit feeders and carnivores. This research could be used to evaluate future changes in benthic assemblages in Bahía de Los Ángeles.

Structure of the macrozoobenthos assemblages in the central part of the northwestern Black Sea shelf (Zernov's Phyllophora field) at the beginning of the 21<sup>st</sup> century

In the first half of the 20th century, there was an extensive biocoenosis of the unattached red algae Phyllophora crispa on the mussel muds of the central section of the Black Sea’s northwestern shelf, which is known as Zernov’s Phyllophora Field (ZPF). At that time, the area of ZPF was approximately 11000 km2. More than a century after the description of ZPF, long-term changes in its phyto- and zoobenthos have been noted. A period of ecological crisis of the Black Sea ecosystem during the second half of the 20th century was destructive for the phytobenthos of ZPF, with the complete degradation of unattached Phyllophora biocoenosis. In contrast, after a sharp decline in the quantitative development of macrozoobenthos of the soft bottoms in the 1970s, its recovery to pre-crisis levels in the 2010s was noted. Despite the difference in the aforementioned phyto- and zoobenthos dynamics, habitat in the 4025 km² area of the botanical sanctuary of national importance “Zernov’s Phyllophora Field” was recognised as Critically Endangered (CR) within the European Red List of Habitats. In this context, the goal of the present study is to clarify the applicability of the CR category to the entire benthic complex of ZPF water area and to assess the current biocoenotic structure and habitat ordination of the zoobenthos on soft bottoms of the ZPF water area in the current conditions of Black Sea de-eutrophication. The obtained results indicate the presence of one biocoenotic complex (Mytilus galloprovincialis) and three subcomplexes in the zoobenthos of ZPF, where the bivalves Mytilaster lineatus, Modiolula phaseolina, as well as Polychaeta are the next most important subcomplex-forming taxa. Throughout all studies of ZPF, relative stability in the biocoenotic representation of the bottom fauna—with the dominance of M. galloprovincialis—has been observed. Due to the current levels of development in both the soft-bottom macrofauna and assemblages of unattached alga Phyllophora, two different habitats were proposed for identification in the water area of the botanical sanctuary. The first habitat – “Aggregations of unattached red algae Phyllophora in the central part of the northwestern shelf of the Black Sea" – was degraded and can be classified as a CR habitat. The second one – “Pontic circalittoral biogenic detritic bottoms with dead or alive mussel beds, shell deposits, with encrusting corallines and attached foliose sciaphilic macroalgae” – represents the soft-bottom biotope and was associated with the biocoenotic complex M. galloprovincialis, proposed for classification as Least Concern. In accordance with three biocoenotic subcomplexes of complex M. galloprovincialis, the spatial position of the three subhabitats was determined on the soft-bottom in the water area of ZPF.

Shelf and deep-water benthic macrofauna assemblages from the western Gulf of Mexico: Temporal dynamics and environmental drivers

Shelf and deep-water soft-bottom macrofauna were explored in the western Gulf of Mexico in terms of species and functional trait assemblages. Their variation was analysed as functions of depth and time, and the relationship with sea-bottom environmental conditions was examined to disentangle their association with potential environmental drivers. Four consecutive cruises (two per year, at the end of the dry and rainy seasons) were performed during 2016–2017 at 27 fixed stations distributed from 42 to 3565 m depth. Changes in macrofauna composition were tested considering species and functional trait assemblages. Environmental variables associated with sediment features (i.e., grain structure, organic matter, pH, redox), oceanographic conditions (i.e., temperature, dissolved oxygen, particulate organic carbon flux) and potential contaminants (i.e., hydrocarbons and metals) were analysed to identify potential drivers that would shape the structure of macrofauna assemblages. The results suggest that the structures of both species and functional trait assemblages change according to depth and show temporal variation in composition at seasonal and interannual scales. The effect of temporal variation represented about 12% of total variation in the assemblages (11.4 for species and 12.5% for functional-traits). Different patterns of spatial and temporal variation between shelf and deep benthic communities were observed. Variation in species assemblages on the shelf were related to the variation in lead, polycyclic aromatic hydrocarbons and the fine sand ratio. In the deep benthos, particulate carbon flux showed high correlation with the spatial and temporal variation in species assemblage. In the deep benthos the changes in the species assemblage between the dry and the rainy seasons and the interannual variation were highly correlated with particulate organic carbon input in the area.

Hydrodynamic Conditions Effects on Soft-Bottom Subtidal Nearshore Benthic Community Structure and Distribution

This study assesses the impacts of wave action and freshwater outflow on soft-bottom benthic macrofauna spatial distribution and temporal stability along the highly exposed French Basque coast. Sediment characteristics and macrofauna abundance have been seasonally investigated during two years for nine stations located at the same (6 m) depth and spread over three subtidal sites showing distinct exposure levels. Wave climate has been determined through an operational numerical model. A total of 121 taxa were recorded, gathered in three main faunal assemblages, as revealed by classification and ordination methods. Non-parametric multivariate multiple regression (distance-based linear model) showed that the variations in macrofaunal distribution can be explained by hydrodynamic conditions. Wave exposure strongly linked to estuarine inputs were the most relevant abiotic factors influencing distributional patterns and functional structure as described by biological traits analysis. Despite the influence of these abiotic variables affecting sedimentary dynamics, seasonal stability was observed in macrobenthic assemblages composition suggesting an ability to recover from natural disturbances such as (e.g.) winter storms. In this way, these results provide baseline knowledge for future ecosystem and resource management in shallow subtidal areas strongly exposed to swell and freshwater outflow where soft-bottom macrozoobenthic communities are less frequently studied.

Testing marine regional-scale hypotheses along the Yucatan continental shelf using soft-bottom macrofauna

Different hypotheses related to the regional-scale configuration of the Yucatan Continental Shelf (YCS) between the Gulf of Mexico (GoM) and the Caribbean Sea have been proposed. Hypotheses regarding its regional boundaries include: (i) an ecoregional boundary at Catoche Cape, dividing the Western Caribbean and the Southern GoM ecoregions; and (ii) a boundary within the Southern GoM ecoregion at 89°W, separating the West and Mid-Yucatan areas. We tested the hypothesis of no variation in benthic macrofaunal assemblages between regions delimited by the former boundaries using the species and functional traits of soft-bottom macrofauna. We considered that the depth and temporal environmental dynamics might interact with regional variations, generating complex benthic community patterns. The data were collected over five years (2010–2012, 2015–2016) at 86 stations (N = 1, 017 samples, 10–270 m depth), comprising 1,327 species with 45 combinations of functional traits. The variation in species composition and functional trait assemblages were both consistent with the occurrence of three separate regions in the Yucatan Peninsula (West Yucatan, Mid-Yucatan and Western Caribbean). This regional configuration was consistent with changes in assemblage structure and depth zonation as well as temporal variation. Along with spatial and temporal variation, diversity diminished with depth and different regions exhibited contrasting patterns in this regard. Our results suggest that the spatial and temporal variation of soft-bottom macrofauna at YCS demonstrate the complex organization of a carbonate shelf encompassing different regions, which may represent transitional regions between the Caribbean and the GoM.

Effect of Species Invasion on Transport of Solutes at Different Levels of Soft Sediment Macrofauna Diversity: Results from an Experimental Approach

Different irrigation or ventilation strategies by macrofauna may provide a competitive advantage to tolerant species invading impacted benthic systems and alter benthic-pelagic coupling. To comparatively analyze the effects of an exotic and a native polychaete burrower on sediment-water exchanges, two laboratory experiments were performed. In the first experiment, the invasive spionid polychaete Marenzelleria neglecta was added to defaunated sediments and fluxes of the inert tracer (bromide, Br−) were measured to quantify the effects of irrigation by the worm on the tracer transport. In the second experiment, M. neglecta or the native polychaete Hediste diversicolor were introduced to a relatively diverse Baltic soft-bottom macrofauna community. The effect of species on fluxes of reactive solutes (ammonium, NH4+, and phosphate, PO43−) and transport rates of Br− was estimated. The results indicate different invasion effects depending on the characteristics of the recipient habitat. In defaunated sediments, a single specimen of M. neglecta significantly enhanced originally low solute exchange rates. Total tracer flux was significantly enhanced over diffusive flux by a factor of 1.6 ± 0.14 (n = 3). In natural sediments, on the other hand, the addition of either M. neglecta or H. diversicolor had no statistically significant effects on benthic fluxes. Tracer flux estimates between control and treatment incubations differed by less than 10% on average, and both reactive solutes tended to increase by 10 to 40% after additions. One specimen of M. neglecta in cores with defaunated sediment generated approximately 20% of the tracer flux produced by the relatively diverse macrofauna community. Estimated net tracer fluxes in two experiments corresponded well with the number of adult polychaetes found in sediments (r2 = 0.73, p = 0.005, n = 12). The invasive M. neglecta produced a small effect on fluxes in biodiverse sediments, comparable to those of H. diversicolor, but it may deeply alter porewater chemistry in azoic sediment. As M. neglecta tolerates chemically reduced and sulphidic conditions, its bioirigation may favor sediment reoxidation and ultimately the recolonization by less tolerant, native species.

Intra-Annual Variability of a Benthic Amphipod Assemblage (Crustacea: Amphipoda) in a Tropical Shallow Coastal Environment

The community structure of tropical soft-bottom macrofauna is generally considered temporally stable. Here, we document the intra-annual variability of an amphipod assemblage from a tropical benthic habitat. The study was carried out in a shallow coastal environment of the southern Gulf of Mexico, based on historical data obtained from monthly samplings from June 2007 to May 2008, which encompassed three seasons: rainy, cold fronts and dry. Water and sediment variables were recorded to characterize the habitat, and amphipods were collected to assess changes in composition, density, and feeding modes. Using habitat characteristics, the predefined climatic seasons were examined with a discriminant analysis to order the sampling months into the three seasons. A nested analysis of variance showed that, at monthly and seasonal scales, the assemblage is more variable than expected. The species richness and density varied significantly over time, mostly at the monthly scale. Furthermore, a correspondence analysis showed that the species composition was distributed seasonally; this ordination was validated by a permutational multivariate analysis of variance. Finally, a redundancy analysis between species and habitat characteristics revealed seasonal relationships between the environmental conditions and the amphipod fauna. We propose a conceptual model to summarize the joint variation of environmental and biological factors. The present study suggests that an ecological turnover occurs at the site, along with habitat partitioning among the species through time, which depends on the species and its trophic preferences.

Assessment of biodiversity and environmental quality using macrozoobenthos communities in the seagrass meadow (Gulf of Gdańsk, southern Baltic)

Abstract This study shows the macrozoobenthic biodiversity and the quality status of the Zostera marina meadow in the Gulf of Gdansk. To our knowledge, this is the first study focused on the assessment of environmental quality based on macrofauna occurring on such a small and specific habitat as a seagrass meadow. The meadow is dominated by Zostera marina, but also Zanichellia palustris and Potamogeton pectinatus are present. Compared to the soft bottom macrofauna in the southern Baltic, the biodiversity of macrozoobenthos is very high, which is reflected in 33 taxa observed during the whole research, while the mean number of taxa was 12. There were also some taxa found only on the bottom overgrown with vegetation, e.g. Idotea balthica or even taxa that are currently rarely observed in the Gulf of Gdansk, e.g. Gammarus locusta or Gammarus ineaquicauda. Nineteen percent of the stations were classified into the very good quality status and 50% into the good quality status, so the environmental status of this meadow based on the BQI index is assessed as good. Given these results, this is probably one of the best preserved meadows in the southern Baltic.

Cumacean assemblages on the Levantine shelf (Mediterranean Sea) – spatiotemporal trends between 2005 and 2012

ABSTRACTCumacea (Crustacea, Peracarida) are an important component of soft-bottom macrofauna. Their assemblages are influenced by environmental parameters, including the presence of alien species. Cumacean assemblages from 443 samples collected between 2005 and 2012, at 148 sites along the Israeli Mediterranean coast were analysed. In all, the 31,508 cumaceans were identified to 18 species. Three of the species, Eocuma rosae, E. sarsii and Scherocumella gurneyi, are considered alien for the Mediterranean Sea. Pseudocuma longicorne, S. gurneyi and Cumopsis goodsir were the most abundant species in our samples. Cumacean densities were significantly higher in spring than in autumn, except on the shelf, where the opposite was observed. At the deeper sites (55–63 m) species composition changed between seasons, suggesting a migration of some shallow-bottom dwellers (P. longicorne, Iphinoe spp.) into deeper waters in wintertime. Comparison among years revealed great differences in density, especially in P. longicorne, which experienced an outbreak in 2009. Although seasonal changes may be explained by the natural dynamics of the species' life cycles, inter-annual variability is more difficult to explain. It may be related to environmental changes and especially to the infralittoral hypernutrification along the southern Israeli coast, causing an increase in food availability. Cumacean alien species occurred only in Haifa Bay.

COMUNIDAD MACROINFAUNAL DE FONDOS BLANDOS SOMEROS TROPICALES (CARIBE COLOMBIANO)

With the aim to charactenze the soft-bottom macrofauna and its spatial and tomporal distnbution patterns in the Santa Marta area, a two years sampling program was performed at depths between 7 to 60m Density, biomass and diversity of tho community woro dotorminod. Tho BIOENV method was applied in order to relate the distnbution of the associations and the environmental vanables (depth, turbidity, organic matter, organic carbon, organic nitrogen, organic phosphorus and median particle diamotor). A density of 1499 indiv * m, and 10.9 g * m* wot biomass woro obtainod. Tho collected organisms belonged to six taxa; polychaetes. crustaceans, sipunculids, molluscs, bryozoans, and ccfunoderms; the first ono was tho most important in terms ol abundance and biomass. Four Ousters were obtained following a depth gradient, but no clear temporal pattom became evident. Due to a targe number ol generalist gonora among the dusters, a sole community conformed by several zones with diffuse boundanos was defined Depth is the vanable which better oxpiams tho distribution of the community; the correspondng correlation coefficient was high in companson with othermacrobenthos studies earned oul *1 the Canbbean as well as m temperate, unpoilutod areas. In the Caribbean. depth alone, or with other variables, exhibits the best relationship with tho biological structural paneros.

Effects of proximity to offshore fish farms over soft-bottom macrofauna

Sea-cage fish farms impact the seabed within their immediate vicinity, potentially affecting recipient communities. We assessed whether proximity to three sea-cage fish farms at the Canary Islands altered patterns in the abundance, assemblage structure and richness of soft-bottom macrofauna. We related among-farm variability in dissimilarities in macrofaunal assemblage structure between seabeds beneath cages and controls to differences in hydrodynamics, production and seabed topography. Contrasting patterns of species abundances with varying proximity to fish farms were observed: some species decreased while other species increased their abundances with increasing distance at some farms. Although faunal assemblages at 0 m (i.e. beneath the cages) were different, in terms of assemblage structure, from those found at controls, pairwise differences in assemblage structure among distances away varied among the studied fish farms. Species richness showed inconsistent patterns with proximity to cages among fish farms. In summary, inconsistent patterns of macrofaunal assemblages with varying proximity to aquaculture facilities preclude confident predictions on the way offshore aquaculture alters macrofauna in the study region.

Inventory of the marine soft bottom macrofauna of São Sebastião Channel, southeastern Brazilian continental shelf

Analysis of macrofauna from 91 quantitative soft-bottom samples (from five surveys) obtained in the Sao Sebastiao Channel at depths ranging from 2 to 45 m yielded 431 species from a total of 38,630 individuals. The present contribution gives a list of the species found in the area and their depth distribution and sedimentary preferences (granulometric characteristics of the sites where they occurred). This is the first complete inventory of the subtidal invertebrate soft-bottom fauna of the Sao Sebastiao Channel, a peculiar marine area under crescent human impact.

Estructura de la comunidad y distribución vertical de la macrofauna de fondos blandos en isla Gorgona, Pacífico Colombiano

Soft bottoms are important in marine ecosystems but their ecology have been less studied in the tropics than in temperate areas. This article describes the temporal, spatial, and vertical distribution of the community structure of subtidal soft bottom macrofauna on Isla Gorgona, Colombian Pacific. Samples were collected in March and June 2011 by corers at 10m depth at five points around the island. Seventy-three species were recorded; polychaetes (55%) and crustaceans (30%) were the dominant groups in number of individuals. The community structure assessed by classification and ordination analysis did not change temporarily, but it shows differences between sampling points, due to the structure of the substrate. The highest abundances of macrofauna were recorded at points with dominance of fine particles (Farallones). However, another point with a similar substrate (Planchon) showed low abundance, apparently due to bioturbation exerted by the fishHeteroconger sp. The presence of Heteroconger sp. in El Planchon could also affect the vertical distribution of the macrofauna, where their relative abundance was homogeneous across the analyzed layers (1-2-3-4-5-10cm). In the other four sites, the abundance of the macrofauna was mainly limited to the first two centimeters of the sediment. Playa Blanca and Remanso showed substrates composed mainly of gravel, recording at the last sampling point the lowest richness, diversity and abundance. Rev. Biol. Trop. 62 (Suppl. 1): 169-188. Epub 2014 February 01.

Diversity and spatial distribution patterns of the soft-bottom macrofauna communities on the Portuguese continental shelf

This study presents a comprehensive assessment of the diversity and spatial distribution of the soft-bottom benthic macrofauna communities along the Portuguese continental shelf and discusses the relationship between biological and environmental data. A total of 145 sites were sampled using a 0.1m2 Smith–McIntyre grab covering the whole west and south coast of Portugal, at depths ranging 13 and 195m. More than 30,000 specimens were identified corresponding to 737 taxa, mostly annelids (43% of the total taxa). The most frequent species were Ampharete finmarchica, Ampelisca sp. and Lumbrineris lusitanica while the most abundant were Mediomastus fragilis, Polygordius appendiculatus and Ampharete finmarchica. Abundance ranged between 7 and 1307 specimens per 0.1m2 and alpha diversity reached a maximum of 96 taxa per 0.1m2. Gravel sediments, and shallow and sheltered areas presented higher diversity values than mud sediments and deeper sites. Six major benthic assemblages were identified: (a) Coarse sediments, mostly located on the western shelf, with Protodorvillea kefersteini, Pisione remota, Angulus pygmaeus and several other interstitial species; (b) near shore fine sands with Magelona johnstoni, Urothoe pulchella and Angulus fabula; (c) Abra alba community in northwestern deep muddy sands; (d) Southwestern very deep muddy sands characterized by Galathowenia oculata, Lumbrinerides amoureuxi and other burrowers and tubicolous polychaetes; (e) Euchone rubrocincta, Nematonereis unicornis and other warmer water species in muddy sands of the southern and sheltered shelf; and (f) muds dominated by Sternaspis scutata, Heteromastus filiformis and Psammogammarus caecus. Sediment grain-size, organic matter, depth and hydrodynamic regime were the variables best related to the macrofauna distribution patterns, highlighting the transitional characteristics of this northeastern Atlantic area, where northern and subtropical faunas can coexist.