Soft-bottom Communities Research Articles

Size Structure of Marine Soft-Bottom Macrobenthic Communities across Natural Habitat Gradients: Implications for Productivity and Ecosystem Function

Size distributions of biotic assemblages are important modifiers of productivity and function in marine sediments. We investigated the distribution of proportional organic biomass among logarithmic size classes (2−6J to 216J) in the soft-bottom macrofaunal communities of the Strait of Georgia, Salish Sea on the west coast of Canada. The study examines how size structure is influenced by 3 fundamental habitat descriptors: depth, sediment percent fines, and organic flux (modified by quality). These habitat variables are uncorrelated in this hydrographically diverse area, thus we examine their effects in combination and separately. Cluster analyses and cumulative biomass size spectra reveal clear and significant responses to each separate habitat variable. When combined, habitat factors result in three distinct assemblages: (1) communities with a high proportion of biomass in small organisms, typical of shallow areas (<10 m) with coarse sediments (<10% fines) and low accumulation of organic material (<3.0 gC/m2/yr/δ15N); (2) communities with high proportion of biomass in the largest organisms found in the Strait, typical of deep, fine sediments with high modified organic flux (>3 g C/m2/yr/δ15N) from the Fraser River; and (3) communities with biomass dominated by moderately large organisms, but lacking the smallest and largest size classes, typical of deep, fine sediments experiencing low modified organic flux (<3.0 gC/m2/yr/δ15N). The remaining assemblages had intermediate habitat types and size structures. Sediment percent fines and flux appear to elicit threshold responses in size structure, whereas depth has the most linear influence on community size structure. The ecological implications of size structure in the Strait of Georgia relative to environmental conditions, secondary production and sediment bioturbation are discussed.

Functional diversity in three Mediterranean transitional water ecosystems

Biological trait analysis (BTA) is a method that describes ecological functioning of species assemblages incorporating information on species' distributions and their biological characteristics. In the present study, soft bottom communities of three Mediterranean coastal lagoons with different degree of salinity range were analyzed for seven biological traits (mobility, habitat, feeding type, habitat modification, body form, body size and feeding apparatus) in order to investigate the differences in communities' structure and functional diversity across a scale of natural stress. In more variable environments semi-mobile and epibenthic organisms prevailed, while predators were found under more stable conditions. Multivariate analyses using biological traits gave similar results with those obtained by the traditional analyses using species abundances; however, the distinction among lagoons was less evident, indicating that in transitional waters species can be different but their biological traits similar. This supports the idea of species redundancy in transitional water ecosystems.

Functional diversity and redundancy of soft bottom communities in brackish waters areas: Local vs regional effects

The present study aims to detect functional diversity as well as functional redundancy patterns of soft bottom benthic communities in relation to the prevailing environmental factors, across several brackish water areas. We further tested whether differences in spatial scale can account for the possible variability in functional trait distribution, as well as for the local community assembly processes driven by species functional traits. Our main results suggested that environmental variation induces a large amount of variability in functional trait distribution at local and regional scale, a result which underscores the importance of habitat and environmental variation in the functioning of soft sediments in brackish areas. Conversely to functional diversity, functional redundancy remained invariable in both local and regional scales, therefore acting as an insurance against the enhanced environmental variability and maintaining ecosystem processes and services. Our findings led us also to conclude that environmental factors control the distribution of certain functional traits thus acting as environmental filters, in both local and regional scales. On the other hand, dominant species interactions accounted for the reduced levels of functional divergence at the less confined brackish water areas. This finding supported the view that interactions among dominant species can potentially induce negative effects on the functionality of brackish water soft sediments. From all the above, it is reasonable to assume that community shaping and functioning of the examined brackish water areas are governed by both biotic interactions and environmental filters, which are acting simultaneously at varying degrees of influence.

Spatio-temporal biodiversity of soft bottom macrofaunal assemblages in shallow coastal waters exposed to episodic hypoxic events

The Humboldt Current System (HCS) has one of the three most important oxygen minimum zones (OMZ) of the global ocean. Several studies have looked at the macrofaunal benthic assemblages inhabiting the continental shelf and shallow bays off central-southern Chile associated with low oxygen areas, but little is known about open coast macrofaunal communities within this zone, which are frequently subjected to the low oxygen conditions of Equatorial Subsurface Waters (ESSW). In order to assess local and mesoscale coastal macrofauna dynamics, the sampling area (ca. 40 linear km) was divided into seven local zones (Cobquecura, southern Cobquecura, northern Itata, Itata River mouth, external, southern Itata, and Coliumo). Eight oceanographic cruises were carried out between May 2006 and February 2008 covering 16 coastal sampling sites, between 36°07’S and 36°30’S. The macrofaunal assemblage was dominated by polychaetes, crustaceans, and mollusks. Our results suggest a high degree of temporal faunal stability on the mesoscale in soft bottom communities along the open coast, given the persistence of a faunal assemblage dominated by organisms tolerant of low oxygen conditions. While there is some local variability in community attributes, the main structuring factor for soft bottom communities in the shallow coastal area off central-southern Chile is the seasonal intrusion of low oxygen ESSW.

Soft-bottom crustacean assemblages in Mediterranean marine caves: the cave of Cerro Gordo (Granada, Spain) as case study

Although marine caves are priority conservation areas according to the Directive 92/43/CEE of the European Community, there is a lack of studies dealing with their soft-bottom communities. For a case study, we selected the Cerro Gordo cave at 15 m depth. Three different zones were defined: a semi-dark 25-m long entrance area, a dark intermediate area of 35 m, and the final zone at 90 m from the entrance. Sediment samples were taken from these zones as well as from outside the cave (control) by SCUBA diving. Six rectangular cores of 10 × 250 cm2 were collected in each site for macrofaunal study, and three more replicates were taken to analyze physico-chemical parameters. The granulometry showed a clear gradient from medium sands outside the cave to silt and clay in the inner zone. Measurements of the crustacean assemblages showed that the number of species and abundance were significantly higher outside the cave (30–40 species, >4,000 ind m−2) than inside (5–10 species, <1,000 ind m−2). Multivariate analyses showed a clear difference in species composition between outside and inside the cave. Caprellids, tanaids, cumaceans, and decapods were only found outside the cave, while gammarids and isopods were present both outside and inside the cave. The gammarid Siphonoecetes sabatieri and the tanaid Apseudes latreilli were the dominant species outside the cave, while the gammarids Harpinia pectinata, Harpinia crenulata, and Harpinia ala were dominant inside. The present study represents an increase in depth range and geographic distribution for Kupellonura mediterranea and Monoculodes packardi. This is the first description of soft-bottom crustacean communities from submarine caves of southern Spain.

Effects of patch size and position above the substratum during early succession of subtidal soft-bottom communities

Early macrobenthos succession in small, disturbed patches on subtidal soft bottoms is facilitated by the arrival of post-larval colonizers, in particular by active and passive dispersers along the seafloor or through the water column. Using a field experiment at two contrasting sites (protected vs. exposed to wave action), we evaluated the role of (a) active and passive dispersal through the water column and (b) the influence of small-scale spatial variability during succession of subtidal macrobenthic communities in northern Chile. Containers of two sizes (surface area: small—0.12 m2 and large—0.28 m2) at two positions above the natural substratum (height: low—3 cm and high—26 cm) were filled with defaunated sediment, installed at two sandy sublittoral sites (7–9 m water depth) and sampled after 7, 15, 30, 60 and 90 days, together with the natural bottom sediment. The experiment took place during austral fall (from late March to early July 2010), when both larval and post-larval stages are abundant. At the exposed site, early succession was driven by similar proportions of active and passive dispersers. A sequence from early, late and reference communities was also evident, but container position and size affected the proportional abundance of dispersal types. At the protected site, the successional process started with abundant colonization of active dispersers, but toward the end of the experiment, the proportion of swimmer/crawlers increased, thus resembling the dispersal types found in the natural community. At this site, the position above the sediment affected the proportional abundance of dispersal types, but patch size had no effect. This study highlights that macrobenthic post-larvae can reach at least 26 cm high above the bottom (actively or passively, depending on site exposure), thus playing an important role during early succession of sublittoral soft bottoms. The active or passive use of the sediment–water interphase may also play an important role in the connectivity of benthic populations and in the recovery after large-scale disturbances of sublittoral habitats.

Predator-induced defenses in a salt-marsh gastropod

Predator-induced defenses are among the most ecologically important forms of phenotypic plasticity. Although predation and induced defenses are well documented in rocky-intertidal systems, they have received less attention in soft-bottom communities. Shell-crushing predators are common in soft-bottom, vegetated habitats, which often exhibit substantial spatial heterogeneity in predation intensity. We examined variations in shell morphology of the salt-marsh periwinkle, Littoraria irrorata, among marsh microhabitats in the northern Gulf of Mexico that vary in their accessibility to predatory blue crabs, Callinectes sapidus. Littoraria from high-predation sites exhibited more extensively calcified apertural lips and narrower apertural openings relative to snails from low-predation sites. Thick apertural lips generally increased the handling time required by Callinectes to breach Littoraria shells in laboratory experiments, although the method of shell entry used by crabs was dependent on the crab:snail size ratio. Apertural-lip thickness was not related to past predation events in field-collected snails. Snails exposed to water treated with the effluent of Callinectes and crushed conspecifics produced significantly thicker apertural lips than controls, with a response time and morphological extent comparable to that of their rocky-shore counterparts. This study underscores the widespread occurrence of predator-induced plasticity in marine gastropods and emphasizes its role in soft-bottom, vegetated marine habitats, where shell-crushing predation can be as prevalent a selective force as in the rocky intertidal.

Effects of thermal pollution on the soft-bottoms surrounding a power station in the Canary Islands (NE Atlantic ocean)

The spatial and temporal effects of hot seawater (60–70°C) from a power station on nearby soft-bottom communities were analyzed in the protected area “Sebadales del sur de Tenerife” (SE coast of Tenerife, Canary Islands, NE Atlantic Ocean). The samples were taken during summer 2003 and winter 2004 from 12 to 20 m depth. The highest macrofaunal abundance and species diversity were found in the turbines. A specific community, characterized by the polychaetes Aponuphis bilineata and sabellids of the genus Chone and the amphipod Photis longicaudata, inhabited the surroundings of the power station turbines. Permanent current from sea effluent had majok impact over the macrofaunal community structure of the neighbouring bottom where no measurable responses to thermal disturbance were detected.

Ecophysiological studies of the non-indigenous species Gracilaria vermiculophylla (Rhodophyta) and its abundance patterns in Ria de Aveiro lagoon, Portugal

Gracilaria vermiculophylla is the dominant macrophyte in the Ria de Aveiro lagoon, Portugal (40°38′N, 8°43′W), which is a highly urbanized estuary impacted by oyster cultivation and finfish aquaculture. This study aimed to understand the success of G. vermiculophylla in estuaries by monitoring its abundance and phenology throughout an annual cycle. This species thrives in soft-bottom communities, mostly entangled in the substrate amongst dead bivalve shells and tubes of the polychaete Diopatra neopolitana but it may be also found free-floating; it is present year-round. Carposporophytes were found throughout the year and at all sampling locations. The life history of this taxon was completed in the laboratory. Spore germination and growth success were investigated in a fully factorial designed array of temperatures (5, 10, 15, 20 and 25°C), photoperiods (8, 12 and 16 h day-lengths) and photon flux densities (40 and 100 µmol photons m−2 s−1). Germination occurred under all conditions, being highest at 20°C under the long day treatment. Germination was lowest at 5°C, with no spore survival. The growth rates of the sporelings were affected by the interaction of the three factors tested. These were minimal at 10°C (2.21% ± 1.14 in 8-h days for tetrasporophytes and 2.60% ± 0.57 in 12-h days for gametophytes) and maximal at 20°C and long day treatments for both gametophyte and tetrasporophyte phases (9.96% ± 0.62 and 16.86% ± 0.73, respectively). No differences were found in the growth rates of the mature haploid or diploid phases. Gracilaria vermiculophylla is reproductive throughout the year. It attains high rates of germination and growth success under a wide range of environmental conditions. With such broad tolerances to environmental factors, G. vermiculophylla has a high invasive potential, which helps to explain its current dominance in the Ria de Aveiro lagoon.

Testing MEDOCC and BOPA indices in shallow soft-bottom communities in the Spanish Mediterranean coastal waters

Abstract The implementation of the European Water Framework Directive has enhanced the development of several indices based on benthic invertebrate communities. Some of them, such as BOPA, simplify the calculation employing the taxonomic sufficiency principle to assess the ecological status of ecosystems since they only consider opportunistic polychaetes and amphipods; others, such as MEDOCC, include all the species found in the community, and assign them to four ecological groups: sensitive, indifferent, tolerant, and opportunistic. Anyway, there is the need for testing, validating and improving these indices in different regions and communities. In this study we test the application of MEDOCC and BOPA along the Spanish Mediterranean coastal waters (Catalonia, Balearic Islands, Valencia, Murcia, and Andalusia regions) in order to investigate whether benthic indices with different taxonomic resolution provide similar ecological status assessment. Shallow fine soft-bottom communities were sampled from 2002 to 2010 in a total of 241 locations. The comparison between both indices demonstrated that the concordance for the studied communities reached up to 79% in some areas, although it was less than 30% in natural and anthropogenically modified ecosystems dominated by stress-tolerant species. Even though BOPA index provides good results, in general it evaluates in higher ecological status than MEDOCC does and it does not always allow discriminating more disturbed situations. The assignation of a same species to different ecological groups (some opportunistic polychaetes of one method are classified as indifferent by the other) and the fact that all the amphipods (except genus Jassa) are considered as sensitive species in BOPA index but not in MEDOCC, could contribute to the observed discrepancies. Some suggestions to improve the agreement between both methods are pointed and discussed.

Gradient effects on structuring of soft-bottom benthic infauna: Macoma balthica and predation, recruitment, and food availability

Infaunal benthic community structure can be affected by factors that operate locally (e.g., predation, competition, and disturbance) and regionally (e.g., recruitment, nutrient delivery). To determine the mechanisms driving distribution of a dominant infaunal clam, Macoma balthica, along a salinity (i.e., stress) gradient in the York River, Chesapeake Bay, I experimentally examined the effects of predation, recruitment, and food availability in shallow, subtidal, soft-bottom habitats. Specifically, in upriver and downriver zones I quantified: (1) the abundance of M. balthica; (2) the effect of predation on survival of M. balthica; (3) the abundance and foraging efficiency of major epibenthic predators; (4) the recruitment of M. balthica; and (5) the food availability for clams (sedimentary carbon). Consumer stress models predict that predators are more stressed in zones where salinity is lower and more variable (i.e., upriver); thus, predator-induced mortality should be lower upriver, potentially elevating the density of infaunal prey. In contrast to these models, in the York River, (1) natural abundance of M. balthica was higher upriver, (2) both predation-induced mortality in manipulative field experiments as well as field measurements of natural mortality of clams over time were higher upriver, though per capita foraging efficiency was lower, (3) predator abundance but not size was greater upriver where predation intensity was higher, (4) recruitment was lower upriver, and (5) food availability (sedimentary carbon) was greater upriver. Clam density, environmental stress, and per capita foraging efficiency were in accord with a consumer stress model of community regulation, whereas higher predator abundance and predation intensity in zones of higher environmental stress were contrary to the model's predictions. Recruitment did not dictate overall patterns of clam abundance, but habitat quality and nutrients appeared to drive prey and predator abundances. The patterns in this soft-bottom community are explained best by a productivity model, as reflected in a community governed principally by resource availability (i.e., bottom–up control), at a broad scale. This research suggests that structuring forces are similar for rocky intertidal, salt marsh, and soft-bottom communities at broad spatial scales.

Rapid macrofaunal colonization of water-based drill cuttings on different sediments

A field experiment was conducted to investigate how water-based drill cuttings and sediment type influence colonization of soft bottom communities. Bottom frames with trays containing defaunated sediments were placed at the seabed for 6months to study colonization of macrofauna. Two different sediments (coarse and fine) were used, and 6 or 24mm layer of water-based drill cuttings were added on top of these sediments. Some of the sediments were controls with no additions. In the end of the experiment, the oxygen availability in sediment porewater and macrofaunal abundance were reduced in treatments with 24mm drill cuttings compared to controls. Tube-building annelids were particularly sensitive to drill cuttings. However, these responses were only minor, and notably, the drill cuttings initiated a weaker faunal response than sediment type and site of the bottom frame. Sediments capped with water-based drill cuttings thus showed a rapid colonization of macrofaunal communities.

Brachyuran crabs of the family Macrophthalmidae Dana, 1851 (Decapoda: Brachyura: Macrophthalmidae) of the Persian Gulf

The family Macrophthalmidae Dana, 1851, is one of the best represented brachyuran groups in intertidal habitats in the Persian Gulf. Nine species from two subfamilies are reported from the gulf and the adjacent Gulf of Oman, mainly inhabiting intertidal soft substrates. The subfamily Ilyograpsinae Števcic, 2005, is represented by Ilyograpsus rhizophorae Barnard, 1950, erroneously recorded as I. paludicola (Rathbun, 1909). Eight species of the subfamily Macrophthalminae Dana, 1851, have been recorded from the area, all belonging to Macrophthalmus Desmarest, 1823. Of these, M. sinuspersici Naderloo &amp; Türkay, 2010, has recently been described and is the only species of the genus occurring on rocky shores. Macrophthalmus graeffei A. Milne-Edwards, 1873, occurs in subtidal water and is hereby recorded for the first time from the northern Indian Ocean. The remaining six species, M. dentipes Lucas, 1836, M. depressus Rüppell, 1830, M. grandidieri A. Milne-Edwards, 1867, M. laevis A. Milne-Edwards, 1867, M. serenei Takeda &amp; Komai, 1991, and M. sulcatus H. Milne-Edwards, 1852, are important elements of the intertidal soft bottom communities. An identification key for the genus Macrophthalmus in the area is provided, and the geographical distribution of the family is briefly discussed.

Assessing reliable indicators to sewage pollution in coastal soft-bottom communities

Physicochemical characteristics of sediment and benthic communities were studied in the proximity of seven sewage outfalls with differences in flow and wastewater treatment in the Western Mediterranean Sea. Redox potential was the only abiotic parameter which showed a pattern related with distance to outfalls, whereas granulometry, percentage of organic matter, metal concentrations or pH did not show changes related with outfall presence. Benthic community analysis proved to be the most suitable monitoring tool. The results showed that the highest impacted stations corresponded with those closest to outfall with the highest flow and only pre-treatment, whilst a decrease of this tendency was detected in the locations where secondary treatment takes place. Meta-analysis showed a decrease of amphipods and tanaids abundance as well as redox potential, as the indicators with the clearest response to sewage presence.

Response of different benthic indices to diverse human pressures

The interest in benthic indicators for soft-bottom marine communities has dramatically increased after a rather long period of relative stagnation due to the need for new tools to assess the status of marine waters, called for by the Clean Water Act and the Water Framework Directive. Our expertise on benthic communities has permitted us to gather a vast amount of data from diverse water bodies under unpolluted and polluted conditions (e.g., accidental oil spill, sewage, long-term anthropogenic estuarine constraints) in tidal estuaries, harbours, and on the coastal shelf from Atlantic Ocean and Mediterranean Sea. We compared the results of four biotic indices on the various available datasets: Shannon-Wiener H′ diversity, AMBI and BO2A, which divide the species into Ecological Groups, and ITI, which divides the species into trophic groups, and the agreement of Best Professional Judgement (BPJ) on the assessment of ecological conditions. Benthic indicators as “ sentinel species”, which is a particular species that by its presence or its relative abundance warns of possible unbalances in the surrounding environment or distortions in community functions, was also tested. Indicators, BPJ and opportunist sentinel species gave similar ECoQS for the different sampling sites. We discuss the use of Biological Indicators as ‘objective’ or ‘subjective’ alternatives for assessing soft-bottom communities, and propose to employ simple methods such as BPJ and taxonomy sufficiency in such diagnostic approaches.

A new echinoderm Lagerstätte from the Pliensbachian (Early Jurassic) of the French Ardennes

A succession of clays with thin shell beds from the French Ardennes, dated to the late Early Pliensbachian Davoei Zone and yielding abundant well-preserved remains of all five extant classes of echinoderms, is described here as a new Lagerstatte. The echinoderms occur in the form of isolated ossicles, semi-articulated plate aggregates and abundant intact skeletons with even the most delicate appendices preserved in place and the finest skeletal structures hardly blurred by recrystallisation. The outstandingly good preservation of the echinoderm specimens allows for a morphological assessment of the represented taxa in detail only rarely achievable by fossil material. The material described herein thus significantly contributes to a better understanding of the systematic position and phylogenetic background of many Early Jurassic echinoderm taxa. The echinoderms are considered to have been buried as an autochthonous or at least parautochthonous assemblage among clumps and beds of Modiolus bivalves. The depositional setting most likely represented a relatively shallow, near-shore soft-bottom environment in which conditions repeatedly favoured the settlement and subsequent effective burial of bivalve-echinoderm assemblages, leading to the formation of the thin highly fossiliferous shell beds intercalating the otherwise nearly sterile clays. The new Lagerstatte opens a unique window into the palaeoecology of an extinct shallow-water soft-bottom community closely comparable to recent analogues.

Macro benthic community assemblage before and after the 2007 tsunami and earthquake at Paracas Bay, Peru

Macrobenthic soft bottom community assemblages were studied from December 2006 to December 2007 at Paracas Bay (Atenas Beach, 13°45' S, 76°17' W, Peru), including the period of the tsunami of 15 August 2007, providing a unique opportunity to assess the effects of this type of natural disturbance in soft bottom marine ecosystems. The results show that the tsunami affected the soft bottom community assemblage by changing the sediment granulometry, the biomass and abundance of epifaunal species, and by increasing the silt proportion. The event affected all functional groups, resulting in an increased numbers and biomass of filter feeder and grazers that were followed soon after by predators during the post-tsunami period. A similar pattern was observed for biomass and the abundance of infaunal species without changing the functional groups. The slow recovery observed after four months was likely related to the loss of sediment stability. In summary, there were differences in the structure and composition of soft bottom macrofaunal assemblages before and after the earthquake and posterior tsunami disturbance, forcing benthic communities to initiate re-colonisation processes.

Ecological Quality Status of the soft-bottom communities on the algerian coast: General patterns and diagnosis

Between 1995 and 2001, the soft-bottom communities along the 1180km of the Algerian coast were sampled in nine gulfs and 12 harbours, providing a total of 655 samples. Eight macrozoobenthos-based biotic indices (S, N, H′, BQI, AMBI, BENTIX, BO2A and ITI) were selected to describe the general patterns of the coastal water quality status and to establish a quality diagnosis for the different zones subjected to anthropogenic pressure (e.g., harbour construction, industrial and urban pollution). Reference values were determined for each of the eight indices selected by analyzing the indices’ parameter distribution. The Ecological Quality Ratio (EQR) was estimated for each index, resulting in an EQR Mean Score and an EQR Bad Score. From these EQR, we defined an EQS for each sample. The agreement between these EQS was analysed using the Kappa method in order to propose a survey strategy for the Algerian coastal waters that would take into account the soft-bottom biological compartment. The results clearly indicate that high and good quality assessments are prevalent in the gulfs, while quality assessments in harbours vary greatly from bad to good. The effect of pollution observed in the harbours can be classified in two main groups, according to when they were constructed and their relative degree of openness to the sea, which permits better water circulation and probably dilutes the pollution.

Effects of two offshore gas platforms on soft-bottom benthic communities (northwestern Adriatic Sea, Italy)

The macrozoobenthos living around two offshore gas platforms, Barbara NW (pB) and Calipso (pC) located in the northwestern Adriatic Sea were investigated for three years after their construction to detect eventual effects due to the platforms. The sampling stations were spaced at increasing distance from the platforms up to 1000 m. Both multivariate and univariate analysis showed an initial defaunation (short-term effect) at pB and within a 120 m radius at pC. A general recovery in terms of abundance, species richness and diversity was observed for the benthic communities after one year. During the third monitoring year a mussel mound developed at both the platforms (longer-term effect) extending up to 30 m from pC, whereas similar soft-bottom communities were found at all the other distances. The geographical position plays an important role in the “timing” of the above effects. Moreover, despite the different environmental features, a 3-year monitoring plan can be effective to evaluate the potential impact on benthic communities of offshore gas platforms in the north-central Adriatic Sea.

Studies on impact of the alien Red King Crab (Paralithodes camtschaticus) on the shallow water benthic communities of the Barents Sea

Summary The red king crab Paralithodes camtschaticus (Tilesius, 1815) was introduced in the Barents Sea from the North Pacific in 1961–1969 to establish a fishery. Currently the crab inhabits an area from Kolguyev Island in the east to Soroya in the west, and the total number of adults exceeds 40 million. The crab is a large generalist predator, so its potential impact on native bottom communities is expected to be high. The goal of this study was to review our publications related to the possible impact of the red king crab on the shallow water benthic communities of the Kola Peninsula inlets. First, we reviewed field and experimental data on feeding ecology of different size groups of the crab. Secondly, we examined the data on the benthic communities’ structure in the bays. Finally, assess possible changes in the community structure caused by the red king crab predation. The crab diet includes about 100 species of invertebrates, algae, and fish remnants. Diet of juveniles varied in three studied areas, but bivalve and gastropod mollusks dominated. Experiments on the juvenile feeding showed their positive selection for ophiuroids. Caught prey was usually not completely consumed. Food losses decreased from 50 to 60% in crabs with 35–40 mm carapace width (CW) to 25% in crabs with 70–80 mm CW. Within and between bays trends in the benthic community structure related to the crab density were revealed. Generally, proportion of the stations with disturbed community structure decreased eastward from 80% in the Kola Bay to 18% in the Dolgaja Bay and it was negligible in the Dal’nezelenzkaja Bay. This pattern coincides with the juvenile crab density decreasing eastward. On a smaller scale in the Kola Bay we observed a negative correlation between biomass of macrozoobenthos and juvenile crab density, which was likely related to the crab predation. Comparison of the new data obtained in 2006 with the detailed survey of soft bottom macrobenthos conducted in 1990 in Dolgaja Bay showed a decrease of the diversity of soft bottom communities as well as in species richness, density and biomass of bivalves. Our data demonstrate that the proposed impact of the crab on the bottom communities of the Barents Sea is not as dramatic as have been expected from its high feeding activity and wide diet. We hypothesize that the crab omnivory distributes its predation pressure among various groups of organisms and prevents elimination of particular species or taxa.