Dominant Polychaete Research Articles

Species characterization of soft bottom habitats by depth and sediment particle size on the Catalan coast (NW Mediterranean): unexpected species composition of the assemblages

The aim of the study is to describe the macrofaunal composition of marine soft bottom habitats on the Catalan coast between a depth of 3 and 35 meters, considering all groups of macroinvertebrates. The study also aims to compare our data with previous studies focused on the NW Mediterranean and to define the variables that drive assemblage composition. Depending on the species composition and the structure of the assemblages, six different habitats, mainly defined by depth and sediment granulometry, are described. Shallow (<20 m) and deep (>20 m) habitats are easily distinguished and are subdivided in three habitats each: (1) very coarse and coarse sediments (coarse sediments); (2) medium, fine and very fine sands (fine sediments); and (3) muddy sediments. Fine sediments in both shallow and deep waters have emerged as the most common and extensive habitats along the coast up to a depth of 35 meters. Neither coarse nor muddy habitats are frequent. The characterization of shallow habitats produced some unexpected results with respect to previous studies: Spisula subtruncata and Lucinella divaricata were dominant, while neither Ditrupa arietina nor Owenia fusiformis, previously mentioned as dominant polychaetes in shallow fine sand habitats, were common. Polychaetes were, in general, the dominant group (both in species richness and abundance) in the six habitats, except in shallow fine sediments, which were dominated by mollusks. The study is a benchmark for future monitoring of soft bottom habitats on the Catalan coast to a depth of 35 meters.

Benthic Community Assessment of Commercial Oyster (Crassostrea virginica) Gear in Delaware Inland Bays

Oyster aquaculture is one of several methods for the restoration of Delaware Inland Bays; however, little is known about its potential impacts on the benthic community of the bays. In this study, water quality parameters were measured and polychaetes were collected from 24 sampling locations at Rehoboth, Indian River, and Little Assawoman Bays from July to October 2016 and 2017. We aimed to assess the impact of Eastern oyster farming under different stocking densities (50 and 250 oysters/gear) and distances away from the sites where the off-bottom gears are implemented (under gears, one meter, and five meters away). No significant impact was detected on polychaetes’ abundance and richness in regard to the presence of oyster gears. The number of polychaetes and species richness was significantly higher in Little Assawoman Bay in comparison to the Indian River and Rehoboth Bays. Results showed that the Ulva lactuca bloom that happened in 2016 could negatively impact the low abundance and richness observed in the polychaetes community. Similarly, the values of polychaetes abundance and species richness did not change significantly in samples that were taken far from the oyster gears. Dominant polychaetes families were Capitellidae and Glyceridae contributing to more than 70% of polychaetes’ number of individuals. Our results help to understand the role of oyster aquaculture in restoring the viability in the natural habitat of the Delaware Inland Bays.

Polychaete Diversity Related to Different Mesophotic Bioconstructions along the Southeastern Italian Coast

In the different mesophotic bioconstructions recently found along the Southeastern Italian coast, polychaetes have been proved to show high species richness and diversity, hitherto never investigated. In the present study, the species composition and functional role of polychaete assemblages were analysed; the updated key to identification of the Mediterranean species of genus Eunice was presented and some taxonomic issues were also discussed. On the total of 70 species Serpulidae and Eunicida were the dominant polychaetes. Facing similar levels of α-diversity, the polychaete assemblages showed a high turnover of species along the north-south gradient, clearly according to the current circulation pattern, as well as to the different bioconstructors as biological determinants. Indeed, Serpulidae were dominant on the mesophotic bioconstructions primarily formed by the deep-sea oyster Neopycnodonte cochlear, while the Eunicida prevailed on the mesophotic bioconstructions mainly built by scleractinians. Lastly, the record of Eunice dubitata was the first for the Mediterranean and Italian fauna and proved this species to be characteristic of mesophotic bioconstructions.

First record of the rare deep-sea polychaete Rhamphobrachium (Rhamphobrachium) agassizii (Annelida: Onuphidae) in European waters

AbstractRhamphobrachium (Rhamphobrachium) agassizii is reported from the Cantabrian Sea, Spain, from depths of 925–1207 m. This is its first record off the Iberian Peninsula and in European waters, representing its northernmost distribution in the North Atlantic Ocean to date. Previous reports of R. (R.) agassizii from the eastern and western North Atlantic demonstrate its apparent amphi-Atlantic distribution, which appears consistent with the distribution of the main Atlantic currents. It is a typical deep-water species with its deepest record at 2165 m from the Azores archipelago. The specimens were collected singly at two stations, attesting to the rarity of the species in contrast to its congener R. (Spinigerium) brevibrachiatum which was the most dominant polychaete species in a previous study.

Response of benthic macrofauna to multiple anthropogenic pressures in the shallow coastal zone south of Sfax (Tunisia, central Mediterranean Sea)

Anthropogenic activities including coastal industries, urbanization, extensive agriculture and aquaculture as well as their cumulative impacts represent major sources of perturbation of marine coastal systems. Macrobenthic communities are useful ecological indicators for monitoring the health status of marine environments (or polluted environments). The present study reports, for the first time, the response of benthic macrofauna sampled during two years survey (2015–2016) to multiple anthropogenic pressures on the coastal zone south of Sfax (Tunisia). A total of 12 stations were monitored seasonally at locations downstream from the main potential sources of disturbance. 106 macrobenthos taxa, belonging to six animal phyla and 70 families, were identified with a dominance of polychaetes (42%), crustaceans (35%) and molluscs (18%). We used an ANOVA test and cluster analysis to identify spatial gradient linked to environmental and anthropogenic factors, including depth, sedimentary texture and anthropogenic activities (i.e. phosphogypsum discharges).The macrofauna present lowest species number and abundance on stations undergoing anthropogenic inputs, which are extremely polluted by heavy metals (Cd, Cu, F and N) and excess of organic matter. Univariate parameters reveal a general trend of increasing species diversity with increasing distance from the pollution source. The polluted stations are strongly dominated by carnivores, and selective deposit feeders, and more closely linked to the availability of trophic resources than to anthropogenic constraints. The seasonal changes in macrobenthic abundance, diversity indices and community structure are mainly linked to the biological cycle (e.g. recruitment events) of the dominant species. Biotic indices (AMBI and BO2A) classified the coastal zone south of Sfax as moderate and good ecological status. This study suggests that initiating a long-term monitoring programme would improve our understanding of the temporal changes of macrobenthic communities of this ecosystem, contributing to the assessment of effective management and conservation measures in this disturbed area.

Structure of the benthic macrofauna of an anthropogenic influenced area: Skhira Bay (Gulf of Gabès, central Mediterranean Sea).

Skhira Bay located in the Gulf of Gabès, on the southeastern coast of Tunisia, is an important area in terms of its dense vegetation coverage, wide continental shelf, and fisheries resources. However, this area with a typically micro-tidal range is subject to intensive anthropogenic pressures: soft bottom trawling, chemical pollution from phosphoric acid production, and shipping activity. The present study is the first investigation of the structure of the benthic macrofauna on this part of the Tunisian coast. In April 2010, 28 stations were sampled along four transects from the phosphogypsum outfall on an inshore-offshore gradient. A total of 239 macrobenthos taxa, belonging to nine zoological groups and 140 families, were identified with a dominance of polychaetes (33.5%), crustaceans (29.4%), and mollusks (19.6%). Results show that the stations facing the phosphogypsum discharges are the most disturbed and characterized by a poorly diversified macrofauna. The macrofauna is dominated by carnivores, suspension feeders, and selective deposit feeders, and seems to be linked more to the availability of trophic resources than to disturbance. Four benthic assemblages are identified using Cluster and MDS analyses linked to edaphic factors, such as sediment structure, organic matter content, inshore/offshore gradient, and the proximity of the phosphogypsum outfall. The biotic indices (AMBI and BO2A) calculated from macrofauna data show that the ecological status of Skhira Bay varies overall from moderate to good. This study suggests initiating a long-term monitoring program to improve our understanding of the temporal changes of this ecosystem, to recommend the necessary conservation measures in this area of high-value natural heritage.

Cyclical Events in the Life and Death of an Ephemeral Polychaete Reef on a Tropical Mudflat

The polychaete (sabellariid-spionid) reefs at Jeram shore (Malaysia) grow up on soft-bottom mudflats and appear short-lived. It is postulated that such reef building results from the succession of polychaete species in response to the changing environment modulated by the extreme hydrometeorological events. To elucidate the biological succession of the reef cycle in relation to the environment, two reef patches on the intertidal mudflat were studied, both spatially (horizontal and vertical community structure) and temporally (June 2012 to January 2014). The Jeram polychaete reef cycles through four phases within a year: pre-settlement phase (March–May), growth phase comprising primary (May–November) and secondary (October–January) successional stages, stagnation phase (December–January), and destruction phase (January–March). The reef dynamics appear to be linked to the regional monsoon climate and local hydrological conditions. At the onset of the southwest monsoon (May), strong erosive forces initiate the reef’s primary succession of the growth phase where the dominant polychaete Sabellaria jeramae colonize and rapidly grow on the exposed lag deposits of shells. During the northeast monsoon (November–March), stronger depositional forces cover the developed reef with fine sediments that are colonized by another polychaete, the spionid Polydora cavitensis during the reef’s secondary succession of the growth phase. On the muddy substrate surrounding the reef clumps, mudflat polychaetes were the most abundant macrobenthos followed by anomurans, gastropods, carideans, and brachyurans. However, these mudflat macrobenthos play no obvious or direct role in initiating the growth of the reef which is likely the result of settlement of dispersed polychaete larvae from unknown offshore reefs. On the other hand, the reef presence has a positive effect on the presence or abundance of surrounding mudflat macrobenthos such as mudflat polychaetes, shrimps, crabs, and gastropods.

Effects of sedimentary sulfide on community structure, population dynamics, and colonization depth of macrozoobenthos in organic-rich estuarine sediments

An annual field survey and in situ recolonization experiment revealed the effects of sedimentary sulfide (H2S) on macrozoobenthos in a eutrophic brackish lagoon. Species diversity was much lower throughout the year in muddy opportunist-dominant sulfidic areas. Mass mortality occurred during warmer months under elevated H2S levels. An enclosure experiment demonstrated that sedimentary H2S modified community composition, size structure, and colonization depth of macrozoobenthos. Species-specific responses to each sediment type (sand, sulfidic mud, and mud with H2S removed) resulted in changes in the established community structure. Dominant polychaetes (Hediste spp., Pseudopolydora spp., and Capitella teleta) occurred predominantly in a thin surface layer in the presence of H2S. On the other hand, organic-rich mud facilitated settlement of polychaete larvae if it does not contain H2S. These results demonstrate that sediment characteristics, including H2S level and organic content, were key structuring factors for the macrozoobenthic assemblage in organically polluted estuarine sediments.

Evaluation of changes in macrobenthic standing stock and polychaete community structure along the south eastern Arabian Sea shelf during the monsoon trawl-ban

The south eastern Arabian Sea is characterized by moderate coastal upwelling, high biological production and subsurface oxygen depletion during the southwest monsoon (June–September). Concurrently, a seasonal closure to trawling activities (15th June–31st July) is implemented here, as a sustainable ecosystem management practise. The effects of monsoon driven environmental changes and consequences of trawling cessation on macrofauna were assessed, based on surveys at 12 sites (30–200m) preceding and during different phases of the southwest monsoon. Macrofaunal density and biomass increased considerably towards the mid and late monsoon along the inner shelf (30–50m) where trawling is intense, while no temporal changes were observed along the outer shelf (100–200m). Density increased four-folds at the 30m contour and three-folds at 50m, while biomass nearly doubled at both depths, reflecting a marked increase in density of polychaetes (61–87% of macrofauna). The disproportionate increase in faunal density and biomass along the inner shelf (30–50m) was due to abundance of juvenile polychaetes and dominance of small-sized opportunists towards late monsoon (August–September). A concurrent hike in nominal species count of polychaetes was also observed in the study area. The increase in polychaete standing stock and high density of planktonic larvae during onset and peak monsoon, coupled with occurrence of juveniles as well as gamete-bearing adults in sediments, indicates that the southwest monsoon is a peak breeding season for the dominant polychaetes in the region. The trawl-ban during this period facilitates the recoupment of benthos by maximising spawning success and larval settlement, thereby enhancing overall ecosystem integrity.

Macrofaunal abundance and community composition at lower bathyal depths in different branches of the Whittard Canyon and on the adjacent slope (3500 m; NE Atlantic)

We studied benthic macrofaunal abundance and community composition in replicate Megacorer samples obtained from three sites in different branches of the Whittard Canyon (NE Atlantic) and one site on the adjacent slope to the west of the canyon system. All sites were located at a depth of ~3500m. Abundance (macrobenthos sensu stricto, >300μm) varied significantly (p<0.001) among sites, and decreased from east to west; highest in the Eastern branch (6249±standard deviation 1363ind.m−2) and lowest on the slope (2744±SD 269ind.m−2). Polychaetes were the dominant taxon, making up 53% of the macrofauna, followed by isopods (11%), tanaids (10%), bivalves (7%) and sipunculans (7%). Among the polychaetes, the Amphinomidae was the dominant family (27%), followed by the Spionidae (22%). Assemblage composition changed across the sites. From east to west, the proportion of polychaetes and isopods decreased (by 6% in each case), while sipunculans and tanaids increased (by 13% and 8%, respectively). The ranking of the two dominant polychaete families reversed from east to west (Eastern branch—Amphinomidae 36%, Spionidae 21%; Slope—Spionidae 30%, Amphinomidae 10%). Ordination of faunal groups (macrofaunal higher taxa, and polychaete families) revealed that the Central and Eastern branches were substantially similar, while the Western branch and slope sites were relatively distinct. A very similar pattern was evident in a corresponding ordination of environmental variables across the sites. An analysis of faunal similarities (ANOSIM) indicated that the Western branch/slope and Central branch/Eastern branch groups displayed the highest similarity. The clearest separation was between the slope and the Eastern branch. We conclude that, when compared at the same water depth, macrofaunal abundance and composition varies between open slope and canyon location, as well as among canyon branches. These differences probably reflect the influence of organic enrichment together with hydrodynamic activity, both of which are influenced by the topographic profile of individual canyon branches.

Comparative study of sediment particle mixing in a Zostera noltei meadow and a bare sediment mudflat

Seasonal changes in sediment particle mixing, surface sediment and seagrass charac teristics, and benthic infaunal composition were measured in Arcachon Bay (France), within both a well-developed Zostera noltei meadow and a bare sediment mudflat. Sediment par- ticle mixing intensities (measured by the normal biodiffusion coefficient Db N ) were obtained by fitting a continuous time random walk model to in situ measured vertical luminophore profiles. Db N values (mean ± SD) were between 2.99 ± 2.75 and 22.45 ± 43.73 cm 2 yr −1 within the bare mud- flat and between 0.39 ± 0.30 and 18.07 ± 18.14 cm 2 yr −1 within the Zostera meadow. Spatiotempo- ral changes in infauna and Db N were lower within the Zostera meadow, which supports the buffer- ing effects of seagrass meadows on biological sedimentary processes. Within the Zostera meadow, root biomass declined during the survey, in correlation with increases in (1) the mean value and the variability of Db N and (2) the spatial variability of infaunal composition with a decrease in the dominant polychaete Melinna palmata. At this station, similarity matrices of mean Db N and abun- dances of a set of 3 infaunal species (including M. palmata) correlated significantly, which further supports the key role of this species in controlling sediment particle mixing through sediment stabilization. When considering the whole data set, the similarity matrices of the coefficients of variation of Db N and of the abundances of a set of 5 species (Abra segmentum, Glycera convoluta, Tubificoides benedii, Heteromastus filiformis, Ruditapes phillipinarum) correlated significantly, which supports the suspected role of these species in controlling sediment particle mixing.

Distribution and seasonal abundance of Polygordius spp. (Class: Polychaeta; Family: Polygordiidae) exo- and endolarvae in the southern Mid-Atlantic Bight, USA

The importance life history plays in understanding population dynamics and the functional roles of species for predicting climate change scenarios are well established. Yet, in the marine environment, the complete life history is unknown for many species, especially the link between morphologically and ecologically distinct planktonic larvae, and their corresponding benthic adult forms. Integration of meroplankton abundance, benthic adult species, larval morphology, and molecular data was employed to unravel the complete life history of Polygordius, a dominant polychaete in sandy shelf sediments of the Mid-Atlantic Bight. Polygordius species are unusual, having two distinct planktonic larval forms: an exolarva and an endolarva. Extensive sampling in the southern Mid-Atlantic Bight with careful preservation of meroplankton (2006–2007) revealed the identity of multiple stages of exo- and endolarvae, and their spatial, seasonal, and vertical distribution. Molecular and morphological evidence indicated exolarvae are Polygordius jouinae and endolarva are an undescribed species. Structure and development of these larvae differed greatly. P. jouinae exolarvae were found off Delaware Bay to North Carolina. At some stations, they were abundant, with densities up to 4,013 m−3, comprising >90 % of the total meroplankton. Exolarvae spent up to a month in the plankton starting in March/May depending on year, settlement began in July when larvae were at least 2 mm in length, and by October were no longer observed in the plankton. These findings are consistent with the distribution patterns and life cycle known for adults. This is the first report of endolarvae north of Cape Hatteras.

Use of benthic polychaetes to assess anthropogenic impacts in the southern Saudi Arabian Red Sea Coast (LB485)

Use of benthic polychaetes to assess anthropogenic impacts in the southern Saudi Arabian Red Sea Coast SALEH A. AL FARRAJ This paper studied the polychaete community structures and their response to anthropogenic impacts in the southern Saudi Arabian Red Sea Coast. Samples were collected from four stations, i.e. Jazan Port, Fisherman’s Port, Corniche North Park and Al Qunfudah, along the southern Saudi Arabian Red Sea Coast for benthic polychaetes and environmental variables during July 2012. A total of 75 polychaete taxa were identifi ed from the study area. Spatial trends showed Jazan Port and Fisherman’s Port to have low species abundance, richness and diversity compared to the reference site (Al Qunfudah). Species richness, abundance and diversity were intermediate at Corniche North Park The reference station had the highest species richness, species diversity and evenness with the following dominant polychaete species: Owenia fusiformis, Pista macrolobata, Euclymene africana, Maldane sarsi and Syllis gracilis. Capitella capitata, Cirratulus cirratus and Heteromastides bifi dus were most abundant at Fisherman’s Port and Jazan Port. The study revealed that polychaetes of the southern Saudi Arabian Red Sea Coast are sensitive to various types of pollution. The data obtained serve as a baseline against which data obtained on subsequent monitoring can be compared. It is recommended that relevant authorities should carry out a continual assessment on the levels of pollutants in the studied area.Grant Funding Source: king saud university

Distribution and Diversity of Intertidal Macrofauna of Dharmadam Beach, South West Coast of India

This contribution presents the abundance and diversity of macrofauna in the pristine intertidal regions of Dharmadam beach along the Kerala coast (South West coast of India) during August 2009 to January 2011.The width of the beach is 15-30m, which alternates according to the tidal height. Environmental parameters like salinity, nutrients, conductivity and total dissolved salts analyzed exhibited significant correlation with macrofauna that dwells in the habitat. Gastropods (45.54%), polychaetes (10%), tanaids (43.4%) dominated in the present study. The monthly variations in abundance were displayed by dominant faunal species in various stations but did not show any seasonal variations except that of Emerita holthuisi , which was observed only in pre monsoon (Feb-May) and monsoon (Jun-Sep) months. Analysis of community indices showed monthly variations in species diversity. The peak mean species diversity was observed in station 1 in May, 2009 and Station 2 in December, 2009 and January, 2010.The spatial distribution of some organisms were not even in the study area. The sparse distribution, low richness and higher dominance of organisms were the characteristic feature of community structure. The dissimilarity trend of organisms like polychaetes, gastropods and total groups were discernible by MDS plotting. It best explained the dominance of polychaetes and gastropods on the beach. Assessing the correlation of water quality parameters to the fauna residing in study area BEST (Bio-Env + Stepwise) analysis was done and salinity showed more significance towards fauna. Draftsman plot were also done to observe the interactions of organisms. The highest correlation has been showed by barnacles and gastropods (0.825).The present study discussed the interaction of organisms in the selected habitat with environmental factors prevailing there along with the diversity and abundance.

Is nematode colonisation in the presence of Scolelepis in tropical sandy-beach sediment similar to the colonisation process in temperate sandy beaches?

The role of a dominant macrobenthic polychaete, Scolelepis squamata, in the colonisation of defaunated tropical sediments by sandy-beach nematodes was investigated and compared with a previous colonisation experiment carried out on a temperate sandy beach. Experimental cylinders, equipped with lateral windows allowing infaunal colonisation, were filled with defaunated sediment containing two treatments, with and without S. squamata. These cylinders were inserted into microcosms containing sediment with indigenous meiofauna collected from the field. The treatments were incubated in the laboratory at ambient temperature and salinity for 7, 14 and 21 days. The nematode assemblages in both treatments did not differ in composition between treatments and from the natural assemblages, suggesting that all the species were equally able to colonise the experimental cores. The presence of the polychaete did not affect the development of the nematode community composition, in contrast to the results from a previous temperate-beach experiment. However, our results did not indicate whether the difference in results was caused by the different behaviour of the polychaete specimens, or by the different composition and response of the present nematode community.

多毛类底栖动物在莱州湾生态环境评价中的应用

Polychaete,often linked in the past to the concept of opportunistic species able to proliferate after an increase in the quantity of organic matter,have played an especially important role in impacted soft-bottom habitats.They are frequently used as a biological indicator of environmental disturbance.The polychaete at 20 sampling sites in Laizhou Bay were investigated by taxonomy and subjected to study the composition of dominant species,biodiversity pattern and spatial distribution in 2011.Spearman correlations of trace metals,natural sediment characteristics and polychaete community were also analyzed.Our results show that Lumbrineris heteropoda and Capitella capitata were dominant polychaete species in spring,and Index of Relative Importance(IRI) value were 5489 and 2008 respectively.The dominant polychaete switched to be Cirratulus cirratus in summer,and IRI value became 3960.The opportunity polychaete accounted for 37.5% in dominant polychaete species of Laizhou Bay.The averages Shannon-Wiener indices were lower at the stations of S01,S05,S08,S13,S14,S15,S18,S19 and S20,and relatively higher at the stations of S04,S06,S07,S11,S16 and S17.The hierarchical clustering,un-weighted pair group method with arithmetic mean(UPGMA),and non-metric multidimensional scaling(NMDS) approaches were used to analyze the pattern of community compositions.Two polychaete community assemblages were found in Laizhou Bay in our study.Sampling stations of S19 and S20 formed an independent cluster,and the other stations constituted the group Ⅱ.Abundance biomass comparison(ABC) calves and W-statistic were used to analyze the disturbed states.In undisturbed states,the community was supposed to be dominated by k-selected species(slow-growing,large,late maturing),the biomass curve lied above the abundance curve,and the W-statistic value was positive.With increasing disturbance,the system was increasingly dominated by r-selected species(fast-growing,small,opportunistic),the biomass curve would lie below the abundance curve,and the W-statistic value was negative.Both ABC and W-statistic values were generated by PRIMER software(Plymouth Routines in Multivariate Ecological Research).Intersection was found between the abundance curves and the biomass curves in Laizhou Bay,indicating current polychaete communities were moderately disturbed.The BOPA index,appropriate for surveying the temporal changes of macrobenthic systems at high frequencies,can be used to assign estuarine and coastal communities into five statuses of ecological quality.The BOPA index showed that two stations(S15 and S16) had moderate ecological status in spring,and one site was heavily polluted in summer.Therefore,such trend revealed by the ABC plot and BOPA index suggests that Laizhou Bay was in an ecologically unhealthy condition.The sediment was sorted into medium sand,fine sand,fine silt and clay.Textural patterns such as fine silt,silty sand and sandy silt were observed in Laizhou Bay with various levels of mixing of the three textural grades of sand,silt and clay.Analysis of the correlations between the polychaete community and environmental variables for all the stations yielded high values of the rank correlation coefficient(ρs) for the best-correlated variable combination(0.8),suggesting that physical and chemical characteristics of the sediments played a significant role in affecting the polychaete community structure in Laizhou Bay.Individual analysis of correlation showed the higher values of ρs and differences in the best-correlated variable combinations in different seasons.The BIO-ENV analyses indicated that the grain size fractions(medium sand and fine sand) were the major environmental variables influencing the polychaete community patterns.Nevertheless,other unmeasured,physical,chemical and biological factors and their interactions may also have been involved in affecting the macrobenthic patterns.Therefore,components of dominant species,biodiversity pattern,spatial distribution and correlation of trace metals,natural sediment characteristics and polychaete community were important to evaluate the quality of ecological environment in Laizhou Bay,and could provide the basic scientific information for environmental pollution control and marine ecological protection.

Polychaete assemblage as surrogate for prey availability in assessing southeastern Bering Sea flatfish habitat

The flatfish yellowfin sole (Limanda aspera), northern rock sole (Lepidopsetta polyxystra), and Alaska plaice (Pleuronectes quadrituberculatus) in the southeastern Bering Sea prey mainly on infauna. Spatial correspondence between their stomach contents and infauna assemblages across habitat types was examined to identify indices of prey availability for flatfish habitat characterization and quality assessment. Benthic samples and flatfish stomachs were collected in 2009 near the Alaska Peninsula in the southeastern Bering Sea. Polychaetes and bivalves were the most dominant infauna groups, each comprising 35–60% by weight in each infauna sample. These two were also the only prey groups that frequently averaged >50% of stomach content by weight. Bivalves dominated the infauna biomass on the relatively sandy inner shelf (0–50m depth). The muddier middle shelf (50–100m) had the highest infauna biomass, which was dominated by polychaetes. Diet compositions of the flatfish varied spatially in correspondence with the infauna assemblage. Polychaetes were prevalent in all flatfish diets on the middle shelf, even yellowfin sole whose typical primary prey are amphipods and bivalves. Polychaete-rich habitats are potentially prime for flatfish as polychaetes are readily utilized where available and generally have high nutritional value. Flatfish did not select for specific polychaete taxa, so an index of habitat quality could be based on the biomass of aggregate polychaetes or on dominant polychaete families of the region. Under normal environmental conditions, the three flatfish have slightly-offset spatial distributions, enabling each to utilize different infauna assemblages across the shelf. However, during cold phases in the Bering Sea ecosystem, as when this study was conducted, a cold pool of <2°C bottom water from the spring ice melt extends over the middle shelf in summer. This physiological barrier displaces all three flatfish to the inner shelf, intensifying competition for prey resources.

The benthic association between a bivalve and a shell boring polychaete and their potential food sources

The trophic relationships in the association of the Yeso scallop Mizuhopecten yessoensis and its dominant endobiontic polychaete Polydora brevipalpa, which burrows into the scallop’s shell, and their potential food sources were studied using the method of fatty acid biochemical markers. It is shown that the differences in the diet of the scallop and the polychaete allow them to coexist in a close association. The trophic role of the association in the benthic community was revealed. The association selectively utilizes the food sources of the environment. It almost does not consume organic matter of bottom sediments, which allows it to coexist with other species in the community of higher order. There is minimal food competition between the association and detritivorous species; however, association can limit the development of species mostly foraging on diatom algae.

A biomonitor as a measure of an ecologically-significant fraction of metals in an industrialized harbour

Biomonitors are commonly used to assess levels of bioavailable contaminants in the environment, however the relationships between biomonitor tissue concentrations and ecological effects are rarely assessed. The present study investigated metal contamination within a highly industrialised harbour and ecological effects on sessile invertebrates. The native oyster Saccostrea glomerata was deployed as a biomonitor across twenty-six sites to test for correlations between metal levels in their tissues and the recruitment of hard-substrate invertebrates. Concentrations of lead and copper in oyster tissues were negatively correlated with densities of the dominant barnacle, Amphibalanus variegatus, and positively correlated with densities of the dominant polychaete, Hydroides elegans, and the two native encrusting bryozoans Celloporaria nodulosa and Arachnopusia unicornis. Results suggest that highly localised events drive contaminant availability and that these events pose a significant risk to fauna. Biomonitoring studies may be enhanced by running concurrent ecological surveys.

Larval growth in the dominant polychaete Polydora ciliata is food-limited in a eutrophic Danish estuary (Isefjord)

Food limitation in larval growth of the spionid polychaete Polydora ciliata was examined in a typical eutrophic estuary, Isefjord, in Denmark. In the field, food availability and the energetic requirements of the P. ciliata larval population were measured during 2 different periods in 2004 and 2007 that together cover the productive part of the year for plankton. In the laboratory, specific growth rates (µ) of larvae reared on natural food suspensions (~0.10 d -1 ) were always lower than those of larvae reared on phytoplankton-enriched food suspensions (100% retention efficiency for Rhodomonas salina; ~0.21 d -1 ). Total meroplankton biomass (average: 3.72 µg C l -1 , range: 0.11 to 26.05 µg C l -1 ) was frequently similar to or exceeded that of holoplankton (average: 5.70 µg C l -1 , range: 0.08 to 29.89 µg C l -1 ), suggesting a trophic significance of meroplankton in the estuary. P. cil- iata was commonly the dominant meroplanktonic larvae (average: 0.5 µg C l -1 , range: 0.03 to 2.51 µg C l -1 ). The available food in the optimal prey size fraction (2004, average: <20 µm; range: 99 to 274 µg C l -1 ; 2007, average: 7 to 18 µm; estimated carbon demand: 119 µg C l -1 ; range: 19 to 474 µg C l -1 ) seemed to be sufficient to cover the energetic carbon requirements of the population through- out the study (0.09 to 3.15 µg C l -1 d -1 ), but insufficient to attain the maximum specific growth rates reported in previous laboratory experiments. This suggests that P. ciliata larvae probably exhibit a low feeding efficiency and their maximum specific growth rates are consequently attained at food concentrations even higher than those found in this eutrophic environment.