Soft-bottom Macrobenthic Communities Research Articles

Seafloor warm water temperature anomalies impact benthic macrofauna communities of a high-Arctic cold-water fjord

Amid the alarming atmospheric and oceanic warming rates taking place in the Arctic, western fjords around the Svalbard archipelago are experiencing an increased frequency of warm water intrusions in recent decades, causing ecological shifts in their ecosystems. However, hardly anything is known about their potential impacts on the until recently considered stable and colder northern fjords. We analyzed macrobenthic fauna from four locations in Rijpfjorden (a high-Arctic fjord in the north of Svalbard) along its axis, sampled intermittently in the years 2003, 2007, 2010, 2013 and 2017. After a strong seafloor warm water temperature anomaly (SfWWTA) in 2006, the abundance of individuals and species richness dropped significantly across the entire fjord in 2007, together with diversity declines at the outer parts (reflected in Shannon index drops) and increases in beta diversity between inner and outer parts of the fjord. After a period of three years with stable water temperatures and higher sea-ice cover, communities recovered through recolonization processes by 2010, leading to homogenization in community composition across the fjord and less beta diversity. For the last two periods (2010-2013 and 2013-2017), beta diversity between the inner and outer parts gradually increased again, and both the inner and outer sites started to re-assemble in different directions. A few taxa began to dominate the fjord from 2010 onwards at the outer parts, translating into evenness and diversity drops. The inner basin, however, although experiencing strong shifts in abundances, was partially protected by a fjordic sill from impacts of these temperature anomalies and remained comparatively more stable regarding community diversity after the disturbance event. Our results indicate that although shifts in abundances were behind important spatio-temporal community fluctuations, beta diversity variations were also driven by the occurrence-based macrofauna data, suggesting an important role of rare taxa. This is the first multidecadal time series of soft-bottom macrobenthic communities for a high-Arctic fjord, indicating that potential periodic marine heatwaves might drive shifts in community structure, either through direct effects from thermal stress on the communities or through changes in environmental regimes led by temperature fluctuations (i.e. sea ice cover and glacial runoff, which could lead to shifts in primary production and food supply to the benthos). Although high-Arctic macrobenthic communities might be resilient to some extent, sustained warm water anomalies could lead to permanent changes in cold-water fjordic benthic systems.

Is the benthic index AMBI impervious to seasonality and data transformations while evaluating the ecological status of an anthropized monsoonal estuary?

Benthic indices are a potential measure of a system's ecological quality status. It is vital for an efficient index to distinguish the anthropogenic effects from the natural stress associated with seasonality, especially in complex ecosystems such as the tropical monsoonal estuaries. AZTI's Marine Biotic Index (AMBI), one of the most successful indices, relies on the distribution of soft-bottom macrobenthic communities into five different ecological groups (EGs) according to their sensitivity to stress. The AMBI was employed in the anthropized Ulhas estuary (India) to test its vulnerability to seasonality. Also it was endeavored in this study to test whether data transformations enhanced the efficiency of AMBI. AMBI values obtained during monsoon failed to distinguish between differently impacted stations in the major stretch of the estuary due to the uniformly dominant occurrence of Namalycastis ouanaryensis, an EG IV species with affinity for low salinity. The AMBI successfully evaluated the status of the estuary during the non-monsoonal seasons whereas it failed to perform well during the monsoon as it either underestimated or overestimated the ecological quality status of >55% of the stations. The results obtained by averaging the AMBI scores of the non-monsoonal seasons gave an accurate ecological status of the estuary. A good level of agreement between all the applied transformations implied that the data transformations did not improve the AMBI efficiency. Conversely, AMBI based on untransformed data indicated a stronger correlation with the contamination proxies than those derived from various data transformations.

Distribution of soft bottom macrobenthic communities in tropical marinas of Singapore

The establishment of marinas alters physico-chemical conditions and affects distribution of resident epibiotic and pelagic communities along coastal areas. However, information on the soft bottom macrobenthos within and around these boating facilities in the tropics is limited. Here, we investigated if macrobenthic communities differed among three representative tropical marinas, and whether the communities inhabiting the marinas differed from those outside the marinas. Ekman grab sampling of the soft bottom sediment at three Singapore marinas – Raffles Marina (RM), ONEo15 Marina (OMC), Marina at Keppel Bay (MKB) – yielded a total of 73 taxa from eight phyla. Accounting for temporal variations, taxonomic richness did not differ among marinas, while Shannon index (MKB > RM = OMC) and abundance (RM > OMC > MKB) did. Macrobenthic community composition differed among the marinas, with RM dominated by a high proportion of opportunistic species and OMC supporting species that were sensitive to pollution. The surveys also revealed that communities within and outside marinas differed. Unlike RM which is more enclosed, diversity was higher within MKB than outside it, likely because the latter marina had a layout that encouraged flushing which maintained good water quality. The study showed that while Singapore’s tropical marinas can support diverse groups of macrobenthic taxa, the presence of high proportions of opportunistic species suggested that pollution within the marinas was still significant. Macrofaunal diversity in tropical marinas, such as those in Singapore, may be promoted by designs that improve water exchange.

Preliminary Results on the Composition and Structure of Soft-Bottom Macrobenthic Communities of a Seamount: the Galicia Bank (NE Atlantic Ocean)

The Galicia Bank (Atlantic Ocean, NW Iberian Peninsula) is a flat-topped seamount located about 200 km from the northwest coast of Spain. This bank is included in the LIFE+ “INDEMARES” project, who aims to identify priority areas of conservation in the Spanish seas. In 2010 and 2011 two oceanographic surveys were carried out to investigate species and habitats of this deep ecosystem. A total of 28 stations were sampled using a box corer with a sampling area of 0.09 m2, in order to evaluate the distribution and biodiversity of the macroinfauna of the Galicia Bank. An additional sediment sample was taken at each station to analyse the granulometric composition and the organic matter content. Sediments were mainly sandy in nature (medium, fine and very fine sands), with low levels of organic matter content. The samples analysed yielded a total of 1189 individuals, belonging to 89 families. Polychaetes were the best represented group in total number of individuals (67%), followed by molluscs (14%). Echinoderms (9.7%), crustaceans (6%), and the Others group (Nemertea and Sipuncula) (3.9%) were less abundant. Two major macrobenthic assemblages were determined through multivariate analyses. Sedimentary composition was the main factor structuring the benthic community, separating medium sand stations from those that had finer sediments.

Structural and functional diversity of soft-bottom macrobenthic communities in the Southern North Sea

Our study presents a revision of the structural characteristics of the soft-bottom benthic communities in the Belgian Part of the North Sea (BPNS) and provides, for the first time, an insight into their functional characteristics. Compared to previous research, the dataset expanded considerably on a spatial and temporal scale (1994–2012). Five communities were identified, each with their own structural characteristics, indicator species, sediment properties and spatial distribution. The offshore area was dominated by the Hesionura elongata community (formerly Ophelia borealis), and although previously described by low diversity and abundance, this study shows that this community has the second highest sample diversity and moderate densities. Also, a new community, the Magelona-Ensis leei community, was found in very shallow water and characterized by low diversity and the dominance of the non-indigenous species E. leei. The structural characteristics and spatial distribution of the previously described Limecola balthica, Abra alba and Nephtys cirrosa community remained largely unchanged. Though structurally distinct, the communities overlap in some of their functional attributes. Analysis of biological traits revealed that in the coarser permeable sands, both the N. cirrosa and H. elongata community harbor more free living mobile individuals, causing diffusive mixing. The finer sand (A. alba, Magelona- Ensis leei) and muddy (L. balthica) communities hold more sessile, tube building and burrow dwelling species. Apart from diffusive mixing, sediment reworking in these finer sands occurs by surface deposition and downward convection. In combination with higher densities and biomass, this results in a higher bioturbation potential (BPc) for the Abra alba and Magelona-Ensis leei community. Finally, measures for functional diversity and redundancy were calculated, and were also highest in the Abra alba and Hesionura elongata community, thus demonstrating the importance of both communities for conservation purposes from a structural as well as a functional perspective. The analyses revealed that even in well-studied areas new data give new insights, with important consequences for management. Our study forms a benchmark for future ecosystem health status assessments in the framework of international and national nature management obligations such as the European Marine Strategy Framework Directive (MSFD), the Habitats Directive and the Marine Spatial Planning Directive.

Macrobenthic communities in a shallow normoxia to hypoxia gradient in the Humboldt upwelling ecosystem.

Hypoxia is one of the most important stressors affecting the health conditions of coastal ecosystems. In highly productive ecosystems such as the Humboldt Current ecosystem, the oxygen minimum zone is an important abiotic factor modulating the structure of benthic communities over the continental shelf. Herein, we study soft-bottom macrobenthic communities along a depth gradient–at 10, 20, 30 and 50 m–for two years to understand how hypoxia affects the structure of shallow communities at two sites in Mejillones Bay (23°S) in northern Chile. We test the hypothesis that, during months with shallow hypoxic zones, community structure will be much more dissimilar, thereby depicting a clear structural gradient with depth and correlated abiotic variables (e.g. organic matter, temperature and salinity). Likewise, during conditions of deeper hypoxic zones, communities will be similar among habitats as they could develop structure via succession in conditions with less stress. Throughout the sampling period (October 2015 to October 2017), the water column was hypoxic (from 2 to 0.5ml/l O2) most of the time, reaching shallow depths of 20 to 10 m. Only one episode of oxygenation was detected in June 2016, where normoxia (>2ml/l O2) reached down to 50 m. The structure of the communities depicted a clear pattern of increasing dissimilarity from shallow normoxic and deep hypoxic habitat. This pattern was persistent throughout time despite the occurrence of an oxygenation episode. Contrasting species abundance and biomass distribution explained the gradient in structure, arguably reflecting variable levels of hypoxia adaptation, i.e. few polychaetes such as Magelona physilia and Paraprionospio pinnata were only located in low oxygen habitats. The multivariable dispersion of community composition as a proxy of beta diversity decreased significantly with depth, suggesting loss of community structure and variability when transitioning from normoxic to hypoxic conditions. Our results show the presence of semi-permanent shallow hypoxia at Mejillones Bay, constraining diverse and more variable communities at a very shallow depth (10–20 m). These results must be considered in the context of the current decline of dissolved oxygen in most oceans and coastal regions and their impact on seabed biota.

Interannual variability of soft-bottom macrobenthic communities of the NW Gulf of Mexico in relationship to the Deepwater Horizon oil spill

A 3-year research program was undertaken to assess potential environmental disturbance caused by the Deepwater Horizon oil spill to the soft-bottom macrobenthic communities within Mexican waters of the northwestern Gulf of Mexico. Community properties and temporal/spatial variability were analyzed besides toxicant parameters such as hydrocarbons and trace-metals. Overall infaunal density increased, taxa proportion changed, and small-size opportunistic organisms prevailed throughout the study. Annual abundance-biomass comparison (ABC) curves revealed progressive stress scenarios from moderate to severe. Concentrations of vanadium, nickel, cobalt, PAHs and AHs increased gradually over time. However, low correlations between benthic density and biogeochemical variables were determined. Initially, sedimentary properties were the main drivers of benthic community structure; subsequently, nickel, vanadium and PAHs, indicative of anthropogenic effect, were highlighted. Interannual variability in the macroinfauna was attributed to the synergy of several environmental factors. Undoubtedly, compounds derived from fossil fuels had a significant disturbance role, but their source remains uncertain.

Spatial variability of soft-bottom macrobenthic communities in northern Sicily (Western Mediterranean): Contrasting trawled vs. untrawled areas

This study examines the impact of bottom trawl fishing on the macrobenthic communities inhabiting the coastal terrigenous mud off the northern coast of Sicily (Western Mediterranean). Two intensely trawled gulfs were compared with two gulfs from which trawling has been excluded for 15 years. The results show a significant effect of trawling on the faunal assemblage and when comparing the mean biomass and the whole isotopic composition of the benthic communities. A similar pattern, although not significant, was found for total abundance, biomass, production/biomass ratio and diversity. Higher abundance and lower biomass were found in the untrawled areas, attributable to the presence of more numerous yet smaller individuals, possibly a consequence of more abundant larger predators that are not removed by trawling, and consequent higher predatory pressure on the benthic macrofauna. The SIMPER analysis evidenced a dominance of burrowing deposit feeding worms (Paraonidae and Cossuridae) in trawled areas, as a result of increased mechanical alteration and hence more organic matter available as food. In contrast, the response to trawling as drawn by the use of trophic markers (i.e., stable isotopes) was less clear. While δ15N of benthic taxa did not vary significantly between untrawled and trawled areas, δ13C was higher in trawled areas possibly due to high sediment resuspension and consequent intense microbial activity. Mixing models confirmed higher reliance to a detritus-based food web for benthic organisms in the trawled areas. Standard Ellipse Areas (SEAc) as a measure of community niche width were slightly larger in trawled areas, likely due to higher generalism triggered by alteration/removal of the original benthic community.

Influence of organic matter inputs and grain size on soft-bottom macrobenthic biodiversity in the upwelling ecosystem of central Chile

Soft-bottom macrobenthic communities on the continental shelf of central Chile were characterised, in number, by polychaetes, followed by amphipods, bivalves and cumaceans, while biomass was dominated by Amphioplus magellanicus (Ophiuroidea). The standing stocks followed a parabolic pattern relative to depth (highest at mid-shelf) but the species were divided into inshore (22 to 50 m) and offshore (80 to 140 m) assemblages, based on the similarity in species composition. Diversity (Es) was highest in the shallow assemblage and lowest at the deeper locations, suggesting that the decline in oxygen offshore was impacting the numbers of species. Dominance followed the opposite pattern, with greatest dominance at the deepest two stations. The distribution of sizes at each site, measured as normalised biomass size spectra (NBSS), was not different among the sites, although total biomass was concentrated in the single large ophiuroid at the deepest location. Significant correlations (p < 0.05) indicated that diversity and number of species were mainly related to the organic content (i.e. total organic carbon) and sediment composition (grain size). Therefore, food supply from primary production and the physical properties of the seafloor are thought to be the main forces structuring the macrobenthos biodiversity and distribution.

Bottom-up control of macrobenthic communities in a guanotrophic coastal system.

Soft bottom macrobenthic communities were studied seasonally in three coastal ponds (Marinello ponds, Italy) at increasing distances from a gull (Larus michahellis) colony to investigate the effect of seabird-induced eutrophication (i.e. guanotrophication) on macrobenthic fauna. We hypothesized that enhanced nutrient concentration and organic load caused by guano input significantly alter the trophic and sedimentological condition of ponds, affecting benthic fauna through a bottom-up control. The influence of a set of environmental features on macrobenthic assemblages was also tested. Overall, the lowest macrobenthic abundances and functional group diversity were found in deeper sites, especially in the pond characterised by severe guanotrophication, where the higher disturbance resulted in a decline in suspension feeders and carnivores in favour of deposit feeders. An increase in opportunistic/tolerant taxa (e.g. chironomid larvae and paraonids) and totally azoic sediments were also found as an effect of the harshest environmental conditions, resulting in a very poor ecological status. We conclude that macrobenthic assemblages of the Marinello coastal system display high spatial variability due to a synergistic effect of trophic status and the geomorphological features of the ponds. The macrobenthic response to guanotrophication, which was a clear decrease in abundance, diversity and trophic functional groups, was associated with the typical response to severe eutrophication, magnified by the geomorphological features.

Checking the concurrence among macrobenthic organism distribution patterns at different taxonomic scales in relation to environmental factors

The interaction of both natural conditions and anthropogenic environmental impacts can lead to different soft-bottom macrobenthic distribution patterns. Soft-bottom macrobenthic community was analysed at different taxonomic scales in order to evaluate whether diverse subsets of organisms respond to the variability of the environmental pressures (natural and human induced) showing or not similar distribution patterns. Therefore, this long-term survey had been focused on a heterogeneous area, where both anthropogenic and natural stresses may affect the community. Three perpendicular transects to the coast were established and stations at 4, 10 and 15m depths were sampled at each transect twice a year (summer–winter) from 2004 to 2009. Non-parametric multivariate techniques were used to analyse soft-bottom macrobenthic community distribution and its relation to the environmental factors. Similar distribution patterns between investigated taxonomic levels were detected and they were mainly related to depth.

A process-driven sedimentary habitat modelling approach, explaining seafloor integrity and biodiversity assessment within the European Marine Strategy Framework Directive

The Marine Strategy Framework Directive (MSFD) seeks to achieve good environmental status, by 2020, for European seas. This study analyses the applicability of a process-driven benthic sedimentary habitat model, to be used in the implementation of the MSFD in relation to biodiversity and seafloor integrity descriptors for sedimentary habitats. Our approach maps the major environmental factors influencing soft-bottom macrobenthic community structure and the life-history traits of species. Among the 16 environmental variables considered, a combination of water depth, mean grain size, a wave-induced sediment resuspension index and annual bottom maximum temperature, are the most significant factors explaining the variability in the structure of benthic communities in the study area. These variables are classified into those representing the ‘Disturbance’ and ‘Scope for Growth’ components of the environment. It was observed that the habitat classes defined in the process-driven model reflected different structural and functional characteristics of the benthos. Moreover, benthic community structure anomalies due to human pressures could also be detected within the model produced. Thus, the final process-driven habitat map can be considered as being highly useful for seafloor integrity and biodiversity assessment, within the European MSFD as well as for conservation, environmental status assessment and managing human activities, especially within the marine spatial planning process.

Recovery Process on Soft-Bottom Macrobenthic Communities after Artificial Disturbance in Tropical Polluted Estuary (Guanabara Bay, Rio de Janeiro, Brazil)

The regime of disturbance with natural or anthropogenic origin can lead to the destabilization or even to a mass mortality of benthic communities. Due to the heterogeneity of the disturbance there is a formation of patches in different stages of ecological succession. The aim of this study is to follow and describe the resilience in artificial disturbed sediment in a polluted bay in Rio de Janeiro. The sediment was collected, sterilized and placed inside corers (10 cmdiameter ×15 cmheight) in the same place where it was collected. We allocated the samples in two structures, the difference between them was that one was placed closed to the bottom and the other was placed50 cmheight. We found 2352 organisms distributed in 14 taxons. The class Polychaeta and the order Amphipoda showed the highest density in all the survey and treatments. We identified the factors influencing the scenarium: different mechanisms of dispersal, the position of the structures and life history of each group. Disturbance can be the main cause of the patch’s diversity found in estuaries and coastal areas. Because of this, monitoring of selected areas becomes an important tool to understand the regime of disturbance as a key factor structuring benthic communities in soft sediment, also suggesting a metapopulation dynamics.

Spatial and temporal changes in macrobenthic communities in the Amazon coastal zone (Guajará Estuary, Brazil) caused by discharge of urban effluents

Spatial and temporal changes in the structure of soft-bottom macrobenthic communities caused by discharges of urban wastewater were studied in the Guajara Estuary, Amazon coastal zone, Brazil. Samples were taken during the dry and rainy seasons at five sites close to wastewater sources (impacted) and two sites further away from effluent discharges (non-impacted). Samples were collected using a Petersen grab (20×20×20 cm) and passed through a 0.3 mm mesh screen. At each site, several parameters were determined in order to characterize the water (pH, QOD and NH 4 ) and sediment (mean grain size diameter, %OM and heavy metals). The benthic fauna was composed of 22 taxa dominated by polychaetes and oligochaetes. The data indicate that environmental contamination has not resulted in a highly polluted environment with a significant reduction in fauna. It would seem that the river flow and intense hydrodynamics dilute and minimize the effects of contaminants in the estuary. The main effect of the discharge effluents was a favorable organic enrichment. The fauna at the impacted sites was generally more diverse than at the non-impacted sites, dominated by Oligochaeta Tubificinae, and showed greater spatial heterogeneity.

Facultative feeding and consistency of trophic structure in marine soft-bottom macrobenthic communities

We investigated the roles of facultative versus strict niche feeding in the maintenance of trophic consistency in soft-bottom macrobenthic communities in the Strait of Georgia, British Columbia, Canada. Changes in trophic structure across gradients in depth and percent fine sediments were examined over a broad regional scale by identifying trophic compartment(s) re sponsible for the resulting trophic changes. The use of proportional organic biomass data allows direct comparison of community trophic structure across diverse hydrographic regime(s), large ranges in overall biomass and productivity, and highly variable community composition. Cluster analyses revealed low overall dissimilarity in trophic structure across all substrate and depth ranges (24 and 28% divergence, respectively), suggesting an overall economy of trophic function. Similarity percentage (SIMPER) analyses revealed that low trophic dissimilarity is driven primarily by the remarkably even distribution of the 2 dominant facultative feeding groups in all habitat types. These facultative groups contained the most ubiquitous and abundant taxa found throughout the Strait, and likely confer strong resilience in these communities to habitat change. In contrast, the small but significant divergences in trophic structure over depth and percent fine sediment gradients was explained by the distributions of strict niche feeders: (1) macro-omnivores and herbivores dependent on non-detrital food sources were important in shallow areas (<25 m) with coarse sediments (<10% fine sediment), contributing to a unique trophic composition in these areas; and (2) subsurface deposit feeders were the only trophic group to vary significantly in proportional biomass explained by depth and percent fine sediment combined (22%; positive linear response to both factors).

The relationship between soft-bottom macrobenthic communities and environmental variables off Ningjin, eastern Shandong Peninsula

Macrobenthic infauna and associated environmental factors influencing the benthic community in the eastern coastal region of Shandong Peninsula were analyzed in four seasonal surveys from January 2007 to October 2007 (30 stations in winter, 20 stations in other three seasons), in order to understand the community structure and the factors unfluencing the benthic distribution. PRIMER 6.0 and SPSS 15.0 software packages were adopted to analyze the environmental and macrobenthic data,. The results show that there were 260 macrobenthic species in total collected from the research region. The composition of species is: Polychaeta (94 species), Crustacea (75), Mollusca (56) and Echinoderm (12), among which, only 23 species were common species in the cruises of every season. The dominant species varied from season to season; however, the polychaete species Paralacydonia paradoxa Fauvel and Echinoderm species Arnphioplus japonicas (Matsumoto) were always present year-round. The abundance and biomass of the macrobenthos in the research region were variable from season to season. The results of CLUSTER and MDS analysis show that the similarities of macrobenthic structures between the stations were low; most of the similarities were at about 30% of similarity value, only two stations were up to 70%. In accordance with the similarity values of the rnacrobenthic structures, we divided the 20 stations into five groups by arbitrary similarity level of 30%. The ABC curve indicates that the marcofauna communities in the research region had not been disturbed massively, except two stations, SB1 and SB3. Ecologically, benthos were controlled by a combination o.f factors such as salinity, phytoplankton, zooplankton, SiO(3)-Si and temperature, and no single factor could be considered as an ecological master factor.

Macrofaunal Spatial Patterns in Relationship to Environmental Variables in the Richibucto Estuary, New Brunswick, Canada

Estuarine macrobenthos respond to a variety of environmental gradients such as sediment type and salinity, and organic enrichment. A relatively new influence, organic loading from suspended bivalve culture, has the potential to alter this response. A study on soft-bottom macrobenthic communities was carried out in the Richibucto estuary (46°40′N, 64°50′W), New Brunswick, Canada, with samples collected from 18 stations in late September and early October 2006. The site consisted of a large tidal channel originating upstream in a small river. The channel was punctuated by bag culture of oysters along its length. A total of 88 species were recorded. The mean values of abundance, species richness, and diversity (H′) of macrofauna were 11,199 ind. m−2 (ranged from 4,371 to 19,930 ind. m−2), 23.4 species grab−1 and 3.29 grab−1, respectively. In general species richness and H′ increased from the upper estuary to the estuarine mouth. Multivariate analyses clearly exhibited the spatial distribution in community structure, which coincided with the locations along the estuary (the upper, the lower and the mouth), as well as inside and outside the channel. Species richness and diversity H′ showed strong positive correlations with salinity (21.2–25.2 ppt), and abundance was positively correlated with water depth (1.0–4.5 m). Abundance and species richness were negatively correlated with both of silt–clay fraction (3.3–24.8%) and sorting (σI). Species richness was also negatively correlated with organic content (1.9–12.7%). The BIO-ENV analyses identified silt–clay fraction, σI and salinity as the major environmental variable combination influencing the macrofaunal patterns, and silt–clay fraction as the single best-correlated variable.

On the Occurrence and Established Populations of the Alien Polychaete Polydora cornuta Bosc, 1802 (Polychaeta: Spionidae) in the Sea of Marmara and the Bosphorus Strait (Turkey)

The present paper reports the first occurrence of Polydora cornuta in the Bosphorus Strait and its finding in a new locality in the Sea of Marmara, providing a link with its Aegean and Black Sea populations. The probable vector for the introduction of P. cornuta into the Sea of Marmara is shipping through the Dardanelles Strait. Both soft and hard-bottom populations were examined and the importance and prevalence of this species within the native macrozoobenthic communities were elucidated. Its abundance ranged between 40 and 3390 ind.m-2 (mean:1320 ±1199.45 SD) and its percent contribution to the total faunal populations ranged between 3.31 and 75.56 (mean:27.79 ±25.00 SD) in the Sea of Marmara softbottom community. During the sampling period, P. cornuta contributed little to the total faunal abundance of the hard-bottom communities in the Bosphorus Strait. Its mean abundance in the hard substrate ranged between 8.33 and 1000 ind.m-2 (mean:117.36 ±279.73 SD) and its percent contribution to the total faunal populations ranged between 0.02 and 21.86 (mean:2.07 ±6.25 SD).The role of this invasive species in the soft-bottom macrobenthic community at an organically enriched site examined in the Sea of Marmara is highlighted, and a comparison with Aegean Sea populations of the species is also included.

Mesoscale spatial structures of soft-bottom macrozoobenthos communities: effects of physical control and impoverishment

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 356:215-224 (2008) - DOI: https://doi.org/10.3354/meps07285 Mesoscale spatial structures of soft-bottom macrozoobenthos communities: effects of physical control and impoverishment Maria Wlodarska-Kowalczuk*, Jan Marcin Weslawski Institute of Oceanology PAS, Powstancow Warszawy 55, PO Box 68, 81-712 Sopot, Poland *Email: maria@iopan.gda.pl ABSTRACT: The recognition of the nature of spatial and temporal variability within ecosystems is crucial for understanding the processes that maintain species diversity and ecological stability. In the present study, mesoscale spatial structures of soft-bottom macrobenthic communities were explored at sites with contrasting disturbance regimes and benthic diversities. Two sites in a glacial Arctic fjord were selected: the Inner site, where sediments are inhabited by an impoverished community composed of a few species resistant to large-scale, chronic physical disturbance by glacial sedimentation, and the Outer site, where diverse fauna is structured by biological interactions among populations of species of different sizes and functional groups. Samples were taken at 6 stations (4 van Veen grabs collected per station) located along a 1 km transect separated by 0 (samples collected at the same station), 200, 400, 600, 800, and 1000 m. Spatial variation at the Inner site was apparent only in changes in relative abundances among a few numerically dominant species (explored using untransformed data), and the fauna was homogenous with respect to species composition (based on presence/ absence data). The spatial heterogeneity in the Outer site community was evident both in species composition and in relative abundances of dominant species populations. The significant autocorrelation peaks on a correlogram of Bray-Curtis similarities of untransformed data indicated a successive sequence of homogenous patches of a minimum 200 m radius, separated by 600 m. Spatial patterns of species composition similarity varied among species groups of different mobility: sedentary fauna did not exhibit a mesoscale patchiness, while clear patchiness was documented for motile and discretely motile organisms. The current study demonstrates that the spatial structure of benthic biota is related to the diversity and the perturbation level of the studied communities. It also supports the recommendation for spatial separation of replicate samples in soft-bottom macrobenthic surveys. KEY WORDS: Spatial patterns · Scale · Soft bottom · Macrofauna · Diversity · Disturbance Full text in pdf format PreviousNextCite this article as: Wlodarska-Kowalczuk M, Weslawski JM (2008) Mesoscale spatial structures of soft-bottom macrozoobenthos communities: effects of physical control and impoverishment. Mar Ecol Prog Ser 356:215-224. https://doi.org/10.3354/meps07285 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 356. Online publication date: March 18, 2008 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2008 Inter-Research.

Soft bottom macrobenthic communities of North Biscay revisited: Long-term evolution under fisheries-climate forcing

Thirty-five years after the first description of the benthic community and sediments of the North Bay of Biscay continental shelf (80–200 m depth in the “Grande Vasière” region) by Glémarec (personal communication), the sampling stations were revisited to provide a new reference on the status of the macrozoobenthic communities to help our understanding and management of fisheries that are highly developed in this area. Results showed that large modifications occurred in the communities and sediments of the central part of the “Grande Vasière”, while these modifications remained moderate in the surroundings on the outer continental shelf. Revisited, macrobenthic communities differed greatly from those recorded in the 1960s, and were less numerous and more homogeneous. The dominant species which characterized the communities and sub-communities had also changed. The main factor that can explain these differences is the granulometry of the sediments which has shown large changes: a strong decrease in the mud fraction and increase in the fine sand fraction. These sedimentary changes should be linked with human activities: increase in bottom trawling effort that induces the resuspension of fine mud particles and the homogenization of sediments over large areas, and decrease in terrigenous particulate fluxes due to anthropic activities on the shoreline and in coastal waters. Effects of global climatic change on the observed evolution remain low, even if some species common in the south of the Bay of Biscay in the 1960s but rare or absent in the north, had increased in density and spread to the north. Trawling activities are probably the main force driving benthic community evolution in the North Bay of Biscay both through direct action on the fauna (inhibition and facilitation processes) and indirect action by modifying sediment characteristics.