Soft-bottom Benthic Communities Research Articles

National assessment on the status, trends and impacts of marine non-indigenous species for the European Union marine strategy framework directive

The Marine Strategy Framework Directive (MSFD) of the European Union aims to enhance the protection of marine ecosystems by assessing Good Environmental Status using several descriptors. Descriptor 2 of the MSFD states that the status of marine non-indigenous species (NIS) should be assessed using specified criteria regarding newly introduced NIS, abundance, and spatial distribution of established NIS, as well as proportions of native species groups adversely altered due to NIS. The current study presents a national NIS indicator assessment for the six sub-basins associated with the Finnish marine waters. The study additionally aimed to develop a methodology to assess changes in native species communities over time. A new biodiversity index was created for this purpose by combining the Gini-Simpson index, and species and phyla richness into a Community Biodiversity Index (CBI). CBI was calculated to measure changes in biodiversity within the soft-bottom benthic communities of the study area, and correlation analyses were conducted between the index scores and NIS proportion. Overall, 34 NIS have been recorded from the Finnish marine waters by 2022, and more than half of them have arrived since 1992. Spatial distribution of three established non-indigenous taxa (Marenzelleria spp., Cercopagis pengoi and Neogobius melanostomus) has expanded during the latest assessment periods and nowadays cover most of the national marine waters. Meanwhile, abundance of Marenzelleria spp. in benthic communities has increased heavily in most sub-basins. The study outcomes indicated that NIS proportion correlated significantly with the CBI within the soft-bottom benthic communities. This correlation was significantly negative for the samples with a higher NIS proportion than the median, suggesting that when NIS became more dominant, biodiversity of the communities decreased. The current study provides an applicable method to evaluate changes in biodiversity for various species groups, and how to link them to changes in the distribution and abundance of established NIS. It can be concluded that the national biological monitoring program has severe temporal and spatial gaps, as the national monitoring data enabled the assessment on native species groups, adversely altered due to NIS to be completed only for one species group, soft-bottom macrozoobenthos. Most importantly, the study emphasised the crucial need for management actions to prevent further NIS introductions.

Lack of strong seasonality in macrobenthic communities from the northern Barents Sea shelf and Nansen Basin

The Barents Sea has been coined ‘the Arctic hotspot’ of climate change due to the rapidity with which environmental changes are taking place. This transitional domain from Atlantic to Arctic waters is home to highly productive benthic communities. This system strongly fluctuates on a seasonal basis in its sympagic-pelagic-benthic coupling interactions, with potential effects on benthic standing stocks and production. Recent discoveries have questioned the marked seasonality for several high Arctic seafloor communities in coastal waters of Svalbard. Still, the seasonal variability of benthic process in the extensive Barents Sea open shelf remains poorly understood. Therefore, we studied the seasonality of macrofauna communities along a transect in the northwestern Barents Sea comprising two hydrographic domains (Arctic vs. Atlantic Water, across the Polar Front) and three geomorphological settings (shelf, continental slope and abyssal plain). Overall, we did not find strong signs of seasonal variation in taxonomic community structure and functional diversity. However, we found some weak signs of seasonality when examining each station separately, especially at a station close to the Polar Front, with high seasonal fluctuations in abiotic drivers indicating a stronger pelagic-benthic coupling. The lack of seasonality found both at the shelf stations south and north of the Polar Front could be related to organic matter stored in the sediments, reflected in constant levels of total organic carbon in surface sediment across time for all stations. We did observe, as expected, highly spatially structured environmental regimes and macrofauna communities associated to them from shelf to slope and basin locations. Understanding the underlying spatio-temporal mechanisms by which soft-bottom benthic communities are structured along environmental gradients is necessary to predict future impacts of climate change in this area. Our results indicate that short-term climate driven changes in the phenology of pelagic ecosystem components might not be directly reflected in the Arctic benthic system, as seafloor processes seem to be partially decoupled from those in the overlying water.

Influence of sea-ice dynamics on coastal Antarctic benthos: A case study on lantern clams (Laternula elliptica) in Adélie Land

Polar regions are warming faster than the world average and are profoundly affected by changes in the spatio-temporal dynamics of sea ice, with largely unknown repercussions on the functioning of marine ecosystems. Here, we investigated the impacts of interannual sea-ice variability on coastal benthic communities in Antarctica, focusing on a close-to-pristine area (Adélie Land). We investigated shell growth of the circum-Antarctic bivalve Laternula elliptica, considered a key species in these soft bottom benthic communities. Chondrophores of live-collected clams were prepared using standard sclerochronological methods to study the interannual variability of shell growth from 1996 to 2015. Our results show that the master chronology varied with sea-ice dynamics. When sea ice breaks up too early, sympagic algae do not have time to accumulate sufficiently high biomass, thus strongly limiting the energy input to the benthos. This negatively affects the physiological performance of L. elliptica, thereby altering their population dynamics and hence the functioning of these soft-bottom ecosystems.

A preliminary study of soft bottom benthic communities in an area affected by intense maritime traffic (Slovenian Sea, Northern Adriatic)

Maritime traffic and port activities pose several environmental and ecological problems in the marine environment. The purpose of this study was to provide baseline data for the future assessment of anthropogenic impacts related with port activities in Slovenian Sea (Northern Adriatic Sea). The macrobenthic communities near the port of Koper, as well as sites offshore were analysed. Results showed that the sites offshore were generally richer and more structured than sites inside the Port area. Those differences were explained partly by depth and sediment grain size. The ecological quality indicated by M-AMBI index resulted Good/High at all the sampling sites. However, the k-dominance curves indicated a disturbance at certain sites, in particular in the port channels. This work highlights the need for consistent monitoring programs to provide baseline data for future studies assessment of anthropogenic impacts.

Some Observations on the Reproductive Biology of the Mediterranean Pennatulacean Pteroeides Spinosum (Ellis and Solander, 1786) (Cnidaria: Octocorallia: Pennatulacea)

Sea pens are some of the most important structural species in soft bottom benthic communities. Pteroeides spinosum is a shallow-water pennatulacean (Cnidaria: Octocorallia: Pennatulacea) habiting NE Atlantic-Mediterranean bottoms. In this study, sixteen colonies of Pteroeides spinosum collected from NW Mediterranean Sea (Cap de Creus, Spain) at 99–106 m depth in July (2012), were used to acquire information of their reproductive biology, and to enable a comparison with other pennatulaceans. Our colonies of Pteroeides spinosum are gonochoric showing a bimodal oocyte frequency distribution and an unimodal spermatocyst diameter distribution. All polyp leaves contained oocytes and spermatocysts in different size classes, with those small and translucent spermatocysts/ oocytes (size-class I) often found near the base or lower end of the gastrovascular cavities of polyps. The largest observed diameter was 668 μm for spermatocysts and 687 μm for oocytes. Mean potential relative fecundity (PRF) ranged between 7–17 oocytes per polyp. The effective reproductive effort (ERE) reached a value of ca. 30,000 large oocytes per colony. As was observed for all pennatulaceans previously studied, no sign of hermaphroditism or internal fertilization was detected in our colonies of Pteroeides spinosum.

Status and Trajectories of Soft-Bottom Benthic Communities of the South Florida Seascape Revealed by 25 Years of Seagrass and Water Quality Monitoring

Status and Trajectories of Soft-Bottom Benthic Communities of the South Florida Seascape Revealed by 25 Years of Seagrass and Water Quality Monitoring

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

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

Growth and reproductive traits of deep-sea pen Anthoptilum murrayi Kölliker, 1880, from Iceland (North Atlantic)

ABSTRACT Sea pens (Octocorallia: Pennatulacea) constitute one of the most important structural species in soft bottom benthic communities. Most pennatulacean species are deep-water organisms inhabiting depths from 200–6000 m. Among these deep-sea pens, a representative set of colonies from the northeastern Atlantic Anthoptilum murrayi Kölliker, 1880 was collected thanks to the BIOICE research surveys. In this study, 18 colonies of A. murrayi were used to acquire information on essential biological traits such as age and growth rates. Our results showed that the colonies collected ranged between 6–17 years, with a diametric growth rate between 0.10–0.17 mm year−1 and a linear growth rate between 14.97–15.75 mm year−1. Moreover, the number and diameter of oocytes per polyp (PRF, ERF), and the reproductive effort at the colony level (PRE, ERE) were determined. These values were compared between colonies of different sizes and within each colony. The largest observed diameter was 1179 μm for oocytes and 711.3 μm for spermatocysts. Both approaches (growth and reproduction) were correlated, indicating that a given large A. murrayi colony (∼300 mm) might be ∼17 years old and contain >7000 oocytes, from which possibly about 2000 oocytes (∼27%) would be spawned per year.

Geographic patterns of soft-bottoms benthic communities in Chilean Patagonian fjords (47°S-54°S) - influence of environmental stress on diversity patterns and stable isotope signatures

The benthic community in the Chilean Patagonia is as rich and highly diverse as the spatial variation of its habitats and food sources. Environmental stress from glacier melt and river discharge are known drivers of benthic community dynamics. Here, we analyze longitudinal patterns of soft-bottom benthic communities across transects of glacier-marine environments and how these habitats may respond to changes in the environmental conditions. To assess the relationships between environmental heterogeneity (marine and glacial habitats) and benthic biodiversity, this paper reviews biological (mega- and macroinfauna) and sedimentological dataset from multiple oceanographic campaigns in Chilean Patagonian fjords. Furthermore, we analyze isotopic compositions of epibenthic and macroinfaunal organisms (δ13C/δ15N and C/N) to determine particulate organic carbon (POC) and particulate organic nitrogen (PON) availability and organismal stoichiometric budgets within each benthic community. Our results showed that glaciomarine and glaciofluvial environmental stress negatively affected nutrient reservoirs and organic matter (OM) availability, and hence produced changes in benthic diversity and trophic structure throughout the fjords. These conditions shaped the benthic community where small-bodied polychaetes and opportunistic species dominated. Additionally, we found a strong relationship between OM and nutrient availability with faunal isotopic composition, but a decoupling in C/N ratios between fauna and sediment OM, suggesting preferential organic carbon use under limited nitrogen in fjord sediments.

Assessment of the ecological quality of soft-bottom benthic communities in the Syrian coast, Eastern Mediterranean

The present study was aimed to evaluate several benthic biological indices to assess the ecological quality status of marine environments in Syria. Samples were obtained from four different areas of Syrian coast (Al-Bassit, Banias, Tartous and Al-Hamidia) on a monthly scale from March 2007 to December 2007. Results showed that the percentage of benthic species are increased significantly in the stations with healthy ecological status. The cluster analysis and the MDS have shown that the studied stations are subjected to environmental disturbance. Some species have been found to be more sensitive (high values of Hurlbert Index) than others such as the Rhinoclavis kochi, which belonged to the Gastropodes taxa and Notomastus latericeus belonged to the polychaetes taxa. The ecological quality of the Syrian coast was assessed using three biotic indices (H′, AMBI and BQI). The Shannon–Wiener index H′ was ranged from 2.88 to 5.39. Thus, the ecological status varied between moderate and high. The values of AZTI Marine Biotic Index (AMBI) and Benthic Quality Index (BQI) classified the ecological state between high and good (slight disturbance).

What ecological and functional changes follow the positioning of an artificial barrier? Answers from a 4-year investigation on soft bottom benthic communities

What ecological and functional changes follow the positioning of an artificial barrier? Answers from a 4-year investigation on soft bottom benthic communities

Ecological quality assessement of marinas: An integrative approach combining biological and environmental data

The importance of marinas as infrastructures for recreational boating is increasing substantially. However, information on their soft-bottom benthic communities, a key tool for managing programmes, is still scarce. We combined environment features with macro- and meiofaunal soft-bottom community information for assessing the ecological status of marinas with an integrative approach. To address this issue, we focused on eight marinas of the Southern Iberian Peninsula. Macro- and meiofauna data revealed high benthic heterogeneity at a spatial scale. The environmental variables which correlated best with macrofauna were mainly phosphorus, granulometry, and total organic carbon, and secondarily important variables were faecal coliforms, the biocide Irgarol, and heavy metals; total hydrocarbon concentration was also significant for meiofauna. Annelida was the dominant phylum in terms of number of species (37%) and abundance (66%) and were better descriptors of the environmental conditions than Arthropoda and Mollusca. Although identification to the species level is desirable and mandatory for assessing biological pollution, significant differences among marinas and correlations between fauna and abiotic variables were already detected at the level of family and order. This implies that biota assessment at higher levels may still be useful in monitoring programmes limited by time and budget constraints. The major novelty of this study lies in the development of an integrative assessment method based on the following selected ecological indicators: Marinas Environmental Pollution Index (MEPI), Biocontamination Index (BCI), macrofaunal biotic indices (AMBI, M-AMBI, BENTIX, MEDOCC and BENFES), macrofaunal taxa richness and Shannon-Wiener's diversity, and nematode:copepod index. This approach was able to discriminate marinas of the Southern Iberian Peninsula based on their ecological status, which ranged from poor to good. The method can be useful to design standards for assigning “sustainable quality seals” to those marinas with better values of ecological indicators.

Spatial and temporal dynamics of Antarctic shallow soft-bottom benthic communities: ecological drivers under climate change

BackgroundMarine soft sediments are some of the most widespread habitats in the ocean, playing a vital role in global carbon cycling, but are amongst the least studied with regard to species composition and ecosystem functioning. This is particularly true of the Polar Regions, which are currently undergoing rapid climate change, the impacts of which are poorly understood. Compared to other latitudes, Polar sediment habitats also experience additional environmental drivers of strong seasonality and intense disturbance from iceberg scouring, which are major structural forces for hard substratum communities. This study compared sediment assemblages from two coves, near Rothera Point, Antarctic Peninsula, 67°S in order to understand the principal drivers of community structure, for the first time, evaluating composition across all size classes from mega- to micro-fauna.ResultsMorpho-taxonomy identified 77 macrofaunal species with densities of 464–16,084 individuals m−2. eDNA metabarcoding of microfauna, in summer only, identified a higher diversity, 189 metazoan amplicon sequence variants (ASVs) using the 18S ribosomal RNA and 249 metazoan ASVs using the mitochondrial COI gene. Both techniques recorded a greater taxonomic diversity in South Cove than Hangar Cove, with differences in communities between the coves, although the main taxonomic drivers varied between techniques. Morphotaxonomy identified the main differences between coves as the mollusc, Altenaeum charcoti, the cnidarian Edwardsia sp. and the polychaetes from the family cirratulidae. Metabarcoding identified greater numbers of species of nematodes, crustaceans and Platyhelminthes in South Cove, but more bivalve species in Hangar Cove. There were no detectable differences in community composition, measured through morphotaxonomy, between seasons, years or due to iceberg disturbance.ConclusionsThis study found that unlike hard substratum communities the diversity of Antarctic soft sediment communities is correlated with the same factors as other latitudes. Diversity was significantly correlated with grain size and organic content, not iceberg scour. The increase in glacial sediment input as glaciers melt, may therefore be more important than increased iceberg disturbance.

Environmental drivers of benthic community structure in a deep sub-arctic fjord system

Fjords are unique geomorphological features that are found globally along (previously) glaciated coasts. They are characteristic for the entire Norwegian coast, where growing human populations and economic development increasingly impact the associated fjord ecosystems, and accordingly basic knowledge about ecosystem structure and functioning is needed. Knowledge about benthic systems within deep basins (over 400 m) of sub-Arctic fjords is currently missing and it remains questionable whether our understanding of similarly deep temperate fjords or shallower sub-arctic fjords is directly transferable to such systems. This study aims to investigate the patterns of soft-bottom benthic communities within a northern Norwegian deep multibasin fjord system and relate them to the prevailing environmental conditions, following a sampling strategy of many-sites with one-sample each. Here we show that oxygen content of the water and organic matter gradients in the sediment, structure the benthic communities of the fjord reflecting the main basins. We found that the community of the deepest basin (>700 m) of this sub-Arctic fjord is similar to the community just outside of Tysfjord at the same depth but differ from other communities within the fjord. Furthermore, the deep basin community reflects deep communities of temperate fjords and the deep Skagerrak. The community within the innermost basin is well adapted to periodic hypoxia with low quality or degraded food supply. Our results demonstrated that fjord specific multibasin topography and the corresponding environmental factors are important drivers of ecological processes, which resulted in distinct benthic communities in each of the three basins. The management of such heterogeneous fjord ecosystems should take an adaptive approach and apply measures that take the differences of these benthic communities into account.

TRACING ORIGIN AND COLLAPSE OF HOLOCENE BENTHIC BASELINE COMMUNITIES IN THE NORTHERN ADRIATIC SEA

The shallow northern Adriatic Sea has a long history of anthropogenic impacts that reaches back many centuries. While the effects of eutrophication, overfishing, pollution, and trawling over recent decades have been extensively studied, the major ecological turnovers during the Holocene as a whole remain poorly explored. In this study, we reconstruct ecological baselines defining benthic ecosystem composition prior to major anthropogenic changes at four stations characterized by low sedimentation and millennial-scale time averaging of molluscan assemblages. We discriminate between natural and anthropogenic drivers based on (1) stratigraphic changes in the composition of molluscan communities observed in sediment cores and (2) changes in concentrations of heavy metals, pollutants, and organic enrichment. The four 1.5-m long sediment cores reach back to the Pleistocene–Holocene boundary, allowing for a stratigraphic distinction of the major sea-level phases of the Holocene. During the transgressive phase and maximum flooding, sea-level and establishment of the modern circulation pattern determined the development of benthic communities in shallow-water, vegetated habitats with epifaunal biostromes and, in deeper waters, with bryozoan meadows. After sea-level stabilization, the composition of these baseline communities remained relatively uniform and started to change markedly only with the intensification of human impacts in the late highstand, leading to a dominance of infauna and a decline of epifauna at all sites. This profound ecological change reduced species richness, increased the abundance of infaunal suspension feeders, and led to a decline of grazers and deposit feeders. We suggest that modern soft-bottom benthic communities in the northern Adriatic Sea today do not show the high geographic heterogeneity in composition characteristic of benthos prior to anthropogenic influences.

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.

Taxonomic distinctness of soft-bottoms mollusks from Gulf of Batabanó, Cuba

Taxonomic distinction is a measure of diversity that has a number of advantages that provides relevant connotation to theoretical and applied ecology. The usefulness of this type of measure as an alternative method for assessing the biodiversity of soft-bottom benthic marine ecosystems was tested using the indices of average taxonomic distinctness (Delta+) and variation in taxonomic distinctness (Lambda+) for mollusk communities of the Gulf of Batabanó (Cuba). For this purpose, inventories of soft bottom benthic mollusk species obtained in the period 1981-1985 and the years 2004/2007 were used. Both species lists were analyzed and compared at spatial and temporal scales. The taxonomic composition, between the period 1981-1985 and years 2004 and 2007, consisted of 3 classes, 20 orders, 60 families, 137 genera and 182 species observed. With the exception of the class level, a non-significant decrease of this composition in 2004 and 2007 was detected. At a spatial scale, a significant decrease in the taxonomic richness was observed in 2004. Significant differences were not detected in Delta+ and Lambda+ to time scale, but at spatial scale, results revealed significant differences that could be attributed to the combined effect of increased anthropogenic activities in the region with hurricane induced effects. These results suggest that the pair of indices, Delta+ and Lambda+, are good descriptors of the biodiversity of soft-bottom benthic mollusk communities in the Gulf of Batabanó.

Underwater observations of the giant spoon worm Ikeda taenioides (Annelida: Echiura: Ikedidae) in a subtidal soft-bottom environment in northeastern Japan, which survived tsunamis of the 2011 off the Pacific Coast of Tohoku Earthquake

Tsunamis associated with the 2011 off the Pacific Coast of Tohoku Earthquake seriously disrupted the shallow marine ecosystem along a 2000 km stretch of the Pacific coast of Japan. The effects of the 2011 tsunamis on the soft-bottom benthic community have been relatively well studied in the intertidal zone, whereas tsunami effects on the subtidal benthos remain poorly understood. Here, we investigated populations of the world’s largest spoon worm Ikeda taenioides (Annelida: Echiura: Ikedidae) in subtidal zone of Funakoshi Bay, Tohoku District, northeastern Japan. Subtidal scuba-diving surveys at two sites in the bay showed extremely long proboscises frequently extending from small holes in the sandy seafloor shortly before and soon after the tsunami disturbances. Based on morphological and molecular identification, the proboscises were revealed to be parts of I. taenioides. On 30 November 2011, 265 days after the tsunami event, many large-sized individuals with >1 m long proboscises were observed; these individuals were probably not derived from post-tsunami larval recruitment but more likely survived the tsunami disturbances. This is surprising because other sympatric megabenthos (e.g. spatangoid echinoids and venerid bivalves) and seagrass beds were almost completely destroyed (although they later recovered) by the tsunamis in this bay. The burrows of I. taenioides are known to be very deep (70–90 cm), which may have sheltered them from the impacts of the tsunamis. Our observations suggest that the effects of the 2011 tsunamis on benthos in soft sediments may differ depending on their burrowing depth.

The benthic fish assemblage of the soft-bottom community of the Duluth-Superior Harbor before and after round goby invasion (1989–2011)

Abstract The soft-bottom benthic fish community of the St. Louis River and Duluth-Superior Harbor was examined yearly (20 of 23 years) from 1989 through 2011 using bottom trawling. Catch per unit effort (CPUE) and fish lengths were used to assess the impact of the round goby, which appeared in trawl records in 1998, on benthic native fishes. Logperch ( Percina caprodes ), spoonhead sculpin ( Cottus ricei ), johnny darter ( Etheostoma nigrum ), channel catfish ( Ictlarus puncatus ), tadpole madtom catfish ( Noturus gyrinus ) and bullhead catfish ( Ictalurus spp.) plus the invasive Eurasian ruffe ( Gymnocephalus cernuus ) populations were assessed. After detection in the trawl record in 1998, round goby continued to increase in abundance through 2006. Logperch showed a 65% decline in median CPUE from 2.4 to 0.85, while johnny darter increased almost three-fold from 0.24 to 0.68 CPUE following round goby detection. Bullheads dropped from 7.5 CPUE to being virtually extirpated from the study area. However, their decline preceded round goby appearance, and was linked to the stocking of predator fish to combat the Eurasian ruffe. It is hypothesized that the presence of the Eurasian ruffe contributed to depressing the native fish population to the extent that the round goby appearance had less impact on the community. However, after 20 years of decline, the native fish appear to be rebounding due to declines in the Eurasian ruffe and round goby populations and improvements in water quality.

The Baltic Sea scale inventory of benthic faunal communities

AbstractThis study provides an inventory of the recent benthic macrofaunal communities in the entire Baltic Sea. The analyses of soft-bottom benthic invertebrate community data based on over 7000 locations in the Baltic Sea suggested the existence of 10 major communities based on species abundances and 17 communities based on species biomasses, respectively. The low-saline northern Baltic, characterized by silty sediments, is dominated by Monoporeia affinis, Marenzelleria spp., and Macoma balthica. Hydrobiidae, Pygospio elegans, and Cerastoderma glaucum dominate the community in sandy habitats off the Estonian west coast and in the southeastern and southern Baltic Sea. Deep parts of the Gulf of Finland and central Baltic Sea often experience hypoxia, and when oxygen levels in these regions recover, Bylgides sarsi was the first species to colonize. The southwestern Baltic Sea, with high salinity, has higher macrofaunal diversity compared with the northern parts. To spatially interpolate the distribution of the major communities, we used the Random Forest method. Substrate data, bathymetric maps, and modelled hydrographical fields were used as predictors. Model predictions were in good agreement with observations, quantified by Cohen's κ of 0.90 for the abundance and 0.89 in the wet weight-based model. Misclassifications were mainly associated with uncommon classes in regions with high spatial variability. Our analysis provides a detailed baseline map of the distribution of benthic communities in the Baltic Sea to be used both in science and management.