The Baltic Sea scale inventory of benthic faunal communities

ICES Journal of Marine Science ICES Journal of Marine Science (2016), 73(4), 1196– 1213. doi:10.1093/icesjms/fsv265 Original Article The Baltic Sea scale inventory of benthic faunal communities Mayya Gogina 1*, Henrik Nygård 2, Mats Blomqvist3, Darius Daunys4, Alf B. Josefson 5, Jonne Kotta6, Alexey Maximov 7, Jan Warzocha 8, Vadim Yermakov 9, Ulf Gräwe1, and Michael L. Zettler 1 1 *Corresponding author: tel: +49 381 5197 393; fax: +49 381 5197 211; e-mail: Gogina, M., Nygård, H., Blomqvist, M., Daunys, D., Josefson, A. B., Kotta, J., Maximov, A., Warzocha, J., Yermakov, V., Gräwe, U., and Zettler, M. L. The Baltic Sea scale inventory of benthic faunal communities. – ICES Journal of Marine Science, 73: 1196 –1213. Received 23 July 2015; revised 9 December 2015; accepted 14 December 2015; advance access publication 26 January 2016. This 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 k 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. Keywords: Baltic Sea, community analysis, large scale, macrozoobenthos, Random Forest, spatial distribution. Introduction In the recent decades, there has been a marked increase in benthic habitat mapping, largely inspired by the development and implementation of various research and monitoring programmes, management plans, and legislations, such as the 1992 EU Habitats Directive. This has resulted in an exponential accumulation of data hitherto stored as different non-standardized national datasets. Here for the first time, we bring much of these datasets together and harmonize them to address management issues on the large Baltic Sea scale. Similar large-scale efforts were previously reported for the North Sea in Rees et al. (2007), for the Barents Sea in Anisimova et al. (2010). The focus of our study was identification, description, and basin scale mapping of major benthic macrofauna community distribution in the Baltic Sea. A number of works were previously published, describing and mapping the benthic macrofauna communities in different subbasins of the Baltic Sea (e.g. Warzocha, 1995; Laine, 2003; Glockzin and Zettler, 2008; Gogina et al., 2010). However, # International Council for the Exploration of the Sea 2016. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited. Leibniz Institute for Baltic Sea Research (IOW), Warnemünde, Seestr. 15, 18119 Rostock, Germany Marine Research Centre, Finnish Environment Institute SYKE, PO Box 140, FI-00251 Helsinki, Finland 3 Hafok AB, 179 61 Stenhamra, Sweden 4 Coastal Research and Planning Institute, Klaipeda University, H. Manto Str. 84, LT-92294 Klaipėda, Lithuania 5 Department of Bioscience, Aarhus University, Frederiksborgvej 399, 4000 Roskilde, Denmark 6 Estonian Marine Institute, University of Tartu, Mäealuse 14, 12618 Tallinn, Estonia 7 Zoological Institute Russian Academy of Science, Universitetskaja nab. 1, 199034 St Petersburg, Russia 8 National Marine Fisheries Research Institute, ul. Kołła˛taja 1, 81-332 Gdynia, Poland 9 Latvian Institute of Aquatic Ecology, Daugavgrı̄vas Str. 8, LV-1048 Riga, Latvia 2 1197 The Baltic Sea scale inventory of benthic faunal communities Methods Joint dataset The standardized dataset comprised over 1000 taxa from over 7000 locations (17 000 visit events) mostly sampled in period 2000–2013 for species abundance and partly for biomass (Figure 1). Overall, 1176 taxonomic units (accepted in the World register of Marine Species WoRMS) were included in the final dataset. Over 70% of the samples were collected from May to July and therefore, the dataset is biased towards spring and early summer. GIS databases were utilized for collating the distribution of benthic macrofauna covering the entire Baltic Sea basin. Most data (77%) were collected with a van Veen grab (covering a bottom area of 0.1 m2), 1 –3 replicates per sampling were taken, sieved on a 1 mm mesh, preserved in 4% buffered formaldehyde–seawater solution, and identified in the laboratory to the lowest taxonomic level possible. Table 1 provides more details including specifications and the area covered by each laboratory. All species abundance and biomass data were recalculated to the area of 1 m2. Biomass records were available for 75% of the samples. Wet weight (including calcareous structures, without tubes) were only available for 2943 (39%) locations and ash-free dry weight for 2241 (29.7%) locations. Only wet weight were used for further analysis. Where only dry or ash-free dry weight data were available, in-house (IOW) biomass data conversion factors were used to calculate wet weight. The conversion factors are available upon request. For the analyses, we used a 5 × 5 km grid (matching one-quarter of the European Environment Agency EEA 10 km reference grid size). Inner coastal fjords, estuaries, and lagoon regions were omitted from the analysis due to higher macrofauna variability, and because these areas contained a large part of freshwater organisms not representative for the broadscale picture of the entire Baltic. Average taxonomic unit abundances were calculated to account for all samples within one grid cell. Biomass records were obtained for 2268 of 5 × 5 km grid cells. Such aggregation of data neglects fine-scale spatial differences in the community structure and ignores temporal variation within the study period (...truncated)