Biodiversity gradient in the Baltic Sea: a comprehensive inventory of macrozoobenthos data

Abstract

In the Helsinki Commission Red List project 2009-2012, taxonomic and distributional data of benthic (macro) invertebrates were compiled by the present authors in a comprehensive checklist of the Baltic Sea fauna. Based on the most recent and comprehensive data, this paper presents the diversity patterns observed among benthic invertebrates in the Baltic Sea. As expected, the total number of species per sub-region generally declined along the salinity gradient from the Danish Straits to the northern Baltic Sea. This relationship is well known from the Baltic Sea and has resulted in a general assumption of an exponentially positive relationship between species richness and salinity for marine species, and a negative relationship for freshwater species. In 1934, Remane produced a diagram to describe the hypothetical distribution of benthic invertebrate diversity along a marine-freshwater salinity gradient. Our results clearly indicated the validity of this theory for the macrozoobenthic diversity pattern within the Baltic Sea. Categorisation of sub-regions according to species composition showed both separation and grouping of some sub-regions and a strong alignment of similarity patterns of zoobenthic species composition along the salinity gradient.

Variation in benthic long-term data of transitional waters: Is interpretation more than speculation?

“…Salinity is considered the key factor for community changes at different spatial scales along the Baltic Sea [6, 10]. Our results confirm that on temporal scales too variability in salinity is an important driver for variation in the benthic community.…”

Spatial pattern of hydrolittoral rock encrusting assemblages along the salinity gradient of the Baltic Sea

“…Similar correlation between the salinity and the species richness and abundance of encrusting assemblages was noted for other taxonomic and functional groups (e.g. Darr et al, 2014;Zettler et al, 2014). Among the environmental variables we studied (including temperature, mean rock size, wave exposure or percent coverage by fauna), salinity showed the strongest relationship with the large-scale pattern of encrusting assemblages.…”

“…Comparative measurement of biological parameters describing encrusting assemblages inhabiting the Baltic Sea hydrolittoral and littoral zones (such as species richness, abundance, diversity, percentage cover of fauna) indicated the significant role of local dispersal limitations in encrusting species composition and a strong influence of nearby biotopes. Table 2 The results of the analysis of covariance (ANCOVA) testing the effects of salinity and habitat on the basic community parameters (significant 636 differences are highlighted in bold) where habitat was used as a grouping factor while salinity as covariate Over the scale of the entire Baltic Sea, spatial species distribution is controlled mainly by the steep salinity gradient (Herkül et al, 2006;Zettler et al, 2014), which, according to the results of this study, is also observed in our data and matched our predictions. Along the gradient of increasing salinity, the spatial trends in the hydrolittoral zone, including species composition and increased diversity of encrusting assemblages, were found to be similar to those reported for other macrobenthic communities from deeper regions of the Baltic Sea (Bonsdorff & Pearson, 1999;Westerbom et al, 2002) and in particular, as this study clearly indicated, the nearby littoral.…”

“…Encrusting fauna is defined here as all sessile animals attached to the sampled rocks. The results of previous studies suggest that the effect of low salinity [leading to a lower number of species, as found in the brackish water littoral zone (see Zettler et al, 2014)], would have a similar effect on hydrolittoral encrusting assemblages. We hypothesize that the large-scale spatial pattern of the structure of hydrolittoral encrusting assemblages (measured in terms of species composition, number and abundance) along the salinity gradient would be similar to large-scale distribution trends found for other Baltic Sea ecological formations (e.g.…”

Phylogenetic Signals of Salinity and Season in Bacterial Community Composition Across the Salinity Gradient of the Baltic Sea

“…This is in accordance with the results of our previous study in which only the July data were considered (Herlemann et al, 2011). The absence of a decline in bacterial diversity in the brackish waters of the Baltic Sea contradicts Remane’s criteria of diversity in the Baltic Sea, deduced from benthic invertebrates, which included a species minimum in the brackish zone (Remane, 1934; Zettler et al, 2014). Deviations from the mesohaline species-minimum proposed for macrozoobenthos have also been noted in other estuaries for bacterial communities (Crump et al, 2004; Hewson and Fuhrman, 2004), zooplankton (Laprise and Dodson, 1994), phytoplankton (Muylaert et al, 2009; Schubert et al, 2011), ciliates (Dolan and Gallegos, 2001), and protists (Telesh et al, 2010).…”