Browsing by Subject "brackish"

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  • Peltomaa, Elina; Hällfors, Heidi; Taipale, Sami J. (2019)
    Recent studies have clearly shown the importance of omega-3 (-3) and omega-6 (-6) polyunsaturated fatty acids (PUFAs) for human and animal health. The long-chain eicosapentaenoic acid (EPA; 20:5-3) and docosahexaenoic acid (DHA; 22:6-3) are especially recognized for their nutritional value, and ability to alleviate many diseases in humans. So far, fish oil has been the main human source of EPA and DHA, but alternative sources are needed to satisfy the growing need for them. Therefore, we compared a fatty acid profile and content of 10 diatoms and seven dinoflagellates originating from marine, brackish and freshwater habitats. These two phytoplankton groups were chosen since they are excellent producers of EPA and DHA in aquatic food webs. Multivariate analysis revealed that, whereas the phytoplankton group (46%) explained most of the differences in the fatty acid profiles, habitat (31%) together with phytoplankton group (24%) explained differences in the fatty acid contents. In both diatoms and dinoflagellates, the total fatty acid concentrations and the -3 and -6 PUFAs were markedly higher in freshwater than in brackish or marine strains. Our results show that, even though the fatty acid profiles are genetically ordered, the fatty acid contents may vary greatly by habitat and affect the -3 and -6 availability in food webs.
  • Virta, Leena; Soininen, Janne; Norkko, Alf (2020)
    Aim Global biodiversity loss has raised interest in understanding variation in diversity at different scales. In particular, studies conducted across large spatial gradients are crucial, because they can increase perspectives on how ecological patterns change relative to environmental factors and facilitate predictions of possible responses to environmental change. We explored the full extent of a brackish sea to test the hypotheses that: (a) benthic communities are defined by the limited ranges of species, controlled by varying drivers along a large environmental gradient; (b) the responses of taxonomic and functional community composition and turnover to the environmental gradient are different, thus highlighting the need to include both measures in ecological studies; and (c) diversity reaches the minimum at intermediate salinities (Remane curve) owing to the low adaptation of freshwater and marine species. Location A large environmental and spatial gradient spanning the entire Swedish coastline (c. 2,300 km; salinity 1.2-27.6), the Baltic Sea. Time period August 2018. Major taxa studied Benthic diatoms. Methods We assessed environmental drivers for the communities and calculated the taxonomic and functional alpha and beta diversity along the gradient. We also compared the taxonomic and functional composition and diversity of communities among areas with different salinity. Results We found support for the hypothesis of limited species ranges, because taxonomic beta diversity, mainly induced by changes in salinity and climate, was high, whereas functional beta diversity remained considerably lower, and the composition and diversity of communities, in addition to environmental drivers controlling the communities, differed between regions with different salinity. The lowest taxonomic diversity was found at intermediate salinities of 5-6. Main conclusions These findings advance understanding of large-scale patterns of benthic diversity, emphasize the importance of large gradient studies for a better understanding of general ecological patterns and highlight the vulnerability of brackish water ecosystems as ecologically important tipping-point realms.
  • Kotta, Jonne; Kotta, Ilmar; Bick, Andreas; Bastrop, Ralf; Väinölä, Risto (2015)
    An as-yet-undescribed, non-indigenous polychaete species was found at very high densities in the eastern part of the Baltic Sea in Estonia in 2012. The species belongs to the sabellid genus Laonome Malmgren, 1866, but it could not be assigned to any of the previously described species. To date, the species has established a stable population after surviving a notably cold winter (2012/2013). To study the local distribution and abundance of the species, a spatial grid with some stations repeated seasonally and interannually was sampled in a quantitative manner. Based of the survey data and available environmental data, the variables that contributed significantly to explaining variation in the abundance of the polychaete were determined using the Boosted Regression Trees modelling approach. Molecular barcodes to characterize the identity of the species were also established. The abundance of Laonome sp. exhibited strong seasonal variation, peaking between July and November. Besides seasonality, the quantity of decomposed microalgae in the sediment and wave exposure best explained the variation in abundance. Laonome sp. is now well-established in the Baltic Sea and locally reached high densities in low salinity areas. This non-indigenous polychaete may potentially modify sediment morphology and chemistry and disrupt the natural infaunal communities. Laonome sp. could displace or even completely eliminate some species currently present in the study area and beyond if it spreads; however, it could also facilitate currently-present species through the provision of alternative substrate and/or food. Given its persistence and high abundance in Parnu Bay, colonization of other low-salinity areas of the Baltic Sea can be expected.
  • Aarnio, Sonja; Soininen, Janne (2021)
    Local biodiversity has traditionally been estimated with taxonomic diversity metrics such as species richness. Recently, the concept of biodiversity has been extended beyond species identity by ecological traits determining the functional role of a species in a community. This interspecific functional diversity typically responds more strongly to local environmental variation compared with taxonomic diversity, while taxonomic diversity may mirror more strongly dispersal processes compared with functional metrics. Several trait-based indices have been developed to measure functional diversity for various organisms and habitat types, but studies of their applicability on aquatic microbial communities have been underrepresented. We examined the drivers and covariance of taxonomic and functional diversity among diatom rock pool communities on the Baltic Sea coast. We quantified three taxonomic (species richness, Shannon's diversity, and Pielou's evenness) and three functional (functional richness, evenness, and divergence) diversity indices and determined abiotic factors best explaining variation in these indices by generalized linear mixed models. The six diversity indices were highly collinear except functional evenness, which merely correlated significantly with taxonomic evenness. All diversity indices were always explained by water conductivity and temperature-sampling month interaction. Taxonomic diversity was further consistently explained by pool distance to the sea, and functional richness and divergence by pool location. The explained variance in regression models did not markedly differ between taxonomic and functional metrics. Our findings do not clearly support the superiority of neither set of diversity indices in explaining coastal microbial diversity, but rather highlight the general overlap among the indices. However, as individual metrics may be driven by different factors, the greatest advantage in assessing biodiversity is nevertheless probably achieved with a simultaneous application of the taxonomic and functional diversity metrics.