Distribution and invasion ecology of Marenzelleria viridis in the Estonian Coastal Waters

The habitat selection and invasion of a new polychaete Marenzelleria viridis is described. Up to now the species has Iow biomass and abundance values in Estonian coastal waters. M. viridis prefers gravel substrate. The increase in the abundance of M. viridis coincides with the decline of that of another polychaete, Nereis diversicolor, in uniform habitats but not in the patchy environment. lt is likely that M. viridis may become a numerically dominant species in the zoobenthos of the region in the following years

Impact of eutrophication and biological invasions on the structure and functions of benthic macrofauna

http://www.ester.ee/record=b1422327*es

Modelling habitat range and seasonality of a new, non-indigenous polychaete Laonome sp (Sabellida, Sabellidae) in Parnu Bay, the north-eastern Baltic Sea

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.Peer reviewe

Disturbance-related patterns in unstable rocky benthic habitats of the north-eastern Baltic coast

Distinct patterns of benthic flora and fauna are produced when unstable rocky substrata are disturbed by water motion. This study investigated occurrence of disturbance-related patterns in benthic boulder habitats on the north-eastern Baltic coast. Sessile assemblages, mostly algae on tops of boulders and barnacles and bryozoans underneath, were found to differ between small (50–150 cm2 upperside surface area) and large (200–800 cm2) boulders. Densities of motile gammaridean amphipods were negatively correlated with boulder size. These patterns may be due to small boulders being displaced by water motion more frequently than large ones. Most of the barnacle shells/tests were remnant empty ones, and the proportion of empty tests and living barnacles was similar underneath small and large boulders, suggesting that degradation/removal of empty tests was not influenced by disturbance associated with boulder size. There was no consistent evidence of algae being affected by boulder size, but the tops of boulders had less algae than the edges, a pattern that is typically associated with high rates of overturning. Confirmation of disturbance as having caused these patterns and thus being an important process for structuring benthic biota in this region could be achieved by further manipulative experimentation

The invasive amphipod Gammarus tigrinus Sexton, 1939 displaces native gammarid amphipods from sheltered macrophyte habitats of the Gulf of Riga

The North-American amphipod Gammarus tigrinus Sexton, 1939 is a successful invader in European waters due to its high reproductive potential and tolerance to severe environmental conditions and various pollutants. In this study, we followed the invasion and establishment of this exotic species in a species-poor ecosystem of the northern Baltic Sea. Two years after the establishment of G. tigrinus, over half of the sampling sites were occupied exclusively by G. tigrinus, whereas G. tigrinus coexisted with native gammarids in only one tenth of all sites. There was a clear separation of habitat occupancy between native species and G. tigrinus in terms of abiotic environment and macrophytic habitat. G. tigrinus preferred shallow sheltered areas dominated by vascular plants, while native species mainly occurred in more exposed, deeper habitats with phaeophytes and rhodophytes. In its suboptimal habitats, G. tigrinus exhibited moderate abundances, which allowed for the coexistence of native gammarids and the invasive gammarid. Since its establishment, the abundance of G. tigrinus has showed no signs of decline, with abundances exceeding almost fifteen times those of native gammarids at some locations. The results suggest that, irrespective to the competitive superiority of G. tigrinus over the native gammarids, the invasive G. tigrinus does not monopolize the entire coastal area of the northern Baltic Sea but mostly outcompetes native species in its favoured habitats.

Competition for food between the introduced polychaete Marenzelleria viridis (Verrill) and the native amphipod Monoporeia affinis Lindström in the Baltic

Abstract Since 1985 the spionid polychaete Marenzelleria viridis (Verrill) has invaded large parts of the Baltic Sea. In deeper softbottom habitats (>10 m) a marked long-term decrease of the native amphipod Monoporeia affinis has been noted and is presently associated with the establishment of the polychaete. One plausible explanation is that the polychaetes and the amphipods are competing for food resources as both are deposit feeding animals and likely to share similar food resources. Interspecific competition for food between the polychaete and the amphipod was studied in a laboratory experiment. Two year classes (0y+,1y+) of the amphipods were kept at various densities, with and without added food resources, with and without the polychaete, in microcosms with sediment and continuous supply of cooled water for 2 months. The polychaetes did not have any effect on mortality in the amphipods. 4-way ANOVA showed that food addition, density of amphipods and presence of the polychaete had a significant effect on the growth of amphipods of different age classes. 1y+ amphipods showed increased growth with added food and this increase was density-dependent in the absence of the polychaetes but not in their presence. The polychaetes reduced the growth of 1y+ amphipods at natural densities (2000 ind m À 2 ) by 60%, but had no clear effects on the growth of juveniles. It is concluded that lower amphipod growth in the presence of M. viridis was caused by competition for food and is likely to affect the population of M. affinis in deep soft-bottom habitats of the northern Baltic Sea.

Testing the concept of green infrastructure at the Baltic Sea scale to support an ecosystem-based approach to management of marine areas

The concept of Green Infrastructure (GI) can facilitate integration of ecological considerations and ecosystem service mapping into spatial planning. GI has been introduced in EU policy as a key tool for implementing the objectives of the EU Biodiversity Strategy 2020 on halting the loss of biodiversity as well as addressing other global environmental problems. Unlike terrestrial ecosystems, mapping of marine GI is still in infancy. Here, application of GI concept in mapping was developed and tested for a large marine region, the Baltic Sea, using existing regional spatial data sets on the distribution of different ecosystem components. Using a qualitative valuation approach, experts assessed 36 marine ecosystem components with respect to their relevance for six ecological value criteria and ten ecosystem services. Then, maps representing the ecological value of Baltic Sea ecosystems and their potential supply of ecosystem services were developed based on a hierarchical aggregation structure, designed to avoid double-counting of features that appeared in many data layers. Finally, results of the ecological value and ecosystem service supply mapping were integrated into the marine GI map. These pioneering results are used to discuss how marine GI mapping can support the ecosystem-based approach in MSP, by improving the knowledge base on the roles and connectedness of ecosystem components. Applied at the transboundary regional scale, as here, the GI concept can support cross-border coherence in spatial planning and provide practical management solutions to improve connectivity and functioning of MPA networks, or develop sustainable planning solutions of marine space

What are the effects of macroalgal blooms on the structure and functioning of marine ecosystems? A systematic review protocol

Abstract Background Anthropogenic activities are believed to have caused an increase in the magnitude, frequency, and extent of macroalgal blooms in marine and estuarine environments. These blooms may contribute to declines in seagrasses and non-blooming macroalgal beds, increasing hypoxia, and reductions in the diversity of benthic invertebrates. However, they may also provide other marine organisms with food and habitat, increase secondary production, and reduce eutrophication. The objective of this systematic review will be to quantify the positive and negative impacts of anthropogenically induced macroalgal blooms in order to determine their effects on ecosystem structure and functioning, and to identify factors that cause their effects to vary. Methods We will search a number of online databases to gather empirical evidence from the literature on the impacts of macroalgal blooms on: (1) species richness and other univariate measures of biodiversity; (2) productivity and abundance of algae, plants, and animals; and (3) biogeochemical cycling and other flows of energy and materials, including trophic interactions and cross-ecosystem subsidies. Data from relevant studies will be extracted and used in a random effects meta-analysis in order to estimate the average effect of macroalgal blooms on each response of interest. Where possible, sub-group analyses will be conducted in order to evaluate how the effects of macroalgal blooms vary according to: (1) which part of the ecosystem is being studied (e.g. which habitat type, taxonomic group, or trophic level); (2) the size of blooms; (3) the region in which blooms occurred; (4) background levels of ecosystem productivity; (5) physical and chemical conditions; (6) aspects of study design and quality (e.g. lab vs. field, experimental vs. observational, degree of replication); and (7) whether the blooms are believed to be anthropogenically induced or not

The effects of exotic seaweeds on native benthic assemblages: variability between trophic levels and influence of background environmental and biological conditions

Abstract Background Biological invasions are among the most severe threats to marine biodiversity. The impacts of introduced seaweeds on native macroalgal assemblages have been thoroughly reviewed. In contrast, no attempt has been made to synthesize the available information on the effects of exotic seaweeds on other trophic levels. In addition, it has not been clarified whether the effects of introduced seaweeds on native assemblages vary according to background physical and biological conditions. Methods This protocol provides details of our proposed method to carry out a systematic review aiming to identify and synthesize existing knowledge to answer the following primary questions: a) how does the impact of the presence of exotic seaweeds on native primary consumers (across trophic levels) compare in magnitude and extent to that observed on native primary producers (same trophic level)?; b) does the intensity of the effects of the presence of exotic seaweeds on native benthic ecosystems vary along a gradient of human disturbance (i.e. from urban/industrial areas to extra-urban areas to pristine areas)