Size-selective microzooplankton grazing on the phytoplankton in the Curonian Lagoon (SE Baltic Sea)

In this study we applied dilution technique and phytoplankton size-fractionation to experimentally evaluate the differences in microzooplankton and phytoplankton community structures, grazing and growth rates between the freshwater (Nida) and brackish water (Smiltyne) parts of the Curonian Lagoon (SE Baltic Sea). We found that the microzooplankton community was able to remove up to 78% of nanophytoplankton (2–20 μm) standing stock and 130% of the total daily primary production in the brackish waters of the lagoon, and up to 83% of standing stock and 76% of the primary production of picophytoplankton (0.2–2 μm) in the freshwater part. The observed differences were attributed to the changes in ciliate community size and trophic structure, with larger nano-filterers (30-60 μm) dominating the brackish water assemblages and pico-nano filterers (<20 μm and 20–30 μm) prevailing in the freshwater part of the lagoon

Infection rates and prevalence of metazoan parasites of the non-native round goby (Neogobius melanostomus) in the Baltic Sea

Studies in the Baltic Sea have identified over 30 parasite taxa infecting the invasive round goby (Neogobius melanostomus (Pallas, 1814). In this study, we aimed at comparing parasite assemblages and infection rates (prevalence and intensity) in different populations across the invasive range in the Baltic Sea (Denmark, Lithuania, Estonia and Finland). Infection rates were 56-60% across all locations except Lithuania (28%). However, the parasite assemblages in the sampled populations were dissimilar, each location having unique parasites. In addition, many of the parasites were generalists commonly infecting native fish species. Based on the results of this study and those previously conducted in the Baltic Sea, the round goby has not retained parasites from its area of origin, but instead has been successively colonized by native generalist parasites. Although variable, overall parasite richness is still quite low around the Baltic compared to the native areas (34 vs 71 taxa, respectively). Also, prevalence and mean infection intensities in the Baltic Sea are significantly lower than in the native areas. Therefore, the invasion success of the round goby in the Baltic Sea can at least partly be attributed to enemy release, in this case shedding a significant proportion of their native parasite load.Peer reviewe

Cost-efficiency assessments of marine monitoring methods lack rigor : a systematic mapping of literature and an end-user view on optimal cost-efficiency analysis

Global deterioration of marine ecosystems, together with increasing pressure to use them, has created a demand for new, more efficient and cost-efficient monitoring tools that enable assessing changes in the status of marine ecosystems. However, demonstrating the cost-efficiency of a monitoring method is not straightforward as there are no generally applicable guidelines. Our study provides a systematic literature mapping of methods and criteria that have been proposed or used since the year 2000 to evaluate the cost-efficiency of marine monitoring methods. We aimed to investigate these methods but discovered that examples of actual cost-efficiency assessments in literature were rare, contradicting the prevalent use of the term “cost-efficiency.” We identified five different ways to compare the cost-efficiency of a marine monitoring method: (1) the cost–benefit ratio, (2) comparative studies based on an experiment, (3) comparative studies based on a literature review, (4) comparisons with other methods based on literature, and (5) subjective comparisons with other methods based on experience or intuition. Because of the observed high frequency of insufficient cost–benefit assessments, we strongly advise that more attention is paid to the coverage of both cost and efficiency parameters when evaluating the actual cost-efficiency of novel methods. Our results emphasize the need to improve the reliability and comparability of cost-efficiency assessments. We provide guidelines for future initiatives to develop a cost-efficiency assessment framework and suggestions for more unified cost-efficiency criteria

Diazotrophic cyanobacteria in planktonic food webs

Blooms of cyanobacteria are recurrent phenomena in coastal estuaries. Their maximum abundance coincides with the productive period of zooplankton and pelagic fish. Experimental studies indicate that diazotrophic, i.e. dinitrogen (N2)-fixing cyanobacterial (taxonomic order Nostocales) blooms affect zooplankton, as well as other phytoplankton. We used multidecadal monitoring data from one archipelago station (1992–2013) and ten open sea stations (1979–2013) in the Baltic Sea to explore the potential bottom-up connections between diazotrophic and non-diazotrophic cyanobacteria and phyto- and zooplankton in natural plankton communities. Random forest regression, combined with linear regression analysis showed that the biomass of cyanobacteria (both diazotrophic and non-diazotrophic) was barely connected to any of the phytoplankton and zooplankton variables examined. Instead, physico-chemical variables (salinity, temperature, total phosphorus), as well as spatial and temporal variability seemed to have more significant connections to both phytoplankton and zooplankton variables. Zooplankton variables were also connected to the biomass of phytoplankton groups other than cyanobacteria (such as chrysophytes, cryptophytes and prymnesiophytes), and phytoplankton variables had connections with the biomass of different zooplankton groups, especially copepods. Overall, negative relationships between cyanobacteria and other plankton taxa were scarcer than expected based on previous experimental studies.​​​​​​​</ul

Diazotrophic cyanobacteria in planktonic food webs

Blooms of cyanobacteria are recurrent phenomena in coastal estuaries. Their maximum abundance coincides with the productive period of zooplankton and pelagic fish. Experimental studies indicate that diazotrophic, i.e. dinitrogen (N2)-fixing cyanobacterial (taxonomic order Nostocales) blooms affect zooplankton, as well as other phytoplankton. We used multidecadal monitoring data from one archipelago station (1992–2013) and ten open sea stations (1979–2013) in the Baltic Sea to explore the potential bottom-up connections between diazotrophic and non-diazotrophic cyanobacteria and phyto- and zooplankton in natural plankton communities. Random forest regression, combined with linear regression analysis showed that the biomass of cyanobacteria (both diazotrophic and non-diazotrophic) was barely connected to any of the phytoplankton and zooplankton variables examined. Instead, physico-chemical variables (salinity, temperature, total phosphorus), as well as spatial and temporal variability seemed to have more significant connections to both phytoplankton and zooplankton variables. Zooplankton variables were also connected to the biomass of phytoplankton groups other than cyanobacteria (such as chrysophytes, cryptophytes and prymnesiophytes), and phytoplankton variables had connections with the biomass of different zooplankton groups, especially copepods. Overall, negative relationships between cyanobacteria and other plankton taxa were scarcer than expected based on previous experimental studies

Marine Strategy Framework Directive - Task Group 4 Report Food Webs

The Marine Strategy Framework Directive (2008/56/EC) (MSFD) requires that the European Commission (by 15 July 2010) should lay down criteria and methodological standards to allow consistency in approach in evaluating the extent to which Good Environmental Status (GES) is being achieved. ICES and JRC were contracted to provide scientific support for the Commission in meeting this obligation. A total of 10 reports have been prepared relating to the descriptors of GES listed in Annex I of the Directive. Eight reports have been prepared by groups of independent experts coordinated by JRC and ICES in response to this contract. In addition, reports for two descriptors (Contaminants in fish and other seafood and Marine Litter) were written by expert groups coordinated by DG SANCO and IFREMER respectively. A Task Group was established for each of the qualitative Descriptors. Each Task Group consisted of selected experts providing experience related to the four marine regions (the Baltic Sea, the North-east Atlantic, the Mediterranean Sea and the Black Sea) and an appropriate scope of relevant scientific expertise. Observers from the Regional Seas Conventions were also invited to each Task Group to help ensure the inclusion of relevant work by those Conventions. This is the report of Task Group 4 Food Webs.JRC.DDG.H.5-Rural, water and ecosystem resource

Approach for Supporting Food Web Assessments with Multi-Decadal Phytoplankton Community Analyses—Case Baltic Sea

Combining the existing knowledge on links between functional characteristics of phytoplankton taxa and food web functioning with the methods from long-term data analysis, we present an approach for using phytoplankton monitoring data to draw conclusions on potential effects of phytoplankton taxonomic composition on the next trophic level. This information can be used as a part of marine food web assessments required by the Marine Strategy Framework Directive of the European Union. In this approach, both contemporary taxonomic composition and recent trends of changes are used to assess their potential consequences for food web functioning. The approach consists of four steps: (1) long-term trend analysis of class-level and total phytoplankton biomass using generalized additive models (GAMs) and calculating average biomass share of each phytoplankton class from the total phytoplankton biomass, (2) comparing the current phytoplankton community composition and its long-term changes with non-metric ordination analysis (NMDS) of genus-level biomass, (3) describing which taxa (the most accurate taxonomic level) are primarily responsible for forming the biomass and for causing the possible changes, and (4) interpretation of the phytoplankton results to assess the potential effects on the next trophic level. Within step 4, special attention is given to the following characteristic of taxa: potential suitability or quality as food for grazers, harmfulness, size, and trophy. These characteristics are selected based on existing scientific knowledge on their relevance to the higher trophic levels. In this article, we present the concept of the suggested approach and demonstrate the phytoplankton analyses with multi-decadal monitoring data from the northern Baltic Sea. We also discuss the future development of the approach toward a food web index by combining or replacing the taxonomic analyses with functional trait-based approaches

SYKE Proficiency Test 10/2014 Phytoplankton

The Finnish Environment Institute (SYKE) organized in 2014 the fourth virtual phytoplankton proficiency test based on filmed material. A total of 39 analysts from 27 organizations and eight countries took part the test. The test material represented phytoplankton that typically occurs in boreal lakes and in the northern Baltic Sea. The test included three components: 1) phytoplankton species identification test, 2) phytoplankton counting test and 3) phytoplankton measurement of cell dimensions. Material for the lake and Baltic Sea phytoplankton identification tests consisted of 20 taxa filmed on 20 video-clips. For the phytoplankton counting test 30 video-clips, representing 30 fields of view in a microscope, were filmed. In the measurement test the cell dimensions (diameter, height/width and length) of three selected taxa were asked to be measured from the Lugol preserved sample. In the lake phytoplankton identification test altogether 81% of the participants reached the good quality target of 75% of the maximum score. The corresponding percentage in the Baltic Sea phytoplankton identification test also was 81%. The success in the counting test was excellent, and all participants performed the counting test successfully. Altogether 92% of the participants did the measurement test successfully. Majority of the participants demonstrated excellent phytoplankton identification skills and proficiency to perform phytoplankton counts and measurements. The results of the proficiency test highlighted to follow the EN 15204 guidance in the quantitative phytoplankton analysis