Multidecadal time series of satellite-detected accumulations of cyanobacteria in the Baltic Sea

Cyanobacteria, primarily of the species \textit{Nodularia spumigena}, form extensive surface accumulations in the Baltic Sea in July and August, ranging from diffuse flakes to dense surface scums. The area of these accumulations can reach ~ 200 000 km². We describe the compilation of a 35-year-long time series (1979–2013) of cyanobacteria surface accumulations in the Baltic Sea using multiple satellite sensors. This appears to be one of the longest satellite-based time series in biological oceanography. The satellite algorithm is based on remote sensing reflectance of the water in the red band, a measure of turbidity. Validation of the satellite algorithm using horizontal transects from a ship of opportunity showed the strongest relationship with phycocyanin fluorescence (an indicator of cyanobacteria), followed by turbidity and then by chlorophyll <i>a</i> fluorescence. The areal fraction with cyanobacteria accumulations (FCA) and the total accumulated area affected (TA) were used to characterize the intensity and extent of the accumulations. The fraction with cyanobacteria accumulations was calculated as the ratio of the number of detected accumulations to the number of cloud-free sea-surface views per pixel during the season (July–August). The total accumulated area affected was calculated by adding the area of pixels where accumulations were detected at least once during the season. The fraction with cyanobacteria accumulations and TA were correlated (<i>R</i>² = 0.55) and both showed large interannual and decadal-scale variations. The average FCA was significantly higher for the second half of the time series (13.8%, 1997–2013) than for the first half (8.6%, 1979–1996). However, that does not seem to represent a long-term trend but decadal-scale oscillations. Cyanobacteria accumulations were common in the 1970s and early 1980s (FCA between 11–17%), but rare (FCA below 4%) during 1985–1990; they increased again starting in 1991 and particularly in 1999, reaching maxima in FCA (~ 25%) and TA (~ 210 000 km²) in 2005 and 2008. After 2008, FCA declined to more moderate levels (6–17%). The timing of the accumulations has become earlier in the season, at a mean rate of 0.6 days per year, resulting in approximately 20 days advancement during the study period. The interannual variations in FCA are positively correlated with the concentration of chlorophyll <i>a</i> during July–August sampled at the depth of ~ 5 m by a ship of opportunity, but interannual variations in FCA are more pronounced as the coefficient of variation is over 5 times higher

Nitrogen and the Baltic Sea: Managing Nitrogen in Relation to Phosphorus

The Baltic is a large, brackish sea (4 x 105 km2) extending from 54ÅN to ~66ÅN, with a fourfold larger drainage area (population 8 x 107). Surface salinity (2 to 8 PSU) and hence biodiversity is low. In the last century, annual nutrient loads increased to 106 metric tons N and 5 x104 ton P. Eutrophication is evident in the N-limited south, where cyanobacteria fix 2 to 4 x 105 ton N each summer, Secchi depths have been halved, and O2-deficient bottom areas have spread. Production remains low in the P-limited north. In nutrient-enriched coastal areas, phytoplankton blooms, toxic at times, and filamentous macroalgae reduce amenity values. Loads need to be reduced of both N, to reduce production, and P, to limit N-fixing cyanobacterial blooms. When large N-load reductions have been achieved locally, algal biomass has declined. So far, P loads have been reduced more than N loads. If this continues, a P-limited Baltic proper may result, very different from previous N-limited conditions. Reaching the management goal of halved anthropogenic N and P loads at minimum cost will require better understanding of biogeochemical nutrient cycles, economic evaluation of proposed measures, and improved stakeholder participation

Benthic-pelagic coupling and trophic relationships in northern Baltic Sea food webs

Understanding marine ecosystem structure and functioning is crucial in supporting sustainable management of natural resources and monitoring the health of marine ecosystems. The current study utilized stable isotope (SI) mixing models and trophic position models to examine energy flow, trophic relationships, and benthic-pelagic coupling between food web components. Roughly 1900 samples from different trophic levels in the food web, collected during 2001-2010 from four northern and central sub-basins of the Baltic Sea, were analyzed for SI ratios of carbon and nitrogen. Trophic structure of the food webs among the sub-basins was consistent, but there were differences between the proportions of energy in different trophic levels that had originated from the benthic habitat. Mysids and amphipods served as important links between the benthic and pelagic ecosystems. Much (35-65%) of their energy originated from the benthic zone but was transferred to higher trophic levels in the pelagic food web by consumption by herring (Clupea harengus). One percent to twenty-four percent of the energy consumption of apex seal predators (Halichoerus grypus and Pusa hispida) and predatory fish (Salmo salar) was derived from benthic zone. Diets of mysids and amphipods differed, although some overlap in their dietary niches was observed. The food web in the Gulf of Finland was more influenced by the benthic subsystem than food webs in the other sub-basins. The baseline levels of delta C-13 and delta N-15 differed between sub-basins of the Baltic Sea, indicating differences in the input of organic matter and nutrients to each sub-basin.peerReviewe

Polychaete invader enhances resource utilization in a species-poor system

Ecosystem consequences of biodiversity change are often studied from a species loss perspective, while the effects of invasive species on ecosystem functions are rarely quantified. In this experimental study, we used isotope tracers to measure the incorporation and burial of carbon and nitrogen from a simulated spring phytoplankton bloom by communities of one to four species of deposit-feeding macrofauna found in the species-poor Baltic Sea. The recently invading polychaete Marenzelleriaarctia, which has spread throughout the Baltic Sea, grows more rapidly than the native species Monoporeia affinis, Pontoporeia femorata (both amphipods) and Macoma balthica (a bivalve), resulting in higher biomass increase (biomass production) in treatments including the polychaete. Marenzelleria incorporated and buried bloom material at rates similar to the native species. Multi-species treatments generally had higher isotope incorporation, indicative of utilization of bloom material, than expected from monoculture yields of the respective species. The mechanism behind this observed over-yielding was mainly niche complementarity in utilization of the bloom input, and was more evident in communities including the invader. In contrast, multi-species treatments had generally lower biomass increase than expected. This contrasting pattern suggests that there is little overlap in resource use of freshly deposited bloom material between Marenzelleria and the native species but it is likely that interference competition acts to dampen resulting community biomass. In conclusion, an invasive species can enhance incorporation and burial of organic matter from settled phytoplankton blooms, two processes fundamental for marine productivity

Provision of aquatic ecosystem services as a consequence of societal changes: The case of the Baltic Sea

Aquatic ecosystem services are important for human wellbeing, but they are much less studied than terrestrial ecosystem services. The objectives of this study are to broaden, itemize and exemplify the human-nature interactions in modeling the future provision of aquatic ecosystem services. We include shared socioeconomic and representative concentration pathways, used extensively in climate research, as drivers of change for the future development of the Baltic Sea. Then we use biogeochemical and ecosystem models to demonstrate the future development of exemplary supporting, provisioning and cultural ecosystem services for two distinct combinations of regionally downscaled global climate and socioeconomic futures. According to the model simulations, the two global futures ("Sustainable well-being" vs. "Fossil-fuelled development") studied lead to clearly deviating trajectories in the provision of marine ecosystem services. Under the "Sustainable well-being"-scenario primary production decreases by 20%, catches of demersal fish increases and the recreation opportunities increase significantly by the end of the ongoing century. Under the "fossil-fuelled development"-scenario primary production doubles, fisheries focus on less valued pelagic fish and the recreation possibilities will decrease. Long-term projections of aquatic ecosystem services prepared for alternative global socioeconomic futures can be used by policy makers and managers to adaptively and iteratively adjust mitigation and adaptation effort with plausible future changes in the drivers of water pollution.Peer reviewe

Directional genetic selection by pulp mill effluent on multiple natural populations of three-spined stickleback (Gasterosteus aculeatus)

Contamination can cause a rapid environmental change which may require populations to respond with evolutionary changes. To evaluate the effects of pulp mill effluents on population genetics, we sampled three-spined sticklebacks (Gasterosteus aculeatus) near four pulp mills and four adjacent reference sites and analyzed Amplified Fragment Length Polymorphism (AFLP) to compare genetic variability. A fine scale genetic structure was detected and samples from polluted sites separated from reference sites in multidimensional scaling plots (P < 0.005, 1000 permutations) and locus-by-locus Analysis of Molecular Variance (AMOVA) further confirmed that habitats are significantly separated (FST = 0.021, P < 0.01, 1023 permutations). The amount of genetic variation between populations did not differ between habitats, and populations from both habitats had similar levels of heterozygosity (polluted sites Nei’s Hs = 0.11, reference sites Nei’s Hs = 0.11). Still, pairwise FST: s between three, out of four, pairs of polluted-reference sites were significant. A FST-outlier analysis showed that 21 (8.4%) loci were statistically different from a neutral distribution at the P < 0.05 level and therefore indicated to be under divergent selection. When removing 13 FST-outlier loci, significant at the P < 0.01 level, differentiation between habitats disappeared in a multidimensional scaling plot. In conclusion, pulp mill effluence has acted as a selective agent on natural populations of G. aculeatus, causing a convergence in genotype composition change at multiple sites in an open environment

EurA1c: the European HbA1c Trial to Investigate the Performance of HbA1c Assays in 2166 Laboratories across 17 Countries and 24 Manufacturers by Use of the IFCC Model for Quality Targets

Background: A major objective of the IFCC Committee on Education and Use of Biomarkers in Diabetes is to generate awareness and improvement of HbA1c assays through evaluation of the performance by countries and manufacturers. Methods: Fresh whole blood and lyophilized hemolysate specimens manufactured from the same pool were used by 17 external quality assessment organizers to evaluate analytical performance of 2166 laboratories. Results were evaluated per country, per manufacturer, and per manufacturer and country combined according to criteria of the IFCC model for quality targets. Results: At the country level with fresh whole blood specimens, 6 countries met the IFCC criterion, 2 did not, and 2 were borderline. With lyophilized hemolysates, 5 countries met the criterion, 2 did not, and 3 were borderline. At the manufacturer level using fresh whole blood specimens, 13 manufacturers met the criterion, 8 did not, and 3 were borderline. Using lyophilized hemolysates, 7 manufacturers met the criterion, 6 did not, and 3 were borderline. In both country and manufacturer groups, the major contribution to total error derived from between-laboratory variation. There were no substantial differences in performance between groups using fresh whole blood or lyophilized hemolysate samples. Conclusions: The state of the art is that 1 of 20 laboratories does not meet the IFCC criterion, but there are substantial differences between country and between manufacturer groups. Efforts to further improve quality should focus on reducing between-laboratory variation. With some limitations, fresh whole blood and well-defined lyophilized specimens are suitable for purpose

Could Seals Prevent Cod Recovery in the Baltic Sea?

Fish populations are increasingly affected by multiple human and natural impacts including exploitation, eutrophication, habitat alteration and climate change. As a result many collapsed populations may have to recover in ecosystems whose structure and functioning differ from those in which they were formerly productive and supported sustainable fisheries. Here we investigate how a cod (Gadus morhua) population in the Baltic Sea whose biomass was reduced due to a combination of high exploitation and deteriorating environmental conditions might recover and develop in the 21st century in an ecosystem that likely will change due to both the already started recovery of a cod predator, the grey seal Halichoerus grypus, and projected climate impacts. Simulation modelling, assuming increased seal predation, fishing levels consistent with management plan targets and stable salinity, shows that the cod population could reach high levels well above the long-term average. Scenarios with similar seal and fishing levels but with 15% lower salinity suggest that the Baltic will still be able to support a cod population which can sustain a fishery, but biomass and yields will be lower. At present knowledge of cod and seal interactions, seal predation was found to have much lower impact on cod recovery, compared to the effects of exploitation and salinity. These results suggest that dual management objectives (recovery of both seal and cod populations) are realistic but success in achieving these goals will also depend on how climate change affects cod recruitment