Poster session 2022

Marine Protected Areas (MPAs) were established in Kenya and Tanzania to mitigate overfishing; however, the degree of connectivity between them is still obscure. For this project, I studied the genetic flow of the overfished species Siganus sutor at different MPAs in Kenya and Zanzibar as proxy of connectivity. To study the population structure, the mitochondrial cytochrome oxidase subunits I (COI) gene was used. My results show a good genetic flow between the MPAs in all the studied sites with 0 genetic differences between populations, revealing good connectivity between Kenya and Zanzibar. Thus, the whole area should be considered one single stock. My outcomes emphasized the importance of establishing MPAs beyond borders and, although steps forward have already been made, more international agreements and common policies should be established to safeguard future fish stocks in the area

¹Stockholm University

Whitefish (Coregonus maraena) has historically been one of the most important target species of coastal fisheries in the Baltic Sea. Over the second half of the 20th century, total catches of this salmonid have declined which is suggested to be caused by overexploitation and spawning habitat loss. However, a collapse of whitefish populations in the 1990s may not be fully explained by these factors. We therefore suggest thiamin (vitamin B1) deficiency as a potential candidate cause. Using whitefish catches of standardized surveys of coastal fish populations provided by the open-access KUL-database, the contemporary trends of whitefish abundance along the Swedish coast were investigated. In addition, three anadromous whitefish populations were sampled during spawning and variables attributed to an individual’s thiamin status were analysed. This study together with literature data shows that the collapse of whitefish in the 1990s coincides with high incidences of thiamin deficiency syndrome in Baltic salmon (M74), suggesting that whitefish may have been similarly affected. Since then, whitefish populations have stabilized at low abundances. Results illustrate a large variation in total thiamin in eggs and muscle tissue. Maternal condition factor shows positive correlations with total thiamin of eggs and muscle tissue. Whether the observed variation in thiamin is natural or indicative of disturbances in maternal transfer of thiamin are evaluated and discussed. This study affirms the need for additional investigation on the potential thiamin deficiency of whitefish and its effect on whitefish abundance. Furthermore, whitefish-specific management practices as well as new survey designs are needed.

¹Linnaeus University, Kalmar, Sweden

Even large inflows of oxygen-rich seawater to the Baltic Proper have in recent decades given only short-lived relief from oxygen deficiency below the halocline. We analyse long-term changes in oxygen deficiency and calculate the ‘‘total oxygen debt’’ sumOD, the oxygen required to oxidize the hydrogen sulphide (H₂S) and ammonium (NH₄⁺) that builds up during stagnation periods. Since the early 1990s, oxygen below 65 m has gradually decreased during successive stagnation periods, and the sumOD has increased, with NH₄⁺ more important than previously recognised. After the major inflow in 2014, the Baltic Proper sumOD has reached its highest level so far. The gradual shift of the sumOD to shallower sub-halocline waters in the western and Northern basins has increased the risk of periodic coastal hypoxia and export of hypoxic water to the Bothnian Sea. The potential for inflows large e0ugh to more than eliminate the sumOD seems limited in the near term.

¹Baltic Sea Centre, Stockholm University, Stockholm, Sweden
²Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden

In the northern Baltic Sea region, climate change will lead to increased precipitation and freshwater inflows to the coastal zone. Coastal macrophytes may have an important role as filter, removing nutrients and pathogenic bacteria entering the system via land runoff and wastewater emissions. In Baltic Sea, one of the commonly found macrophyte species is Potamogeton perfoliatus. In this study, we investigated the nutrient reduction in the macrophyte meadow and the occurrence of potentially pathogenic bacteria associated with macrophytes in the Rundvik and Kylören bay, Västerbotten County region. Nutrient samples were collected in land-offshore transects: before, within and outside the macrophyte meadows. Bacteria were isolated using selected media. The results show that carbon-nitrogen-phosphorous nutrients were reduced in the macrophyte meadows, and that potentially pathogenic bacteria Vibrio sp, Pseudomonas sp, Serratia sp and Aeromonas sp were associated to the macrophytes. The bacterial analysis will be complemented by Nanopore 16S rRNA long-read sequencing of filtered seawater samples. The results imply that macrophytes constitute a natural cleansing mechanism, potentially protecting the recipient coastal system from wastewater emissions.

¹Department of Ecology and Environmental Science, Umeå University, SE-901 87 Sweden.
²Umeå Marine Sciences Centre, Umeå University, SE-905 71 Hörnefors, Sweden.

The elemental composition of phytoplankton (C:N:P ratio or stoichiometry) is critical for biogeochemical cycles in the sea. Environmental conditions can shape the stoichiometry of plankton biomass at large spatial scale (latitude), but our understanding of the variability of autotroph stoichiometry in relation to the dynamics of plankton microbial communities is incomplete. This gap contributes to the unpredictability of the impact of climate change on marine ecosystems. In this study, we explore the seasonal variability of the stoichiometry of planktonic microbial communities at an offshore station (LMO) in the Baltic Sea, Sweden. We combined C:N:P stoichiometry of the total microplankton community and different size fractions (<3 µm, 3-20 µm, 20-90 µm, 90-200 µm) spanning from picoplankton to filamentous cyanobacteria. Seasonal patterns across the size fractions highlight the predominance of both pico- and nanoplanktonic communities in the total photosynthetic plankton. Seasonal stoichiometry variability was higher in the largest phytoplankton fractions compared to the pico- and nanoplankton fractions that revealed stable carbon:nutrient ratios under various nutrient-limited conditions. The stoichiometric response and the comparison of the molecular diversity of the four planktonic fractions reveals their respective importance in the nutrient dynamics in the upper water column.

¹Department of Biology and Environmental Science, Linnaeus University, Kalmar, Sweden
²School of Business, Inovation and Sustainability, Halmstad University, Sweden

Climate change influences the ocean’s physical and biogeochemical conditions, causing additional pressures on marine environments and ecosystems, now and in the future. Such changes occur in environments that already today suffer under pressures from, for example, eutrophication, pollution, shipping, and more. We demonstrate how to implement climate change into regional marine spatial planning by introducing data of future temperature, salinity, and sea ice cover from regional ocean climate model projections to an existing cumulative impact model. This makes it possible to assess climate change impact in relation to pre-existing cumulative impact from current human activities. Results indicate that end-of-century projected climate change alone is a threat of the same magnitude as the combination of all current pressures to the marine environment. These findings give marine planners and policymakers forewarning on how future climate change may impact marine ecosystems, across space, emission scenarios, and in relation to other pressures.

¹Research Department, Swedish Meteorological and Hydrological Institute, Norrköping, Sweden
²Octopus Ink Research & Analysis, Lysekil, Sweden
³Geological Survey of Sweden, Uppsala, Sweden
⁴Kelonia AB, Göteborg, Sweden
⁵Department of Physical Oceanography and Instrumentation, Leibniz-Institute for Baltic Sea Research (IOW), Rostock, Germany
⁶Mountainlake, Göteborg, Sweden
⁷Department of Marine Sciences, Tjärnö Marine Laboratory, University of Gothenburg, Strömstad, Sweden
^ꝉDeceased

The crossing of environmental barriers poses major adaptive challenges. Rareness of freshwater-marine transitions separates their bacterial communities, but how these are related to brackish counterparts remains elusive, as are molecular adaptations facilitating cross-biome transitions. Here, we conduct large-scale phylogenomic analysis of freshwater, brackish, and marine quality-filtered metage0me-assembled ge0mes (11,276 MAGs). Average nucleotide identity analyses showed that bacterial species rarely existed in multiple biomes. Distinct brackish basins co-hosted numerous species despite differences in salinity and geographic distance, the latter having stronger intra-species population structuring effects. We further identified the most recent cross-biome transitions, which were rare, ancient, and most commonly directed towards the brackish biome. Transitions were accompanied by changes in isoelectric point distribution and ami0 acid composition of inferred proteomes, as well as convergent gains or losses of specific gene functions. Therefore, adaptive challenges entailing proteome reorganization and specific changes in gene content result in species-level separation between aquatic biomes.

¹Department of Gene Technology, KTH Royal Institute of Technology, Science for Life Laboratory, Stockholm, Sweden
²Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden

Long-chain polyunsaturated fatty acids (LC-PUFA; with ≥20 carbon atoms) are important biomolecules for a number of physiological and biological processes in organisms and are mainly produced de novo by algae. Algae-produced LC-PUFA are transferred to higher trophic levels and accumulated in the consumers in food chains. However, LC-PUFA content in consumers may vary with environmental conditions and their physiological demands. Therefore, the goal of our study was to investigate spatial and taxo0mic differences in LC-PUFA retention of fish predators in coastal ecosystems. We analysed the fatty acid (FA) composition of common fish species, i.e., roach and European perch, as well as their potential prey from benthic and pelagic habitats at three bays of the Northern Baltic Sea. We then assessed whether the fish LC-PUFA retention differed between species and among the study bays with different diet quality, i.e., LC-PUFA availability. Our data indicated taxon-specific differences in the retention of LC-PUFA and their precursor FA in fish. Perch did not show any spatial variation in retention of all these FA, while roach showed spatial differences in retention of docosahexaenoic acid (DHA) but not eicosapentae0ic acid (EPA). Data suggest that diet quality underlay the DHA retention differences in roach. Although the PUFA supply may differ among sites, the low spatial variation in LC-PUFA content of perch and roach indicates that both fishes were able to selectively retain LC-PUFA and/or convert precursor dietary FA to LC-PUFA. Since FA bioconversion is an energy-demanding process, it was not clear that bioconversion or selective retention alone would meet the LC-PUFA requirements of the fishes. This may be alarming as climate change together with other human-caused environmental changes in Northern coastal ecosystems will likely alter the algal assemblages and their LC-PUFA supply for consumers. We advocate further investigations on how environmental changes would affect the nutritional quality of the basal trophic level, and their subsequent impacts may affect the LC-PUFA and LC-PUFA retention in individual fish species.

¹Department of Ecology and Environmental Science, Umeå University, 90187 Umeå, Sweden
²Umeå Marine Sciences Centre, Umeå University, 90571 Hörnefors, Sweden
³Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, 75007 Uppsala, Sweden

The Pacific Oyster (Magallana gigas) is probably one of the most invasive species in the world. Originally from Japan, it has been spreading rapidly along the Swedish west coast since first recorded in 2007. Being identified as an invasive species comes directly with a negative connotation, but the complexity of its ecological effects is far from being well understood. M. gigas is an ecosystem engineer species and the biogenic reefs it creates act as refuge and substrate for many organisms. For instance, macroalgae species, which rely on a hard substrate to attach and in turn provide habitat to numerous species of invertebrates and fish. In this study, data on the biomass and species composition of the macroalgae occurring on oyster beds in the area around Tjärnö Marine Laboratory was collected to try to answer the question: do we find more macroalgae in places with a higher oyster coverage? Observations and data obtained from the field seem to support this hypothesis, but statistical analysis is yet to be performed. If this is the case, pacific oyster beds could be promoting biodiversity in the shallow coastal communities of the Swedish west coast.

¹Department of Marine Sciences, University of Gothenburg, Gothenburg, Sweden

It is assumed that the biological control of oceanic silica cycling is dominated by diatoms, with sponges and radiolarians playing additional roles. Recent studies have revealed that biosilicification also takes place in organisms which do not exhibit silicon dependent cellular structures, such as the picocyanobacterium Synechococcus. These findings imply that additional, yet unrecognized, marine microorganisms also take up silicic acid (dissolved silica, dSi). Here we show biogenic silica (bSi) accumulation in five strains of picoeukaryotes (<2–3 µm diameter), including three novel isolates from the Baltic Sea, and two marine species (Ostreococcus tauri and Micromonas commoda), in cultures grown with added dSi (100 µM). Average bSi accumulation in these novel biosilicifiers was quantitatively similar to that of Synechococcus isolates, ranging from 30-92 amol Si cell-1. Growth rate and cell size of the picoeukaryotes was not affected by dSi addition. This study is the first to document uptake of dSi by picoeukaryotes lacking silicon dependent structures. Yet, the purpose of bSi accumulation in these microorganisms remains unclear. The importance of this novel group of biosilicifiers should be considered in future studies.

¹Department of Biology and Environmental Science, Linnaeus University, Kalmar, Sweden
²Department of Geology, Lund University, Lund, Sweden

Langmuir Circulation (LC) is important for increasing mixing in the surface mixed layer. Too small mixing in the surface mixed layer may lead to (1) too shallow surface mixed layer, (2) too low SST during winter, and (3) too large SIE. In spite of this, LC is generally not included in the mixing parameterization in the 3D Baltic Sea circulation models being used to today, while at the same time, many of these models suffer from the above-mentioned weaknesses. This goal of this poster presentation is to visualize and quantify the improvements when including LC in a model for the Gulf of Bothnia based on NEMO-4.0.

¹Swedish Meteorological and Hydrological Institute

¹Department. of Chemistry, Umeå University, Umeå, Sweden.
²Kosterhavet National Park, Länsstyrelsen I Västra Götaland, Sydkoster, Sweden.

Macroalgae are growing in popularity, as human food, animal feed and supplements, for production of bioactive products and use in biorefineries.^1,2 The global market was $9.9 billion USD in 2021 and forecast $12.1 billion USD by 2030.³ Nearly all commercial macroalgae is farmed rather than wild harvested.² Concerns for food safety are usually for elements: arsenic, iodine, and heavy metals such as cadmium, lead, and mercury, while emerging issues are bacteria, marine toxins, persistent organic pollutants (POPs), pharmaceuticals, microplastics, and radionuclides.¹

Here we present the case for halogenated natural products (HNPs), which are produced by marine bacteria, phytoplankton, macroalgae and invertebrates.⁴ In particular, we focus on bioaccumulating and toxic “bromophenolic” HNPs which arise from transformation of precursor bromophenols. These include bromoanisoles (BAs), hydroxylated and methoxylated bromodiphenyl ethers (OH-BDEs and MeO-BDEs), and polybrominated dibenzo-p-dioxins (PBDDs). In this pilot study, we compare levels of BAs and MeO-BDEs in commercial and wild macroalgae. Commercial products were purchased from farms on the Swedish west coast (Skagerrak) and from other countries, wild macroalgae were harvested from Skagerrak and along the Norwegian coast.⁵ Extraction and analysis was conducted as described.⁵  In 12 commercial products comprising 9 species, the Σ₂BAs ranged from 0.01-5.8 ng/g wet weight (ww), while the Σ₂MeO-BDEs ranged from <10-138 pg/g ww. Ranges in 10 wild samples comprising 8 species were Σ₂BAs 0.4-58 ng/g wet weight (ww) and Σ₂MeO-BDEs ranged from <10-305 pg/g ww. The same species of commercial and wild macroalgae were analysed in four cases and levels of these HNPs were similar. Some bromophenolic HNPs bioaccumulate and have toxic effects^6-8. We suggest a broader survey of these compounds in commercial and wild macroalgae and food products derived from them, and development of Certified Reference Materials for analytical quality control.

1. Banach, J.L. et al., 2022. Foods 11, 1514. 
2. Ferdouse, F. et al., 2018. The global status of seaweed production, trade and utilization. FAO, Rome.
3. https://www.grandviewresearch.com/industry-analysis/commercial-seaweed-market#.       
4. Bidleman, T.F. et al., 2020. Environ. Sci. Technol. 54, 6468-6485.
5. Bidleman, T.F. et al., 2019. Environ. Sci. Proc. Impacts 21, 881-892,
6. Haglund, P. et al. 2007. Environ. Sci. Technol. 41, 3069-3074.
7. Legradi, J. et al. 2014. Environ. Sci. Technol. 48, 14703-14711.
8. Haraguchi, K. et al. 2016. Environ. Internat. 97, 155-162.

Phytoplankton are vital for energy transfer within the marine ecosystem, they depend on light for energy capture. The light environment in the Baltic is generally browner in the north than in the south. This shift in the visible light spectrum towards red wavelengths is caused by chromophoric dissolved organic matter (CDOM) which absorbs light in the blue part of the visible spectrum. Terrestrial CDOM levels in seawater are predicted to increase as climate change induces greater rainfall. The Baltic Sea system presents an opportunity to better determine the effect of this aspect of climate change on phytoplankton. Initially the effects of the light environment are investigated using culture techniques and DNA barcoding to determine how phytoplankton communities from northern and southern Baltic waters respond to changes in the visible light spectrum. We will show which species are favoured by the red shift in light and identify whether these species have adapted to cope with the challenges posted by this light environment.

¹Department of Ecology and Environmental Science, Umeå University, Umeå, Sweden