Beschreibung: Highlights: • Larvae upregulate genes associated with fatty acid and glycogen synthesis under moderate ocean acidification (OA) • Larvae under high levels of OA fail to regulate • Dysfunctional metabolism and stress associated with pathologies in internal organs • Lack of differential gene regulation and stress response in juveniles correspond to a higher resilience to OA stress Elevated environmental carbon dioxide (pCO2) levels have been found to cause organ damage in the early life stages of different commercial fish species, including Atlantic cod (Gadus morhua). To illuminate the underlying mechanisms causing pathologies in the intestines, the kidney, the pancreas and the liver in response to elevated pCO2, we examined related gene expression patterns in Atlantic cod reared for two months under three different pCO2 regimes: 380 μatm (control), 1800 μatm (medium) and 4200 μatm (high). We extracted RNA from whole fish sampled during the larval (32 dph) and early juvenile stage (46 dph) for relative expression analysis of 18 different genes related to essential metabolic pathways. At 32 dph, larvae subjected to the medium treatment displayed an up-regulation of genes mainly associated with fatty acid and glycogen synthesis (GYS2, 6PGL, ACoA, CPTA1, FAS and PPAR1b). Larvae exposed to the high pCO2 treatment upregulated fewer but similar genes (6PGL, ACoA and PPAR1b,). These data suggest stress-induced alterations in the lipid and fatty acid metabolism and a disrupted lipid homeostasis in larvae, providing a mechanistic link to the findings of lipid droplet overload in the liver and organ pathologies. At 46 dph, no significant differences in gene expression were detected, confirming a higher resilience of juveniles in comparison to larvae when exposed to elevated pCO2 up to 4200 μatm.

Beschreibung: Cape anchovy Engraulis encrasicolus is an ecologically and economically important pelagic fish species occurring along the coast of South Africa. A recent eastward shift in Cape anchovy distribution indicates that environmental conditions are becoming more favorable for the species on the east coast. This shift is particularly important in the sheltered Algoa Bay region, a nursery area for fish larvae. However, the relatively low productivity of the Agulhas Current Large Marine Ecosystem on the eastern coast of South Africa may result in an anchovy population in poorer nutritional condition and with slower growth rates than the west coast population. Using otolith and nucleic acid analyses, the growth rates of anchovy larvae from the western and southeastern coasts of South Africa were compared. The otolith analysis results indicated that, at any given age, individual growth rates for anchovy larvae were higher on the southeast coast than on the west coast. The RNA:DNA values also indicated that instantaneous growth rates of anchovy larvae were higher in Algoa Bay than on the west coast. At the time of sampling, chlorophyll and zooplankton productivity were higher at sampling sites in Algoa Bay than sites on the west coast, potentially due to favorable oceanographic features in the bay. As such, the results suggest that Algoa Bay is a suitable and potentially favorable nursery area for the early stages of anchovy, highlighting the importance of separate management of the southeast coast region in a changing world.

Beschreibung: Highlights: • Microplastic abundance was overall low and not related to environmental parameters. • High microplastic loads were found on few occasions after rainfall and snowmelt. • Microplastics were mainly hard fragments of PE and PP in various colours. • Microplastic contamination from the wastewater treatment plant was the lowest. • Stormwater drains are important source of microplastics into the marine environment. Abstract: Microplastics are ubiquitous to most marine environments worldwide, and their management has become one of the major challenges facing stakeholders. Here we monitored monthly, between March 2018 and March 2019, the abundance of microplastics (0.3–18.2 mm) at the sea surface within the Kiel Fjord, southwest Baltic Sea. Microplastics were sampled at eight locations, inside and outside the fjord, near potential source of microplastics, such as the outlets of storm drains or the Kiel-Bülk wastewater treatment plant, the Schwentine River mouth and the entrance of the Kiel Canal. Weather (wind, precipitations) and seawater (salinity, temperature) parameters were compared to the spatiotemporal distribution of the microplastics. We found an overall stable, and low (0.04 particles/m3), microplastic load within the Kiel Fjord compared to other urban areas worldwide with comparable population densities. No relationship was found between the microplastic abundance and the environmental factors, but the few samples that yielded unusually high amount of microplastics were all preceded by rainfall and snow/ice melt. During such events, vast amounts of water, potentially contaminated with microplastics, were released into the fjord via the storm drainage system. The microplastic abundances at the wastewater plant outflow were among the lowest of our survey, likely thanks to an efficient filtering system. The results of this study highlight the importance to repeat microplastic samplings over time and space to determine with confidence baseline microplastic abundance and to detect unusual acute contamination, especially during snow and ice melting. Overall, the microplastic abundance within the Kiel Fjord was low, probably thanks to efficient waste management on land. However, improvements are still needed to filter millimetre-sized particles within the storm drainage system, which is likely a major source of microplastics into the marine environment.

Beschreibung: Ovigerous females were collected by scraping from inner Kiel Fjord in July -August 2017 and kept under control constant temperature room (~20°C) until egg hatching. Newly hatched larvae were reared under different salinity treatments in order to estimate their salinity tolerance,. Experiments were conducted until larvae reached the megalopae stage (last larval stage) or died, The results of such study could give us a primary outlook on the dispersal ability of H. takanoi larvae along the Baltic Sea, and insights about the life cycle of H. takanoi specifically in the south-western Baltic.

Beschreibung: Crabs were collected from inner Kiel Fjord by scraping in November 2018, in order to study their tolerance to salinity and consequently their ability to establish a population along the Baltic Sea, in addition, their feeding rates were estimated under laboratory condition. Experiments were conducted in constant climate temperature room (~12 °C) at GEOMAR during December 2018.

Beschreibung: Salinity in Kiel Fjord was recorded on mostly-weekly cruises of the research vessel FK Polarfuchs from 2005 to 2018 using a CTD48M probe (Sea and Sun technologies, Trappenkamp, Germany) at a station in front of the GEOMAR Pier (“Wittlingskuhle”, Position: 54°19'69 N, 10°09'06 E). These measurements are important for better understanding the salinity as one of the important abiotic factor determine the reproduction, establishment and has an effect on many species in the Baltic Sea in general and the fjord specifically.