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A mesocosm study with oil in ice was performed in Van Mijenfjorden in Svalbard to compare effects of the oil spill responses (OSR) in situ burning, chemical dispersion and natural attenuation on the physiological performance of the Arctic copepod Calanus glacialis . Seawater collected from the mesocosms in winter and spring was used in laboratory incubation experiments, where effects on fecal pellet production, egg production and hatching success were investigated over a period of 14 days. Polycyclic aromatic hydrocarbon (PAH) seawater concentrations were lowest in winter. Brine channel formation in spring resulted in an 18 times increase in PAH concentration in the chemical dispersion treatment (1.67 μg L −1 ), and a 3 fold increase in the natural attenuation (0.36 μg L −1 ) and in situ burning (0.04 μg L −1 ) treatments. The physiological performance of female C. glacialis was unaffected by the PAH seawater concentrations. However, a higher mortality and deformity of nauplii was observed in the chemical dispersion treatment, highlighting the importance of considering secondary effects on next generation in future environmental risk assessment of OSR. This study shows that during the ice-covered period, chemical dispersion of oil spills leads to higher PAH exposure than natural attenuation and in situ burning, with potential consequences for recruitment of Arctic copepods. [ABSTRACT FROM AUTHOR]

Salp fecal pellets are rich in organic matter and have been shown to sink at very high velocities. In recent years, salp abundances have been increasing in the Southern Ocean where they seem to be replacing krill as the dominant grazers on phytoplankton. As salps can form large swarms with high pellet production rates, it has been suggested that they will become increasingly important for the vertical export of particulate organic matter in the Southern Ocean. However, detailed studies combining both investigations of pellet production rates, turnover, and export are still needed in order to determine whether salp pellets are important for export (‘sinkers’) or recycling (‘floaters’) of organic matter. Our results suggest that pellets are produced at high rates in the upper few hundred meters of the water column. Although we observed high sinking velocities and low microbial degradation rates of the produced salp pellets, only about one third of the produced pellets were captured in sediment traps placed at 100 m and about ~13% of the produced pellets were exported to sediment traps placed at 300 m. The high retention of these fast-settling pellets seems to be caused by break-up and loosening of the pellets, possibly by zooplankton and salps themselves. We measured 3-fold lower size-specific sinking velocities in loosened and fragmented compared to freshly produced intact pellets-. This enhanced the residence times (>1 day) of both small and large pellets in the upper water column. We postulate that the fragile nature of salp pellets make them more important for recycling of organic matter in the upper mesopelagic layer rather than as a conduit for export of particulate organic matter to the seafloor. [ABSTRACT FROM AUTHOR]

In order to explore possible development process of red tides caused by Prorocentrum donghaiense, effects of concentrations of P. donghaiense and Oxyrrhis marina on the feeding behaviour of Oithona brevicornis were investigated. The results showed that within the concentration range of P. donghaiense, 1.0~5.0×104 cells·mL-1, ingestion rates (IRs) and faecal pellet production rates (FPPRs) of O. brevicornis on P. donghaiense increased with increasing concentrations of P. donghaiense, the maximum IR and FPPR were 620 cells·ind-1·h-1 and 31.67 pellet·copepod-1·d-1, respectively. When the concentration of P. donghaiense was 10.0×104 cells·mL-1, the IR value decreased to 400 cells·ind-1·h-1 and the FPPR value decreased to 13.33 pellet·copepod-1·d-1, respectively. Within the concentration range of P. donghaiense, 1.0~10.0×104 cells·mL-1, filtration rates (FRs) of O. brevicornis decreased with increasing concentrations of P. donghaiense. The results also showed that O. brevicornis could ingest O. marina fed P. donghaiense, and within the concentration range of O. marina, IRs of O. brevicornis on O. marina increased with increasing concentrations of O. marina, while its FRs decreased, the maximum IR value and FR value were 300 cells·ind-1·h-1 and 0.23 ml·ind·h-1, respectively. Within the concentration range of O. marina, FPPRs of O. brevicornis increased with increasing concentrations of O. marina, the maximum FPPR was 21.67 pellet·copepod-1·d-1, and FPPRs had a good linear relationship with IRs. In this study, "Copepodsred tide algae" and "Copepods-protozoa-red tide algae" food chain models can provide references for the development process and regulating method of red tides caused by P. donghaiense. [ABSTRACT FROM AUTHOR]

Abstract: The influence of six monoalgal diets was tested on the reproductive success of the copepod Acartia tonsa over a 15-day period in order to define the most favorable diet for the optimization of this copepod species to be used in aquaculture and in ecotoxicology applications. The cryptophytes Rhinomonas reticulata and Rhodomonas baltica induced highest egg production rates (mean=24.4eggsfemale−1 day−1and 21.9eggsfemale−1 day−1) and hatching success (mean=76% and 86.1%) over the 15-day period, respectively. Lowest egg production rates were recorded with both diatoms Phaeodactylum tricornutum (mean=8.8eggsfemale−1 day−1) and Skeletonema marinoi (mean=8.4eggsfemale−1 day−1). These two diatoms also had detrimental effects on hatching success (mean=44.1% and 46.5%, respectively) and adult survival. No adults survived for longer than 13days with a diet of P. tricornutum. Moreover, nauplii produced by females that had fed on diatoms for >10 d, were positively stained for the apoptotic fluorescent marker TUNEL, indicating imminent death. The prasinophyta Tetraselmis suecica induced low fecundity (mean=13.4eggsfemale−1 day−1) and hatching success (mean=62%), and after 15days only 37.5% of the adults survived. Isochrysis galbana induced low egg production per female (<10eggsfemale−1 day−1) after 15days. [Copyright &y& Elsevier]

The article focuses on the development an history of three Calanus species in Disko Bay, Greenland, which includes C. finmarchicus, C. glacialis and C. hyperboreus. The authors conducted their study to understand coupling of the phytoplankton in Disko Bay from later winter to mid-summer 2008. The study disclosed that on the onset of the phytoplankton bloom, C.finmarchicus and C. glacialis were the first to surface in the water and was followed after two weeks by C. hyperboreus. It was also found that there was refueling of storage lipids by C. glacialis and C. hyperboreus during the bloom and after it.

We studied the physiological response of Pseudocalanus sp. under four different temperature elevation regimes: +0, +2, +4 and +6 °C above the decadal average temperature in the Western Baltic Sea. We measured fecal pellet (FP) production rates, which was taken as a proxy of ingestion, egg production (EPR) and respiration rates. Experiments lasted from mid-February to end April, corresponding most of the observations to the postspring bloom phase. We combined small scale incubations with the use of big (ca. 1400 L) mesocosms, which have previously been shown to be appropriate when studying phyto- and zooplankton succession, and the water used for the incubations was taken from the mesocosm tanks. Given that the phytoplankton succession varied between the four thermal scenarios, we evaluated (excepting in the case of the respiration rates, where incubations were carried out using 0.2 μm filtered water) both the temperature and the associated food concentration effects. Respiration and ingestion rates were found to increase with temperature. As for EPR, they also increased with temperature during the bloom, but remained at low and constant values during the postbloom in all the four treatments due to the food limitation. Linked to the temperature rise, we also detected an increase in instantaneous mortality rates and a reduction in the net growth efficiency. Finally, we discuss the potential implications of our findings for the spring phyto- and zooplankton succession under the forecasted climate warming, as well as for the fisheries in the Baltic Sea, where Pseudocalanus sp. is a key species. [ABSTRACT FROM AUTHOR]

• MPs (20 μm) did not affect fecal pellet production rate on Arctic Calanus species. • MPs caused stress-induced spawning in arctic Calanus copepods. • The amount of MPs ingested by copepods depends on food concentration. • The presence of MPs in C. hyperboreus pellets did not affect their sinking rates. • MPs have a low impact on arctic Calanus at current environmental concentrations. Microplastics (MPs) are contaminants of emerging concern in the Arctic, but knowledge of their potential effects on Arctic plankton food webs remains scarce. We experimentally investigated ingestion and effects of MPs (20 μm polyethylene spheres) on the arctic copepods Calanus finmarchicus, C. glacialis and C. hyperboreus. These species dominate arctic zooplankton biomass and are relevant target species to investigate the potential impacts of MPs on the Arctic marine ecosystem. Females of each species were exposed to two concentrations of MPs (200 and 20,000 MPs L−1) in combination with different food (diatom) concentrations, reflecting high (3000–5000 cells mL−1, spring phytoplankton bloom) and low (50–500 cells mL−1, pre/post bloom) food conditions. MPs did not affect negatively fecal pellet production rates in any of the species at the studied exposure concentrations. However, egg production rates of copepods exposed to MPs were 8 times higher compared with the controls, which suggests that MP exposure can cause stress-induced spawning in arctic copepods. Microscopic examination of the fecal pellets confirmed ingested MPs in the three species (up to aprox. 1000 MPs cop−1 d−1). The number of MPs per pellet decreased exponentially with increasing food concentration. The daily ingestion of MPs per copepod was higher at low- food concentrations (250–500 cells mL−1). At our exposure conditions, the presence of MPs inside C. hyperboreus fecal pellets did not affect their sinking rates. Overall, our experimental research show that 1) acute exposure to virgin polyethylene MPs has a low impact on arctic Calanus species at environmentally relevant MP concentrations, independent of food availability, and 2) arctic copepods influence the environmental fate of plankton-sized MPs by exporting buoyant MPs from the surface layer to the sea floor via fecal pellets. [ABSTRACT FROM AUTHOR]