Marine phytoplankton community data and corresponding environmental properties from eastern Norway, 1896-2020.

Time series are essential for studying the long-term effects of human impact and climatic changes on the natural environment. Although data exist, no long-term phytoplankton dataset for the Norwegian coastal area has been compiled and made publicly available in a standardised format. Here we report on a compilation of phytoplankton data from inner Oslofjorden going back more than a century. The database contains 605 sampling events from 1896 to 2020, and environmental data has also been provided when available. Although the sampling frequency has varied over time, the high taxonomic quality and relatively similar methodology make it very useful. For the last 15 years (2006-2020), the sampling frequency has been almost monthly throughout the year. This dataset can be used for time series analysis to understand community structure and changes over time. It can also be used to study common taxa' responses to environmental variables and changes, seasonal or annual species diversity and be useful for developing ecological indicators.

The MicroClimate Screen - A microscale climate exposure system for assessing the effect of CO2, temperature and UV on marine microalgae.

Global warming and anthropogenic activities are changing the ocean, inducing profound impacts on marine life and ecosystems from changing physical and chemical factors in and above the water column. Rising surface temperatures, ocean acidification, and seasonal variations in UV radiation (UVR), modulated by water clarity and sea-ice extent, affect life cycles of the marine food-web, and directly or indirectly also the global carbon fixation. Diatoms, pelagic microalgae that are responsible for 40% of the marine productivity, have limited capability to avoid exposure to changing ocean conditions, and hence, highly relevant for model studies of the influence of climate change on growth and productivity in the marine environment. A plate-based high-throughput exposure system was constructed to assess the biological effects from relevant climate change factors on the diatom Skeletonema pseudocostatum, conducted as a chronic toxicity tests over 72 h periods. The exposure system consisted of a micro-climate unit and a light-exposure unit, enabling accurate regulation of pCO2, temperature, UVR and photosynthetic active radiation (PAR). Changes in physical factors, including pH, dissolved inorganic carbon (DIC), total alkalinity (TA), temperature and salinity in the medium, as well as reduction in growth were characterised to demonstrate performance of the micro exposure system. The results demonstrate that the exposure system successfully simulated ocean acidification and could maintain stable temperature (CV < 3%), PAR and UVR irradiance (CV < 8%). Growth inhibition responses were typically dose-dependent and verified that the micro-exposure system could be used to assess effects and adaptions to climate-relevant stressors.

The advective origin of an under-ice spring bloom in the Arctic Ocean using multiple observational platforms.

Under-ice blooms of phytoplankton in the Chukchi Sea have been observed, with strong implications for our understanding of the production regimes in the Arctic Ocean. Using a combination of satellite remote sensing of phytoplankton biomass, in situ observations under sea ice from an autonomous underwater vehicle (AUV), and in vivo photophysiology, we examined the composition, magnitude and origin of a bloom detected beneath the sea ice Northwest of Svalbard (Southern Yermak Plateau) in May 2010. In situ concentration of up to 20 mg chlorophyll a [Chl a] m-3, were dominated by the northern planktonic spring species of diatoms, Thalassiosira nordenskioeldii, T. antarctica var. borealis, Chaetoceros socialis species complex and Fragilariopsis oceanica. These species were also found south of the marginal ice zone (MIZ). Cells in the water column under the sea ice were typically high-light acclimated, with a mean light saturation index (E k ) of 138 µmol photons m-2 s-1 and a ratio between photoprotective carotenoids (PPC) and Chl a (w:w) of 0.2. Remotely sensed data of [Chl a] showed a 32,000 km2 bloom developing south of the MIZ. In effect, our data suggest that the observed under-ice bloom was in fact a bloom developed in open waters south of the ice edge, and that a combination of northward-flowing water masses and southward drifting sea ice effectively positioned the bloom under the sea ice. This have implications for our general understanding of under-ice blooms, suggesting that their origin and connection with open water may be different in different regions of the Arctic.