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Marine pelagic projects

Assessing the effects on the marine pelagic food web by the invasive marine cladoceran Penilia avirostris

An effect of climate change is that marine organisms previously living in warmer waters are expanding their distribution. The cladoceran Penilia avirostris, normally distributed in warmer marine areas, has invaded the Swedish west coast, and become the dominant larger zooplankton during autumn. Penilia is probably competing with native copepod species for food. Penilia also consumes plankton of a smaller size than copepods, possibly leading to a shorter food chain; a higher amount of carbon and energy will go directly to zooplankton eating fish. The food quality of Penilia for plankton eating fish and fish larvae is unknown, as well as the ability of the fish to catch Penilia. This project is investigating the effects of Penilia on the pelagic food web, with emphasis on:

  1. How Penilia affects the microbial food web
  2. How Penilia affects plankton consuming fish e. g. sprat and herring

Methods that are used are laboratory studies, field sampling and experiments, and analysis of historical data.

The invasive cladoceran Penilia avirostris. Photo by Per Carlsson
The invasive cladoceran Penilia avirostris. Photo by Per Carlsson

Sinking rates and phenotypic plasticity among marine phytoplankton in a warmer world

This project is studying the effects of increasing sea surface temperatures, due to global warming, on sinking rates of marine phytoplankton, and if phenotypic plasticity among the plankton can counteract increased sedimentation rates. Physics tells us that particles sink faster in seawater at higher temperature, meaning that sinking rates of non-motile plankton such as diatoms, will be higher as the temperature of the sea is rising. However, it is not known if the cells can change their size or density and to some degree decrease their sinking rate at a higher temperature. Recent research suggests that cells decrease in volume at higher temperature but this has not been linked to sinking rates. The project addresses:

  1. How do sinking rates for different diatom species vary with temperature?
  2. How is the sinking rate dependent on the physiological state of the cells, and can changes in size or density counteract a higher sinking rate?
  3. Can phytoplankton adapt to long-term to changes in seawater temperature, by decreasing their sinking rate?

The project consists of laboratory experiments to answer these questions. The results will give insights into the effects on plankton sinking when surface water temperature is rising: will there be an increased carbon export to the deep sea, and lower carbon dioxide uptake from the atmosphere, or can the phytoplankton change in size or density and decrease their sinking rates?

Thalassiosira eccentrica
The centric diatom Thalassiosira eccentrica

Temporal and spatial distribution of harbour porpoises in the southern Kattegat

This project is aiming at quantifying the temporal and spatial distribution of harbour porpoises in the southern Kattegat, an area considered to be a ”hot spot” for harbour porpoises. The project will use an acoustic method to quantify the presence of porpoises, and also aerial surveillance with a drone in order to study movements of individuals and mothers and calves. Echolocation of potential fish prey in combination with gill net fishing will also be used to study the porpoise distribution in relation to their food source. The project will seek answers to the following questions:

  1. What is the spatial and temporal distribution of harbour porpoises in southern Kattegat?
  2. Is this distribution correlated with e g the day/night cycle, the lunar cycle, fish distribution?
  3. Can some areas in the southern Kattegat be identified as important reproduction areas for the harbour porpoise?

Harbour porpoise outside Kullaberg. Photo: Johanna Stedt
Harbour porpoise outside Kullaberg. Photo: Johanna Stedt
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Ceratium furca