Bentic and pelagic micro algae

THE ECOLOGY OF BALTIC CYANOBACTERIA FOCUSING ON BOTTOM-UP FACTORS

Current environmental issues in the Baltic environment are the increasing occurrence of toxic algal blooms, eutrophication and the increasing level of UV-B radiation (UV-B: 280-(315) 320 nm). Light and nutrients are key factors for photosynthetic primary producers but light can act as a promoting as well as a restricting factor to both the individual cell and the phytoplankton community. The ultraviolet part of the solar spectrum is believed to act as a restricting factor. The overall aims of the project are to assess the influence of bottom-up factors and study the effects of I) high light intensities (PAR: 400-700 nm) and UVR (280-400 nm)) on the biodiversity of phytoplankton communities focusing on bloom-forming Baltic cyanobacteria, and II) the interaction effects of UVR and nutrients (N, P). A central question to be answered is "Will UV-B radiation function as a selective pressure thereby altering the microalgal biodiversity?" The project aims at increasing the knowledge about factors controlling the occurrence and distribution of toxic microalgae, a knowledge crucial for predicting toxic phytoplankton blooms.

In addition, we are studying the ecological role of UV-absorbing compounds and the cyanotoxin nodularin.

LIGHT EFFECTS ON POLAR PRIMARY PRODUCERS

I have a special interest in polar research (Arctic and Antarctic environments) focusing on effects of UVR on both microalgal and macroalgal communities. Marine macroalgae are very important primary producers in coastal ecosystems, serving as food for herbivores and as habitat for many organisms. Both, UVR and consumers significantly shape macroalgal succession in the Antarctic intertidal. Consumers, particularly gastropods can mediate negative effects of ambient UVR on richness and diversity till a certain level. UV-B radiation in general and an increase of this short wavelength due to stratospheric ozone depletion in particular may have the potential to affect the zonation, composition and diversity of Antarctic intertidal seaweeds altering trophic interactions in this system. Furthermore, in the study area (Potter Cove, King George Island) the phytoplankton biomass is not sufficient to explain the benthic consumer abundance and the benthic microalgae dominated by benthic diatoms account for the nutrition of the local fauna. Here benthic diatoms seem unaffected by UVR but the mechanisms behind this tolerance are still to be elucidated.

During autumn-winter 2003 and 2004 I worked on King George Island, Antarctica. During the International Polar Year I participated in the Norwegian IPY project CLEOPATRA (Climate effects on planktonic food quality and trophic transfer in Arctic Marginal Ice Zones). We were studying:

• The timing, quantity and quality of ice algal and phytoplankton spring bloom
• How variations in light and UV radiation affect algal food quality
• The importance of timing and available food for reproduction and growth of the dominant herbivorous zooplankton species Arctic shelf seas

The major part of this project was presented at OSC, IPY Oslo Science Conference, June 2010.

GreMeCa – GREENHOUSE GASES AND MERCURY IN A CHANGING ARCTIC

This is an interdisciplinary project funded by The Swedish Research council. In short: The changing climate in polar regions is predicted to be faster than for the rest of our planet due to the influence of feedbacks related to the changing surface of Polar Oceans. The exchange between ocean –atmosphere - snow – sea ice of greenhouse gases (carbon dioxide, carbon monoxide, methane, naturally produced ozone depleting substances, oxides of nitrogen) is driven by physical, chemical and biological processes occurring in the snowpack and sea ice, and this exchange has a significant impact on the concentrations of ozone and mercury. During spring at polar sunrise, both these chemical species are depleted in the troposphere, and this process is mediated by air-surface exchange of gases, specifically halogen species. The objective is to determine the importance of greenhouse gases, as well as mercury, for chemical and biological exchange processes in the marine environment with focus on Polar regions and their feedback mechanisms in the context of a changing climate. The project aims to investigate the mechanisms controlling the temporal and spatial variability in the processes driving the fluxes of greenhouse gases and mercury in the sensitive polar ocean. The exchange of species between sea – atmosphere- sea ice – snow, as well as the control mechanisms, will be studied in laboratory experiments as well as in field studies, with emphasis on the impact of changes in sea ice cover, precipitation, temperature, changes in UV radiation, and a high carbon dioxide scenario.

In March – April, 2010, we spent ca 3 weeks in Ny-Ålesund, Svalbard, studying the fluxes of e.g. greenhouse gases between the atmosphere, sea ice and sea water, and the impact of microalgae and bacteria on these processes.