Intraspecific variability in the response of bloom-forming marine microalgae to changed climate conditions

Phytoplankton populations can display high levels of genetic diversity that, when reflected by phenotypic variability, may stabilize a species response to environmental changes. We studied the effects of increased temperature and CO₂ availability as predicted consequences of global change, on 16 genetically different isolates of the diatom Skeletonema marinoi from the Adriatic Sea and the Skagerrak (North Sea), and on eight strains of the PST (paralytic shellfish toxin)-producing dinoflagellate Alexandrium ostenfeldii from the Baltic Sea. Maximum growth rates were estimated in batch cultures of acclimated isolates grown for five to 10 generations in a factorial design at 20 and 24°C, and present day and next century applied atmospheric pCO₂, respectively. In both species, individual strains were affected in different ways by increased temperature and pCO₂. The strongest response variability, buffering overall effects, was detected among Adriatic S. marinoi strains. Skagerrak strains showed a more uniform response, particularly to increased temperature, with an overall positive effect on growth. Increased temperature also caused a general growth stimulation in A. ostenfeldii, despite notable variability in strain-specific response patterns. Our data revealed a significant relationship between strain-specific growth rates and the impact of pCO₂ on growth—slow growing cultures were generally positively affected, while fast growing cultures showed no or negative responses to increased pCO₂. Toxin composition of A. ostenfeldii was consistently altered by elevated temperature and increased CO₂ supply in the tested strains, resulting in overall promotion of saxitoxin production by both treatments. Our findings suggest that phenotypic variability within populations plays an important role in the adaptation of phytoplankton to changing environments, potentially attenuating short-term effects and forming the basis for selection. In particular, A. ostenfeldii blooms may expand and increase in toxicity under increased water temperature and atmospheric pCO₂ conditions, with potentially severe consequences for the coastal ecosystem.

EU side event at Rio+20: Hot, Sour and Breathless – Ocean Under Stress: consequences for sustainable development and resource provision for human communities

This side-event involves a partnership between EC and intergovernmental, international and national research projects, institutions, organisations and NGOs. Language will be English, although the short film will have subtitles in Brazilian Portuguese. It will address the major ocean stressors of ocean warming, acidification and deoxygenation, how this might impact sustainable development, resource provision for human communities and what science and society can do to assess vulnerable communities and to build resilience.

Oceans Day at Rio+20: advancing oceans, coasts, and island states at Rio+20 and beyond

The Ocean Global Forum, the IUCN and The Nature Conservancy will organize the Oceans Day at Rio+20. The event will take place in the Rio Conventions Pavilion on Saturday 16 June 2012, 0915-1830hrs (reception following).