Phytoplankton, Protists

Autecology of Key Species and Food-web Relationships within the Plankton

Investigations on population dynamics of key species and on the major properties which make these species so successful within their ecosystems. Interactions with the biotic and abiotic environment in space (local and global) and time. Influence of key species on geochemical processes such as sea water chemistry dynamics and sedimentation of organic and inorganic materials. Selection, geological and evolutionary processes crucial for the origin of key species.
 
Comparatively few genera and species of plankton are responsible for the bulk of primary and derived production in the ocean. The factors selecting dominance of phytoplankton key species are largely unknown and, in view of the wide range of environmental conditions under which blooms of the same species are commonly encountered, cannot be attributed to physico-chemical conditions, i.e. bottom-up factors, alone. The accumulation rate of cells of a population represents the balance between growth and mortality rates. There is growing evidence that factors regulating mortality rates are responsible for the ultimate size that species populations attain.

As natural mortality cannot be replicated under laboratory conditions, detailed studies of ecological processes in the field supplemented by long-term observations and in situ fertilization experiments will be necessary to identify the suite of factors that lead to dominance of one or several species populations over the others.

Powerful new methods and instruments enable processes to be addressed at the species level under field conditions. So the species approach to plankton ecology and ocean biogeochemistry is now tractable. Clearly, a better understanding of the ecology and life cycles of such key species will provide the information necessary to understand the mechanisms forming Polar ecosystems. In addition, crucial traits which aid these species in surviving, such as physiological adaptations, physical and chemical defenses, and onthogenetic strategies, are studied in detail in andvanced laboratory investigations.