Environmental and developmental physiology in the Arctic: The green sea urchin as a representative of planktonic developing marine larvae.

The ease of availability and the ecological and economic importance of S. droebachiensis make this species an excellent candidate for integrative studies of developmental physiology of marine organisms in Arctic ecosystems. We propose to conduct studies f undamental to establishing the green sea urchin as a valuable species for continued Norway/USA collaborative research on the unique physiological adaptations that permit survival of developmental stages in Arctic marine environments. Survival to the larv al feeding stage is dependent upon the metabolic demand of early development and the maternal supply of energy reserves invested in eggs. In the first study we will (i) determine the biochemical composition of eggs, embryos and larvae, (ii) the rate of en ergy metabolism during development, and (iii) how food availability regulates metabolism in Arctic and boreal populations of green sea urchin at their respective environmental temperatures. A second study will address the ability of green sea urchin de velopmental stages to respond to climate change. Polar environments are highly sensitive to global climate change. One likely outcome of climate change is a shift in phenology, i.e., the temporal and sequential occurrence of events in nature (in particula r the timing of life history events). The response to climate change may vary between organisms or trophic levels. One major ecological impact is the effective uncoupling between the timing of annual phytoplankton blooms and the appearance of feeding pl anktonic larvae. Such changes could impede the physiology and development of larvae to the point where perhaps no larvae would have the ability to recover even if food becomes available at a later time. This study will examine the ability of green sea u rchin larvae to survive and recover from periods of prolonged starvation, and is essential to understanding the possible impacts of changing phenology on recruitment dynamics.