Abstract: Changes in the fatty acid composition in the tissues of the bivalve Quidnipagus palatum from the Tomigusuku intertidal flat, Okinawa, Japan, collected in four different seasons (November 2000, the beginning of cold season; January 2001, the cold season; May 2001, the rainy season; and July 2001, the warm season) were examined and compared to the composition of surface sediments and suspended particulate materials. Assessment of fatty acid markers suggested that the food sources of Q. palatum differed between seasons and depended on the sources of organic material present in the sediment and water column. Vascular plants and bacteria were the main dietary components from July to November because of their abundance in the sediment. From November to January, macroalgae and phytoplankton were the major food sources of Q. palatum, corresponding to their predominance in sediments and algal blooms, respectively. During the May rainy season, organic matter in the sediment was dominated by diatoms, whereas the water column contained diatoms and resuspended macroalgal detritus. The transition to the warm season by July significantly increased the contribution of diatoms to the organic matter present in both the sediment and the water column. Consequently, from May to July, diatoms became the main food source for Q. palatum.

Abstract: Katabatic flows largely dominate the climate of the Adelie Land coastal region. A detailed climatological data analysis of Dumont d'Urville has been conducted. Results of this study support the idea that katabatic flow can be locally enhanced by the diurnal cycle of solar insolation and the temperature contrast between the continent and the ocean. The interaction between katabatic wind and local thermal effects is expressed in terms of scale analysis. Except for surface stress, all terms in the momentum equation for a katabatic flow in a coastal region of Antarctica can reach the same order of magnitude. The local circulation then is the result of a relatively tenuous force balance which can be disrupted even by a weak perturbation of any term. To estimate the effect of the temperature contrast between the ocean and the continent on the katabatic flow, two numerical experiments have been conducted. The simulations consider an ocean free of sea ice representative of the summer months, and another winter case with the ocean covered by thick sea ice. These simulations show that with the ocean free of sea ice, the katabatic flows extend only a limited distance over the open ocean during the day due to the local thermal effects. With the ocean covered by sea ice, the katabatic winds are not constrained and extend a considerable distance offshore.