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[1] Recently, the areal extent of melt ponds within sea ice has rapidly increased during the Arctic Ocean summer. However, the biological impacts of melt ponds on the Arctic marine ecosystem have rarely been studied. Carbon and nitrogen uptake rates of phytoplankton were measured at 26 different melt ponds in 2005 and 2008, using a 13 C-15 N dual stable isotope tracer technique. Generally, the open ponds had relatively higher nutrients than closed ponds, but the nutrient concentrations in the open ponds were within a range similar to those in surrounding surface seawaters. Chlorophyll a (Chl a) concentrations in melt ponds ranged from 0.1 to 2.9 mg Chl a m À3 with a mean of 0.6 mg Chl a m ) in the Arctic Ocean. Based on this study, recent annual carbon production of all melt ponds was roughly estimated to be approximately 2.6 Tg C, which is less than 1% of the total production in the Arctic Ocean.

The annual cycles of phytoplanktonic and microphytobenthic biomasses as food sources for intertidal bivalves were investigated in a temperate estuarine muddy sandflat of Kwangyang Bay (Korea) from January to December 2002. Seasonal patterns in growth and reproductive activity of a suspension-feeder Laternula marilina and a deposit-feeder Moerella rutila were examined in order to assess their relationship with the annual cycles of pelagic and benthic microalgae, and were combined with analyses of δ 13 C and δ 15 N of bivalve tissues and their potential food resources. Biomasses of phytoplankton and microphytobenthos peaked in late spring-summer, and demonstrated a unimodal pattern of seasonal variation. Photosynthetic pigment composition showed a predominance of diatom marker pigment, fucoxanthin, in the water and the sediments throughout the year. Similar patterns of annual cycles in pelagic and benthic microalgal biomasses and similarities in taxonomic composition indicated that resuspended microphytobenthos is an important contributor to the bay's phytoplankton component. This was supported by the δ 13 C values of suspended particulate organic matter (POM) and physical characteristics of the bay. Synchrony in growth and reproductive activity was observed for both bivalves: their shell and tissue growth and gonadal development were achieved together during late spring and summer when chlorophyll a (chl a) concentrations were highest. This temporal coupling of macrofaunal and microalgal processes indicated that the activities of intertidal bivalves might depend largely on microphytobenthos seasonality. The isotopic signatures of the bivalve tissues demonstrated their dependence on organic matter of microphytobenthic source irrespective of season, despite a comparable contribution of phytoplankton to the diet of the suspension-feeding bivalve. These results highlight the importance of seasonal development of microphytobenthos as an available food source during the critical period of gamete production and growth for both suspension-and deposit-feeding bivalves.

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Although the Ulleung Basin is an important biological ''hot spot'' in East/Japan Sea (hereafter the East Sea), very limited knowledge for seasonal and annual variations in the primary productivity exists. In this study, a recent decadal trend of primary production in the Ulleung Basin was analyzed based on MODIS-derived monthly primary production for a better annual production budget. Based on the MODISderived primary production, the mean daily primary productivity was 766. the Ulleung Basin during the study period. The monthly contributions of primary production were not largely variable among different months, and a relatively small interannual production variability was also observed in the Ulleung Basin, which indicates that the Ulleung Basin is a sustaining biologically productive region called as ''hot spot'' in the East Sea. However, a significant recent decline in the annual primary production was observed in the Ulleung Basin after 2006. Although no strong possibilities were found in this study, the current warming sea surface temperature and a negative phase PDO index were suggested for the recent declining primary production. For a better understanding of subsequent effects on marine ecosystems, more intensive interdisciplinary field studies will be required in the Ulleung Basin.

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