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| Vertical Flux of Ice algae in a Shallow Lagoon, Hokkaido, Japan pp. 435-456 |
$100.00 |
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Authors: (Yoko Niimura, Hiroaki Saito, and Satoru Taguchi, Tokyo University of Fisheries, Tokyo 108-0577, Japan, and others)
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Abstract:
A seasonal variability in the vertical flux of ice algae was examined with a multiple sediment trap during seasonal ice coverage in SaromaKo Lagoon, Hokkaido, Japan. The multiple sediment traps were moored at 4 m below the water surface and 5 m above the bottom to collect suspended materials at 7 dayintervals for 64 days from February 4 to April 8, 1999. Community structure of ice algae and water column phytoplankton collected with the sediment traps was determined in terms of both cell abundance and cell volume. For the ice algal community, Odontella aurita was the most dominant in cell volume, followed by Pleurosigma spp., Achnanthes spp., Detonula confervacea, Bacteriaosira fagilis, Fragilariopsis spp., and Navicula spp. while Fragilariopsis spp. and Achnanthes spp. were dominant numerically. Water column phytoplankton were dominant in descending order of cell volume by Membraneis spp. Thalassiosira spp. Campylodiscus sp., Chaetoceros spp., Amphora spp., and Dictyocha speculum, and Alexandrium sp. Mean cell volume ratio of ice algae to total algae with one standard deviation was 0.30 ± 0.28 and highly variable although a similar ratio based on cell number was 0.72 ± 0.06. The vertical fluxes of chlorophyll a (Chl a) was estimated from the volume ratio, and the mean with one standard deviation was 0.90 ± 0.42 mg Chl a m−2 d−1. This suggests that the ecological role of ice algae in a small embayment should be considered separately from ecosystem in the high latitudes although a total release of ice algal carbon from the sea ice into a water column could be similar to one in the high latitudes and only 3 g C m2 in 65 day ice season. Even during the ice coverage, due to a lateral transport of phytoplankton through two channels from the Sea of Okhotsk, where ice coverage was always incomplete, the community structure of released ice algae under the sea ice was modified significantly. A combination of laterally transported water column phytoplankton and vertically released ice algae into the underlying water column may play a significant role in the energy transfer to the successful aquaculture of scallops and oysters as well as other benthos in the shallow coastal water ecosystem. |
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