Photosynthetic characteristics of phytoplankton off Adelie Land, Antarctica, during the austral summer

The photosynthesis-irradiance characteristics (P-E curves) and quantum yields of natural phytoplankton were investigated in the Southern Ocean off Adelie Land, Antarctica, during the austral summer. Data were acquired at eight stations during a cruise of T/V Umitaka-Maru III. The photosynthetic P-E curves showed low light adaptation of phytoplankton. Mean value (±standard deviation) of the P-E curve parameters, α^*, and I_k, were 0.014 (±0.013) mgC (mg chl. α)^ h^1 (μmol photons m^ s^)^ and 76 (±55) μmol photons m^ s^, respectively. Although phytoplankton were adapted to low irradiance, the phytoplankton in the SCM were not fully adapted to the low irradiance prevailing at those depths. P^*_ in the studied region was low (mean of 0.66 (±0.37) mgC (mg chl. α)^ h^) and generally lower than the previously reported values in waters near the Antarctic Peninsula. The maximum quantum yield varied widely, ranging from 0.001 to 0.038mol C (mol photons absorbed)^ at the surface and from 0.007 to 0.092mol C (mol photons absorbed)^ near the bottom of the euphotic zone. These values were within the range of published data. Comparison of photosynthetic parameters with historical data indicated that primary productivity from remotely sensed data for the whole of the Southern Ocean, based on these field estimates of photosynthetic parameters, has been overestimated

Distribution of nutrient salt and phytoplankton in the Antarctic Ocean

The phytoplankton standing stock and the nutrient concentration around the Balleny Islands were compared with those in the vicinity of the pack ice. The concentrations of phosphate, nitrate and chlorophyll-α fluctuated noticeably around the Balleny Islands, on the other hand, silicate concentrations fluctuated in the vicinity of the pack ice. The concentrations of phosphate, nitrate, silicate and chlorophyll-α ranged 0.86-2.10μg-at/l, 5.0-29.6μg-at/l, 57.2-69.9μg-at/l and 0.15-2.41mg/m^3 around the Balleny Islands, respectively, and ranged 1.37-2.20μg-at/l, 26.4-28.4μg-at/l, 34.5-50.1μg-at/l and 0.098-0.323mg/m^3 in the vicinity of the pack ice, respectively. The concentrations of silicate around the Balleny Islands (mean=62.3μg-at/l) were more abundant than those of observed in the vicinity of the pack ice (mean=41.5μg-at/l). The inverse relationship between the concentrations of chlorophyll-α and those of nitrate were observed in the vicinity of the Young Island. This opposite relationship may suggest that nitrate and phosphate were uptaken by phytoplankton. The maximum concentration of chlorophyll-α was observed at 66°20\u27S, 162°05\u27E, where the dominant species were Thalassiosira gravida, Chaetoceros dichaeta and Fragilariopsis kerguelensis

Primary production of phytoplankton in high Arctic Kongsfjorden, Svalbard (scientific paper)

Standing stock and primary productivity of phytoplankton were investigated in relation to the environmental conditions in high arctic Kongsfjorden, Svalbard (Norway) during the early summer of 1993,just after the sea ice melting. The concentration of chlorophyll a in the surface water showed high values only during sea ice melting (1.0-5.7μg・l^), then decreased to less than 0.5μg・l^. Daily variations of photosynthetically active radiation (PAR) ranged from 200 to 1200 μmole・m^・s^ during the study period. Even in the midnight sun, more than 20% of the daily maximum PAR was recorded. Photosynthetic activity of phytoplankton measured by the ^C stable isotope method was high (1.17mg C・mg Chl. a^・hr^) during the ice melting period, whereas that in the succeeding period was low (0.45mg C・mg Chl. a^・hr^). Daily primary production was calculated in the ice melting period and succeeding period to be 1100 and 87-119mg C・m^・day^, respectively

Photosynthetic nature of ice algae and their contribution to the primary production in lagoon Saroma Ko, Hokkaido, Japan

Photosynthetic activity of ice algae and phytoplankton was investigated under sea ice at two stations (ca. 44°10\u27N, 143°46\u27E) in lagoon Saroma Ko, Hokkaido, Japan, in early March 1987. Water temperature and salinity ranged from -1.1 to -1.4℃ and from 32.4 to 33.5, respectively. The maximum chlorophyll a concentrations of ice algae within 4cm from the bottom of sea ice and phytoplankton in water column were 385 and 0.77 mg m^, respectively. The maximum photosynthetic rate (1.12 mgO_2 mgchl, a^ h^) of ice algae was obtained under 37.5 μEm^2 s^, which corresponds to only 3% of incident solar radiation. These results demonstrate the low-light adaptation of ice algae grown under low light conditions. The optimum temperature for photosynthesis of ice algae was around 8℃. In situ measurements on a clear day gave the primary production of 1.59 mgCm^ h^ by ice algae and that of 1.92 mgCm^ h^ by phytoplankton. It was concluded that the ice algae contribute to a considerable extent to the production of organic carbon in the ice-covered area of Saroma Ko during winter