ISSN:
1365-2427
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
SUMMARY. The ecology of the phytoplankton of Heywood Lake, Signy Island, South Orkney Islands, Antarctica was investigated during 1969–72. The lake, which is ice-covered for 8–10 months per year, is moderately eutrophic due to enrichment by seal excreta.The annual cycle of the phytoplankton is described. During the winter (approximately May-September), very few algal cells could be detected in the water column and 14C fixation was below measurable limits. In spring (October-November), a rapidly-growing population of algae caused a large increase in the chlorophyll-a concentration (maximum value 170 mg m−2) but carbon fixation remained low, with values 〈500 mg C m−2 day−1. The algae contributing to this peak were mainly small chlorophytes and chrysophytes. The summer open-water period (December-March) was characterized by a different phytoplankton population dominated by cryptophytes. Chlorophyll levels were lower (c. 40 mg m−2) but 14C fixation rates 〉3 g C m−2 day−1 were measured on bright days. Values for Assimilation Number were very high (maximum value 10.5 mg C h−1 mg−1 (chlorophyll-a) in January (1971) though temperatures never exceeded 8°C. In autumn, the phytoplankton regressed to winter levels. Both spring and summer algal populations probably overwinter as resting stages.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1365-2427.1981.tb01239.x
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