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Primary productivity of the upper reaches of a South African estuary (Swartvlei)

1976; Elsevier BV; Volume: 24; Issue: 1 Linguagem: Inglês

10.1016/0022-0981(76)90046-0

1879-1697

Richard D. Robarts,

Aquatic Ecosystems and Biodiversity

Primary productivity, using the 14C technique was measured in the expanded lake-like upper reaches of a South African estuary during 1972. Maximal assimilation per unit volume ranged between 5.0 and 13.1 mg C m−3 h−1 and areal productivity ranged between 13.1 and 36.9 mg C m−2 h−1. For most of the period the euphotic zone (level of 1% of surface light) extended to only 4.5 m. The poor light conditions in the estuary were due to the heavy content of humic material and suspended detrital matter. Light, therefore, was a major factor limiting primary productivity. The PO4-P concentration reached an undetectable level following a large diatom increase and nutrient limitation may have occurred. The phytoplankton population of the upper reaches of Swartvlei was dominated by nannoplanktonic (< 60 μm) diatoms and dinoflagellates. The ecological advantages that these small organisms might have in an environment such as Swartvlei are discussed.