Role of nutrients and zooplankton grazing on phytoplankton growth in a temperate reservoir in New South Wales, Australia

Tsuyoshi Kobayashi*, Anthony G. Church

*Corresponding author for this work

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

The role of nitrogen (N) and phosphorus (P) and zooplankton grazing on the growth of a phytoplankton community was investigated at different times in the Ben Chifley reservoir. In situ nutrient enrichment bioassays (n = 12) indicated that phytoplankton growth was limited by P in 33% of experiments, by both N and P in 25% of experiments and no limitation was found in 42%. The hypothesis that N or P limitation occurred when ambient N:P ratios were different from the Redfield ratio was supported in 33% of bioassay experiments, suggesting that ambient N:P ratios do not always correctly indicate if N or P is limiting. Grazing rates of the reservoir zooplankton (>150 μm in size) ranged from 0.023-0.199 day-1 (mean: 0.078 day-1, n = 8). The grazing efficiency, as measured by a weight-specific clearance rate, ranged from 0.049-0.743 mL μg dry wt-1 day-1, and was positively correlated with the relative biomass of Daphnia in the community. The nutrient-stimulated growth of phytoplankton ranged from 0.085-1.031 day -1 (mean: 0.461 day-1, n = 10). The effect of nutrient enrichment exceeded that of zooplankton grazing in 62% of experiments. Further study is necessary to understand a qualitative effect of nutrients and zooplankton grazing on the phytoplankton community structure in the Ben Chifley reservoir.

Original languageEnglish
Pages (from-to)609-618
Number of pages10
JournalMarine and Freshwater Research
Volume54
Issue number5
DOIs
Publication statusPublished - 2003
Externally publishedYes

Keywords

  • Ben Chifley reservoir
  • Calanoid copepods
  • Chlorophyll a
  • Daphnia
  • Interactive effect
  • Nitrogen
  • Phosphorus

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