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Technical Report

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Nitrogen, Phosphorus, Enclosures, Lakes, Phytoplankton, Algae, Standing crop, Limiting factors, Eutrophication, Bioassay


An in situ experimental procedure and protocol was developed to evaluate nitrate and phosphate enrichment using isolated indigenous phytoplankton assemblages during different seasons. Results of the comparison of the parameters-temperature, pH, alkalinity, conductivity, and dissolved oxygen between the open water and enclosed systems indicated that there was no significant influence of the physicochemical factors on the isolated biological processes. Growth responses were measured by turbidity, biomass and chlorophyll-a, the most sensitive being chlorophyll-a. Additions of nitrate and phosphate were added in known concentrations and in different magnitudes of concentration based upon ambient conditions and ratio. During the fall, phosphorus influenced phytoplankton growth, whereas in the spring both nutrients effect growth response equally, and in the summer nitrate had the greatest influence. Based upon the results of these experiments a sampling regime for physicochemical parameters and growth response is recommended.

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