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INTERACTIONS BETWEEN NUTRIENTS,PHYTOPLANKTON GROWTH AND MICROZOOPLANKTON GRAZING RATES IN A GULF OF MEXICO ESTUARY
Citation:
Juhl, A R. AND M C. Murrell. INTERACTIONS BETWEEN NUTRIENTS,PHYTOPLANKTON GROWTH AND MICROZOOPLANKTON GRAZING RATES IN A GULF OF MEXICO ESTUARY. AQUATIC MICROBIAL ECOLOGY 38(1):147-156, (2005).
Impact/Purpose:
To experimentally measure phytoplankton growth rates and microzooplankton grazing rates under in situ and nutrient-replete conditions.
Description:
Juhl, Andrew R. and Michael C. Murrell. Submitted. Phytoplankton Growth and Microzooplankton Grazing in a Gulf of Mexico Estuary. Aquat. Microb. Ecol. 38(1): 147-156, 2005.(ERL,GB 1214).
Dilution grazing experiments were conducted on 9 dates over a 16-month period in Santa Rosa Sound (Florida, USA) measuring microzooplankton grazing (m), and phytoplankton gross-growth rates under in situ (?0) and nutrient-replete (?n) conditions. The rates were measured on four phytoplankton fractions, including: bulk, large (>5 ?m), small (<5 ?m), and cyanobacteria. Grazing rates were positively correlated with both ?0 and ?n; the relationship of ?0 and m was nearly 1:1, while ?n always exceeded m. The 1:1 relationship between ?0 and m implied that microzooplankton grazing accounted for essentially all in-situ growth (?0) of phytoplankton, allowing no net accumulation of phytoplankton fractions, ?0 < ?n, indicating persistent nutrient limitation. Results suggest that additional nutrient influx to the environment would generate a disparity between microzooplankton grazing and phytoplankton growth ( ?n) rates, resulting in increased biomass in all phytoplankton fractions. The large fraction exhibited the highest ?n, suggesting that increased nutrient availability would lead to greater dominance by larger eukaryotic phytoplankton. This predicted increase in dominance by larger phytoplankton was experimentally observed after nutrient additions. Temperature was strongly correlated with grazing rates on, and gross-growth rates of, cyanobacteria, but not the other phytoplankton fractions.