Planktonic and Benthic Foodweb Research

foodweb conceptual diagram

Conceptual diagram of the effects of food web structure on grazing control of small and large cell size dinoflagellates.

Coupling phytoplankton production to fish is principally through the micro- and mesozooplankton links in estuaries. We propose to develop indicators of ecosystem condition from short and long -term trends of zooplankton abundance and species composition in Chesapeake Bay. Hypothesized secular changes in mesozooplankton abundance in response to nutrient over-enrichment will be tested with archival data from monitoring and optical data from contemporary sampling. We propose to develop predictive relationships between optical measurements of phytoplankton biomass from remote and in-situ sensors, with zooplankton abundance and community composition. We will begin analysis using Chesapeake Bat data and begin to incorporate available data from other ACE INC estuaries. We hypothesize that physical parameters, photopigments, and other optical properties can be used as indicators to predict zooplankton abundance and community composition.

Zooplankton as Indicators of Climate Change and Trophic Change in Estuaries

Spatial and temporal changes in zooplankton community composition and abundance have been observed in response to freshwater input in the Chesapeake Bay. In order to determine how freshwater flow directly impacts zooplankton species in the Chesapeake Bay, statistical models were constructed from long-term monitoring data. The purpose of the models was to identify how changing estuarine conditions that accompanied increases or decreases in freshwater input impacted zooplankton dynamics. Significant deviations from the models were found for particular time periods and correlated with water quality conditions. Time periods showing the strongest deviations from the model were typically “wet” or “dry” years. Therefore, we believe that zooplankton may be used as indicators of changes in estuarine condition that relate to freshwater discharge.

size spactra summary charts

Figure 2. Biomass size spectra slope values for each 3 regions of Chesapeake Bay. Size spectra slope may be used as an indicator of nutrient reduction efforts and their impacts on zooplankton.

Zooplankton may be used as indicators of trophic condition. We have recently focused on the use of biomass size spectra as an indicator of zooplankton response to changes in Chesapeake Bay ecosystem. The distribution of zooplankton biomass in Chesapeake Bay appears to vary significantly throughout the year. The slope of the size spectra appears to vary with hydrologic conditions, including nutrient inputs, thus may serve as a tool to assess the efficacy of nutrient reduction efforts. The zooplankton size spectra will be combined with phytoplankton and fish size spectra in order to create a whole ecosystem based indicator.

Chesapeake Bay zooplankton co-varied with regional weather patterns calculated from data on sea level pressure. Particular weather patterns impacted the Chesapeake Bay region differently, causing variations in temperature, precipitation, cloud cover, etc.

Weather pattern anomalies were calculated and correlated with shifts in mesozooplankton abundance and community composition. Winter-spring weather conditions appeared to influence the distribution of zooplankton in the spring and summer. We are currently using synoptic climatology to predict the water balance for the Susquehanna River Basin. This will allow prediction of the magnitude of the spring freshwater input and be used to drive models of zooplankton dynamics that rely on freshwater input as a major driver. Thus, the prediction of zooplankton response to weather patterns is possible.

Principal Investigators

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