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Sport Fisheries Restoration in Puerto Rican Reservoirs - Water Quality


Wes Neal, Robert Kröger

Graduate Student(s):  Nick Peterson, Clint Lloyd, Karina Olivieri-Velazquez, Cynthia Fox (Ph.D.)

This project between Mississippi State University and Puerto Rican Department of Environment and Natural Resources hopes to improve sport fisheries in respective reservoirs by understanding the underlying water quality potential of each reservoir. This project was funded in October of 2009 and will run for 5 years, and is expected to be completed by December 2013. It is important to understand the water quality component of Puerto Rican reservoirs (e.g. Cerrillos, Luchetti, Dos Bocas, and Guajataca) to provide an understanding of the underlying biogeochemistry potentially affecting both trophy largemouth bass populations, but more importantly the affect on prey (threadfin shad) production. Spatial and temporal changes in concentrations of contaminants (nutrients, sediments and agro-chemicals) will influence basic autotrophic dynamics with a cascading effect through the food web. Reservoir drawdown has an impact on sediment biogeochemistry though changes in microbial community structure (desiccation), and nutrient biogeochemistry.

Some important questions that need to be addressed include:

  1. What water quality characteristics are associated with varying reservoir watershed land use categories in Puerto Rico?
  2. Are there associated water quality concerns with reservoir outflows and downstream ecosystems and coastal ecosystems?
  3. Are threadfin shad population characteristics correlated with certain water quality parameters?
  4. Are bass population problems associated with "poor" water quality? Or temporal changes associated with drawdown and reflooding?

Getting a basis for the water quality characteristics of Puerto Rican reservoirs will provide data for understanding the drivers of water quality in times of drawdown, extreme climatic influence (i.e. hurricanes) or "normal" conditions. These data will also be of use when climatic variation and drawdown conditions lead to abnormal reservoir conditions (i.e. nutrient turnover, increased turbidity, change in fish populations). These data will provide endpoints to return the system to, or endpoints to compare systems trajectories and mirrored fish population dynamics.

These questions will be answered by conducting comprehensive survey of water quality parameters on a spatial and temporal basis. The spatial component will include a 3-D coverage of the lake (lake surface area, and varying depths). The temporal component will monitor changes through seasons and reservoir management cycles. The suite of parameters would include nitrate-N, nitrite-N, ammonium, dissolved reactive phosphorus, total phosphorus, total organic carbon (dissolved and suspended), pH, temperature, conductivity, alkalinity and total suspended sediments (dissolved and particulate). Agrochemicals will be analyzed from water and selective sediment samples for a suite of 17 pesticides. Reservoir sediments, especially those susceptible to oxygenation and aeration through drawdown will be fractionated to determine important biogeochemical parameters associated with contaminant transformations. GIS and remote sensing technology will provide detailed analysis of land use in respective reservoir watersheds as well be used on a temporal basis for change analysis. These data, in conjunction with fish population characteristics data will provide comparisons for: land use and water quality; fish population structures and water quality (across varying spatial and temporal scales) ; initial establishment of suite of environmental variables, fish species and structure to develop thresholds of potential concern of environmental variables in reservoirs; temporal and spatial analysis of water quality; temporal changes in sediment biogeochemical characteristics mirroring drawdown in the summer (in conjunction with microcosm work in phosphorus sediment exchange mechanisms).

Outputs

Gulf of Mexico Research

Completed Projects