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Title: Spatial and temporal variability in the water column nutrients and pesticides of Jobos Bay

item WHITALL, DAVID - National Oceanic & Atmospheric Administration (NOAA)
item DIEPPA, ANGEL - National Oceanic & Atmospheric Administration (NOAA)
item Potter, Thomas

Submitted to: National Oceanic and Atmospheric Administration
Publication Type: Government Publication
Publication Acceptance Date: 7/1/2011
Publication Date: 7/1/2011
Citation: Whitall, D.R., Dieppa, A., Potter, T.L. 2011. Spatial and temporal variability in the water column nutrients and pesticides of Jobos Bay. In: Whitall, D.R., Costa, B.M., Bauer, L.J., Hile, S.D., editors. A baseline assessment of the ecological resouces of Jobos Bay. National Oceanic and Atmospheric Administration Technical Memorandum NOS NCCOS 113, Silver Spring, MD. p. 188. Available:

Interpretive Summary: Agriculture is a primary land-use in the Jobos Bay National Estuarine Research Reserve (JBNERR) watershed located on Puerto Rico's southeast coast. There are continuing concerns that farmland within the watershed may be contributing agrochemical residues to the estuary and bordering wetland habitats. To assess potential impacts water quality monitoring was conducted over 2.5 years. This work was conducted cooperatively with National Oceanic and Atmospheric Administration and JBNERR staff and was part of Conservation Effects Assessment Program Jobos Bay Special Emphasis Watershed project. Findings suggested that both phosphorous and pesticides residues are being discharged to the estuary in surface water drainage associated with tropical storm events. We conclude that mitigation measures including storm water detention and treatment, and improved pest management practices are needed to protect critical JBNERR habitats.

Technical Abstract: The Conservation Effects Assessment Project (CEAP) is a national, multi-agency effort to quantify the environmental benefits of best management practices used by agricultural producers participating in selected U.S. Department of Agriculture (USDA) conservation programs, including programs such as the Conservation Reserve Program and the Wetlands Reserve Program. The Jobos Bay Watershed, located in south-central Puerto Rico, was selected by CEAP partners as the first tropical CEAP Special Emphasis Watershed. The CEAP effort included a baseline assessment of Jobos Bay (Puerto Rico) and surrounding marine ecosystems conducted cooperatively by National Oceanic and Atmospheric Administration’s (NOAA) Center for Coastal Monitoring and Assessment (CCMA), U.S. Department of Agriculture’s (USDA) Agricultural Research Service (ARS) and the Jobos Bay National Estuarine Research Reserve (JBNERR). Specific objectives of this portion of the ecological characterization project of Jobos Bay were to: a) quantify magnitude and spatiotemporal variability of surface water nutrients and pesticides within the JBNERR; b) establish a baseline of nutrient and pesticide conditions against which to measure changes in the future; and c) link observed concentrations of nutrients and pesticides to hydrological forcing factors. Water quality monitoring was conducted at six stations within the estuary over a period of 2.5 years. Water samples were tested for dissolved nitrogen (N) and phosphorous (P), chlorophyll and 32 pesticides and degradates. The nutrient (N and P) and chlorophyll concentrations were within the range reported for other estuaries in southern Puerto Rico. Seasonal variations in N and P at near shore stations were observed with the highest N concentrations found in the dry season and the highest P levels during the wet season. Results suggest that groundwater seepage was a source of N in these samples and that P is being delivered to the estuary by stormwater runoff. Stormwater runoff also appeared to be the principal source of pesticides detected. Relative high levels of the herbicide atrazine were found in near shore station samples collected after a tropical storm passed through the area in August 2008. The herbicide had been applied to farm fields adjacent to the reserve 4 days prior to the arrival of this storm. These data show that non-point source contaminants (nutrients and pesticide residues) are being transported from the watershed to the estuary and that transport is linked to both groundwater discharge and stormwater runoff. Findings will be used to evaluate the efficacy of and planning for implementation of watershed best management practices designed to minimize impacts to estuary water quality and habitats.