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Scripps Contact:
Mario Aguilera or Cindy Clark (858) 534-3624 As part of the multi-pronged project, funded by the City of San Diego, Scripps researchers John Largier, Melissa Carter, and Moninya Roughan will use dye to carefully track Mission Bay water movement beginning November 13. Researchers and city officials note, however, that the bright red or green substance is absolutely non-toxic and harmless to all swimmers, wildlife, and the environment. Tracking the dye is one of several approaches the scientific team is using to trace Mission Bay water flow. Other elements of the multi-year project, called the “Mission Bay Contaminant Dispersion Study,” include meters to measure currents, instruments that measure the water’s temperature and salinity, and the use of “drifters,” underwater kites equipped with satellite GPS units that record the track along which water is flowing. “We are undertaking this project to provide information necessary to improve Mission Bay water quality,” said Largier, principal investigator of the study and an associate research oceanographer in the Integrative Oceanography Division at Scripps. “This project will add much value to the on-going monitoring of bacteria levels in Mission Bay. When polluted water is found at a given position, the results of this study will help officials know the spatial extent of pollution and, even better, understand where the pollution could have come from. That’s the most exciting aspect of this project. If we know where the pollution is coming from, we can go after the source and reduce pollution inputs to the bay. That’s the ultimate aim.” Karen Henry, of the City of San Diego’s Storm Water Pollution Prevention Program, which is overseeing the Scripps study, said: “The goals of the study are to understand where pollutants, in particular fecal bacteria, travel when introduced into the bay, how long they remain there, how quickly their concentrations are diluted, and to identify which parts of the bay are most susceptible to pollutant events.” The researchers will follow the November 13 testing with additional dye releases through December 24. The data gathered will be integrated into a computer model that will aid in predicting how pollutants move through the bay. The field observations and model output will be used to explore scenarios, specifically to determine the zones most impacted by contamination events. These zones can then be used to guide County health officials with decisions on contamination postings, beach closures, and responses to spill events. Largier’s team will use Fluoroscene and Rhodamine FWT, harmless, non-toxic dyes that can be used to color most anything, somewhat similar to food coloring. Such dyes can be found in many everyday products. “In some ways, using dye is the ultimate measurement of water motion,” said Largier. “Over time we will map out the shape of the dye patch, which is moving and deforming. The important part of it is that we are directly measuring the concentration in parts per million. We can measure the flow and dilution—not just look at the interesting patterns and see how visible it is. That’s really where the science is.” Using a multi-faceted approach will give the science team vital information on understanding fundamental aspects of the underlying mechanisms of the Mission Bay aquatic system. “In a general sense, everything
in aquatic ecosystems and water-based environments is subject to the flow
of water,” said Largier. “Even fixed plants require water
to bring them nutrients and animals that live on a rocky reef require
water to bring food to them. Everything is carried by water. It integrates
and connects everything, so the water movement is a fundamental component
in understanding how any water-based system works.”
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