Creation and breakdown of Narragansett Bay lecture

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Lecture: Creation and breakdown of Narragansett Bay density stratification, and its role in deep oxygen depletion

NARRAGANSETT– September 19, 2007 — Environmental conditions have at times deprived the fish that inhabit Narragansett Bay of the oxygen they need, leading to dramatic fish kills. The layered structure of Bay waters due to density stratification plays a central role in deep oxygen depletion, known as hypoxia.

Determining when stratification strengthens or weakens, and understanding the processes responsible, is of great interest to scientists, fishermen, and resource managers, says Dan Codiga, University of Rhode Island (URI) oceanography research associate. He will present his research in a lecture, “Fresher Over Saltier: Stratification and Hypoxia in Narragansett Bay,” on October 4 at 6:30 p.m. in the main auditorium of the URI Graduate School of Oceanography Coastal Institute in Narragansett.

Near-surface bay waters receive oxygen from the atmosphere, and tides and wind can mix that oxygen-rich water with deeper water, distributing oxygen throughout. However, freshwater enters the Bay from rivers, creating density stratification that impedes mixing of the shallow, fresher layers of water with the deeper, saltier layers.

As part of a project funded by NOAA’s Coastal Hypoxia Research Program,

Codiga analyzes measurements of Bay temperature, salinity, tidal heights, winds, and river runoff, to come up with models for how stratification evolves.

“We use this modeling to understand where stratification occurs and how long it lasts,” Codiga says. “Our rationale is to first be able to hindcast stratification events, then assess the feasibility of forecasting. The same modeling approach developed for stratification can then be taken for oxygen concentrations to better understand hypoxia.”

The lecture is part of Coastweeks, the annual nationwide celebration of the coast. For more information, visit, contact Codiga at, or call Rhode Island Sea Grant Communications at (401) 874-6842.

Coastweeks in Rhode Island is sponsored by the R.I. Coastal Resources Management Council and Rhode Island Sea Grant. To receive the free calendar of events, contact Rhode Island Sea Grant Communications at (401) 874-6842.