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System-wide Monitoring Program
Salinity Salinity is generally defined as the total amount of dissolved solids in a volume of water. The salinity of seawater in the open ocean is remarkably constant at about 35 parts per thousand (ppt). Salinity in an estuary, however, varies according to location, tidal fluctuations and the volume of freshwater runoff. Salinity levels in estuaries are generally highest near the mouth of a river where ocean water enters, and lowest upstream where freshwater flows in. However, actual salinities at specific locations in the estuaries vary through the tidal cycle. Overall salinity levels in the estuaries decline in the spring when snowmelt and rain produce elevated freshwater discharges from streams and groundwater. Variations in salinity produce changes in species composition, distribution and abundance in an estuary. Estuarine organisms have different tolerances and responses to salinity changes. For example, benthic (bottom-dwelling) organisms are able to tolerate changing salinities, but salinities outside an acceptable range will affect growth and reproduction. Salinity is also important because it affects chemical conditions within the estuary, particularly dissolved oxygen levels. The amount of dissolved oxygen (solubility) decreases with increasing salinity. The solubility of oxygen in seawater is about 20 percent less than in freshwater of the same temperature. |
Revised March 12, 2004 by NERRS Webmaster
Ocean and Coastal Resource Management | Ocean Service | NOAA | Department of Commerce
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Ocean and Coastal Resource Management | Ocean Service | NOAA | Department of Commerce
Privacy Policy | Disclaimer http://nerrs.noaa.gov/Monitoring/WaterSalinity.html