Marine Beach Water Quality

Many marine beaches in King County are located in parks that provide a source of recreation. Visitors interact with the water by swimming, wading, kayaking, fishing, and SCUBA diving. These beaches are habitat for many plants and animals that are key to a healthy environment. They provide spawning areas for several types of fish, habitat for young salmon, and are home to other marine life like seaweeds, clams, and crabs. 

Marine beaches near urban areas are vulnerable to pollution. Sources of pollution to these beaches may include stormwater pipes, combined wastewater and stormwater (CSO) outfalls, and freshwater creeks and streams. Bacteria and viruses from animal or human poop in the water can cause illnesses in people and animals that interact with contaminated water. Too many nutrients can cause marine plants to become overgrown, which can be a nuisance for people and degrade the water quality of the beach.

We test for signs of poop from humans or animals (indicator bacteria) and track nutrients, temperature, and salinity at marine beaches. We collect water samples monthly from 20 beach sites in King County waters of Puget Sound. Some of these sites have been sampled since the 1970s. Beach water samples are collected by scientists who wade into the water to knee depth and collect a water sample using a sample bottle. Observations about wildlife, beach use, and weather are collected too. Water samples are analyzed at the King County Environmental Laboratory.