Part III II
Water Quality and Waste Treatment
Microorganisms in sediments and mudflats of estuaries, bays and near-shore submerged lands break down human and animal wastes.32 They can also detoxify petroleum products and chemicals harmful to human health. The physical destruction of habitat, alteration of food webs or overload of nutrients or waste products disrupts disease regulation and waste processing services. Alteration of ecosystems can also create breeding sites for disease vectors where they were once nonexistent. People can be exposed to disease in coastal areas through direct contact with bacterial or viral agents while swimming or washing in fresh or saltwater, and by ingesting contaminated fish, seafood or water. Water quality is extremely important to healthy native fish and wildlife populations. Because most aquatic biological processes are limited by nitrogen and phosphorous, changes in these nutrient levels may have significant effects on ecosystems. For example, increases in nutrient loading in Hood Canal due to failing septic systems have caused low dissolved oxygen, or “dead zones,” where fish cannot survive. Land-use patterns also play an important role. Researchers have found that more agriculturally active and heavily urbanized watersheds contribute three times the nitrogen and phosphorous loads to Puget Sound waters than the forested watersheds in the Olympic Mountains.33 Wetlands, estuarine macroalgae and nearshore sedimentary organisms play a crucial role in removing nitrogen and phosphorous from water.32; 34 Local Example: • Many MPT parks serve this filtration function, helping to purify residential water runoff containing chemicals from lawn fertilization. Both Swan Creek and Puget Creek are deep canyons surrounded by homes and businesses. Water running through these canyons is naturally filtered before it enters Puget Sound.
Economic Impact of Metro Parks Tacoma Ecosystem Services
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