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14 STATE OF THE ESTUARY OVERVIEW • • In the Bay, concentrations of mercury in some embryos and chicks of cer- tain fish-eating birds like Forster’s terns are high enough to kill them. High mercury levels also threaten the endangered Ridgway’s rail. Water touches every aspect of the Estuary’s health. The amounts and variability of freshwater inflows from rivers and streams – defining charac- Photo: Mark Rauzon teristics of an estuary – create habitat for fish and wildlife, trigger migration and reproduction, and fuel the productivity and ecological processes that make estuaries such rich and vibrant ecosystems. However, human alterations to the watershed and within the Estuary itself, such as dams, water diversions, levees, dredging and channel- ization, have changed freshwater inflow amounts and patterns. These changes, in turn, have affected estuarine habitat, wildlife and ecological functions. There- fore, freshwater inflow conditions are useful indicators of estuarine health. Pesticides are of particular concern in urban creeks and sometimes the water bodies into which they flow, such as the Delta, where recent studies have implicated pyrethroids as the cause of toxicity to invertebrate test organisms. • • • • • • Salmon and trout caught in the Estuary are safe to eat, with levels of all measured contaminants below thresholds of concern. Striped bass, black bass, white croaker, shiner surfperch, and other spe- cies should be eaten less frequently, in accordance with state consump- tion advice, due to high levels of PCBs and mercury. Water quality is also an important indicator of the state of the Estuary. Organisms that spend their lives immersed in water or feeding from the aquatic food web are strongly affected by conditions in the water, including tempera- ture. They are also affected by levels of oxygen, contaminants, and nutrients in the water. Clean water is also essential for human use of the Estuary — as a source of drinking water and food, or as a place to enjoy swimming, windsurfing, and other forms of water recreation. Pregnant women and children consuming Estuary-caught fish are espe- cially at risk, and should carefully follow state consumption advice. The amounts and variability of freshwater inflows to the Estuary have been reduced to levels too low to support critical ecological processes or protect estuarine fish. Most of the ten indicators used in the composite Freshwater Inflow Index showed “poor” or “very poor” conditions. Water is central to the Estuary and directly influences ecological outcomes. Given that people manage or influence so many aspects of freshwater inflow and water quality, water may be our most powerful tool for restoring health to the Estuary. Human alterations to inflows have created chronic drought conditions in the Estuary that, particularly in the upstream region, impair ecological function, degrade habitat and productivity, and contribute to increasingly serious fish population declines. TAKE HOMES • Conditions at 22 of 28 Bay beaches in summer were excellent (“safe”) for water recreation most of the time in 2012 and 2013. Two San Mateo County beaches, Aquatic Park and Lakeshore Park, consistently have poor condi- tions in both wet and dry weather. S S y y • TA TE of the est u SUPPORTING MATERIALS ar y the The Estuary is in fair E T o condition s e e h t f t u in terms of providing clean f o habitat s e t u that sup- TE ar a A TA ports abundant, T diverse communities of the animal and plant species r that live in or depend upon the Bay, including algae, zooplankton, macroinverte- brates, fish, aquatic birds, and marine mammals. to be safe to drink following treatment, and monitoring and regulatory programs are important for addressing ongoing water quality challenges. S • In the Delta, source water diverted for drinking water purposes continues WildlifE Habitat TA TA SC O B AY & f the o WATER FR N NCI SA f the est o N N CISC O B AY SA SA Pollutants posing the greatest threats to the development and survival of aquatic life in the Estuary include mercury, invasive species, pesticides, and L FR FR EL trash. DE AN A & D AN TA • 2015 DE CIS C O B AY & f the o L This chapter summarizes data and materials written by the authors listed on page 12 and provided in full in the technical appendix for the State of the Estuary 2015 report. Go to: http://sfestuary.org/about-the-estuary/soter/ Water chapter pelican & fish photo: Rick Lewis