Aquatic Ecology

The effect of selenium toxicity on wildlife has been known for more than 50 years. This issue drew particular attention in the 1980s when embryo deformity and mortality was observed in birds at a wildlife refuge in California. Harmful effects from selenium were determined to be connected to irrigation drainage water. As a result, an effort began to monitor levels of selenium in irrigation drainage...

Drought is making the Delta Saltier. Less freshwater coming from watershed runoff and reservoir releases means that more salty water flows into the Sacramento San Joaquin Delta (Delta) from the Pacific Ocean. Changes in Delta salinity have far-reaching impacts, affecting the water supply for agriculture, drinking, wildlife, and Delta ecosystems.

The USGS California Water Science Center conducts a variety of research activities at Clear Lake, California, including surface-water monitoring and water quality and aquatic habitat studies.

The Clear Lake Hitch ( Lavinia exilicauda chi ) population, which once flourished in great abundance, has been decimated by loss of spawning habitat, nursery areas, and the encroachment of non-native species. In order to make an informed decision, the California Water Science Center has been asked by the U.S. Fish and Wildlife Service to conduct studies into the fish’s habitat, specifically...

The San Francisco Bay and Sacramento-San Joaquin Delta form one of the largest estuaries in the United States. Water flow and water quality in the San Francisco Bay-Delta Estuary are important to the economies of both California and the nation. The Bay-Delta system provides water to more than 25 million California residents and vast farmlands, as well as key habitat for birds, fish, and other...

Longfin Smelt ( Spirinchus thaleichthys ) is a pelagic fish species found in waters along the Pacific coast, from Alaska to central California. Its complex life cycle makes it vulnerable to threats in both freshwater and at sea. Longfin Smelt is listed as a threatened species by the state of California.

Many non-native fish, invertebrates, and plants have colonized the Sacramento-San Joaquin Delta (Delta) of California, the landward most region of the San Francisco Estuary. Included among these invasive species is the water primrose ( Ludwigia spp . ), an aggressive floating aquatic plant that is native to South and Central America and parts of the US, but invasive in California. Water primrose...

Phytoplankton comprise the bottom of the aquatic food web and the abundance of phytoplankton serves as an indicator of healthy aquatic habitats. In the Sacramento-San Joaquin River Delta (Delta), competing with phytoplankton for required nitrogen, invasive aquatic vegetation (IAV) has increased exponentially in recent years. Once established, IAV can negatively impact local ecosystems and...

Tidal marshes are important ecosystems in the San Francisco-Bay Delta. They remove carbon from the atmosphere, they build up soils that buffer our communities from sea level rise, they provide critical habitat and food resources for a diversity of species, and they reduce excessive nutrients which have a negative impact on water quality. As a result of land-use change and urbanization, the San...

The abandoned Sulphur Bank Mercury Mine on the shores of Clear Lake in Northern California has been designated as a "Superfund Site" by the U.S. Environmental Protection Agency (EPA). This means that the EPA has determined that the area is contaminated by hazardous waste and requires cleanup because it poses a risk to human health and/or the environment. One of the chief contaminants at the site...

Suisun Bay is an area identified as critical habitat for the threatened Delta Smelt. Several important changes in the pelagic food web of this area have been documented over the last two decades indicating that food for Delta Smelt and other threatened fishes is in short.

Prior to 2000, the four most abundant resident pelagic fishes in the study area included two native species, delta smelt (Hypomesus transpacificus) a federal listed endangered species, and longfin smelt (Spirinchus thaleicthys) a state listed endangered species, and two introduced species, threadfin shad (Dorosoma petenense) and age-0 striped bass (Morone saxatilis).