Estuarine and Lagoon Conditions

Importance to Salmonids

Estuaries and lagoons are critical to adult and juvenile coho salmon (Oncorhynchus kisutch) and steelhead trout (O. mykiss). Young salmonids use estuaries as nursery habitat and as a physiological transition zone in which to prepare for life in the marine environment. Lagoons and estuaries are important as rearing habitat, especially in small coastal streams such as those in San Mateo and Santa Cruz Counties, where freshwater rearing habitat is often limited. Smith (1990) suggests that lagoon areas may produce the majority of smolts from these small coastal stream systems. Because of intense predation pressure and the need for large amounts of food resources prior to out-migration, estuarine conditions are ideal when characterized by high levels of habitat complexity and abundance of macroinvertebrates. Adults use estuaries as a place to rest and feed prior to starting their upstream migration. Upstream migration of adults is often triggered by high outflow in combination with high tides.

A lagoon and sand bar have formed near the mouth of Scott Creek – a coho and steelhead bearing stream in Santa Cruz County.

Estuaries and lagoons in San Mateo and Santa Cruz Counties tend to be small, with large fluctuations in freshwater levels and the formation of a sandbar during summer and fall low flow periods. In general, fish diversity increases with lagoon size in this area, and salmonid viability in these lagoons is dependent upon a complex interaction of physical and biotic features and processes, including temperature, salinity, dissolved oxygen, hydro-geomorphology, large wood, phytoplankton, aquatic vegetation, invertebrates, and so forth.

Human Impacts

Human impacts to lagoons and estuaries vary widely, depending upon the watershed that the estuary drains, as well as localized land uses. Some estuaries are downstream of relatively undeveloped watersheds, whereas others are situated at the mouth of river systems characterized by substantial upslope disturbance from agriculture, logging, and urbanization. These land uses may result in excessive levels of sediment, loss of large wood, modification of freshwater inflows, or the influx of pollutants. In addition to watershed land use impacts, local lagoon-specific impacts such as artificial sandbar breaching can cause imbalances in fresh and saline ratios, and allow predators into the estuarine area. Other direct impacts to estuaries and lagoons in the area include diversion for agricultural and municipal uses and diking of surrounding wetland areas. There are three harbors within the study area – the Santa Cruz, Moss Landing, and Pillar Point Harbors – that also impact lagoons and estuaries by altering sand deposition patterns and near-shore ocean currents, and increasing pollutants. These permanent structures require deep-water access, regular dredging, and the construction of support structures such as jetties and seawalls that interfere with the natural ebb and flow of estuary and beach boundaries (Brazil 1998; CCS 2004). Boat maintenance, repair, and refinishing in harbors contribute oils, lubricants, cleaning solutions, paints, and dust to the waters (CDFG 2003). Finally, bridges, such as the Highway 1 bridge over Scott Creek, may influence bar breaching, potentially delaying upstream migration in the winter, and causing premature sandbar closure in the spring.

References

Brazil, E. 1998. Slowly but surely, erosion eats away at California's beachfront property. San Francisco Examiner. View on-line source.

California Department of Fish and Game (CDFG). 2003. "Market Squid Fishery Management Plan." View on-line source.

Center for Coastal Studies (CCS). 2004. Coastal Erosion [Web site]. Scripps Institution of Oceanography [cited 2003]. View on-line source.

Smith, J.J. 1990. "The Effects of Sandbar Formation and Inflows on Aquatic Habitat and Fish Utilization in Pescadero, San Gregorio, Waddell and Pompinio Creek Estuary/Lagoon Systems, 1985-1989." Department of Biological Sciences, San Jose State University.

Local References

Swanson Hydrology and Geomorphology, Native Vegetation Network, and Hagar Environmental Science. 2002. "Lower San Lorenzo River and Lagoon Management Plan." Prepared for City of Santa Cruz Redevelopment Agency, San Lorenzo Urban River Task Force, City of Santa Cruz, State Coastal Conservancy.

Habitat Restoration Group. 1990. "Soquel Lagoon Management and Enhancement Plan." Prepared for City of Capitola, Santa Cruz County, California Coastal Conservancy, California Department of Fish and Game, 67 (plus appendices) pp.

General References

Nielsen, J.L., P. Goodwin, C.K. Cuffe, and T. Light. 1994. "Russian River Estuary Study, 1992 - 1993: Hydrologic, Limnilogical, and Biological Aspects of an Estuary Management Plan." Planning Department of Sonoma County. 186 (plus appendices) pp.

Goodwin, P., J.L. Nielsen and C.K. Cuffe. 1993. The tidal Inlet characteristics of a small California Estuary. Hydraulic Engineering 93:562-567.

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