ECOSYSTEM

California's Ocean Ecosystem

California's Ocean Ecosystem

Introduction

Habitats within California's ocean ecosystem contain some of the most biologically diverse natural communities in the world. The abundance of species and habitats located offshore California can be attributed to the inter-relationship of the identified resource zones located both onshore and offshore. Onshore, an extensive system of inland waterways provide habitat for various marine species, as well as freshwater and nutrient flows. Offshore, several major oceanic factors, such as the California and Davidson Currents and a hydrological phenomenon known as upwelling, contribute essential nutrients to nearshore and deep ocean waters. It is beyond the scope of this analysis to fully identify the many factors affecting the diversity of biological resources off the California coast. However, the analysis does describe the major interactions between different ocean resource zones, how these interactions affect diversity, and the fact that modifications in one zone may strongly influence biological processes in other zones located miles away.

For descriptive purposes, the habitats which make up California's ocean ecosystem have been grouped into four zones:

inland watershed zone, extending from the watersheds of the Sierra Nevada to the California shoreline;

enclosed waters zone, including waters and habitats of bays, estuaries, and subtidal areas;

nearshore ocean zone, including nearshore open coastal waters out to a depth of 100 meters; and

offshore ocean zone, extending from a depth of 100 meters to the edge of the Exclusive Economic Zone (200 miles offshore).

Inland Watershed Zone

California's extensive inland watershed zone consists of approximately 7,800 miles of rivers, creeks and drainages, traversing a rich variety of climatic, geographic, sedimentary and topographic conditions as they meander towards the Pacific Ocean. These waterways play a critical role in providing freshwater flows which support anadromous fish and dependent habitats, such as coastal wetlands and nearshore coastal waters.

The health and productivity within California's inland watershed zone depends on the appropriate distribution of sediments, adequate vegetation along waterways, and sufficient flows of freshwater to the system. Coniferous forests, common along northern streams and in the upper reaches of most watersheds, function to retain topsoil and prevent sediment loading in rivers. When sediment loads increase, stream channels and associated wetlands may lose their effectiveness for flood control and wildlife habitat. Riverside forests and riparian woodlands provide nutrients, shade, and channel stability, permitting river waters to support spawning and the survival of young fish, such as salmon.

Freshwater wetlands, also common to the inland watershed zone and often associated with rivers, are important for controlling and reducing the effects of peak flood flows, breaking down pollutants from contaminated waters, providing fish and wildlife habitat, and settling sediments before they reach coastal or urbanized areas. Adequate stream flow and water quality are required for anadromous fish to reach their spawning grounds, successfully spawn, rear to emigration size, and safely reach the ocean. Numerous fish species spend most of their lives in the ocean, but are seasonally dependent upon rivers and streams for reproduction. Known as anadromous fish, these species include the coho and chinook salmon, steelhead trout, American shad, striped bass ...