California’s Marine Eco-Regions

By Terry Tillman

Macrocystis Kelp

Macrocystis Kelp, photo by Andrew Weltz

The western edge of California forms a coastal ribbon that contains some of our planet’s most productive marine ecosystems. These ecosystems host a myriad of plant and animal assemblages on a scale that exceed the world’s tropical rainforests.  Spanning the length of the State, the marine region includes over 1,100 miles of coastline that is home to many diverse habitats including giant kelp forests, rocky intertidal zones, shallow seagrass meadows, and estuarine marshes.  Though California’s marine region extends only three miles seaward, to the limit of the State’s jurisdiction, this area nonetheless boasts an incredibly rich and complex ocean environment that is ever changing.

California map showing coastal habitatsThe entire marine region can be subdivided into four smaller eco-regions, North Coast Marine Eco-Region, North Central Coast Marine Eco-Region, Central Coast Marine Eco-Region, and the South Coast Marine Eco-Region.  These smaller regions follow logical divisions in water movement or fish assemblages occurring along the coast at:  Point Arena, Pigeon Point, and Point Conception.

Further divisions within the smaller eco-regions are necessary to embrace the unique habitats and conditions within each region in order to have meaningful discussion of conservation strategies.  Thus each

Beach wrack debris at the mouth of the Eel River

Beach wrack debris at the mouth of the Eel River, photo by Andrew Weltz

eco-region is divided into broad ecosystem categories to identify and evaluate threats and stresses for each category.  These broad ecosystems are: 1) Bays, Estuaries and Lagoons; 2) Intertidal Zone; 3) Nearshore Zone (0-30m); 4) Mid Depth Zone (30-100m); and 5) Deep Zone (>100m).  Within these ecosystems, three focal conservation targets were identified in the State Wildlife Action Plan update process as most critical to the development of conservation strategies:

  • Bays, Estuaries and Lagoons: bay surface area at high tide, bay islands, estuarine habitats at the mouth of watershed tributaries, and estuarine waters, tidelands, tidal marshes, and submerged habitats.
  • Coastal Intertidal: all coastal habitats that are subject to periodic tidal inundation, including rocky and sandy intertidal communities from the splash zone to the lower intertidal, and beach wrack (“Wrack” refers to the piles of seaweed, terrestrial plants, and driftwood that wash ashore.)
  • Nearshore Marine: benthic sub-tidal habitats out to 30 meters and the top 30 meters of the water column (euphotic zone) out to 3 nautical miles, including coastal nearshore habitats around islands.
Eel grass

Eel grass, photo by Kirsten Ramey

Nutrient rich waters flow through these diverse habitats, supporting abundant marine wildlife that live both in and above the water.  Eel grass beds, kelp forests, sub-tidal reefs, sea mounts, canyons, expanses of fine grain sediments or sandy sea floor, and open water zones are home to a dazzling array of marine animals.  Between the high-tide and low-tide marks, rocky and sandy intertidal zones provide a home for organisms that spend part of their life out of the water.  Above high-tide, sandy beaches, headlands, estuaries, rocky shorelines, offshore rocks, and islands serve as vital habitat for marine plants, birds, and mammals – and provide spectacular scenery for those fortunate enough to visit these shores.

Alongside this broad array of habitat types and biological assemblages lives the heart of a pulsing state economy with coastal-dependent industries that host various human activities.  The 220,000 square miles of combined State and Federal ocean waters off California sustain some of the busiest shipping lanes and ports in the world.  The marine region is home to multi-million-dollar commercial and recreational fisheries and tourism industries, and also provides unparalleled opportunities for wildlife viewing and recreation.

California halibut

California halibut, photo by Travis Tanaka

Our diverse coastal ecology and economy offer compelling reasons to want to live in California.   So much so, that 80 percent of the State’s estimated 38 million residents live within 30 miles of the coastline.  Not surprisingly, along with the variety of features and diversity of uses, a myriad of environmental stressors to the state’s coastal region has emerged.  California’s marine ecosystems face numerous threats including pollution, habitat destruction, invasive species, fishing pressure, bioaccumulation of toxins, climate change and associated sea level rise and ocean acidification.

The pressures on our marine regions that exist at the interface between human development and the ocean are similar the world over.   However, it is this same diversity and richness of California’s marine region that present unique challenges to its conservation.  Because California’s marine region is of global importance as an area of intense productivity and biodiversity, what occurs here can affect and ripple throughout the Pacific Ocean.  Moreover, an ever- increasing population in California adds a rising level of pressure on this valuable marine resource.

Critical threats that have emerged in evaluating the three critical focal conservation targets (Bays, Estuaries, and Lagoons; Coastal Intertidal; and Nearshore Marine) include:

  • Climate change (a major contributor being anthropogenic greenhouse gases).
  • Diversions and control of freshwater inputs to estuarine systems such as suspended sediments and fluid flow kinematics.
  • Pollution and shoreline development.

Combined, these threats impair the marine environment through various stress avenues, such as: increased sea surface and tidal inundation, altered circulation patterns and tidal mixing, pattern shifts in water temperature, ocean acidification,  reduced species diversity and abundance, increased pollutants and pathogens, altered sediment deposition, loss of aquatic plant coverage,  and  reduced presence of native marine species. Future work will include developing conservation strategies, in collaboration with department partners, to address these impacts and to conserve these vibrant ecoregions.  Examples of conservation strategies for the marine ecoregions include:

  • Improve coordination and communication with State, local, and Federal agencies on shoreline protections, stormwater runoff (including urban and agricultural inputs), and modifications to estuarine flow dynamics.
  • Implement State invasive species management plans, and develop streamlined processes to control and eradicate invasive species.
  • Increase education and outreach efforts with partners to improve public awareness about the impact of threats, such as stormwater runoff, pharmacological pollutants, pathogens, and invasive organisms, on marine ecosystems.
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