What’s New in Our Harbors?
Invasive species have received an increasing amount of attention in the last decade, and with good reason. The spread of species beyond their native range has the potential to produce severe, often irreversible impacts on agricultural, recreational, and natural resources. The term “invasive species” was formally defined by Executive Order 13112 in 1999 and refers to a species that 1) is non-native (or alien) to the ecosystem under consideration and 2) whose introduction causes or is likely to cause economic or environmental harm or harm to human health. Except for habitat destruction, invasive species are the biggest threat to native biodiversity and have contributed to the decline of 42 percent of U.S. endangered and threatened species. A recent estimate of the total cost of invasive species in the United States is more than $100
billion each year. In addition to these direct economic impacts
are the ecological effects, many of which remain unknown.
|The sea slug Hermissenda crassicornis (and its white, coiled egg cases) and a variety
of hydroids, tunicates, and other encrusting invertebrates are typical of the fouling
communities found on the sides of floating docks. photo 2003 Steve Lonhart
The Monterey Bay National Marine Sanctuary covers hundreds of miles of coastline and encompasses a diverse array of marine habitats, ranging from the high intertidal zone to the depths of Monterey Canyon. However, not all of these habitats are equally susceptible to invasive species. It is well established that the spread of many invasive species is intimately linked with human activities (e.g., shipping), so it comes as no surprise that areas of high human activity receive the bulk of invasive species introductions. In particular, harbors and ports are “hot spots” for species invasion, due to their high levels of vessel traffic. Many species become attached
to vessel hulls or are taken up in ballast water as larvae, then are displaced hundreds of miles to a new environment where they
may become established.
In December 2002 the California Department of Fish and Game’s (CDFG) Office of Oil Spill Prevention and Response
prepared and submitted a report entitled A Survey of Non-Indigenous Aquatic Species in the Coastal and Estuarine Waters
of California to the California state legislature as required by the Ballast Water Management Act of 1999. CDFG conducted the study to “determine the location and geographic range of non-indigenous species populations along the California coast.” Such data are lacking for many areas, and this report now serves as a baseline to determine both the nature and extent of biological
invasions and to evaluate the effectiveness of potential methods
to prevent the establishment and control the spread of invasive species in California coastal waters.
The study indicated that all areas investigated, covering coastal California from Humboldt Bay to San Diego, have experienced some level of biological invasion. Researchers focused on seven major harbors and ports (e.g., San Francisco Bay, Los Angeles, and Long Beach Harbors), but also included minor ports, bays, and estuaries. Not surprisingly, the most invaded areas were major
commercial ports. The report also noted that smaller ports (e.g., Monterey and Santa Cruz Harbors) also had significant numbers of non-indigenous species. In total, the survey reported 747 organisms that were “introduced or most likely introduced.” Taxonomic experts felt confident that 360 of the 747 species were invasive.
For the 387 remaining species, it was difficult to determine if they were native to California; some were introduced prior to extensive biological inventories and research in the 1900s, so their origins and native status remain a mystery. In addition, 126 of the organisms could not be identified to species, a common problem for many of the small, encrusting invertebrates.
In Monterey Harbor, CDFG divers collected 72 organisms from invertebrate communities found both above and within the seafloor bottom. Of these, 12 were nonindigenous, 25 native, 9 cryptogenic (i.e., it is not known if they are native or nonindigenous), and 26 could not be identified to species.
One species readily recognized as an invader is the seaweed Undaria pinnatifida. Native to Asia and commonly known as wakame, Undaria was first detected in southern California in the spring of 2000. Unlike native annuals that first appear in the spring and become reproductive in the summer, Undaria first appears in winter and becomes reproductive within two months. It is unclear how Undaria will impact California natives, but in other parts of the world it is seasonally very dense and may displace native species.
Based on the results of the report, CDFG made several recommendations, including: 1) ongoing surveys for nonindigenous aquatic species; 2) research on the pathways of introduction; and 3) more refined taxonomy to identify species conclusively. CDFG and the sanctuary are already working together to address these issues.
Monterey Bay National Marine Sanctuary and
Sanctuary Integrated Monitoring Network (SIMoN)