Research Technical Report
A PDF version of this report is available here:
Monterey Bay National Marine Sanctuary: Davidson Seamount Management Zone Threats Assessment
MBNMS (June 2012)
MBNMS Technical Report 2012-1, 39pp.
Davidson Seamount is an undersea mountain off the Central California coast, with its crest (summit) approximately 1,250 m below the sea surface and its base in approximately 3,500 m of water. The Davidson Seamount Management Zone (DSMZ) of the Monterey Bay National Marine Sanctuary (MBNMS or Sanctuary) is a protected area bounded by a square approximately 30 nautical miles (nm) per side, centered on the crest of the Davidson Seamount. The zone's surface area is approximately 585 square nm, and the submerged lands there under are included within the DSMZ (NMSP 2008). This portion of the Sanctuary is located approximately 65 nm off the coast of San Simeon, San Luis Obispo County. The DSMZ is bounded by coordinates West: 123.0°W; East: 122.5°W; North: 35.9°N; South: 35.5°N (Fig. 1). The DSMZ possesses several special characteristics that make it a priority for resource protection. These characteristics include a relatively pristine, physically undisturbed seafloor, sizable microhabitats of large (some over eight feet tall) and old (some over 200 years) deep-sea corals and vast sponge fields, and relatively high numbers of rare and undescribed benthic species. As a result, Davidson Seamount has been called "An Oasis in the Deep." Though seamount habitats are relatively poorly understood, Davidson Seamount is one of the best studied (Clague et al., 2010).
Many of the biological communities of the DSMZ are particularly vulnerable to damage. The abundance of long-lived species within the management area, coupled with the dominance of large, fragile, slow-growing organisms, means that anthropogenic disturbances are likely to result in extremely long recovery times. Although many seamount communities exhibit endemism rates over 50%, researchers have found little evidence to support the seamount endemicity hypothesis at Davidson Seamount (Stone et al., 2004; McClain et al., 2008). Seventy-one percent of the species observed in the DSMZ are cosmopolitan (i.e., distributed on seamount and non-seamount habitats), 12% are potentially confined to seamounts and 7% are potentially confined to Davidson Seamount (McClain et al., 2008). If these percentages are assumed to represent the actual level of endemicity in the DSMZ, they still imply a substantial number of unique species. Particularly compelling is the difference in frequency of species observations between Davidson Seamount and the nearby deep-sea environment of Monterey Canyon. Only 70 nm apart, Monterey Canyon is a less optimal habitat, with species on Davidson Seamount exhibiting greater abundance and biomass (Fig. 2; Clague et al., 2010).
Of the estimated 33,452 isolated seamounts with elevations greater than 1,000 m in the world, only 350 have been sampled thus far, and Davidson is one of less than 100 that have been sampled in any detail (Yesson et al., 2011; CenSeam, 2011). Protection of the physical and biological resources at Davidson Seamount is thus even more important, as the local science community has demonstrated their ability to conduct extensive deep-sea research in the DSMZ. Increases to our understanding of Davidson Seamount have been, and will continue to be, significant to humanity's knowledge of seamount environments in general. The DSMZ possesses unique resources that could suffer irrecoverable losses if not guarded against direct and indirect human impacts. MBNMS management must anticipate all possible risks that may place the DSMZ under increased pressure, and strive to minimize those risks (NOAA, 2009b).
Activity 3.1 of the DSMZ Management Plan (version 5.0, July 2009) describes the importance of Continuously Characterizing the Potential Threats to Davidson Seamount. Specifically, Activity 3.1 states:
A threats and protection plan will be developed based on a thorough literature review, workshops with experts, and a socioeconomic and biological characterization.
This document begins to accomplish the objective in Activity 3.1 by first summarizing existing measures that have been taken to protect Davidson Seamount. It then describes many of the known existing and potential threats to the DSMZ. Our description of the pressures on the seamount is based on observations from expeditions to the DSMZ, knowledge of human activities in the surrounding areas, and documentation of human impacts to other seamount environments found in the literature. It should be noted that many of the threats listed below relate to phenomena of a global nature and will require regulation at larger geographical scales beyond the jurisdiction of Sanctuary management. However, compiling them here will allow managers within and beyond the MBNMS to anticipate and respond to these pressures.