• wetlands and the coastal flood zone (NRC, 2012); geographic ranges of warm water marine species are already extending poleward (e.g., Sorte et al., 2010; Doney et al., 2012), a trend that could exacerbate problems associated with invasive non-indigenous species, including increasing the potential for establishment of reproductive populations of the nonnative Pacific oyster in Drakes Estero.

The committee found that many of the impact assessments for the resource categories were limited by a lack of scientific information, resulting in moderate to high uncertainty in the conclusions. Although the feasibility of gathering new data within the given time constraints may be limited, the committee identified the following approaches for reducing scientific uncertainty in the DEIS:

  • To the extent feasible, monitor how frequently boats are used for both bag and rack culture relative to stage of tide, motor boat routes relative to the distribution of seagrass beds and harbor seal protected areas, and more details on how the balance between bag culture and rack culture has changed from year to year and may change in the future (acreage used, location and production).
  • Document the air and underwater soundscape, including evaluation of both natural and anthropogenic noise sources.
  • Apply scientific methods to the assessment of socioeconomic impacts. Consider the use of qualitative modeling techniques to integrate across environmental, fishery, and socio-economic information.
  • Assess the abundance and distribution of native and non-indigenous benthic invertebrates (infauna, epifauna, sessile and mobile species on hard, soft, and biological surfaces).
  • Develop more accurate estimates of the seasonal flushing rate in the culture areas and use those for developing simple models of the contribution of cultured shellfish to water quality and food resource competition.
  • Conduct a rigorous and comprehensive analysis of aerial photographs to resolve uncertainty in issues such as eelgrass extent and change, bag and rack culture area, and propeller scarring and other disturbance effects on eelgrass.
  • Measure temporal (day/night) and spatial variability (distance from sources) within Drakes Estero using unweighted measures of ambient and source sound levels.

In Drakes Estero, as in many highly valued coastal areas, sustained monitoring of key variables (e.g., water quality parameters such as current velocities, temperature, salinity, dissolved nutrients, phytoplankton biomass, suspended organic matter, attenuation of downwelling radiation, and turbidity; abundance and distributions of benthic fauna, fish, birds, harbor seals, and non-indigenous species; extent and condition of eelgrass beds and tidal marshes) would reduce the uncertainty of impact assessments. These types of monitoring programs have been established through programs such as the National Estuarine Research Reserve System and the Integrated Ocean Observing System. Monitoring data on some of these key variables would inform adaptive, ecosystem-based management of the impacts of human uses on soundscapes, water quality, benthic habitats, biodiversity, and living resources in Drakes Estero.



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