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Effects of light reduction on food webs and associated ecosystem services of Yaquina Bay
Citation:
DEWITT, T. H., S. R. Pacella, AND P. M. ELDRIDGE. Effects of light reduction on food webs and associated ecosystem services of Yaquina Bay. Presented at Pacific Estuarine Research Society Meeting, Astoria, OR, March 03 - 05, 2011.
Impact/Purpose:
Reduced water clarity can affect estuarine primary production but little is known of its subsequent effects to consumer guilds or ecosystem services.
Description:
Reduced water clarity can affect estuarine primary production but little is known of its subsequent effects to consumer guilds or ecosystem services. We investigated those effects using inverse analysis of modeled food webs of the lower (polyhaline) and upper (mesohaline) reaches of Yaquina Bay, upon which we imposed a scenario of reduced water clarity equivalent to proposed estuarine water quality thresholds. Food web models were parameterized using floral and faunal biomass and production values obtained from our sampling or the literature. The effects of reduced water clarity were propagated using light-productivity sub-models for phytoplankton, benthic micro- and macroalgae, and seagrasses, and by reducing the area of eelgrass habitat due to changes in its depth distribution. Abundance of fauna from eelgrass habitats was correspondingly reduced also. This simulation indicated that NPP could decrease 5% in the lower estuary and 12% in the upper, eelgrass habitat could decline by 50% in the upper estuary, but upper estuary faunal biomass would decline only 1% because seagrass habitat area was initially small. Our food web modeling suggests that under the low-light scenario, benthic infaunal production would decline in both reaches, nekton guilds would not change, and that bird abundance would decline in the upper estuary. Total carbon throughput and net ecosystem metabolism would decrease only slightly in both reaches. However, carbon burial would be reduced 17-88% in the lower and upper reaches. Thus, if water clarity was reduced below proposed thresholds, the ecosystem services of fisheries production may be little affected, but carbon sequestration and opportunities to view wildlife (birds) could decline, particularly in the upper reaches of the estuary.