NOAA Technical Memorandum
NMFS-AFSC-130
A comparison of the eastern and western Bering Sea shelf and slope ecosystems through the use of mass-balance food web models
Abstract
A comparison of the food webs of the eastern and western Bering Sea continental shelf large marine ecosystems (EBS and WBS LMEs) is presented, with a literature review of Russian and English sources for the western Bering Sea food web. A model is constructed using Ecopath, a tool for performing quantitative mass-balance calculations to synthesize food web data. The model focuses on the earliest period for which detailed diet data was available in both systems, 1980-85.
The results show that the broad EBS shelf supports a benthic community of considerable diversity, while the narrower WBS shelf contains an ecosystem with a higher per-unit-area production in the pelagic layers and a more productive pelagic phytoplankton and zooplankton community. Keystone species in both systems are walleye pollock (Theragra chalcogramma) and Pacific cod (Gadus macrocephalus). In the eastern Bering Sea, small flatfish and crab species have a large impact on the energy flow from the benthic web to upper trophic levels. On the other hand, in the WBS, a large proportion of detritus entering the benthic food web is consumed by epifaunal species such as urchins and brittlestars. This may be due to the larger percentage of WBS shelf area close to shore. Additional measures of ecosystem structure, maturity, and sensitivity are presented.
Future steps in pursuing ecosystem modeling efforts through the food webs in these two systems should lie in determining the importance and role of deep Bering Sea Basin processes, especially through mesopelagic forage fish, and in further subpartitioning each model into fine scale biophysical domains.
View Online (pdf, 4.25MB).
|
