Tidal exchange, bivalve grazing, and patterns of primary production in Willapa Bay, Washington, USA

N. S. Banas, B. M. Hickey, J. A. Newton, J. L. Ruesink

Research output: Contribution to journalArticle

53 Citations (Scopus)

Abstract

Willapa Bay, Washington, USA, is a shallow, coastal-plain, upwelling-influenced estuary where Pacific oysters Crassostrea gigas are intensively cultivated. CTD transect data show that in the long-term average over the May to September growing season, Willapa Bay is a sink for oceanic phytoplankton, not a net exporter: as the tidal circulation stirs ocean water into the estuary, chlorophyll concentration declines by 30 to 60% relative to a hypothetical dilution of the ocean end-member. A 3D circulation model (General Estuarine Transport Model, GETM) was modified to include a phytoplankton-like tracer subject to variable intertidal benthic grazing rates. The grazing rate that best reproduces the along-estuary phytoplankton biomass profile agrees, within confidence limits, with an estimate of cultivated-oyster filtration from literature values. Oysters and other intertidal benthic grazers may thus be the primary cause of the net loss of phytoplankton within the estuary in summer. These grazers appear to be within a small factor of their carrying capacity: as bay-total filtration capacity is increased in the model, the chlorophyll intrusion shortens and food intake per individual grazer declines. Nevertheless, only 8 to 15% of the net tidal supply of oceanic phytoplankton is consumed within the estuary. Even in this well-flushed system, the small-scale structure of tidal transport - rather than total oceanic supply - controls overall food availability for the benthos.

LanguageEnglish
Pages123-139
Number of pages17
JournalMarine Ecology Progress Series
Volume341
DOIs
Publication statusPublished - 4 Jul 2007

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primary production
bivalve
primary productivity
Bivalvia
estuaries
grazing
phytoplankton
estuary
Crassostrea gigas
oysters
chlorophyll
General Circulation Models
food intake
coastal plains
carrying capacity
benthic organisms
food availability
coastal plain
benthos
general circulation model

Keywords

  • biophysical interactions
  • bivalves
  • estuaries
  • primary production
  • tidal circulation
  • Willapa Bay

Cite this

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title = "Tidal exchange, bivalve grazing, and patterns of primary production in Willapa Bay, Washington, USA",
abstract = "Willapa Bay, Washington, USA, is a shallow, coastal-plain, upwelling-influenced estuary where Pacific oysters Crassostrea gigas are intensively cultivated. CTD transect data show that in the long-term average over the May to September growing season, Willapa Bay is a sink for oceanic phytoplankton, not a net exporter: as the tidal circulation stirs ocean water into the estuary, chlorophyll concentration declines by 30 to 60{\%} relative to a hypothetical dilution of the ocean end-member. A 3D circulation model (General Estuarine Transport Model, GETM) was modified to include a phytoplankton-like tracer subject to variable intertidal benthic grazing rates. The grazing rate that best reproduces the along-estuary phytoplankton biomass profile agrees, within confidence limits, with an estimate of cultivated-oyster filtration from literature values. Oysters and other intertidal benthic grazers may thus be the primary cause of the net loss of phytoplankton within the estuary in summer. These grazers appear to be within a small factor of their carrying capacity: as bay-total filtration capacity is increased in the model, the chlorophyll intrusion shortens and food intake per individual grazer declines. Nevertheless, only 8 to 15{\%} of the net tidal supply of oceanic phytoplankton is consumed within the estuary. Even in this well-flushed system, the small-scale structure of tidal transport - rather than total oceanic supply - controls overall food availability for the benthos.",
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Tidal exchange, bivalve grazing, and patterns of primary production in Willapa Bay, Washington, USA. / Banas, N. S.; Hickey, B. M.; Newton, J. A.; Ruesink, J. L.

In: Marine Ecology Progress Series , Vol. 341, 04.07.2007, p. 123-139.

Research output: Contribution to journalArticle

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AB - Willapa Bay, Washington, USA, is a shallow, coastal-plain, upwelling-influenced estuary where Pacific oysters Crassostrea gigas are intensively cultivated. CTD transect data show that in the long-term average over the May to September growing season, Willapa Bay is a sink for oceanic phytoplankton, not a net exporter: as the tidal circulation stirs ocean water into the estuary, chlorophyll concentration declines by 30 to 60% relative to a hypothetical dilution of the ocean end-member. A 3D circulation model (General Estuarine Transport Model, GETM) was modified to include a phytoplankton-like tracer subject to variable intertidal benthic grazing rates. The grazing rate that best reproduces the along-estuary phytoplankton biomass profile agrees, within confidence limits, with an estimate of cultivated-oyster filtration from literature values. Oysters and other intertidal benthic grazers may thus be the primary cause of the net loss of phytoplankton within the estuary in summer. These grazers appear to be within a small factor of their carrying capacity: as bay-total filtration capacity is increased in the model, the chlorophyll intrusion shortens and food intake per individual grazer declines. Nevertheless, only 8 to 15% of the net tidal supply of oceanic phytoplankton is consumed within the estuary. Even in this well-flushed system, the small-scale structure of tidal transport - rather than total oceanic supply - controls overall food availability for the benthos.

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