Multi-day water residence time as a mechanism for physical and biological gradients across intertidal flats

Elizabeth E. Wheat, Neil S. Banas, Jennifer L. Ruesink

Research output: Contribution to journalArticle

Abstract

Tidal flats with shallow-sloping bathymetry under meso-to macrotidal conditions allow organisms to occupy similar tidal elevations at different distances from subtidal channels. As water floods or ebbs across such tidal flats during a single tidal cycle, upstream organisms may modify water properties such as chlorophyll concentration, while physiochemical properties may change due to close association with sediments. Here we report evidence for an additional mechanism establishing cross-shore gradients: multi-day water residence times, in the sense that even if water completely drains into subtidal channels at low tide, a large fraction returns to the flats on the next high tide. We applied circulation modeling and empirical measurements of water properties and benthic secondary production to a 1-km-wide tidal flat in Willapa Bay, Washington, USA. From the circulation model, water parcels on this intertidal flat have residence times up to 2 d, that is, water found on the flat at one high tide returns to the intertidal zone for a median of 4 successive semidiurnal high tides. Modeled residence times generally increased towards shore. Four empirical datasets showed cross-shore gradients consistent with modeled residence times: Salinity time series lagged towards shore; water column chlorophyll declined towards shore at fixed stations (near-bottom) and in surface transects more than could be explained by benthic suspension-feeding during a single transit of water; and oyster (Magallana = Crassostrea gigas) condition declined 25% over 0.5 km from channel to shore, independent of tidal elevation. One environmental measurement was more consistent with within-tide change, as water temperatures warmed towards shore on afternoon flood tides but showed no tidal-cycle lags. Taken together, these patterns suggest that multi-day water residence times can contribute to environmental heterogeneity from channel to shore on tidal flats, acting orthogonally to well-recognized estuarine gradients in residence time from ocean to river.

LanguageEnglish
Article number106303
JournalEstuarine, Coastal and Shelf Science
Early online date26 Jul 2019
DOIs
Publication statusE-pub ahead of print - 26 Jul 2019

Fingerprint

residence time
tides
tide
tidal flat
water
tidal cycle
chlorophyll
circulation modeling
secondary production
littoral zone
Crassostrea gigas
organisms
drainage water
intertidal environment
bathymetry
oysters
drain
time series analysis
water temperature
transect

Keywords

  • benthic suspension feeders
  • circulation model
  • crassostrea gigas
  • intertidal gradients
  • residence time
  • water column chlorophyll

Cite this

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title = "Multi-day water residence time as a mechanism for physical and biological gradients across intertidal flats",
abstract = "Tidal flats with shallow-sloping bathymetry under meso-to macrotidal conditions allow organisms to occupy similar tidal elevations at different distances from subtidal channels. As water floods or ebbs across such tidal flats during a single tidal cycle, upstream organisms may modify water properties such as chlorophyll concentration, while physiochemical properties may change due to close association with sediments. Here we report evidence for an additional mechanism establishing cross-shore gradients: multi-day water residence times, in the sense that even if water completely drains into subtidal channels at low tide, a large fraction returns to the flats on the next high tide. We applied circulation modeling and empirical measurements of water properties and benthic secondary production to a 1-km-wide tidal flat in Willapa Bay, Washington, USA. From the circulation model, water parcels on this intertidal flat have residence times up to 2 d, that is, water found on the flat at one high tide returns to the intertidal zone for a median of 4 successive semidiurnal high tides. Modeled residence times generally increased towards shore. Four empirical datasets showed cross-shore gradients consistent with modeled residence times: Salinity time series lagged towards shore; water column chlorophyll declined towards shore at fixed stations (near-bottom) and in surface transects more than could be explained by benthic suspension-feeding during a single transit of water; and oyster (Magallana = Crassostrea gigas) condition declined 25{\%} over 0.5 km from channel to shore, independent of tidal elevation. One environmental measurement was more consistent with within-tide change, as water temperatures warmed towards shore on afternoon flood tides but showed no tidal-cycle lags. Taken together, these patterns suggest that multi-day water residence times can contribute to environmental heterogeneity from channel to shore on tidal flats, acting orthogonally to well-recognized estuarine gradients in residence time from ocean to river.",
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Multi-day water residence time as a mechanism for physical and biological gradients across intertidal flats. / Wheat, Elizabeth E.; Banas, Neil S.; Ruesink, Jennifer L.

In: Estuarine, Coastal and Shelf Science, 26.07.2019.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Multi-day water residence time as a mechanism for physical and biological gradients across intertidal flats

AU - Wheat, Elizabeth E.

AU - Banas, Neil S.

AU - Ruesink, Jennifer L.

PY - 2019/7/26

Y1 - 2019/7/26

N2 - Tidal flats with shallow-sloping bathymetry under meso-to macrotidal conditions allow organisms to occupy similar tidal elevations at different distances from subtidal channels. As water floods or ebbs across such tidal flats during a single tidal cycle, upstream organisms may modify water properties such as chlorophyll concentration, while physiochemical properties may change due to close association with sediments. Here we report evidence for an additional mechanism establishing cross-shore gradients: multi-day water residence times, in the sense that even if water completely drains into subtidal channels at low tide, a large fraction returns to the flats on the next high tide. We applied circulation modeling and empirical measurements of water properties and benthic secondary production to a 1-km-wide tidal flat in Willapa Bay, Washington, USA. From the circulation model, water parcels on this intertidal flat have residence times up to 2 d, that is, water found on the flat at one high tide returns to the intertidal zone for a median of 4 successive semidiurnal high tides. Modeled residence times generally increased towards shore. Four empirical datasets showed cross-shore gradients consistent with modeled residence times: Salinity time series lagged towards shore; water column chlorophyll declined towards shore at fixed stations (near-bottom) and in surface transects more than could be explained by benthic suspension-feeding during a single transit of water; and oyster (Magallana = Crassostrea gigas) condition declined 25% over 0.5 km from channel to shore, independent of tidal elevation. One environmental measurement was more consistent with within-tide change, as water temperatures warmed towards shore on afternoon flood tides but showed no tidal-cycle lags. Taken together, these patterns suggest that multi-day water residence times can contribute to environmental heterogeneity from channel to shore on tidal flats, acting orthogonally to well-recognized estuarine gradients in residence time from ocean to river.

AB - Tidal flats with shallow-sloping bathymetry under meso-to macrotidal conditions allow organisms to occupy similar tidal elevations at different distances from subtidal channels. As water floods or ebbs across such tidal flats during a single tidal cycle, upstream organisms may modify water properties such as chlorophyll concentration, while physiochemical properties may change due to close association with sediments. Here we report evidence for an additional mechanism establishing cross-shore gradients: multi-day water residence times, in the sense that even if water completely drains into subtidal channels at low tide, a large fraction returns to the flats on the next high tide. We applied circulation modeling and empirical measurements of water properties and benthic secondary production to a 1-km-wide tidal flat in Willapa Bay, Washington, USA. From the circulation model, water parcels on this intertidal flat have residence times up to 2 d, that is, water found on the flat at one high tide returns to the intertidal zone for a median of 4 successive semidiurnal high tides. Modeled residence times generally increased towards shore. Four empirical datasets showed cross-shore gradients consistent with modeled residence times: Salinity time series lagged towards shore; water column chlorophyll declined towards shore at fixed stations (near-bottom) and in surface transects more than could be explained by benthic suspension-feeding during a single transit of water; and oyster (Magallana = Crassostrea gigas) condition declined 25% over 0.5 km from channel to shore, independent of tidal elevation. One environmental measurement was more consistent with within-tide change, as water temperatures warmed towards shore on afternoon flood tides but showed no tidal-cycle lags. Taken together, these patterns suggest that multi-day water residence times can contribute to environmental heterogeneity from channel to shore on tidal flats, acting orthogonally to well-recognized estuarine gradients in residence time from ocean to river.

KW - benthic suspension feeders

KW - circulation model

KW - crassostrea gigas

KW - intertidal gradients

KW - residence time

KW - water column chlorophyll

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DO - 10.1016/j.ecss.2019.106303

M3 - Article

JO - Estuarine, Coastal and Shelf Science

T2 - Estuarine, Coastal and Shelf Science

JF - Estuarine, Coastal and Shelf Science

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ER -