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Tidal Channel Diatom Assemblages Reflect within Wetland Environmental Conditions and Land Use at Multiple Scales
Citation:
Weilhoefer, C., Walt Nelson, AND Pat Clinton. Tidal Channel Diatom Assemblages Reflect within Wetland Environmental Conditions and Land Use at Multiple Scales. Estuaries and Coasts. Estuarine Research Federation, Port Republic, MD, 38:534-545, (2015).
Impact/Purpose:
The tidal creek benthic diatom assemblage appears sensitive to variation in both wetland and landscape level factors, which suggests that it may be a useful bioindicator of human disturbance to tidal wetland ecosystems. Regional patterns of this benthic diatom community in marshes within Oregon estuaries were characterized. The relative importance of local wetland and surrounding landscape level stressors in structuring this assemblage were measured at 100m, 250m, 1000m, and watershed scales. The tidal channel benthic diatom community was most strongly correlated with variables related to human disturbance surrounding the wetland at all scales, and not with salinity or any tidal channel water quality parameter. Extent of developed and impervious surface land covers within the 100m and 250m buffers were more strongly correlated with the diatom assemblage than at larger spatial scales. Species richness and Shannon diversity index were both negatively correlated with the amount of wetland and mudflat surrounding the study sites. Of secondary importance in structuring the diatom assemblage were sediment nitrogen and phosphorus concentrations in wetlands immediately surrounding the tidal channels.
Description:
We characterized regional patterns of the tidal channel benthic diatom community and examined the relative importance of local wetland and surrounding landscape level factors measured at multiple scales in structuring this assemblage. Surrounding land cover was characterized at the 100m, 250m, 1000m, and watershed buffer scales. Tidal channel benthic diatom communities were characterized by high species richness, abundance of rare species, and an abundance of species characterized as meso-eutraphentic and eutraphentic. The number of species per site ranged between 21 and 60 (mean ± standard deviation: 43.5 ± 9.4). Abundant and frequently occurring taxa included Planothidium delicatulum, Navicula gregaria, and Amphora coffeaeformis. The tidal channel benthic diatom community was most strongly correlated with variables related to human disturbance at all scales surrounding the wetland and not with any tidal channel water quality parameter, including salinity. Furthermore, developed and impervious surface land covers within the 100m and 250m buffers were more strongly correlated with the diatom assemblage than these covers at larger spatial scales. Species richness and Shannon diversity index were both negatively correlated with the amount of wetland and mudflat surrounding the sites. Of secondary importance in structuring the diatom assemblage were sediment nitrogen and phosphorus concentrations in wetlands immediately surrounding the tidal channels. The sensitivity of the tidal creek benthic diatom assemblage to both wetland and landscape level factors indicates that it might be a useful bioindicator of human disturbance to tidal wetland ecosystems.