Type of Presentation

Oral

Session Title

General Habitat Topics

Description

Biofilm is recognized as ecologically important habitat in the Fraser River Estuary due to its foraging value for migratory shorebirds. Areas of biofilm have been noted at Roberts Bank, where biofilm occurs across 120 ha in the upper intertidal zone. In 2013, hyperspectral remote sensing techniques were used to map biofilm across Roberts Bank, identifying a total area of 325 ha, including 160 ha of previously unknown biofilm in close proximity to the Fraser River. Groundtruthing data conducted during the mapping indicated a high confidence in delineating biofilm-dominated sediments. The application of a chlorophyll a algorithm identified the highest densities in sheltered habitat in the upper intertidal zone with lower densities occurring in exposed habitat.

Sediments within the identified biofilm areas were sampled for microphytobenthic composition and biomass over three seasons; spring, summer, and winter. The overall microphytobenthic community was dominated by Nitzschia spp. (33%), Navicula spp. (21%) and Achnanthidium spp. (20%). Spatially, biofilm in close proximity to the Fraser River possessed a lower abundance of marine-influenced genera as well as lower biomass, as measured by photopigment and carbohydrate densities. Seasonally, microphytobenthic composition changed towards a more diverse community from spring, through to summer and winter. However, peak biomass levels occurred in the spring and summer compared to the winter.

Assessment of physical and chemical data collected from the same sampling locations indicated a positive relationship between biofilm biomass and salinity, while a negative relationship was observed with coarse sediment grain size. This study provides the first detailed mapping and biological description of biofilm across Roberts Bank and highlights the influence of freshwater flows to the distribution, composition, and biomass of estuarine biofilms.

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Distribution and Species Composition of Biofilm in the Fraser River Estuary, Vancouver, British Columbia

2016SSEC

Biofilm is recognized as ecologically important habitat in the Fraser River Estuary due to its foraging value for migratory shorebirds. Areas of biofilm have been noted at Roberts Bank, where biofilm occurs across 120 ha in the upper intertidal zone. In 2013, hyperspectral remote sensing techniques were used to map biofilm across Roberts Bank, identifying a total area of 325 ha, including 160 ha of previously unknown biofilm in close proximity to the Fraser River. Groundtruthing data conducted during the mapping indicated a high confidence in delineating biofilm-dominated sediments. The application of a chlorophyll a algorithm identified the highest densities in sheltered habitat in the upper intertidal zone with lower densities occurring in exposed habitat.

Sediments within the identified biofilm areas were sampled for microphytobenthic composition and biomass over three seasons; spring, summer, and winter. The overall microphytobenthic community was dominated by Nitzschia spp. (33%), Navicula spp. (21%) and Achnanthidium spp. (20%). Spatially, biofilm in close proximity to the Fraser River possessed a lower abundance of marine-influenced genera as well as lower biomass, as measured by photopigment and carbohydrate densities. Seasonally, microphytobenthic composition changed towards a more diverse community from spring, through to summer and winter. However, peak biomass levels occurred in the spring and summer compared to the winter.

Assessment of physical and chemical data collected from the same sampling locations indicated a positive relationship between biofilm biomass and salinity, while a negative relationship was observed with coarse sediment grain size. This study provides the first detailed mapping and biological description of biofilm across Roberts Bank and highlights the influence of freshwater flows to the distribution, composition, and biomass of estuarine biofilms.