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

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

U-Pb (zircon) geochronologic analyses for rocks of the Transantarctic Mountains (Table 4.3-1)

The Byrd Glacier discontinuity us a major boundary crossing the Ross Orogen, with crystalline rocks to the north and primarily sedimentary rocks to the south. Most models for the tectonic development of the Ross Orogen in the central Transantarctic Mountains consits of two-dimensional transects across the belt, but do not adress the major longitudinal contrast at Byrd Glacier. This paper presents a tectonic model centering on the Byrd Glacier discontinuity. Rifting in the Neoproterozoic producede a crustal promontory in the craton margin to the north of Byrd Glacier. Oblique convergence of the terrane (Beardmore microcontinent) during the latest Neroproterozoic and Early Cambrian was accompanied by subduction along the craton margin of East Antarctica. New data presented herein in the support of this hypothesis are U-Pb dates of 545.7 ± 6.8 Ma and 531.0 ± 7.5 Ma on plutonic rocks from the Britannia Range, subduction stepped out, and Byrd Glacier. After docking of the terrane, subduction stepped out, and Byrd Group was deposited during the Atdabanian-Botomian across the inner margin of the terrane. Beginning in the upper Botomian, reactivation of the sutured boundaries of the terrane resulted in an outpouring of clastic sediment and folding and faulting of the Byrd Group

Natural Regeneration of Estuarine Biofilm in the Fraser River Estuary, Vancouver, British Columbia

High densities of biofilm occur in the top 2 mm of soft fine sediments within the upper intertidal zone of estuaries. As such, biofilm is subjected to periodic physical disturbance from natural processes and is increasingly exposed to anthropogenic disturbance from shoreline use and coastal development. The natural regeneration of biofilm in the Fraser River Estuary was assessed at Roberts Bank through paired control-impact study plots. Biofilm biomass, as measured by photopigment and carbohydrate densities, was sampled immediately prior to, post, and every three to five days following a manual disturbance over a 45 day period. Biofilm biomass at the disturbance sites was significantly lower compared with control plots for biofilm biomass parameters (chlorophyll a, fucoxanthin, and total carbohydrate) immediately following disturbance. Pairwise tests showed the biofilm biomass parameters at the disturbance sites returned to statistically similar levels as the control sites within nine days of disturbance. These results indicate biofilm to be resilient to disturbance with an ability to readily establish if optimal growth conditions occur. A larger temporal pattern was observed within the biofilm biomass levels and the microphytobenthic community composition across all sites. Control sites did not return to pre-disturbance conditions until 28 to 32 days following disturbance. The occurrence of a 28 day pattern with peak biomass densities occurring during monthly maximum spring tides and low biomass occurring during neap tides suggests the influence of the spring-neap tidal cycle, which is known to drive estuarine mixing dynamics. Biofilm is shown to exhibit a naturally high level of variability, which should be considered during ecological assessments