Transport of nutrients and carbon from the Nanaimo River to its estuary 1

Abstract

Over an annual cycle, concentrations of inorganic nitrogen, phosphorus, and organic carbon were measured slightly upstream from the confluence of the Nanaimo River, British Columbia, and its estuary. Inorganic nitrogen and phosphorus concentrations in river water are low most of the year and may not be important in supplying these nutrients to the estuarine mudflat. Large amounts of dissolved organic carbon (DOC) and fine particulate organic carbon (FPOC) are exported from the river to the mudflat (about 2,000 and 56 g C·m−2·yr−1), but the actual amount retained and utilized by the mudflat community is not known. Comparison with in situ primary production on the mudflat shows that fluvial DOC may be the greatest source of carbon to the system. A conceptual hypothesis is presented relating basin morphometry and retention structures to estuarine efficiency in retaining nutrient and carbon inputs.