Dissolved Organic Carbon

The Pacific coastal temperate rainforest is characterized by many small watersheds and a coastline that features numerous fjords. Ultimately, freshwater runoff reaches the marine environment. On route to the ocean, each stream collects and carries terrestrial material that is unique to its watershed. We are currently examining relationships between watershed characteristics and use, freshwater flow and terrestrial carbon export.

Aquatic carbon may exist in particulate or dissolved form, as either inorganic or organic carbon. Inorganic carbon includes any species of carbonate (e.g. calcium carbonate, carbon dioxide, bicarbonate), and plays a crucial role in the buffering capacity of natural waters. Dissolved organic carbon (DOC) is a complex mixture of molecular species that vary in composition and origin. DOC contributes to the base of aquatic food webs and often adds colour to surface waters, making the water appear brown and sometimes frothy. Carbon dynamics are important in both terrestrial and marine ecosystems, and the carbon cycle is fundamental to life on earth. The hydrologic cycle plays a critical role in carbon cycling, especially in linking the land to sea.

In collaboration with the Coastal Rainforest Margins Research Network and the Hakai Institute, we are sampling rivers on Vancouver Island and around the central and south coast of BC to quantify dissolved organic carbon. DOC concentrations can be combined with river discharge values to indicate flux and yield of terrestrial DOC moving into the ocean. Studies in the 7 focal watersheds at the Hakai institute showed that this rain-dominated region of Pacific coastal temperate rainforest have some the highest land-to-sea DOC yields in the world! High DOC yields from these small watersheds on the outer Pacific coast indicates that the coastal margin plays an important role in global carbon processes, and the link between ocean and land. Empirical data about DOC composition and flux in small watersheds along the Pacific coast are scarce. We are expanding stream monitoring and analysis of DOC to fill in some of the information gaps about land-to sea DOC flux in small catchments.

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This map shows the locations of streams that are included in our DOC synoptic sampling program.



(link) Oliver, A. A., Tank, S. E., Giesbrecht, I., Korver, M. C., Floyd, W. C., Sanborn, P., Bulmer, C., and Lertzman, K. P.: A global hotspot for dissolved organic carbon in hypermaritime watersheds of coastal British Columbia, Biogeosciences, 14, 3743-3762, https://doi.org/10.5194/bg-14-3743-2017, 2017.