Terrestrial materials exported from coastal watersheds influence marine food-webs and carbon budgets across the globe, yet much is unknown about the fundamental processes of land-sea carbon cycling or system response to climate change. On an outer-coast island near the center of the Pacific Coastal Temperate Rainforest (PCTR) in North America, the Hakai Institute has developed a long-term coastal margin observatory to examine the flux of terrestrial materials from land to sea – the origins, pathways, processes and food web consequences – in the context of long-term environmental change.
Our study area is Kwakshua Channel and all the land that drains into the channel (approximately 7000 hectares) - a natural laboratory well suited to the study of terrestrial-marine coupling in the hypermaritime coast of western North America. The terrestrial environment is ecologically and physically diverse, varying from bogs and forested wetlands to productive riparian forests. Streams are characterized by high levels of terrestrial organic matter, with concentrations varying across time and space. Kwakshua channel itself is a well-defined and accessible marine waterbody in which to observe physical mixing, microbial processing, food web uptake and ecological interactions.
Beginning in 2013, we established an integrated and multi-disciplinary study across the land-sea gradient. We are using LiDAR and other remote sensing data to examine landscape controls on terrestrial ecosystems and watershed exports. Focusing in on the sources of dissolved organic matter on land, we established a network of terrestrial ecosystem plots across a landscape gradient. Plots are used to examine community composition, stand dynamics, and soil processes, with a subset of plots outfitted for remote monitoring of soil dynamics with sensors. At stream outlets, we use a year-round sampling program and sensor network to quantify, at high temporal resolution, the amount and character of terrestrial exports from seven focal watersheds. Nearshore oceanographic conditions and plankton communities are also monitored year round, adjacent to stream outlets and at other nearshore stations within and outside the channel. Similarly, we conduct year-round sampling of microbial communities - including bacteria and protists - across the terrestrial, freshwater and marine sites.
The Critical Zone - from bedrock to tree-top - indeed plays a critical role in controlling the export of organic materials from coastal watersheds. Consequently, we use the framework of a critical zone observatory to study the watersheds of Calvert Island.
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