However, despite the diversity of potential terrestrial OC sources (e.g., rainfall, snow, and glacial melt) to nearshore waters of the northeast Pacific (Fellman et al. In the northwestern Atlantic, for example, it is estimated that more than half (59% ± 12%) of all carbon inputs to coastal waters originate from rivers and streams that drain the adjacent landmasses (Najjar et al. This transitional zone is now recognized as the Riverine Coastal Domain, a potentially important hotspot between land and sea for the processing of terrestrial materials (Carmack et al. 2013).Ĭoastal waters around northern North America are characterized by large freshwater inputs from the adjacent landmasses. Both the terrestrial DOC and POC fluxes to and the composition of DOC and POC within coastal waters are therefore expected to vary seasonally and spatially with changing terrestrial, freshwater, and marine processes and contributions (Bauer et al. Terrestrial OC mixes with both autochthonous OC produced within estuaries, coastal waters and the open ocean, or upwelled from deep waters (Hill and Wheeler 2002), and allochthonous groundwater inputs and lateral fluxes from adjacent marginal systems (e.g., salt marshes, mangrove forests, and coastal wetlands Clark et al. 2002), or altered during mixing (Asmala et al. 2016), or be lost to the atmosphere following remineralization (Abril et al. Within coastal waters, these exports of terrestrial organic matter can be taken up into food webs, thus directly subsidizing biological production (Harding and Reynolds 2014 Hitchcock et al. Dissolved organic carbon (DOC) accounts for between 40% and 60% of this flux, with the remainder exported as particulate organic carbon (POC) (Cauwet 2002 Dai et al. ![]() Rivers and streams globally export approximately 0.45 Pg C of terrestrially derived organic carbon (OC) to the coastal ocean every year (Bauer et al. ![]() Terrestrial exports of dissolved and particulate organic carbon affect nearshore ecosystems of the Pacific coastal temperate rainforest Our results highlight the importance of storms for connecting the coastal temperate rainforest with surface coastal waters, especially during the summer when connectivity between the freshwater and marine ecosystems is otherwise low. On an annual basis, primary production in marine waters (21–42 Gg C) exceeded total freshwater OC contributions (1.8–2.2 Gg C) however, freshwater exports were more important during the autumn and winter months, when rainfall was highest and primary production was limited by shorter days and deep turbulent mixing. Rainfall events facilitated the rapid export of terrestrial DOC and POC to coastal waters, altering water quality and potentially subsidizing microbial productivity across marine surface waters. ![]() δ 13C-DOC and -POC in freshwaters were constant, but varied seasonally at the marine stations with freshwater and marine processes. Freshwater DOC concentrations (9.97 ± 0.25 mg L −1) far exceeded those in marine waters (1.24 ± 0.03 mg L −1), while POC concentrations were similar across all sites (0.23 ± 0.01 mg L −1). ![]() We conducted monthly and targeted rainfall event surveys of dissolved and particulate organic carbon (DOC and POC) quantity and quality (δ 13C, dissolved organic matter characterization) across a freshwater to marine salinity gradient between Calvert and Hecate Islands, British Columbia, Canada. While it has been suggested that terrestrially derived organic matter could subsidize marine food webs and affect ocean biogeochemistry along the coastal margin, little work has been done to quantify and characterize OC across the freshwater to marine continuum. Watersheds of the coastal temperate rainforests of Pacific North America export large amounts of organic carbon (OC) to the coastal ocean.
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