Climate-Mediated Changes to Linked Terrestrial and Marine Ecosystems across the Northeast Pacific Coastal Temperate Rainforest Margin

Abstract

Coastal margins are important areas of materials flux that link terrestrial and marine ecosystems. Consequently, climate-mediated changes to coastal terrestrial ecosystems and hydrologic regimes have high potential to influence nearshore ocean chemistry and food web dynamics. Research from tightly coupled, high-flux coastal ecosystems can advance understanding of terrestrial–marine links and climate sensitivities more generally. In the present article, we use the northeast Pacific coastal temperate rainforest as a model system to evaluate such links. We focus on key above- and belowground production and hydrological transport processes that control the land-to-ocean flow of materials and their influence on nearshore marine ecosystems. We evaluate how these connections may be altered by global climate change and we identify knowledge gaps in our understanding of the source, transport, and fate of terrestrial materials along this coastal margin. Finally, we propose five priority research themes in this region that are relevant for understanding coastal ecosystem links more broadly.

The Kwakshua Watersheds Observatory, central coast of British Columbia, Canada

“…In the near term, ongoing observations will be used to further elucidate land‐sea linkages and landscape controls on hydrological and ecological processes, in the context of regional gradients (Figure 1; Bidlack et al, 2021) and collaboration networks (Bidlack et al, 2017; Sullivan et al, 2017). Over the longer term, the KWO aims to support a broad range of local‐level and network‐level studies that capitalize on the unique opportunities of this observatory to study the changing coastal margin ecosystem.…”

“…These factors result in highly dynamic and spatially variable catchment processes, which are challenging to measure and led us to use technologies for automated measurements. In this region, climate change is expected to increase the mean annual temperature, the mean annual precipitation (Wang et al, 2016) and the frequency of extreme precipitation events associated with atmospheric rivers (Radic et al, 2015; Sharma & Déry, 2019), among other changes with downstream implications (e.g., Bidlack et al, 2021; Shanley et al, 2015). Consequently, the KWO was designed to provide long‐term year‐round observations of weather, watershed hydrology and biogeochemistry and nearshore coastal ocean processes, in a poorly studied yet socially and economically important region.…”

Watershed Classification Predicts Streamflow Regime and Organic Carbon Dynamics in the Northeast Pacific Coastal Temperate Rainforest

“…Glacial and glacier supported regimes (Figure 7) are limited to high mountain watersheds in Southeast AK and BC (Figure 3), while a topographically controlled mix of pluvial and rain‐snow hybrid regimes dominate the rest of the SCR watersheds of Southeast AK (Curran & Biles, 2021; Edwards et al., 2013; O’Neel et al., 2015; Sergeant et al., 2020), BC (Bidlack et al., 2021; Eaton & Moore, 2010; Trubilowicz et al., 2013; Wade et al., 2001), and WA from Puget Sound northward (Fleming et al., 2007; Reidy Liermann et al., 2012; Sanborn & Bledsoe, 2006). Pluvial‐dominated hydrographs are nearly ubiquitous among SCRs south of Puget Sound WA (Bidlack et al., 2021; Lane et al., 2018; Reidy Liermann et al., 2012; Sanborn & Bledsoe, 2006), with a distinct “dry season” in CA (McManamay et al., 2014; Roden, 1967). By contrast, the comparatively “pure” nival regimes (Figure 7) are limited to the few large continental rivers that penetrate the coastal mountains from colder climates; for example, Skeena R. (Morrison et al., 2012) and Fraser R. (Fleming et al., 2007; Figure 3).…”

“…We used two separate approaches to place all watersheds into discrete types. First, we set aside 10 large continental watersheds (Figure S1 in Supporting Information S1) because we expected them to be fundamentally different from the SCR watersheds (e.g., Bidlack et al., 2021) in terms of catchment controls on river hydro‐biogeochemistry (e.g., watershed size, transit times, groundwater storage, agricultural land use, and fluvial network structure are likely of increasing importance). Second, we grouped the remaining 2,695 SCR watersheds into statistically similar clusters using k ‐means partitioning (Hastie et al., 2009) with 12 variables and 12 clusters, after exploring several permutations of different statistical clustering methods ( k ‐means, k ‐medoids, unsupervised random forest), different lists of input variables, and different numbers ( k ) of clusters (Figure 1).…”

Rain-fed streams dilute inorganic nutrients but subsidise organic-matter-associated nutrients in coastal waters of the northeast Pacific Ocean

“…Terrestrial dissolved organic-matter-bound Fe, which likely predominates in these watersheds, has been shown to be highly stable during estuarine mixing and can be transported well beyond the estuary to open waters where it can serve as a source of potentially limiting Fe (Herzog et al, 2020b). However, despite this stability, these complexes remain permeable to microbial siderophores (Batchelli et al, 2010), molecules with a strong affinity for Fe that are produced by microbes across a wide diversity of nutrient regimes in the coastal oceans (Boiteau et al, 2019). The quantification of dFe complexation and more broadly of fate (sedimentation, uptake) is an important next step within this region (Fig.…”