Climate‐driven trends and ecological implications of event‐scale upwelling in the California Current System

Abstract

Eastern boundary current systems are among the most productive and lucrative ecosystems on Earth because they benefit from upwelling currents. Upwelling currents subsidize the base of the coastal food web by bringing deep, cold and nutrient-rich water to the surface. As upwelling is driven by large-scale atmospheric patterns, global climate change has the potential to affect a wide range of significant ecological processes through changes in water chemistry, water temperature, and the transport processes that influence species dispersal and recruitment. We examined longterm trends in the frequency, duration, and strength of continuous upwelling events for the Oregon and California regions of the California Current System in the eastern Pacific Ocean. We then associated event-scale upwelling with up to 21 years of barnacle and mussel recruitment, and water temperature data measured at rocky intertidal field sites along the Oregon coast. Our analyses suggest that upwelling events are changing in ways that are consistent with climate change predictions: upwelling events are becoming less frequent, stronger, and longer in duration. In addition, upwelling events have a quasi-instantaneous and cumulative effect on rocky intertidal water temperatures, with longer events leading to colder temperatures. Longer, more persistent upwelling events were negatively associated with barnacle recruitment but positively associated with mussel recruitment. However, since barnacles facilitate mussel recruitment by providing attachment sites, increased upwelling persistence could have indirect negative impacts on mussel populations. Overall, our results indicate that changes in coastal upwelling that are consistent with climate change predictions are altering the tempo and the mode of environmental forcing in near-shore ecosystems, with potentially severe and discontinuous ramifications for ecosystem structure and functioning.

Biodiversity and ecosystem functioning in dynamic landscapes

“…the indirect effects of environmental drivers). In this vein, the interaction between global-change drivers such as climate warming and eutrophication, and the multi-trophic structure of ecological communities are particularly important [71][72][73][74][75][76]. These studies demonstrate that in future research, the relative role of direct and indirect processes must be assessed from the perspective of understanding basic mechanisms [77], but also with a greater emphasis on providing 'actionable' knowledge to inform decision-makers [20].…”

Influence of larval behavior on transport and population connectivity in a realistic simulation of the California Current System

“…Some larvae may be able to return to shore as passive particles during downwelling periods or upwelling relaxation events (Roughgarden et al 1991;Farrel et al 1991;Wing et al 2003;Dudas et al 2009;Iles et al 2012). Larval recruitment also may be increased by timing reproduction to occur when offshore transport is reduced (Parish et al 1981;Shanks and Eckert 2005) and by larvae exploiting opposing, depth-varying cross-shore currents (Peterson 1998;Batchelder et al 2002;Shanks and Brink 2005).…”

Climatic and environmental factors influencing occurrence and distribution of macroalgae — a fjord gradient revisited

“…Large scale and mainly climate-driven changes have recently been observed in coastal ecosystems (Harley et al 2006, Parmesan 2006, Aksnes et al 2009, Iles et al 2012, Hernández-Fariñas et al 2014. The more long-lasting the fluctuations in the physical environment, the greater the ecosystem impacts (Sundby & Nakken 2008).…”