Effects of Ocean Acidification on Temperate Coastal Marine Ecosystems and Fisheries in the Northeast Pacific

Abstract

As the oceans absorb anthropogenic CO2 they become more acidic, a problem termed ocean acidification (OA). Since this increase in CO2 is occurring rapidly, OA may have profound implications for marine ecosystems. In the temperate northeast Pacific, fisheries play key economic and cultural roles and provide significant employment, especially in rural areas. In British Columbia (BC), sport (recreational) fishing generates more income than commercial fishing (including the expanding aquaculture industry). Salmon (fished recreationally and farmed) and Pacific Halibut are responsible for the majority of fishery-related income. This region naturally has relatively acidic (low pH) waters due to ocean circulation, and so may be particularly vulnerable to OA. We have analyzed available data to provide a current description of the marine ecosystem, focusing on vertical distributions of commercially harvested groups in BC in the context of local carbon and pH conditions. We then evaluated the potential impact of OA on this temperate marine system using currently available studies. Our results highlight significant knowledge gaps. Above trophic levels 2–3 (where most local fishery-income is generated), little is known about the direct impact of OA, and more importantly about the combined impact of multi-stressors, like temperature, that are also changing as our climate changes. There is evidence that OA may have indirect negative impacts on finfish through changes at lower trophic levels and in habitats. In particular, OA may lead to increased fish-killing algal blooms that can affect the lucrative salmon aquaculture industry. On the other hand, some species of locally farmed shellfish have been well-studied and exhibit significant negative direct impacts associated with OA, especially at the larval stage. We summarize the direct and indirect impacts of OA on all groups of marine organisms in this region and provide conclusions, ordered by immediacy and certainty.

The sensitivity of estuarine aragonite saturation state and pH to the carbonate chemistry of a freshet-dominated river

“…1) is a large (∼ 6800 km 2 , > 400 m deep), temperate, semi-enclosed, fjord-like estuarine sea with strong seasonal stratification, productivity, and carbonate chemistry cycles Ianson et al, 2016). This high productivity supports abundant populations of shellfish, finfish, and other higher organisms that may be sensitive to pH and A anomalies (Haigh et al, 2015). The Fraser River, the primary freshwater source, drains approximately 238 000 km 2 with seasonally variable discharge (∼ 800 to 12 000 m 3 s −1 at Hope, ECCC data, http://wateroffice.ec.gc.ca) due to summer snow/ice melt and lack of dams throughout most of the watershed.…”

“…M. rubrum (a ciliated protozoan) retains functional chloroplasts during grazing and uses them to perform photosynthesis. Calcifying phytoplankton (e.g., coccolithophores) are assumed to contribute minimally to productivity in the Strait of Georgia (Haigh et al, 2015) and were absent from satellite observations in the strait prior to 2016 (Jim Gower, personal communication, 2014; NASA Earth Observatory, http://earthobservatory.nasa.gov/IOTD/ view.php?id=88687; last access: 13 June 2018) -they are not explicitly modeled.…”

“…Critical trophic links within many of these ecosystems may be negatively impacted by increases in dissolved inorganic carbon (DIC) and reduced pH associated with ocean acidification (Haigh et al, 2015). Those organisms using the calciumcarbonate mineral form aragonite in their external hard parts (e.g., some molluscs) are especially vulnerable since oceanic CO 2 uptake lowers the aragonite saturation state ( A ) of seawater (Waldbusser et al, 2015).…”

The sensitivity of estuarine aragonite saturation state and pH to the carbonate chemistry of a freshet-dominated river

“…1) is a large (∼6800 km 2 , >400 m deep), temperate, semi-enclosed, fjord-like estuarine sea with strong seasonal stratification, productivity, and carbonate chemistry cycles (Moore-Maley et al, 2016;Ianson et al, 2016). This high productivity supports abundant populations of shellfish, finfish, and other higher organisms that may be sensitive to pH 5 and Ω A anomalies (Haigh et al, 2015). The Fraser River, the primary freshwater source, drains approximately 238,000 km 2 with seasonally-variable discharge (∼800 to 12,000 m at Hope, ECCC data, http://wateroffice.ec.gc.ca) due to summer snow/ice melt and lack of dams throughout most of the watershed.…”

Pacific Salmon and Steelhead: Life in a Changing Winter Ocean

“…By the end of the 21 st Century, multiple stressors from anthropogenic climate change and ocean acidifi cation are expected to aff ect salmon and the fi sheries that depend on them (Haigh et al 2015). For example, increases in sea surface temperatures due to greenhouse gas emissions are predicted to shrink the thermal habitats of salmon over vast regions of the North Pacifi c Ocean and adjacent seas (Welch et al 1998a, b;Azumaya et al 2007;Abdul-Aziz et al 2011;Kaeriyama et al 2012Kaeriyama et al , 2014.…”