Norwegian Polar Institute - How Will Acidification Of Arctic Ocean Affect Zooplankton, Food Chain?
In the ocean, zooplankton are a crucial link between energy-producing phytoplankton and fish. We have studied how changing acidity might affect zooplankton. Although recent research has revealed a complex web of interactions between plankton species, the notion of a linear food chain from phytoplankton via zooplankton to fish is still valid as a model for the transport of energy from primary producers to fish stocks in arctic waters. There, most fish larvae rely on zooplankton for food. This makes the arctic ecosystem particularly vulnerable to perturbations that affect zooplankton productivity. One focus of concern is how arctic zooplankton populations will evolve in the face of climate change and ocean acidification (OA).
Just as arctic ecosystems are vulnerable to perturbation, the waters of the Arctic are vulnerable to OA. Present OA rates are far higher here, and they are expected to remain so for three reasons. First, melting sea ice has low capacity to buffer acidity. Second, although the Arctic Ocean constitutes only 1% of the global ocean volume, it receives 11% of the discharge from rivers, which not only has low buffering capacity but also brings significant amounts of terrestrial carbon, which may ultimately be transformed to CO2 by microbial respiration. Finally, increasing inflow from the North Atlantic transports large amounts of anthropogenic CO2 to the Arctic Ocean. Arctic organisms are therefore the first to face the effects of OA and will face stronger OA in the future.
Unfortunately, arctic species may also be less well equipped to handle decreasing pH than most other marine invertebrates. Unlike lower-latitude species that tolerate a wide range of temperatures, true polar species perform best at low temperatures. But this advantage comes at a price. Polar marine invertebrates have less energy available for cellular pH regulation.
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Pteropods are another group of keystone species in the Arctic. While their biomass does not rival that of the Calanus species, they also contribute to the diet of many fish species. These mollusks build calcium carbonate shells, which are sensitive to corrosion when pH decreases. Studies have shown that shell integrity is compromised at OA levels predicted for year 2100 with increased mortality as a result.
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https://thebarentsobserver.com/en/node/4973
