Heidi Hirsh et al., 2020

World - Acidifying Oceans Could Get Help from Kelp

Forests of fast-growing kelp influence the chemistry of the water in which they live. A new study evaluates their potential to ameliorate ocean acidification in sensitive coastal ecosystems.

Carbon dioxide is well known as a greenhouse gas, but its effects on climate and environments aren’t limited to the atmosphere. As more carbon dioxide fills the air, more of the gas dissolves into seawater, making the ocean more acidic and threatening marine organisms. Giant kelp may offer a local solution. As kelp grows, it captures carbon from the water and produces oxygen, possibly removing enough carbon dioxide to relieve acidification.

Hirsh et al. investigate conditions inside and outside a kelp forest in Monterey Bay, Calif., to evaluate kelp’s ability to mitigate ocean acidification in sensitive areas. Their study area experiences localized injections of deep water via upwelling events, in which equatorward winds push away surface water and draw up cold, low-pH (more acidic), low-oxygen water from offshore depths.

Upwelling also delivers nutrients, so upwelling events spark surges in kelp and phytoplankton growth and productivity. If the kelp-driven carbon fixing spurred by the nutrient inflow outpaces the amount of carbon brought up from deep water, kelp could start consuming anthropogenic carbon in the water, locally alleviating acidification stress.

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Read also Drivers of Biogeochemical Variability in a Central California Kelp Forest: Implications for Local Amelioration of Ocean Acidification, Heidi K. Hirsh et al., Oct. 22, 2020