How does rising atmospheric CO2 affect marine organisms?

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The Positive Response of Two Eelgrass Populations to CO2 Enrichment

Paper Reviewed
Zayas-Santiago, C., Rivas-Ubach, A., Kuo, L.-J., Ward, N.D. and Zimmerman, R.C. 2020. Metabolic profiling reveals biochemical pathways responsible for eelgrass response to elevated CO2 and temperature. Scientific Reports 10: 4693.

Seagrasses are key ecosystem engineers in marine environments, providing productive habitats for numerous species. They are also widely distributed across the world oceans, spanning a considerable range of thermal environments. Consequently, researchers have long been interested in their response to projections of future climate change.

A recent example of such work comes from the study of Zayas-Santiago et al. (2020). Focusing on Zostera marina (eelgrass), a seagrass species inhabiting the Atlantic and Pacific coasts of the United States, the five scientists examined the growth performance and metabolic profile of two distinct populations across a range of five pCO2 levels spanning seawater pH values of approximately 8.0 (ambient) down to 6.0 (highly enriched with pCO2). Samples of the two populations were acquired from Puget Sound (a cold-water environment from Dumas Bay, Washington, USA) and the Chesapeake region (a warm-water environment from South Bay, Virginia, USA). Shoots of the collected species were transported to the Virginia Aquarium & Marine Science Center (Virginia Beach, Virginia) where they were placed in outdoor aquaria supplied with seawater from an adjacent estuary that was modified to the prescribed seawater pH treatment. The length of the experiment lasted one full year.

In describing their findings Zayas-Santiago et al. report the two eelgrass populations each experienced overall enhancements in plant size, growth and survival in response to CO2 enrichment. What is more, elevated CO2 stimulated growth-related metabolites while suppressing those associated with stress, indicating an improved tolerance to high temperature in addition to improvements in growth.

Commenting on these important findings the scientists say their findings "suggest that seagrass populations will respond variably, but overall positively, to increasing CO2 concentrations, generating negative feedbacks to climate change [by sequestering increased amounts of carbon]."

Posted 18 November 2020