Effects of Acidification on Submerged Aquatic Vegetation

The sandy shores that characterize the Mid-Atlantic coast are not particularly amenable to growth of seaweeds (marine algae) that flourish in rocky habitats to the north and coral reef environments to the south. However, the extensive system of bays, barrier islands and shallow coastal lagoons have been an important historical habitat for both fresh and saltwater vascular plants, collectively known as submerged aquatic vegetation (SAV). 

Despite their historic importance as shallow-water ecosystem engineers, or organisms that create or significantly modify a habitat, SAV populations in the Mid-Atlantic have been affected by slowly deteriorating water quality associated with human activity, combined with a disease outbreak in the 1930s that devastated eelgrass populations throughout the North Atlantic, and a series of hurricanes. In the Chesapeake Bay, SAV currently occupy less than 10% of their original habitat. Efforts to control nutrient and sediment loading from the land have led to improved water quality conditions in many areas and some SAV populations have recovered. Some areas have also been successfully restored such as on the Seaside of Virginia’s Eastern Shore where restoration efforts have resulted in the creation of over 7,000 acres of eelgrass and the re-introduction of bay scallops. However, there is concern for the future as CO2 induced climate warming may be particularly stressful for heat-intolerant species such as eelgrass.

(Photo: Maryland Department of Natural Resources)

Partial pressure carbon dioxide (pCO2) elevation has produced mixed effects on photosynthesis and growth of marine algae that frequently possess efficient mechanisms for exploiting bicarbonate (HCO3-) to support photosynthesis. In contrast, the photosynthesis of most SAV species, including wild celery, widgeon grass and eelgrass is limited by present day pCO2. Consequently, the negative effects of climate warming induced by elevated CO2 may be at least partially offset in these species by increased photosynthetic rates in an acidified coastal environment, as demonstrated by recent theoretical and experimental efforts.

(Photo: Courtesy NOAA/NEFSC)


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