It’s time to get local about marine climate change

Oysters in the Mook Sea Farm hatchery in Walpole, Maine, on Jan. 7, 2015. Chris Adams | TNS

On Aug. 22, the first ever Northeast Shell Day has been planned as a single-day monitoring blitz aimed to create a snapshot of coastal marine conditions. The project strives to support a network approach generating science that can lead to improving local and state decision making that addresses ocean and coastal acidification.

Climate change projections for ocean acidification anticipate a world with steep declines in populations of shellfish and calcifying organisms. The amount of carbon dioxide (CO2) dissolved in ocean water can determine the acidity of seawater, and the oceans are getting progressively more acidic with rising atmospheric CO2 levels.

Already in the Northeast and Gulf of Maine acidification is harmful to shellfish; slowing growth rates and weakening the immune system’s ability to ward off disease, causing shells to be smaller and softer, and limiting the survival of juvenile bivalves. These effects threaten to decrease the abundance of commercial species available for harvest. They could also impact water quality as large populations of shellfish help to filter and clean seawater.

Thus, in the Northeast as well as many other coastal locations, marine research teams are investigating how soon baseline populations may shift as a result of acidification and other co-stressors of climate change, and how intensely communities will feel the impact on environmental well-being and livelihoods.

In the past two centuries, burning fossil fuels has already caused the open ocean’s surface to become 30 percent more acidic. However, acidification in the near shore environment (which is called coastal acidification) is also driven by the CO2 produced from the decomposition of organic material on the seafloor. Marine mud can be a compost pile — with too much material decomposing, episodic spikes in CO2 result in local acidification events magnified beyond the global trends of climate change. Living and photosynthesizing marine plants and algae have the opposite effect, taking up CO2 and reducing acidification. However, overstimulated growth of planktonic microalgal will produce extra material that falls to the bottom and decomposes, thereby exacerbating the problem.

Maintaining a healthy balance between the compost pile and the garden of photosynthesis in coastal waters is remarkably important for protecting coastal ecosystems. In certain locations, improving nutrient pollution to the coastal environment and helping to ensure healthy habitats for shellfish can reduce the risk of acidification from globally rising atmospheric carbon dioxide.

However, throughout the thousands of miles of Northeast coastline, conditions of coastal acidification vary and are affected by many different drivers including the freshwater from rivers, the underlying chemistry of bedrock and soils among watersheds, and the amount of open ocean water that enters each estuary.

The water monitoring blitz taking place on Shell Day is a part of a broader search for regional understanding at the local scale. A growing and collaborative community of water monitoring groups, state agencies, research scientists, aquaculturists and fishermen are uniting around this issue. Policy making that explores state management has recently begun, and there is a regional effort underway to better study and adapt to coastal acidification in the Northeast.

Ask your local water monitoring organization if they are working with Shell Day and find out more at necan.org/shellday.

Parker Gassett, Bangor Daily News, 5 August 2019. Article.

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