Sentinel Sites

National marine sanctuaries are places where focused monitoring and research efforts take place that enhance our understanding of natural and historical resources and how they are changing. This allows them to serve as sentinel sites that provide early warning capabilities for detecting changes to ecosystem processes and conditions. The above icons identify the issues and threats that are common to multiple sanctuaries: climate change and ocean acidification, fishing impacts, human health, integrity of heritage resources, invasive species, marine debris, noise, vessel impacts, water quality, and wildlife health. For more information, visit

Climate Change & Ocean AcidificationClimate Change & Ocean Acidification

Ocean Acidification

From sea snails to scallops, many marine species like the red turban snail at right depend on hard shells made from calcium carbonate to protect them from predators, pounding surf and other threats. However, the changes in our climate are impacting these organisms.

photo of a scallop up close

Scallop, Gray’s Reef NMS. Photo: Greg McFall/NOAA

When we burn fossil fuels like oil and gas, we release carbon dioxide into the atmosphere, some of which is absorbed by the ocean. With more and more carbon dioxide from the atmosphere dissolving into the ocean, the chemistry of the ocean is changing and becoming less basic.

photo of pink and purple hydrocoral

Pink and purple hydrocoral, Cordell Bank NMS. Photo: Matt Vieta/BAUE

This ocean acidification reduces the amount of building material, or calcium carbonate, available to animals in the ocean. That makes it harder for organisms to form their calcium carbonate shells or can cause their shells to dissolve, threatening a number of shelled marine organisms.

photo of goose barnicles and mussels

Goose barnacles and mussels, Olympic Coast NMS. Photo: Elizabeth Weinberg/NOAA

Some sanctuaries, like Olympic Coast National Marine Sanctuary, are particularly vulnerable to the effects of ocean acidification. Researchers within national marine sanctuaries are working to understand the effects of ocean acidification so we can better protect these animals and the ecosystems that depend on them. By reducing the fossil fuels we burn, we can all help protect these ecosystems for the future.

photo of long

Long-spined sea urchin, Flower Garden Banks NMS. Photo: G.P. Schmahl/NOAA