Effects of Climate Change on Marine Life

Aerial view of seal colony © Karl Swenson
Aerial view of seal colony © Karl Swenson

Marine life faces challenges from warming waters and ocean acidification. Warming waters alter the latitude and depth at which certain species are able to survive, so many species are moving deeper or father north in the Atlantic to find cold water. More acidic oceans keep crustaceans, coral, and other organisms from developing. 

The result is widespread disruption of interconnected food webs.

Moving Northward & Deeper

Overall, marine species are responding to warmer temperatures by moving northward or deeper when possible in search of cooler waters.

On average, for 105 northern species in water off the northeastern U.S. and in the Bering Sea have shifted northward by about 10 miles between since 1982. They have also moved an average of 20 feet deeper. Since the late 1960s, three economically important species, American lobster, red hake, and black sea bass, have shifted northward 119 miles, on average.

Change in latitude and depth of marine species graph © EPA


The graphs above show the average shift northward and toward deeper waters of 105 marine species along the Northeast coast and in the eastern Bering Sea.

Sea Turtles

Mass Audubon staff member examining a sea turtle © Esther Horvath
Mass Audubon staff member examining a sea turtle © Esther Horvath

Wellfleet Bay Wildlife Sanctuary has been tracking the number of cold-stunned sea turtles on Cape Cod since 1979, helping understand juvenile sea turtle population changes and behavior over several decades.

Much is still unclear about sea turtle behavior, but cold-stun stranding numbers are increasing rapidly. This increase is likely due to a combination of successful conservation efforts on the nesting beaches in Mexico and Texas and changes in ocean temperatures, and possibly currents, driven by climate change.


American Lobster © Patrick Randall
© Patrick Randall via Flickr

Warmer sea surface temperatures are forcing lobster populations northward, disrupting ecosystems and the coastal economies that depend on them. The lobster industry in southern New England has virtually collapsed. Since 1996, New York’s registered lobster landings dropped more than 98%. Connecticut is seeing the same, with a drop of about 97%, while Rhode Island a decline of more than 70%. 

That doesn’t mean the lobster populations have dropped overall. They are, in fact, remaining relatively stable, in part due to forward-thinking management practices, but they are being found farther north. While southern New England is losing lobsters, Maine is reaping the benefits with a 219% increase in registered lobster landings since 1994.

The challenge ahead is that lobster populations will not settle into place—they will keep moving northward until they run out of suitable habitat.

Blue Crabs

Blue crab © Jennifer Childs

Historically, Cape Cod marked the northern extent of blue crabs’ range. They were found south of the Cape, but not north. In recent years, that has change with warming waters and an enhanced gulf stream.

It’s unlikely that blue crabs will be able to reliably breed in cooler waters north of the Cape. They may, however, increase in population off of New York, and during warm years, gain a temporary foothold in the Gulf of Maine. 

It will take decades to understand the pace at which climate change is affecting their range.

Coastal Birds

Roseate tern with chicks © Jean Hubble
© Jean Hubble

As our oceans warm, rising seas, stronger storms, and erosion will continue to impact many of our coastal breeding birds.

In many cases, salt marshes will be unable to expand inland to offset losses to sea level rise, and salt marsh specialists like saltmarsh sparrows, seaside sparrows, willets, and clapper rails will lose precious habitat.

High-intensity storms will continue to degrade and destroy beach-nesting habitat for species like piping plover, roseate tern, and American oystercatcher.

Marine Life & Ocean Acidification

Ocean acidification is impacting marine ecosystems in a number of ways. The thin shells of some pteropods, for example, can be completely dissolved within a month at the levels of acidity found off the New England coast. And there is a detrimental side effect.

In creating carbonic acid, free hydrogen ions are created. Those hydrogen ions react with carbonates to create additional carbonic acid, but those carbonates are needed by organisms to grow shells. The process of ocean acidification steals the molecules needed for organisms to thrive, in addition to corroding their shells and making the waters otherwise inhospitable. It’s a double whammy.

The coral, pteropods, shellfish, and crustaceans threatened by ocean acidification also serve as food sources for many other types of marine life and seabirds. As some species feel the direct effects and struggle, other food webs begin to collapse as well.

The potential cascading impacts of ocean acidification on the world’s global food supply and the health of its oceans cannot be overstated.