August 29, 2022 — The following was released by the Science Center for Marine Fisheries:

As parts of the Atlantic Ocean warm at unprecedented rates, researchers are looking to past warming trends to help understand how previous changes in climate have influenced marine life. A new study looks at the fossil record of one of Earth’s longest-lived species to provide new insights into historic changes in climate, and the impacts that it caused.

Published in the journal Holocene and funded by the Science Center for Marine Fisheries (SCEMFIS), the study looks at the fossil record of ocean quahogs to chart historical changes in ocean temperatures over the Holocene period, which covers the last 10,000 years of Earth’s history. Because there are no direct measurements of ocean temperatures for much of this period, indirect measures, like fossil records, can help reconstruct some of that history.

Ocean quahogs in particular are useful for this type of reconstruction. They can only live in colder waters, below 16 degrees Celsius. Since much of the Northwest Atlantic is warmer than that, their habitat is currently limited to grounds that are part of the Mid-Atlantic Cold Pool, a recurring area of cold bottom water in an area of the Atlantic known as the Mid-Atlantic Bight.

Because ocean quahogs prefer the waters of the Cold Pool to the surrounding waters, the change in ocean quahog habitats over time can also serve as a proxy for changes in the Cold Pool, and regional water temperatures, over the same period. Dating ocean quahog shells thus gives a history of climate change in the region.

The study accomplished this by collecting samples of ocean quahog shells from an area off the coast of the Delmarva Peninsula, inshore from the species’ current range, as well as live ocean quahogs from areas off New Jersey, Long Island, and Georges Bank. The shells were radiocarbon dated to determine the approximate ages of when the ocean quahogs were alive; the radiocarbon dates for these animals varied from 4,392 to 61 years ago, with most of the sampled shells being born during the early-to-late 1800s.

The study found that, in the last 200 years, the Cold Pool extended both further south and further inshore than its current location. Temperature shifts, specifically warming, since the late 1800s led to a shift in the range of ocean quahog habitats away from these inshore areas during the 20th century. Taking a longer look at the entire Holocene period, the distribution of ocean quahogs expanded inshore during all previous cold periods, including most recently during the Little Ice Age, and retracted offshore during the intervening warm periods.

“This study gives us an important new tool in studying past climate changes in the Atlantic Ocean,” said Dr. Roger Mann, of the Virginia Institute of Marine Science, one of the authors of the study. “Knowing how ocean quahogs have previously responded to a warming ocean gives us insights into how they will respond in the future.”

“Since about 5,000 years ago, ocean quahogs have moved onshore and offshore at least 4 times commensurate with a warming and cooling ocean,” said Dr. Eric Powell, of the University of Southern Mississippi, another author of the study. “This study shows the potential for ocean quahogs to serve not only as a recorder of temperature change, but also a tracker of the migration of species across the continental shelf in response to climate change, and demonstrates the resiliency of this long-lived species to a shifting climate.”

About SCEMFIS

SCEMFIS utilizes academic and fisheries resources to address urgent scientific problems limiting sustainable fisheries. SCEMFIS develops methods, analytical and survey tools, datasets, and analytical approaches to improve sustainability of fisheries and reduce uncertainty in biomass estimates. SCEMFIS university partners, University of Southern Mississippi (lead institution), and Virginia Institute of Marine Science, College of William and Mary, are the academic sites. Collaborating scientists who provide specific expertise in finfish, shellfish, and marine mammal research, come from a wide range of academic institutions including Old Dominion University, Rutgers University, University of Massachusetts-Dartmouth, University of Maryland, and University of Rhode Island.

The need for the diverse services that SCEMFIS can provide to industry continues to grow, which has prompted a steady increase in the number of fishing industry partners. These services include immediate access to science expertise for stock assessment issues, rapid response to research priorities, and representation on stock assessment working groups. Targeted research leads to improvements in data collection, survey design, analytical tools, assessment models, and other needs to reduce uncertainty in stock status and improve reference point goals.