Food Web Threats Reputed by Climate Change

Dogs feed on barkless on the shores of Swan Island in Maine. A new study documents the decline of these and three other intertidal species – at least due to climate change. Credit: Jonathan E. Fisher

The decline in shellfish species on rocky seashores corresponds to climate-driven changes.

Data from two decades of a study on Swan Island, Maine, document the slow and steady decline of muscles, barnacles and snails.

The waters of the Gulf of Oceans are heating up faster than the oceans almost anywhere on Earth. And as the level of carbon dioxide in the atmosphere rises, it is absorbed by the oceans, causing the pH level to fall. Ocean acidification makes it difficult for shellfish to thicken their shells – their primary defense against predators.

In a new study in the journal Communication biology, Researchers Peter Petraitis, a retired professor of biology at the Penn School of Arts and Sciences, and Steve Dudin, a professor of biology at California State University, Northridge, who completed a postdoctoral fellowship with Pennitis in the 1990s , Which reflects the changing climate. Taking a toll on the marine life of Maine. A dataset collected over two decades includes the numbers of five species, including musals, barnacles and snails, indicating that all are experiencing declines – some slower, some more rapid – due to climate change. .

“These species are often overlooked because of how common they are,” Petraitis says. “They are everywhere across rocky shores. People don’t think anything is going to happen to them. If they are reduced by about 3% in a year, this is a relatively small change, so that you may not notice it for some time. But in a year, people are suddenly going to look around and say, ‘Where are all the snails, muscles and barnacles? ”

Dudigen states that these species are “a major center of Gulf food”. “The concurrent decline of the five species, including both native and non-native, is proportionally larger, and can lead to profound changes in the ecology of coastal oceans in the region.”

In 1997, Petritis and Dudgene established a long-term experiment on the Gulf of Swan Island, Maine to study the ecological principles of several stable states. Concentrating on the topic of Petraitis’s research and his 2013 book, “Multiple Stable States in Natural Ecosystems”, the concept encapsulates the idea that an ecosystem is looking at the right environmental disturbances, completely different creations of organisms Can switch between quickly.

For shellfish on Swan Island, one such disturbance occurs when periodic powerful winter storms cause all the creatures associated with the reefs on the seaside to be driven out, forcing communities to rebuild from scratch next year .

In 1996, Petritis and Dudgins simulated the occurrence of a large-scale snowflake by cracking the rocks to see what the coast would recur. Since then researchers have been making annual visits to their 60 study plots on Swan Island, counting the incidence of organisms living not only in scraped areas, but also in abandoned areas in their natural state, control plots.

Given the five common shell species, the present work took advantage of the calculation of these control plots: turtle lime (Testudinalia testudinellis), common periwinkle (Littorina littorea), dogsque (Nussella lapillus), blue muscles (Mytilus edulis). The Barnacle (Semibalanus balanoids).

According to Petritis, “we did not expect to see much change in the control plots,” but we were surprised to see these restrictions. ”

Using abundance data from 1997 to 2018, the researchers found that very few young muscles were in the fastest free fall, declining by about 16% per year, while the other four species were declining 3 to 5% each year. Over that time period, there was a 50% drop in the total number of limpets, periwinkles, and dogworks, the researchers described as contractions.

On the question of why, researchers looked at data on ocean temperature and chemistry. They found that the downward trajectory of the Musals and Common Periwinkles matched the increase in summer sea temperatures collected from a nearby bua.

Meanwhile, the population decline of limpets and dogworks is accompanied by an increase in the symmetry state, a measurement that tracks with ocean pH. This was unexpected, since lower levels of aragonite saturation are associated with more acidic seaweed, making it harder for shellfish to form their shells. “It may be a sign of other conditions in the proximal regions that vary with the aragonite saturation state,” says Petritis.

Changes in sea temperature, pH, or changes in the arganite saturation state, along with other factors suggest that the decline does not have other factors.

All these species play an important ecological role in the Gulf of Maine.

Petras says that as filter feeders, the muscles and barnacles remove phytoplankton from the water column, “digested them, ejected them, and fertilized the shoreline.” Limpets and periwinkles feed on algae and seaweed, so small numbers of algul blooms and “greenery” may occur in adjacent areas.

As all five species act as prey for different types of animals, the shrinking population will revive the food chain, as well as affect humans.

“Transferring organic matter into the food web without animal consumption,” said Dudigen, “microorganisms produced in the coastal oceans will be shaken directly by the path of decomposition, not to support populations of species that human fish and Which coastal economies depend on. ”

Petritis also notes the common periwinkle, now emblematic of the coast, was introduced from Europe into the Gulf of Maine in the mid-19th century. “It is now the most common cemetery on the coasts – they feed like goats,” he says. “Before 1860, the shore without periwinkles probably looked a lot greener than it is now. As they decrease, we can see the shore back to its state in the 1850s.

Presenting these findings at conferences over the years, Petritis says he has heard anecdotes from other scientists about the disappearance similar to the Muscles in the North Atlantic, suggesting that the incident was reported from the Gulf of Maine Is not separated.

Reference: 20 October 2020, Communication biology.
DOI: 10.1038 / s42003-020-01326-0

Peter is a professor of biology in the Department of Biology at the Petraitis School of Pennsylvania.

Steve Dudigan is a professor of biology at California State University, Northridge.

The study was supported by the National Science Foundation (OCE-9529564, DEB-0314980, DEB-1020480, and DEB- 1555641).

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