Move over polar bears, another predator along the Arctic coast
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in coastal ecosystems about North Pole Peninsula, polar bears They have always been considered top predators. But a new study suggests that sea stars could be surprising contenders to rival the famous polar bears at the top of the local food web.
A food web is a sprawling map of ecological links that connects all the different food chains within an ecosystem. Individual food chains contain primary producers that derive energy from the sun or by recycling dead organic matter; core consumers who patronize core consumers; Then secondary or tertiary consumers who prey on all consumers below them. But organisms in one food chain can also have a place in another, or several others, so the best way to see how an ecosystem works is to link those chains together.
In marine food webs, researchers often focus on surface food chains, or open waters, that contain small plankton living at the surface all the way up to large predators such as polar bears (sea bear), which are often located at the top of multiple food chains. But the seafloor, or bottom world, is often overlooked in marine food webs because scientists thought it had no true apex predators of its own.
But in a new study published December 27, 2022 in the journal Ecology (Opens in a new tab), the researchers took a more in-depth look at the coastal marine ecosystem in the Canadian Arctic and found that the benthic component of the region’s food web was significantly underappreciated. The research team created a detailed map of the different food chains surrounding Southampton Island, at the mouth of Hudson Bay in Canada’s Nunavut Territory, and found that the benthic part of the web has as many connections as its high-sea counterpart, as well as the polar bear’s own equivalent – predatory sea stars.
Related: A swarm of rainbow starfish devouring the carcass of a sea lion at the bottom of the sea
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“It’s a shift in our view of how the Arctic coastal marine food web works,” said the study’s lead author Remy Admiral (Opens in a new tab)said a marine ecologist at the University of Laval in Canada who was working with the University of Manitoba when the study was conducted in statment (Opens in a new tab). “We have demonstrated that land animals that live in seawater and those that live in sediments form two separate but interconnected sub-networks.”
The researchers analyzed data on 1,580 individual animals living in the coastal ecosystem of Southampton Island to create a new food web. They found that the benthic and pelagic components each have a similar number of steps, or trophic levels, in their respective food chains.
Sea stars were an essential part of the benthic food web, occupying different trophic levels, but one family, the Pterasteridae, has always been at the top of most individual food chains. The researchers discovered that these sea stars feed on a range of secondary consumers including bivalves, a group of molluscs whose bodies are protected by a hinged shell, sea cucumbers, and sponges. This means that the Pterastidae sea stars were hunting on an equivalent scale to polar bears, which preyed on walruses, gulls, and beluga whales (Delphinapterus leucas) and o-rings (dirty puss). The main difference between polar bears and sea stars was the size of their prey.
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In addition to being among the most successful predators in the entire ecosystem, Pterasteridae sea stars and polar bears also shared the ability and desire to forage, which researchers believe enabled both groups to thrive in the Arctic.
Sea stars feed opportunistically on dead marine organisms that have sunk to the sea floor, which means they have had to fish less. Similarly, dead washed up whales can be scavenged by polar bears, which they can keep for weeks or even months, the researchers wrote in the study.
The team believes the new findings highlight the importance of seafloor food chains in many other marine food webs. Pterasteridae sea stars are found in nearly all marine ecosystems, and if they are successful anywhere else as they are in the Arctic, they may turn out to be one of the ocean’s most successful predators, the researchers wrote.