[Animals] How Sea Otters Protect Seagrass Meadows

[Akrapovic]

These endangered predators strengthen the genetic diversity of seagrasses, making threatening seagrass environments more resilient.

 

 

Covered in lustrous fur, the thickest in the animal world, sea otters live their entire lives in the ocean, feeding profusely on ocean floor animals such as shells and crustaceans.

In British Columbia, Canada, sea otters often eat clams, which burrow in the grasslands of eelgrass (Zostera marina), a widespread species of marine plant. Otters use their sensitive whiskers and front claws to feel for clams on the soft ocean floor. When they find one, they dig it up and pry it open, or use a rock to break the shell, before devouring it.

The eelgrass meadows where sea otters live are patched and filleted where animals have scratched, while the non-animal meadows have a dense blanket of vegetation. Put like this, it would seem that what otters do is more destructive than constructive, but nothing could be further from the truth.

It turns out, that tenant otter meadows are hardier, with more genetically diverse seagrasses, according to a new study published Oct. 14 in the journal Science. That's because, by foraging, and gently distorting, the ocean floor, otters force plants to flower and produce seeds. What's more, its excavations provide more space and light for the seeds to settle and germinate.

The discovery is a great example of how predators like otters influence their ecosystems beyond predation, usually in an invisible and little-known way, says study director Erin Foster, a research associate at the Hakai Institute, an organization. British Columbia-based non-governmental organization for coastal and conservation studies.

It also means that sea otters, an endangered species, are vital to their environments and give eelgrass meadows a better chance of being healthy and surviving. The eelgrass and other marine plants are in danger globally, in part due to warming waters caused by climate change, Jane Watson, co-author of the study and emeritus professor of marine ecology at the University of Vancouver Island (Canada) .

Seagrass beds are also important nurseries for many fish and crustaceans, provide food for many animals such as gray whales and sea turtles, absorb greenhouse gases, and filter harmful pollution and bacteria from the water.

"Genetic diversity often provides resistance to change and considering the challenges we face ... this will be important for eelgrass meadows," says Foster, who conducted this study while completing his PhD at the University of Victoria, Canada. ).

The great otter hunt
In their day, sea otters spread through the coastal waters that ran from the southern tip of the Baja California peninsula (Mexico), up to Alaska and the Aleutian Islands and reaching Russia and Japan. But, after European colonization, they were a great target for hunters for their fur, especially in the 19th century. This reduced their po[CENSORED]tion from about 300,000 to less than 2,000 at the beginning of the 20th century. Fortunately, small po[CENSORED]tions of otters survived in Alaska and California, and today they have returned to parts of the west coast of North America.

In North America there are two subspecies, the southern sea otter (found in California) and the northern sea otter. The fondness of sea otters for eating sea urchins is well known, which can devastate kelp forests if their po[CENSORED]tion is not controlled or their predators disappear. Scientists have shown that the introduction of sea otters and their expansion into areas where the po[CENSORED]tion of the Pacific purple sea urchin is rampant restores balance in the ecosystem, and for that reason otters are known both as a key species and ecosystem engineers.

But Foster and his team were curious about what impact otters had on seagrass beds, a less studied element of their biology.

Hunting made otters locally extinct in British Columbia in the early 1900s, and all animals now found in the region are descendants of 89 sea otters reintroduced to the region between 1969 and 1972 from Alaskan po[CENSORED]tions. One of the introductions consisted of a group of sea otters from the island of Amchitka, which were evacuated before a nuclear test that was carried out there in 1972.

Since then, the po[CENSORED]tion in British Columbia has grown to nearly 8,000, Watson says, even though they only occupy half the territory they occupied two centuries ago.

This uneven distribution allowed Foster and his team to accurately compare eelgrass meadows with and without these predators. To see the impact of the animals, they looked at the richness of the alleles

 

LINK: https://www.nationalgeographic.es/animales/2021/10/como-las-nutrias-marinas-protegen-las-praderas-submarinas