Sea otter return boosts ailing seagrass in California

[Proof that nature can take care of her own, if only we'd step aside and let her...]

Sea otter return boosts ailing seagrass in California

By Suzi Gage BBC News

sea otter ecology A sea otter enjoys a crab in California, and helps seagrass in the process.

The return of sea otters to an estuary on the central Californian coast has significantly improved the health of seagrass, new research has found.

Seagrass was deemed to be heading for extinction in this region before the otters returned.

But scientists found that the animals triggered a chain reaction of events that boosted the water-dwelling plants.

The research is published in the journal, PNAS.

The urbanisation of California has led to a huge increase in nutrient pollution in coastal waters, from increasing use of nitrogen-rich fertilizers.

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“Start Quote

It’s almost like these sea otters are fighting the effects of poor water quality”

End Quote Brent Hughes University of California

This is said to be the reason for the dieback of seagrass, which has also been declining worldwide.

This research suggests that the hunting to near-extinction of sea otters in the late 19th and early 20th Century may have exacerbated the problem, and conversely that their reintroduction is helping revive ailing seagrass populations, even in the face of hugely nutrient-rich water.

Links in the chain

The researchers assessed seagrass levels over the past 50 years in the Elkhorn Slough in Monterey Bay, and mapped their increases and declines.

They looked at a variety of changes that may have affected the grass, but the only factor that really matched the changes in seagrass was sea otter numbers.

They theorised that sea otters were eating the crabs which prey upon small invertebrates in the water.

These invertebrates eat a type of algae which blooms when there are more nutrients in the soil. It grows on the leaves of the seagrass, shading them from sunlight and causing them to die back.

This is quite a complex cascade of effects, so the researchers tested out their theory by comparing similar estuaries with and without sea otters, and by doing experiments in the lab, and in the field.

These experiments, which included putting cages that sea otters either could or couldn’t access, down on the seagrass, confirmed their hypothesis.

otters Sea otters have been responsible for improving the health of the seagrass in these estuaries.

Brent Hughes, lead author of the study, said: “This estuary is part of one of the most polluted systems in the entire world, but you can still get this healthy thriving habitat, and it’s all because of the sea otters.

“So it’s almost like these sea otters are fighting the effects of poor water quality.”

Hughes described seagrass as “the canary in the coalmine” in terms of predicting levels of nutrient pollution in the water.

Foundation species

It also acts as a nursery habitat for many species of fish and it uses CO2 from sea water and the atmosphere, thus potentially helping with climate change.

Not only that, but it acts as protection to the stability of the shoreline.

Hughes said: “It’s what we call a foundation species, like kelp forest, salt marsh or coral reef. The major problem from a global perspective is that seagrass is declining worldwide. And one of the major drivers of this decline has been nutrient inputs from anthropogenic sources, via agriculture or urban runoff.”

These findings are of particular interest at the moment, as a ban on sea otters moving along the coast to southern California was lifted last year. The ban was in place as there was a fear the sea otters would impinge on fisheries in the area.

Hughes told BBC news: “That’s important because there’s a lot of these kind of degraded estuaries in southern California because of all the urban runoff from places like Los Angeles and San Diego.

“Coastal managers will now have a better sense of what’s going to happen when sea otters move in to their systems.

“There’s a huge potential benefit to sea otters returning to these estuaries, and in to these seagrass beds that might be threatened.”

Otters—a Pinnacle of Evolution

As is often the case, I awoke this morning to the sensation of our cat walking gingerly across my head. Sleek and silky, with luxuriant dark fur, Winnie reminds me of the river otter I saw yesterday afternoon crossing the road and heading upstream into our backyard beaver pond system.

I’d been hoping the otter I have been seeing in the waterways nearby would find our ponds, which are fed by several small streams flowing out of the surrounding hills. Though the ponds turn a light brown this time of year from the clay-rich soil leaching from their banks, they support a healthy variety of life, from frogs, fish and crawdads; to ducks, herons, kingfishers and osprey; to beaver, muskrat, raccoon, mink…and now otter.

A descendant of the diverse weasel family, the river otter is a pinnacle of evolution if ever there were one. While their kin adapted to every other habitat in North America—the ermine and pine marten, to the snowy north woods; fisher, the ancient forests; mink, the riparian zones; badger, the arid plains; and wolverine, the mountainous high country—river otters are masters of inland waterways and freshwater lakes. To those who know them, “otter” is synonymous with the word “play.” Among the most spirited of species, they clearly enjoy themselves in the water, delighting in games with each other like tag and hide-and-go-seek. They also enjoy snow sports: otter “slides” are a familiar sight on snowy slopes along frozen rivers in winter.

Like every other fur-bearer on the continent, otters were nearly decimated during the mindless fur trade era. Unbelievably, otters are still killed in traps set by nineteenth century throw-backs even today. Others are shot by selfish humans unwilling to share aquatic resources that otters had adapted to hundreds of thousands of years before Homo sapiens reached the Western Hemisphere.

The threat of human greed is even more pervasive for sea otters, who have all but lost their ability to move about on land, giving themselves and their terrestrial origins up to their oceanic habitat. Unlike commercial fishermen, they don’t sit out the storms in a cozy home or a dry shack heated by an oil furnace; they spend day and night floating among the coastal kelp beds.

River otter are more than welcome to stay as long as they like here in our beaver ponds. Hopefully we’ll get an occasional glimpse of them swimming fluidly by, or moving on land with their trademark weasel-esque, undulating lope. I’m just glad Winnie is lighter afoot when she tip-toes across my head in the morning.

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Back To the Bad Old Days

What’s up with all the anti-wildlife legislation going on around the country these days? Everywhere you look there’s some state senator or representative introducing bills to keep non-human animals down and implement some new form of cruelty to punish them for the crime of not being born of our privileged species.

A few examples: a self-amused eastern Washington representative is calling for east-side wolves to be moved out of his district to the west side of the Cascade Mountains; at the same time Washington State politicians just introduced three bills to make it easier for ranchers to use lethal measures on wolves whenever they see fit; and of course you’ve heard that Montana’s public servants are on a rampage to get rid of their resident wolves. Now one of their legislators wants to lower the minimum hunting age for that state to nine years old.

Meanwhile, in Alaska, a senator just put forth legislation to instate a $100.00 bounty on sea otters! Never mind that these playful, aquatic mammals were nearly completely wiped out during the fur trade era, are critically endangered or extinct from much of their former range and are still listed in Alaska as Threatened or Endangered under the federal ESA, those poor, underpaid (sarcasm intended) commercial crab fishermen see them as competition. (Far from downtrodden, crabbers take pride in being the wealthiest of commercial fishermen; no doubt the senator who proposed the bounty is counting on a kickback into his campaign coffers from the crabbing industry for his otter oppression bill.)

And the list of detrimental anti-wildlife legislation goes on and on.

Is it just me, or have good ol’ boy state politicians stepped up the pace of non-human animal persecution? It’s as though they’re intentionally trying to drag us back to the bad old days of the 1800s, arguably this country’s most reckless period for uncontrolled animal exploitation—besides, perhaps, the present.

Take Action:

Not surprisingly, state legislators only take input from residents of their given state, but since there are bogus bills and measures cropping up across the country, there should be something to speak out against wherever you live. For instance, if you live in Washington State, contact your senator and urge them to oppose anti-wolf bills SB 5187, SB 5188 and SB 5193. Let them know:

  • These three bills would undermine the state’s wolf management plan by giving authority to the county legislators and local sheriffs over the state wildlife agency biologists, and would allow the public to override the state and kill wolves perceived to be a threat to livestock on public and private lands.
  • There are only 50 wolves in Washington.  Now is not the time to remove their protection.
  • Washington’s wolf management plan was created with massive public involvement and adopted unanimously by the Washington Wildlife Commission; powerful ranching advocates should not be allowed to undermine it.
Text and Wildlife Photography ©Jim Robertson, 2013. All Rights Reserved

Text and Wildlife Photography ©Jim Robertson, 2013. All Rights Reserved