Otters busy helping environment
Fertilizer runoff has led to a global decline in seagrass meadows, which provide crucial habitat for fish. But thanks to sea otters, these meadows are flourishing in Elkhorn Slough, a major estuary in Monterey Bay, Calif., scientists say.
Fertilizer from farms in Salinas flows into Elkhorn Slough, carrying phosphates and other nutrients that fuel the growth of algae on seagrass leaves. As the algae blooms, it shades seagrass from sunlight it needs to grow.
In fact, nutrient levels are so high in Elkhorn Slough that scientists wouldn't expect seagrasses to survive there. Yet in recent years, the estuary bed has been teeming with the lush, green grass.
“There's more seagrass in the slough than there's ever been,” said study leader Brent Hughes, a marine ecologist at the University of California, Santa Cruz.
To find out why, he and his colleagues combed through surveys conducted by the California Department of Fish and Wildlife and other agencies that tracked the growth of seagrass in Elkhorn Slough during the last 50 years. Fertilizer runoff nearly wiped out the seagrasses, but they began expanding in 1984 — right when sea otters began recolonizing Elkhorn Slough, the researchers reported on Monday in the Proceedings of the National Academy of Sciences.
Sea otters once thrived along the California coast, but the fur trade nearly drove them to extinction in the early 1900s. Since then, conservation efforts have helped them recover and repopulate their former habitats, including Elkhorn Slough.
Since sea otters returned to the estuary, the seagrass has expanded sevenfold. But how did the otters boost its numbers? The researchers suspected that the otters fed on a predator that affected the plant's growth.
The only predators sea otters eat are crabs, which feed on invertebrates — such as sea slugs — that nibble algae off seagrass leaves. With fewer crabs to prey on them, these grazers grow more abundant, keeping seagrass leaves clean and healthy.
To test whether crabs really were the missing link, the researchers compared seagrasses in Elkhorn Slough with those in Tomales Bay, an estuary that has a similar ecosystem, but with low levels of nutrient runoff and no otters.
The researchers also simulated the effects of otters in the ecosystem using enclosures in Elkhorn Slough. One of the enclosures contained the large crabs one would expect to find when otters aren't around to eat them; the other had the smaller crabs found when otters are present. As expected, the seagrass grew larger and faster in the enclosure with the smaller crabs.
Show commenting policy
TribLive commenting policy
You are solely responsible for your comments and by using TribLive.com you agree to our Terms of Service.
We moderate comments. Our goal is to provide substantive commentary for a general readership. By screening submissions, we provide a space where readers can share intelligent and informed commentary that enhances the quality of our news and information.
While most comments will be posted if they are on-topic and not abusive, moderating decisions are subjective. We will make them as carefully and consistently as we can. Because of the volume of reader comments, we cannot review individual moderation decisions with readers.
We value thoughtful comments representing a range of views that make their point quickly and politely. We make an effort to protect discussions from repeated comments either by the same reader or different readers.
We follow the same standards for taste as the daily newspaper. A few things we won't tolerate: personal attacks, obscenity, vulgarity, profanity (including expletives and letters followed by dashes), commercial promotion, impersonations, incoherence, proselytizing and SHOUTING. Don't include URLs to Web sites.
We do not edit comments. They are either approved or deleted. We reserve the right to edit a comment that is quoted or excerpted in an article. In this case, we may fix spelling and punctuation.
We welcome strong opinions and criticism of our work, but we don't want comments to become bogged down with discussions of our policies and we will moderate accordingly.
We appreciate it when readers and people quoted in articles or blog posts point out errors of fact or emphasis and will investigate all assertions. But these suggestions should be sent via e-mail. To avoid distracting other readers, we won't publish comments that suggest a correction. Instead, corrections will be made in a blog post or in an article.
- State AGs lambaste climate proposal, predicting higher electricity prices, job losses
- First, ‘Watson’ wins ‘Jeopardy’; now, he helps treat cancer
- Texas attack called ‘textbook’ lone-wolf case
- $5.6B in education tax credits dubious
- Federal appeals court flips on cell location records ruling in Florida
- AG vows to help better Baltimore police
- 56 years later, Ohio fugitive captured in Florida
- Trucking interests trump safety in $55.3B transportation spending bill
- Researchers find new, elusive bird species
- Utah outpost stands in for Mars
- Ousted Secret Service agent Smith remains on payroll, House committee learns