The new study, published in Science journal, reveals that the genetic diversity of eelgrass “was significantly higher where otters were present and that the impact was related to time: Longer otter presence was associated with higher genetic diversity”.
The Canada-based study, led by ecologist Erin Foster and biologist Jane Watson and supported by the Hakai Institute, collected 462 eelgrass shoots which are commonly found in the North Pacific Ocean. Collecting cuttings from 15 different meadows, the research team took six cuttings from areas where otters are known to have lived for more than 30 years, three cuttings from areas where otters have returned to in the past ten years, and six cuttings from areas where otters were wiped out by humans around 100 years ago. Ultimately, the DNA revealed that the seagrass from areas with long-established sea otter populations had 30 per cent higher genetic diversity.
The reason behind the increased genetic diversity, argues the study, is simple. When otters dig in seagrass meadows to look for clams, they tend to disturb seagrass roots and leave plenty of craters and holes in the ground. This, in turn, fuels the flowering rate of seagrass (seagrasses are known to be the only flowering plants that can pollinate under water) and therefore the reproduction rate. Seagrass can also reproduce in a somewhat different way: they are able to clone themselves asexually. While an entire meadow could grow while cloning itself, the similar DNA strands would leave the seagrass more exposed to environmental changes.
Not only do these findings point out, once again, how intrinsically linked everything is in ecosystems, but they also offer ideas on how to restore seagrass meadows around the world. Seagrass is known to remove carbon from the atmosphere around 30 times quicker than a rainforest. That’s why restoring seagrass meadows is such an important task to fight climate change. In the UK alone, 90 per cent of the island’s seagrass disappeared in the last century.
Douglas McCauley, an ecologist at the University of California, Santa Barbara tells Science that some restoration attempts “have seen lots of ups and downs”. “I can’t help but wonder how such efforts would fare with otters added back in those systems.”
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Photography courtesy of Unsplash.