While out in the field, Foster and her coauthor, Jane Watson, a biologist at Vancouver Island University in British Columbia, would frequently notice hundreds of little pits dotting the seafloor, creating bald spots in the otherwise dense eelgrass meadow. These gaps in the vegetation were the work of sea otters. While hunting for food, the sea otters were inadvertently digging up the eelgrass.<\/p>\n
Watson had a hunch that by digging these pits, sea otters were shaping the meadow in an important way. Undisturbed, eelgrass primarily reproduces by cloning itself via rootlike rhizomes that sprout into new, genetically identical plants. While between roughly five and 10 percent of eelgrass shoots do flower and reproduce sexually, the resulting seedlings are often unable to compete with clones. It\u2019s not uncommon to see a meadow made up entirely or almost entirely of genetically identical eelgrass, Foster says. Disturbance\u2014such as a particularly forceful tide or a hungry sea otter tearing at eelgrass rhizomes\u2014forces eelgrass to flower at a much higher rate. New seedlings settle in the newly established gaps in the vegetation, and the meadow becomes more genetically diverse. Foster, Watson, and their colleagues wanted to know whether the sea otters were causing the eelgrass to shuffle its genes.<\/p>\n
![\"pit](\"https:\/\/hakaimagazine.com\/wp-content\/uploads\/otter-pit-sea-otter-eelgrass-1200x675.jpg\")
<\/a>Pits dug by sea otters disturb eelgrass rhizomes, which spurs sexual reproduction of the eelgrass plants. Photo courtesy of the Hakai Institute<\/p><\/div>\n
A century ago, the maritime fur trade largely wiped out sea otter populations along the west coast of North America. Reintroduction from the remaining pocket populations and rehabilitation efforts, as well as bans on hunting mean that sea otters have been able to rebound in some areas<\/a>. The variability in sea otters\u2019 growing populations gave the scientists a way to test their hypothesis. They collected eelgrass shoots from 15 different sites, six of which had been home to sea otters for at least 20 to 30 years, and three for less than 10 years. They also looked at six sites that had no sea otters and served as a control. The team highlighted 13 sections of eelgrass DNA, and analyzed how many varieties of each section they saw at each site.<\/p>\n The contrast was stark: eelgrass\u2019s genetic diversity at sites with long-established otter populations was up to 30 percent higher than at the sites without sea otters and those where the sea otters\u2019 populations had only recently begun to rebuild.<\/p>\n Brent Hughes, a biologist at Sonoma State University in California who was not involved in this study, has spent much of his career studying how sea otters physically restructure their ecosystems. For him, the central question of the paper was revolutionary. \u201cThis is a whole new lens,\u201d Hughes says. \u201cSea otters are restructuring the genetics of the whole system.\u201d<\/p>\n This finding has important implications for the future of eelgrass in a rapidly changing world in which it\u2019s threatened by warming waters<\/a>, pollution<\/a>, and disease<\/a> throughout its range. \u201cIf the one clone that spreads is weakened by disease or a grazer or pollution then the whole area is vulnerable,\u201d says Mary O\u2019Connor, an ecologist researching eelgrass at the University of British Columbia who was also not involved in the study. Genetic diversity ups the odds that at least one patch of grass will survive these stressors.<\/p>\n
![\"Erin](\"https:\/\/hakaimagazine.com\/wp-content\/uploads\/jane-erin-sea-otter-eelgrass-900x1239.jpg\")
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