Climate-related diseases compromise the health of seagrass beds

In an oceanic harbinger for the intensifying effects of climate change, Cornell-led research shows seagrass beds – across vast expanses of intertidal grasslands in the Pacific Northwest – are suffering from a debilitating disease filled with lesions. . The once dynamic root systems of grasses are also deteriorating.

The research was published Nov. 10 in the journal Frontiers in Marine Science.

“Not only are we seeing more disease outbreaks devastating seagrass beds, but we are seeing a severe impact on the stores of vital nutrients of these plants in the roots – so they are compromised at the end of the growing season. preparing for a harsher winter, ”said co-lead author Olivia Graham, doctoral student in ecology and evolutionary biology.

The other lead author is Lillian R. Aoki, a former postdoctoral researcher in the Department of Ecology and Evolutionary Biology at the College of Agriculture and Life Sciences.

Eelgrass (Zostera marina) normally thrives in the San Juan Islands, Washington, on the Salish Sea along the Canadian border. In typical scenarios, Graham describes the seagrass environment as abundant underwater tropical forests, which clean the waters and support herring, salmon, perch, clams, mussels and oysters. Nearby, orcas feast on chinook salmon – the largest salmon in the Pacific – that live in these intertidal grasslands.

The herbarium dieback disease has been present for years, thanks to the warming of the waters due to climate change, which reinforces the sworn enemy of the disease Labyrinthula zosterae. This article confirms that below muddy beds, the roots of the plant are compromised.

In their research, Graham and Aoki tagged hundreds of plants at low tide and followed the fate of the prairie for several weeks. This “mark-and-recapture” method has shown that seagrass beds with pathological lesions grow more slowly and produce less storage sugars than their healthy counterparts.

“This answers a long-standing question about whether this disease causes real damage,” said lead author Drew harvell, professor emeritus in ecology and evolutionary biology, at CALS. “Unfortunately, that’s a resounding ‘yes’. “

Eelgrass plants propagate vegetatively, Harvell said, noting that eelgrass roots have huge systems where carbohydrates and sugars are made and stored, to expand their own lush networks.

“This document really nails it,” Harvell said. “The plants were tagged in the natural grassland and each was tracked over time. We’ve learned that injured plants have reduced starch stores and grow more slowly, so now we can say that the wasting disease is even more serious than you might think – and the harm goes far beyond the lesions.

In addition to Graham, Aoki, and Harvell, researchers on this article, “Effects of eelgrass dieback disease on eelgrass growth and subterranean sugar in natural grasslands, “were Carla P. Gomes, Professor at Cornell Ann S. Bowers College of Computing and Information Science and Director of Institute for IT Sustainability; Brendan Rappazzo, doctoral student in computer science; Sukanya Dayal ’19; Tiffany Stephens, Seagrove Kelp Co., Ketchikan, Alaska; and Joshua Stokes, undergraduate student at Southeast Missouri State University, Cape Girardeau, Missouri. The National Science Foundation provided the funding.

A related article from the Cornell team, “Warming sea surface temperatures fuel summer outbreaks of eelgrass wasting disease», Published Nov. 25 in the Marine Ecology Progress series, showed increasing levels of wasting eelgrass disease in the San Juan Islands, from 5% to 70% in 2013, then from 60% to 90% by 2017 Eelgrass shoot density decreased by 60% between 2013 and 2015 and did not recover. Additionally, work shows that disease prevalence correlated with warmer water temperatures for the month prior to sampling. The study shows increasing levels of disease at several sites in 2017.

Maya Groner of the US Geological Survey Western Fisheries Research Center, Seattle, led the study; Harvell and Gomes were the principal authors. Authors also included Morgan Eisenlord, doctoral student in ecology and evolutionary biology; Graham, Rappazzo, as well as several CORALS alumni, Cornell Ocean Research Apprenticeship for Lynch Scholars (CALS) students, who are Reyn M. Yoshioki ’14, University of Oregon; Evan A. Fiorenza ’17, University of California, Irvine; Phoebe D. Dawkins ’16, University of California, Irvine; Miranda Winningham ’17, marine biologist; Alex Vompe ’19, Oregon State University; and Natalie D. Rivlin ’13, at the University of British Columbia.

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