Seagrass success goes beyond the lagoons

Sometimes doing good is worth the effort – and hopefully can provide a blueprint for others.

A 20-year commitment by US scientists and supporters to reverse habitat degradation in Virginia’s coastal lagoons already is recognised as a success story, with more than 3600 hectares of native eelgrass (Zostera marina) restored in four bays.

Now, a long-term monitoring study, published in the journal Science Advances, shows that the success extends far beyond seagrass.

Populations of silver perch, scallops and other fauna have increased rapidly in the area, turbidity levels have decreased, indicating healthier water, and carbon and nitrogen stocks sequestered in mature seagrass sediments are 30% and 120% higher, respectively, than in newly colonised sediments.

A nearby restoration program for bay scallops, which rely on the seagrass habitat to settle on as juvenile recruits, also appears to have prospered, with wild population inhabiting the seagrass beds.

“As the world settles into the era of the Anthropocene, and regulatory agencies worldwide seek to conserve and recover valuable ecosystem services, our study provides a positive example that successful marine restorations are possible on the scales that contribute directly to human well-being,” the authors write.

201008 seagrass
Credit: Jay Fleming

Just as importantly, adds lead researcher Robert Orth, from Virginia Institute of Marine Science, it provides a better definition of what constitutes success.

“Traditional metrics have focussed on habitat attributes such as plant biomass, coverage, or density,” he says, “but the ultimate motivation is often not to restore the habitat itself, but the services it provides, benefits such as enhanced water quality, fisheries production, and now, carbon storage.”

Orth was co-author on a 2017 paper describing similar seagrass research in Australia’s Cockburn Sound. That project was led by the University of Western Australia.

In Virginia, the work began back in 2001, and the researchers and citizen volunteers have since spent 3500 hours gathering then dispersing 74.5 million eelgrass seeds in 536 plots covering 213 hectares.

Continued seeding has helped the nascent meadows survive the natural ups and downs experienced by coastal ecosystems.

Though the restoration is far from complete – eelgrass currently occupies about 28% of its estimated historical distribution in the lagoons – the authors suggest that the results reveal a speed and scale of restoration rarely observed in marine ecology.

They did have some things going for them, notably the project’s location within the 16,000-hectare Virginia Coast Reserve, strong community support and the fact that natural recovery was precluded not by degraded environmental conditions but by a lack of seeds.

Nevertheless, Orth says, success “required a strong understanding of the causes of decline, repeated assessment of best restoration practices, and a sustained commitment to long-term monitoring and research”.

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