Research discovery a pearl of hope for imperiled oyster reefs

Date:
April 5, 2022
Source:
University of Virginia
Summary:
Despite a greater than 85% population loss worldwide due to
overharvesting, collaborative research shows oyster reefs can
rebound through restorative efforts.



FULL STORY ========================================================================== University of Virginia researchers, in partnership with The Nature
Conservancy, are sharing the good news that the future of oyster reefs,
which have experienced greater than 85% loss worldwide over the past
two centuries, doesn't have to be bleak.


========================================================================== Their 15-year study, published Tuesday, demonstrates that restored reefs
can match natural reef oyster populations in about six years and continue
to hold strong thereafter.

"Our study shows that restoration can catalyze rapid recovery of an
imperiled coastal habitat and help reverse decades of degradation,"
said the study's lead author, Rachel Smith, a postdoctoral researcher
in the Department of Environmental Sciences at UVA.

Oyster reefs are aggregate coastal formations built by the hinge-shelled mollusks. The reefs form along sand bars and muddy tidal flats, molding
to contours at water's edge and serving as a bulwark against erosion. As
sea levels rise, so do the reefs -- if they are healthy.

Due to over-harvesting and oyster diseases, however, the reefs have
been in decline. In fact, many wild populations are now considered "functionally extinct" because of severe habitat losses.

At 16 sites in coastal Virginia, composed of 70 reefs, the researchers
studied the Crassostrea virginica variety of oyster, which, despite
sounding perhaps like a Virginia native exclusive to the state, is better
known as "the Eastern oyster" or "the Atlantic oyster." Vitally important
to the seafood economy, it is the common variety found on the Eastern
Seaboard, and in Canada and South America as well -- though it's less
common today. European colonization and subsequent commercial appetites
reduced the oysters to about 1% of their estimated historical abundance
along the Chesapeake Bay and its tributaries.



========================================================================== Where the reefs were spared or have recovered, waters are clearer and
cleaner.

The "filter feeders," like other oysters and bivalve mollusks, suck
in surrounding water, consuming plankton and any silt and debris, then
eject the water back out, free of impurities. Scientists note the added
value of oysters as a form environmental remediation, often mitigating
the impact of fertilizer seepage or accidental spills. Oyster reefs also provide habitat for crabs and fish, supporting coastal fisheries.

So, can refurbished reefs return these oyster habitats to their former
glory, restoring the benefits that go along with their presence? While
the odds now seem more favorable, until recently, the waters had been
murky in that regard as well.

Since the 1990s, conservationists and government agencies have been
restoring reefs by recycling oyster and clam shells provided by natural deposits, aquaculture -- farms for aquatic lifeforms -- and restaurant discards; the shells are used to form the substrate for the reefs. These projects, sometimes led by local volunteers, then nudge oyster development
by laying out beds for "baby" oysters to take hold. Yet the disparate
efforts have been hard to track and compare in the methodical way
scientists find useful. When researchers have led efforts, their studies
have usually been for two years or less, and often failing to measure comparable natural reference sites.

"In the past, answering this question has been hampered by unknown
timelines for recovery, undefined benchmarks for success and uncertainty
about whether restored ecosystems can match natural ones," said study
coauthor Max Castorani, an assistant professor in the Department of Environmental Sciences. "Although preventing habitat loss should be the
first priority, our new findings show that restored oyster reefs can
catch up within a decade." Smith and Castorani worked with scientist
Bo Lusk at The Nature Conservancy, which has been restoring oyster reefs
in Virginia's coastal bays since 2003.

They culled bushels of empirical evidence, documenting the relatively
quick rebound of not only the oysters, but also small crabs on the reefs
that help support the broader food web.

"We also learned that as restored reefs matured and gained oysters,
they became more stable over time, which suggests that restoration can
increase ecosystem resilience," Smith added.

The scientists conducted their experiment at the National Science
Foundation's Virginia Coast Reserve Long-Term Ecological Research
site. The foundation supports dozens of sites around the world to study ecosystem changes over many years to decades, to predict how they will
look in the future.


========================================================================== Story Source: Materials provided by University_of_Virginia. Original
written by Eric Williamson. Note: Content may be edited for style
and length.


========================================================================== Journal Reference:
1. Rachel S. Smith, Bo Lusk, Max C. N. Castorani. Restored oyster reefs
match multiple functions of natural reefs within a
decade. Conservation Letters, 2022; DOI: 10.1111/conl.12883 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/04/220405123913.htm

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