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A Resilient Seagrass Species Could Help Reshape Coastal Restoration

Ruppia maritima, a relatively uncommon native seagrass in Florida's Indian River Lagoon.

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Seagrasses are among the most important foundation species in coastal ecosystems, providing habitat for marine life, stabilizing sediments and helping improve water quality. Yet nearly 20% of the world’s historic seagrass cover has been lost, and efforts to restore these vital underwater meadows often face significant challenges.

In Florida’s Indian River Lagoon (IRL), widespread seagrass losses following harmful algal blooms have left many areas with little natural recovery. Now, researchers from ����ֱ��’s Harbor Branch Oceanographic Institute have identified a resilient native seagrass species that could offer a new approach to restoring degraded estuarine habitats.

The study, published in , provides new insight into the life history and potential restoration applications of Ruppia maritima, a relatively uncommon seagrass in the IRL that has persisted in some of the lagoon’s most environmentally altered areas, including mosquito impoundments that can be especially challenging to seagrass while also offering a promising study environment.

They are hydrologically altered wetlands separated from the lagoon by dikes and water-control structures. Seasonal reconnection through Rotational Impoundment Management creates fluctuating water levels and water quality, making these systems challenging environments for seagrasses. At the same time, they offer a unique setting to study how R. maritima withstands repeated disturbance and what makes the species potentially valuable for restoration.

To investigate, researchers followed R. maritima from the field to the laboratory and nursery. Over three years, they monitored naturally occurring populations at two sites within Bee Gum Point Nature Preserve, tracking seasonal changes in seagrass coverage, biomass and environmental conditions. They also examined the sediment seed bank and conducted laboratory experiments to determine which conditions trigger seed germination.

In addition, plants collected from the preserve were transplanted into aquaculture tanks at the ����ֱ��Harbor Branch Seagrass Nursery to evaluate their growth, reproduction and potential for nursery cultivation.

Results revealed that R. maritima follows a distinctive annual life cycle, growing primarily from late winter through spring, flowering and then dying back during summer. Despite seasonal flooding and deteriorating water quality, the population returned year after year.

Researchers found the key beneath the sediment: a persistent seed bank that survived unfavorable conditions and regenerated when conditions improved, with laboratory experiments showing that lower salinity, particularly freshwater exposure, strongly stimulated germination.

“Ruppia maritima has a remarkable ability to persist through disturbance,” said Rachel Brewton, Ph.D., senior author and an assistant research professor at ����ֱ��Harbor Branch. “Even when the plants disappear above ground, the population can persist as a seedbank in the sediment, waiting for conditions to become favorable.”

The species demonstrated similar resilience in cultivation. Transplanted R. maritima was successfully established in aquaculture tanks at FAU’s seagrass nursery, following a seasonal growth pattern similar to the wild population and producing viable seeds. Most notably, the cultivated population has remained self-sustaining in the nursery since its establishment in 2021.

“That ability to regenerate from a persistent seed bank, combined with its successful cultivation in our seagrass nursery, is what makes this species particularly interesting from a restoration perspective,” said Richard Mulroy, study co-author and biological scientist at ����ֱ��Harbor Branch.

The results suggest that R. maritima may serve as a useful pioneer species in IRL restoration – one capable of rapidly colonizing bare or disturbed areas and potentially helping create conditions for broader seagrass recovery.

“Rather than simply replacing established seagrass communities, we see potential for Ruppia maritima to help initiate recovery in places where habitat has been lost,” said Deanna Webber, primary study author and research coordinator at ����ֱ��Harbor Branch. “Its ability to come back from seed after periods of environmental stress suggests it may be useful for disturbed systems where conditions are not always predictable.”

The findings also support further exploration of seed-based restoration as a potentially useful strategy. During laboratory trials, R. maritima seeds remained viable during prolonged exposure to high salinity and germinated after freshwater exposure, suggesting that seeds could potentially be collected, stored and propagated before being introduced into restoration sites.

The next step is field testing to determine where and how R. maritima performs best. Researchers will evaluate aquaculture-derived plants and seed-based approaches under natural conditions and identify the environmental conditions, planting methods and restoration goals for which the species provides the greatest benefit.

“The goal of restoration is not simply to put seagrass back – it is to create the conditions for a functioning ecosystem to recover,” Brewton said. “If future field trials confirm what we are seeing in the laboratory, nursery and natural populations, Ruppia maritima could give restoration practitioners another tool for rebuilding seagrass habitat in the Indian River Lagoon and potentially other disturbed estuaries around the world.”

Study co-authors are Patrick H. Monaghan, biological scientist; David C. Heuberger, biological scientist; and the late M. Dennis Hanisak, Ph.D., research professor, all with ����ֱ��Harbor Branch.  

This research is dedicated to the memory of Hanisak and was supported by the U.S Fish and Wildlife Service’s Coastal Program with matching support from the Indian River Land Trust.

-FAU-

Tags: research | harbor branch | environmental coastal and ocean sustainability | faculty and staff