Submerged Aquatic Vegetation Restoration Research Findings

One of the SAV signs at Fountainbleau State Park.

Submerged aquatic vegetation (SAV) ecosystems support many desirable fish and wildlife species, improve water quality and provide shoreline stabilization – all while sequestering carbon in soils. Yet, SAVs are vulnerable to a litany of environmental changes, sea level rise and coastal development. Nowhere is that more apparent than in the Pontchartrain Basin.

With the goal of uncovering the best means of SAV restoration in the basin, Eva Hillmann, professor of biology at Southeastern Louisiana University, and her research team embarked on a two-year study funded by Louisiana Sea Grant – Seed to Seagrass: Planting and Seeding Re-Enforce Submerged Aquatic Vegetation Habitat Resiliency in the Pontchartrain Estuary. What they discovered is encouraging.

“The big takeaway is that after a year, survival rates in the three restoration sites studied were 25 to 35 percent,” said Hillmann. “That aligns with survival rates globally. So, we know we’re on the right path.”

“We also found that the restoration technique – transplanted bare root seedlings compared to hessian bag wrapped seedings – didn’t matter as much as which species was targeted. One species performed better each time in each area,” Hillmann added.

At each of the three restoration sites, two dominate SAV species were evaluated: the Chandeleur Islands, shoal grass (Halodule wrightii) vs. turtle grass (Thalassia testudinum); nearshore Lake Pontchartrain, widgeon grass (Ruppia maritima) vs. wild celery (Vallisneria americana); and Big Branch National Wildlife Refuge, wild celery vs. Eurasian milfoil (Myriophyllum spicatum). Shoal grass was the more resilient species at the Chandeleur Islands site. Wild celery fared the best at the other two sites.

Although the restoration technique wasn’t a factor in plant survival, seeding is less costly and less time consuming compared to hand transplanting SAVs – making it the preferred method for larger-scale restoration efforts. In greenhouse experiments, Hillmann’s team found that wrapping seeds in burlap with sediment appears to be the best approach. She hopes to field-test that premise in a future Sea Grant-funded project.

For the nature enthusiast interested in learning more about SAVs, educational signage has been installed at three locations – Fountainbleau State Park, Camp Salmen Nature Park and the Slidell Fishing Pier – that summarizes the importance of submerged aquatic vegetation with SAV specifics for that location. The signage, part of Hillmann’s Sea Grant project, also includes a QR code to even more material online.