SAV Recovery in the Susquehanna Flats

by Audrey Smylie

The Susquehanna River Flats, located at the mouth of the Chesapeake Bay’s largest tributary near Havre de Grace, Maryland, is home to the bay’s largest submerged aquatic vegetation (SAV) bed. Approaching 11,000 acres in 20231, this dense underwater habitat plays a pivotal role in supporting the health of the bay's tidal wetlands. SAV filters harmful nutrients and sediments from upstream sources and indirectly supports the resilience and productivity of wetlands across the Chesapeake Bay, which depend on clean water and stable shorelines to thrive. Although SAV populations in the Susquehanna Flats have been vulnerable over the past few decades, the overall resilience of this ecosystem is significant.

The recovery of SAV populations in the Susquehanna Flats after tropical storms such as Agnes (1972) and Lee (2011) is a testament to a combination of natural resilience and targeted interventions. Following these storms, which unleashed record-breaking sediment and nutrient flows that smothered grasses, scientists and conservationists implemented several key strategies to aid recovery. Efforts included monitoring water quality, reducing upstream nutrient and sediment loads through improved agricultural practices, and restoring buffers to prevent erosion2.

Additionally, seeding programs and transplanting SAV species were employed to kick-start regrowth in affected areas3. Beyond these direct interventions, the natural characteristics of the Susquehanna Flats have also contributed to the recovery. The Flats' shallow waters and strong tidal currents help flush excess sediments, allowing sunlight to penetrate and promote SAV growth. Recent research has also shown that submerged aquatic vegetation in the Susquehanna Flats plays a critical role in buffering pH levels in the Chesapeake Bay4. During the summer months, dense SAV beds facilitate high rates of photosynthesis, which not only increase oxygen levels but also elevates pH and carbonate mineral saturation states, promoting the formation of calcium carbonate (CaCO3) on plant surfaces. These carbonate particles are then transported downstream into deeper, oxygen-depleted waters, where their dissolution counteracts acidification caused by carbon dioxide (CO2) emissions and aerobic respiration. This natural pH-buffering mechanism highlights another essential function of SAV in sustaining the bays overall water quality and supporting a productive shellfish industry.

Recovery efforts in the Susquehanna Flats not only reinforces the ecological importance of SAV but also highlights its resilience. Healthier SAV beds now serve as natural filters, reducing sediment and nutrient loads and creating favorable conditions for tidal wetlands to thrive in the Chesapeake Bay. Tidal wetlands in the Chesapeake Bay are vital for biodiversity, acting as nurseries for aquatic species, providing habitat for birds, and serving as natural flood controls. As scientists continue to study the Flats’ resilience, their findings offer valuable insights into protecting and restoring SAV and wetlands throughout the bay.

Footnotes:

1. Underwater grasses in the Chesapeake Bay continue upward climb, Chesapeake Bay Program.

2. Susquehanna Flats (CB1TF2), Chesapeake Bay Program.

3. Scientists study mysterious invader in the Chesapeake Bay’s largest underwater grass bed, The Baltimore Sun.

4. Chesapeake Bay acidification buffered by spatially decoupled carbonate mineral cycling, Nature Geoscience.

Date: 2/11/2025 Category: News