Analysis of seagrass recovery at the Virginia Coast Reserve (VCR) Long Term Ecological Research (LTER) center. This work contributes a new experimental manipulation that compliments the ongoing long-term seagrass monitoring and restoration efforts within the VCR. The experiment also directly contributes to questions developed in the VCR-VII proposal related to state change and resilience.
- Climate change is impacting the VCR through sea-level rise, increased storms, and warming water temperatures. Heatwaves are a component of the warming phenomena and have been shown to negatively impact seagrass within the VCR. My research at the VCR investigates seagrass resilience (i.e., recovery) following disturbance.
- A marine heatwave (MHW) in June 2015 led to a ~90% dieback of seagrass within the central portion of the South Bay, VA seagrass meadow. Spatial patterns in eelgrass shoot density loss were not uniform as the meadow edge nearest the oceanic inlet had no evidence of shoot density or canopy cover loss. Recovery of the meadow interior, as indicated by aerial canopy cover imagery and annual summer shoot density counts, was complete 3-4 years following the MHW disturbance.
- This study seeks to address:
- is resilience greater (i.e., faster recovery) at sites with greater oceanic exchange (i.e., meadow edge) that have lower thermal stress?
- what are the mechanisms of recovery (i.e., clonal or seedling growth)?
- what is recovery trajectory shape (i.e., linear or non-linear)?
- In June 2020 I initiated an experimental disturbance of a seagrass ecosystem by removing above-ground seagrass in replicated, circular plots (6 meters in diameter) within the central and northern edge portions of the South Bay seagrass meadow.
- Broadly, the scale of this experimental manipulation is >2x larger in area than the next largest seagrass removal experiment. This broader areal scale of experimentation is significant as patterns and processes are often scale-dependent; what is observed and observable at one scale can change as the scale expands or contracts. The majority of prior experimental manipulations have occurred in ≤ 0.25 m2 plots that have likely overestimated the importance of lateral clonal growth during recovery as well as making it difficult to discern recovery patterns (e.g., linear vs. non-linear). Additionally, hydrodynamic conditions within small-scale disturbances are likely negligible however, this is likely not the case for larger-scale disturbances.
A quantitative literature synthesis of disturbance and recovery dynamics in seagrass ecosystems
Prior experimental and observational studies measured the aboveground recovery rate of seagrass following a disturbance event. These studies of disturbance/recovery dynamics are geographically extensive, occur in mono- and mixed beds, and across depth gradients. Despite the breadth of seagrass disturbance/recovery studies, there has been little cross-system examination of the resulting patterns or generalizations regarding the recovery of seagrass ecosystems.
Systematically review and synthesize the available english language primary literature on seagrass ecosystem disturbance and recovery to:
- summarise spatial scales of experimental and observational research on seagrass disturbance and recovery
- quantify seagrass recovery rates
- identify factors related to recovery to provide greater context for the experiment described above and to assess possible generalities about seagrass recovery