Distribution of the Non-Native, Hybrid Eelgrass in Kings Bay

Kings Bay is a 600-acre spring fed bay that is located at the headwaters of Crystal River in Citrus County, Florida. Habitat restoration efforts during 2015 to 2022 included annual plantings of eelgrass cultivars which were later suspected to be a non-native hybrid (Vallisneria spiralis x V. denseserrulata). By October 2022, estimated percent areal coverage of eelgrass in the bay had increased to 77%. However, following Hurricane Idalia in August 2023, estimated coverage abruptly declined to 10%. The objectives of this study were to determine the species composition of eelgrass in and around known planting locations and away from planting locations on the west side of the bay.

Eelgrass samples were collected in Kings Bay and genetically tested in October 2023 and April 2024. Non-native eelgrass occurred in 55 of 57 (97%) random samples collected within restoration areas, 40 of 47 (85%) random samples collected adjacent to restoration areas, and 28 of 82 (34%) random samples collected in the open bay. Non-native eelgrass was dominant in and around restoration areas, indicating establishment and substantial expansion within 200 m of planted locations during 1 to 8 years following restoration. Non-native eelgrass was less common in the open bay, indicating slower expansion rates into areas ranging from 200 to 1,300 meters from the planted locations. Native eelgrass was present in the open bay but was far less common in and around restoration areas. Additionally, morphological traits were recorded and compared with genetic results to identify characteristics that may be useful for field identification. The presence of lateral leaf pigment was associated with native eelgrass and the absence of lateral leaf pigment was associated with non-native eelgrass in Kings Bay. Additional sampling will be completed during 2024-2025 to monitor and evaluate the recovery of native and non-native eelgrass in Kings Bay.