Biodiversity on oyster reefs includes organisms that affect oysters as their food, predators, parasites, and competitors. The organisms present and their interactions with oysters may differ on aquaculture leases and restored sanctuary reefs. This study takes an enhanced perspective on biodiversity and oyster health by comparing the species detected on aquaculture leases and restored sanctuary reefs at three timepoints that are critical for the oyster life cycle: the spring phytoplankton bloom, the summer reproductive window, and the fall spike in Perkinsus parasitic infections. The aim is to identify species linked to oyster health and improve the understanding of ecosystems supported by oyster aquaculture and restoration.
We sampled 11 reefs across two rivers in spring, summer, and fall of 2024 and used salinity, temperature, dissolved oxygen, turbidity and chlorophyll to characterize environmental conditions. We leveraged a variety of biodiversity metrics to capture diverse taxa. First, environmental DNA (“eDNA”) was extracted from water and sediment to identify animals through the DNA they shed into the environment and is effective for rare or microscopic organisms. Second, we deployed settlement tiles for approximately 30 days at each timepoint to track small fouling organisms that compete with oysters for space and food. Finally, GoPro videos and audio recordings target mobile organisms, such as fish, jellyfish, and crustaceans. Oysters were diagnosed for Perkinsus marinus infection and scored for body condition to assess how oyster health is linked to biodiversity.
Aquaculture leases and restoration reefs had distinct biodiversity as estimated by audio profiles based on eight unique sounds (Figure 1). Audio from oyster toadfish was only consistently present on restoration reefs, while non-reef control sites had the lowest sound diversity. Sediment tiles showed differences in small fouling organisms across rivers and timepoints. Restoration reefs had more oysters and more complex habitat than aquaculture leases, but also greater disease impacts. Sequencing of eDNA from water and sediment will yield further insights into biodiversity profiles and linkages with oyster health, indicating species that merit increased attention in managing oyster aquaculture and restoration.