Quantifying The Impacts Of Oyster Reef Restoration On Oyster Coverage, Wave Attenuation And Seagrass Fragment Retention In Mosquito Lagoon, Florida

The goal of this project was to determine the effects of oyster reef restoration on oyster coverage, wave height dissipation and seagrass recruitment. First, to assess the current versus historical coverage of natural, dead and restored oyster reefs within Mosquito Lagoon, aerial photographs from 2009, provided by Saint Johns River Water Management District, were digitized using ArcGIS software. Live reefs, restored reefs and dead reefs were screen digitized using a reef ‘signature’ in order to estimate the area of each type of reef. The 2009 maps were used as a guide to digitizing the historical aerial photographs (1943, 1951, 1967, 1971, 1984, 1995, 2006). Dead reefs increased both in number and aerial extent during the study period (1943 – 2009), with 2009 having over 10 acres of dead reef coverage. Dead reefs were more likely to be found along major boating channels. Several dead reefs exhibited migration into the mangrove islands located landward of the 1943 footprint, with some dead reefs completely washing up into the shoreline. Restoration of dead reefs added 0.5 acres of live oysters to the Mosquito Lagoon area as of January 2009. Second, I examined how different oyster reef types (natural reef, restored reef, dead reef) reduced wave height. To determine wave height attenuation on each reef type, experiments were conducted in a 9 meter long wave tank using sensors that measured changes in wave height. For each reef type, replicate reefs were created in the wave tank. Shoreline sediment without oysters was used as a control. Using the wave generator, wave heights similar to Mosquito Lagoon boat wakes were created. Restored reefs reduced the incoming wave height by 25% compared to sediment without oysters. iii Lastly, I examined the potential link between oyster reef restoration and recruitment of seagrass fragments. Monthly surveys were performed to quantify the number of seagrass fragments encountering the three oyster reef types: dead reefs, natural reefs and restored reefs. The quantity of seagrass fragments was found to be similar on the three different reef types, but did show a significant trend of seasonality, which corresponds with the growing season of Halodule wrightii. Next, I tested retention of experimentally manipulated seagrass fragments on five natural and five restored reefs. Restored reefs retained seagrass fragments for significantly longer than natural reefs. I also measured seagrass fragment entanglement on each reef type inside the wave tank. I found that seagrass fragments were significantly more likely to become entangled and retained on restored reefs compared to dead and natural reefs. Overall, these metrics are important for determining the success of long-term oyster restoration project in Mosquito Lagoon, Florida. This project has found that oyster restoration is increasing the area of oyster habitat as well as providing important ecosystem services