Larval settlement, Oyster reef, Recruitment, Restoration


Productivity, diversity and survival of estuaries are threatened by explosive coastal population growth and associated recreational activities. One major area of recreational growth has been the number of small pleasure craft motoring in shallow waters at high speeds. On the east coast of Central Florida in the Indian River Lagoon system, intense boating activity occurs year-round and intertidal reefs of the eastern oyster Crassostrea virginica with dead margins (piles of disarticulated shells) on their seaward edges are commonly found adjacent to major boating channels. The cause(s) of the dead margins is unclear. However, the disarticulated shells may be reducing reef sustainability if these surfaces are unavailable for larvae. Recruitment trials were run on eight reefs (4 with dead margins, 4 without) in three 8-week trials in 2001/2002. Significant differences were found for location on reef and season. For survival of recruits, significant differences were found for reef type, location on reef, and season. Sediment loads, percent silt/clay, and relative water motion were all found to be significantly higher on impacted reefs. Spring months were found to be the optimal time for larval recruitment to increase larval set and survival and to also decrease the effects of sedimentation and water motion. Based on these results, experimental restoration began May 2003 to develop an ecologically and economically feasible restoration protocol for this intertidal region. Four different densities of shells (0, 16, 25, 36) were attached to vexar mesh mats (45 X 45 cm) displaying shells perpendicular to the substrate. 360 mats were randomly deployed at one of six dentified optimum recruitment locations. Recruitment increased through June and was significantly higher on mats with 36 shells. This was followed by a large, expected decline in recruitment and survival in July/August, due to competition, predation and/or extreme high temperatures. Total live oysters on the restoration mats significantly increased during October 2003 through February 2003. These newly-created oyster reefs are moveable and provide optimal substrate and larval set to be transported post-recruitment to areas resource managers have slated for restoration to aid in reef sustainability. To determine the potential negative effects of flow and sediment levels on oyster larval settlement, which may be associated with an increase in boating actitivity, laboratory experiments were conducted. Eighteen trials, with competent oyster larvae, nine in flowing-water and nine in still-water were run at three sediment levels: no sediment, low sediment, and high sediment loads. Larval settlement was significantly higher in the still-water trials and both high and low sediment loads significantly reduced larval settlement.


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Graduation Date





Walters, Linda J.


Master of Science (M.S.)


College of Arts and Sciences



Degree Program









Release Date

August 2004

Length of Campus-only Access


Access Status

Masters Thesis (Open Access)


Arts and Sciences -- Dissertations, Academic; Dissertations, Academic -- Arts and Sciences

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Biology Commons