Changes in Sediment Characteristics upon Oyster Reef Restoration, NE Florida, USA

Abstract

debated [11,12,14,15], but less research has been devoted to the effect of oyster reefs on the surrounding sediment. Reefs act to attenuate wave energy, possibly facilitating deposition of fine sediment [8]; this process may work in concert with oyster filtration to increase light penetration that may then shift ecosystems towards more benthic primary producers [6]. Finer particles and much higher organic matter (OM) content in oyster-associated sediments suggests a substantial role for carbon and nutrient removal by burial [8,17] and benthic algal uptake where light penetration is sufficient [6]. However, mesocosm experiments show that physical factors such as bottom shear can influence sediment resuspension and benthic micro-algal biomass, making the system more complex and the likelihood of OM burial versus remineralization more difficult to predict [7]. Several recent studies suggest that sediments associated with natural and restored oyster reefs have high rates of denitrification and may thus represent important sites for long term nitrogen removal [17][18][19][20]. Whole-creek studies and some mesocosm studies do not parse the contributions of the oysters themselves versus the associated sediments but rather consider the reef-sediment system as a whole [3,5,17]. Indeed, it is difficult to separate these effects because the presence of the reef will likely alter the depositional environment and ultimately the biogeochemistry of the surrounding sediment.

After Hurricanes Irma and Matthew: Living Shorelines Stabilize Sediments

“…25,36 Although we did not detect significant sediment changes behind the reefs, the oysters themselves were found to be partially buried in sediment before the storms. 35 In addition to storm surge during hurricane season, oyster reef sites along the Tolomato River are also exposed to frequent boat wakes and wind-driven waves. After the storms, the reefs were considerably damaged, and their dead shell was spread over a large area of shoreline (Figure 6b).…”

“…Recycled oyster shells were collected, put into plastic net bags, and placed in 5.3 m x 1.8 m x 0.5 m groups six meters apart along 315 m of the eastern shoreline of the Tolomato River. 35 Sediment cores (22 cm depth; 7 cm diameter) were collected with a push corer before and after the storms to compare the sediment profiles and determine if the sediment had become disturbed due to these storms. Before the storms, in June 2016, one sediment core was taken from behind/landward each of three oyster reefs (2,17,21) and at three control sites, where no reefs were present (Figure 1).…”

“…One year after their restoration, the fine sediment reached a volume of 0.36 m 3 behind the created reefs that were tested, compared to a fine sediment volume of 0.12 m 3 at the control sites. 35 The shift in particle size distribution in the surface depths indicated the created oyster reefs' ability to accumulate fine sediment and alter sediment profiles.…”

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“…Although we did not detect significant sediment changes behind the reefs, the oysters themselves were found to be partially buried in sediment before the storms. 35 In addition to storm surge during hurricane season, oyster reef sites along the Tolomato River are also exposed to frequent boat wakes and wind-driven waves. After the storms, the reefs were considerably damaged, and their dead shell was spread over a large area of shoreline (Figure 6b).…”

“…Recycled oyster shells were collected, put into plastic net bags, and placed in 5.3 m x 1.8 m x 0.5 m groups six meters apart along 315 m of the eastern shoreline of the Tolomato River 35. …”