University of Central Florida Undergraduate Research Journal - Oyster Reef Restoration: Impacts on Infaunal Communities in a Shallow Water Estuary
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Discussion

With the global loss of oyster reef habitats, oyster reef restoration is vital to restoring ecosystem services, preventing economic losses, and providing habitat to important estuarine species (Beck et al. 2011).  Infaunal organisms are a key food source in this ecosystem for many commercial, recreational, and endangered species (Meyer and Townsend, 2000).  Based on the importance of infaunal organisms in the food web, infauna may also play an important role in habitat recovery after restoration and may be strong indicators of habitat productivity (Bell and Devlin 1983; Paynter and Rodney 2006).  Even so, few studies have examined the direct impacts of oyster reef restoration on infaunal communities.  This study focuses on the impact of oyster reef restoration on infaunal abundance and composition and documents the change to infaunal communities on restored oyster reefs in Mosquito Lagoon, Florida.

Infaunal abundance increased following restoration on restored oyster reefs, even with seasonal temporal changes taken into consideration.  This study supports the expectation that live reefs have high infaunal abundance; this expectation was made based on other studies of infaunal communities (Grabowski et al. 2005).  Following restoration, restored oyster reefs increased in infaunal abundance by about 230 organisms, a 90% increase in infauna.  One month after restoration, restored reefs became more similar to live reefs in terms of infaunal abundance.  These data support the hypothesis that restoration increases infaunal abundance and allows restored reefs to function more similarly to live reefs. 

A large primary food source is important to support larger species and a more complex trophic structure (Paynter and Rodney 2006).  With an increase in infaunal abundance, it is likely that restored reefs will be better able to support other estuarine species.  Many species of wading birds are known to depend on infauna as part of their diet, including the white ibis, sandpipers, plovers, gulls, and American oystercatchers (Kushlan and Kushlan 1975; Goss-Custard et al. 1977; Skagen and Oman 1996).  Increased infaunal abundance would give wading birds a larger food source and could allow restored oyster reefs to support more birds.   

Many of the infaunal families found on oyster reefs in Mosquito Lagoon are cited as important food sources for wading birds, such as the polychaete families: Nereididae, Spionidae, and Eunicidae (Figure 5); amphipod families: Gammaridae and Corophiidae; and bivalve family: Tellinidae (Goss-Custard et al. 1977; Goss-Custard et al. 1991; Skagen and Oman 1996).  These studies focus on birds in the Charadriiform order, including plovers, terns, oystercatchers, and sandpipers.  All of the listed infaunal families were found on restored reefs following restoration.  Nereididae and Gammaridae were some of the more common infaunal organisms on restored reefs and are most likely to contribute the most to wading bird diets on these reefs. 

A recent study on avian community structure and behavior in Mosquito Lagoon confirms the importance of restored oyster reef habitats in bird’s foraging behaviors.  Shaffer et al. (2019) found that wading bird’s foraging behavior was greatest on live and restored oyster reefs, with little foraging behavior observed on dead reefs.  This study suggests that restored oyster reefs, at least two years after restoration, are able to provide similar food sources and foraging opportunities as live reefs in Mosquito Lagoon.  It is likely that the demonstrated increase in infaunal abundance on restored reefs has a direct impact on the proportion of birds observed foraging on restored reefs.  This observation directly demonstrates that restoration allows restored reefs to provide necessary food sources and foraging grounds to wading birds in Mosquito Lagoon.

The largest increase in infaunal abundance on restored reefs occurred one month after restoration.  This increase in abundance is not wholly surprising as infaunal species are typically the first organisms to colonize oyster reefs after a disturbance like restoration (Bell and Devlin 1983).  This increase in abundance was expected to continue, yet, at the six-month collection period, there was a decrease in infaunal abundance across all reef types.  Based on other studies of infaunal communities, this decrease is most likely due to seasonal changes in infaunal communities.  The six-month samples were collected in January and other studies note a decrease in infaunal abundance corresponding with winter months (Zajac and Witlatch 1982).  Restored reefs had the smallest decrease in abundance at the six-month time period, only decreasing by an average of 50 organisms, although it is unclear if this has any correlation to the restoration efforts.

This study covers infaunal abundance up to six months after restoration.  This is a short time period compared to other food web studies of oyster reef restoration projects (Meyer and Townsend 2000; Paynter and Rodney 2006).  In this short time, however, there were positive impacts on infaunal communities on restored oyster reefs following restoration.  Six months after restoration, restored reefs were more productive with higher infaunal abundance than their non-restored, dead reef counterparts.  Given more time, restored reef infaunal communities may become increasingly similar to live reef communities. Restoration has also allowed restored oyster reefs to function as a foraging ground for important species of wading birds by providing a habitat to infaunal organisms that make up a large part of the birds’ diets.  At six months after restoration, oyster reef restoration has increased numerous infaunal species and shows a positive trajectory to support their associated food webs.

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