When one hears the word reef, it is usually coral that comes to mind. These incredible animals provide homes and protection for numerous species, making them an essential element of many saltwater ecosystems. However, in brackish regions, such as Mosquito Lagoon, Florida, another species has a massive ecological role to play: oysters. Oyster reefs are large structures that form as oysters attach to one another, growing together. Walking along the shore, it is easy to miss these essential structures; one may spend an entire day along the coast unaware of the small creatures poking up from the sand beside them. Even upon noticing them, they may seem insignificant at first: a cluster of shells, rigid upon the rocky shore. But oyster reefs serve a variety of purposes, filtering water, providing protection for various fish and crustaceans, and acting as a buffer from storm surges. Although these reefs are important aspects of coastal environments, they are at risk of destruction from human activity, especially boating.
In the Mosquito Lagoon region, oyster reefs support a variety of bird species, such as ruddy turnstones and white ibises. Many of these birds, such as the roseate spoonbill and the Florida scrub jay, are threatened, and oyster reefs provide essential nesting and foraging opportunities. However, despite the key ecological role that these reefs play, they face various threats from human activity. Speedy boat rides along coastal regions may seem like a relatively harmless way to enjoy the watery views, but the reality is far grimmer: the wakes created by the sudden, fast movements of boats along the coast strike the oyster reefs, displacing large sections and creating tall piles of dead oysters. The oyster reef decline in Mosquito Lagoon has accelerated rapidly in recent decades, with a loss of over 240 reefs over a period of 66 years. However, in 2017, the University of Central Florida, with the help of the Coastal Conservation Alliance and the Marine Discovery Center, completed a restoration project to mitigate this damage. This project stabilized reefs and placed additional shells along the coast to promote new growth. While this change was undoubtedly positive for the oyster population, the wide-ranging impacts of restoration are not entirely known. A notable study by a team of researchers from the University of Central Florida has delved into the relationship between oyster reefs and coastal ecosystems to assess the project’s effectiveness, studying restored, living, and dead reefs along Mosquito Lagoon. In this paper, Jessica Copertino and her collaborators investigated the effectiveness of oyster reef restoration in supporting bird and benthic invertebrate populations. Benthic invertebrates—spineless creatures living in sediment at the bottom of bodies of water—can be essential food sources for birds and fish along the coasts. Thus, a potential increase in benthic invertebrate populations may signal more survival opportunities for birds in Mosquito Lagoon.
Copertino and her colleagues focused on 12 oyster reefs: 4 living reefs, 4 dead reefs, and 4 restored reefs. Shortly before the restoration, the team collected sediment samples and over the following three years, periodically collected additional samples. These samples were analyzed for benthic invertebrates and larger prey species. Every month, the researchers also visited each reef to conduct bird counts, focusing largely on bird behavior. The team measured both foraging (feeding) and loafing (non-breeding and non-feeding) behavior along the reefs. This allowed the researchers to gain a better understanding of how population dynamics changed over time after the 2017 restoration.
After an extensive data-collection and analysis process, the researchers were able to learn more about both the invertebrate and bird populations. Throughout the study period, the restored invertebrate populations overcame pre-restoration numbers and approached those of the living reefs. Furthermore, the diversity of invertebrate species living in restored reefs gradually changed, gaining a similar composition to the living reefs. While the dead reefs were simply shells of their former selves, the restored reefs became biodiverse havens for the many invertebrates of Mosquito Lagoon.
The restored reefs also had a large impact on the bird species in Mosquito Lagoon, as the researchers noted that loafing bird populations were similar in restored and living reefs. Birds such as the white ibis or roseate spoonbill will no longer have to search desperately for empty land to rest on after an intense period of flying and feeding. Copertino’s team also observed foraging on all three types of reefs, but the bird species that made up these feeding groups varied: living reef groups had similar compositions to restored reefs but differed from dead ones. The researchers did not detect a similar relationship for birds engaged in loafing behavior. Evidently, the various reefs of Mosquito Lagoon serve a myriad of purposes for the region’s birds and bolster the area’s diversity.
Oyster reefs provide many resources and services to a wide variety of organisms. From increasing invertebrate populations to supporting the behaviors of various bird species, their functions are essential for a healthy, diverse ecosystem. Copertino’s paper has demonstrated the importance of reef restoration, which has allowed these reefs to persist in a region that is heavily impacted by human activity. While oyster reefs may seem insignificant to many visitors and passerby, the Florida scrub jay and roseate spoonbill depend on the opportunities they provide. For these threatened birds, pressures such as climate change and habitat loss are dire problems with potentially fatal outcomes. But with further upkeep and more extensive restoration efforts, oyster reefs may be one shell of a solution.