The Living Dock: A Study of Benthic Recruitment to Oyster Substrates Affixed to a Dock in the Indian River Lagoon

Abstract

Benthic filter feeding organisms have the potential to improve local water quality by filtering microalgae and particulate matter out of the water column. A pilot project was conducted to test the concept of creating a Living Dock by growing these filter feeders at a dock in the Indian River Lagoon. Two different methods (mats and bags) were tested for their ability to recruit benthic organisms, as well as the efficacy of these methods for use as a long-term citizen science project. Eighteen oyster mats were wrapped around dock pilings, and 18 oyster bags were suspended between pilings of the same dock. After 1 year of immersion, healthy populations of barnacles, sponges, algae, bryozoans, mussels, and tunicates were found growing on both the bags and the mats. During that same time period, live oysters were also found growing on both mats and bags, with a maximum of 73 live oysters in one bag. Although the total percent cover of organisms settling on the shells did not differ between the mats or the bags, there was significantly greater organismal diversity in the bag treatment compared to the mat treatment. Bags were a more effective recruiter of benthic organisms, but longevity was an issue, with bags becoming heavily fouled and often breaking loose from the dock over time. It was noted that the mats with the higher shell densities saw greater recruitment and had greater diversity. Although the bags proved to be a better alternative than mats for the recruitment and growth of benthic organisms, they are not sustainable for use as a citizen science project. Future efforts should consider constructing mats with high-density shell counts, as the mats have more durability and are better suited for citizen scientists.