The Role of Marine Sponges in Carbon and Nitrogen Cycles of Coral Reef and Nearshore Environments

Hoer, Daniel

The Role of Marine Sponges in Carbon and Nitrogen Cycles of Coral Reef and Nearshore Environments Public Deposited

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March 19, 2019

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Hoer, Daniel
- Affiliation: College of Arts and Sciences, Department of Marine Sciences

Abstract

Sponges and their microbial consortia can alter the water quality of the surrounding environment through animal and hosted microbial chemical transformations resulting from their dynamic pumping, water filtration, and respiration processes. The goal of this dissertation was to quantify the role of these organisms in the cycles of carbon (C) and nitrogen (N) on reefs and representative environments of Florida Bay and describes five principle findings: 1) the abundant coral reef sponge Xestospongia muta satisfies the bulk of its respiration oxygen (O2) demand through uptake of dissolved organic carbon, and this species removed C in excess of O2 demand which is presumed to be reserved for cellular maintenance, growth, and the generation of reproductive materials. 2) Respiration activities in this species yielded a tremendous flux of dissolved inorganic nitrogen (DIN), and the rate of this N release appeared to be broadly conserved between Floridian and Bahamian reefs. 3) The magnitude and speciation of exhalent DIN from species tested in Florida Bay showed similar rates of N efflux as those on the reef, yet the remineralization of particulate organic matter appears to be the dominant feedstock for the observed N release. 4) The N released from these species represented a dominant source of N to a budget calculated for an offshore basin in Florida Bay (Mystery Basin). 5) Bloom conditions swept through Mystery Basin decimating sponge populations and water column N, and yielded significant and lasting changes to the chemical and ecological structure of the system. These results indicated that sponges have the capacity to alter local water quality through the observed C and N transformations mediated by the holobiont (sponge and associated microbiome), and further suggests that they can drastically impact ecosystems where their populations dominate.

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