Sponges dramatically alter ecosystem water quality through the combination of extraordinary pumping rates and rapid, dynamic biogeochemical transformations. Sponge communities are ubiquitous in marine environments and can inhabit over 40% of the benthic area in tropical ecosystems.
In this project, a research team from the University of North Carolina at Chapel Hill, the University of Hawaii at Manoa, and the University of Washington will continue their ongoing investigations of the importance of sponge nitrogen (N) transformations and fluxes in coastal environments through quantifying their role in the N cycle of Florida Bay, specifically the importance of these dominant benthic organisms in meeting the N demands of primary producers throughout the Bay. The team's previous research demonstrated that sponge dissolved inorganic nitrogen (DIN) flux to overlying waters at Conch Reef, Florida Keys, was larger than any other benthic nitrogen (N) source. In choosing Florida Bay as their study area, the team will benefit from the wealth of available data concerning N sources and recycling, including estimated values for new N inputs, and quantitative sponge benthic biomass. By performing in situ sponge N flux measurements they expect be able to contribute information about a potentially important recycled N source that has not previously been quantified in N budgets.
The overarching goal of this research is to establish the importance of sponge-mediated N cycling processes in Florida Bay where sponges are abundant, their biomass has been quantified at hundreds of stations and their key role in water filtration has been established, by quantifying rates and mechanisms of transformations of both dissolved and particulate organic nitrogen to DIN and N2 (nitrogen gas) by key sponge species, and elucidating controls on N2 production by natural factors such as sponge tissue dissolved oxygen concentrations.
Broader Impacts: Sponges play a crucial role in the nutrient balance of coastal environments because they are abundant in tropical, temperate and polar habitats, they process tremendous volumes of water, and many common species host abundant and active microbial populations. Their impact on biogeochemical cycling in most environments, however, remains largely unknown. During this study, graduate and undergraduate students and a postdoctoral fellow will learn in both laboratory and field settings a spectrum of state-of-the-art techniques and instrumentation firsthand and, when the results are ultimately synthesized for publication, they will benefit from participation in the exchange of ideas with established researchers from diverse fields.
Coastal ecosystems worldwide contribute substantial direct economic benefits (e.g., fisheries and tourism) and provide important ecosystems services. However, they are being increasingly stressed such that many of these systems no longer resemble their more pristine states and likely have radically altered nitrogen cycles. Nitrogen cycles of coastal ecosystems are of particular interest because levels of this fertilizer typically underpin their health. Sponges dramatically alter marine ecosystem water quality through the combination of extraordinarily high pumping rates and rapid, dynamic nitrogen transformations. These nitrogen transformations are maintained by an active and abundant microbial community living within the tissues of sponges. The microbial community can perform various nitrogen transformations, such as nitrification (conversion of ammonia to nitrate), nitrogen fixation (conversion of N2 gas to organic nitrogen) and even N2 production (the conversion of bioavailable nitrate to N2 gas). Sponges process tremendous volumes of water (e.g., www.youtube.com/watch?v=bf0CoQDW9oA), pumping 50,000 to 100,000 times their own volume in a day depending on the species, which can translate into a sponge community being able to circulate the entire overlying water column in days. Sponge communities are ubiquitous in marine environments and can inhabit over 40% of the sea floor in tropical ecosystems. However, the impact of sponges and their microbial community on coastal ecosystems remains largely unknown. Our previous research demonstrated that the bioavailable nitrogen release by sponges to overlying waters at Conch Reef, Florida Keys, was larger than any other nitrogen source on the sea floor. The primary goal of this research has been to quantify the importance of nitrogen transformations in sponges and the release of that nitrogen in coastal environments in Florida Bay, FL and Kaneohe Bay, HI. Our research combined the expertise and talents of marine ecologists, chemists and physical oceanographers to examine nutrient element and chemical cycling for a wide variety of coral reef sponges that differed in basic biological characteristics, such as the presence or absence of large, internally hosted populations of diverse microorganism that control the potential chemical transformations occurring within sponges. Our field assays examined how chemicals in seawater exhaled by sponges affect the growth, health and survival of neighboring corals and algae including seaweeds. Because sponges are a major component of sea floor communities in diverse tropical, temperate and polar marine habitats, a quantitative understanding of important chemical processes occurring within sponges and nutrient chemicals released by sponges and their surrounding communities are crucial for defining their roles in regulating the quality of critical marine habitats, such as coral reefs. Our findings from this research project have already been published in peer-reviewed scientific papers and several more peer-reviewed scientific papers have been recently submitted and are currently undergoing peer-review plus others are in the final stages of preparation for publication. We have presented various aspects of this research at national and international conferences and workshops and results have been disseminated through the world-wide web. Graduate and undergraduate students and a postdoctoral fellow have learned in both laboratory and field settings a spectrum of state-of-the-art techniques and instrumentation. This research directly supported the thesis research of two Ph.D. students (one at University of North Carolina-Chapel Hill and the other at the University of Hawaii). We have been a leader in study of the role of sponges in nutrient cycling in coastal environments.