Award: OCE-1756907

The molecule, dimethylsulfoniopropionate (DMSP), is produced in copious quantities by marine algae, wherein it can comprise an unusually high amount of carbon - up to 20% - in several algal species. An important transformation of DMSP is its enzymatic cleavage to form the gas dimethylsulfide (DMS). Some DMS escapes to the atmosphere wherein it affects cloud formation and climate. To better understand this ocean-atmosphere coupling, marine DMSP and DMS cycling have been studied extensively. However, little is known about acrylate concentrations, fluxes, or impacts in the oceans, even though acrylate is produced in equal quantities to DMS when DMSP is enzymatically cleaved to DMS. Acrylates concentrations and fluxes should at times be substantial, especially in shallow-water coral reefs or during blooms of DMSP-rich phytoplankton that are common throughout the world's oceans and sometimes harmful or toxic. It is not known why marine algae produce acrylate, even as a by-product, since it is generally considered to be toxic. Unlike DMSP or DMS, acrylate is chemically reactive. Indeed, acrylate is used in industry to convert small molecules into much larger molecules (polymers) that are of synthetic value (e.g., carpet fibers); there is evidence for acrylates polymerizing role in marine ecosystems as well. Despite its reactivity and toxicity, acrylate is consumed by marine bacteria as food. Thus, acrylate is a reactive form of marine organic matter that may have important impacts on the carbon cycle and ecology of the upper ocean. A study was undertaken to garner fundamental information about the marine acrylate cycle. The main goals were to (1) study the effects of sunlight on the formation (photoproduction) and loss (photolysis) of acrylate in seawater, and (2) determine if photoproduction and photolysis are important pathways in the marine acrylate cycle relative to its biological production and consumption in a coral reef. We first determined the absorption spectrum of acrylate in water, which surprisingly had never been reported in the scientific literature, but which is nonetheless critical to understanding its chemistry and reactivity in water. Second, we discovered a new molecule, dimethylsulfoxonium propionate (DMSOP), which is a previously unrecognized abundant marine organosulfur compound that is produced and used by marine organisms with proposed important roles in oxidative stress protection, marine microbial food web dynamics, and global carbon and sulfur cycling. Third, we determined that acrylate does not undergo photolysis in seawater as previously reported, but rather is produced through sunlight-driven reactions of marine organic matter. This process is driven by solar ultraviolet radiation and the rate of production is wavelength and temperature dependent. Fourth, we determined acrylate is produced by DMSP-containing marine algae in large quantities including the symbiotic algae associated with reef-building corals. Acrylate can constitute a significant proportion of the total carbon in the coral symbionts algal cellnot as much as DMSP but nonetheless well above what would be expected for a compound that is considered to be toxic. Corals are the main source of acrylate and DMSP to the coral reef, but unlike DMSP much of the acrylate is released by the coral into the dissolved phase. Unexpectedly, we observed a large day night (diel) cycle for the biological production and removal of dissolved acrylate. Together, these findings indicate that (1) acrylate is an important food source in the coral-reef ecosystem, and (2) coral production and microbial consumption of acrylate are quite rapid, much faster than all other acrylate processes in the coral reef. Through this research, we discovered a new pathway for acrylate formation in the oceans and a novel molecule DMSOP; we also addressed significant information gaps and generated results that led to an improved understanding of acrylate cycling in seawater and its impact on the marine carbon and organosulfur cycles. DMS, DMSP, and acrylate are central components in the ecology of the oceans, particularly during massive blooms of DMSP-rich algae that are common worldwide, making them potential keystone compounds to gauge the oceans response to global changes in climate, UV, and other factors of immediate societal relevance. Major findings are reported in one Ph.D. dissertation and seven research papers and one refereed review chapter. Data generated from this project are archived with the Biological and Chemical Oceanography Data Management Office or reported in the scientific publications. More than fifteen talks and posters were presented at scientific meetings. This project contributed to the education of two Ph.D. students, and the professional development of a postdoctoral investigator and four undergraduates. This project also fostered disciplinary and interdisciplinary research and educational collaborations for the students and postdoctoral investigator with four other academic institutions (University of South Alabama; University of Buffalo; Friedrich-Schiller-Universitt, Germany; Institut de Cincies del Mar, CSIC, Spain). Last Modified: 05/03/2024 Submitted by: DavidJKieber