Dayboat - Ocean Acidification: Controls on Reef pH

Ocean Acidification Project

Principal Investigator: Dr. Chris Martens, UNC Chapel Hill
Co-Principal Investigator: Dr.Niels Lindquist, UNC Chapel Hill
Training: July 6 — 9
Mission: July 13 — 22

Knowledge of the present and potential future threats of ocean acidification to coral reef ecosystems is critical to planning for their preservation and mitigating damage associated with global-scale pH changes. Can we accurately monitor pH and the carbonate system in coral reef environments? How can pH variability and changes in the carbonate system resulting from global-scale change be differentiated from higher frequency shifts resulting from local-scale processes occurring immediately adjacent to corals and other important calcifiers? Our research team, including marine chemists, coral reef ecologists, and physical oceanographers, is focused on obtaining accurate measures of how near-bottom benthic boundary layer (BBL) respiration processes interact with global ocean acidification to impact coral reef calcification rates. Focusing on the lower regions of the BBL where water quality parameters and chemical characteristics are dominated by local processes and slow diffusion rather than rapid advective mixing will be critical for understanding the impact of pH on calcification rates of corals because their recovery through the survival and growth of young recruits residing within the region of the BBL must occur from the bottom-up. Changes in the total dissolved inorganic carbon (ΣCO2), carbonate alkalinity (CA), CO2 fugacity (pCO2) and pH in the near-bottom BBL involves complex interactions of sources and sinks dominated by daily cycles of photosynthetic processes of benthic seaweeds and cynaobacteria versus the nearly constant, high respiration of sponges. Our new, Aquarius- or surface ship-tested instrumentation provides a unique opportunity to conduct in situ measurements of carbonate system and pH values with state-of-the-art precision. Knowledge of the in situ rates of benthic respiration processes and their impact on local pH has been virtually non-existent but is likely of substantial importance given the great abundance and biomass of sponges on Florida and Caribbean coral reefs and their high metabolic rates. In addition, the impacts of increasing macroalgal and cyanobacterial mat biomass needs to be investigated. Coral reef managers need to be aware of a distinction between pH changes associated with global-scale ocean acidification and local sponge- or algal mat mediated changes so as to implement effective strategies for mitigating impacts.

Oil Spill Monitoring Initiative

In addition to the NURC-funded Ocean Acidification project, we will initiate a hydrocarbon oil spill monitoring project at Aquarius Reef Base, utilizing the light hydrocarbon monitoring capabilities of both our underwater mass spectrometry and Seaguard multi-sensor platform systems. Our cabled underwater Membrane Inlet Mass Spectrometer, TETHYS, is the same instrument now in use in the northern Gulf of Mexico for oil plume detection. Our Seaguard platforms will be equipped with light hydrocarbon sensors used in our gas hydrate projects from the northern Gulf of Mexico and with a new Contros Non-Dispersive Infrared (NDIR) sensor on loan to us from a private German company.

Establishing Oil Spill Monitoring Capabilities at Aquarius Reef Base

Our initial plans for developing an oil spill monitoring capability are to document hydrocarbon concentrations in contaminated (from boating activities) local waterways and in the water column of the outer reef tract in order to establish background levels prior to the arrival of any materials from spills. A major part of the effort will be to establish the capabilities of existing Aquarius Reef Base (ARB) platforms including the Life Support Buoy (LSB) for Aquarius to enable a continuous monitoring capability in the coming years.