Melissa Meléndez,
Department of Marine Sciences, University of Puerto Rico, Mayagüez Campus, Puerto Rico

Time and date: 15:30 – 16:30 pm, Friday Feb 3^rd
Venue: IMAS Sandy Bay seminar room

Abstract:
Seawater carbonate mineral saturation state is traditionally estimated from measurements of the carbonic acid system and an assumed calcium (Ca⁺²) concentration based on salinity. Due to diverse processes such as biogenic and abiogenic calcification, carbonate sediment dissolution or precipitation, and coastal processes, Ca⁺² behavior cannot be entirely conservative with respect to salinity. One well-known example is that of magnesium (Mg⁺²), co-precipitation with Ca⁺² which yields high-magnesium calcite thereby altering the Ca⁺²/Mg⁺² ratio and the ion activity product relative to Mg-calcite mineral phases. Direct determination of Ca⁺² and Mg⁺² can help in more accurate determination of calcium carbonate saturation state (Ω_CaCO3) of the meta-stable carbonate mineral phases and in the understanding of the carbon cycle and carbonate chemistry. By measuring not only the traditional parameters of the carbonate system (in our case pH and alkalinity) but also Ca⁺² and Mg⁺² concentrations, we intend to more accurately quantify Ω_CaCO3 with respect to aragonite and calcite, identify the carbonate mineral composition, and characterize the variability of the seawater Ca⁺²/Mg⁺² mineral ratio in the coral reef ecosystem of La Parguera Marine Reserve, Puerto Rico. To this end we are implementing a new method for high ionic strength solutions, such as seawater and sediment pore-waters, using High Performance Chelation Ion Chromatography (HPCIC). Since the HPCIC technique is based on metal ion complexation at the stationary phase, this separation technique is insensitive to the ionic strength of the sample and allows direct on-column injection of seawater resulting in a precision of 0.1% or better.

Corresponding author. E-mail address: melissa.melendezoyola@upr.edu (M. Meléndez)

Biography:
Melissa Meléndez is a graduate student finishing her master in Chemical Oceanography at the University of Puerto Rico, Mayagüez Campus, Marine Science Department, with Dr. Jorge Corredor. She has been studying the dynamics and controls on local carbonate chemistry within La Parguera Marine Reserve, Puerto Rico. Her main interest in the future aspiration is to study calcium and magnesium carbonate equilibria in coastal environments. As graduate student she have been part of the research group of the Pacific Marine Environmental Laboratory and the Caribbean Coastal Ocean Observing System (CariCOOs).  She had established the Puerto Rico Ocean Acidification Program, which provides carbonate chemistry data for La Parguera Marine Reserve online through the CariCoos website. She got her bachelor degree at the University of Puerto Rico in Environmental Science.  As undergrad she had the opportunity to participate in two NSF-Research Experience for Undergrads programs at Penn State University with Dr. David Eissenstat and in Bermuda Institute of Ocean Sciences (BIOS) with Dr. Andreas Andersson.