Carbon recycling at the seafloor: Understanding processes through pore-water dissolved organic matter-November 21st

Tomoko Komada, San Francisco State University

Moss Landing Marine Labs Seminar Series - November 21st, 2019

Hosted by the Chemical Oceanography Lab

MLML Seminar Room, 4pm

Open to the public

Tomoko Komada is a marine biogeochemist at the Estuary & Ocean Science Center, San Francisco State University. She is also a faculty member at the Department of Chemistry & Biochemistry, SFSU. Her research centers on the transformation of organic matter across the land-ocean interface, and in the application of natural carbon isotopes to deconvolve carbon cycle processes. She has a PhD in Chemical Oceanography from Rutgers University, and a BA in Chemistry from International Christian University, Tokyo.

Abstract:

Organic matter decomposition at the seafloor constitutes a critical fork in the road in the global carbon cycle, where carbon is either returned to seawater and the atmosphere through decomposition, or sequestered over geological time. However, mechanisms of organic matter degradation, and factors that control its rate remain unclear. This presentation will highlight main findings from an ongoing project that aims to fill this knowledge gap by examining the composition and dynamics of dissolved organic matter (DOM) in the interstitial pore waters of marine sediments. Pore-water DOM plays a central role in the carbon recycling process, because sedimentary organic matter must be first solubilized to DOM before it can be utilized by the microbial community. Findings to date underscore the high molecular diversity of pore-water DOM, and indicate that degradation itself enhances this diversity. Degradation rate differs sharply across DOM constituents, and this variation in part correlates with the age of the substrate. Implications of these findings on the marine carbon cycle will be discussed.

 

Thesis Defense by Elizabeth Ramsay – August 9

Morphological variability within Dictyoneurum californicum and Dictyoneurum reticulatum along a wave exposure gradient on the Monterey Peninsula

A Thesis Defense by Elizabeth Ramsay

The Phycology Lab

Friday, August 9th, 2019 at 10am

MLML Seminar Room

Elizabeth Ramsay is a Masters graduate from the Phycology Lab under Dr. Michael Graham. She graduated from California State University Monterey Bay in 2015 with a B.S. in Marine Science with a concentration in Marine and Coastal Ecology. During her time at Moss Landing Marine Labs, Elizabeth had the opportunity to travel and conduct research focused on marine algal species and the ecosystems they support in Baja and Chile. She also had hands on experience with marine aquaculture systems through the MLML aquaculture seminar and her part-time work at the Monterey Bay Seaweeds farm. During her time at MLML, Elizabeth also interned with Stanford Center for Ocean Solutions, where she worked as a scientific communicator, collaborating with researchers and policy makers. Elizabeth is currently seeking out a career in the marine science field with hopes to continue her work with research, science communication, and education.

Thesis Abstract:

The ability of kelps to change the physical characteristics of their thallus in response to their environment can be both functionally and ecologically important to the individual and their local surroundings, especially relative to variability in wave exposure. For decades, Dictyoneurum reticulatum and Dictyoneurum californicum have been studied independently along the Monterey Peninsula, where there is a well-studied wave exposure gradient. Recent genetic work has shown that these two species are genetically indistinct from one another. However, there is a deficit in the knowledge and understanding of the morphological variety within Dictyoneurum and role that wave exposure may play in determining characteristics used to distinguish species. This study tested for morphological variability within the Dictyoneurum genus to document the range of morphological traits and to determine whether or not the morphological traits were genetically fixed or plastic. Year-long observational surveys were conducted in tandem with common garden experiments along a well-established wave exposure gradient on the Monterey Peninsula. I found that depth and wave exposure determined the presence of the characteristic midrib trait, where individuals with midribs were significantly more likely to be found at sheltered sites or only at deeper depths at the exposed sites. Individuals that grew in clumps were also significantly more likely to lack a midrib and split completely through the lamina versus individuals that grew solitarily, that more likely had a midrib and did not split at all. The results based on midrib and splitting presence were most significant at the intermediate sites, whereas the two extreme sites did not show that much diversity in morphological traits. There was no significant difference in growth or morphological characteristics throughout the common garden experiment, suggesting that the morphological characteristics of the midrib and splitting were not genetically fixed. The results of my study suggest that the morphological characteristic of the midrib that is currently used to distinguish between D. californicum and D. reticulatum is plastic and therefore, should no longer be used for species identification for this genus.

Watch Elizabeth’s Thesis Defense Below: