ASSESSING MACROALGAL ORGANIC CARBON RELEASE AND SUBSEQUENT BIO- AND PHOTO-DEGRADABILITY

As macroalgae grow, they release C, primarily as dissolved organic carbon (DOC). In natural systems, most macroalgal C (MA-C) sequestration is hypothesized to occur when DOC is exported into deeper waters. Thus, MA-C sequestration is a function of MA-DOC release and the resistance of MA-DOC to bio- and photo-degradation. Current estimates of MA-C sequestration efficiency rely on scarce data on 1) rates of DOC release as macroalgae grow, and 2) how rapidly MA-DOC is remineralized back to CO₂, with most of the latter studies focusing only on biodegradation. Thus, it is unclear whether bio- and photo-degradation processes acting on MA-DOC in the ocean are slow enough to allow DOC to persist long enough to be exported and sequestered below the mixed layer. Here we present an accounting of MA-DOC release during ca. month-long laboratory growth experiments and during subsequent bio- and photo-degradation experiments using 7 common macroalgal species: Ascophyllum nodosum, Fucus distichus, Ulva lactuca, Gracilaria hayi, Gracilaria parvispora, Spermothamnion species, and Laminaria saccharina. We present DOC release and degradation kinetics in the context of natural macroalgal OC cycling and report on the potential recalcitrant fraction of DOC from each species that might have the capacity to contribute to C sequestration. 

Primary Presenter: Jessica Gould, Northeastern University (jlagould@gmail.com)

Authors:

Jessica Gould, Northeastern University  (jlagould@gmail.com)

Cassandra Vongrej, Northeastern University  (vongrej.c@northeastern.edu)

Aunjoli Das, Northeastern University  (das.a@northeastern.edu)

Lixin Zhu, Northeastern University  (lix.zhu@northeastern.edu)

Aron Stubbins, Northeastern University  (a.stubbins@northeastern.edu)