Macroalgal Carbon Cycling & Sequestration

Kelp are among the fastest growing and most productive marine algae. During photosynthesis, aquatic algae can release fixed carbon into the seawater as dissolved organic carbon (DOC), or dissolved sugars. This process fuels microbial carbon cycling in the coastal ocean, and some of this carbon sinks into the deep ocean, contributing to global carbon sequestration. My lab uses stable isotopes of carbon (13C) as a biological tracer to study carbon fixation and release by kelp. We found that carbon fixation by bull kelp is as high as 2.35 kg C m−2 yr−1, but an average of 16% of this carbon is released as DOC into the surrounding seawater (Weigel and Pfister 2021). This can elevate DOC concentrations in seawater by ~50% inside of kelp forests (Pfister et al. 2019). 

My lab will continue to enhance our understanding of kelp forest contributions to global carbon cycling and sequestration. It is estimated that 50% of all macroalgal carbon sequestration occurs through the DOC pathway. However, we know little about the production and fate of this substantial quantity of organic carbon released by kelps. Our research group will shed light on how much kelp carbon is potentially sequestered in the deep ocean, processed by microbial communities in the seawater, or enters the nearshore food web, which supports important fisheries such as salmon and rockfish.