Marine Community Respiration Rates In Response to Climate Change

With carbon dioxide concentrations on the rise, the storage of much of this additional CO₂ in the world’s oceans has the potential to alter marine chemistry and biology as we know it today. With increasing CO₂ concentrations, both decreases in oceanic pH and increases in sea surface temperatures are predicted. Furthermore, increases in sea surface temperatures (SSTs) have the potential to influence key upwelling cycles, which bring nutrient-rich waters to the surface ocean, where such waters can undergo photochemical alterations of nutrient availability. Finally, changes in SSTs could lead to increases in storm frequency and storm water run-off and thus excess nutrient inputs to the coastal oceans. These changes would influence the microbial communities present in the ocean. Thus, it is the goal of the present work to address how changes in marine chemistry associated with climate change will impact marine microbial communities in San Pedro Basin of the Southern California Bight—specifically in regards to rates of respiration.  In preliminary work measuring respiration rates ex situ using O₂ microsensors, it has been found that community respiration rates increase in response to increasing amounts of nutrients (e.g. ammonia) up to a threshold value, and this threshold value depends on the original depth of the microbial community.   It has also been found that for surface ocean microbial communities, respiration rates are highest in waters that have been photochemically altered, suggesting some response to a change in DOC availability.  Thus, evidence already indicates metabolic responses by marine microbial communities to anthropogenic forcing.