Are Warming Ocean Temperatures Altering Photosynthesis and Respiration in Nereocystis luetkeana?

Abstract

Due to climate change caused by anthropogenic stressors there has been an increase in warming ocean temperatures that have led to the decline of kelp forest cover as well as range shifts (Duarte et al. 2018). Because of the increases in our need for climate mitigation a call to action for direct and indirect changes, like the restoration of wetlands and kelp forests because of their natural ability to act as a carbon sink, has become increasingly popular (Gallagher, Shelamoff, Layton 2022). Kelp forests are threatened by warming ocean temperatures, with their ability to adapt to temperature thresholds relying on adaptation and plasticity in response to thermal events (Gauci et al. 2022). The ability of kelp to adapt can take many generations (Gauci et al. 2022), while increasing temperatures affect this ability and their metabolic functions (Green-Gavrielidis & Thornbur 2022). As the ocean warms, canopy forming kelps may decline in health, leading to decreased growth and increased mortality. This leads to a loss in carbon sequestration potential (the capture and storage of carbon from our atmosphere by algae for ~100 plus years) resulting in an increase in kelp respiration rates, a loss of carbon fixation and Net Primary Production (NPP) (Gao et al. 2021). This study looked at the physiological effects of increasing ocean temperatures in Nereocystis luetkeana. The expected outcome was that increasing ocean temperatures would drive an increase in kelp respiration rates and decrease carbon fixation rates through photosynthesis.