The incredible primary production of kelp forests is receiving global recognition. This has been accompanied with an eagerness to harness three ecophysiological services inherent to this impressive photosynthesis: 1) carbon fixation, 2) nutrient uptake and 3) pH modulation. However, empirical measurements of these services are few in number, rough in nature, and typically do not consider the influence of water quality.
Coastal darkening and eutrophication are two linked-yet-distinct anthropogenic stressors on kelp forests that are anticipated to intensify with climate change. Here, we investigate how the form and duration of these stressors affect the ecophysiology of Ecklonia radiata, the dominant canopy-forming kelp in northeastern Aotearoa New Zealand.
We found that short-term, acute ‘pulses’ of either nitrate or ammonium did not reduce subsequent photosynthetic performance nor pH modulation capacity. However, assessments following long-term exposure to degraded light and/or nutrient enrichment revealed several physiological and morphological impacts, depending on the form and, where applicable, the combination of stressors.
E. radiata is a foundational, ecosystem-engineering species. Therefore, evaluating how its functioning may change is imperative to understanding the response and resilience of temperate reef communities. This research also has implications for the application of these services to blue carbon and nutrient bioremediation initiatives.