Research which sheds light on the response of coastal ecosystems to increased atmospheric carbon dioxide will help predict the future of coastal waters.
The study by Auckland University of Technology’s Associate Professor Kay Vopel and colleagues, has just been published as an article, “Biogeochemical feedbacks to ocean acidification in a cohesive photosynthetic sediment” in the Springer Nature journal, Scientific Reports. The MBIE-funded multi-year research collaboration between Auckland University of Technology and the University of Waikato unravels the responses of seafloor microbial ecosystems to environmental disturbance.
The absorption of human made atmospheric carbon dioxide by the ocean represents one of the most significant disturbances of the Earth system including profound changes in open ocean and coastal ecosystems. Predicting these changes requires a detailed understanding of ecosystem responses (feedbacks) to this absorption, which often involve complex biogeochemical processes that can enhance or diminish the disturbance effect.
Studying the near-shore seafloor of the Hauraki Gulf, New Zealand, Dr. Vopel and co-authors have shown, for the first time, how ecosystem feedbacks to excess carbon dioxide amplify the day–night variations in the chemistry of the photosynthetic sediment surface. These day–night variations, which are a natural feature of coastal ecosystems, can influence the sediment–seawater exchange of important nutrients. Because this exchange links the seafloor with the open seawater (pelagic) ecosystem functions, understanding the mechanisms behind changes in its workings is critical to predict the functioning of the future coastal ocean.
For example, stronger variations expose seafloor organisms to more extreme conditions and decrease the stability of calcium carbonate, a mineral important for the survival of organisms that can influence the sediment–seawater nutrient exchange as the study has demonstrated.
Having unravelled feedback mechanisms of the micrometre-scale sediment surface ecosystem, Dr. Vopel and his research team are now exploring if and how their findings apply at larger spatial scales. “It appears that the mechanisms we have described work in other marine ecosystems such as lagoons and estuaries at scales of hundreds to thousands of meters to produce similar feedback,” he says.