Carbonate sediment budgets under predicted future Ocean Acidification pathways

Anthropogenically-driven climate change is an established fact. While significant efforts are being made to understand the effects of greenhouse gasses on the climate, the effects of the related process of Ocean Acidification, through the dissolution of CO₂ in seawater, receives less attention. The vast majority of ocean acidification studies have focused on the ability of marine calcifiers to precipitate skeletal material under a scenario of falling pH. The lowering of marine pH is accompanied by a decrease in calcium carbonate (CaCO₃) saturation, thus increasing the dissolution of carbonate skeletal material – particularly aragonite.

 

Predicted future ocean surface pH values, on the basis of IPCC SSP climate scenarios, range between 8.0 and 7.7 by the year 2100. While the potential effects on marine calcifiers are worrying, such extreme reductions in pH will also have significant consequences for future carbonate sediment budgets. This is particularly a concern for low-lying tropical island nations.

 

This study experimentally assesses the effects of ocean acidification, at a range of predicted future pH scenarios, on carbonate bioclasts in a simulated tropical shallow marine environment. During each experimental run, targeted carbonate materials were subjected to an extended period of exposure under predicted future pH conditions. Experiments were run in duplicate, under both passive and dynamic conditions, so as to assess the effects of dissolution on the mechanical competence of sediment grains in natural transport scenarios. Project outcomes enable the construction of a predictive matrix for the potential effects of future ocean acidification pathways on carbonate sediment budgets. Outcomes will directly support informed planning and decision making, particularly in resilience and vulnerability assessments.