A systems approach to exploring the influence of ‘Ocean Acidification’ on nutrient cycling in coastal zones

Abstract

Global concentrations of aqueous carbon dioxide (CO2) have been steadily increasing since the onset of the industrial revolution. A consequence of this has been an observed decrease in the pH of seawater as its natural buffering capacity has become overwhelmed. Research into this ‘ocean acidification’ effect has only emerged recently, although there is already compounding evidence that the impacts will be wide-ranging. This is because pH is a dominant variable in controlling biogeochemical processes. A potentially critical effect of decreasing pH is how it influences nutrient cycling in coastal zones, which will have flow-on effects on primary and secondary producers and has various implications including nutrient management, ecosystem health and carrying capacity. Of these, nutrient management is of particular concern because (1) the effect of decreasing pH combined with other expected changes in climatic conditions (e.g. increased storm events, increased water temperature) will alter the environmental fate of nutrients; and (2) there will be increased demands for managing ‘recycled’ water discharges into coastal waters arising from increasing populations. We present here a systems approach to mapping nutrient cycling within the context of ocean acidification for a sub-tropical coastal waterway located in southeast Queensland, Australia. This conceptualization will help to identify the causal pathways (including feedback loops) between a suite of important social, economic and environmental variables and highlight important leverage points for adaptation strategies for nutrient management under ocean acidification.