Effects of fishing and acidification‐related benthic mortality on the southeast Australian marine ecosystem

Abstract

Oceanic uptake of anthropogenic carbon dioxide (CO 2 ) is altering the carbonate chemistry of seawater, with potentially negative consequences for many calcifying marine organisms. At the same time, increasing fisheries exploitation is impacting on marine ecosystems. Here, using increased benthic-invertebrate mortality as a proxy for effects of ocean acidification, the potential impact of the two stressors of fishing and acidification on the southeast Australian marine ecosystem to year 2050 was explored. The individual and interaction effects of the two stressors on biomass and diversity were examined for the entire ecosystem and for regional assemblages. For 61 functional groups or species, the cumulative effects of moderate ocean acidification and fishing were additive (30%), synergistic (33%), and antagonistic (37%). Strong ocean acidification resulted in additive (22%), synergistic (40%), and antagonistic (38%) effects. The greatest impact was on the demersal food web, with fishing impacting predation and acidification affecting benthic production. Areas that have been subject to intensive fishing were the most susceptible to acidification effect, although fishing also mitigated some of the decline in biodiversity observed with moderate acidification. The model suggested that ocean acidification and long-term fisheries exploitation could act synergistically with the increasing sensitivity to change from long-term (decades) fisheries exploitation potentially causing unexpected restructuring of the pelagic and demersal food webs. Major regime shifts occur around year 2040. Greater focus is needed on how differential fisheries exploitation of marine resources may exacerbate or accelerate effects of environmental changes such as ocean acidification.

Changes to Marine Trophic Networks Caused by Fishing

“…This generalized effect is reducing the naturally occurring competition among the original species in the network and facilitating the onset of indirect effects that generate competition among species that did not strongly interact before. Similar findings were obtained in southeast Australia with the Atlantis marine ecosystem model (Griffith et al, 2011).…”

A framework for assessing risk to coastal ecosystems in Taiwan due to climate change

“…For example, the rising atmospheric concentration of carbon dioxide (CO 2 ) is causing higher oceanic uptake of CO 2 and ocean acidification, which affects seawater chemistry and could negatively affect calcifying marine organisms (Griffith et al 2011). Coral and algal reefs appear to be sensitive to ocean acidification and increasing temperature, but these hazards may have little or no impacts on mangroves and salt marshes.…”

“…As resource exploitation increases, an ecosystem's adaptive capacity decreases. For example, a study assessing the potential impact of fishing and acidification demonstrated that areas subject to intensive fishing were at greatest risk and most susceptible to the effects of acidification (Griffith et al 2011). The same ecosystems in different areas and different ecosystems in the same area can differ considerably in their adaptive capacity and in their vulnerability to predicted climatic hazards due to future climate change.…”

The effects of global warming on fisheries: Simulation estimates

“…Another channel, in which warmer temperature may affect biomass, is through hypoxia, which consists of lower levels of oxygen in the water. The effects of global warming on biomass through hypoxia plus some risk-managing recommendations are thoroughly analysed in [77].…”