Busting a salty myth: long-term monitoring detects limited impacts on benthic infauna after three years of brine discharge

Abstract

The Gold Coast Desalination Plant (GCDP) was built in 2006 following six years of crippling drought and water restrictions, and began supplying water to Southeast Queensland (Australia) in 2009. Preliminary reports identified potential environmental impacts resulting from the discharge of desalination effluent (brine) on the receiving environment (a soft sediment ecosystem in the nearshore coastal zone). In accordance with regulatory approvals and good environmental practice a monitoring program of the marine environment was designed and implemented to assess the impact of brine discharge on benthic infauna within 60 m of the discharge diffuser, which is the expected maximum distance at which complete dilution occurred from the 14 diffuser nozzles (based on dispersion plume modelling). Monitoring of benthic infauna is one part of GCDP’s Marine Water Quality Monitoring Program (MWQMP). This study adds to the growing number of monitoring programs assessing the potential impact of brine discharge on the receiving environment, using a long term monitoring approach that incorporates industry leading monitoring design principles including sampling before and after the plant began to discharge. Long term monitoring, has allowed an assessment of the potential long term impact of discharge on the composition of benthic infaunal assemblages, relative to those found in areas that remain unaffected. Since beginning operation in March 2009, the environmental impact of the discharge of brine on benthic infauna has been minimal. Instead, the effects of natural seasonal factors have contributed more substantially to the differences in the composition of benthic assemblages between impact and control sites. In assessing impacts on benthic assemblages it is extremely relevant to understand these natural fluctuations in the structure and composition of assemblages preferably at multiple comparative or control sites, rather than just relying on monitoring of impact sites alone.

Keywords:

• Desalination
• Environment
• Ecology
• Monitoring
• Richness
• Abundance