We assessed the effects of primary, secondary and tertiary treated sewage on the stable isotope composition of the viscera and muscle of the zooplanktivorous eastern hula fish (Plesiopidae: Trachinops taeniatus). Fish were collected from three regions during three consecutive summer months for 2 years. In comparison to fish from control sites, the muscle ä 15N of fish at outfall sites was significantly enriched by secondary and tertiary treated effluent. We estimate that 30-50% of nitrogen in hula fish near outfalls may be sewage-derived. The ä34S content of muscle was similar at all regions and sites (20-21‰), although it was significantly depleted by 1-2‰ at the tertiary treated outfall site. Detection of a comparatively minor volume of effluent (<6 ML day -1) in fish muscle may be due to its slower tissue turnover rate and the continuous discharge of effluent at outfall sites, compared to major yet sporadic rainfall or oceanographic events. The isotopic composition of hula fish from near a large primary treated sewage outfall off the coast of Sydney was not significantly different from one of the control sites, indicating a regional effect of four outfalls discharging > 1000 ML day-1. With increasing upgrades to sewage treatment, stable isotopes may become useful tracers of anthropogenic nutrients in an oligotrophic environment.

Item Type:	Refereed Article
Research Division:	Biological Sciences
Research Group:	Ecology
Research Field:	Marine and Estuarine Ecology (incl. Marine Ichthyology)
Objective Division:	Environment
Objective Group:	Ecosystem Assessment and Management
Objective Field:	Ecosystem Assessment and Management of Coastal and Estuarine Environments
Author:	Gaston, TF (Dr Troy Gaston)
ID Code:	63071
Year Published:	2004
Web of Science® Times Cited:	22
Deposited By:	NC Marine Conservation and Resource Sustainability
Deposited On:	2010-04-13
Last Modified:	2010-05-04
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