Sydney Harbour: a review of anthropogenic impacts on the biodiversity and ecosystem function of one of the world’s largest natural harbours M. Mayer-Pinto A,B,L , E. L. Johnston A,B , P. A. Hutchings C , E. M. Marzinelli A,B,D , S. T. Ahyong C , G. Birch E , D. J. Booth F , R. G. Creese G , M. A. Doblin H , W. Figueira I , P. E. Gribben B,D , T. Pritchard J , M. Roughan K , P. D. Steinberg B,D and L. H. Hedge A,B A Evolution & Ecology Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia. B Sydney Institute of Marine Science, 19 Chowder Bay Road, Mosman, NSW 2088, Australia. C Australian Museum Research Institute, Australian Museum, 6 College Street, Sydney NSW 2010, Australia. D Centre for Marine Bio-Innovation, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia. E School of GeoSciences, The University of Sydney, Sydney, NSW 2006, Australia. F Centre for Environmental Sustainability, School of the Environment, University of Technology, Sydney, NSW 2007, Australia. G New South Wales Department of Primary Industries, Port Stephens Fisheries Institute, Nelson Bay, NSW 2315, Australia. H Plant Functional Biology and Climate Change Cluster, University of Technology, Sydney, NSW 2007, Australia. I Centre for Research on Ecological Impacts of Coastal Cities, School of Biological Sciences, University of Sydney, NSW 2006, Australia. J Water and Coastal Science Section, New South Wales Office of Environment and Heritage, PO Box A290, Sydney, NSW 1232, Australia. K Coastal and Regional Oceanography Lab, School of Mathematics and Statistics, University of New South Wales, NSW 2052, Australia. L Corresponding author. Email: m.mayerpinto@unsw.edu.au Abstract. Sydney Harbour is a hotspot for diversity. However, as with estuaries worldwide, its diversity and functioning faces increasing threats from urbanisation. This is the first synthesis of threats and impacts in Sydney Harbour. In total 200 studies were reviewed: 109 focussed on contamination, 58 on habitat modification, 11 addressed non-indigenous species (NIS) and eight investigated fisheries. Metal concentrations in sediments and seaweeds are among the highest recorded worldwide and organic contamination can also be high. Contamination is associated with increased abundances of opportunistic species, and changes in benthic community structure. The Harbour is also heavily invaded, but invaders’ ecological and economic impacts are poorly quantified. Communities within Sydney Harbour are significantly affected by extensive physical modification, with artificial structures supporting more NIS and lower diversity than their natural equivalents. We know little about the effects of fishing on the Harbour’s ecology, and although ocean warming along Sydney is among the fastest in the world, we know little about how the ecosystem will respond to warming. The interactive and cumulative effects of stressors on ecosystem functioning and services in the Harbour are largely unknown. Sustainable management of this iconic natural system requires that knowledge gaps are addressed and translated into coherent environmental plans. Additional keywords: contamination, habitat modification, NIS, Port Jackson, threats, urbanisation. Received 18 April 2015, accepted 2 October 2015, published online 16 November 2015 CSIRO PUBLISHING Marine and Freshwater Research, 2015, 66, 1088–1105 http://dx.doi.org/10.1071/MF15157 Journal compilation Ó CSIRO 2015 www.publish.csiro.au/journals/mfr Review