Sustaining intertidal diversity on artificial habitats in Sydney Harbour

Professor Gee Chapman

Preparing a seawall for experiments

Diversity is often estimated from simple counts of organisms and ecological interactions among species are ignored. Yet, natural interactions among species, e.g. between resources and consumers, competitors, parasites and hosts, etc., must sustain diversity, because it is primarily these ecological processes that determine patterns of abundance. Approximately 50 % of the shoreline of Sydney Harbour is artificial, mainly seawalls. At first glance, seawalls appear to provide habitat for intertidal animals and plants, but they do not support natural assemblages and many species which are common on rocky shores are found at unnatural densities or are absent from seawalls. Many of these are important in determining patterns of abundance of many other species and the diversity on natural rocky shores. Shoreline development in urbanized estuaries has the potential therefore, to affect long-term sustainability of marine biodiversity.


This project will:

1) test how changes in abundances of important grazing intertidal animals on seawalls are due to the physical nature of the wall (e.g. surface material), changes in food supply (i.e. food of different quality of quantity) or changes in abundances of competitors

2) test the extent to which competition for food or shelter has developed among species that do not normally come into contact on rocky shores (being generally separated by 10s of metres), but which are brought into close proximity on seawalls (where the intertidal zone is generally <2m wide (i.e.high))

3) predict long-term effects of such changes on the structure of intertidal assemblages on seawalls and, the likely consequences to biodiversity of more development of shorelines

Preparing a seawall for experiments

One of the most pressing issues facing environmental managers in coastal towns and cities is to plan development to meet societies’ needs, while sustaining diverse functioning ecological systems. Planning coastal developments is hampered by needs to alter shorelines, but within the context of little understanding of the consequences for conservation. This research will provide some important answers about the feasibility of long-term conservation of intertidal assemblages in estuaries with ever-increasing amounts of development.


Results will be posted as they become available