icolls - Sustainable Tourism CRC

ECOLOGY, THREATS AND MANAGEMENT OPTIONS FOR SMALL ESTUARIES AND ICOLLS
Whilst techniques for examining the impacts of sewage discharges are applicable to a wide range of aquatic
environments, the effects of STP effluent discharge have most often been examined in large macrotidal estuaries
(Hall, Frid & Gill 1997; Leeming & Nichols 1998; Costanzo, O’Donohue & Dennison 2003), bays and open
coastal waterways (Tucker, Sheats, Giblin, Hopkinson & Montoya 1999; Seguel et al. 2001; Rogers 2003) and
more recently, coral reefs (Risk & Erdmann 2000; Umezawa, Miyajima, Yamamuro, Kayanne & Koike 2002;
Yamamuro, Kayanne & Yamano 2003). However, given the number and distribution of ICOLLS in Australia
(Roy et al. 2001), it is timely that an investigation of the effects of STP inputs be conducted in this subset of
estuaries.
Materials and Methods
Sampling Sites
This study was conducted in Tallows and Belongil Creeks; two ICOLLS in northern New South Wales, Australia
(Figure 3). These systems are typical of many of the small ICOLLS in eastern Australia and are characterised by
having relatively small catchments with a diverse range of land uses.
Australia
Figure 3: Map of study ICOLLs in Byron Bay, New South Wales, Australia
Both Belongil Creek and Tallows Creek have received large amounts of nutrients over the past 50 years,
principally from STPs that discharge into their waters (McAlister et al. 2000). However, the Belongil Creek
system receives sewage from the West Byron Treatment Plant, which discharges treated wastewater into an
extensive treatment wetland system before it enters the waters of the creek. The success of this treatment is
reflected in the nutrient concentrations in this system. For example, McAlister et al. (2000) reported that
Belongil Creek nutrient concentrations are within ANZECC water quality guidelines during wet weather
conditions, but may partially exceed the guidelines during dry periods. In contrast, Tallows Creek receives
effluent directly from the South Byron Treatment Plant, which uses comparatively old treatment technologies.
McAlister et al. (2000) investigated the fate and effects of these direct inputs and found that nutrient
concentrations in Tallows Creek consistently exceeded the ANZECC water quality guidelines (ANZECC 1999),
with total nitrogen ranging from 1 – 6 mg/L and total phosphorus from 0.2 – 1.8 mg/L over the course of their
study.
Sampling Methods
NSW
A
Samples for stable isotope analysis of food web structure were collected in both systems in early May 2003.
Significantly, sampling occurred immediately following an artificial opening event in Tallows Creek, whereas
Belongil Creek had been open and subject to tidal influences for the proceeding two months. In both systems,
samples were collected from two sites less than 500 m from the entrance. Where possible, replicate samples of
key taxa were processed separately. The reported mean (± S.E.) stable isotope signatures consequently revealed
A
Belongil Creek
Tallows Creek
Taylor’s Lagoon
Cape Byron
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