Research Report
Steven Delean and Glenn De'ath
Australian Institute of Marine Science
ISBN 9781921359200
Released November 2008
MTSRF Project 1.1.1
- Identification of indicators and thresholds of concern for
ecosystem health on a bioregional scale for the Great Barrier
Reef.
Executive Summary
Spatial patterns and temporal change of the reef biota of the
Great Barrier Reef (GBR) are examined, and potential indicators of
reef ecosystem health are presented and discussed. These indicators
form a hierarchy and range through indicators based on taxonomic
and functional groups to composite indicators of relative reef
ecosystem health, one based on the benthos and the other based on
fish abundance and diversity.
Spatial patterns and temporal change of these indicators are
modelled and presented through maps, trend plots and tabulations.
The spatial analyses are based on: (a) relative distance across and
along the GBR; and (b) six marine regions adjacent to coastal
Natural Resource Management (NRM) regions. By basing the spatial
analyses on NRM regions, the health indicators can provide valuable
input to regionally-based coastal management programs.
These analyses show similar spatial patterns of relative reef
ecosystem health across both individual and composite indicators,
with reefs in the central inner-shelf regions being in relatively
poor health.
The patterns of relative health were also related to measures of
water quality based on water clarity and concentrations of
chlorophyll, and for some indicators, poorer health coincided with
low levels of water quality (low clarity and high chlorophyll).
The analyses of temporal indicators show consistent declines in
relative benthic health of the inner and mid-shelf regions of the
GBR over the last decade, but improvements in the relative health
of fish communities, in particular on the outer shelf.
Extract from Section 1: Objective and
methods
This work comprises three components. First, analyses are
presented identifying a subset of important reef ecosystem health
indicator variables on the Great Barrier Reef (GBR). Composite
indices of reef benthos health and reef fish community health are
calculated from these indicator variables. Analyses show consistent
spatial patterns of relative reef ecosystem health for both
individual biotic indicators and composite indices. Regional
differences associated with Natural Resource Management (NRM) zones
and temporal trends in composite indices are presented and
discussed.
Second, summaries are presented of the spatial patterns of
variation in all potential reef ecosystem health indicator
variables that were examined. Spatial patterns of each indicator
variable are predicted for all GBR reefs and these predictions are
provided for use in the Reef Atlas project (see http://e-atlas.org.au/).
Third, temporal trends are provided in all potential reef
ecosystem health indicator variables, broken down by NRM marine
regions and by distance across the continental shelf. Plots
are displayed on equal y-scales to show average regional
differences and the pattern and magnitude of temporal changes.
