Caboolture Region Water Quality Study - Moreton Bay Regional ...

Deception Bay
5.4 Deception Bay
Water quality throughout Deception Bay was variable (Figure 11). Generally the sites closer to land
had poorer water quality than those further from land. Conductivity was elevated at all sites, although
in a marine environment such as this, this indicator does not accurately represent problems with
salinity. Excluding conductivity, most sites rated good for all indicators, although sites close to the
mouth of the Caboolture River (Dec-j,l) and close to the canals on the Redcliffe peninsula (Dec-u,y,x)
had elevated concentrations of nutrients and in some cases chlorophyll-a. This likely reflects their
proximity to the land-sourced influences entering Deception Bay.
Figure 11: Final water quality assessments for the Deception Bay for the year 2000-2001. These ratings represent assessments
based on water quality data for the period October 2000 to September 2001. The dots indicate the latest water quality
assessment in comparison to the Queensland Water Quality Guidelines (green = good, yellow = moderate, red = poor, grey =
insufficient data or median was detection limit which was greater than the guidelines).
Many sites showed improvements in nitrogen (total and organic) and FRP (dissolved inorganic
phosphorus with some particulate phosphorus) (Table 12, 23, 30). However total phosphorus,
dissolved oxygen and chlorophyll-a concentrations have deteriorated over recent years at some sites
(Table 13). The regression analysis of long-term trends indicated improving dissolved oxygen
concentrations and secchi depth at the site Dec-m (Table 31, Appendix F), even though this site is
close to the Caboolture River mouth.
The Ecological Health Monitoring Program (EHMP) has detecting an increasing frequency of Lyngbya
blooms in Deception Bay in recent years. This phytoplankton smothers mangrove roots and seagrass
communities. The nuisance macro-algae Caulerpa taxifolia was also present in some areas of
northern Deception Bay.
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