The impact of turbidity on seagrass and other marine life

Historically, dugongs and turtles grazed on seagrass beds within Bramble Bay, but high turbidity and nutrients eliminated these beds at least 30 years ago. Current water quality conditions of Bramble Bay are unsuitable for the re-establishment of seagrass meadows. Nitrogen in the Bramble Bay zone has been decreasing since the upgrade of the Luggage Point Waste Water Treatment Plant (WWTP) in 2001. However, poor flushing continues to contribute to the poor condition of this catchment, the area possessing the longest residence time of Moreton Bay (59 to 62 days).

Deception Bay is situated at the northern section of Moreton Bay from Newport up to the south of Bribie Island and receives input from the Caboolture River, Pumicestone Passage and several other streams including Burpengary Creek.

Extensive seagrass meadows are present in the northern part of the bay but have been threatened by toxic Lyngbya blooms. Lack of seagrass recovery is likely due to discharge of poor quality water from the Caboolture River which remains a pressure on Deception Bay’s overall ecosystem health. Poor flushing resulting in turbidity in that area of Deception Bay compounds the impact of this discharge.   Since 2002 Healthy Waterways has monitored 9 sites within the Deception Bay reporting zone.

Source: http://hlw.org.au/region/baycatchments

Seagrass Monitoring data from Wildlife Queensland Coastal Citizen Science has enabled the processing of Landsat imagery (USGS product) to understand the impact of Turbidity upon seagrass in Deception Bay. The negative impact is quite clearly seen in Sheet 10 of https://public.tableau.com/profile/wpccs#!/vizhome/mbay-sgw/Dashboard1  

A recent seagrass survey at Ormiston (Moreton Bay) noted turbidity impacting upon the coral reef located adjacent to the monitoring site.   This area supports coral gardens but they are under threat from too much turbidity. If we want to protect these amazing coral gardens we need to improve our land management within the catchment, starting with protecting natural vegetation.

 

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