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Monitoring in Cleveland Bay

Page last updated on 15-05-2024.

Monitoring in Cleveland Bay

Marine Water Monitoring

The Port of Townsville has deployed a number of real-time marine water monitoring buoys in Cleveland Bay.  One monitor is located at a navigational channel marker in Cleveland Bay referred to as Pylon S2, and the second is located at Geoffrey Bay, Magnetic Island and was named Beagle by the Port of Townsville’s Community Liaison Group to reflect regional and port history.  HMS BEAGLE was a survey ship that surveyed these waters first in 1841 and the naturalist Charles Darwin was aboard on the second voyage of the vessel, and this was his trip of discovery.

Buoy Marine Water Parameters

The marine water monitoring buoys measure marine water quality at approximately 1m below the water surface.  Individual water quality sensors measure parameters including temperature, conductivity (EC) and turbidity.  Each monitor has a mechanical wiper to prevent biofouling of the sensors.  Sensors are calibrated according to manufacturer’s guidelines and changed out regularly to ensure data accuracy.

Temperature – the marine water buoys measure temperature in degrees Celsius (oC).  Temperature is affected by ambient temperatures (summer vs winter), riverine inflows and tidal mixing (wave action).  Water temperature is important in the functioning of aquatic ecosystems and can affect the diversity and distribution of marine organisms including seagrass, corals and fish.

Conductivity – the marine water buoys measure electrical conductivity, or conductivity for short (a measure of the saltiness of water) in microsiemens per centimetre (µS/cm).  Conductivity in the ocean is typically in the range 50-55,000 µS/cm, however conductivity in Cleveland Bay can be affected by freshwater inflows in times of floods and cyclones.  Aquatic ecosystems function within a typical conductivity range and changes outside of this can stress organisms.

Turbidity – the marine water buoys measure turbidity in Nephelometric Turbidity Units (NTU).  The term Nephelometric refers to the way the instrument estimates how light is scattered by suspended particulate material in the water.  The Nephelometer, also called a turbidimeter, has a photocell (similar to the one on your camera or your bathroom nightlight) set at 90 degrees to the direction of the light beam to estimate scattered rather than absorbed light.  This measurement generally provides a very good correlation with the concentration of particles in the water that affect clarity.

Turbidity is caused by particles suspended or dissolved in water that scatter light making the water appear cloudy or murky.  Increased turbidity in water decreases the amount of light that can penetrate below the surface.  Light penetration is important for the health of ocean plants (like seagrass) and algae that live on some corals to make food (photosynthesis).  Historical records show that turbidity occurs on average 220 days of the year for water depths up to 5 metres due to wind and current resuspension.  This means the shallow areas of Cleveland Bay are naturally turbid for about two thirds of the year.


Raw data from the sensors is collected every 15 minutes via a data logger on the buoy and transmitted by mobile network to a data server.  Data is then averaged over the hour and made available on the website.  Raw data is reviewed for quality control purposes to flag data points that are related to faulty sensors, outside calibration ranges or outside of ranges compared to other nearby buoys/stations.  

Marine water monitoring plans and the data from Cleveland Bay can be downloaded below.

Disclaimer:  Whilst Port of Townsville Limited (Port) has taken care in the preparation of all information, neither the Port, any related body corporate of the Port nor any of their officers, employees, consultants, officers, advisors or agents gives any warranty, nor makes any representations (express or implied) as to the completeness, adequacy, suitability, quality or accuracy of this information. Users of this information do so at their own risk and are responsible for ensuring that the information meets their requirements for any proposed usage.

Seagrass Monitoring

Seagrasses are a key species in indicating changes to water quality making them ideal to monitor and understand the overall health of the marine environment in Townsville.

The Port of Townsville and James Cook University’s TropWATER team have partnered to survey seagrass in Cleveland Bay annually since 2007.

The annual boat and helicopter surveys asses the condition and species of more than 25,000 hectares of seagrass meadows  in the Townsville region and track changes over time.

2023 Seagrass Report    

The 2023 annual seagrass survey results for Townsville and Cleveland Bay showed:

  • The overall condition of seagrass in Cleveland Bay was ’Satisfactory’ in 2023.
  • Seven of the 12 monitoring meadows were in a satisfactory or better condition, while five were in poor condition.
  • While an extensive seagrass footprint was present, declines in the meadow biomass and/or area between October 2022 to October 2023 were recorded across most meadows and are explained by local environmental conditions.
  • Unfavourable environmental/growing conditions throughout 2023 included above average annual and monthly rainfalls, above average river flow inputs and tidal exposure and sustained and extended periods of low light conditions.
  • Green sea turtles and their feeding trails in seagrass meadows were observed during field surveys, indicating a high use of the area by herbivorous marine megafauna.
  • Although the overall ‘satisfactory’ condition of seagrass in 2023, seagrasses in Townsville still had good spatial coverage, good species composition and the presence of higher light require species in the subtidal meadows is a good indicator that seagrass in the region have some level of resilience and a capacity to return to better overall meadow conditions if favourable environmental conditions were present through 2024.

The Dry Tropics Partnership for Healthy Waters has recently developed a StoryMap on the seagrasses of Cleveland Bay.

Seagrass Story Map


Dry Tropics Partnership for Healthy Waters  

Launched in 2019, the Townsville Dry Tropics Partnership for Healthy Waters is an initiative made up of stakeholders from community, industry, education, science and government organisations. The Partnership produces an annual, independent regional report card on the status of our region’s waterways and associated habitats, as well as the social and economic benefits our waterways and Reef provides to the Townsville community.

Hosted by Townsville City Council, the Dry Tropics Partnership for Healthy Waters is funded by the Australian and Queensland Governments and collaborating partners, including the Port of Townsville. The Partnership is independently chaired and supported by a management committee and two staff who oversee day-to-day operations.

The Report Card focusses on the health of the Townsville region’s freshwater, estuary and coastal waters that lead to the outer Greater Barrier Reef. The catchment area covers a land area of about 134,000km2 and 12,000km2 of sea area. It includes the greater Townsville area and extends north to Crystal Creek and south to Crocodile Creek (near Cape Cleveland). The marine area includes Cleveland Bay and Halifax Bay, Magnetic Island, the Palm Island Group, and offshore to the outer boundary of the Great Barrier Reef Marine Park.

The term “dry tropics” refers to the region which has an average rainfall range of 500 mm to 1000 mm per year. Most rainfall occurs over a few weeks during the summer months. The Dry Tropics region in Queensland is typically defined by the Burdekin River watershed and waterways north and south of Townsville.

Understanding the condition of our waterways and catchments is important for identifying which areas are healthy and others which may need improving. It is also important to determine and understand the potential impacts affecting our waterways. This information will help us track improvements over time and help decision-makers target investment where it is needed most.


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