Reef Plan Marine Monitoring Program - Project - Inshore water quality monitoring (AIMS)

Introduction

The management of water quality is essential to ensure the long-term protection of the coastal and inshore reefs of the Great Barrier Reef (GBR). The land management initiatives under the Australian and Queensland Government's Reef Water Quality Protection Plan 2009 (Reef Plan) are key tools to improve the water quality entering the GBR. Long-term monitoring at 20 fixed sites (Figure 1) is part of the Reef Plan and is fundamental to determine the status and long-term trends of marine water quality of the coastal and inshore GBR lagoon.

The 6th year of long term water quality monitoring was completed in June 2011.  An index of water quality derived from long term means (Table 1) was: good to very good at 12/20 sites, poor to very poor at 5/20 and fair at 3/20 sites.

Water quality in the inshore GBR lagoon shows distinct gradients away from river mouths and are influenced over short time periods by river floods and by wind-driven resuspension of seafloor sediments. The natural seasonal differences and extreme difference in river discharges since the start of the MMP sampling (a few drier years at the start of the program and extreme wet seasons during the past three years) currently best explain the data variability. A longer time series will be required to distinguish the influences of land management changes from the high temporal variability in the marine water quality data.

This page summarises one component of the Reef Plan Marine Monitoring Program (MMP). Information about the whole program and links to other components can be found here.

Methods

The MMP site-specific water quality monitoring in the inshore lagoon has started in 2005 at 14 fixed coral reef sites in four Natural Resource Management Regions (NRM) regions, the Wet Tropics (5 sites), Burdekin (3), Mackay Whitsunday (3) and Fitzroy regions (3).  As part of the regular monitoring we collect water samples that are analysed for a comprehensive suite of dissolved and particulate nutrients and carbon, suspended solids, chlorophyll a and salinity. We also use sensors with data logging capacity for continuous measurements of temperature, chlorophyll and turbidity. Sampling of the longest available time series of water quality data for the Great Barrier Reef (GBR) (since 1989) has also continued at 6 sites in coastal waters between Cape Tribulation and Cairns. Figure 1 shows where these 20 sites are.

The Water Quality Guidelines for the Great Barrier Reef Marine Park (GBRMPA 2009; hereafter called “the Guidelines”) are used to interpret the water quality values obtained at the 20 sampling sites to identify areas/sites with potential water quality issues.

Figure 1   Sampling sites of the Reef Rescue MMP inshore marine water quality monitoring. Red symbols indicate the 14 sites where autonomous water quality instruments (temperature, chlorophyll and turbidity) were deployed and regular water sampling was undertaken. Yellow symbols are the sites of the ‘Cairns Transect’, which have been sampled by AIMS since 1989. NRM region boundaries are represented bycolouredcatchment areas and the black line for marine boundaries.

Key results

The water quality index at eight out of the eleven Wet Tropics sites was rated as ‘good’ or ‘very good’; three of these are located in the midshelf water body (Table 1).  The remaining three sites were rated as ‘poor’. These were Dunk Island, Yorkey’s Knob and Fairlead Buoy, all of which are close to river mouths that drain catchments with intensive agricultural land uses. The ‘poor’ score was due to long-term means of chlorophyll, turbidity-related values (combined SS, Secchi and turbidity data) and PP that exceeded the Guidelines. 

Of the three sites in the Burdekin Region, the water quality index of the two sites located in the midshelf water body was rated as ‘good’, while the Magnetic Island site that is closer to the mainland and to riverine influence had a ‘poor’ rating (Table 1). Long-term mean turbidity (combined score of SS, Secchi and turbidity), chlorophyll and PP values exceeded the Guidelines.

The water quality index at Double Cone Island in the Mackay Whitsunday Region was rated as ‘good’, while the two other sites were rated as ‘fair’ (Table 1). The long-term means of chlorophyll and turbidity (combined scores) at these sites exceeded the Guidelines.

In the Fitzroy Region, the most inshore location, Pelican Island had a water quality index of ‘very poor’ (Table 1). The long-term means of all four indicators exceeded the Guidelines. The other two sites in this region, were rated as ‘good’ and ‘very good’, in line with their increasing distance away from river influence.

Table 1: Interim site-specific water quality index for monitoring data from August 2005 to June 2011. The six sitesof the ‘AIMS Cairns Transect’ (open water sampling) are in italics. Underlined sites are in the “midshelf” water body, as designated by the GBR Water Quality Guidelines (GBRMPA 2009); all other sites are in the “open coastal” water body.

The interim water quality index aggregates the assessments of compliance (score= 0) or exceedance (score=1), as compared to the GBR Water Quality Guidelines (GBRMPA 2009), of long-term means (2005-2011) of each of four indicators:

• Acombined chlorophyll indicator (averaging scores for chlorophyll concentrations measured in water samples at all sites and chlorophyll fluorescence data from FLNTUSB instruments at 14 sites);
• A combined turbidity indicator (averaging scores for suspended solids concentrations in water samples and Secchi depth readings at all sites and turbidity values fromFLNTUSB instruments at 14 sites;
• Particulate nitrogen concentrations in water samples at all sites and
• Particulate phosphorus concentrations in water samples at all sites.

The lowest overall score is 0, indicating full compliance of all indicators with the guidelines; 4 is the maximum score if all 4 indicators exceed guideline values, indicating impaired water quality. The colour scheme used is consistent with other marine condition reporting under the Paddock to Reef Monitoring, Modelling and Reporting Program and colours reflect the status of water quality: red (very poor), orange (poor), yellow (fair), light green (good), dark green (very good).

An example of the variability of the water quality variables turbidity and chlorophyll over short time periods is shown in Figure 2 using data collected in Geoffrey Bay at Magnetic Island in the Burdekin NRM region.  Note the very high turbidity values during and after the passage of the severe tropical cyclone ‘Yasi’ in early February 2011.

Figure 2   Time series of daily means of chlorophyll fluorescence (green line, µg L^-1) and turbidity (brown line, NTU) collected by Eco FLNTUSB instruments at Magnetic Island in the Burdekin NRM Region. Additional panels represent daily discharge from the Burdekin River (blue line, ML day^-1 x 10⁵) and daily wind speeds (grey line, km h^-1) from the Townsville Airport weather station.

Management of coastal water quality in the GBR region is undertaken at the ecosystem-scale, along the catchment-to-reef continuum.  However, the impacts of land runoff have to be considered as part of global change and we need to better understand the complex responses and thresholds of coastal ecosystems, especially in interaction with other anthropogenic pressures on the coastal zone and with climate change. Programs like the MMP will allow us to both measure the future changes and also improve our understanding of the functioning of the coastal and inshore Great Barrier Reef ecosystem.

Reports from this project

These reports cover the work of this project in detail:

• Final MMP Inshore Water Quality Monitoring Report 2010-2011 (6.3 MB)
• Inshore water quality monitoring 2009-2010  (5.3 MB)
• Inshore coral and water quality monitoring 2008-2009 (3.4 MB)
• Inshore water quality and coral monitoring 2007-2008 (3.4 MB)
• Inshore water quality and coral monitoring 2006-2007 (5.5 MB)

Project meta-data

The full meta-data for this project can be found in the following record: Reef Plan Monitoring of Inshore Water Quality, Great Barrier Reef

Maps in the e-Atlas

The following map shows a summary of the inshore water quality monitoring and coral reef monitoring. This map is downloadable as a KMZ. This layer shows three main datasets:

• Water quality monitoring loggers showing annual time series graphs of turbidity and chlorophyll from 2007-2011.
• Coral cover (percent) showing annual time series of hard coral, soft coral and macro algae from 2005-2011.
• Nutrient data (particulate nitrogen, particulate phosphorus, suspended solids, secchi depth) gathered from bucket samples as an average of all data from 2005-2011.