Environmental: Indicator Group Results

Whole Harbour

What was measured?

The environmental health of Gladstone Harbour was assessed on the basis of water and sediment quality, habitat condition and connectivity.

Water and Sediment quality

The water and sediment quality scores are based on ten water quality and seven sediment quality measures. Water and sediment quality data were collected quarterly from 51 sampling sites across thirteen zones in Gladstone Harbour, with some changing of sites in the fourth quarter. Water quality data from four sampling periods were analysed for the 2015 Report Card: August 2014, November 2014, March 2015 and June 2015. Sediment sampling was conducted in conjunction with the water quality sampling in June 2015.

Habitats

The 2015 Gladstone Harbour Report Card uses two habitat indicators within the environmental component: seagrass and coral.

The seagrass indicator consists of three sub-indicators: seagrass biomass, seagrass area and species composition. The report card results were derived from monitoring data collected from fourteen seagrass meadows in six Harbour zones: The Narrows, Western Basin, Inner Harbour, Mid Harbour, South Trees Inlet and Rodds Bay. Seagrass monitoring is conducted annually in October/November around the peak of seagrass abundance.

The coral indicator consists of three sub-indicators, coral cover, macroalgal cover and juvenile density. The report card data were collected from four reefs in the Mid Harbour and two reefs in the Outer Harbour zone. Coral monitoring will be conducted annually.

Connectivity

The connectivity indicator group consists of three sub-indicators: flushing rate (measure of water exchange through harbour zones), ecological connectivity (measure of water exchange between spawning grounds and nursery areas for iconic species) and contaminant connectivity (measure of the potential of contaminants to move to other zones). The results are based on three dimensional hydrodynamic models developed for Gladstone Harbour.


Results

Of the three indicator groups, water and sediment quality received the highest score of 0.90 (A). This very high score was due to very high sediment quality scores and high water quality scores.

The overall score for the habitat indicator group was 0.30 (D). This low habitat score was due to very poor coral scores and mixed seagrass scores. The overall score for corals in the 2015 report card was 0.18 (E) and the overall score for seagrass in the 2015 report card was 0.43 (D).

The overall connectivity score in the 2014-15 reporting year was 0.61 (C). Overall, flushing rate and contaminant connectivity received good scores of 0.77 (B) and 0.78 (B) respectively. However, ecological connectivity received a poor score of 0.29 (D).

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Environmental Indicators
2015 Results
Environmental Overall Result
Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Confidence
Confidence
Trends (from 2014 Pilot to 2015)
Trends

  Water & sediment

What Was Measured

Three sub-indicators were used to assess water quality: physicochemical condition, nutrient concentrations and dissolved metal concentrations.

Physicochemical: pH and Turbidity

Nutrients: Total Nitrogen (TN) and Total Phosphorus (TP)

Dissolved metals: Aluminium (Al), Copper (Cu), Lead (Pb), Manganese (Mn), Nickel (Ni), Zinc (Zn)

Two sub-indicators were used to assess sediment quality: metals and metalloid, and total Polycyclic Aromatic Hydrocarbons (PAH).

Metals and metalloid: Arsenic (As), Cadmium (Cd), Copper (Cu), Lead (Pb), Nickel (Ni) and Zinc (Zn)

Total PAHs: sum of 18 ​Polycyclic Aromatic Hydrocarbons (PAHs)

Why Was It Measured

Water and sediment quality are important and interconnected aspects of the harbour ecosystem. A healthy water and sediment system is necessary to sustain the health of a large number of aquatic species, including fish, turtles, dugongs, seagrass, mangroves and benthic invertebrates. A large number of catchment-related, anthropogenic and climatic factors play major roles in determining the water and sediment quality recorded in the harbour.

The Gladstone Harbour Report Card uses standard measures for water and sediment quality that were selected by the Independent Science Panel and have local or national guidelines.

The independent Science Panel in collaboration with a team of statistical consultants developed and piloted water and sediment quality indicators to address the report card objectives. Those objectives were based on a series of detailed GHHP vision statements developed by representatives of the Gladstone community and GHHP stakeholders in 2013.

The criteria for selecting indicators were:

  • conceptual relevance (indicator reflects ecosystem health),
  • feasibility (indicator is measurable),
  • response variability (spatial and temporal signal, extent and variability understood),
  • ability to detect change along a defined gradient,
  • interpretation/utility and
  • availability of relevant guidelines (see 2015 Gladstone Harbour Report Card - Technical Report for further details).

Data used to determine water and sediment quality scores and grades for the 2015 report card were provided by the Port Curtis Integrated Monitoring Program (PCIMP). This program involves extensive water and sediment quality monitoring throughout Gladstone Harbour and adjacent coastal marine environments.

What Does It Mean

Water quality was relatively uniform across the harbour with all zones apart from Boat Creek receiving good overall scores. While nutrients (nitrogen & phosphorus) mostly received poor scores, dissolved metals (aluminium, copper, lead, manganese, nickel & zinc) generally received good to very good scores. Physicochemical indicator pH received very good scores for harbour zones, although the, turbidity scores varied between satisfactory and very good. Five measures of water quality can be compared between 2014 and 2015: scores for turbidity, nitrogen, phosphorus and aluminium improved while the score for copper declined.

The causes for (or sources of) the increased levels of nitrogen and phosphorus in some harbour zones relative to the Department of Environment and Heritage Protection guidelines are currently not known.

Sediment quality scores were uniformly very high across all zones of Gladstone Harbour due to low levels of all measures (arsenic, cadmium, copper, lead, nickel and zinc and total PAHs).

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Water & Sediment Quality Results

Water
Sediment

Measures Results

Water
Sediment

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Water & Sediment Quality Results

Water
Sediment

Measures Results

Water
Sediment

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Water & Sediment Quality Results

Water
Sediment

Measures Results

Water
Sediment

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Water & Sediment Quality Results

Water
Sediment

Measures Results

Water
Sediment

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Water & Sediment Quality Results

Water
Sediment

Measures Results

Water
Sediment

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Water & Sediment Quality Results

Water
Sediment

Measures Results

Water
Sediment

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Water & Sediment Quality Results

Water
Sediment

Measures Results

Water
Sediment

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Water & Sediment Quality Results

Water
Sediment

Measures Results

Water
Sediment

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Water & Sediment Quality Results

Water
Sediment

Measures Results

Water
Sediment

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Water & Sediment Quality Results

Water
Sediment

Measures Results

Water
Sediment

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Water & Sediment Quality Results

Water
Sediment

Measures Results

Water
Sediment

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Water & Sediment Quality Results

Water
Sediment

Measures Results

Water
Sediment

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Water & Sediment Quality Results

Water
Sediment

Measures Results

Water
Sediment

  Habitats

Seagrass Results

What Was Measured

Seagrass meadows in Gladstone Harbour are located in The Narrows, Western Basin, Inner Harbour, Mid Harbour, South Trees Inlet and Rodds Bay. Three indicators of seagrass health were measured to calculate the seagrass score for the 2015 Gladstone Harbour Report Card.

Biomass: Average above-ground biomass within a monitoring meadow.

Area: Total area of a monitoring meadow.

Species composition: Relative proportions of different seagrass species.

The overall grade for each monitoring meadow was determined as the lowest grade received for the three indicators (biomass, area and species composition). The lowest grade was used rather than the average of the three sub-indicator scores because a poor grade for any one of the three described a seagrass meadow in poor condition. The zone grade was determined as the average grade of the meadows within that zone.

Why Was it Measured?

Seagrass meadows form one of the most important habitat types within Gladstone Harbour. Within the GHHP reporting area there are a total of 14 monitored seagrass meadows in six harbour zones. While the area and distribution of the seagrass meadows can vary on an annual basis, at peak distribution seagrass meadows in Gladstone Harbour can cover an area of approximately 12,000ha. In addition to providing a range of important ecosystem functions such as sediment stabilisation, nutrient cycling and carbon sequestration, seagrass meadows can also provide nursery areas for juvenile fish and foraging areas for dugongs, turtles and large fish. The Gladstone Harbour Report Card objective for key ecosystems such as seagrass is to “maintain/improve habitat function and structure of key ecosystems”.

Seagrass has been monitored in Gladstone Harbour since 2002 enabling changes in seagrass conditions to be assessed over that period.

What Does it Mean?

Seagrasses in the Gladstone region underwent significant declines during and immediately following years of above average rainfall and flow from the Calliope River. Years with a large number of poor and very poor overall meadow grades either correspond with (2010-2013) or directly follow (2004, 2014) flooding and major rain or storm activity in the region. Declines in the condition of monitored meadows were indicative of wider declines in seagrasses across the Port Curtis region.

Declines in seagrass biomass were also associated with high flows in the Calliope River with the strongest associations occurring at monitored meadows closest to the river mouth (e.g. near Wiggins Island in the Western Basin). The timing of flood-related seagrass declines in 2010 and 2011 prior to the commencement of the capital dredging program makes it difficult to ascertain what additional impacts dredging may have had on seagrass condition and subsequent rate of recovery. However monitoring of light levels during the Western Basin Dredging and Disposal Project indicated that light levels were maintained above locally derived guidelines at seagrass meadows outside of the dredging locations.

Species composition scores below 0.85 were mostly a result of a shift from the more stable species Zostera muelleri to meadows dominated by colonising Halophila ovalis between 2009 and 2014. Shifts back to Z. muelleri dominance in some meadows indicates both propagule availability and suitable conditions for recruitment of this species. Seed banks for this species have been detected during monitoring in Gladstone Harbour, and investigations into the viability of these seedbanks is currently being undertaken by the seagrass monitoring team.

Multiple years of high rainfall, high river flows and cyclone activity in the Gladstone region may have reduced the resilience and capacity for recovery in Gladstone Harbour’s seagrass communities. However, seagrasses in Queensland have a demonstrated ability to recover from past impacts. Condition improvements recorded for some meadows suggest that the seagrasses in Gladstone Harbour remain resilient.


Corals Results

What Was Measured And Why

The coral indicator group consists of three sub-indicators: coral cover (hard and soft), macroalgal cover and juvenile density.

Coral cover (hard and soft)

Healthy coral communities are those which have sufficient recruitment and colony growth to replace losses resulting from disturbances and environmental limitations. High coral cover indicates that a large brood-stock is available and this increases the potential of other reefs in the vicinity to recover from disturbance. Additionally, high coral cover contributes to the structural complexity of a reef which can increase its biodiversity by providing habitat for fish and other marine organisms.

Critical values for coral cover have been developed through the Australian Institute of Marine Science Reef Plan Marine Monitoring Program (MMP) and fitted to the Gladstone Harbour Report Card grading classifications by setting 40% coral cover at the C/D threshold. The upper bound for this indicator, equivalent to a score of 1.00 is 90% coral cover and the lower bound is coverage of 0%.

Macroalgal cover

Macroalgae can inhibit coral recruitment and growth by increased competition for space, shading and by changing the micro-environment. Once established, macroalgae occupy space that might otherwise be available for coral, and shade the coral, reducing the light available for the coral’s photosynthetic symbiotic algae (the dinoflagellate Zooxanthellae). Macroalgae include large fleshy species belonging to the Rhodophyta (red algae), Phaeophyta (brown algae) and Chlorophyta (green algae).

As macroalgae have a negative effect on coral, high coverage of macroalgae is indicative of poor coral reef condition and low macroalgal cover is indicative of good condition. Critical values for macroalgal cover were developed through the MMP, and fitted to the Gladstone Harbour Report Card grading scheme. A baseline of 14% macroalgal cover was set at the C/D threshold for coral communities in Gladstone Harbour. A macroalgal cover of 20% was set to a score of 0.00 (E) and a macroalgal cover of 5% was set to a score of 1.00 (A).

Juvenile coral density

Recovery of coral reefs from disturbances such as flooding, cyclones, thermal bleaching or outbreaks of crown-of-thorns starfish is dependent on the recruitment of new coral colonies and regeneration of existing colonies. The number of juvenile colonies (<10cm) present at a reef can be negatively affected by poor water quality; particularly elevated concentrations of nutrients, agrichemicals and high turbidity. High rates of sediment deposition will also negatively impact the number of juvenile colonies observed. Hence juvenile coral density can provide an indication of a reef’s potential for recovery from disturbance given the current conditions.

Thresholds for juvenile coral density are based on the MMP thresholds. These thresholds were set based on the densities of juvenile colonies recorded over four years of MMP monitoring (2005 – 2009). That monitoring determined the mean density of juvenile corals for inshore reefs at sites 2m below the Lowest Astronomical Tide to be about 7.7 juvenile corals per square metre of available substrate. For this study, the scores of 0.00 and 1.00 were set at the 10th and 90th percentiles of the distribution, or 1 and 16 juvenile colonies per square meter, respectively.

What Do The Coral Results Mean?

The coral communities in Gladstone Harbour are currently in very poor condition, with the available information strongly suggesting that the floods of 2011 and 2013 have impacted the coral communities across the harbour.

Freshwater runoff in flood plumes is a recognised cause of coral mortality owing to reduced salinity levels, although other factors associated with flooding can also have adverse effects. Major flooding of the Boyne and Calliope rivers, a result of heavy rainfalls associated with Tropical Cyclone Oswald in January 2013, temporarily lowered salinity levels within Gladstone Harbour. For a period of approximately three days from 27 to 29 January 2013, salinity levels remained below 20 psu at a depth of 0.75m, with a minimum level of less than 5 psu on 28 January. These low salinities, and similar low salinities in 2011, are likely to have caused high levels of mortality of corals within the harbour.

The loss of coral cover caused by freshwater plumes from flooding is not limited to Gladstone Harbour. Flooding in the Fitzroy River caused severe mortality of corals in Keppel Bay in 1991 and 2011. While the flooding almost certainly had severe effects on Gladstone’s coral communities, this does not preclude the possibility that other factors may have also contributed to the current poor condition of corals in Gladstone Harbour. The Great Barrier Reef Report Card 2014 reported that coral reefs in the Fitzroy region remained in very poor condition for at least two years following multiple disturbances.

The very low proportion of juvenile coral colonies in the 5 – 10cm size class (> 2 years old) across the surveyed reefs indicated low settlement and/or survival of juveniles spawned in late 2012. Conversely the numbers of juvenile coral colonies in the <2cm and 2 – 5 cm classes indicated that conditions for the settlement and survival of juveniles may have improved since then.

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Seagrass Results

Meadow ID Biomass Area Species Composition Overall Meadow Score Overall Zone Score
21 0.15 0.74 0.62 0.15 0.15

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Seagrass Results

Meadow ID Biomass Area Species Composition Overall Meadow Score Overall Zone Score
5.8

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Seagrass Results

Meadow ID Biomass Area Species Composition Overall Meadow Score Overall Zone Score
4 0.85 0.42 0.85 0.42 0.51
5 0.53 0.41 0.66 0.41 0.51
6 0.67 0.83 0.67 0.67 0.51
7 0.53 0.68 1.00 0.53 0.51
8 0.66 0.60 0.35 0.35 0.51
52-57 0.67 0.94 0.88 0.67 0.51

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Seagrass Results

Meadow ID Biomass Area Species Composition Overall Meadow Score Overall Zone Score
0.75

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Seagrass Results

Meadow ID Biomass Area Species Composition Overall Meadow Score Overall Zone Score
58 0.41 0.96 0.75 0.41 0.41

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Seagrass Results

Meadow ID Biomass Area Species Composition Overall Meadow Score Overall Zone Score
7.71

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Seagrass Results

Meadow ID Biomass Area Species Composition Overall Meadow Score Overall Zone Score
43 0.58 0.69 0.85 0.58 0.56
48 0.58 0.54 0.61 0.54 0.56

Corals Results

The 2015 Gladstone Harbour Report Card scores for the Mid Harbour are based on data collected from four reefs: Facing Island Reef 2, Farmers Reef, Manning Reef and Rat Island.

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Seagrass Results

Meadow ID Biomass Area Species Composition Overall Meadow Score Overall Zone Score
60 0.52 0.96 1.00 0.52 0.52

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Seagrass Results

Meadow ID Biomass Area Species Composition Overall Meadow Score Overall Zone Score
3.62

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Seagrass Results

Meadow ID Biomass Area Species Composition Overall Meadow Score Overall Zone Score
176.97

Corals Results

The 2015 Gladstone Harbour Report Card scores for the Outer Harbour zone are based on data collected from two reefs: Seal Rocks North and Seal Rocks South.

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Seagrass Results

Meadow ID Biomass Area Species Composition Overall Meadow Score Overall Zone Score
18.98

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Seagrass Results

Meadow ID Biomass Area Species Composition Overall Meadow Score Overall Zone Score
94 0.42 0.92 0.84 0.42
96 0.38 0.71 0.56 0.38
104 0.55 0.96 0.68 0.55

  Connectivity

Why It Was Included In Report Card

The connectivity of water bodies is an important driver of productivity in marine ecosystems and helps to maintain ecosystem function. Hydrological connectivity contributes to the health of habitats such as seagrass beds, mangroves and coral reefs within Gladstone Harbour by cycling nutrients, facilitating biological and genetic connectivity and by diluting and flushing of contaminants. However connectivity between contaminant inputs (e.g., from industrial discharges) and vulnerable habitats (e.g., seagrass beds) can also have negative effects on harbour health. The development of shipping channels, land reclamation and coastline armouring also have the potential to alter connectivity within the harbour.

A high resolution hydrodynamic model that links to the Great Barrier Reef eReefs model was used to calculate connectivity scores for the report card.

How Connectivity Was Calculated

The zone level connectivity was assessed using three indicators: flushing rate, ecological connectivity and contaminant connectivity. Each of these three indicators was assessed by tracking the movement of virtual particles in a 3D hydrodynamic model of Gladstone Harbour. The model outputs for the current year were then compared to model outputs over a four year baseline period (2010 – 2014) to derive a score for each indicator. In each model run, 2000 neutrally buoyant ‘particles’ were randomly seeded throughout the virtual water column in each zone at 20 day intervals.

Flushing rate

Flushing rate is a measure of water exchange throughout Gladstone Harbour. The flushing rate indicator was calculated for each 20 day re-seeding by plotting the number of particles remaining in a zone over time and calculating the time until only 36.8% of particles remained.

Ecological connectivity

Ecological connectivity is a measure of water exchange between spawning grounds and nursery areas for iconic species such as barramundi, bream and mud crab.

The ecological connectivity score is based on the modelled movement of virtual particles between zones for each of the 20 day re-seedings. Movement of particles into a zone, weighted by the number of habitats in that zone, provides a relative measure of how favourable the system connectivity is for recruitment to habitats within that zone. The movement of particles out of a zone into other zones, weighted by the number of identified key spawning grounds in each, provides a relative measure of how favourable the system connectivity was to the dispersal of eggs and larvae from the initial zone.

Contaminant connectivity

The contaminant connectivity indicator is a measure of the potential of contaminants to move to other parts of Gladstone Harbour from an input source. This indicator is based on annual loads of toxic substances discharged into the waterways for four harbour zones; Western Basin, Inner Harbour, Calliope Estuary and South Trees Inlet; as reported to the National Pollutant Inventory (www.npi.gov.au). As these figures are reported annually (pollutant loads for the 2014-15 will be reported in January 2016) the previous year of data is used as the best available estimate of the current year’s loads. A constant annual background load was also added to all other zones.

The contaminant connectivity score is based on the movement of particles out of a zone weighted with a zone score based on the annual load of pollutants multiplied by the toxicity of those pollutants to aquatic organisms.

What Does It Mean?

In 2014-15, flushing rate and contaminant connectivity both tended to score highly, while ecological connectivity tended to score poorly. This combination indicates that particles were rapidly flushed out of their starting zone, but were not necessarily transported around a large number of other harbour zones. Particles were more likely to be transported quite rapidly out of the harbour, so that high flushing rate would not lead to contaminants affecting other zones, but would lead to eggs and larvae being washed out of the harbour.

Such a scenario provides reduced opportunity for both contamination of other zones and larval recruitment to nursery areas in other zones. Hence the wide range of scores achieved in 2014-15 were largely due to changes in water circulation rather than changes in contaminant loads or habitat distributions.

Connectivity scores for the 2015 Gladstone Harbour Report Card were calculated using a statistical technique known as bootstrapping. This method provides scores that approximate the arithmetic mean score and provides estimates of the variability in the data. The scores calculated by bootstrapping will frequently differ from the arithmetic mean scores, as presented in Condie et al. (2015).

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Connectivity Results

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Connectivity Results

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Connectivity Results

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Connectivity Results

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Connectivity Results

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Connectivity Results

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Connectivity Results

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Connectivity Results

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Connectivity Results

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Connectivity Results

Grading system
A
Very good (0.85-1.00)
B
Good (0.65-0.84)
C
Satisfactory (0.50-0.64)
D
Poor (0.25-0.49)
E
Very poor (0.00-0.24)
 
Data not available

Connectivity Results