Spatial and temporal patterns of near-surface chlorophyll a in the Great Barrier Reef lagoon

2007 ◽  
Vol 58 (4) ◽  
pp. 342 ◽  
Author(s):  
J. Brodie ◽  
G. De'ath ◽  
M. Devlin ◽  
M. Furnas ◽  
M. Wright
Keyword(s):  
Great Barrier Reef ◽  
Chlorophyll A ◽  
Agricultural Development ◽  
Monitoring Program ◽  
Barrier Reef ◽  
Spatial And Temporal Patterns ◽  
Wet Season ◽  
Near Surface ◽  
Nutrient Delivery ◽  
Inshore Waters

Surface chlorophyll a concentrations in the Great Barrier Reef (GBR) lagoon were monitored at individual stations for periods of 6 to 12 years. The monitoring program was established to detect spatial and temporal changes in water quality resulting from increased loads of nutrients exported from the catchments adjoining the GBR. Sampling occurred monthly at up to 86 sites that were located in transects across the width of the continental shelf. In the central and southern GBR (16–21°S), there was a persistent cross-shelf chlorophyll a gradient, with higher concentrations near the coast. No cross-shelf gradient was observed in the far northern GBR (12–15°S). Mean chlorophyll a concentrations in the far northern GBR (0.23 µg L–1) were less than half those in the south and central GBR (0.54 µg L–1). Chlorophyll a varied seasonally within regions, with mean summer-wet season (December–April) concentrations ~50% greater than those in the winter-dry season (May–November). Sub-annual, inter-annual and event-related variations in chlorophyll a concentrations were observed in several zones. Multi-year patterns in concentrations suggest that relatively short (5–8 years) time series may give spurious estimates of secular trends. Higher chlorophyll a concentrations in inshore waters south of 16°S were most likely related to the levels of river nutrient delivery associated with agricultural development on adjacent catchments.

Turbidity in the northern Great Barrier Reef lagoon in the wet season, March 1989

1994 ◽  
Vol 45 (4) ◽  
pp. 585 ◽  
Author(s):  
LJ Hamilton
Keyword(s):  
Great Barrier Reef ◽  
Attenuation Coefficient ◽  
Quantitative Relation ◽  
Barrier Reef ◽  
Wet Season ◽  
Secchi Disc ◽  
Reef Lagoon ◽  
Secchi Disc Depth ◽  
Beam Attenuation ◽  
Beam Attenuation Coefficient

In 1989, a typical wet season was experienced in northern Queensland, with low winds and long calm periods. Turbidity in upper waters of the Great Barrier Reef lagoon broadly had a simple distribution that could be modelled from bottom depth contour values alone, without introducing wind speed or bottom type. In the absence of major storm and cyclone events, this result appears to be general, based on the similarity between March 1989 survey data and Secchi disc climatology. The simple distribution arises because the main turbidity sources are riverine discharges, with little entrainment of bottom sediment into the upper column, except in shallower waters. Fresh, highly turbid riverine influxes are generally confined close inshore, with salinity and Secchi contours parallel to shore, forming cross-shelf gradients. A semi-quantitative relation was found between sea surface colour and Secchi disc depth. Examination of nephelometric turbidity stratification showed that satellite and Secchi data should be more useful for subsurface turbidity inference between Cooktown and Innisfail than in Princess Charlotte Bay, with horizontal and vertical stratifications, respectively, observed in those areas. Highest nephelometric turbidity was seen from Cooktown to Innisfail. Beam attenuation coefficient in oceanic waters outside the reef appeared to be dominated by absorption, with lagoon waters influenced by scattering. A method is suggested to enable approximate transfer of beam attenuation coefficient measured by a transmissometer operating at a single wavelength to beam attenuation coefficient at other wavelengths, using coincident measurements of Secchi disc depths made with filters.

Patterns of recruitment of polychaetes to coral substrates at Lizard Island, Great Barrier Reef - an experimental approach

1982 ◽  
Vol 33 (6) ◽  
pp. 1029 ◽  
Author(s):  
P Hutchings ◽  
A Murray
Keyword(s):  
Great Barrier Reef ◽  
Similar Pattern ◽  
Experimental Approach ◽  
Temporal Patterns ◽  
The Other ◽  
Barrier Reef ◽  
Spatial And Temporal Patterns ◽  
Lizard Island

The spatial and temporal patterns of recruitment of seven species in six families of polychaete to coral substrates at two sites at Lizard Island, Great Barrier Reef, are described. Four species exhibit similar patterns of recruitment to both sites, and another species exhibits a similar pattern to both sites but with different intensities. The other two species recruit in different patterns to the two sites. All species exhibit peaks of recruitment, most during mid-summer. Recruitment during 1977 was significantly greater than during 1976 for five of the seven species. Factors responsible for this variation and the patchiness of successful settlement are discussed.

Dependance of phytoplankton chlorophyll on bottom resuspension in Cleveland Bay, northern Queensland

1981 ◽  
Vol 32 (6) ◽  
pp. 981 ◽  
Author(s):  
TA Walker
Keyword(s):  
Great Barrier Reef ◽  
Bottom Sediment ◽  
Chlorophyll A ◽  
Water Depth ◽  
Inverse Correlation ◽  
Barrier Reef ◽  
Secchi Disc ◽  
Secchi Disc Depth ◽  
The Mean ◽  
Strong Inverse Correlation

In relatively shallow regions of the lagoon of the central Great Barrier Reef. phytoplankton chlorophyll a concentrations are dependent on intermittent resuspension of bottom sediment by wind-generated waves. This results in a strong inverse correlation between chlorophyll a levels and transparency over a period of time. Bottom resuspension and resettling cause a mide transparency range to occur at any given station. but the mean Secchi disc depth increases linearly with water depth across the lagoon.

Wet season fine sediment dynamics on the inner shelf of the Great Barrier Reef

2008 ◽  
Vol 77 (4) ◽  
pp. 755-762 ◽  
Author(s):  
Eric Wolanski ◽  
Katharina E. Fabricius ◽  
Timothy F. Cooper ◽  
Craig Humphrey
Keyword(s):  
Great Barrier Reef ◽  
Fine Sediment ◽  
Sediment Dynamics ◽  
Barrier Reef ◽  
Wet Season ◽  
Inner Shelf

scholarly journals Can changes to pasture management reduce runoff and sediment loss to the Great Barrier Reef? The results of a 10-year study in the Burdekin catchment, Australia

2014 ◽  
Vol 36 (1) ◽  
pp. 67 ◽  
Author(s):  
Rebecca Bartley ◽  
Jeff P. Corfield ◽  
Aaron A. Hawdon ◽  
Anne E. Kinsey-Henderson ◽  
Brett N. Abbott ◽  
...  
Keyword(s):  
Great Barrier Reef ◽  
Ground Cover ◽  
Bank Erosion ◽  
Grazing Management ◽  
Barrier Reef ◽  
Wet Season ◽  
Sediment Yields ◽  
Hill Slope ◽  
Sediment Loss ◽  
Catchment Runoff

Excess sediments from agricultural areas are having a detrimental impact on the Great Barrier Reef, and threaten the long-term viability of rangeland grazing. Changes to grazing management have been promoted as a mechanism for reducing excess sediment loss from grazed rangelands. This paper summarises the results of a 10-year study (2002–11) on a property in the Burdekin catchment that investigated the role of reduced stocking rates and rotational wet season resting on hill-slope and catchment runoff and sediment yields. Ground cover and pasture biomass were evaluated using on-ground surveys and remote sensing. During this study, average ground cover increased from ~35 to ~80% but pasture biomass was low due to the dominance of Bothriochloa pertusa (77% of composition). The percentage of deep-rooted perennial species increased from ~7% of pasture composition in 2002 to ~15% in 2011. This is still considerably lower than the percentage that occupied this property in 1979 (~78%). The increased ground cover resulted in progressively lower hill-slope runoff coefficients for the first event in each wet season, but annual catchment runoff did not respond significantly to the increasing ground cover during the study. Hill-slope and catchment sediment concentrations did decline with the increased ground cover, yet catchment sediment yields increased proportionally to annual runoff due to the contribution of sub-surface (scald, gully and bank) erosion. This study has demonstrated that changes to grazing management can reduce sediment concentrations leaving B. pertusa-dominated pastures, as B. pertusa is an effective controller of surface erosion. To further reduce the runoff that is fuelling gully and bank erosion, the proportion of deep-rooted native perennial grasses needs to be increased. It is argued that more than 10 years will be required to restore healthy eco-hydrological function to these previously degraded and low productivity rangelands. Even longer timescales will be needed to meet current targets for water quality.

Effect of terrestrial and marine humics on copper speciation in an estuary in the Great Barrier Reef Lagoon

1988 ◽  
Vol 39 (1) ◽  
pp. 19 ◽  
Author(s):  
GB Jones ◽  
FG Thomas
Keyword(s):  
Great Barrier Reef ◽  
Humic Substances ◽  
Coastal Waters ◽  
River Estuary ◽  
Barrier Reef ◽  
Wet Season ◽  
Reef Lagoon ◽  
Copper Speciation ◽  
High Concentrations ◽  
Monsoonal Season

Studies carried out over several years on a tropical estuary, the Ross River Estuary, have shown that copper speciation is influenced by both terrestrial and marine humic substances. While terrestrial humic substances are mobilized by high freshwater runoff in the monsoonal season, Trichodesmium blooms mobilize high concentrations of marine humics to the inshore zone and increase labile forms of copper. The marine humics are more soluble than the terrestrial humics and persist in coastal waters of the Great Barrier Reef lagoon for many months prior to the wet season.

Community and connectivity: summary of a community based monitoring program set up to assess the movement of nutrients and sediments into the Great Barrier Reef during high flow events

2001 ◽  
Vol 43 (9) ◽  
pp. 121-131 ◽  
Author(s):  
M. Devlin ◽  
J. Waterhouse ◽  
J. Brodie
Keyword(s):  
Great Barrier Reef ◽  
Monitoring Program ◽  
Agricultural Practices ◽  
Suspended Sediments ◽  
Life Forms ◽  
First Flush ◽  
Barrier Reef ◽  
Flood Events ◽  
Set Up ◽  
Extreme Flow

The Great Barrier Reef (GBR) system encompasses the largest system of corals and related life forms anywhere in the world. The health of this extensive system, particularly the inshore area, is dependent on the relationship between the GBR and adjacent coastal catchments. The major impact of agricultural practices on the GBR is the degradation of water quality in receiving (rivers) waters, caused by increased inputs of nutrients, suspended sediments and other pollutants. For the past three years, the Great Barrier Reef Marine Park Authority (GBRMPA) has been involved with the co-ordination of a river-monitoring program, specifically targeting the sampling of rivers during flood events. Representative sites were set up along two North Queensland rivers, the Russell-Mulgrave and Barron Rivers. This monitoring program is run in conjunction with the Queensland Department of Natural Resources' Waterwatch program. The program involves intensive sampling of first flush, extreme flow and post flood conditions over the two rivers. Extreme flow conditions are sampled over a limited time span (48 hours) with trained volunteers at 4-hour intervals. Concentrations measured in the flood events are dependent on landuse characteristic, and extent of flow. Concentrations of dissolved and particulate nutrients are higher if the extreme flow event is part of the first flush cycle. Concentrations of DIN and DIP measured before, during and after a major flood event suggest that there is a large storage of inorganic material within the Barron and Russell-Mulgrave agricultural subcatchments that move over a period of days, and perhaps weeks. This program created a forum in which GBRMPA liased with the Barron and Russell-Mulgrave community about the connectivity existing between the river and the Great Barrier Reef lagoon.

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