Combining in-situ water quality and remotely sensed data across spatial and temporal scales to measure variability in wet season chlorophyll-a: Great Barrier Reef lagoon (Queensland, Australia)

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.

Download Full-text

Circulation in the Great Barrier Reef Lagoon using numerical tracers and in situ data

Continental Shelf Research ◽

10.1016/j.csr.2006.11.020 ◽

2007 ◽

Vol 27 (6) ◽

pp. 757-778 ◽

Cited By ~ 56

Author(s):

John L. Luick ◽

Luciano Mason ◽

Thomas Hardy ◽

Miles J. Furnas

Keyword(s):

Great Barrier Reef ◽

Barrier Reef ◽

Reef Lagoon ◽

In Situ Data

Download Full-text

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

Marine and Freshwater Research ◽

10.1071/mf9880019 ◽

1988 ◽

Vol 39 (1) ◽

pp. 19 ◽

Cited By ~ 10

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.

Download Full-text

Effect of Trichodesmium Blooms on Water Quality in the Great Barrier Reef Lagoon

Marine Pelagic Cyanobacteria: Trichodesmium and other Diazotrophs ◽

10.1007/978-94-015-7977-3_18 ◽

1992 ◽

pp. 273-287 ◽

Cited By ~ 2

Author(s):

G. B. Jones

Keyword(s):

Water Quality ◽

Great Barrier Reef ◽

Barrier Reef ◽

Reef Lagoon

Download Full-text

Exposure of inner-shelf reefs to nutrient enriched runoff entering the Great Barrier Reef Lagoon: Post-European changes and the design of water quality targets

Marine Pollution Bulletin ◽

10.1016/j.marpolbul.2006.05.009 ◽

2006 ◽

Vol 52 (11) ◽

pp. 1467-1479 ◽

Cited By ~ 92

Author(s):

Scott Wooldridge ◽

Jon Brodie ◽

Miles Furnas

Keyword(s):

Water Quality ◽

Great Barrier Reef ◽

Barrier Reef ◽

Inner Shelf ◽

Reef Lagoon

Download Full-text

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

Marine and Freshwater Research ◽

10.1071/mf06236 ◽

2007 ◽

Vol 58 (4) ◽

pp. 342 ◽

Cited By ~ 117

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.

Download Full-text

Marine microbial communities of the Great Barrier Reef lagoon are influenced by riverine floodwaters and seasonal weather events

PeerJ ◽

10.7717/peerj.1511 ◽

2016 ◽

Vol 4 ◽

pp. e1511 ◽

Cited By ~ 28

Author(s):

Florent E. Angly ◽

Candice Heath ◽

Thomas C. Morgan ◽

Hemerson Tonin ◽

Virginia Rich ◽

...

Keyword(s):

Water Quality ◽

Great Barrier Reef ◽

Microbial Communities ◽

River Mouth ◽

Environmental Parameters ◽

River System ◽

Rrna Gene ◽

Barrier Reef ◽

Wet Season ◽

Marine Microbial Communities

The role of microorganisms in maintaining coral reef health is increasingly recognized. Riverine floodwater containing herbicides and excess nutrients from fertilizers compromises water quality in the inshore Great Barrier Reef (GBR), with unknown consequences for planktonic marine microbial communities and thus coral reefs. In this baseline study, inshore GBR microbial communities were monitored along a 124 km long transect between 2011 and 2013 using 16S rRNA gene amplicon sequencing. Members of the bacterial orders Rickettsiales (e.g., Pelagibacteraceae) and Synechococcales (e.g.,Prochlorococcus), and of the archaeal class Marine Group II were prevalent in all samples, exhibiting a clear seasonal dynamics. Microbial communities near the Tully river mouth included a mixture of taxa from offshore marine sites and from the river system. The environmental parameters collected could be summarized into four groups, represented by salinity, rainfall, temperature and water quality, that drove the composition of microbial communities. During the wet season, lower salinity and a lower water quality index resulting from higher river discharge corresponded to increases in riverine taxa at sites near the river mouth. Particularly large, transient changes in microbial community structure were seen during the extreme wet season 2010–11, and may be partially attributed to the effects of wind and waves, which resuspend sediments and homogenize the water column in shallow near-shore regions. This work shows that anthropogenic floodwaters and other environmental parameters work in conjunction to drive the spatial distribution of microorganisms in the GBR lagoon, as well as their seasonal and daily dynamics.

Download Full-text

Inter-annual variability of wet season freshwater plume extent into the Great Barrier Reef lagoon based on satellite coastal ocean colour observations

Marine Pollution Bulletin ◽

10.1016/j.marpolbul.2012.02.022 ◽

2012 ◽

Vol 65 (4-9) ◽

pp. 210-223 ◽

Cited By ~ 62

Author(s):

Thomas Schroeder ◽

Michelle J. Devlin ◽

Vittorio E. Brando ◽

Arnold G. Dekker ◽

Jon E. Brodie ◽

...

Keyword(s):

Great Barrier Reef ◽

Coastal Ocean ◽

Barrier Reef ◽

Ocean Colour ◽

Wet Season ◽

Reef Lagoon ◽

Annual Variability ◽

Freshwater Plume

Download Full-text

Review and conceptual models of agricultural impacts and water quality in waterways of the Great Barrier Reef catchment area

Marine and Freshwater Research ◽

10.1071/mf15301 ◽

2017 ◽

Vol 68 (1) ◽

pp. 1 ◽

Cited By ~ 29

Author(s):

Aaron M. Davis ◽

Richard G. Pearson ◽

Jon E. Brodie ◽

Barry Butler

Keyword(s):

Water Quality ◽

Great Barrier Reef ◽

Catchment Area ◽

Conceptual Models ◽

Base Flow ◽

Barrier Reef ◽

Wet Season ◽

Management Options ◽

Fresh Waters ◽

Quality Risk

Adequate conceptual frameworks that link land use to water quality and ecosystem health are lacking for tropical and subtropical freshwater systems, so we review here extensive water-quality research undertaken in the Great Barrier Reef catchment area (GBRCA) and present conceptual models synthesising the dynamics of agricultural pollutants and their ecological effects. The seasonal flow regime defines the following key periods of water-quality risk over the annual hydrological cycle for diverse GBRCA ecosystems: initial ‘pre-flush’ flows during the transition from the dry to the wet season; early wet-season ‘first flush’ flows; peak wet-season flood flows; and sustained base flow or periods of disconnection during the dry season. The level of seasonal contrast varies from the perennial systems of the wet tropics to the intermittent systems of the dry tropics. Major water-quality stressors may be catchment scale (e.g. in streams draining broad-scale agriculture) or more localised (e.g. cattle access, irrigation tail water). Water-quality stressors such as ammonia toxicity and hypoxia (due to organic or nutrient run-off and enhanced plant productivity) are of low relevance to downstream GBR ecosystems but are major threats to fresh waters. Similarly, whereas high contaminant loads in wet-season floods present the highest water-quality risk to marine ecosystems, the greatest risk in fresh waters is often from acute contamination during early wet-season ‘pre-flush’ flows into lentic waters, or continuous input of contaminants over long periods of base flow. Because of differences in the nature of risk periods, water-quality threats and pollutant-delivery mechanisms, the benefits of different management options to improve water quality can also differ among freshwater habitats and between freshwater and marine environments.

Download Full-text