A Bayesian network model linking nutrient management actions in the Tully catchment (northern Queensland) with Great Barrier Reef condition

2010 ◽  
Vol 61 (5) ◽  
pp. 587 ◽  
Author(s):  
Will Shenton ◽  
Barry T. Hart ◽  
Jon Brodie

Correlating catchment management actions with improvements in the ecological condition of downstream coastal regions is challenging. We describe a Bayesian network (BN) model that predicts the effects of nitrogen-fertiliser management strategies in the Tully River catchment (northern Queensland) on the condition of inshore reefs of the Great Barrier Reef (GBR). The model consists of three linked submodels that relate sugarcane nitrogen management with runoff into the Tully River and nitrate concentration in the GBR lagoon, predicts phytoplankton biomass in the GBR lagoon from the nitrate inputs, and links the phytoplankton biomass with three marine influences to predict the probability of the reefs being dominated by coral (good) or macro-algae (bad). Four scenarios were modelled – current and the ‘six easy steps’ nitrogen management, and active and depleted algal grazing (herbivory) of the reef. The model predicts an increased probability of the reef being coral-dominated with current fertiliser practice and with active reef herbivory, with increased algal-dominance if reef herbivory is decreased. Introduction of a better nitrogen-fertiliser management with active herbivory resulted in an increased probability of coral dominance. This comparative-scenario analysis highlights the importance of both agricultural nutrient management practices and marine processes in predicting reef condition.

Author(s):  
Yu.I. Sorokin ◽  
P.Yu. Sorokin

The abundance, composition and metabolic activity of plankton were assessed in the Tribulation zone of the central Great Barrier Reef (16°–17°S). Wet phytoplankton biomass ranged in shallow reef waters from 30 to 70 mg m−3, and from 60 to 270 mg m−3in the deep lagoon and in the estuarine areas which are dominated by pico- and nano-algae. Wet bacterioplankton biomass varied from 70 to 290 mg m−3. Wet meroplankton biomass was less than 10 mg m−3. Wet daytime mesozooplankton biomass ranged from 100 to 300 mg m−3in the deep lagoon. In the estuarine area, it reached 400 to 1300 mg m−3and in the shallow inner lagoon of the Low Isles ring reef it varied from 10 to 30 mg m−3. Zooplankton density increased at night and was 3 to 5 fold greater in the deep lagoon, for about 2 orders of magnitude greater over the reef shallows and up to 3 orders of magnitude greater in mangrove habitats, due to the emergence of demersal components from the benthos. The biomass of zooplankton hidden in the benthic substrates during the day reached 10 to 40 g m−2. Pelagic primary production in the deep lagoon varied between 0.2 and 0.5 g C m−2 d−1. A calculation of the energy balance suggests that the basic energy source for heterotrophic plankton production in the deep lagoon is the organic matter exported from surrounding reef benthic communities and from mangroves. The trophic status of coral reef pelagic ecosystem might range from mesotrophic to eutrophic.


2015 ◽  
Vol 73 (suppl_1) ◽  
pp. i115-i126 ◽  
Author(s):  
C. Roland Pitcher ◽  
Nick Ellis ◽  
William N. Venables ◽  
Ted J. Wassenberg ◽  
Charis Y. Burridge ◽  
...  

Abstract A series of related research studies over 15 years assessed the effects of prawn trawling on sessile megabenthos in the Great Barrier Reef, to support management for sustainable use in the World Heritage Area. These large-scale studies estimated impacts on benthos (particularly removal rates per trawl pass), monitored subsequent recovery rates, measured natural dynamics of tagged megabenthos, mapped the regional distribution of seabed habitats and benthic species, and integrated these results in a dynamic modelling framework together with spatio-temporal fishery effort data and simulated management. Typical impact rates were between 5 and 25% per trawl, recovery times ranged from several years to several decades, and most sessile megabenthos were naturally distributed in areas where little or no trawling occurred and so had low exposure to trawling. The model simulated trawl impact and recovery on the mapped species distributions, and estimated the regional scale cumulative changes due to trawling as a time series of status for megabenthos species. The regional status of these taxa at time of greatest depletion ranged from ∼77% relative to pre-trawl abundance for the worst case species, having slow recovery with moderate exposure to trawling, to ∼97% for the least affected taxon. The model also evaluated the expected outcomes for sessile megabenthos in response to major management interventions implemented between 1999 and 2006, including closures, effort reductions, and protected areas. As a result of these interventions, all taxa were predicted to recover (by 2–14% at 2025); the most affected species having relatively greater recovery. Effort reductions made the biggest positive contributions to benthos status for all taxa, with closures making smaller contributions for some taxa. The results demonstrated that management actions have arrested and reversed previous unsustainable trends for all taxa assessed, and have led to a prawn trawl fishery with improved environmental sustainability.


2018 ◽  
Vol 45 (4) ◽  
pp. 307 ◽  
Author(s):  
Ian Bell ◽  
Michael P. Jensen

Context An understanding of the genetic stock structure of wide-ranging marine species is necessary for sound conservation management. Eretmochelys imbricata is Critically Endangered globally, but is among the least studied marine turtles. Reduced population sizes, its long-distance migratory nature between feeding and nesting habitats and poor understanding of its stock structure, biology and anthropogenic impact(s) pose challenges to developing effective conservation strategies for regional conspecifics. Aims Quantification of the population connectivity between specific feeding areas and regional nesting populations is needed for threat assessment and development of mitigation actions. Methods Here, we sequenced the mitochondrial DNA (mtDNA) of 91 immature and adult foraging E. imbricata individuals captured at the Howick Group of islands in the far-northern section of the Great Barrier Reef (nGBR), Queensland, Australia. We used a Bayesian mixed-stock analysis (MSA) approach to determine the contribution of nine regional genetically characterised breeding populations to this feeding aggregation. Key results The MSA estimated that a majority (83%; 95% CI = 70–92%) of feeding E. imbricata had originated from nesting beaches in the Bismarck–Solomon Sea region, whereas only 15% (95% CI = 6–25%) had originated from nGBR rookeries. International reproductive migrations were also corroborated by the return of 18 uniquely numbered titanium flipper tags that had been applied to E. imbricata found foraging in the Howick Group and had swum to rookeries within the Bismarck–Solomon Sea region. These 18 turtles represent 86% of all migration tag–recaptures from the Howick Group. Conclusions We postulate that recent increases in nesting populations within the Solomon Islands may be due to the high level of protection afforded to foraging turtles within the Great Barrier Reef. Implications An understanding of the connectivity between specific feeding areas and nesting populations is necessary to determine threats to animals over their entire life history and, therefore, allow the development of sound conservation management actions.


2014 ◽  
Vol 186 (12) ◽  
pp. 8527-8540 ◽  
Author(s):  
R. J. Beeden ◽  
M. A. Turner ◽  
J. Dryden ◽  
F. Merida ◽  
K. Goudkamp ◽  
...  

Coral Reefs ◽  
1990 ◽  
Vol 9 (1) ◽  
pp. 1-10 ◽  
Author(s):  
Miles J. Furnas ◽  
Alan W. Mitchell ◽  
Malvern Gilmartin ◽  
Noelia Revelante

2001 ◽  
Vol 43 (9) ◽  
pp. 203-211 ◽  
Author(s):  
J. Brodie ◽  
C. Christie ◽  
M. Devlin ◽  
D. Haynes ◽  
S. Morris ◽  
...  

Pollution of coastal regions of the Great Barrier Reef is dominated by runoff from the adjacent catchment. Catchment land-use is dominated by beef grazing and cropping, largely sugarcane cultivation, with relatively minor urban development. Runoff of sediment, nutrients and pesticides is increasing and for nitrogen is now four times the natural amount discharged 150 years ago. Significant effects and potential threats are now evident on inshore reefs, seagrasses and marine animals. There is no effective legislation or processes in place to manage agricultural pollution. The Great Barrier Reef Marine Park Act does not provide effective jurisdiction on the catchment. Queensland legislation relies on voluntary codes and there is no assessment of the effectiveness of the codes. Integrated catchment management strategies, also voluntary, provide some positive outcomes but are of limited success. Pollutant loads are predicted to continue to increase and it is unlikely that current management regimes will prevent this. New mechanisms to prevent continued degradation of inshore ecosystems of the Great Barrier Reef World Heritage Area are urgently needed.


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