Multinational genetic connectivity identified in western Pacific hawksbill turtles, Eretmochelys imbricata

2018 ◽  
Vol 45 (4) ◽  
pp. 307 ◽  
Author(s):  
Ian Bell ◽  
Michael P. Jensen
Keyword(s):  
Great Barrier Reef ◽  
Conservation Management ◽  
Threat Assessment ◽  
Population Connectivity ◽  
Genetic Connectivity ◽  
Stock Structure ◽  
Barrier Reef ◽  
Long Distance ◽  
Eretmochelys Imbricata ◽  
Management Actions

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.

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
Keyword(s):  
Bayesian Network ◽  
Great Barrier Reef ◽  
Phytoplankton Biomass ◽  
Nutrient Management ◽  
Nitrogen Management ◽  
Catchment Management ◽  
Barrier Reef ◽  
Nitrogen Fertiliser ◽  
Management Actions ◽  
Reef Condition

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.

scholarly journals Not All Larvae Stay Close to Home: Insights into Marine Population Connectivity with a Focus on the Brown Surgeonfish (Acanthurus nigrofuscus)

2011 ◽  
Vol 2011 ◽  
pp. 1-12 ◽  
Author(s):  
Jeff A. Eble ◽  
Luiz A. Rocha ◽  
Matthew T. Craig ◽  
Brian W. Bowen
Keyword(s):  
Resource Planning ◽  
Reef Fishes ◽  
Population Connectivity ◽  
Genetic Connectivity ◽  
Dispersal Ability ◽  
Small Range ◽  
Long Distance ◽  
Larval Recruitment ◽  
Marine Population ◽  
Acanthurus Nigrofuscus

Recent reports of localized larval recruitment in predominately small-range fishes are countered by studies that show high genetic connectivity across large oceanic distances. This discrepancy may result from the different timescales over which genetic and demographic processes operate or rather may indicate regular long-distance dispersal in some species. Here, we contribute an analysis of mtDNA cytochromebdiversity in the widely distributed Brown Surgeonfish (Acanthurus nigrofuscus;N=560), which revealed significant genetic structure only at the extremes of the range (ΦCT=0.452;P<.001). Collections from Hawaii to the Eastern Indian Ocean comprise one large, undifferentiated population. This pattern of limited genetic subdivision across reefs of the central Indo-Pacific has been observed in a number of large-range reef fishes. Conversely, small-range fishes are often deeply structured over the same area. These findings demonstrate population connectivity differences among species at biogeographic and evolutionary timescales, which likely translates into differences in dispersal ability at ecological and demographic timescales. While interspecific differences in population connectivity complicate the design of management strategies, the integration of multiscale connectivity patterns into marine resource planning will help ensure long-term ecosystem stability by preserving functionally diverse communities.

scholarly journals Effects of trawling on sessile megabenthos in the Great Barrier Reef and evaluation of the efficacy of management strategies

2015 ◽  
Vol 73 (suppl_1) ◽  
pp. i115-i126 ◽  
Author(s):  
C. Roland Pitcher ◽  
Nick Ellis ◽  
William N. Venables ◽  
Ted J. Wassenberg ◽  
Charis Y. Burridge ◽  
...  
Keyword(s):  
Great Barrier Reef ◽  
Environmental Sustainability ◽  
Large Scale ◽  
Regional Scale ◽  
Regional Distribution ◽  
Dynamic Modelling ◽  
Barrier Reef ◽  
Worst Case ◽  
Management Actions ◽  
Management Interventions

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.

scholarly journals Asymmetric dispersal is a critical element of concordance between biophysical dispersal models and spatial genetic structure in Great Barrier Reef corals

2018 ◽  
Author(s):  
C Riginos ◽  
K Hock ◽  
AM Matias ◽  
PJ Mumby ◽  
MJH van Oppen ◽  
...  
Keyword(s):  
Gene Flow ◽  
Great Barrier Reef ◽  
Larval Dispersal ◽  
Coral Species ◽  
Spatial Genetic Structure ◽  
Critical Element ◽  
Barrier Reef ◽  
Long Distance ◽  
Biophysical Models ◽  
Asymmetric Dispersal

AbstractAimWidespread coral bleaching, crown-of-thorns seastar outbreaks, and tropical storms all threaten foundational coral species of the Great Barrier Reef, with impacts differing over time and space. Yet, dispersal via larval propagules could aid reef recovery by supplying new settlers and enabling the spread of adaptive variation among regions. Documenting and predicting spatial connections arising from planktonic larval dispersal in marine species, however, remains a formidable challenge.LocationThe Great Barrier Reef, AustraliaMethodsContemporary biophysical larval dispersal models were used to predict longdistance multigenerational connections for two common and foundational coral species (Acropora tenuisandAcropora millepora). Spatially extensive genetic surveys allowed us to infer signatures of asymmetric dispersal for these species and evaluate concordance against expectations from biophysical models using coalescent genetic simulations, directions of inferred gene flow, and spatial eigenvector modelling.ResultsAt long distances, biophysical models predicted a preponderance of north to south connections and genetic results matched these expectations: coalescent genetic simulations rejected an alternative scenario of historical isolation; the strongest signals of inferred gene flow were from north to south; and asymmetric eigenvectors derived from north to south connections in the biophysical models were significantly better predictors of spatial genetic patterns than eigenvectors derived from symmetric null spatial models.Main conclusionsResults are consistent with biophysical dispersal models yielding approximate summaries of past multigenerational gene flow conditioned upon directionality of connections. ForA. tenuisandA. millepora, northern and central reefs have been important sources to downstream southern reefs over the recent evolutionary past and should continue to provide southward gene flow. Endemic genetic diversity of southern reefs suggests substantial local recruitment and lack of long distance gene flow from south to north.

The hawksbill turtle, Eretmochelys imbricata, in Queensland: population structure within a southern Great Barrier Reef feeding ground.

1992 ◽  
Vol 19 (4) ◽  
pp. 489 ◽  
Author(s):  
CJ Limpus
Keyword(s):  
Great Barrier Reef ◽  
Carapace Length ◽  
Regression Equations ◽  
Barrier Reef ◽  
Growth Data ◽  
Eretmochelys Imbricata ◽  
Nesting Beaches ◽  
Hawksbill Turtles ◽  
Feeding Grounds

Hawksbill turtles, Eretmochelys imbricata, live at low density on coral reefs in the southern Great Barrier Reef. The biomass of the species on Heron Reef was estimated at 0.82 kg ha-1. This is equivalent to 3.34 turtles km-1. The nesting beaches used by these E. imbricata are unknown. However, within the Great Barrier Reef and Coral Sea region, no regular nesting by the species occurs within 1200 km of these reefal feeding grounds. E. imbricata take up long-term residence in these feeding grounds at a minimum curved carapace length of 35.0cm. The E. imbricata feeding over these reefs ranged in size from these small immatures up to adults with curved carapace length of 87.5cm, but the maturity ratio was very strongly biased toward immatures (maturity ratio=0.01 adults). The sex ratio of all size classes was significantly skewed in favour of females (2.57 : 1 females : male overall) while 2% of the turtles were identified as intersex. Growth data from these turtles indicate that they will be decades old at first breeding. A key for sexing and assessing reproductive maturity of E. imbricata is provided. Regression equations for converting between curved carapace length and other standard measures including straight carapace measures, weight, head length and width and plastron length are described.

scholarly journals Quantifying the environmental impact of a major coal mine project on the adjacent Great Barrier Reef ecosystems

2021 ◽  
Author(s):  
Antoine Saint-Amand ◽  
Alana Grech ◽  
Severine Choukroun ◽  
Emmanuel Hanert
Keyword(s):  
Great Barrier Reef ◽  
Coal Mine ◽  
Marine Species ◽  
Ocean Model ◽  
Barrier Reef ◽  
Dispersal Patterns ◽  
Long Distance ◽  
Sediment Dispersal ◽  
Seagrass Meadows ◽  
Sediment Types

A major coal mine project in Queensland, Australia, is currently under review. It is planned to be located about 10 km away from the Great Barrier Reef World Heritage Area (GBRWHA). Sediment dispersal patterns and their impact on marine ecosystems have not been properly assessed yet. Here, we simulate the dispersal of different sediment types with a high-resolution ocean model, and derive their environmental footprint. We show that sediments finer than 32 µm could reach dense seagrass meadows and a dugong sanctuary within a few weeks. The intense tidal circulation leads to non-isotropic and long-distance sediment dispersal patterns along the coast. Our results suggest that the sediments released by this project will not be quickly mixed but rather be concentrated where the most valuable ecosystems are located. If accepted, this coal mine could therefore have a far-reaching impact on the GBRWHA and its iconic marine species.

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