The accumulation of floating anthropogenic debris in marine and coastal areas has environmental, economic, aesthetic, and human health impacts. Until now, modelling the transport of such debris has largely been restricted to the large-scales of open seas. We used oceanographic modelling to identify potential sites of debris accumulation along a rugged coastline with headlands, islands, rocky coasts and beaches. Our study site was the Great Barrier Reef World Heritage Area that has an emerging problem with debris accumulation. We found that the classical techniques of modelling the transport of floating debris models are only moderately successful due to a number of unknowns or assumptions, such as the value of the wind drift coefficient, the variability of the oceanic forcing and of the wind, the resuspension of some floating debris by waves, and the poorly known relative contribution of floating debris from urban rivers and commercial and recreational shipping. Nevertheless the model was successful in reproducing a number of observations such as the existence of hot spots of accumulation. The orientation of beaches to the prevailing wind direction affected the accumulation rate of debris. The wind drift coefficient and the exact timing of the release of the debris at sea affected little the movement of debris originating from rivers but it affected measurably that of debris originating from ships. It was thus possible to produce local hotspot maps for floating debris, especially those originating from rivers. Such modelling can be used to inform local management decisions, and it also identifies likely priority research areas to more reliably predict the trajectory and landing points of floating debris.

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Most coral reef fishes have a pelagic larval stage before recruiting to reefs. The survival of larvae and their subsequent recruitment can drive the dynamics of reef populations. Here we show that the recruitment of the snapper Lutjanus carponotatus to One Tree Island in the Capricorn Bunker Group, in the southern Great Barrier Reef, was highly variable over 23 years. We predicted that the currents in the Capricorn Bunker Group, including their wind driven components and the Capricorn Eddy (a nearby transient oceanic eddy), would affect patterns of recruitment. A biophysical model was used to investigate this prediction. L. carponotatus were collected from One Tree Island and the dates when they were in the plankton as larvae were determined from their otoliths. The winds present during the pelagic phases of the fish were examined; they were found to have survived either longshore (SSE) winds that induced little cross shelf movement in the larval plume or cross shelf (ENE) winds that induced little longshore movement. The unidirectional transportation of the larval plume in these conditions was favorable for recruitment as it kept the plume concentrated in the Capricorn Bunker Group. These winds were more prevalent in the periods of peak L. carponotatus production that preceded high recruitment. Dispersal under average winds (6.2 m s −1 from the prevailing ESE) and strong winds (velocity 1.5 times average), with and without the Capricorn Eddy, was also modeled. Each of these combinations were less favorable for recruitment than the longshore and cross shelf winds larval L. carponotatus survived before reaching OTI. The larval plume was comparatively less concentrated in the Capricorn Bunker Group under average winds. Strong winds transported the larval plume far longshore, to the NW, away from the Capricorn Bunker Group, while the Capricorn Eddy transported larvae seaward into oceanic waters. Larval swimming could counteract these dispersive forces; however, significant dispersion had occurred before larvae developed strong swimming and orientation abilities. This study provides a physical proxy for the recruitment of snapper. Further, we have demonstrated that great insights into recruitment variability can be gained through determining the specific conditions experienced by survivors.

Transgenerational marking enables mass-marking of larval fishes via transmission of enriched stable isotopes from mother to offspring, but potential impacts on the resultant progeny are poorly understood. We injected enriched stable isotopes ( 137 Ba and 87 Sr) into female purple-spotted gudgeon, Mogurnda adspersa, to produce multiple batch markers and examined larval morphology at hatch as well as survival and growth to 31 days posthatch in marked and unmarked offspring. Transgenerational marking had minimal effects on larval growth and survival, whereas body depth at hatch was significantly reduced in marked larvae. A meta-analysis of transgenerational marking effects on larval morphology at hatch and growth rates across multiple fish species found a nonsignificant positive effect of enriched stable barium isotopes on larval morphology at hatch, but a significant negative effect on growth. There were no significant effects of strontium on morphology or growth. Meta-regression analysis revealed that larval size at hatch increased with the dose of injected stable barium isotopes, but this result should be interpreted cautiously. Because of high levels of between-study heterogeneity, we caution against assuming there are no effects of transgenerational marking on fish offspring; any such effects should be validated and incorporated into transgenerational marking studies of fish dispersal.Résumé : Si la méthode de marquage transgénérationnel permet le marquage d'un grand nombre de larves de poisson par la transmission d'isotopes stables enrichis de la mère à sa progéniture, ses impacts potentiels sur cette progéniture demeurent mal compris. Nous avons injecté des isotopes stables enrichis ( 137 Ba et 87 Sr) dans une femelle de Mogurnda adspersa pour produire différents marqueurs de lot et avons examiné la morphologie, la survie et la croissance de larves marquées et non marquées 31 jours après leur éclosion. Si le marquage transgénérationnel a eu peu d'effets sur la croissance et la survie des larves, la profondeur du corps au moment de l'éclosion était significativement plus faible pour les larves marquées. Une méta-analyse des effets du marquage transgénérationnel sur la morphologie des larves à l'éclosion et les taux de croissance pour différentes espèces de poisson a révélé un effet positif non significatif sur la morphologie des larves à l'éclosion, mais un effet négatif significatif sur la croissance, attribuable à l'enrichissement des isotopes stables de baryum. Aucun effet significatif du strontium sur la morphologie ou la croissance n'a été décelé. L'analyse de méta-régression a révélé que la taille des larves à l'éclosion augmentait parallèlement à la dose d'isotopes stables de baryum injectée, mais ce résultat devrait être interprété avec prudence. En raison des degrés élevés d'hétérogénéité entre les études, il est recommandé de ne pas présumer que le marquage transgé-nérationnel n'a aucun effet sur la progéniture de poisson, la présence de tels effets devant préalablement être validée, puis incorporée ...

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