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The North West Shelf (NWS) of Australia features extensive and globally significant fringing coral reef ecosystems with high levels of endemism and consequently has received significant conservation efforts in the form of Marine Parks. The shelf circulation on the NWS is dominated by the southwestward-flowing Holloway Current during austral autumn–winter and by the northeastward monsoonal currents during austral summer. Intraseasonal Oscillation and short-term wind variability also influence advection processes on the NWS. These circulation processes are likely to determine demographic inter-dependencies among reef systems in the region, but the extent and spatial variability of the inter-dependence are not well understood. In this study, we used a 3-dimensional, hydrostatic, primitive equations model, to simulate the shelf circulation on the NWS at 1 km horizontal resolution during 2004–2009. We then used a particle tracking model based on the shelf circulation model to simulate larval dispersal in a representative coral species, Acropora millepora, among the 3430 coral reefs on the NWS during its autumn mass spawning. Model results predicted that settling larvae typically reach suitable reef within 10 days of spawning, with a predominantly southwestward tendency of transport. There was significant spatial heterogeneity in larval settlements and the Dampier Archipelago areas seemed to be more isolated from the rest of the NWS. Year-to-year variations of larval dispersals were sensitive to the seasonal and intraseasonal variations of alongshore winds: mass spawning in late March would expose the Dampier Archipelago area to the Holloway Current onset, resulting in it being an occasional source region of larval supply for the rest of the NWS to the southwest; intraseasonal northeastward wind pulses coinciding with the mass larval spawning would bring larvae from coastal regions to the Dampier Archipelago on rare occasions. By aggregating the reefs into 47 subregions, we estimated that the mean rate of self-seeding within the subregions (as a proportion of total supply) was 22% (range from 99% to

A variety of techniques for measuring coral growth, a fundamental biological trait, have been used to improve our understanding of coral demographics. Remaining gaps and biases in this information, in combination with technological advances, led to the present study. We assessed the capacity of structure-from-motion (SfM) technology to build image mosaics (orthophotos) of ~6 × 8 m reef plots from which individual coral colonies could be identified in repeated annual surveys and colony planar area measured. We monitored Acropora, Pocilloporidae (specifically from the genera Stylophora and Seriatopora) and Platygyra colonies over 2 years. We compared growth measurements, as change in radius, from SfM orthophotos to the more traditional method of tagging and photographing individual coral colonies. We conclude that planar coral growth can be measured from SfM orthophotos, with clear advantages over tagging including large sample sizes, and speed and ease of surveying, albeit with some bias in the SfM method (growth estimates were 15% greater (~0.5 cm/year) from standard photos than from the SfM orthophotos). We documented mortality and growth rates in a high wave energy environment on the reef slope at Ningaloo Reef, Western Australia, where there were no existing coral growth or mortality estimates. The mean change in radial extension of Acropora colonies with no mortality was 2.92 ± 0.06 (SE, n = 572) cm year−1 across the pooled data set of standard and orthophotos, substantially lower than previous estimates on similar species from the region. The growth rate of Pocilloporidae was 3.54 ± 0.52 (SE, n = 12) cm year−1 for colonies with no mortality. Robust planar growth estimates were not obtained for Platygyra due to its morphology, but we report high survivorship of the colonies: 94% with no mortality as compared with 79% for Acropora and only 53% for Pocilloporidae. High sample sizes from the novel SfM methodology allowed us to demonstrate that Acropora growth rate was inversely linked to wave energy and coral size.

Data from 13 autonomous profiling BGC-Argo floats, equipped with biogeochemical and bio-optical sensors deployed between 2011 and 2016, were used to explore the potential of bio-optical methods to map deep biomass distribution in the Arabian Sea oxygen minimum zone (OMZ). Dissolved oxygen sensors revealed concentrations below 5 μmol kg−1 for much of the depth range between 200 and 400 m and below 1 μmol kg−1 in the centre of the OMZ, which is well below climatological values. Optical particle backscatter sensors revealed intensities within the upper OMZ that were nearly as high as within the euphotic zone. The distribution of these particulate scatterers was confined to oxygen concentrations below 1 μmol kg−1, with vertical distributions that exhibited maxima just below the top of the OMZ and decreased downward with similar attenuation to that expected for sinking organic matter. These distributions were very similar to those of nitrate deficits (ΔNO3) estimated from a float with an ultra-violet nitrate sensor (R2 = 0.54, p

Species' ranges are shifting globally in response to climate warming, with substantial variability among taxa, even within regions. Relationships between range dynamics and intrinsic species traits may be particularly apparent in the ocean, where temperature more directly shapes species' distributions. Here, we test for a role of species traits and climate velocity in driving range extensions in the ocean-warming hotspot of southeast Australia. Climate velocity explained some variation in range shifts, however, including species traits more than doubled the variation explained. Swimming ability, omnivory and latitudinal range size all had positive relationships with range extension rate, supporting hypotheses that increased dispersal capacity and ecological generalism promote extensions. We find independent support for the hypothesis that species with narrow latitudinal ranges are limited by factors other than climate. Our findings suggest that small-ranging species are in double jeopardy, with limited ability to escape warming and greater intrinsic vulnerability to stochastic disturbances.

Puerulus settlement in the western rock lobster fishery has remained below average for seven consecutive years (2006/2007–2012/2013), with 2008/2009 being the lowest in over 40 years. Examination of the timing of the start of spawning using fishery-independent data since the mid-2000s indicated that spawning has been occurring earlier. The low settlement appears related to higher water temperatures at the time of the onset of spawning (October) since the mid-2000s. Statistical analysis shows that the most (71%) of the variation in puerulus settlement was explained by the timing of spawning, storm activity during autumn/spring, and offshore water temperatures in February. Earlier spawning may cause a mismatch with other environmental factors such as peaks in ocean productivity and/or storms that assist the larvae return to the coast and offshore water temperatures that help the early stage larval growth. These variables produced a plausible hypothesis to explain the decline in puerulus settlement for these 7 years, including the recruitment failure of 2008/2009. They also predicted the substantial improvement in settlement for 2013/2014. Egg production levels did not to have a significant relationship with puerulus settlement levels after taking environmental variables into account. Further verification with additional years is required to see whether this relationship is maintained. Global climate change may influence these environmental factors: the timing of spawning is influenced by water temperature and there has been a reduced trend of autumn to spring storms off southwest Australia.

18 pages, 10 figures, 5 tables, supplementary material in https://doi.org/10.3354/meps09730, Empirical and modelled data were used to examine the influence of the Leeuwin Current on larval fish assemblages along the Western Australian continental shelf and adjacent eastern Indian Ocean (22°S-34°S) during the late austral autumn. Larval fish assemblages, comprising >200 taxa from 114 neritic and oceanic teleost families, displayed significantly distinct latitudinal and cross-shelf variability, which was linked to meso-scale features of the Leeuwin Current, specifically anticyclonic eddies. Results of Lagrangian particle back-tracking showed good connection between the shelf and a developing eddy situated at 27°S; connectivity was highest in the 0-20 m depth stratum where >80% of the particles entering the eddy were derived from the shelf. This was supported by the high abundance (mean: 84 larvae m -2) of larval neritic taxa, especially small anchovy Engraulis australis larvae in the eddy. The lack of a significant difference in the size structure of these larvae between the shelf and eddy indicated continuous connection between these waters. In contrast, connectivity between the shelf and an older eddy further south was much lower (, This research was made possible with funding support from the Marine National Facility (MNF) for vessel time and the Commonwealth Scientific and Industrial Research Organization (CSIRO) Wealth from Oceans Flagship. D.H. was supported by a Murdoch University PhD scholarship and funding from the Western Australian Marine Science Institution (WAMSI). International travel for M.P.O. was funded by WAMSI and Murdoch University

An individual-based model, incorporating outputs of a data-assimilating hydrodynamic model, was developed to investigate the role of ocean circulation in the recruitment processes of western rock lobster ( Panulirus cygnus ) during its 9- to 11-month larval phase off the west coast of Australia. During austral summer, strong northward alongshore winds aid the offshore movement of early-stage model larvae from midshelf hatching sites into open ocean; during austral winter, eastward flows that feed the enhanced Leeuwin Current facilitate onshore movement of late-stage larvae towards nearshore habitats. Stokes drift induced by swells from the Southern Ocean is critical to retain larvae off the west coast. Diurnal migration and temperature-dependent growth are also important. Model larvae hatched in late spring – early summer grow faster because of longer exposure to warm summer temperature, which allows them to be transported towards the coast by the strong onshore flows in winter and reduces their natural mortality. Preliminary source–sink relationship indicates that the population was well mixed off the coast, with higher likelihood of settlement success from hatching sites in the north, mostly due to higher surface temperature. Weighted with the breeding stock distribution, the area between 27.5°S and 29.5°S, including the Abrolhos Islands, is the most important hatching area to the success of settlement.

A major observed and predicted impact of climate change on marine species is the poleward shift in their distributions and the resulting changes in community structure. Here, we used a Dynamic Bioclimate Envelope Model to project range shift of exploited marine fishes and invertebrates in Western Australia. We combined published data and expert knowledge to predict current species distributions for 30 tropical, sub-tropical and temperate species that occur along the coast of Western Australia. Using outputs from both a Regional Oceanographic Model and a Global Circulation Model, we simulated change in the distribution of each species. Our study shows that under the SRES (Special Report for Emission Scenarios) A1B scenario, the median rate of distribution shift is around 19 km decade–1 towards higher latitudes and 9 m deeper decade–1 by 2055 relative to 2005. As a result, species gains and losses are expected along the south coast and north coast of Western Australia, respectively. Also, the coast of Western Australia is expected to experience a ‘tropicalisation’ of the marine community in the future, with increasing dominance of warmer-water species. Such changes in species assemblages may have large ecological and socio-economic implications through shifts in fishing grounds and unexpected trophic effects.

Retention and dispersal of shelf waters under the influence of ocean boundary currents is crucial to recruitment processes of many coastal species. In this study, a Lagrangian particle tracking method based on an eddy-resolving, data-assimilating, hydrodynamic model is used to study spatial variations of local retention rates and alongshore dispersal of surface waters on the continental shelf off the west coast of Australia. The circulation on the shelf off the west coast of Australia is dominated by the southward-flowing eastern boundary current, the Leeuwin Current, which is interrupted by episodic wind-driven, northward, inshore surface transport during the austral summer, and by mesoscale eddy formations during the austral winter. Low-retention shelf regions tend to experience high alongshore currents, owing to the near-shore influence of the Leeuwin Current, protruding coastal geography, or formation of mesoscale eddies, whereas high-retention regions are sheltered from the direct influence of the Leeuwin Current by coastal geographic features. Alongshore dispersal also exhibits spatial as well as seasonal heterogeneity, with predominantly southward dispersal during the austral winter, and more symmetrical dispersal during the austral summer. Shelf retention and seasonal dispersal are linked with recruitment processes of invertebrate and fish species off the west coast of Australia.