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An accurate representation of physical and biological processes is crucial to resolve larval dispersal pathways and characterize connectivity of coral reef ecosystems. We investigate how hydrodynamic forcings drive larval retention rates during the bi‐annual mass coral spawning of the coral genus Acropora within a coral reef atoll (Mermaid Reef), located off northwestern Australia. By analyzing hydrodynamic conditions during 41 yr of historical spring and autumn coral spawning events, we identify typical and extreme hydrodynamic forcing conditions. Particle tracking using the output from a fine‐scale coupled wave‐flow hydrodynamic model forced with typical hydrodynamic conditions during coral spawning, revealed a mean transport of larvae eastward across the atoll. Transport was mainly driven by a combination of wave and tidal currents, where the residual tidal flow and unidirectional wave flow increased the net export of particles, and the oscillatory tidal (non‐residual) flow reduced the net export of particles from the reef. Importantly, however, numerical simulations forced with extreme hydrodynamic conditions generated by episodic tropical cyclones (11 out of 41 yr) showed large deviations from the typical eastward flow during autumn spawning, generating different connectivity pathways within the reef. Considering the substantial time larvae can be retained within reef systems, overlooking fine‐scale hydrodynamic processes may greatly overestimate larval transport distances between adjacent coral reef atolls. As a result, we emphasize the need to consider fine‐scale hydrodynamic processes within regional connectivity predictions, which is generally not considered yet critical to understand the capacity of reefs to recover following disturbances. [ABSTRACT FROM AUTHOR]

Aim: Genetic connectivity is a key component of species resilience to climate change in terms of recovery capacity following disturbance and capacity to disperse to novel locations as the climate warms and isotherms shift poleward. We aimed to strengthen our understanding of resilience in this context by characterizing patterns of connectivity and genetic diversity in a broadcast spawning coral across a tropical-- temperate transition zone. We hypothesize genetic differentiation between tropical and temperate populations and decreasing genetic diversity with higher latitudes. Location: Western Australia (WA). Taxon: Turbinaria species complex. Turbinaria reniformis' Oken, 1815 (Scleractinia: Dendrophylliidae). Methods: A total of 930 target corals were sampled from 10 locations between 13 and 32° latitude spanning a 9°C mean temperature range. In situ species identification of T. reniformis is hindered by morphological plasticity and homoplasy with sister species. We combined Sanger sequencing of two mitochondrial DNA markers and high-throughput genotyping by sequencing (GBS) to isolate a single genetic Turbinaria lineage from our dataset through which patterns of genetic flow and diversity along the WA coastline could be explored using population- and individual-based clustering analyses. Results: Mitochondrial DNA sequence variation was low among Turbinaria samples and could not resolve individual species. Using GBS, we identified three genetically distinct lineages. Subsequent analyses within one of these lineages revealed strong spatial subdivision with 2-3 genetic clusters. While temperate populations were genetically diverged from more tropical sites, we did not observe declines in genetic diversity with latitude. Main conclusions: Tropical populations of T. 'reniformis' in Western Australia exhibit strong genetic connectivity, which extends to a southern limit at sub-tropical Shark Bay. Temperate populations are genetically isolated from their tropical counterparts but have relatively high genetic diversity. While the maintenance of genetic variation in temperate populations may provide some resilience to future climate scenarios, their isolation may increase their vulnerability. [ABSTRACT FROM AUTHOR]

The worlds' coral reefs are declining due to the combined effects of natural disturbances and anthropogenic pressures including thermal coral bleaching associated with global climate change. Nearshore corals are receiving increased anthropogenic stress from coastal development and nutrient run-off. Considering forecast increases in global temperatures, greater understanding of drivers of recovery on nearshore coral reefs following widespread bleaching events is required to inform management of local stressors. The west Pilbara coral reefs, with cross-shelf turbidity gradients coupled with a large nearby dredging program and recent history of repeated coral bleaching due to heat stress, represent an opportune location to study recovery from multiple disturbances. Mean coral cover at west Pilbara reefs was monitored from 2009 to 2018 and declined from 45% in 2009 to 5% in 2014 following three heat waves. Recruitment and juvenile abundance of corals were monitored from 2014 to 2018 and were combined with biological and physical data to identify which variables enhanced or hindered early-stage coral recovery of all hard corals and separately for the acroporids, the genera principally responsible for recovery in the short-term (<7 years). From 2014 to 2018, coral cover increased from 5 to 10% but recovery varied widely among sites (0–13%). Hard coral cover typically recovered most at shallower sites that had higher abundance of herbivorous fish, less macroalgae, and lower turbidity. Similarly, acroporid corals recovered most at sites with lower turbidity and macroalgal cover. Juvenile acroporid densities were a good indicator of recovery at least two years after they were recorded. However, recruitment to settlement tiles was not a good predictor of total coral or acroporid recovery. This study shows that coral recovery can be slower in areas of high turbidity and the rate may be reduced by local pressures, such as dredging. Management should focus on improving or maintaining local water quality to increase the likelihood of coral recovery under climate stress. Further, in turbid environments, juvenile coral density predicts early coral recovery better than recruits on tiles and may be a more cost-effective technique for monitoring recovery potential. • Three thermal anomalies over four years bleached corals and reduced cover by ~90%. • Coral recovery varied spatially, limited driven mostly by turbidity. • Better water quality increases the likelihood of coral recovery under climate stress. • Juvenile coral density predicted early coral recovery better than recruits on tiles. [ABSTRACT FROM AUTHOR]