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FOUR-and-a-half thousand metres beneath the waves, trapped in deep-sea volcanoes and submarine canyons, the history of WA's coastline is written into the rocks.

FOUR-and-a-half thousand metres beneath the waves, trapped in deep-sea volcanoes and submarine canyons, the history of WA's coastline is written into the rocks.

The extreme Western Australia 2011 marine heatwave had a lasting effect on the marine ecosystem and after 7 years, only parts of the ecosystem have showed good signs of recovery. After the heatwave, scallop fisheries in the Abrolhos Is. and Shark Bay were closed for 3-5 years, while the Shark Bay crab fishery was closed for 18 months; these fisheries at the center of the heatwave have shown some improvement due to better protection of spawning stock and improved environmental conditions. Also at the center of the heatwave, Roe's abalone suffered a catastrophic mortality and has not recovered as spawning stock remains very low. The Perth abalone stock which was outside the peak heatwave area had a major stock reduction but remained opened with reduced catches. The heatwave had a marked indirect effect on brown tiger prawns in Exmouth Gulf due to loss of seagrass habitat. The heatwave also resulted in a decline in western king prawn recruitment in Exmouth Gulf, to the north of heatwave center, but an improved recruitment in the cooler waters of Shark Bay. Western rock lobsters near the heatwave peak also appear to have been indirectly affected and have not recovered. Factors influencing the recovery rate from the heatwave appeared to be: species near their upper temperature range and/or sensitive to warming temperatures; spatial overlap between the warming event and species distribution; whether spawning stock was affected to the point of recruitment impairment; life-cycle duration of invertebrate (or habitat) species affected; and management intervention. This study provides a framework for managing the consequences of heatwaves on fisheries by highlighting the value of early identification of the event and its effect on fisheries and having flexible harvest strategies for early management intervention. This is particularly important as long-term increases in water temperatures will increase the frequency of marine heatwave events and the fisheries stocks would hav

The pelagic development stages of many marine invertebrate species dictates their spatial and temporal distribution once reaching their benthic second phase of life. This life cycle is associated with the Western Rock Lobster (Panulirus cygnus) along the coast of Western Australia. Over the past 50 years, the number of puerulus reaching the nearshore reefs after their first 9 to 11 months of pelagic life in Western Australia has been monitored. These numbers, collected now at eight sites over the latitudes of the fishery, are indicative of the catchable stock 3-4 years into the future. In 2008, the fishery experienced a recruitment failure which lasted for several years before recovering to mean numbers pre-2008. This was associated with spatial and temporal shifts in the patterns of puerulus settlement. Previous research has hypothesized that physical and biological conditions in the south-east Indian Ocean no longer favored their survival. However, this decline has not been attributed to a single process. As the recovery is ongoing, contrasts in the settlement data before and after the decline are not completed. Here we characterize the data using ANOVA and pairwise comparisons to gain a better understanding of the typical patterns after the decline. Our results demonstrate that there has been a significant reduction in puerulus numbers over the first half of the season at all sites post decline. For the sites south of Lancelin there has been a significant reduction in puerulus numbers over the whole season. In addition, sites that show signs of recovery indicate that the majority of settlement occurred in the second half of the season. We anticipate these results to be the starting point for focused research into the environmental changes which may have occurred to generate these shifts in settlement numbers both from a timing and spatial perspective.

Drops locked inside rock offer clues to modeling Earth's climate and ocean circulation.

The recently discovered Onnuri hydrothermal vent field (OVF) is a typical off-axis ultramafic-hosted vent system, located on the summit of the dome-like ocean core complex (OCC) at a distance of ∼12 km from the ridge axis along the middle region of the Central Indian Ridge (CIR). The plume chemistry with high methane anomaly was consistent with the precursor of hydrothermal activity; however, the fundamental characteristic of the OVF system, such as the hydrothermal circulation process and source of heat, remains poorly understood. Here, we focus on the geochemical features of surface sediments and minerals collected at and around the OVF region in order to better understand this venting system. The results reveal that the OVF sediments are typified by remarkably high concentrations of Fe, Si, Ba, Cu, and Zn, derived from hydrothermal fluid and S and Mg from seawater; depleted C-S isotope compositions; and abundant hydrothermally precipitated minerals (i.e., Fe-Mn hydroxides, sulfide and sulfate minerals, and opal silica). Notably, the occurrence of pure talc and barite bears witness to strong hydrothermal activity in the OVF, and their sulfur and strontium isotope geochemistry agree with extensive mixing of the unmodified seawater with high-temperature fluid derived from the gabbroic rock within the ultramafic-dominated ridge segment. The findings reveal that the OVF is a representative example of an off-axis, high-temperature hydrothermal circulation system, possibly driven by the exothermic serpentinization of exposed peridotites. Given the widespread distribution of OCC with detachment faults, furthermore, the OVF may be the most common type of hydrothermal activity in the CIR, although the paucity of data precludes generalizing this result. This study provides important information contributing to our understanding of the ultramafic-hosted hydrothermal vent system with a non-magmatic heat source along mid-ocean ridges.

Repeat multibeam mapping of two slope-confined canyons on the northwest Australian margin provides new understanding of the processes that are active in shaping these environments. The Cape Range and Cloates canyons initiate on the mid to lower continental slope but are now known to be connected to the shelf via small channels and gullies. Both canyons have areas of steep walls, with evidence of slides, and large depressions on the canyon floors. These canyons were first mapped systematically with multibeam sonar in 2008 and were remapped in 2020 during a biodiversity survey that also collected high-resolution imagery and biological samples. Comparison of seabed features between these two time periods indicates active sliding, minor headwall retreat and continued excavation of deep depressions on the canyon floor. Significantly, intact blades of displaced seagrass imaged at various depths up to 4200 m throughout both canyons indicates that material sourced from the adjacent continental shelf is being transported through these canyon systems. Turbidity currents are actively modifying canyon walls and floor depressions, while also providing a sediment source that has resulted in minor accretion on the canyon floor. Sedimentation likely regulates benthic communities in these canyons, with imagery showing highest densities of sessile invertebrates in habitats protected from sedimentation (e.g. rock overhangs, cliff edges). Since steep canyon habitats are rare within these canyons, and support high benthic abundance, they likely represent biologically significant areas of the Gascoyne Marine Park. Repeat mapping provides an understanding of the dynamics of these canyons and a context for assessing and monitoring the stability of the seabed habitats within this marine reserve.

The Java Trench is the only subduction trench in the Indian Ocean that extends to the hadal zone (> 6,000 m water depth), and except for sevenbenthic trawls acquired around the 1950s, there has been little to no sampling at hadal depths undertaken since. In 2019, we undertook a 5-day expedition comprising a scientific dive using a full ocean depth-rated submersible, the DSV Limiting Factor, seven hadal-lander deployments, and high-resolution bathymetric survey. The submersible performed a video transect from the deepest point of the trench, up a 150 m high near-vertical escarpment located on the forearc, and then across a plateau at a depth of ∼7,050 m to make in situ observations of the habitat heterogeneity and biodiversity inhabiting these hadal depths. We found the Java Trench hadal community to be diverse and represented by 10 phyla, 21 classes, 34 orders and 55 families, with many new records and extensions in either depth or geographic range, including a rare encounter of a hadal ascidian. The submersible transect revealed six habitats spanning the terrain. The deepest trench axis comprised fine-grained sediments dominated by holothurians, whereas evidence of active rock slope failure and associated talus deposits were prevalent in near-vertical and vertical sections of the escarpment. Sediment pockets and sediment pouring down the steep wall in "chutes" were commonly observed. The slope terrain was dominated by two species in the order Actiniaria and an asteroid, as well as 36 instances of orange, yellow, and white bacterial mats, likely exploiting discontinuities in the exposed bedrock, that may indicate a prevalence of chemosynthetic input into this hadal ecosystem. Near the top of the escarpment was an overhang populated by > 100 hexactinellid (glass) sponges. The substrate of the plateau returned to fine-grained sediment, but with a decreased density and diversity of epifauna relative to the trench floor. By providing the first visual insights of the h

Two men survive reported shark attack on their boat off Western Australia.

Australia's ancient language shaped by sharks.

Great White Sharks in Australia Get a Concert from KISS. But Will the Sharks Care?

Having struck something in the water last night Sam DAVIES this morning is heading out of the worst of the weather and the sea state to further assess the damage to Initiatives Coeur. She spoke to Vendee Globe HQ this morning.