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Warming seas, marine heatwaves, and habitat degradation are increasingly widespread phenomena affecting marine biodiversity, yet our understanding of their broader impacts is largely derived from collective insights from independent localized studies. Insufficient systematic broadscale monitoring limits our understanding of the true extent of these impacts and our capacity to track these at scales relevant to national policies and international agreements. Using an extensive time series of co-located reef fish community structure and habitat data spanning 12 years and the entire Australian continent, we found that reef fish community responses to changing temperatures and habitats are dynamic and widespread but regionally patchy. Shifts in composition and abundance of the fish community often occurred within 2 years of environmental or habitat change, although the relative importance of these two mechanisms of climate impact tended to differ between tropical and temperate zones. The clearest of these changes on temperate and subtropical reefs were temperature related, with responses measured by the reef fish thermal index indicating reshuffling according to the thermal affinities of species present. On low latitude coral reefs, the community generalization index indicated shifting dominance of habitat generalist fishes through time, concurrent with changing coral cover. Our results emphasize the importance of maintaining local ecological detail when scaling up datasets to inform national policies and global biodiversity targets. Scaled-up ecological monitoring is needed to discriminate among increasingly diverse drivers of large-scale biodiversity change and better connect presently disjointed systems of biodiversity observation, indicator research, and governance.

In recent decades, the transplantation of corals has been a primary focus of restoration strategies in areas where coral populations have declined [...]

Rock pool fish assemblages can be highly diverse, though are poorly studied in many locations. Where rock pool fishes have been studied, sampling has often been undertaken using destructive techniques, causing fish mortality and damage to pool ecosystems. There is, therefore, a need for greater understanding of non-destructive methods for evaluating rock pool fish assemblages. To improve knowledge in this area, we tested three non-destructive techniques: mini baited remote underwater videos (mini-BRUVs) which utilised a stationary video camera to record fish, visual censuses (VCs) where a roving observer recorded fish using a slate and observer operated videos (OOVs) where fish were recorded by an observer using a video camera. These methods were tested for their effectiveness in assessing fish assemblages, using data from rock pools on Lord Howe Island (LHI), in New South Wales (NSW), Australia. VCs and OOVs required significantly less total survey time than mini-BRUVs, whereas mini-BRUVs provided advantages in the detection of fishes in small pools (

Biodiversity surveys of marine species are largely conducted during the day, and often over relatively short timeframes, due to practical, operational, and budgetary constraints. As a consequence, surveys can underestimate biodiversity for some groups, such as heterobranch (formerly opisthobranch) molluscs, where abundances vary seasonally by orders of magnitude and different species are active at different times of the day. Here, we quantitatively assess day/night (diel) and seasonal variation in heterobranch sea slug assemblages using monthly, diel scuba surveys for 13 months at three sites in Port Stephens, New South Wales (NSW). All heterobranch sea slugs encountered in 50 × 5-m belt transects were recorded using identical survey methods both during the day and at night. Significant differences were detected between day and night assemblages, with species richness and abundance being consistently higher at night. Significant cyclical patterns were also detected in sea slug assemblages over the duration of the study, for both day and night assemblages, with species assemblages changing throughout the study period. The results demonstrate that marine diversity studies conducted only during the day, and those which do not account for all seasons, are likely to underestimate diversity and abundance of molluscs, particularly heterobranch sea slugs. It is, therefore, important that studies which aim to provide a comprehensive catalogue of molluscan biodiversity include not only day-time surveys, but also those conducted at night. They should also include temporal replication in order to capture ephemeral species.

Reef Life Survey (RLS) provides a new model for ecological monitoring through training experienced recreational divers in underwater visual census methods to the level of skilled scientists. Detail produced is similar to that of programs with professional scientific teams, at low cost to allow global coverage. RLS differs from most other citizen science initiatives in its emphasis on rigorous training and data quality rather than open participation, selectively involving the most skilled and committed members. Volunteers participate primarily because they appreciate the close relationship with scientists, other divers, and managers, and see their efforts directly contributing to improved environmental outcomes. RLS works closely with Australian management agencies, scheduling annual events at core monitoring sites associated with 10 inshore marine protected areas Australia-wide. Surveys of 12 offshore Australian Marine Parks (AMPs) are realized through 2-4 week voyages in a sailing catamaran crewed by volunteers. Across the AMP network, RLS surveys have quantified densities of fishes, mobile invertebrates, macroalgae and corals at 350 shallow coral reef sites (180 sites surveyed on two or more occasions), providing an understanding of (i) population changes amongst threatened species including sea snakes, (ii) responses of fish and invertebrate populations following fisheries closures, (iii) ecosystem-wide impacts of marine heat-waves, and (iv) the extent that AMPs spanning the network comprehensively encompass national coral reef biodiversity. This scientist/volunteer/manager collaboration could be greatly expanded globally (presently 3537 sites in 53 countries).

The distribution of heterobranch sea slugs is generally poorly documented at a regional scale. Thus, it is currently difficult to quantify biodiversity, identify endemic and invasive species, and track range shifts at scales relevant to conservation management. For Lord Howe Island, which lies ~600 km east of the New South Wales (NSW) mid-north coast, data from a range of taxa indicate high biodiversity and endemism, but this has not been examined for heterobranch sea slugs. To address this deficit, we collated occurrence data on sea slugs from both private and public sources, including museum records, scientific literature, field guides and citizen science activities. A total of 186 nominal (formally described) species in 82 genera and 31 families were identified from intertidal and subtidal habitats. Of these, two species are endemic to Lord Howe Island, two have not been recorded elsewhere in Australia, and 28 have not been recorded on the mainland coast of NSW. These results support studies of other taxa suggesting that the relative isolation of the island has facilitated the development of diverse and unique assemblages. However, this isolation is moderated by larval transport from surrounding regions, resulting in considerable overlap of the species pool with the mainland coast of NSW and tropical areas to the north.

Port Stephens, on the central New South Wales coast, provides ideal oceanographic and benthic conditions for the settlement and growth of larvae of tropical species delivered from the north by the East Australian Current. The popularity of the bay for recreational and scientific diving has facilitated extensive documentation of the biota over several decades, confirming its high biodiversity. Of the 313 species of heterobranch sea slugs recorded from Port Stephens to date, 30 are not known to occur further south. Our observations increase the number of taxa with a southern distribution limit at Port Stephens by 12 species and add to a growing list of marine taxa that are progressively extending their southern range, potentially as a result of climate change.