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Context. Longspined sea urchins (Centrostephanus rodgersii) form extensive urchin barrens in south-eastern Australia, threatening biodiversity and lucrative fishery stocks. Although large urchins are readily visible on reefs, small or 'undersized' urchins have often been considered non-emergent, cryptic, and largely inaccessible to predators, meaning smaller predators are considered not to contribute to top-down urchin control. Aims. Here,we aimto investigate variation in nocturnalmovement across urchin size classes and discuss the associated ecological implications. Methods. Using timelapse footage we measured timing of movement, distance covered, and displacement of different sized sea urchins in various habitats. Key results. Small urchins emerge from cryptic habitats and are active overnight on open reef areas. At dusk, smaller urchins emerge later than larger urchins, whereas at dawn, movement of all size classes of urchins decline at a similar rate. Conclusions. The nocturnal emergence and movement of small urchins on open reef spaces makes them accessible to nocturnal predators, such as the southern rock lobster (Jasus edwardsii). Implications. This time- space overlap of predator and prey implies that rock lobsters (including small lobsters) may be inflicting higher predatory pressure than previously considered on undersized sea urchins. [ABSTRACT FROM AUTHOR]

The loss of marine biodiversity is a major global issue that needs to be prioritised. In Australia, a considerable proportion (48%) of its Exclusive Economic Zone is dedicated to marine protected areas. To effectively manage this network of marine protected areas Australia has recently introduced a Management Effectiveness system. This system is designed to identify, monitor, and manage natural values and the various activities and pressures affecting the Australian Marine Parks (AMPs). Key to this approach is the identification and accurate mapping of the location of these values and pressures acting on the seabed. The AusSeabed program is a national initiative in Australia aimed at improving access to bathymetric data and coordinating efforts to collect such data in Australian waters. This manuscript proposes a novel systematic processing method to create detailed and scalable geomorphometric maps from AusSeabed's bathymetric data holdings, intended as a standard operating procedure for initial bathymetric data interpretation in the AMPs. Utilising this workflow, we produce seafloor geomorphometry maps across 37 AMPs within which sufficient bathymetric data has been collected. These maps can be used 1) for predictive mapping of biological assemblages; 2) in field sampling design for the collection of 'ground truthing' data (e.g. underwater imagery and sediment samples) to validate habitat maps from bathymetric datasets; and 3) as input datasets for subsequent geomorphological mapping with a deeper understanding of seafloor processes. This research highlights the importance of robust geomorphometry classification standards to ensure consistency in mapping Australia's marine estate in preparation for the Decade of Oceans plans. The Seamap Australia program provides a stepwise approach to advancing Australia's national collection of bathymetric data into derived products that can enable habitat mapping of Australian waters, providing a foundational tool for the adaptive management of AMPs. [ABSTRACT FROM AUTHOR]