Data on captive feeding trials for prey preference in southern rock lobsters on longspined sea urchins, black lipped abalone, shortspined sea urchins and periwinkle.

This dataset has been superseded by https://metadata.imas.utas.edu.au/geonetwork/srv/eng/catalog.search#/metadata/0145df96-3847-474b-8b63-a66f0e03ff54 (Victorian Statewide Marine Habitat Map 2023). The Victorian seabed habitat map documents the distribution of broad benthic habitat types in Victorian Coastal Waters to the State’s 3 nautical mile jurisdictional limit. The map was created using a top-down modelling process whereby habitat descriptors were assigned using seafloor structure and biological information derived from multibeam sonar (Victorian Marine Habitat Mapping Project), bathymetric LiDAR (Future Coasts program) and observations from underwater video. Identification of benthic biota, to the lowest discernible taxonomic level, and substrate characteristics were recorded according to the Victorian Towed Video Classification scheme (Ierodiaconou et al. 2007).

Shifts from productive kelp beds to impoverished sea urchin barrens occur globally and represent a wholesale change to the ecology of sub-tidal temperate reefs. Although the theory of shifts between alternative stable states is well advanced, there are few field studies detailing the dynamics of these kinds of transitions. In this study, sea urchin herbivory (a ‘top-down’ driver of ecosystems) was manipulated over 12 months to estimate (1) the sea urchin density at which kelp beds collapse to sea urchin barrens, and (2) the minimum sea urchin density required to maintain urchin barrens on experimental reefs in the urbanised Port Phillip Bay, Australia. In parallel, the role of one of the ‘bottom-up’ drivers of ecosystem structure was examined by (3) manipulating local nutrient levels and thus attempting to alter primary production on the experimental reefs. It was found that densities of 8 or more urchins m-2 (≥ 427 g m-2 biomass) lead to complete overgrazing of kelp beds while kelp bed recovery occurred when densities were reduced to ≤ 4 urchins m-2 (≤ 213 g m-2 biomass). This experiment provided further insight into the dynamics of transition between urchin barrens and kelp beds by exploring possible tipping-points which in this system can be found between 4 and 8 urchins m-2 (213 and 427 g m-2 respectively). Local enhancement of nutrient loading did not change the urchin density required for overgrazing or kelp bed recovery, as algal growth was not affected by nutrient enhancement.