Sea urchins have the capacity to destructively overgraze kelp beds and cause a wholesale shift to an alternative and stable ‘urchin barren’ state. However, their destructive grazing behaviour can be highly labile and contingent on behavioural shifts at the individual and local population level. Changes in supply of allochthonous food sources, i.e. availability of drift-kelp, is often suggested as a proximate trigger of change in sea urchin grazing behaviour, yet field tests of this hypothesis are rare. Here we conduct a suite of in situ behavioural surveys and manipulative experiments within kelp beds and on urchin barrens to examine foraging movements and evidence for a behavioural switch to an overgrazing mode by the Australian sea urchin Heliocidaris erythrogramma (Echinometridae). Tracking of urchins using time-lapse photography revealed urchin foraging to broadly conform to a random-walk-model within both kelp beds and on barren grounds, while at the individual level there was a tendency towards local ‘homing’ to proximate crevices. However, consistent with locally observed ‘mobile feeding fronts’ that can develop at the barrens-kelp interface, urchins were experimentally inducible to show directional movement toward newly available kelp. Furthermore, field assays revealed urchin grazing rates to be high on both simulated drift-kelp and attached kelp thalli on barren grounds, however drift-kelp but not attached kelp was consumed at high rates within kelp beds. Time-lapse tracking of urchin foraging before/ after the controlled addition of drift-kelp on barrens revealed a reduction in foraging movement across the reef surface when drift-kelp was captured. Collectively results indicate that the availability of drift-kelp is a pivotal trigger in determining urchin feeding modes, which is demonstrably passive and cryptic in the presence of a ready supply of drift-kelp. Recovery of kelp beds therefore appears possible if a sustained influx of drift-kelp was to inundate urchin barrens, particularly on reefs where local urchin densities and where grazing pressure is close to the threshold enabling kelp bed recovery.

The data is the quantitative abundance of fish derived from underwater visual census methods involving transect counts at rocky reef sites around Tasmania. This data forms part of a larger dataset that also surveyed megafaunal invertebrate abundance and algal cover for the area. The aggregated dataset allows examination of changes in Tasmanian shallow reef floral and faunal communities over a decadal scale - initial surveys were conducted in 1992-1995, and again at the same sites in 2006-2007. There are plans for ongoing surveys. An additional component was added in the latter study - a boat ramp study looking at the proximity of boat ramps and their effects of fishing. We analysed underwater visual census data on fishes and macroinvertebrates (abalone and rock lobsters) at 133 shallow rocky reef sites around Tasmania that ranged from 0.6 - 131 km from the nearest boat ramp. These sites were not all the same as those used for the comparison of 1994 and 2006 reef communities. The subset of 133 sites examined in this component consisted of only those sites that were characterized by the two major algal (kelp) types (laminarian or fucoid dominated). Sites with atypical algal assemblages were omitted from the 196 sites surveyed in 2006. This study aimed to examine reef community data for changes at the community level, changes in species richness and introduced species populations, and changes that may have resulted from ocean warming and fishing. The methods are described in detail in Edgar and Barrett (1997). Primarily the data are derived from transects at 5 m depth and/or 10 m depth at each site surveyed. The underwater visual census (UVC) methodology used to survey rocky reef communities was designed to maximise detection of (i) changes in population numbers and size-structure (ii) cascading ecosystem effects associated with disturbances such as fishing, (iii) long term change and variability in reef assemblages.

This data set consists of a scored time-series of Autonomous Underwater Vehicle (AUV) images from the Bicheno region on the east coast of Tasmania. Surveys were conducted between 2011 and 2016 within the Governor Island Marine Reserve and nearby sites outside the reserve. Governor Island was surveyed in 2011, 2013, 2014 and 2016. The outside sites of Trap Reef, Cape Lodi and Butlers Point were surveyed in 2011, 2013 and 2016. Imagery across all surveys was scored for the presence of Centrostephanus rodgersii urchin barrens across rocky reef at each site. Prior to analysis the data was subsetted to every fifth image to avoid overlapping images. The data set also contains depth information for each image and a measure of rugosity (Vector Rugosity Measure) computed in ArcGIS software from a one metre resolution bathymetric map covering the survey sites. Analysis was conducted to examine the trend in the presence of barrens through time and to compare the occurrence of barrens inside the Governor Island Marine Reserve with sites outside the reserve. A spatio-temporal model incorporating both spatial and temporal correlation in the time-series of data was used. This data set contains the scored data used in the analysis. Further details of the methods used and results are contained in the following article. Please cite any use of the data or code by citing this article: Perkins NR, Hosack GR, Foster SD, Monk J, Barrett NS (2020) Monitoring the resilience of a no-take marine reserve to a range extending species using benthic imagery. PLOS ONE 15(8): e0237257. https://doi.org/10.1371/journal.pone.0237257

The phenotypic plasticity of habitat-forming seaweeds was investigated with a transplant experiment in which juvenile Ecklonia radiata and Phyllospora comosa were transplanted from NSW (warm conditions) to Tasmania (cool conditions) and monitored for four months. We used multiple performance indicators (growth, photosynthetic characteristics, pigment content, chemical composition, stable isotopes, nucleic acids) to assess the ecophysiology of seaweeds before and following transplantation between February 2012 and June 2012.

Seasonal patterns in the in situ ecophysiology of the common habitat-forming seaweeds Ecklonia radiata, Phyllospora comosa, and Macrocystis pyrifera were investigated at different latitudes and depths in southeastern Australia. We used multiple performance indicators (photosynthetic characteristics, pigment content, chemical composition, stable isotopes, nucleic acids) to assess the ecophysiology of seaweeds near the northern and southern margins of their range, along a depth gradient (E. radiata only), over a two year period (September 2010 – August 2012).