Kelps are in global decline due to climate change, including ocean warming. To identify vulnerable species, we need to identify their tolerances to increasing temperatures and whether tolerances are altered by co-occurring drivers such as inorganic nutrient levels. This is particularly important for those with restricted distributions, which may already be experiencing thermal stress. To identify thermal tolerance of the range restricted kelp Lessonia corrugata, we conducted a laboratory experiment on juvenile sporophytes to measure performance (growth, photosynthesis) across its thermal range (4 – 22 °C). We found the upper thermal limit for growth and photosynthesis to be ~ 22 – 23 °C, with an optimum of ~ 16 °C. To determine if elevated inorganic nitrogen availability could enhance thermal tolerance, we compared performance of juveniles under low (4.5 µmol/day) and high (90 µmol/day) nitrate conditions at and above the thermal optimum (16 – 23.5 °C). Nitrate enrichment did not enhance thermal performance at temperatures above the optimum but did lead to elevated growth rates at the thermal optimum 16 °C. Our findings indicate L. corrugata is likely to be extremely susceptible to moderate ocean warming and marine heatwaves. Peak sea surface temperatures during summer in eastern and northeastern Tasmania can reach up to 20 – 21 °C and climate projections suggest that L. corrugata’s thermal limit will be regularly exceeded by 2050 as south-eastern Australia is a global ocean-warming hotspot. By identifying the upper thermal limit of L. corrugata we have taken a critical step in predicting the future of the species in a warming climate.

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 principle aim of this project was to map the fine-scale spatial distribution of key abalone habitat impacted by urchins in < 25 m water depth using multibeam acoustic imagery. Detailed substrate type (Pavement Reef, Megaclast Reef, Mixed Consolidated Sediment/Reef and Sand), and kelp coverage maps have been produced for the east coast of Tasmania. Large urchin barrens have been predicted and the minimum quantifiable unit of which small incipient barrens can be detected has been identified using this acoustic water column technique. This data provides a snapshot of the 2021 distribution of seafloor habitats and associated vegetation distribution, and will assist in the facilitation of strategic decision making for urchin control and abalone management. Data for download has been split by fishing block (22-24, 27-30). This record describes *FISHING BLOCK 28*. The following data products are available for download, for each fishing block: • 50cm resolution bathymetry • 50cm resolution substrate type (Seamap Australia classification) • bathymetry derivatives (seabed slope, curvature, rugosity, 1 and 2m contours) • water column data - 1m mean signal • water column data - 9m2 raw block statistic • water column data - vegetation likelihood classification See associated records for access to data from other fishing blocks (22, 23, 24, 27, 29, 30).

This dataset relates to statistical models of killer whale (Orcinus orca) occurrence in the Bremer Sub-Basin developed from vessel-based and aerial survey data collected between 2015 and 2017. Further information can be found in: Salgado-Kent C, Parnum I, Wellard R, Erbe C, Fouda L. 2017. Habitat preferences and distribution of killer whales (Orcinus orca) in the Bremer Sub-Basin, Australia. Report to the National Environmental Science Programme Marine Biodiversity Hub (CMST 2017-15), 37 p.

Collected benthic community structure (species and abundance) and physical/chemical attributes (including sediment grain size, redox, sulphide and depth) for a large number of locations in the Huon and Derwent estuaries of south east Tasmania. Data was collected using van veen grab, divers where necessary or core samples. All locations include heavy metal data and site information. Most data was collected with spatial references (GPS).

The Aqua and Orbview satellites carry a MODIS and SeaWIFS sensors (respectively) that observes sunlight reflected from within the ocean surface layer at multiple wavelengths. These multi-spectral measurements are used to infer the concentration of chlorophyll-a (Chl-a), most typically due to phytoplankton, present in the water. There are multiple retrieval algorithms for estimating Chl-a and aggregating the data over time. This data set is a reprocessed copy of 9km monthly and 8-day versions produced globally by NASA, adjusted for the Southern Ocean south of latitude 30S. The full methodology is described in Johnson, R., Strutton, P.G., Wright, S.W., McMinn, A., Meiners, K.M., 2013. Three improved satellite chlorophyll algorithms for the Southern Ocean. Journal of Geophysical Research: Oceans. doi: 10.1002/jgrc.20270. It is expected that the data set will be periodically updated with contemporary data as it becomes available. There are four sub-streams within this data set. A monthly and an 8-day series for MODIS/Aqua and similarly for SeaWIFS. Note that SeaWIFS ceased operation in late 2010 so there will be no further SeaWIFS data. The data represented by this record is weekly data for MODIS/Aqua.