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.

This database contains sampling effort, catch records, biological data, and water quality data for sampling and catches of elasmobranchs in northern Australian rivers, estuaries and coasts undertaken under the National Environmental Research Program (NERP) Marine Biodiversity Hub Project 2.4 'Supporting Management of Listed and Rare Species'. and the National Environmental Science Program (NESP) Marine Biodiversity Hub Project A1 'Northern Australian Hotspots for the Recovery of Threatened Euryhaline Elasmobranchs'. Surveys using gillnets and rod-and-line were undertaken in the Top End region of the Northern Territory and the Kimberley region of Western Australia. Selected animals were tagged for movement ecology, habitat use and mortality estimates (acoustic telemetry), and tissue samples were collected from all fish for molecular analyses (population genetics and close-kin mark-recapture).

Bathymetry and Side Scan Sonar transects taken in various project locations within South Australian state waters. For analysis of seabed topography and interpretation of benthic substrate and flora.

These contours are derived from the Australian Bathymetry and Topography Grid, June 2009 (Geoscience Australia).

This record provides an overview of the scope and research output of NESP Marine Biodiversity Hub Project A9 - "Grey Nurse Shark CK-MR Population Estimate – East Coast". For specific data outputs from this project, please see child records associated with this metadata. -------------------- A review of the 2002 National Recovery Plan for Grey Nurse Shark (DEWHA 2009) concluded it was not possible to determine if the east coast population had shown any signs of recovery (DoE 2014); recommending a new recovery plan be developed for this species. A primary objective of the new recovery plan (DoE 2014) is to improve knowledge of GNS population status. This will require a robust estimate of population size and trend – something that has not been provided to date. This project will use genetic SNP data to inform close kin-mark recapture analysis to estimate population size and trend, and provide guidance on future monitoring strategies for the east coast population of grey nurse shark. Planned Outputs • Tools to refine and integrate CK-MR and species demographic data for population assessments of a key threatened species at a national scale (combining knowledge developed under this project combined with similar techniques being applied under NESP to euryhaline sharks and white sharks). • A national estimate of (census) population size and trend for the eastern Australian population of grey nurse shark will be developed to fulfil the highest priority actions of the National Recovery Plan. • Identify national strategies to guide future monitoring of grey nurse shark populations. • The project will provide peer-reviewed additions to the scientific literature that will add to the science-support for the development and implementation of policies to support the ecologically sustainable management of Australia’s marine environment.

Six dredges were undertaken from the RV Investigator during voyage IN2016_E01 to obtain rock and sediment samples to constrain the crustal nature, age of formation and paleo-environment through time of the Cascade Seamount, located offshore Eastern Tasmania, Australia. This record lists the sample number, weights and rock types recovered. In total we collected 713 kg of rock samples, including basalts, conglomerates, sandstones, limestones and tuffs.

We evaluate the status of shellfish reef ecosystems in Australia including their historical distribution and loss, regulation and management and identify current research priorities, policies and conservation mechanisms that can enable their future protection and repair. Eight species of shellfish were identified as developing complex, three-dimensional reef systems over large scales in intertidal and subtidal areas across tropical, subtropical and temperate Australia. A dramatic decline in the extent and condition of Australia’s shellfish reef ecosystems occurred during the mid-1800s to early 1900s in concurrence with extensive harvesting for food and lime production, habitat modification, disease outbreaks and a decline in water quality. Despite early attempts during the late 1800s to curb over exploitation and repair degraded reefs through protection, primitive aquaculture and enhancement, living examples of shellfish reefs are now rare. Only one Ostrea angasi reef is known to exist that is comparable in size to reefs historically commercially fished, compared to at least 118 previously known locations. Out of the 60 historically fished locations identified for Saccostrea glomerata, only five are known to still contain commercially harvestable sized reefs. The introduced oyster Crasostrea gigas is increasing in reef extent, whilst data on the remaining five reef-building species is limited, preventing a detailed assessment of their current status. Our knowledge of the extent, physical characteristics, biodiversity and ecosystem services of natural shellfish reefs in Australia is extremely limited. Australia is well equipped to reverse the decline of shellfish reef ecosystems with a number of state and federal protection laws, international conventions and management mechanisms already in place, all of which can be used to help protect remaining reefs and aid in future recovery. Several restoration projects have recently begun as awareness of historical loss grows amongst the community and groups become motivated to implement repair. As momentum continues to grow, Australia could serve as a long-term model for other regions that may currently have limited understanding of their shellfish reefs ecosystems but wish to work towards their future conservation. Data to be made publicly available with publication of manuscript by end 2018.

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.