An aerial survey was conducted for giant kelp (Macrocystis pyrifera) on the east coast of Tasmania from Eddystone Point to Southeast Cape. This survey represents part of a series of similar surveys, with historic aerial surveys having been conducted in 1986 and 1999. The survey was conducted via light aircraft. Areas of visable Macrocystis pyrifera beds were marked on topographical land tenure maps using landmarks as references, and complimentary photo footage was collected.

Giant kelp (Macrocystis pyrifera) forests are a foundational habitat that dominates many nearshore rocky coastlines in temperate and cold-water regions worldwide. Macrocystis forests can extend as much as 40 m to the surface and form closed canopies that alter the light, current, and sedimentation environment beneath them. They play an ecosystem-structuring function and provide habitat for a diverse range of fish and invertebrate species. The coastal waters of Tasmania represent the most extensive giant kelp habitat in Australia. Dense forests have historically covered large areas of the nearshore reef habitat, but significant declines have been recorded in eastern Tasmania in recent decades. These losses are thought to be linked to environmental stressors such as extended periods of high water movement, warming sea temperatures, and nutrient depletion. Eastern Tasmania has experienced some of the most pronounced declines, leading to the 2012 listing of the giant kelp community as an ‘endangered marine community type’ under Australia’s Federal Environment Protection and Biodiversity Conservation Act. This dataset uses Landsat satellite imagery to quantifiy the spatial extent and temporal variability of giant kelp surface canopies along the Tasmanian coastline to address gaps in long-term monitoring. The data collection is divided into two components: 1) A statewide analysis that maps the extent of Macrocystis pyrifera canopies across the whole Tasmanian coastline, grouped into nine three-year bins spanning 1987–2015. This long-term dataset is intended for assessing long-term (decadal) changes at a broad spatial scale. 2) A higher temporal-resolution analysis of 24 specific sites along the Tasmanian coastline. This dataset includes canopy coverage from all cloud-free Landsat imagery captured over the period 1986-2015 to enable detailed analysis of seasonal and interannual fluctuations in kelp canopy extent and understand localised population dynamics.

An aerial survey of giant kelp (Macrocystis pyrifera), was carried out on the east coast of Tasmania from Musselroe Bay to Southeast Cape. This survey represents part of a series of similar surveys, with historic aerial surveys having been conducted in 1986, 1999 and 2009. This survey was conducted via light aircraft in Nov-Dec 2019, and recorded areas of visible surface canopy cover of giant kelp. Canopy areas were scribed in-flight onto 1:50,000 topographic maps (TASMAP 2017), and complimentary photo and video footage was collected. Canopy areas were digitised with reference to photo, video and map data within QGIS 3.4, and boundaries were checked against Seamap Australia seafloor habitats (Lucieer et al. 2017) and bathymetric data (Smith 2016). Each bed was attributed a broad and fine scale location, density and reliability estimate (see attached report for details). This survey was completed with funding from Pennicott Wilderness Journeys, Tassal and IMAS, and equal in-kind support by Marine Solutions and Seacare Inc.

This record describes an aggregated data product compiled from a number of different surveys of Macrocystis surface cover in Tasmanian waters, spanning 1950 to 2019. Some surveys represent a statewide census of Macrocystis cover, while others are targeted surveys of smaller regions. Methodology and data quality may also vary between surveys. Please see linked metadata records for specific methodologies and quality statements applying to individual surveys.

Data accompanying Layton et al. 2019, Resilience and stability of kelp forests: the importance of patch dynamics and environment-engineer feedbacks. PLOS ONE. To explore how resilience and stability of kelp habitats is influenced by this habitat degradation, we created an array of patch reefs of various sizes and supporting adult Ecklonia radiata kelp transplanted at different densities. This enabled testing of how sub-canopy abiotic conditions change with reductions in patch size and adult kelp density, and how this influenced demographic processes of microscopic and macroscopic juvenile kelp.

-- Layton et al. Chemical microenvironments within macroalgal assemblages: implications for the inhibition of kelp recruitment by turf algae. Limnology & Oceanography. DOI:10.1002/lno.11138 -- Kelp forests around the world are under increasing pressure from anthropogenic stressors. A widespread consequence is that in many places, complex and highly productive kelp habitats have been replaced by structurally simple and less productive turf algae habitats. Turf algae habitats resist re-establishment of kelp via recruitment inhibition; however little is known about the specific mechanisms involved. One potential factor is the chemical environment within the turf algae and into which kelp propagules settle and develop. Using laboratory trials, we illustrate that the chemical microenvironment (O2 concentration and pH) 0.0–50 mm above the benthos within four multispecies macroalgal assemblages (including a turf-sediment assemblage and an Ecklonia radiata kelp-dominated assemblage) are characterised by elevated O2 and pH relative to the surrounding seawater. Notably however, O2 and pH were significantly higher within turf-sediment assemblages than in kelp-dominated assemblages, and at levels that have previously been demonstrated to impair the photosynthetic or physiological capacity of kelp propagules. Field observations of the experimental assemblages confirmed that recruitment of kelp was significantly lower into treatments with dense turf algae than in the kelp-dominated assemblages. We demonstrate differences between the chemical microenvironments of kelp and turf algae assemblages that correlate with differences in kelp recruitment, highlighting how degradation of kelp habitats might result in the persistence of turf algae habitats and the localised absence of kelp.