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Temporal and spatial variability in stable isotope values on seabird islands: what, where and when to sample
Invasive mammal eradications are widely used for managing island ecosystems. However, tracking the outcomes of such large-scale, whole ecosystem projects is challenging and costly, and monitoring all components of an ecosystem is near impossible. Instead, indicators of ecosystem change may provide more practical and integrated measures of ecosystem response to eradications. As high-order marine predators, seabirds subsidise island ecosystems with nutrients isotopically enriched in nitrogen. Invasive mammals have caused a global decline of seabirds on islands, reducing this nutrient subsidisation. Following eradications, nitrogen stable isotope analysis may provide a useful and resource-efficient indicator of ecosystem functional change on eradicated islands. However, isotope ratios are affected by a myriad of factors, with potential sources of variation being introduced by spatial and temporal variation in sampling, and within and between different taxa and ecosystem components. To correctly attribute isotopic change to post-eradication ecosystem function change, these confounding variables need to be understood. To address this need, we analysed stable isotopes of nitrogen in soil, plant, spider, and seabird guano samples collected at different distances from seabird colonies and at different stages of the short-tailed shearwater breeding cycle on six island sites around south-eastern Tasmania, Australia. Across these cool, temperate islands we detected no temporal variability in δ15N throughout the breeding season. However, there was notable spatial variability in δ15N values. The effects of seabird-derived nutrient subsidisation were highly localised with high δ15N values found inside seabird colonies and then rapidly decreasing from the colony boundary. Higher δ15N values also occurred in areas of higher burrow density within a colony. Variability in δ15N values also existed both within and between ecosystem components. Our results highlight the importance of context dependency when using ecological indicators and have important implications for the design, implementation and interpretation of studies employing stable isotopes as indicators for ecosystem change. We provide recommendations for designing future stable isotope studies on seabird islands.
This data is from the 2021 Seeds for Snapper season which is a community volunteer seed based seagrass restoration program located in Perth, Western Australia. It details the effort that went into the collection of Posidonia australis seagrass fruit including number of divers, number of shore support personnel, volunteered hours, and fruit collection metrics (volume, estimated number).
Here, we hypothesize that Fe uptake rates by sea-ice algae and under-ice phytoplankton are higher than the rates reported for open ocean phytoplankton in the SO. We performed 55Fe and carbon (14C) short-term uptake field measurements in, on and under Antarctic sea ice. We collected under ice seawater, melted snow and sea-ice cores. We then spiked them with 14C or 55Fe radiotracers to measure Fe and C uptake rates by sea-ice algae. Samples were then filtered, and residual radioactivity on the filters measured liquid scintillation counter (Packard).
Collection of processed BGC-Argo float profiles, used to calculate phytoplankton phenology from chlorophyll, phytoplankton carbon and nitrate.
Seagrass meadows extents derived from field to spaceborne earth observation at Midge Point, Great Barrier Reef, September/October 2017
Seagrass meadow extent and meadow-scape was mapped using three alternative approaches at Midge Point, a coastal turbid water habitat, in the central section of the Great Barrier Reef, in September/October 2017. Approach 1 included mapping meadow boundaries and meadow-scape during low spring tides on foot using a handheld Garmin GPS. Approach 2 was where the meadows were surveyed at low tide with observations from a helicopter, with observational spot-checks conducted at a number haphazardly scattered points. Approach 3 used PlanetScope Dove imagery captured on 09 October 2017 coinciding as close as possible to the field-surveys, with 3.7 m x 3.7 m pixels (nadir viewing) acquired from the PlanetScope archive. This record describes meadow extent data collected using Approach 3 (PlanetScope imagery). View the original metadata record at https://doi.org/10.1594/PANGAEA.946606 for the full data collection.
Seagrass meadow extents derived from field to spaceborne earth observation at Green Island (Wunyami), a reef habitat in the Cairns section of the Great Barrier Reef, November 2020
Seagrass meadow extent and meadow-scape was mapped using two alternative approaches at Green Island, a reef clear water habitat, in the Cairns section of the Great Barrier Reef, in November 2020. Approach 1 included mapping seagrass meadow-scape using imagery captured during low spring tides with a DJI Mavic 2 Pro UAV at an altitude of 100 m, with a resolution of 2.45cm/pixel. Approach 2 used PlanetScope Dove imagery captured on 05 November 2020 coinciding as close as possible to the field-surveys from 25 to 27 November 2020, with 3.7 m x 3.7 m pixels (nadir viewing) acquired from the PlanetScope archive. This record describes meadow extent data collected using Approach 2 (PlanetScope imagery). View the original metadata record at https://doi.pangaea.de/10.1594/PANGAEA.946605 for the full data collection.
Tidal wetlands are vulnerable to accelerated rates of sea-level rise projected by climate models. The Surface Elevation Table (SET) is a technique applied globally to assess the extent of vertical adjustment of tidal wetlands to sea-level rise over decadal timescales. This record describes the SET data from the Australian network (OzSET). This data can be used for analyzing wetlands elevation change at the study sites
In March 2020 UWA and the Malgana Rangers transplanted by hand 36 pieces of Posidonia australis and Amphibolis antarctica into nearby restoration plots at Dubaut Point, Shark Bay. In March 2022 UWA went back to assess survival and shoot growth which is detailed in this dataset.
Assessing the influence of ocean alkalinity enhancement on a coastal phytoplankton community - manuscript data
The effect of ocean alkalinity enhancement on a coastal phytoplankton community was assessed via a microcosm experiment. The effect of alkalinity enhancement in two scenarios (i) when enclosed seawater was in equilibrium with atmospheric CO2 and (ii) when enclosed seawater was not in equilibrium with atmospheric CO2 were explored. Alkalinity was increased by ~497 umol/kg in these two treatments and plankton communities, carbonate chemistry, dissolved inorganic nutrients, particulate matter and chlorophyll a dynamics monitored over a 22 day period where a spring bloom occurred.
Code and data for: The effect of seabird presence and seasonality on ground-active spider communities across temperate islands
We investigated the effects of seabird presence and seasonality on ground-active spider community structure (activity-density, family-level richness, age class and sex structure) and composition at the family-level across five short-tailed shearwater breeding islands around south-eastern Tasmania, Australia. Using 75 pitfall traps (15 per island), spiders were collected inside, near and outside seabird colonies on each island, at five different stages of the short-tailed shearwater breeding cycle over a year. 3. Pitfall traps were deployed for a total of 2,674 days, capturing 1,592 spiders from 26 families with Linyphiidae and Lycosidae the most common.