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Video surveys of long spined sea urchin (Centrostephanus rodgersii) barrens habitat, eastern Tasmania
The spatial extent of C. rodgersii "barrens" was estimated by surveying rocky reef habitat with a towed underwater video system. Sampling took place at 13 regions along the east coast of Tasmania, each comprising 3 subsites. Substrate and habitat type were recorded using video analysis, with 4 categories of urchin barren habitat recognised (see below for definitions).
Enzyme analysis of long spined sea urchin (Centrostephanus rodgersii) on the south eastern seaboard of Australia
Sixty animals were collected from each of Bass Pt, New South Wales (lat 34°35' S, long 150°54' E; August 2000); south side of East Cove, Deal Is, Bass St. (lat 39°28.4' S, long 147°18.4' E; June 2000) and Fortescue Bay, Tasmania (lat 43°8.5' S, long 148°0.0' E; October 2000 and April 2001). To examine the genetic relationship between the three site populations of Centrostephanus rodgersii, allelic diversity and heterozygosity among the three sites was compared using BIOSYS.
Data is PCR amplification results of southern rock lobster (Jasus edwardsii) faecal material tested for sea urchin DNA (using unique primers for Centrostephanus rodgersii and Heliocidaris erythrogramma) in an attempt to determine in situ rates of consumption of sea urchins by lobsters. An efficient and non-lethal method was used to source and screen lobster faecal samples for the presence of DNA from ecologically important sea urchins. Lobster faecal samples were collected from trap caught specimens sourced in winter & summer seasons over 2 years (2009-2011) within two no-take research reserves; declared specifically for the purpose of rebuilding large predatory-capable lobsters to assess the potential for predator-driven remediation of kelp beds on rocky reefs extensively overgrazed by sea urchins (North Eastern Tasmania) and reefs showing initial signs of overgrazing (South Eastern Tasmania). Data for molecular assays showed high variability in the proportion of lobsters testing positive to sea urchins, with significant variability detected across different years and seasons but this was found to vary depending on different lobster size-classes. Sea urchin DNA was also amplifiable from sediments and urchin faeces collected from the reef surface where urchins occurred in high abundance. Furthermore, positive sea urchin DNA assays were obtainable from lobster faeces after lobsteres were fed sediment and urchin faecal material. Rates of predation obtained with genetics tests can also be compared to independent rates of urchin losses given known lobster abundances within research reserves (and at control sites). Data of changes in urchin abundances and lobster abundances are therefore also lodged as part of this record.
Growth and age across range extension region of Centrostephanus rodgersii in eastern Tasmania and morphometric comparison of urchins inhabiting kelp versus barrens habitats
The barrens-forming sea urchin Centrostephanus rodgersii has undergone poleward range extension to eastern Tasmania. This data compares growth, morphology, reproductive investment and gonad indices between individuals inhabiting barrens ('barrens-maintaining' urchins') with those found on kelp beds ('barrens-forming' urchins) in north eastern Tasmania. The data set is comprised of 3 files. The first (Centrostephanus_biometrics_kelp_vs_barrens_urch.xls) compares biometrics of urchins across 3 sites and 2 habitats in eastern Tasmania. The second (Copy_of_Centrostephanus_annual_jaw_growth_increments.xls) compares annual growth increments of urchins in kelp bed and barren habitat including an additional site in south eastern Tasmania (The Lanterns - Tasman Peninsula) to allow comparison of growth across the newly extended range. The third (Jaw_TD_allometery.xlsx) provides a conversion between the allometry of jaw length and test diameter. Ultimately a generalised growth model for the sea urchin in kelp bed habitat was obtained for eastern Tasmania.
Recent poleward range expansion of the barrens-forming sea urchin Centrostephanus rodgersii (Diadematidae) from mainland Australia to Tasmania, has emphasized the need to understand the population dynamics of this ecologically important species in Tasmania. This work informs potential population dynamics of C. rodgersii in Tasmania by examination of its reproductive ecology. Reproductive periodicity (gonad index and propensity to spawn) was assessed bimonthly for 18 months at 4 sites in eastern Tasmania. Gamete viability was assessed by fertilization and early development trials. Temperature tolerance of Tasmanian C. rodgersii larvae was also assessed to determine whether this species has undergone an adaptive shift to the cooler Tasmanian environment. There was also no evidence for an adaptive shift in reproductive phenology. Reproductive phenology was assessed by determination of peak spawning period (gonad index analysis).
Surveys of long spined sea urchin (Centrostephanus rodgersii) and barrens habitat, Kent Group, Tasmania 2000
Quantitative surveys were undertaken at four sites in the Kent Group, north eastern Tasmania (southern and northern shores of East Cove at Deal Island, Winter Cove at Deal Island, NE coast of Dover Island) by divers using underwater visual census methods to survey the reef habitat.
Range expansion of the sea urchin Centrostephanus rodgersii leads to loss of taxonomic diversity in a kelp bed habitat, eastern Tasmania
The long spined sea urchin Centrostephanus rodgersii (Diadematidae) has recently undergone poleward range expansion to eastern Tasmania (southeast Australia). This species is associated with barrens habitat which has been grazed free of macroalgae, and therefore has potentially important consequences for reef structure and biodiversity. This study used urchin removal experiments from barrens patches in eastern Tasmania to monitor the subsequent response of the macroalgae relative to unmanipulated barrens patches. In removal patches, there was a rapid proliferation of canopy-forming macroalgae (Ecklonia radiata and Phyllospora comosa), and within 24 months the algae community structure had converged with that of nearby areas without urchins. Faunal species richness was comparatively low in barrens habitat, with C. rodgersii grazing activity resulting in an estimated minimum net loss of approximately 150 taxa compared with intact macroalgal habitats.
Effect of Centrostephanus rodgersii barrens on standing stocks of abalone and rock-lobster in Tasmania
The effect of barrens formed by the long spined sea urchin, Centrostephanus rodgersii, on the standing stocks of southern rock lobsters (Jasus edwardsii) and black lip abalone (Haliotis rubra) was estimated by divers using underwater visual census methods to compare lobster and abalone abundance in barrens with that in adjacent kelp habitat. Abalone (H. rubra) and rock-lobster (J. edwardsii) populations were compared on C. rodgersii barrens and in adjacent algal-dominated habitat at the same depth and on the same substratum type at three sites in eastern Tasmania (Elephant Rock:Binalong Bay, St Helens Is, and Mistaken Cape:Maria Island). At Elephant Rock and St Helens Island , the barrens are extensive and well established Type 1 barrens, while at Mistaken Cape the barrens in 8-14 m are incipient Type 4 barrens, comprising small barren patches in the algal bed (see FRDC report for classification of barren types). Note that while there are extensive barrens in deeper water (>18 m) at Mistaken Cape, at these depths working time is limited and it was difficult to locate intact macroalgal beds on equivalent substrata.