Abstract [Related publication]:
Climate change and population irruptions of crown-of-thorns sea stars (Acanthaster sp.) are two of the most pervasive threats to coral reefs. Yet, there has been little consideration regarding the synergies between ocean warming and the coral-feeding sub-adult and adult stages of this asteroid. Here, we explored the thermosensitivity of the aforementioned life stages, by assessing physiological responses to acute warming. Thermal sensitivity was assessed based on temperature-dependent maximal activity of enzymes involved in aerobic (citrate synthase) and anaerobic (lactate dehydrogenase) metabolic pathways, as well as the basal oxygen consumption rate of sub-adult and adult sea stars. Citrate synthase activity declined at a rate of -0.016 U mg-1 tissue C-1 with increasing temperature from 15 to 40 °C, with negligible activity occurring at > 35 °C. Lactate dehydrogenase activity increased with temperature at a rate of 0.088 U mg-1 tissue C-1 from 20 to 45 °C, indicating a greater reliance on anaerobic metabolism at warmer temperatures. Rates of oxygen consumption by sea stars were measured between 24 to 36 °C, and increased with increasing temperature at rates of 0.004 and 0.001 mg O2 g-1 h-1 °C-1 for sub-adults and adults, respectively. Adult sea stars exhibited evidence of thermal stress, with metabolic depression occurring from 33 °C. In contrast there was no evidence of metabolic depression in sub-adults. Here, we demonstrate that crown-of-thorns sea stars are thermosensitive, but may have some resilience to short-term marine heatwaves in the near-future.
Dataset descriptions:
The CSdata0201.csv dataset consists of details of the activity of citrate synthase (CS) U mg-1 tissue in tube feet samples from 10 sub-adult and 19 adult crown-of-thorns starfish (Acanthaster sp.) collected from the central mid-shelf of the Great Barrier Reef, measured using spectrophotometry between 15-40 °C. The dataset consists of the Starfish ID (column A), life-stage i.e. sub-adult or adult (column B), wet weight in g (column C), the collection reef (column D), the enzyme name (column E), the temperature (column F) and the enzyme activity (column G).
The LDHdata0201.csv dataset consists of details of the activity of lactate dehydrogenase (LDH) U mg-1 tissue in tube feet samples from 9 sub-adult and 19 adult crown-of-thorns starfish (Acanthaster sp.) collected from the central mid-shelf of the Great Barrier Reef, measured using spectrophotometry between 20-45 °C. The dataset consists of the Starfish ID (column A), life-stage i.e. sub-adult or adult (column B), wet weight in g (column C), the collection reef (column D), the temperature (column E) and the enzyme activity (column F).
The Acuteforrevisionnew.csv dataset consists of details of the oxygen consumption rate (standard metabolic rate) mg O2 g-1 hr-1 of 13 sub-adult and 12 adult crown-of-thorns starfish (Acanthaster sp.), measured using intermittent flow respirometry between 24 to 36 °C. The dataset consists of the Starfish ID (column A), trial number, which is equivalent to the day of measurement (column B), the temperature (column C), the life-stage i.e. sub-adult or adult (column D), the oxygen consumption rate of the whole organism (column E) the wet weight in g (column F) and the weight-specific oxygen consumption rate (column G).
The Markdown-Metab.Therm.Resp.-CoTS.-R3.html markdown document consists of the code for the statistics and graphics used in the paper entitled “Metabolic Responses of Pacific Crown-of-Thorns Sea Stars (Acanthaster sp.) to Acute Warming” in Biological Bulletin. The data for the statistics for CS activity, LDH activity and oxygen consumption rate/standard metabolic rate analysis were attained from the CSdata0201.csv, LDHdata0201.csv and Acuteforrevisionnew.csv datasets respectively. CS and LDH activity and the standard metabolic rate were analysed using polynomial linear mixed effects models, and the estimated marginal means were used for further data investigation and to create the figures. Ordinary least squares regression was used to establish the metabolic scaling exponent at each temperature. The data used for this analysis were from Acuteforrevisionnew.csv, but the data for each temperature were put into separate files for the purpose of the analysis.
Software/equipment used to create/collect the data:
Software: Pyro Oxygen Logger version 2 LabX
Equipment: UV5, Mettler-Toledo, Columbus, USA Firesting oxygen probes, Pyroscience, Aachen, Germany
Software/equipment used to manipulate/analyse the data: Software- R Studio version 3.6.3 os darwin15.6.0 Adobe After Effects
The full methodology will be made available in the publication shown in the Related Publications link below.