DOI: 10.5285/60b777b4-0bd6-48c3-a301-c700854fbfa1
title: Acclimation and acclimatisation of marine ectotherms collected at Rothera Research Station and Scott Base in Antarctica between 2004 and 2015

description: This data assesses the ability of 8 species, from 7 classes representing a range of functional groups, to survive, for 100 to 303 days, at temperatures 0 to 4 degrees Celsius above previously calculated long-term temperature limits. Survivors were then tested for acclimation responses to acute warming. Acclimatisation in the field was tested in the seastar Odontaster validus collected in different years, seasons and locations within Antarctica. Finally, we tested the importance of oxygen limitation in controlling survival duration by incubating 7 species under normoxia (20%) and mild hyperoxia (30%).

This study was funded by Natural Environment Research Council core funding to the British Antarctic Survey and Spitfire DTP funding to R.E.S.
description: Experiments were conducted between 2006 and 2015 with individuals hand collected by SCUBA divers in the austral summer, from 6 - 15m depth, near Rothera Research Station, Adelaide Island (67° 34' 2'' S, 68° 08' 0'' W). Common marine ectotherms were selected from different phyla to represent a range of functional groups, for which aquarium husbandry is well established and long term temperature limits have been estimated under normoxia.
All animals remained submerged throughout the transfer from the sea to the flow-through aquarium system at the station. To control for size-dependent effects on survival we selected individuals of a similar size within each species group at the start of the experiment, and only studied fully reproductive adults.

The 3.0 °C temperature-oxygen experiment was conducted in flow through aquaria at Rothera Research Station. In Rothera the tanks had a constant exchange of seawater that was balanced to allow temperature and oxygen treatments to be maintained while preventing any build-up of metabolic waste. In all experiments, seawater chemistry was monitored every 2-3 days using Nutrafin aquarium test kits. Ammonia, nitrite and nitrates were maintained well below 0.4, 0.2 and 5 mg L-1 to prevent toxicity from metabolic by-products.

A small piece of one tentacle was removed from each anemone and preserved in 96% ethanol. DNA was extracted from each tentacle using the DNeasy Blood and Tissue kit (Qiagen) according to manufacturer's instructions. The cytochrome oxidase subunit I gene (COI) mitochondrial region was amplified using 1-2 µl extracted DNA and MyTaq DNA polymerase mix (30 µl reactions; Bioline UK (now Meridien Biosceince), with 10nmol each of the universal COI primers for invertebrates (LCO 1490 5'-GGTCAACAAATCATAAAGATATTGG-3'; HCO 2198 5''''''-TAAACTTCAGGGTGACCAAAAAATCA-3') (Folmer et al. 1994). PCR conditions were: 94 °C for 5 minutes, 5 cycles of 94 °C for 1 min, 45 °C for 1.5 min, 72 °C for 1.5 min, followed by 30 cycles of 94 °C for 1 min, 50 °C for 1 min, 72 °C for 1 min and a final elongation stage of 5 min at 72 °C. The COI fragments were bi-directionally sequenced by Source Bioscience (Cambridge, UK). The species identity of each individual was analysed using Blast sequence similarity searching of INSDC (International Nucleotide Sequence Database Collaboration) (https://www.insdc.org/).

Temperatures were raised at the same rate in all experiments (0.3 ± 0.1 °C d-1) until the incubation temperature was reached and subsequently monitored daily. Animals were held at temperatures of 6.0 and 8.0 °C, temperatures that were 0 to 4 °C above the long-term limits calculated from experiments with different rates of warming. Control animals were kept at 0.0 °C in the main holding aquarium.

Acute thermal limits: Individuals that survived beyond the duration of incubations at both 6.0 and 8.0 °C were then tested to see if acute thermal limits were elevated due to acclimation to these elevated incubation temperatures. These data were compared with acute thermal limits conducted on control individuals that had been kept in the aquarium at 0.0 °C. For the acute temperature ramping trials individuals were transferred to plastic jacketed tanks (Engineering Design and Plastics Ltd), whose jackets were filled with 25 % v/v ethanol in water solution, that was heated or cooled by LTD20G thermocirculators (Grant Instruments). Temperatures were increased at 1.0 ± 0.1 °C d-1 until the last animal was no longer responding to the stimuli detailed above.

Acclimatisation in field animals was tested for in only one species, the common starfish O. validus. To test for field acclimatisation the assessment of CTmax of freshly collected O. validus was repeated between 2006 and 2015 in both summer and winter. There was also a test of individuals from Scott Base (77° 50' 5'' S, 166° 46' 0'' E) to allow for regional differences and compare with a site with even less annual and seasonal variation than Rothera. As above, temperatures were increased at 1.0 ± 0.1 °C d-1 until the last animal was no longer responding to the stimuli. For analysis field temperature from the Rothera Time Series was measured by CTD (conductivity, temperature, depth) casts at 15m depth and was averaged for the month of animal collection.

Further details on methodology are in the associated manuscript.
description: All data have been quality checked by the data creators.