An extreme marine environment: a 14-month record of temperature in a polar tidepool
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ORIGINAL PAPER
An extreme marine environment: a 14‑month record of temperature in a polar tidepool Andrew Clarke1 · Jennifer C. Beaumont1,2 Received: 23 December 2019 / Revised: 30 September 2020 / Accepted: 7 October 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Tidepools are not uncommon in Antarctica, but there appear to be no data on the physical environment within polar tidepools and only anecdotal information on their biology. Here we report a high resolution record of temperature in an Antarctic tidepool made over two summers and the intervening winter. During the summer open water season the highest daily mean, and also the maximum temperatures, were recorded during the period of continuous daylight around the summer solstice. This short-term variability of temperature in the tidepool greatly exceeded that in the nearby open ocean, indicating the need for a eurythermal physiology in tidepool biota. In winter the tidepool froze over, the unfrozen water cooled to − 5.5 °C, and freeze concentration increased its salinity to roughly three times normal seawater. A polar tidepool isolated from the sea in winter is probably inimical to many larger marine organisms, which must populate the tidepool afresh each summer. Keywords Ice · Salinity · Seasonality · Temperature · Tidepool · Variability
Introduction Tidepools are tough places to live. When exposed to the sun at low tide, water temperatures can rise significantly, but also fall rapidly when inundated by the flooding tide. Salinity can increase with evaporation or decrease with rainwater input, and in polar regions there is dilution by meltwater, scour by brash ice and the likelihood of the surface freezing over in winter. These fluctuations in temperature and salinity in turn drive variability in oxygen and C O2 content, as well as pH. This marked variability in environmental conditions makes tidepools a challenging environment for life (Ricketts et al. 1985; Little and Kitchen 1996; Tomanek and Helmuth 2002; Denny and Gaines 2007; Firth and Williams 2016). Tidepools have been studied extensively in temperate and tropical latitudes. Their location renders them accessible, and their discrete nature makes them ideal test beds for ecological theory (Naylor and Slinn 1958; Morris and Taylor 1983; Denny and Gaines 2007; Hawkins et al. 2016). Studies
to date have shown that tidepools at lower latitudes support food-webs having a structure and network properties comparable with larger bodies of water, and also with terrestrial systems (Mendonça et al. 2018). It remains an open question whether polar tidepools have assemblages simpler (that is with fewer species) than those elsewhere, as is the case for polar terrestrial systems, or whether they are comparable in species richness with the nearby open ocean. Critical to understanding these patterns will be the physical environmental conditions within polar tidepools. Tidepools are not uncommon in Antarctica and whilst there have been a few anecdotal studies documenting the domina
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