Effects of increasing water temperatures on survival and growth of ecologically and economically important seaweeds in Atlantic Canada: implications for climate change
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Rising temperatures are changing the distribution and abundance of species worldwide, yet the magnitude of warming varies regionally. Atlantic Canada lies in a zone of significant warming and harbors many cold-adapted seaweeds of ecological and economic importance. Using a factorial laboratory experiment, we tested the effects of increasing water temperature on the survival, growth, and nutrient content of rockweeds (Ascophyllum nodosum, Fucus vesiculosus), Irish moss (Chondrus crispus), kelp (Laminaria digitata), and the invasive Codium fragile ssp. tomentosoides from Nova Scotia (44°29.9′N, 63°31.7′W). In June 2014, species were exposed to typical spring–summer water temperatures (12, 16, 20 °C), a predicted increase in summer temperature (23 °C), and potential heat wave temperatures in shallow waters (26, 29 °C) for 9 weeks. Chondrus crispus and L. digitata experienced highest growth at 12 °C, F. vesiculosus and Codium at 16 °C, and A. nodosum at 20 °C. Survival was lowest in L. digitata with no survival above 20 °C, followed by rockweeds with low survival above 23 °C, while C. crispus and Codium exhibited high survival at all temperatures. There was some evidence for temporary acclimation and short-term survival at higher temperatures. Temperature stress did not affect carbon content but some species showed increased tissue nitrogen, potentially changing nutritional quality and the ability to store and cycle nutrients. These species-specific responses to increasing water temperature will result in shifts in species composition along Atlantic Canada’s rocky shore, altering seaweed canopies, their ecosystem structure and function, and the services they provide.
KeywordsMacroalgae Nova Scotia Increase Water Temperature Ascophyllum Nodosum Warm Water Temperature
Financial support for this study was provided by the Natural Sciences and Engineering Research Council (NSERC) of Canada with a grant to HKL and an Undergraduate Research Award to KLW, as well as a Sarah Lawson Research Scholarship to KLW. We thank B. Worm for his aid in diving for macroalgae, and M. Mayer, E. Chambers, and E. Colin for helping with the many water changes.
Compliance with ethical standards
Conflict of interest
The authors declare no conflict of interest.
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