Abstract
Ocean warming and acidification are current global environmental challenges impacting aquatic organisms. A shift in conditions outside the optimal environmental range for marine species is likely to generate stress that could impact metabolic activity, with consequences for the biosynthesis of marine lipids. The aim of this study was to investigate differences in the lipid content of Dicathais orbita exposed to current and predicted future climate change scenarios. The whelks were exposed to a combination of temperature and CO2-induced acidification treatments in controlled flowthrough seawater mesocosms for 35 days. Under current conditions, D. orbita foot tissue has an average of 6 mg lipid/g tissue, but at predicted future ocean temperatures, the total lipid content dropped significantly, to almost half. The fatty acid composition is dominated by polyunsaturated fatty acids (PUFA 52%) with an n-3:6 fatty acid ratio of almost 2, which remains unchanged under future ocean conditions. However, we detected an interactive effect of temperature and pCO2 on the % PUFAs and n-3 and n-6 fatty acids were significantly reduced by elevated water temperature, while both the saturated and monounsaturated fatty acids were significantly reduced under increased pCO2 acidifying conditions. The present study indicates the potential for relatively small predicted changes in ocean conditions to reduce lipid reserves and alter the fatty acid composition of a predatory marine mollusc. This has potential implications for the growth and survivorship of whelks under future conditions, but only minimal implications for human consumption of D. orbita as nutritional seafood are predicted.
Highlights
Climate change is one of the major environmental challenges to humankind and all other life forms on Earth
The highest lipid content from D. orbita foot tissue was 6.3 mg/g fresh weight in specimens held at current ocean conditions of 23 °C, current pressure of atmospheric CO2 (pCO2), dropping to an average of 5.0 mg/g in specimens maintained at 23 °C and future pCO2 (Figure 1)
The reduced lipid content under elevated water temperature conditions in this study suggests that D. orbita is sensitive to the relatively small increases (~2 °C) in temperature predicted from global climate change models [1]
Summary
The consequences of the global climate change have been widely reported [1,2,3] and are likely to worsen over the coming decades. From anthropogenic activities, such as burning of fossil fuels, agriculture and land clearing [1]. These two phenomena, ocean warming and pCO2-induced acidification, are anticipated to have detrimental effects on seawater quality and to marine organisms. Marine molluscs are considered good models for climate change studies because they are ectothermic animals with limited ability to regulate their internal temperature
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