Abstract
Juvenile stages are often thought to be less resistant to thermal challenges than adults, yet few studies make direct comparisons using the same methods between different life history stages. We tested the resilience of juvenile stages compared to adults in 4 species of Antarctic marine invertebrate over 3 different rates of experimental warming. The species used represent 3 phyla and 4 classes, and were the soft-shelled clam Laternula elliptica, the sea cucumber Cucumaria georgiana, the sea urchin Sterechinus neumayeri, and the seastar Odontaster validus. All four species are widely distributed, locally abundant to very abundant and are amongst the most important in the ecosystem for their roles. At the slowest rate of warming used (1°C 3 days−1) juveniles survived to higher temperatures than adults in all species studied. At the intermediate rate (1°C day−1) juveniles performed better in 3 of the 4 species, with no difference in the 4th, and at the fastest rate of warming (1°C h−1) L. elliptica adults survived to higher temperatures than juveniles, but in C. georgiana juveniles survived to higher temperatures than adults and there were no differences in the other species. Oxygen limitation may explain the better performance of juveniles at the slower rates of warming, whereas the loss of difference between juveniles and adults at the fastest rate of warming suggests another mechanism sets the temperature limit here.
Highlights
Life stages of marine invertebrates have been considered to be vulnerable or fragile in relation to environmental stresses for over 100 years [1,2,3], with many species exhibiting high mortality during development and early growth and lower mortality rates with maturity [4], [5]
Juveniles are considered generally less resilient to environmental stressors [3] including temperature [11], and reduced pH [25]. We address this paradigm by testing temperature tolerances in early juveniles and adults of four species of Antarctic marine invertebrates at different rates of thermal challenge
Small juvenile O. validus and S. neumayeri were present in the red algal mat and these were held with P. antarctica throughout, with the macroalga being regularly replenished during the longer term experiments
Summary
Life stages of marine invertebrates have been considered to be vulnerable or fragile in relation to environmental stresses for over 100 years [1,2,3], with many species exhibiting high mortality during development and early growth and lower mortality rates with maturity [4], [5]. May be complex, because several marine groups grow to larger size at low temperatures [13] This has been explained as a consequence of oxygen availability [14], [15], or as a consequence of increased growth efficiency at lower temperature [16]. Increased temperature raises growth, development and metabolic rates of juvenile stages up to a critical threshold. This increases energy and resource use which may cause a energy stress and failure due to food limitation, which has been used to explain poor recruitment in coral reef fish during warm El Nino events [17], [18]
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