Coral-associated invertebrates: Diversity, ecological importance and vulnerability to disturbance

Abstract

Abstract Global warming and increased atmospheric CO2 are causing the oceans to warm, decrease in pH and become hypercapnic. These stressors have deleterious impacts on marine invertebrates. Increasing temperature has a pervasive stimulatory effect on metabolism until lethal levels are reached, whereas hypercapnia has a narcotic effect. Ocean acidi™cation is a major threat to calcifying larvae because it decreases availability of the carbonate ions required for skeletogenesis and also exerts a direct pH effect on physiology. Marine invertebrate propagules live in a multistressor world and climate change stressors are adding to the mix. Ocean pH, pCO2 and CaCO3 covary and will change simultaneously with temperature, challenging our ability to predict future outcomes for marine biota. To address questions of future vulnerabilities, data on the thermo-and pH/pCO2 tolerance of fertilization and development in marine invertebrates are reviewed in the context of the change in the oceans that are forecast to occur over the next 100-200 years. Gametes and fertilization in many invertebrates exhibit a broad tolerance to warming and acidi™cation beyond stressor values projected for 2100. Available data show that all development stages are highly sensitive to warming. Larvae may be particularly sensitive to acidi™cation/hypercapnia. Embryos that develop through the bottleneck of mortality due to warming may succumb as larvae to acidi™cation. Early juveniles may be vulnerable to skeletal dissolution, although warming may diminish the negative impact of acidi™- cation on calci™cation. The effects of climate change stressors and their interaction differ among life history stages and species. Multistressor experiments show that if thermal thresholds are breached, embryos may not reach the calcifying stage. If the bottleneck for species persistence is embryonic thermotolerance, then the question of compromised calici™cation due to acidi™cation may not be relevant. Our limited knowledge of the interactive effects of climate change stressors is a major knowledge gap. Although climate change is deleterious for development in a broad range of marine invertebrates, some species and regional faunas will be more resilient than others. This has implications for persistence, faunal shifts, species invasions and community function in a changing ocean.