Hong D. Nguyen

Temperature, but not pH, compromises sea urchin fertilization and early development under near-future climate change scenarios

Global warming is causing ocean warming and acidification. The distribution of Heliocidaris erythrogramma coincides with the eastern Australia climate change hot spot, where disproportionate warming makes marine biota particularly vulnerable to climate change. In keeping with near-future climate change scenarios, we determined the interactive effects of warming and acidification on fertilization and development of this echinoid. Experimental treatments (20–26°C, pH 7.6–8.2) were tested in all combinations for the ‘business-as-usual’ scenario, with 20°C/pH 8.2 being ambient. Percentage of fertilization was high (>89%) across all treatments. There was no difference in percentage of normal development in any pH treatment. In elevated temperature conditions, +4°C reduced cleavage by 40 per cent and +6°C by a further 20 per cent. Normal gastrulation fell below 4 per cent at +6°C. At 26°C, development was impaired. As the first study of interactive effects of temperature and pH on sea urchin development, we confirm the thermotolerance and pH resilience of fertilization and embryogenesis within predicted climate change scenarios, with negative effects at upper limits of ocean warming. Our findings place single stressor studies in context and emphasize the need for experiments that address ocean warming and acidification concurrently. Although ocean acidification research has focused on impaired calcification, embryos may not reach the skeletogenic stage in a warm ocean.

Protein Analysis in Large Benthic Foraminifera

Large benthic foraminifera (LBFs) have long been used as environmental recorders of ocean chemistry. Although the importance of foraminifera in paleo-reconstructions of ancient oceans and as sediment producers is well documented, the biology of tropical symbiont-bearing foraminifera has only recently gained increased attention. Tropical symbiont-bearing LBFs represent a unique and important subset of LBFs in that they are vital to coral-reef ecosystems and host a wide suite of algal symbionts (e.g., dinoflagellates, diatoms, red algae, green algae and cyanobacteria). Previous studies on both host and symbiont physiology have been performed in order to gauge the foraminiferal response to a variety of stressors, including elevated temperature and nutrient levels, as well as acidification. Recently, protocols have been developed for protein analysis in LBFs that will allow for expression analyses of target proteins from both members of the holobiont. In this chapter, we detail a protein expression protocol for one-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis (1-D SDS-PAGE) and consequent western blotting for determination of protein expression in the foraminiferal holobiont. This technique has the potential to target proteins that are specific to either host or symbiont compartments, a breakthrough that may ultimately allow for an increased understanding of the molecular-scale regulation of the symbiosis that is vital to these globally important calcifiers.