University of Otago, MSc

Oxidative stress in Antarctic and non-Antarctic sea urchin larvae

Austral spring-time ozone depletion over the Antarctic in the last 25 years has increased the amount of biologically harmful ultraviolet-B (UV-B) radiation entering the marine environment (Karentz, 1991). In addition, the Southern Ocean may experience future increases in UV-B penetration if sea ice, which is relatively opaque, decreases in spatial and temporal extent as a result of global warming (Holland et al., 2006).  Undoubtedly, climate change will influence Antarctic marine ecosystems and species in a number of ways.

I am primarily interested in the effects of climate change on marine invertebrate embryos and larvae as their development and survival are substantially affected by environmental conditions. Oxidative stress - the production and accumulation of reactive oxygen species (ROS) - is an important component of the stress response in marine organisms exposed to UV-R, and can damage lipids, proteins and DNA (Lesser, 2006).  This may be especially important for Antarctic marine species because of the very high oxygen concentration in Antarctic seawater, although there are few published studies examining oxidative stress in polar ectotherms (Abele et al., 1998, Heise et al., 2003).

My research aims to examine the degree of oxidative stress in the Antarctic sea urchin Sterechinus neumayeri as a function of UV-R exposure.  To gain a measure of this, the activity of a range of antioxidant enzymes that are involved in defense systems, including superoxide dismutase (SOD), ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR) and glutathione reductase (GR) will be evaluated via biochemical assays. Antioxidant activity in embryos of several other sea urchin species from a range of latitudes will also be quantified: Evechinus chloroticus, Pseudechinus huttoni (New Zealand), Diadema savignyi and Tripneustes gratilla (Cook Islands). Quantifications will be made using in situ experimental techniques, standardised to allow direct comparisons among species. Captive embryos will be held on moored experimental racks for 1 to 13 days (depending on development rates) and exposed to one of 3 light treatments: (1) full ambient light (UVT); (2) visible light but no UV-R (UVO); or (3) visible light and UV-A, but no UV-B (UVA). The outcome of these physiological comparisons will be a greater understanding of the importance of oxidative stress in colder waters and under changing UV-R conditions and will thus provide insight into underlying differences among polar versus non-polar species that may be significant under future climate change scenarios.

Publications

Lister, K.  Oxidative damage and aspects of antioxidant defense in Antarctic and non-Antarctic sea urchin embryos in response to UV-B radiation.  M.Sc, University of Otago, 2009.  79pp.

Lister, K.N., Lamare, M.D., Burritt, D.J. Sea ice protects the embryos of the Antarctic sea urchin Sterechinus neumayeri from oxidative damage due to naturally enhanced levels of UV-B radiation. Journal of experimental biology 213: 1967-1975 2010. doi:10.1242/jeb.039990