In situ rates of DNA damage and abnormal development in Antarctic and non-Antarctic sea urchin embryos

Abstract

To understand the in situ effects of ultraviolet radiation (UV-R) on the development of planktonic embryos from a range of latitudes, we quantified rates of DNA damage (cyclobutane pyrimidine dimer [CPD] production) and abnormal development in embryos of 4 sea urchin species: Sterechinus neumayeri (Antarctica), Evechinus chloroticus (New Zealand), Diadema savignyi and Tripneustes gratilla (Cook Islands). Quantifications were made using in situ experimental techniques that were standardised to allow direct comparisons among species. Captive embryos were held on moored experimental racks for 2 to 5 d and exposed to one of 3 light treatments: (1) full ambient light; (2) visible light but no UV-R; or (3) visible light and UV-A but no UV-B. Each treatment was repeated at 3 depths (0.5, 1.0, and 4 or 5 m). Ambient UV-R irradiance was highest during the tropical exposures, although UV-R dose during experiments was greatest in Antarctica. DNA damage (CPD concentration) was significantly higher in Antarctic embryos (up to 30.8 CPDs Mb -1 DNA) compared to New Zealand (16.5 CPDs Mb -1 DNA) and tropical species (2.2 and 3.0 CPDs Mb -1 DNA, respectively), with damage decreasing with depth. DNA damage was positively related to total UV-B dose accumulated during each experiment. Exposure to UV-R increased abnormal development, with rates generally higher in Antarctic embryos. High abnormality rates were associated with both UV-B and UV-A exposure. The greater sensitivity of Antarctic embryos to UV-R is consistent with their slow metabolism, low concentrations of sunscreens, and slow rates of DNA repair compared with temperate and tropical species.

Sea ice protects the embryos of the Antarctic sea urchin Sterechinus neumayeri from oxidative damage due to naturally enhanced levels of UV-B radiation

“…In the past, the Antarctic marine environment has been exposed to relatively low levels of ultraviolet-B radiation (UV-B) due to its polar location, seasonal sea ice coverage and high atmospheric ozone (O 3 ) concentrations (McKenzie et al, 2003;Karentz et al, 2004;Lesser et al, 2004;Lamare et al, 2007). However, in recent years two relatively rapid changes to the global climate have occurred that are causing biologically important changes to the Antarctic environment.…”

“…The greatest loss of stratospheric O 3 has occurred over the Antarctic continent and the surrounding Southern Ocean, where mean austral springtime O 3 concentrations are now 40-50% lower than they were in the late 1970s (Malloy et al, 1997;Balis et al, 2009). This reduction in springtime O 3 concentrations, to less than 220 Dobson units, has resulted in the formation of the Antarctic 'ozone hole' (Madronich et al, 1998), which results in large transient increases in the levels of UV-B as the ozone hole moves across the Antarctic continent (McKenzie et al, 2003;Karentz et al, 2004;Lesser et al, 2004;Lamare et al, 2007). Although research suggests that global ozone levels are stabilizing (Häder et al, 2003), full recovery of the ozone layer is not expected for many decades (Newman et al, 2006;McKenzie et al, 2007) and hence UV-B levels are expected to remain high for the immediate future.…”

“…Although many embryonic and larval marine invertebrates do contain UV-B screening molecules in the form of mycosporine-like amino acids (MAAs), provided by the maternal parent, the levels of these molecules can vary greatly depending on the diet of the parent and are often not present at sufficiently high enough levels to provide complete protection from UV-B induced damage (Dunlap et al, 2000;Adams and Shick, 2001;Shick and Dunlap, 2002;Lamare et al, 2007). This lack of complete protection by screening molecules is compounded by the fact that springtime phytoplankton blooms and many invertebrate spawning times coincide with the development of the ozone hole, making it highly likely that they will be exposed to maximal UV-B levels (Smith et al, 1992).…”

“…Studies have already shown that increased UV-B can reduce primary productivity (Bidigare, 1989;Smith et al, 1992;Arrigo,oxygen species (ROS) such as the superoxide anion (O 2 •), hydrogen peroxide (H 2 O 2 ), and the extremely reactive hydroxyl radical (•OH) (Lesser et al, 2001;. Direct absorption of UV-B by DNA results in the formation of cyclobutane-pyrimidine dimers (CPDs) and 6-4 photoproducts, and causes increased mutation rates in phytoplankton, macroalgae, and in the eggs and larval stages of fish and other aquatic animals (Arrigo, 1994;Malloy et al, 1997;Lesser et al, 2001;Lamare et al, 2006;Tedetti and Sempéré, 2006;Lamare et al, 2007). ROS are produced continuously in living cells, largely as a normal by-product of respiration in animals, however, changes in environmental conditions that result in stress can lead to the over production of ROS (Halliwell and Gutteridge, 1999).…”

Sex and Microhabitat Influence the Allocation of Mycosporine-Like Amino Acids to Tissues in the Purple Sea Urchin, Strongylocentrotus Purpuratus

“…In benthic macroalgae, exposure to UVR reduces growth and photosynthesis and cause decreased offspring survival (Wood 1987;Wiencke et al 2000). In sea urchins, which are classic model organisms for studies of UV-effects on marine invertebrates, solar UVR can cause cyclobutane pyrimidine dimers, developmental delays, abnormalities and death in larvae (Adams and Shick 1996;Lesser et al 2004;Lamare et al 2007) and is behaviorally avoided by adults (Sharp and Gray 1962;. At the community level, UVR can reduce biomass, productivity and diversity and alter marine community composition (Worrest et al 1978;Bothwell et al 1994;Lotze et al 2002).…”