Temperature is the evil twin: effects of increased temperature and ocean acidification on reproduction in a reef fish.

Reproduction in many organisms can be disrupted by changes to the physical environment, such as those predicted to occur during climate change. Marine organisms face the dual climate change threats of increasing temperature and ocean acidification, yet no studies have examined the potential interactive effects of these stressors on reproduction in marine fishes. We used a long-term experiment to test the interactive effects of increased temperature and CO2 on the reproductive performance of the anemonefish, Amphiprion melanopus. Adult breeding pairs were kept for 10 months at three temperatures (28.5°C [+0.0°C], 30.0°C [-1.5°C] and 31.5°C [+3.0°C]) cross-factored with three CO2 levels (a current-day control [417 µatm] and moderate [644 µatm] and high [1134 µatm]) treatments consistent with the range of CO2 projections for the year 2100. We recorded each egg clutch produced during the breeding season, the number of eggs laid per clutch, average egg size, fertilization success, survival to hatching, hatchling length, and yolk provisioning. Adult body condition, hepatosomatic index, gonadosomatic index, and plasma 17ß-estradiol concentrations were measured at the end of the breeding season to determine the effect of prolonged exposure to increased temperature and elevated. CO2 on adults, and to examine potential physiological mechanisms for changes in reproduction. Temperature had by far the stronger influence on reproduction, with clear declines in reproduction occurring in the +1.5°C treatment and ceasing altogether in the +3.0°C treatment. In contrast, CO2 had a minimal effect on the majority of reproductive traits measured, but caused a decline in offspring quality in combination with elevated temperature. We detected no significant effect of temperature or Co2 on adult body condition or hepatosomatic index. Elevated temperature had a significant negative effect on plasma 17ß-estradiol concentrations, suggesting that declines in reproduction with increasing temperature were due to the thermal sensitivity of reproductive hormones rather than a reduction in energy available for reproduction. Our results show that elevated temperature exerts a stronger influence than high CO2 on reproduction in A. melanopus. Understanding how these two environmental variables interact to affect the reproductive performance of marine organisms will be important for predicting the future impacts of climate change.

Terrestrial pollutant runoff to the Great Barrier Reef: An update of issues, priorities and management responses.

The Great Barrier Reef (GBR) is a World Heritage Area and contains extensive areas of coral reef, seagrass meadows and fisheries resources. From adjacent catchments, numerous rivers discharge pollutants from agricultural, urban, mining and industrial activity. Pollutant sources have been identified and include suspended sediment from erosion in cattle grazing areas; nitrate from fertiliser application on crop lands; and herbicides from various land uses. The fate and effects of these pollutants in the receiving marine environment are relatively well understood. The Australian and Queensland Governments responded to the concerns of pollution of the GBR from catchment runoff with a plan to address this issue in 2003 (Reef Plan; updated 2009), incentive-based voluntary management initiatives in 2007 (Reef Rescue) and a State regulatory approach in 2009, the Reef Protection Package. This paper reviews new research relevant to the catchment to GBR continuum and evaluates the appropriateness of current management responses.

Equivalent whole-body concentrations of 11-ketotestosterone in female and male coral goby Gobiodon erythrospilus, a bidirectional sex-changing fish.

The relationship between whole-body concentrations of 11-ketotestosterone (11-KT) and sexual function was examined in the coral goby Gobiodon erythrospilus, a bi-directional sex-changing fish. 11-KT occurred in both female and male G. erythrospilus, but levels were not always higher in males than in females within heterosexual pairs, and were not related to the stage of gonadal development of individual fish. These results suggest that comparable 11-KT levels in both sexes may allow serial adult sex change to take place in bi-directional sex-changing species, such as Gobiodon spp.

The role of steroid hormones in protogynous sex change in the Blackeye goby, Coryphopterus nicholsii (Teleostei: Gobiidae).

To detect and describe correlations between steroid concentrations and sexual function in the protogynous Coryphopterus nicholsii, we examined whole-body concentrations of the gonadal steroids testosterone (T), 11-ketotestosterone (11-KT), and 17beta-estradiol (17beta-E2). Our results show that T, 11-KT, and 17beta-E2 are naturally occurring steroids in both female and male C. nicholsii. Further, mean whole-body concentrations of T and 11-KT in males were approximately twice those in females, whereas mean whole-body concentration of 17beta-E2 in females was almost twice that in males. Second, we tested hypotheses on the causation of sex change arising from these correlations between steroid concentrations and sexual function. We examined the effects of administration of 11-KT, 11-KA, 17alpha-methyltestosterone, and an aromatase inhibitor (Fadrozole) on gonadal structures of mature females. Complete sex change was induced by 11-KT, 11-KA, and Fadrozole. Our results strongly suggest that an increase in 11-KT concentration and perhaps also a decrease in 17beta-E2 concentration are involved in mediating natural sex change in C. nicholsii.