(Table 1) Breeding parameters for 60 male Adélie penguins (Pygoscelis adeliae) at station Dumont d'Urville (Antarctica) depending on treatment (control vs. CORT)

Corticosterone, the main stress hormone in birds, mediates resource allocation, allowing animals to adjust their physiology and behaviour to changes in the environment. Incubation is a time and energy-consuming phase of the avian reproductive cycle. It may be terminated prematurely, when the parents' energy stores are depleted or when environmental conditions are severe. In this study, the effects of experimentally elevated baseline corticosterone levels on the parental investment of incubating male Adelie penguins were investigated. Incubation duration and reproductive success of 60 penguins were recorded. The clutches of some birds were replaced by dummy eggs, which recorded egg temperatures and rotation rates, enabling a detailed investigation of incubation behaviour. Corticosterone levels of treated birds were 2.4-fold higher than those of controls 18 days post treatment. Exogenous corticosterone triggered nest desertion in 61% of the treated birds; consequently reducing reproductive success, indicating that corticosterone can reduce or disrupt parental investment. Regarding egg temperatures, hypothermic events became more frequent and more pronounced in treated birds, before these birds eventually abandoned their nest. The treatment also significantly decreased incubation temperatures by 1.3 °C and lengthened the incubation period by 2.1 days. However, the number of chicks at hatching was similar among successful nests, regardless of treatment. Weather conditions appeared to be particularly important in determining the extent to which corticosterone levels affected the behaviour of penguins, as treated penguins were more sensitive to severe weather conditions. This underlines the importance of considering the interactions of organisms with their environment in studies of animal behaviour and ecophysiology.

Larval and post-larval stages of pacific oyster (Crassostrea gigas) are resistant to elevated CO2

Rising anthropogenic carbon dioxide (CO2) dissolving into coastal waters is decreasing the pH and carbonate ion concentration, thereby lowering the saturation state of calcium carbonate (CaCO3) minerals through a process named ocean acidification (OA). The unprecedented threats posed by such low pH on calcifying larvae of several edible oyster species have not yet been fully explored. Effects of low pH (7.9, 7.6, 7.4) on the early growth phase of Portuguese oyster (Crassostrea angulata) veliger larvae was examined at ambient salinity (34 ppt) and the low-salinity (27 ppt) treatment. Additionally, the combined effect of pH (8.1, 7.6), salinity (24 and 34 ppt) and temperature (24 °C and 30 °C) was examined using factorial experimental design. Surprisingly, the early growth phase from hatching to 5-day-old veliger stage showed high tolerance to pH 7.9 and pH 7.6 at both 34 ppt and 27 ppt. Larval shell area was significantly smaller at pH 7.4 only in low-salinity. In the 3-factor experiment, shell area was affected by salinity and the interaction between salinity and temperature but not by other combinations. Larvae produced the largest shell at the elevated temperature in low-salinity, regardless of pH. Thus the growth of the Portuguese oyster larvae appears to be robust to near-future pH level (> 7.6) when combined with projected elevated temperature and low-salinity in the coastal aquaculture zones of South China Sea.

Effects of elevated pCO2 on the post-settlement development of Pocillopora damicornis

Ocean acidification represents a key threat to the recruitment of scleractinian corals. Here, we investigated the effect of increased partial pressure of carbon dioxide (pCO2) on the early development of Pocillopora damicornis by rearing the recruits for 12 days at 3 pCO2 levels (446, 896 and 1681 µatm). Results showed that increased pCO2 exerted minor effects on symbiont density and maximum quantum yield (Fv/Fm), while significantly enhanced the relative electron transport through photosystem II (PSII) of Symbiodinium. Notably, calcification and biomass of recruits decreased sharply by 34% and 24% respectively in 896 µatm, and tended to remain constant as pCO2 was raised from 896 to 1681 µatm. Furthermore, recruits in 1681 ?atm, with comparable surface area as those in 896 µatm, produced fewer buds. These findings indicated that juvenile P. damicornis under high pCO2 would enhance electron transport rate and suppress asexual budding to favor skeletal and tissue growths, which are more critical for their persistence and survival in a high pCO2 environment. This work suggested the physiological plasticity of juvenile corals under short-term exposure to elevated pCO2.