(Table 1) Diving behaviour of male Adélie penguins (Pygoscelis adeliae) with and without corticosterone implants at Pointe Géologie

The amount of energy that organisms can allocate to self-maintenance and/or reproduction largely depends on their foraging strategies. Because of corticosterone (CORT) involvement in the control of energy metabolism, food intake and locomotor activity, recent studies have sought to demonstrate the role of this hormone in foraging decisions and performance. Moreover, considerable recent advances in animal-attached loggers now allow the study of behaviour in free-living animals. In order to assess the effects of CORT administration on the foraging behaviour of free-living Adelie Penguins Pygoscelis adeliae, we studied a group with CORT implants and a control group without CORT implants, by attaching time-depth recorders to the two groups and monitoring them throughout up to seven consecutive foraging trips during the guard stage (in Adelie Land, Antarctica). We found that foraging trips duration was similar between both groups. Dive durations, time spent at the bottom phase of dives, and the number of undulations per dive of CORT-implanted birds were all significantly higher than those of controls. However, CORT-implanted birds performed fewer dives overall (ca. 4,400) than controls (ca. 6,250) and spent many (13 and 6 times for penguins #3 and #4, respectively) long periods (>3 h) without diving. The low foraging effort and long resting periods support the view that CORT-implanted birds probably gained less energy than did the control birds. CORT treatment appears then to result in redirecting bird behaviour from costly activity (i.e. reproduction) to a behaviour promoting the preservation of energy reserves. Future studies are therefore needed to assess body condition and reproductive success of CORT-manipulated birds in parallel with the recording of their diving performances.

Seawater carbonate chemistry and giant kelp Macrocystis pyrifera reproduction processes during experiments, 2011

The worldwide effects of ocean acidification (OA) on marine species are a growing concern. In temperate coastal seas, seaweeds are dominant primary producers that create complex habitats and supply energy to higher trophic levels. Studies on OA and macroalgae have focused on calcifying species and adult stages but, critically, they have overlooked the microscopic stages of the reproductive life cycle, which, for other anthropogenic stress e.g. UV-B radiation, are the most susceptible life-history phase. Also, environmental cues and stressors can cause changes in the sex ratio which has implications for the mating system and recruitment success. Here, we report the effects of pH (7.59-8.50) on meiospore germination and sex determination for the giant kelp, Macrocystis pyrifera (Laminariales), in the presence and absence of additional dissolved inorganic carbon (DIC). Lowered pH (7.59-7.60, using HCl-only) caused a significant reduction in germination, while added DIC had the opposite effect, indicating that increased CO2 at lower pH ameliorates physiological stress. This finding also highlights the importance of appropriate manipulation of seawater carbonate chemistry when testing the effects of ocean acidification on photosynthetic organisms. The proportion of male to female gametophytes did not vary significantly between treatments suggesting that pH was not a primary environmental modulator of sex. Relative to the baseline (pH 8.19), gametophytes were 32% larger under moderate OA (pH 7.86) compared to their size (10% increase) under extreme OA (pH 7.61). This study suggests that metabolically-active cells can compensate for the acidification of seawater. This homeostatic function minimises the negative effects of lower pH (high H+ ions) on cellular activity. The 6-9% reduction in germination success under extreme OA suggests that meiospores of M.pyrifera may be resistant to future ocean acidification.