In vivo measurements of [Ca2+] and [CO32−] indicate biological control of carbonate chemistry at site of calcification in corals.

This paper shows that various relevant dynamical systems can be described as vector fields associated to smooth functions via a bracket that defines what we call a Leibniz structure. We show that gradient flows, some dissipative systems, and nonholonomically constrained simple mechanical systems, among other dynamical behaviors, can be described using this mathematical construction that generalizes the standard Poisson bracket currently used in Hamiltonian mechanics. The symmetries of these systems and the associated reduction procedures are described in detail. A number of examples illustrate the theoretical developments in the paper.Comment: 19 page

The identification of sea turtle behaviours is a prerequisite to predicting the activities and time-budget of these animals in their natural habitat over the long term. However, this is hampered by a lack of reliable methods that enable the detection and monitoring of certain key behaviours such as feeding. This study proposes a combined approach that automatically identifies the different behaviours of free-ranging sea turtles through the use of animal-borne multi-sensor recorders (accelerometer, gyroscope and time-depth recorder), validated by animal-borne video-recorder data. We show here that the combination of supervised learning algorithms and multi-signal analysis tools can provide accurate inferences of the behaviours expressed, including feeding and scratching behaviours that are of crucial ecological interest for sea turtles. Our procedure uses multi-sensor miniaturized loggers that can be deployed on free-ranging animals with minimal disturbance. It provides an easily adaptable and replicable approach for the long-term automatic identification of the different activities and determination of time-budgets in sea turtles. This approach should also be applicable to a broad range of other species and could significantly contribute to the conservation of endangered species by providing detailed knowledge of key animal activities such as feeding, travelling and resting.

In the context of sexual selection, animals have developed a variety of cues conveying information about the sex of an individual to conspecifics. In many colonial seabird species, where females and males are monomorphic and do not show obvious differences in external morphology, acoustic cues are an important signal for individual and sex recognition. Here, we study the vocal and morphological sex dimorphism in the King Penguin Aptenodytes patagonicus, a colonial, monomorphic seabird for which our knowledge about the role of vocalizations and morphology in mate choice is very limited. Data were collected at Possession Island, Crozet Archipelago, in a breeding colony consisting of about 16 000 breeding pairs. Using measurements of six morphological features and analysing acoustic parameters of call recordings of adult individuals, we show that King Penguins can be sexed based on a single morphological measurement of the beak with an accuracy of 79%. We found a sex‐specific syntax in adult King Penguin calls that provided a 100% accurate method to distinguish between the sexes in our study population. To confirm the method at the species level, we analysed calls recorded from King Penguin adults in Kerguelen Island, 1300 km away from our study population and found the same accuracy of the sex‐specific syntax. This sex‐specific syllable arrangement is rare in non‐passerines and is a first step in understanding the mate choice process in this species. Furthermore, it offers a cost‐effective, non‐invasive technique for researchers to sex King Penguins in the field.

Background: Reef-building corals regularly experience changes in intra and extracellular H+ concentration ([H+]) due to physiological and environmental processes. Stringent control of [H+] is required for the maintenance of homeostatic acid-base balance in coral cells and is achieved through the regulation of intracellular pH (pHi). This task is especially challenging for reef-building corals that share an endosymbiotic relationship with photosynthetic dinoflagellates (family Symbiodinaceae), which exert a significant effect on the pHi of coral cells. Despite their importance, the pH regulatory proteins involved in the homeostatic acid-base balance have been scarcely investigated in corals. Here, we reported the full characterisation in terms of genomic structure, domain topology and phylogeny of three majors H+ transporter families implicated in pHi regulation; we investigated their tissue-specific expression and we assessed the effect of seawater acidification on their level of expression.Results: We identified members of the Na+/H+ exchanger (SLC9), vacuolar-type electrogenic H+-ATP hydrolases (V-ATPase) and voltage-gated proton channels (HvCN) families in the genome and transcriptome of S. pistillata. In addition, we identified a novel member of the HvCN gene family in the cnidarian subclass Hexacorallia, which has never been described in any species to date. We also reported key residues that participate to the H+ transporters substrate specificity, protein function and regulation. Lastly, we demonstrated that some of these have different tissue expression patterns and are mostly unaffected by exposure to seawater acidification.Conclusions: In this study, we provide the first characterization of the H+ transporters genes that contribute to homeostatic acid-base balance in coral cells. This work will enrich knowledge about basic aspects of coral biology, bearing important implications for our understanding of how corals regulate their intracellular environment.

This paper includes results centered around three topics, all of them related with the nonlinear stability of equilibria in constrained dynamical systems. First, we prove an energy-Casimir type sufficient condition for stability that uses functions that are not necessarily conserved by the flow and that takes into account the asymptotically stable behavior that may occur in certain constrained systems, such as Poisson and Leibniz dynamical systems. Second, this method is specifically adapted to Poisson systems obtained via a reduction procedure and we show in examples that the kind of stability that we propose is appropriate when dealing with the stability of the equilibria of some constrained mechanical systems. Finally, we discuss two situations in which the use of continuous Casimir functions in stability studies is equivalent to the topological stability methods introduced by Patrick et al. (Arch. Rational Mech. Anal., 2004, preprint arXiv:math.DS/0201239v1, to appear).

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Understanding which factors enhance or mitigate the impact of high temperatures on corals is crucial to predict the severity of coral bleaching worldwide. On the one hand, global warming is usually associated with high ultraviolet radiation levels (UVR), and surface water nutrient depletion due to stratification. On the other hand, eutrophication of coastal reefs increases levels of inorganic nutrients and decreases UVR, so that the effect of different combinations of these stressors on corals is unknown. In this study, we assessed the individual and crossed effects of high temperature, UVR and nutrient level on the key performance variables of the reef building coral Pocillopora damicornis. We found that seawater warming was the major stressor, which induced bleaching and impaired coral photosynthesis and calcification in all nutrient and UVR conditions. The strength of this effect however, was nutrient dependent. Corals maintained in nutrient-depleted conditions experienced the highest decrease in net photosynthesis under thermal stress, while nutrient enrichment (3 μM NO3- and 1 μM PO4+) slightly limited the negative impact of temperature through enhanced protein content, photosynthesis and respiration rates. UVR exposure had only an effect on total nitrogen release rates, which significantly decreased under normal growth conditions and tended to decrease also under thermal stress. This result suggests that increased level of UVR will lead to significant changes in the nutrient biogeochemistry of surface reef waters. Overall, our results show that environmental factors have different and interactive effects on each of the coral’s physiological parameters, requiring multifactorial approaches to predict the future of coral reefs.