Coral Uptake of Inorganic Phosphorus and Nitrogen Negatively Affected by Simultaneous Changes in Temperature and pH

The effects of ocean acidification and elevated seawater temperature on coral calcification and photosynthesis have been extensively investigated over the last two decades, whereas they are still unknown on nutrient uptake, despite their importance for coral energetics. We therefore studied the separate and combined impacts of increases in temperature and pCO2 on phosphate, ammonium, and nitrate uptake rates by the scleractinian coral S. pistillata. Three experiments were performed, during 10 days i) at three pHT conditions (8.1, 7.8, and 7.5) and normal temperature (26°C), ii) at three temperature conditions (26°, 29°C, and 33°C) and normal pHT (8.1), and iii) at three pHT conditions (8.1, 7.8, and 7.5) and elevated temperature (33°C). After 10 days of incubation, corals had not bleached, as protein, chlorophyll, and zooxanthellae contents were the same in all treatments. However, photosynthetic rates significantly decreased at 33°C, and were further reduced for the pHT 7.5. The photosynthetic efficiency of PSII was only decreased by elevated temperature. Nutrient uptake rates were not affected by a change in pH alone. Conversely, elevated temperature (33°C) alone induced an increase in phosphate uptake but a severe decrease in nitrate and ammonium uptake rates, even leading to a release of nitrogen into seawater. Combination of high temperature (33°C) and low pHT (7.5) resulted in a significant decrease in phosphate and nitrate uptake rates compared to control corals (26°C, pHT = 8.1). These results indicate that both inorganic nitrogen and phosphorus metabolism may be negatively affected by the cumulative effects of ocean warming and acidification

Sea Snake research in New Caledonia

International audienceNew Caledonia hosts about fourteen species of sea snakes. They belong to both of the marine Elapidaelineages: laticaudinae or sea kraits, which are oviparous and amphibious, and hydrophiinae or true seasnakes, which are viviparous and fully marine. Some populations of these sea snakes species areexceptionally easy to access for researchers, as they inhabit shallow coastal waters near urbanized areas.However, they did not attract much interest from scientists before the twenty-first century. Less than 20scientific articles about New Caledonian sea snakes were published before 2000, some of them onlymaking a brief account of species presence. Sea snake research greatly increased in New Caledonia duringtwenty-first century, as more than 55 articles containing data about New Caledonia sea snakes werepublished to date. Professor Rick Shine is one of the major initiators of this increase, since he authored orco-authored at least 35 of these papers. These studies cover different aspects of sea snake ecology andevolution. This presentation aims to highlight some of the findings of his research about sea snakes inNew Caledonia

The ability of damselfish to distinguish between dangerous and harmless sea snakes

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Peaceful coexistence between people and deadly wildlife: Why are recreational users of the ocean so rarely bitten by sea snakes?

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Niche partitioning within a population of sea snakes is constrained by ambient thermal homogeneity and small prey size

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Industrial Melanism in the Seasnake Emydocephalus annulatus

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Frequency-dependent Batesian mimicry maintains colour polymorphism in a sea snake population

International audienceAbstract Evolutionary theory suggests that polymorphic traits can be maintained within a single population only under specific conditions, such as negative frequency-dependent selection or heterozygote advantage. Non-venomous turtle-headed sea snakes ( Emydocephalus annulatus ) living in shallow bays near Noumea in New Caledonia exhibit three colour morphs: black, black-and-white banded, and an intermediate (grey-banded) morph that darkens with age. We recorded morph frequencies during 18 consecutive years of surveys, and found that the numbers of recruits (neonates plus immigrants) belonging to each morph increased in years when that morph was unusually rare in the population, and decreased when that morph was unusually common. Thus, morph frequencies are maintained by negative frequency-dependent selection. We interpret the situation as Batesian mimicry of highly venomous sea snakes ( Aipysurus, Hydrophis, Laticauda ) that occur in the same bays, and range in colour from black-and-white banded to grey-banded. Consistent with the idea that mimicry may protect snakes from attack by large fish and sea eagles, behavioural studies have shown that smaller fish species in these bays flee from banded snakes but attack black individuals. As predicted by theory, mimetic (banded) morphs are less common than the cryptically-coloured melanic morph

The behaviour of sea snakes (Emydocephalus annulatus) shifts with the tides

Abstract Tidal cycles are known to affect the ecology of many marine animals, but logistical obstacles have discouraged behavioural studies on sea snakes in the wild. Here, we analyse a large dataset (1,445 observations of 126 individuals) to explore tidally-driven shifts in the behaviour of free-ranging turtle-headed sea snakes (Emydocephalus annulatus, Hydrophiinae) in the Baie des Citrons, New Caledonia. Snakes tended to move into newly-inundated areas with the rising tide, and became more active (e.g. switched from inactivity to mate-searching and courting) as water levels rose. However, the relative use of alternative habitat types was largely unaffected by tidal phase