Metabolic rate determines the physiological and life-history performances of ectotherms. Thus, the extent to which such rates are sensitive and plastic to environmental perturbation is central to an organism's ability to function in a changing environment. Little is known of long-term metabolic plasticity and potential for metabolic adaptation in marine ectotherms exposed to elevated p CO 2 . Consequently, we carried out a series of in situ transplant experiments using a number of tolerant and sensitive polychaete species living around a natural CO 2 vent system. Here, we show that a marine metazoan (i.e. Platynereis dumerilii ) was able to adapt to chronic and elevated levels of p CO 2 . The vent population of P. dumerilii was physiologically and genetically different from nearby populations that experience low p CO 2 , as well as smaller in body size. By contrast, different populations of Amphiglena mediterranea showed marked physiological plasticity indicating that adaptation or acclimatization are both viable strategies for the successful colonization of elevated p CO 2 environments. In addition, sensitive species showed either a reduced or increased metabolism when exposed acutely to elevated p CO 2 . Our findings may help explain, from a metabolic perspective, the occurrence of past mass extinction, as well as shed light on alternative pathways of resilience in species facing ongoing ocean acidification.

Nereidid worms are well known to be key prey species for aquatic organisms, including economically important fish (e.g. plaice) and invertebrates (shrimps). Food regimes which include nereidids improve the reproductive fitness of cultured animals, i.e. the 'nereidid effect'. Aquaculture produces huge amounts of sludge, which might be recycled by feeding to the ragworm Nereis diversicolor. Here we analysed the fatty acid profiles in N. diversicolor over 1 yr for a wild population and for ragworms fed with commercial fish food or eel sludge. The omega-3 (ω-3) eicosapentanoic acid (20:5n3) was the most abundant fatty acid followed by palmitic (16:0), stearic (18:0) and oleic (18:1) acids. Biomass of the ragworms increased by 205% in worms fed with fish food and remained stable in worms fed with eel sludge, indicating the good adaptation of individuals to the culture conditions. Only under fish food regimes were significant increases observed in saturated and total unsaturated fatty acids compared to natural food regimes. However, the ω-3 polyunsaturated fatty acids did not differ among food regimes, indicating that sludge from aquaculture is a good nutritive resource for N. diversicolor. This suggests the potential use of ragworms in aquaculture to reduce the production of waste and increase the reproductive fitness of cultivated animals.

There is an increasing demand for easy and cost-effective methods to screen the toxicological impact of the growing number of chemical mixtures being generated by industry. Such a screening method has been developed using viable, genetically modified green fluorescent protein (GFP) reporter yeast that was magnetically functionalised and held within a microfluidic device. The GFP reporter yeast was used to detect genotoxicity by monitoring the exposure of the cells to a well-known genotoxic chemical (methyl methane sulfonate, MMS). The cells were magnetised using biocompatible positively charged PAH-stabilised magnetic nanoparticles with diameters around 15 nm. Gradient mixing was utilised to simultaneously expose yeast to a range of concentrations of toxins, and the effective fluorescence emitted from the produced GFP was measured. The magnetically enhanced retention of the yeast cells, with their facile subsequent removal and reloading, allowed for very convenient and rapid toxicity screening of a wide range of chemicals. This is the first report showing magnetic yeast within microfluidic devices in a simple bioassay, with potential applications to other types of fluorescent reporter yeast in toxicological and biomedical research. The microfluidic chip offers a simple and low-cost screening test that can be automated to allow multiple uses (adapted to different cell types) of the device on a wide range of chemicals and concentrations.

Olfactory sensitivity to bile salts is wide-spread in teleosts; however, which bile salts are released in suYcient quantities to be detected is unclear. The current study identiWed bile salts in the intestinal and bile Xuids of Solea senegalensis by mass spectrometry-liquid chromatography and assessed their olfactory potency by the electro-olfactogram. The main bile salts identiWed in the bile were taurocholic acid (342 mM) and taurolithocholic acid (271 mM) plus a third, unidentiWed, bile salt of 532.3 Da. These three were also present in the intestinal Xuid (taurocholic acid, 4.13 mM; taurolithocholic acid, 0.4 mM). In sole-conditioned water, only taurocholic acid (0.31 M) was released in suYcient quantities to be measured (release rate: 24 nmol kg ¡1 min ¡1). Sole had high olfactory sensitivity to taurocholic acid but not to taurolithocholic acid. Furthermore, olfactory sensitivity was higher in the upper (right) olfactory epithelium than the lower (left). These two bile acids contribute about 40% of the olfactory potency of intestinal Xuid and account for the diVerence in potency at the two epithelia. Taurocholic acid (but not taurolithocholic acid), and possibly other types of bile acid not tested, could be used as chemical signals and the upper olfactory epithelium is specialised for their detection.

Increasing atmospheric levels of carbon dioxide are largely absorbed by the world's oceans, decreasing surface water pH 1 . In combination with increasing ocean temperatures, these changes have been identified as a major sustainability threat to future marine life 2 . Interactions between marine organisms are known to depend on biomolecules, but the influence of oceanic pH on their bioavailability and functionality remains unexplored. Here we show that global change significantly impacts two ecological keystone molecules 3 in the ocean, the paralytic toxins saxitoxin (STX) and tetrodotoxin (TTX). Increasing temperatures and declining pH increase the abundance of the toxic forms of these two neurotoxins in the water. Our geospatial global model highlights where this increased toxicity could intensify the devastating impact of harmful algal blooms on ecosystems in the future, for example through an increased incidence of paralytic shellfish poisoning (PSP). We also use these results to calculate future saxitoxin toxicity levels in Alaskan clams, Saxidomus gigantea, showing critical exceedance of limits safe for consumption. Our findings for TTX and STX exemplify potential consequences of changing pH and temperature on chemicals dissolved in the sea. This reveals major implications not only for ecotoxicology, but also for chemical signals mediating species interactions such as foraging, reproduction, or predation in the ocean with unexplored consequences for ecosystem stability and ecosystem services.