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Garrido, M., Cecchi, P., Vaquer, A., & Pasqualini, V. (2013). Effects of sample conservation on assessments of the photosynthetic efficiency of phytoplankton using PAM fluorometry. Deep-Sea Res. Part I-Oceanogr. Res. Pap., 71, 38–48.
Résumé: Pulse Amplitude Modulated (PAM) fluorometry is now a widely used method for the assessment of phytoplankton fitness, with an increasing popularity in field assessments. It is usually recommended to carry out measurements swiftly after collection, but the number of samples and analytical procedures needed to obtain valuable datasets sometimes makes immediate analysis impracticable, forcing delays between fluorescence measurements. Conservation conditions of samples before analysis may potentially affect their photosynthetic performances but no formal study documenting such impacts appears available in the literature. The aim of this study was to investigate the effects of storage conditions (temperature, duration) on photosynthetic parameters in different phytoplankton communities (characterized in situ by a BBE fluoroprobe) sampled during summer in different environmental locations in a Mediterranean lagoon (Biguglia lagoon, Corsica, France). PAM-fluorescence parameters were measured after three different conservation durations (2-4 h, 6-8 h and 10-12 h after collection) on samples stored at three different temperatures (15 degrees C, 25 degrees C and 35 degrees C). Results showed that storage at the highest temperature severely impacted photosynthetic parameters, with cumulative effects as storage duration increased. For phytoplankton samples collected in warm or tropical environments, storage at “room temperature” (25 degrees C) only appeared a valid option if measurements have to be carried out strictly within a very short delay. Inversely, cooling the samples (i.e. conservation at 15 degrees C) did not induce significant effects, independently of storage duration. Cooling appeared the best solution when sampling-to-analysis delay goes over a few hours. Long-term storage ( > 8 h) should definitively be avoided. (C) 2012 Elsevier Ltd. All rights reserved.
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Geffard, O., Xuereb, B., Chaumot, A., Geffard, A., Biagianti, S., Noel, C., et al. (2010). Ovarian cycle and embryonic development in gammarus fossarum: Application for reproductive toxicity assessment. Environ. Toxicol. Chem., 29(10), 2249–2259.
Résumé: Among freshwater invertebrates, Gammarus fossarum is an important test organism and is currently used in ecotoxicology for acute and chronic assays; nevertheless, reproductive toxicity test methods are not yet available for these species. In the present study, the reproductive cycle in Gammarus fossarum was characterized in order to propose a reproductive toxicity test encompassing molting, follicle growth, and embryonic development that will provide a better understanding of the mode of action of chemicals disrupting these hormone-regulated processes. A detailed description of the reproductive cycle in Gammarus fossarum was obtained. As in some amphipods, molt and reproductive cycles of G. fossarum females occur concurrently, lasting 30 d at 12 C. Each molt stage is characterized by a specific marsupial embryonic development stage and the size of developing follicles visible on the ovarian membrane. Based on these results, a 21 -d reproductive toxicity test is proposed for this species. This new bioassay was applied to identify the specific impact of different stressors: cadmium, methomyl, nonylphenol, and a starvation diet. Good reproducibility was obtained for different endpoints under control conditions and throughout the experiments. Preliminary robust reference values or benchmarks were proposed for these endpoints. Cadmium was found to specially inhibit secondary vitellogenesis. Nonylphenol had a specific concentration-dependent effect on embryonic development, with an increase in the percent abnormality from a concentration of 0.05 mu g/L. A restricted food diet led to a significant delay in the molt cycle, which in turn induced inhibition of secondary vitellogenesis. Environ Toxicol. Chem. 2010;29:2249-2259. (C) 2010 SETAC
Mots-Clés: Endocrine disruption; Gammarus fossarum; Molt cycle; Reproductive cycle; Reproductive toxicity; acetylcholinesterase activity; amphipod monoporeia-affinis; aquatic environment; behavioral-responses; crustacea-amphipoda; estuarine sediments; melita-plumulosa zeidler; multilevel assessment; pulex crustacea; test
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Goetze, J., Langlois, T., Claudet, J., Januchowski-Hartley, F., & Jupiter, S. D. (2016). Periodically harvested closures require full protection of vulnerable species and longer closure periods. Biol. Conserv., 203, 67–74.
Résumé: Periodically harvested closures (PHCs) are small fisheries closures with objectives such as sustaining fisheries and conserving biodiversity and have become one of the most common forms of nearshore marine management in the Western Pacific. Although PHCs can provide both short-term conservation and fisheries benefits, their potential as a long-term management strategy remains unclear. Through empirical assessment of a single harvest event in each of five PHCs, we determined whether targeted fishes that differ in their vulnerability to fishing recovered to pre-harvest conditions (the state prior to last harvest) and demonstrated post-harvest recovery benefits after 1 year of re-closure. For low and moderately vulnerable species, two PHCs provided significant pre-harvest benefits and one provided significant post-harvest recovery benefits, suggesting a contribution to longer-term sustainability. PHCs with a combination of high compliance and longer closing times are more likely to provide fisheries benefits and recover from harvest events, however, no benefits were observed across any PHCs for highly vulnerable species. We recommend PHCs have longer closure periods before being harvested and species that are highly vulnerable to fishing (e.g. large species of; grouper, wrasse and parrotfish) are avoided during harvests to avoid overexploitation and increase the sustainability of small-scale fisheries. (C) 2016 Elsevier Ltd. All rights reserved.
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Iversen, N. K., McKenzie, D. J., Malte, H., & Wang, T. (2010). Reflex bradycardia does not influence oxygen consumption during hypoxia in the European eel (Anguilla anguilla). J. Comp. Physiol. B-Biochem. Syst. Environ. Physiol., 180(4), 495–502.
Résumé: Most teleost fish reduce heart rate when exposed to acute hypoxia. This hypoxic bradycardia has been characterised for many fish species, but it remains uncertain whether this reflex contributes to the maintenance of oxygen uptake in hypoxia. Here we describe the effects of inhibiting the bradycardia on oxygen consumption (MO(2)), standard metabolic rate (SMR) and the critical oxygen partial pressure for regulation of SMR in hypoxia (Pcrit) in European eels Anguilla anguilla (mean +/- A SEM mass 528 +/- A 36 g; n = 14). Eels were instrumented with a Transonic flow probe around the ventral aorta to measure cardiac output (Q) and heart rate (f (H)). MO(2) was then measured by intermittent closed respirometry during sequential exposure to various levels of increasing hypoxia, to determine Pcrit. Each fish was studied before and after abolition of reflex bradycardia by intraperitoneal injection of the muscarinic antagonist atropine (5 mg kg(-1)). In the untreated eels, f (H) fell from 39.0 +/- A 4.3 min(-1) in normoxia to 14.8 +/- A 5.2 min(-1) at the deepest level of hypoxia (2 kPa), and this was associated with a decline in Q, from 7.5 +/- A 0.8 mL min(-1) kg(-1) to 3.3 +/- A 0.7 mL min(-1) kg(-1) in normoxia versus deepest hypoxia, respectively. Atropine had no effect on SMR, which was 16.0 +/- A 1.8 mu mol O(2) kg(-1) min(-1) in control versus 16.8 +/- A 0.8 mu mol O(2) kg(-1) min(-1) following treatment with atropine. Atropine also had no significant effect on normoxic f (H) or Q in the eel, but completely abolished the bradycardia and associated decline in Q during progressive hypoxia. This pharmacological inhibition of the cardiac responses to hypoxia was, however, without affect on Pcrit, which was 11.7 +/- A 1.3 versus 12.5 +/- A 1.5 kPa in control versus atropinised eels, respectively. These results indicate, therefore, that reflex bradycardia does not contribute to maintenance of MO(2) and regulation of SMR by the European eel in hypoxia.
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Kadowaki, K., Barbera, C. G., Godsoe, W., Delsuc, F., & Mouquet, N. (2016). Predicting biotic interactions and their variability in a changing environment. Biol. Lett., 12(5), 20151073.
Résumé: Global environmental change is altering the patterns of biodiversity worldwide. Observation and theory suggest that species' distributions and abundances depend on a suite of processes, notably abiotic filtering and biotic interactions, both of which are constrained by species' phylogenetic history. Models predicting species distribution have historically mostly considered abiotic filtering and are only starting to integrate biotic interaction. However, using information on present interactions to forecast the future of biodiversity supposes that biotic interactions will not change when species are confronted with new environments. Using bacterial microcosms, we illustrate how biotic interactions can vary along an environmental gradient and how this variability can depend on the phylogenetic distance between interacting species.
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