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Eckbo, N., Le Bohec, C., Planas-Bielsa, V., Warner, N. A., Schull, Q., Herzke, D., et al. (2019). Individual variability in contaminants and physiological status in a resident Arctic seabird species. Environ. Pollut., 249, 191–199.
Résumé: While migratory seabirds dominate ecotoxicological studies within the Arctic, there is limited knowledge about exposure and potential effects from circulating legacy and emerging contaminants in species who reside in the high-Arctic all year round. Here, we focus on the case of the Mandt's Black guillemot (Cepphus grylle mandril) breeding at Kongsfjorden, Svalbard (79.00 degrees N, 11.66 degrees E) and investigate exposure to legacy and emerging contaminants in relation to individual physiological status, i.e. body condition, oxidative stress and relative telomere length. Despite its benthic-inshore foraging strategy, the Black guillemot displayed overall similar contaminant concentrations in blood during incubation (Sigma PCB11(15.7 ng/g w.w.) > Sigma PFAS(5) (9.9 ng/g w.w.)> Sigma Pesticides(9) (6.7 ng/g w.w.) > Sigma PBDE4 (2.7 ng/g w.w.), and Hg (0.3 mu g/g d.w.) compared to an Arctic migratory seabird in which several contaminant-related stress responses have been observed. Black guillemots in poorer condition tended to display higher levels of contaminants, higher levels of reactive oxygen metabolites, lower plasmatic antioxidant capacity, and shorter telomere lengths; however the low sample size restrict any strong conclusions. Nevertheless, our data suggests that nonlinear relationships with a threshold may exist between accumulated contaminant concentrations and physiological status of the birds. These findings were used to build a hypothesis to be applied in future modelling for describing how chronic exposure to contaminants may be linked to telomere dynamics. (C) 2019 Published by Elsevier Ltd.
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Ouisse, V., Marchand-Jouravleff, I., Fiandrino, A., Feunteun, E., & Ysnel, F. (2020). Swinging boat moorings: Spatial heterogeneous damage to eelgrass beds in a tidal ecosystem. Estuarine, Coastal and Shelf Science, 235, 106581.
Résumé: Seagrass meadows are currently known to be subjected to huge physical disturbances including boat moorings in shallow bays. We aimed to identify the impact of permanent swing mooring on the fast-growing seagrass Zostera marina in a mega-tidal area. Coupling the hydrodynamic MARS3D model to simulate mooring chain movements and in situ measurements of plant traits, we analyzed the structural responses of the eelgrass bed to scraping disturbance in the western English Channel (France). A comparison of the results with a reference site without any permanent swing boat mooring showed a significant impact on eelgrass structure (shoot density, leaf size, leaf dry weight), depending on the direction and distance from the mooring. Zostera marina was absent close to the mooring fixation point in three out of the four directions we evaluated. Beyond 5 m, the canopy height remained lower than in the reference site, most likely due to regular disturbances by mooring chains. Conversely, shoot density beyond 5 m was higher than in the reference site. This adaptive response counter-balanced the decrease in canopy height at these distances. The fluctuations of the structure of the eelgrass cover (number of shoots, leaf length) at a small spatial scale was clearly in accordance with the scraping intensity simulated by the MARS3D model. The tidal currents coupled to tidal amplitude variability imply a small-scale heterogeneous effect of permanent mooring on the benthic compartment, previously undetected by an aerial survey. The present results highlight the interest of coupling approaches so as to understand how physical pressure influences fast-growing species traits. The resulting important modifications could imply a more functional impact such as biodiversity loss and carbon sequestration, which is beyond the scope of the present paper.
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Soissons, L. M., da Conceicao, T. G., Bastiaan, J., van Dalen, J., Ysebaert, T., Herman, P. M. J., et al. (2019). Sandification vs. muddification of tidal flats by benthic organisms: A flume study. Estuar. Coast. Shelf Sci., 228, Unsp-106355.
Résumé: Bioturbating benthic organisms have typically been characterised by how they modify the vertical sediment erosion thresholds. By means of several annular flume experiments, we aimed to understand how benthic organisms may affect grain-size sediment properties over time, and how this depends on the sediment type and the sediment loading of the water column. We compared the effect of two bioturbating macroinvertebrate species: a local dominant species, the cockle Cerastoderma edule and a spreading non-indigeneous species, the clam Ruditapes philippinarum. Our results indicate that the effect of benthic organisms on sediment dynamics is strongly dependent on both the prevailing environmental conditions and the benthic species present. If sediment is sandy, the benthos can gradually enhance the silt content of the sediment by mixing in part of the daily tidal sediment deposition. In contrast, if sediment is muddy, benthos can gradually decrease the silt content of the sediment by specifically suspending the fine fraction. Moreover, we observed that the native cockles had a stronger impact than invasive clams. Therefore, bioturbating benthos can have an important effect in determining the local sediment properties, with the outcome depending both on the species in question and the environmental conditions the bioturbator lives in. Our findings show that sediment bioturbation may have strong implications for tidal flat stability undergoing major changes from natural or anthropogenic sources.
Mots-Clés: arenicola-marina; Benthic organisms; cerastoderma-edule bioturbation; Cerastorderma edule; community structure; erosion; impact; intertidal flat; lanice-conchilega; model; Ruditapes philippinarum; sediment erodability; Sediment properties; Silt content; Suspended sediment concentration; Tidal flats; wadden sea
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Santos, B. S., Friedrichs, M. A. M., Rose, S. A., Barco, S. G., & Kaplan, D. M. (2018). Likely locations of sea turtle stranding mortality using experimentally-calibrated, time and space-specific drift models. Biol. Conserv., 226, 127–143.
Résumé: Sea turtle stranding events provide an opportunity to study drivers of mortality, but causes of strandings are poorly understood. A general sea turtle carcass oceanographic drift model was developed to estimate likely mortality locations from coastal sea turtle stranding records. Key model advancements include realistic direct wind forcing on carcasses, temperature driven carcass decomposition and the development of mortality location predictions for individual strandings. We applied this model to 2009-2014 stranding events within the Chesapeake Bay, Virginia. Predicted origin of vessel strike strandings were compared to commercial vessel data, and potential hazardous turtle-vessel interactions were identified in the southeastern Bay and James River. Commercial fishing activity of gear types with known sea turtle interactions were compared to predicted mortality locations for stranded turtles with suggested fisheries-induced mortality. Probable mortality locations for these strandings varied seasonally, with two distinct areas in the southwest and southeast portions of the lower Bay. Spatial overlap was noted between potential mortality locations and gillnet, seine, pot, and pound net fisheries, providing important information for focusing future research on mitigating conflict between sea turtles and human activities. Our ability to quantitatively assess spatial and temporal overlap between sea turtle mortality and human uses of the habitat were hindered by the low resolution of human use datasets, especially those for recreational vessel and commercial fishing gear distributions. This study highlights the importance of addressing these data gaps and provides a meaningful conservation tool that can be applied to stranding data of sea turtles and other marine megafauna worldwide.
Mots-Clés: bycatch; chesapeake bay; Chesapeake Bay; Drift simulations; Endangered species; fisheries; Fisheries and vessel interactions; global patterns; hotspots; ichthyoplankton; manatees; Marine conservation; megafauna; Protected species management; Sea turtle mortality; Sea turtle strandings; vessel; virginia
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Blasco, F. R., Esbaugh, A. J., Killen, S. S., Rantin, F. T., Taylor, E. W., & McKenzie, D. J. (2020). Using aerobic exercise to evaluate sub-lethal tolerance of acute warming in fishes. J. Exp. Biol., 223(9), jeb218602.
Résumé: We investigated whether fatigue from sustained aerobic swimming provides a sub-lethal endpoint to define tolerance of acute warming in fishes, as an alternative to loss of equilibrium (LOE) during a critical thermal maximum (CTmax) protocol. Two species were studied, Nile tilapia (Oreochromis niloticus) and pacu (Piaractus mesopotamicus). Each fish underwent an incremental swim test to determine gait transition speed (U-GT), where it first engaged the unsteady anaerobic swimming mode that preceded fatigue. After suitable recovery, each fish was exercised at 85% of their own U-GT and warmed 1 degrees C every 30 min, to identify the temperature at which they fatigued, denoted as CTswim. Fish were also submitted to a standard CTmax, warming at the same rate as CTswim, under static conditions until LOE. All individuals fatigued in CTswim, at a mean temperature approximately 2 degrees C lower than their CTmax. Therefore, if exposed to acute warming in the wild, the ability to perform aerobic metabolic work would be constrained at temperatures significantly below those that directly threatened survival. The collapse in performance at CTswim was preceded by a gait transition qualitatively indistinguishable from that during the incremental swim test. This suggests that fatigue in CTswim was linked to an inability to meet the tissue oxygen demands of exercise plus warming. This is consistent with the oxygen and capacity limited thermal tolerance (OCLTT) hypothesis, regarding the mechanism underlying tolerance of warming in fishes. Overall, fatigue at CTswim provides an ecologically relevant sub-lethal threshold that is more sensitive to extreme events than LOE at CTmax.
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