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Toupoint N.,University of Quebec at Rimouski | Mohit V.,Laval University | Linossier I.,University of Southern Brittany | Bourgougnon N.,University of Southern Brittany | And 4 more authors.
Biofouling | Year: 2012

Biofilm ageing is commonly assumed to improve mussel settlement on artificial substrata, but the structure and taxonomic composition of biofilms remains unclear. In the present study, multi-species biofilms were characterized at different ages (1, 2, and 3 weeks) and their influence on settlement of the blue mussel, Mytilus edulis, was tested in the field. As biofilms can constitute a consistent food resource for larvae, the lipid quality, defined as the proportion of related essential fatty acids, may be a selection criterion for settlement. Overall mussel settlement increased on biofilms older than 1 week, and the enhanced settlement corresponded to the abundance and composition of the biofilm community, rather than to essential fatty acid levels. However, during a pulse of phytoplankton, the positive influence of biofilm was not detected, suggesting that pelagic cues overwhelmed those associated with biofilms. The influence of biofilms on mussel settlement could be more crucial when planktonic resources are limited. © 2012 Copyright Taylor and Francis Group, LLC. Source

Martel A.L.,Canadian Museum of Nature | Tremblay R.,University of Quebec at Rimouski | Toupoint N.,University of Quebec at Rimouski | Olivier F.,University of Quebec at Rimouski | And 2 more authors.
Journal of Shellfish Research | Year: 2014

Examination of the larval shell (prodissoconch) of molluscs with planktotrophic development can provide valuable information on their planktonic and early benthic life. We examined temporal variability of abundance and size among 11,994 veligers of the blue mussel (Mytilus edulis) in a coastal lagoon during settling periods between 1995 and 2009. Size and date at metamorphosis during the recruitment season were determined for 1,925 postlarvae (shell length, 255-900 μm) with prodissoconch II (PII) measurements. Emphasizing the recurrence of metamorphosis delay in the field, our study reveals a net increase in mean size at metamorphosis through time, with means for PII size ranging from 255-288 μm early in summer (after peak spawning events) to 400-422 μm (PII) during late July to early September. By estimating the "true" settlement date using the amount of dissoconch secreted after metamorphosis, such time-series analyses appropriately recapitulated the temporal pattern of mean pediveliger (competent larvae) size in the plankton. Our results demonstrate that greater settlement success rates were related to small size at metamorphosis-in particular, less than 320 μm. Seasonal increase in mean PII size occurring during the latter part of the settling period may be explained by competent veligers remaining adrift and delayed metamorphosis as a result of the lack of favorable encounters with a suitable substrate or the absence of specific trophic signals, or cues, required for stimulating settlement, thus forcing larvae to continue planktonic growth. The difference between the smallest and largest means for PII size corresponds to 122 μm of larval shell growth, or 47.8%, potentially representing a 322% difference in larval body mass at settlement. Source

Moreau S.,Catholic University of Louvain | Moreau S.,University of Quebec at Rimouski | Mostajir B.,Montpellier University | Almandoz G.O.,CONICET | And 14 more authors.
Aquatic Microbial Ecology | Year: 2014

Marine planktonic communities can be affected by increased temperatures associated with global climate change, as well as by increased ultraviolet B radiation (UVBR, 280-320 nm) through stratospheric ozone layer thinning. We studied individual and combined effects of increased temperature and UVBR on the plankton community of the Beagle Channel, southern Patagonia, Argentina. Eight 2 m3 mesocosms were exposed to 4 treatments (with 2 replicates) during 10 d: (1) control (natural temperature and UVBR), (2) increased UVBR (simulating a 60% decrease in stratospheric ozone layer thickness), (3) increased temperature (+ 3 °C), and (4) simultaneous increased temperature and UVBR (60% decrease in stratospheric ozone; + 3 °C). Two distinct situations were observed with regard to phytoplankton biomass: bloom (Days 1-4) and postbloom (Days 5-9). Significant decreases in micro-sized diatoms (>20 μm), bacteria, chlorophyll a, and particulate organic carbon concentrations were observed during the post-bloom in the enhanced temperature treatments relative to natural temperature, accompanied by significant increases in nanophytoplankton (10-20 μm, mainly prymnesiophytes). The decrease in microsized diatoms in the high temperature treatment may have been caused by a physiological effect of warming, although we do not have activity measurements to support this hypothesis. Prymnesiophytes benefited from micro-sized diatom reduction in their competition for resources. The bacterial decrease under warming may have been due to a change in the dissolved organic matter release caused by the observed change in phytoplankton composition. Overall, the rise in temperature affected the structure and total biomass of the communities, while no major effect of UVBR was observed on the plankton community. © Inter-Research 2014. Source

Toupoint N.,University of Quebec at Rimouski | Gilmore-Solomon L.,University of Quebec at Rimouski | Bourque F.,Center Maricole Des Iles Of La Madeleine Cemim | Bourque F.,Center Dinnovation Of Laquaculture Et Des Peches Du Quebec | And 6 more authors.
Ecology | Year: 2012

We considered Cushing's match/mismatch theory in a heterotrophic environment and hypothesized that settlement and recruitment success in blue mussel are higher when the food supply is rich in polyunsaturated and essential fatty acids (PUFA/EFA). To test this hypothesis, we monitored larval development as well as fatty acid composition in trophic resources during two successive reproductive seasons. The decoupling we found between the presence of competent larvae in the water column and settlement rates strongly suggests that metamorphosis is delayed until conditions are suitable. In both years, the major mussel settlement peak was synchronized with a phytoplanktonic pulse rich in EFA, consisting of a large autotrophic bloom in 2007 and a short but substantial peak of picoeukaryotes in 2008. These results suggest a "trophic settlement trigger" that indirectly affects recruitment by strongly improving the settlement rate. Despite similar larval settlement rates during both years, the lower 2007 recruitment likely resulted from a mismatch with a high lipid-quality trophic resource. The seasonal trophic conditions differed greatly between the two years, with fatty acids profiles reflecting heterotrophic plankton production in 2007 and mostly autotrophic production in 2008. In agreement with Cushing's theory, our results highlight a match/mismatch, related to the food lipid quality rather than food quantity. For the first time, we show that the recruitment in marine bivalves may be dependent on phytoplanktonic pulses characterized by high levels of PUFA. © 2012 by the Ecological Society of America. Source

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