The recent appearance and invasion of feral oysters (Crassostrea gigas) along the northern European Atlantic coast, underscores the necessity to investigate the relationship between environmental variables, reproductive physiology, larval development and recruitment. We studied these relationships at both high (HT) and intermediate (IT) – turbidity sites, through historical data on water temperatures, multi-parameter environmental probes, histological analyses, and field collections of planktonic larvae and settled post-larvae in 2005 and 2006. A progressive warming trend was observed, especially since 1995, when oyster proliferation first became severe. Threshold temperatures for oocyte growth, larval development and settlement were achieved in both 2005 and 2006. The HT site showed greater numbers of larvae and post-larvae than the IT site for both years, with the highest numbers of post-larvae observed at both sites during the warmer summer of 2006. These results suggest that increased temperatures in northern European waters allow successful reproduction, larval development, and recruitment of C. gigas. High turbidity conditions further enhance this success.
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"The expansion of wild settlement in Europe can be observed through the formation of dense reefs, which drastically change the physical characteristics of both soft and hard substrates (Lejart & Hily, 2011). Several field studies have reported a correlation between this expansion and the increase in seawater temperature, mainly since 1995, related to better reproduction, larval development and recruitment rates (Diederich et al., 2005; Schmidt et al., 2008; Dutertre et al., 2010). The increase in water temperature expected in the 21st century (IPCC, 2007) may exacerbate the expansion of C. gigas along NW European coasts and, on a greater scale, along the latitudinal range of its current world-wide biogeographical distribution (Carrasco & Bar on, 2010), but multiple vectors of transport between water bodies (e.g. "
[Show abstract][Hide abstract] ABSTRACT: Aim: The spread of non-indigenous species in marine ecosystems world-wide is one of today's most serious environmental concerns. Using mechanistic modelling, we investigated how global change relates to the invasion of European coasts by a non-native marine invertebrate, the Pacific oyster Crassostrea gigas. Location: Bourgneuf Bay on the French Atlantic coast was considered as the northern boundary of C. gigas expansion at the time of its introduction to Europe in the 1970s. From this latitudinal reference, variations in the spatial distribution of the C. gigas reproductive niche were analysed along the north-western European coast from Gibraltar to Norway. Methods: The effects of environmental variations on C. gigas physiology and phenology were studied using a bioenergetics model based on Dynamic Energy Budget theory. The model was forced with environmental time series including in situ phytoplankton data, and satellite data of sea surface temperature and suspended particulate matter concentration. Results: Simulation outputs were successfully validated against in situ oyster growth data. In Bourgneuf Bay, the rise in seawater temperature and phytoplankton concentration has increased C. gigas reproductive effort and led to precocious spawning periods since the 1960s. At the European scale, seawater temperature increase caused a drastic northward shift (1400 km within 30 years) in the C. gigas reproductive niche and optimal thermal conditions for early life stage development. Main conclusions: We demonstrated that the poleward expansion of the invasive species C. gigas is related to global warming and increase in phytoplankton abundance. The combination of mechanistic bioenergetics modelling with in situ and satellite environmental data is a valuable framework for ecosystem studies. It offers a generic approach to analyse historical geographical shifts and to predict the biogeographical changes expected to occur in a climate-changing world.
Full-text · Article · Nov 2015 · Journal of Biogeography
"However, early life stages are generally more vulnerable (de Rivera et al. 2007). For example, suboptimal temperatures were found to negatively affect spawning, larval development, spatfall and subsequent juvenile survival in Crassostrea gigas, and this has led to the recruitment failure in some regions (Spencer et al. 1994; Child and Laing 1998; Diederich et al. 2005; Dutertre et al. 2010). Conditions, however, need to be suitable for all life cycle stages so that recruitment, and hence spread of the species into a new environment, can be successful. "
[Show abstract][Hide abstract] ABSTRACT: The establishment and spread of a non-native species in an introduced range depends to a large extent on the performance of the species under the prevailing environmental conditions. The spawning, larval and spatfall periods of the invasive gastropod Crepidula fornicata were monitored in the intertidal zone at its northernmost range in Wales, UK, between February 2010 and January 2011. The duration of the reproductive season was similar to that recorded from more southerly European populations. Spawning and larval release occurred throughout most of the year even at low seawater temperatures of <7 °C, but benthic recruitment was observed over a much shorter period at seawater temperatures >16 °C. Recruitment was low and likely controlled by post-settlement mortality. These observations suggest that C. fornicata’s northwards spread in Welsh waters will not be limited by seawater temperature negatively affecting reproduction, but by processes acting after larval release. These data show the importance of incorporating settlement and post-settlement processes into studies on recruitment success when aiming to predict the potential spread of a potentially harmful invader such as C. fornicata.
"C.J.M. Philippart et al. / Estuarine, Coastal and Shelf Science xxx (2012) 1e12 8 Please cite this article in press as: Philippart, C.J.M., et al., Spatial synchronies in the seasonal occurrence of larvae of oysters (Crassostrea gigas) and mussels (Mytilus edulis/galloprovincialis) in European coastal waters, Estuarine, Coastal and Shelf Science (2012), doi:10.1016/ j.ecss.2012.05.014 (Pouvreau et al., 2006; Cardoso et al., 2007; Enríquez-Díaz et al., 2009; Troost et al., 2009; Dutertre et al., 2010). The second best but comparably good model (Fig. 4) suggested that larvae exhibit one seasonal trend and one underlying latitudinal effect in probability of occurrence, while the third best model (Fig. 5) suggested that oyster larvae also occurred earlier at higher latitudes in the range of those tested. "
[Show abstract][Hide abstract] ABSTRACT: Reproductive cycles of marine invertebrates with complex life histories are considered to be synchronized by water temperature and feeding conditions, which vary with season and latitude. This study analyses seasonal variation in the occurrence of oyster (Crassostrea gigas) and mussel (Mytilus edulis/ galloprovincialis) larvae across European coastal waters at a synoptic scale (1000s of km) using standardised methods for sampling and molecular analyses.
We tested a series of hypotheses to explain the observed seasonal patterns of occurrence of bivalve larvae at 12 European stations (located between 37� N and 60� N and 27� W and 18� E). These hypotheses included a model that stated that there was no synchronisation in seasonality of larval presence at all between the locations (null hypothesis), a model that assumed that there was one common seasonality pattern for all stations within Europe, and various models that supposed that the variation in seasonality could be grouped according to speciﬁc spatial scales (i.e., latitude, large marine ecosystems and ecoregions), taxonomic groups, or several combinations of these factors.
For oysters, the best models explaining the presence/absence of larvae in European coastal waters were (1) the model that assumed one common seasonal pattern, and (2) the one that, in addition to this common pattern, assumed an enhanced probability of occurrence from south to north. The third best model for oysters, with less empirical support than the ﬁrst two, stated that oysters reproduced later in the south than in the north. For mussels, the best models explaining the seasonality in occurrence of larvae were (1) the model that assumed four underlying trends related to large marine ecosystems, and (2) the one that assumed one common seasonal pattern for larvae occurrence throughout Europe. Such synchronies in larval occurrences suggest that environmental conditions relevant to bivalve larval survival are more or less similar at large spatial scales from 100s to 1000s of km. To unravel the underlying mechanisms for this synchronisation is of particular interest in the light of changing environmental conditions as the result of global climate change and the possible consequences for marine food webs and ecosystem services.
Full-text · Article · Aug 2012 · Estuarine Coastal and Shelf Science