Abstract
Polar regions are currently warming at a rate above the global average. One issue of concern is the consequences on biodiversity in relation to the Northward latitudinal shift in distribution of temperate species. In the present study, lasting almost two years, we examined two phenological traits, i.e. the shell growth and behavioural rhythm of a recently re-established species in the high Arctic, the blue mussel Mytilus sp. We compared this with a native species, the Islandic scallop Chlamys islandica. We show marked differences in the examined traits between the two species. In Mytilus sp., a clear annual pattern of shell growth strongly correlated to the valve behaviour rhythmicity, whereas C. islandica exhibited a shell growth pattern with a total absence of annual rhythmicity of behaviour. The shell growth was highly correlated to the photoperiod for the mussels but weaker for the scallops. The water temperature cycle was a very weak parameter to anticipate the phenology traits of both species. This study shows that the new resident in the high Arctic, Mytilus sp., is a highly adaptive species, and therefore a promising bioindicator to study the consequences of biodiversity changes due to global warming.
Highlights
Arctic ecosystems undergo drastic climatic variability in terms of light, temperature and food availability on several scales, from daily changes to seasonal and annual ones
The northward expansion of organisms at high latitudes raises the question of their phenotypic adaptation and the plasticity of their physiological mechanisms to extreme photoperiods [3,4]
A re-emerged resident in the high Arctic, have a distribution range limited mainly by winter air temperatures and are good candidates to study the adaptations of species undergoing a poleward expansion, informing on the consequences of climate change upon biodiversity [7,8,9]
Summary
Arctic ecosystems undergo drastic climatic variability in terms of light, temperature and food availability on several scales, from daily changes to seasonal and annual ones. A re-emerged resident in the high Arctic, have a distribution range limited mainly by winter air temperatures and are good candidates to study the adaptations of species undergoing a poleward expansion, informing on the consequences of climate change upon biodiversity [7,8,9]. We analysed the seasonal timing (i.e. the phenology) of two biological processes that are the behaviour and the shell growth of the blue mussel Mytilus sp., a species which recently resettled in the Svalbard archipelago after a 1000-year absence. We present the first analysis, at an annual scale, of the valve behaviour jointly to the shell growth pattern of the mussel in the high Arctic. We highlighted differences and shared phenological traits studied in both bivalve species (native versus resettled)
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