Vertical distribution of brittle star larvae in two contrasting coastal embayments: implications for larval transport
|Author(s)||Guillam Morgane1, Bessin Claire1, Blanchet-Aurigny Aline2, Cugier Philippe2, Nicolle Amandine1, 3, Thiébaut Éric1, Comtet Thierry1|
|Affiliation(s)||1 : Sorbonne Université, CNRS, Station Biologique de Roscoff, Laboratoire Adaptation Et Diversité en Milieu Marin, ADMM, CS90074, 29688, Roscoff Cedex, France
2 : Ifremer, Centre de Bretagne, Département Dynamiques des Ecosystèmes Côtiers (DYNECO), Laboratoire d’Ecologie Benthique Côtière (LEBCO), Technopole Brest Iroise, CS 10070, 29280, Plouzané, France
3 : ENSTA Bretagne, Pôle STIC/OSM, 2 rue François Verny, 29806, Brest Cedex 9, France
|Source||Scientific Reports (2045-2322) (Springer Science and Business Media LLC), 2020-07 , Vol. 10 , N. 1 , P. 12033 (15p.)|
The ability of marine invertebrate larvae to control their vertical position shapes their dispersal pattern. In species characterized by large variations in population density, like many echinoderm species, larval dispersal may contribute to outbreak and die-off phenomena. A proliferation of the ophiuroid Ophiocomina nigra was observed for several years in western Brittany (France), inducing drastic changes on the benthic communities. We here studied the larval vertical distribution in this species and two co-occurring ophiuroid species, Ophiothrix fragilis and Amphiura filiformis, in two contrasting hydrodynamic environments: stratified in the bay of Douarnenez and well-mixed in the bay of Brest. Larvae were collected at 3 depths during 25 h within each bay. In the bay of Brest, all larvae were evenly distributed in the water column due to the intense vertical mixing. Conversely, in the bay of Douarnenez, a diel vertical migration was observed for O. nigra, with a night ascent of young larvae, and ontogenetic differences. These different patterns in the two bays mediate the effects of tidal currents on larval fluxes. O. fragilis larvae were mainly distributed above the thermocline which may favour larval retention within the bay, while A. filiformis larvae, mostly concentrated near the bottom, were preferentially exported. This study highlighted the complex interactions between coastal hydrodynamics and specific larval traits, e.g. larval morphology, in the control of larval vertical distribution and larval dispersal.