Data from: Physical and biological factors affect the vertical distribution of larvae of benthic gastropods in a shallow embayment

Marine gastropods form a diverse taxonomic group, yet little is known
about the factors that affect their larval distribution and abundance. We
investigated the larval vertical distribution and abundance of 9
meroplanktonic gastropod taxa (Margarites spp., Crepidula spp., Astyris
lunata, Diaphana minuta, Littorinimorpha, Arrhoges occidentalis, Ilyanassa
spp., Bittiolum alternatum and Nudibranchia), with similar morphology and
swimming abilities, but different adult habitats and life-history
strategies. We explored the role of physical (temperature, salinity,
density, current velocities) and biological (fluorescence) factors, as
well as periodic cycles (lunar phase, tidal state, diel period) in
regulating larval vertical distribution. Using a pump, we collected
plankton samples at 6 depths (3, 6, 9, 12, 18 and 24 m) at each tidal
state, every 2 h over a 36 and a 26 h period, during a spring and neap
tide, respectively, in St. George’s Bay, Nova Scotia. Concurrently, we
measured temperature, salinity, density, fluorescence (as a proxy for
chlorophyll, i.e. phytoplankton density), and current velocity. Larval
abundance was most strongly related to temperature, except for
Littorinimorpha and Crepidula spp., for which it was most strongly related
to fluorescence. Margarites spp., A. lunata, Ilyanassa spp. and B.
alternatum exhibited either diel or reverse-diel vertical migration during
1 or both lunar phases. For Crepidula spp., Littorinimorpha, A.
occidentalis and Nudibranchia, larval vertical distribution differed
between lunar phases. Only the larval vertical distribution of Margarites
spp., D. minuta and Ilyanassa spp. varied with tidal state during 1 or
both lunar phases. The key factors determining the vertical distribution
of gastropod larvae were temperature, fluorescence, and light, although
the importance of each factor varied among taxa. Differences in vertical
distribution may enable these larvae to partition over a wide range of
potential habitats for settlement.