Constrained nearshore larval distributions and thermal stratification

Abstract

© The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Marine Ecology Progress Series 595 (2018): 105-122, doi:10.3354/meps12561.Vertical and cross-shore distributions and abundances of shallow-water barnacle larvae were characterized in La Jolla, southern California (USA), during a 2 yr period. Five stations located within 1 km of shore and ranging from 4-12 m water depths were sampled intensively in 2 m depth intervals during 27 cruises throughout spring-summer (April-July) and fall-winter (October-December) of 2014 and 2015. Larval abundances significantly decreased from 2014 to 2015, which could be related to the arrival of a warm-water anomaly (the so-called ‘Blob’) in 2014 and El Niño conditions in 2015. Despite the presence of these large-scale regional disturbances, vertical and cross-shore larval distributions were consistent throughout the 2 yr study period. Early-stage nauplii and Chthamalus fissus cyprids tracked bottom depth, and cyprids were on average deeper than nauplii. Vertical distributions were not related to the mid-depth of the thermocline or thermal stratification. Early-stage nauplii had a broader cross-shore distribution than cyprids, which were concentrated at inshore stations. Nearshore cyprid concentration had a positive relationship with thermal stratification, and the center of distribution of cyprids was farther offshore during fall-winter when stratification decreased. These results suggest that thermal stratification elicits enhanced behavioral control of cyprids to remain close to shore and reach the adult habitat.This material is based upon work supported by the National Science Foundation under grants OCE-1357290, OCE-1357327, OCE-1630459, and OCE- 1630474. Support was also provided by the University of San Diego and Woods Hole Oceanographic Institution