Instantaneous Flow Structures and Opportunities for Larval Settlement: Barnacle Larvae Swim to Settle
Journal article, 2016

Water flow affects settlement of marine larvae on several scales. At the smallest scale local flow regime may control the probability of adhesion to the substrate. Our aim was to mechanistically understand the transition from suspended to attached larvae in turbulent flow. Recently it was proposed that opportunities for larval settlement in turbulent boundary layers depend on time windows with suitable instantaneous flow properties. In flume flow we characterized the proportion of suitable time windows in a series of flow velocities with focus on the near-bed flow. The change in the proportion of potential settling windows with increasing free-stream velocities was compared to the proportion of temporary attachment of barnacle cypris larvae at different flow velocities. We found large instantaneous flow variations in the near-bed flow where cyprid attachment took place. The probability of temporary attachment in cyprids declined with local flow speed and this response was compatible with a settling window lasting at least 0.1 s with a maximum local flow speed of 1.9–2.4 cm s-1. Cyprids swam against the near-bed flow (negative rheotaxis) and the swimming speed (1.8 cm s-1) was close to the critical speed that permitted temporary attachment. We conclude that temporary attachment in barnacle cyprids requires upstream swimming to maintain a fixed position relative to the substrate for at least 0.1 s. This behaviour may explain the ability of barnacles to recruit to high-flow environments and give cyprids flexibility in the pre-settlement choice of substrates based on flow regime.

barnacles

flow structures

Author

Ann I. Larsson

University of Gothenburg

Lena Granhag

Chalmers, Shipping and Marine Technology, Maritime Environmental Sciences

University of Gothenburg

Per R. Jonsson

University of Gothenburg

PLoS ONE

1932-6203 (ISSN)

Vol. 11 7 e0158957-

Areas of Advance

Transport

Subject Categories

Biological Sciences

DOI

10.1371/journal.pone.0158957

PubMed

27463968

More information

Created

10/7/2017