title: Attachment strength of the subtidal seaweedSargassum horneri(Turner) C. Agardh varies among development stages and depths.
abstract: Sargassum horneriis one of the most important contributors to the rafts of floating seaweed in the waters off the coasts of northeastern Asia. These rafts serve as spawning and nursery grounds for many marine organisms, including Japanese saury and yellowtail. Thus, the details of the attachment/detachment mechanisms ofS. horneriare of commercial significance for the aquaculture industry. Here, we describe variations in the attachment strength ofS. hornerias it relates to its developmental stage and depth along a bottom gradient. We measured the attachment strength/dislodgement force ofS. hornerisamples with holdfast detachment in Shidagaura Cove, Shimoda, Japan, from December 2014 to May 2015. After we had determined the dislodgement forces required to detach thalli from the substratum (using a spring scale device) in the field, we transferred released individuals to the laboratory and measured selected morphological traits. Attachment strength was linearly related to the holdfast basal area when thalli were immature (prior to mid-March), but not when they were mature (mid-March to May). Thus, attachment strength was maintained through the reproductive phase and declined thereafter, allowing released thalli to join the drifting raft community. Rafting may be a mechanism by which the species expands its distribution range, as floating thalli continuing to shed germlings that are able to recruit when suitable habitat is encountered. Attachment strengths were greater in the shallows than in deeper water, reflecting the differences in wave forces experienced at different depths.
authors.affiliation: Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa City, Chiba 277-0882 Japan.
authors.forename: Min
authors.initials: M
authors.lastname: Xu
authors.affiliation: Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa City, Chiba 277-0882 Japan.
authors.forename: Shingo
authors.initials: S
authors.lastname: Sakamoto
authors.affiliation: Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa City, Chiba 277-0882 Japan.
authors.forename: Teruhisa
authors.initials: T
authors.lastname: Komatsu
keywords: Attachment strength; Depth; Maturity stages; Phaeophyceae; Sargassum horneri