New aspect in seagrass acclimation: leaf mechanical properties vary spatially and seasonally in the temperate species Cymodocea nodosa Ucria (Ascherson)

Mar Biol (2013) 160:10831093 DOI 10.1007/s00227-012-2159-3

ORIGINAL PAPER

New aspect in seagrass acclimation: leaf mechanical properties vary spatially and seasonally in the temperate species Cymodocea nodosa Ucria (Ascherson)

Carmen B. de los Santos Fernando G. Brun

Juan J. Vergara Jos Lucas Prez-Llorns

Received: 30 July 2012 / Accepted: 19 December 2012 / Published online: 9 January 2013 Springer-Verlag Berlin Heidelberg 2013

Abstract Seagrasses may acclimate to environmental heterogeneity through phenotypic plasticity. In contrast to leaf morphology, which has been a central point in seagrass acclimation studies, plasticity in leaf biomechanics and bre content is poorly understood, despite being crucial in plant ecological performance, especially regarding physical forces. We hypothesised that mechanical traits (e.g. breaking force, strength, toughness, and stiffness) and bre content of seagrass leaves vary as morphology does under differential environments. Cymodocea nodosa was seasonally monitored at three locations around Cdiz Bay (southern Spain) with hydrodynamic regime as the most noticeable difference between them. Leaves showed plasticity in both morphology and mechanical traits, with wave-exposed individuals presenting short but extensible and tough leaves. Leaf bre content was invariant along the year and with little spatial variability. Cross-sectional area rather than material properties or bre content differentiates leaf mechanical resistance. Seagrass capacity to thrive under a range of mechanical forces may be dictated by their plasticity in morpho-biomechanical traits, a key element for the hydrodynamical performance and, hence, for species colonisation and distribution.

Introduction

Seagrasses are clonal plants living in shallow coastal waters, exposed to high environmental variability. In heterogeneous environments, phenotypic plasticity (i.e. the potential ability of an organism to change its phenotype in response to environmental forcing) may be benecial (Sultan 1987; Pigliucci 2001), although it may also be costly and limited (DeWitt et al. 1998). In seagrasses, the well-documented and noticeable phenotypic plasticity allows these organisms to acclimate to environmental heterogeneity and cope with environmental stresses (Hemminga and Duarte 2000). The magnitude of the intraspecic variability for a plant trait, normally quantied as the coefcient of variation within species (Marb and Duarte 1998; Brun et al. 2006), reects seagrass capacity to colonise and survive to environmental changes (Marb and Duarte 1998) and may explain species distribution (Mascar et al. 2009).

The environmental variability manifests at spatial and/or temporal scales, being the latter...