Microspatial variability in community structure and photophysiology of calcified macroalgal microbiomes revealed by coupling of hyperspectral and high-resolution fluorescence imaging.

J Brodie,P Launeau,M L Yallop,R G Perkins,B Jesus,L Barillé,C J Williamson,J Lavaud

doi:10.1038/srep22343

Abstract

Calcifying coralline macroalgae provide biogenic habitats colonised by epiphytic microalgae that contribute significantly to community productivity. Georeferenced hyperspectral and high-resolution fluorescence imaging were coupled to microspatially mapped community composition and relative biomass of macroalgal host and epiphyte microalgal groups, and their weighted contributions to productivity within host fronds of Corallina officinalis on upper and lower zones of a rocky shore were determined. Lower shore epiphytes were dominated by filamentous diatoms (Bacillariophyta), confined to the apex of the frond structure, which were low light acclimated but retained a high capacity for photoprotective down regulation and contributed up to 51% of total community productivity. Upper shore epiphytes were dominated by green algae (Chlorophyta) and single-celled diatoms (principally Cocconeis spp.), which were high light acclimated but present at far lower relative biomass and contributed negligibly to productivity. The host, C. officinalis was the main primary producer. Variation in light environment resulting from differences in shore height and shading within the host macroalga, likely play a large role in determining patterns in epiphyte community structure, biomass and productivity observed. Additionally, microspatial gradients in photophysiological parameters along the host macroalga likely resulted from age-dependent variation in pigments as well as the gradient in light environment.

Highlights

Calcifying coralline macroalgae provide biogenic habitats colonised by epiphytic microalgae that contribute significantly to community productivity
Total phototrophic biomass of the community as indicated by extracted chlorophyll a (Chl a) (Fig. 1a) showed a higher biomass on the lower shore compared to the upper shore, with incremental increases from low, to medium to high-epiphyte biomass category
On the lower shore the epiphyte community was dominated by diatoms with highly significant correlations between the hyperspectral measurement of relative abundance of diatoms and pigment data for chlorophyll c (Chl c) (r = 0.96, p < 0.01; Fig. 1c), fucoxanthin (r = 0.98, p < 0.01; Fig. 1d) and diadinoxanthin (r = 0.95, p < 0.01; Fig. 1e)

Summary

Introduction

Calcifying coralline macroalgae provide biogenic habitats colonised by epiphytic microalgae that contribute significantly to community productivity. The spatial variation in photosynthetic microalgal epiphytes on the host C. officinalis was investigated on both a large scale (across shore heights on a rocky shore) and small scale (within individual fronds), with measurements made concomitantly for the epiphyte community and the host frond. This was achieved using a novel combination of state-of-the-art hyperspectral and high-resolution variable chlorophyll fluorescence imaging (see Ralph et al.[27] for an overview of fluorescence imaging). Epiphyte productivity is a major contribution to the overall community productivity, dependent upon the dominant epiphyte taxa present

Methods

Results

Conclusion