The north–south divide? Macroalgal functional trait diversity and redundancy varies with intertidal aspect

Axelle Amstutz, Louise B. Firth, Andy Foggo, John I. Spicer, Mick E. Hanley*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Background and Aims Marine macroalgae (‘seaweeds’) are critical to coastal ecosystem structure and function, but also vulnerable to the many environmental changes associated with anthropogenic climate change (ACC). The local habitat conditions underpinning observed and predicted ACC-driven changes in intertidal macroalgal communities are complex and probably site-specific and operate in addition to more commonly reported regional factors such as sea surface temperatures. Methods We examined how the composition and functional trait expression of macroalgal communities in SW England varied with aspect (i.e. north–south orientation) at four sites with opposing Equator- (EF) and Pole-facing (PF) surfaces. Previous work at these sites had established that average annual (low tide) temperatures vary by 1.6 °C and that EF-surfaces experience six-fold more frequent extremes (i.e. >30 °C). Key Results PF macroalgal communities were consistently more taxon rich; 11 taxa were unique to PF habitats, with only one restricted to EF. Likewise, functional richness and dispersion were greater on PF-surfaces (dominated by algae with traits linked to rapid resource capture and utilization, but low desiccation tolerance), although differences in both taxon and functional richness were probably driven by the fact that less diverse EF-surfaces were dominated by desiccation-tolerant fucoids. Conclusions Although we cannot disentangle the influence of temperature variation on algal ecophysiology from the indirect effects of aspect on species interactions (niche pre-emption, competition, grazing, etc.), our study system provides an excellent model for understanding how environmental variation at local scales affects community composition and functioning. By virtue of enhanced taxonomic diversity, PF-aspects supported higher functional diversity and, consequently, greater effective functional redundancy. These differences may imbue PF-aspects with resilience against environmental perturbation, but if predicted increases in global temperatures are realized, some PF-sites may shift to a depauperate, desiccation-tolerant seaweed community with a concomitant loss of functional diversity and redundancy.

Original languageEnglish
Pages (from-to)145-152
Number of pages8
JournalAnnals of Botany
Volume133
Issue number1
Early online date16 Nov 2023
DOIs
Publication statusPublished - 1 Jan 2024

ASJC Scopus subject areas

  • General Medicine

Keywords

  • Anthropogenic climate change
  • aspect
  • biodiversity–ecosystem functioning
  • extreme temperatures
  • functional redundancy
  • functional traits
  • rocky shore
  • seaweed
  • England
  • Plants
  • Biodiversity
  • Seaweed
  • Phenotype
  • Ecosystem

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