Limited congruence exhibited across microbial, meiofaunal and macrofaunal benthic assemblages in a heterogeneous coastal environment

Ian Jermyn,Mark P. Johnson,A. Louise Allcock,Sorcha Cronin-O’Reilly,Michael Cunliffe,Joe D. Taylor

doi:10.1038/s41598-018-33799-9

Abstract

One of the most common approaches for investigating the ecology of spatially complex environments is to examine a single biotic assemblage present, such as macroinvertebrates. Underlying this approach are assumptions that sampled and unsampled taxa respond similarly to environmental gradients and exhibit congruence across different sites. These assumptions were tested for five benthic groups of various sizes (archaea, bacteria, microbial eukaryotes/protists, meiofauna and macrofauna) in Plymouth Sound, a harbour with many different pollution sources. Sediments varied in granulometry, hydrocarbon and trace metal concentrations. Following variable reduction, canonical correspondence analysis did not identify any associations between sediment characteristics and assemblage composition of archaea or macrofauna. In contrast, variation in bacteria was associated with granulometry, trace metal variations and bioturbation (e.g. community bioturbation potential). Protists varied with granulometry, hydrocarbon and trace metal predictors. Meiofaunal variation was associated with hydrocarbon and bioturbation predictors. Taxon turnover between sites varied with only three out of 10 group pairs showing congruence (meiofauna-protists, meiofauna-macrofauna and protists-macrofauna). While our results support using eukaryotic taxa as proxies for others, the lack of congruence suggests caution should be applied to inferring wider indicator or functional interpretations from studies of a single biotic assemblage.

Highlights

Taxa are typically thought to vary in their tolerance of environmental stresses and contaminants[1,2]
We examined the congruence of five benthic groups to multiple gradients in Plymouth Sound
Cawsand Bay was the site with the highest sand particle fraction, with Sutton Lock dominated by silts

Summary

Introduction

Taxa are typically thought to vary in their tolerance of environmental stresses and contaminants[1,2] This is the basis of biotic indices like the AZTI Marine Biotic Index (AMBI) used to summarize ecological quality from the relative abundance of macroinvertebrates classified into groups representing different tolerance levels[2]. Variability in ecosystem function is unlikely to be predictable from a single assemblage[9] if other functionally important groups respond in different ways to shared environmental conditions. Anthropogenic contaminants like hydrocarbons and metals are commonplace stressors in these areas This sort of multiple-stress context provides a more demanding test of congruence in taxon responses to environmental and anthropogenic stresses. We examined the congruence of five benthic groups (archaea, bacteria, microbial eukaryotes/protists, meiofauna and macrofauna) to multiple gradients in Plymouth Sound. As macrofauna can influence other groups by sediment reworking, an index of bioturbation (community bioturbation potential, BPc)[18] and the distribution of different functional types of bioturbation were derived to test whether these variables influenced the occurrence of taxa within groups

Methods

Results

Conclusion