Above-below surface interactions mediate effects of seagrass disturbance on meiobenthic diversity, nematode and polychaete trophic structure

Francisco J A Nascimento,Simon Creer,Diana Deyanova,Mats Björk,Liberatus D Lyimo,Tiago José Pereira,Martin Gullström,Holly M Bik,Taruna Schuelke,Martin Dahl

doi:10.1038/s42003-019-0610-4

Abstract

Ecological interactions between aquatic plants and sediment communities can shape the structure and function of natural systems. Currently, we do not fully understand how seagrass habitat degradation impacts the biodiversity of belowground sediment communities. Here, we evaluated indirect effects of disturbance of seagrass meadows on meiobenthic community composition, with a five-month in situ experiment in a tropical seagrass meadow. Disturbance was created by reducing light availability (two levels of shading), and by mimicking grazing events (two levels) to assess impacts on meiobenthic diversity using high-throughput sequencing of 18S rRNA amplicons. Both shading and simulated grazing had an effect on meiobenthic community structure, mediated by seagrass-associated biotic drivers and sediment abiotic variables. Additionally, shading substantially altered the trophic structure of the nematode community. Our findings show that degradation of seagrass meadows can alter benthic community structure in coastal areas with potential impacts to ecosystem functions mediated by meiobenthos in marine sediments.

Highlights

Ecological interactions between aquatic plants and sediment communities can shape the structure and function of natural systems
The Illumina Miseq dataset of eukaryotic 18S ribosomal RNA amplicons generated a total of 10,320,000 raw paired-end reads from 24 samples, resulting in a total of 6,180,945 quality-filtered reads after read merging and primer trimming, which led to an average of 257,539 sequences per sample
The percentage of operational taxonomic unit (OTU) belonging to metazoan groups was high for all seagrass treatments (on average 86, 80, 87,87, and 86% in Control (CTRL), High clipping (HC), High shading (HS), Low clipping (LC), Low shading (LS), respectively), and highest in the unvegetated treatment with 96% (Supplementary Fig. 2), confirming that sieving and density extraction is an effective way to isolate metazoan organisms as found in previous works[37]

Summary

Introduction

Ecological interactions between aquatic plants and sediment communities can shape the structure and function of natural systems. Disturbance was created by reducing light availability (two levels of shading), and by mimicking grazing events (two levels) to assess impacts on meiobenthic diversity using highthroughput sequencing of 18S rRNA amplicons Both shading and simulated grazing had an effect on meiobenthic community structure, mediated by seagrass-associated biotic drivers and sediment abiotic variables. As meiobenthos mediate important benthic ecosystem processes, it is crucial to understand how indirect effects of eutrophication and overfishing-induced changes on plant above and below-ground biomass affect meiobenthic communities. Such an understanding is vital to predict future impacts on marine ecosystem structure and function[35]

Methods

Results

Conclusion