DOI: 10.5061/dryad.vhhmgqns7
title: Heatwave grazing kelp microbes sequences

description: The range-expansion of tropical herbivores due to ocean warming can
 profoundly alter temperate reef communities by overgrazing the seaweed
 forests that underpin them. Such ecological interactions may be mediated
 by changes to seaweed-associated microbiota in response to warming, but
 empirical evidence demonstrating this is rare. We experimentally simulated
 ocean warming and marine heatwaves (MHWs) to quantify effects on two
 dominant temperate seaweed species and their microbiota, as well as
 grazing by a tropical herbivore. The kelp Ecklonia radiata’s microbiotain
 sustained warming and MHW treatments were enriched with microorganisms
 associated with seaweed disease and tissue degradation. In contrast, the
 fucoid Sargassum linearifolium’s microbiota was unaffected by temperature.
 Consumption by the tropical sea-urchin Tripneustes gratilla was
 greater on Ecklonia where the microbiota had been altered by higher
 temperatures, while Sargassum’s consumption was unaffected. Elemental
 traits (carbon, nitrogen), chemical defences (phenolics) and tissue
 bleaching of both seaweeds were generally unaffected by temperature.
 Effects of warming and MHWs on seaweed holobionts (host plus its
 microbiota) are likely species-specific. The effect of increased
 temperature on Ecklonia’s microbiota and subsequent increased consumption
 suggest that changes to kelp microbiota may underpin kelp-herbivore
 interactions, providing novel insights into potential mechanisms driving
 change in species’ interactions in warming oceans.
description: # Heatwave grazing kelp microbes sequences
 [https://doi.org/10.5061/dryad.vhhmgqns7](https://doi.org/10.5061/dryad.vhhmgqns7) We experimentally simulated ocean warming and marine heatwaves (MHWs) to quantify effects on two dominant temperate seaweed species and their microbiota, as well as grazing by a tropical herbivore. The kelp *Ecklonia radiata*’s microbiota in sustained warming and MHW treatments were enriched with microorganisms associated with seaweed disease and tissue degradation. In contrast, the fucoid *Sargassum linearifolium*’s microbiota was unaffected by temperature\*.\* Consumption by the tropical sea-urchin *Tripneustes gratilla* was greater on *Ecklonia* where the microbiota had been altered by higher temperatures, while *Sargassum*’s consumption was unaffected. Elemental traits (carbon, nitrogen), chemical defences (phenolics) and tissue bleaching of both seaweeds were generally unaffected by temperature. ## Description of the data and file structure Juvenile *Ecklonia radiata* (length \~15cm; N=140) and *Sargassum linearifolium* (length \~10cm; N=140) were collected haphazardly (&gt;2m apart) at Cronulla rocky reef, Sydney, Australia. We exposed seaweeds to one of four temperature profiles over seven weeks: Ambient, Warming, marine heatwave MHW, MHW variable. After seven weeks of exposure to temperature treatments, a subset of individuals from each species/temperature treatment (*Ecklonia*: n=4-6; *Sargassum*: n=3) were randomly selected. Sterile cotton swabs were used to sample microbiota on algal surfaces, with the same area (20cm<sup>2</sup>) and swabbing time (30s) sampled for all individuals. Swabs were immediately stored in liquid nitrogen and transported to the University of New South Wales (UNSW, Sydney) and kept at -80°C until DNA extraction. DNA was extracted from swabs using the DNeasy PowerSoil Kit (Qiagen) and amplified using Polymerase Chain Reaction (PCR) primers 341F (5’-CCTACGGGNGGCWGCAG-3’) and 785R (5’-GACTACHVGGGTATCTAATCC-3’), targeting the 16S rRNA gene V3-V4 regions (bacteria and archaea), and were sequenced with a 2x250bp MiSeq reagent kit v2 on the Illumina MiSeq2000 Platform.