DOI: 10.5061/dryad.kd51c5bj0
title: Data from: Marine heatwaves amplify benthic community metabolism and solute flux in a seafloor heating experiment

description: The magnitude and frequency of marine heatwaves is increasing and
 predicted to intensify, but our ability to understand the real-world
 effects on vital benthic ecosystems is lagging behind. Prior insights into
 the impacts of marine heatwaves are often derived from observational or
 laboratory studies. Observational studies may not fully disentangle the
 complexities of potential compound events and typically focus on severe,
 often lethal marine heatwaves. Laboratory studies on the other hand, while
 valuable for understanding specific mechanisms, often use artificial
 setups and can introduce unnatural disturbances that do not reflect
 real-world scenarios. To investigate sublethal temperature effects of
 marine heatwaves in a natural benthic habitat, we developed a novel
 approach for inducing elevated water temperatures in situ over several
 days. The system utilizes domestic under-floor heating technology combined
 with custom-made benthic chambers. We placed 10 chambers for 15 days in a
 bare-sediment habitat at 2.5 m depth and heated 5 chambers to 5°C above
 ambient water temperatures in summer for 6 days followed by a period of 7
 days at ambient temperatures. Incubations during day and night were
 performed during the experiment to assess changes in ecosystem functioning
 (solute fluxes) and sediment cores were collected at the end of the
 experiment to assess the effects of a realistic marine heatwave on benthic
 community structure. 4. The results indicate that while the benthic
 community structure remained similar between the treatments, except for a
 size shift of Marenzelleria spp. towards smaller individuals in the heated
 treatment, elevated temperatures caused a significant increase in the
 community respiration and amplified the magnitude of either efflux or
 influx of nutrients (NH4+-N, PO43--P, Si). Primary production during
 daytime incubations remained mostly unaffected by the heatwave treatment,
 contributing to the concept of heterotrophy being more influenced by
 increased temperature than autotrophy. This study confirms the suitability
 of the novel system for examining the impact of temperature on benthic
 habitats in situ and demonstrates its potential for investigation of
 complex habitats and communities, which is essential for our understanding
 of the ecosystem-level effects of climate change.
description: # Marine heatwaves amplify benthic community metabolism and solute flux in
 a seafloor heating experiment
 [https://doi.org/10.5061/dryad.kd51c5bj0](https://doi.org/10.5061/dryad.kd51c5bj0) ## Description of the data and file structure ### Files and variables The files in this repository contain all necessary information to replicate the results of the linked article. The input and output file data formats are typically .txt or .csv files. The analysis of the data was conducted in R studio with .R files included in the .zip folders. The .zip folders are grouped by data and scripts related to either the Benthic Macrofauna Community, Nutrient and Oxygen fluxes, and Temperature data of the Benthic Chambers. ### File: Community.zip **Description:** Contains 3 data files with values for abundance, biomass, and size data of macrofaunal species identified in all 10 benthic chambers. Further contains 1 R script analysing community data. #### **File Name:** Abundance\_sq-meter.txt **Description:** This file contains macrofaunal abundance (individuals per square meter, ind./m²) for different taxa under two experimental treatments: Control and Heat (marine heatwave exposure). Each row represents an individual sample, with taxon-specific abundances recorded for each replicate. **Missing Values:** Not explicitly present in the file. #### **File Name:** Biomass\_sq-meter.txt **Description:** This file contains macrofaunal biomass (blotted wet weight, g/m²) for different taxa under two experimental treatments: Control and Heat (marine heatwave exposure). Each row represents an individual sample, with taxon-specific biomass recorded for each replicate. **Missing Values:** Not explicitly present in the file. #### **File Name:** Community\_sizes.csv **Description:** This file contains the size measurements of each organism in [mm] under two experimental treatments: Control and Heat (marine heatwave exposure). Each row represents an individual organism. **Missing Values:** Not explicitly present in the file. #### **File Name:** Community\_nmds\_1.R **Description:** This file is an .R script that was used to analyse the community data. ### File: Nutrients.zip **Description:** Contains 1 data file with all measured fluxrates during, 4 output files with either averaged rates or statistical results, and two .R files specifying the analyses. #### **File Name:** Fluxrates\_mmol.csv **Description:** This dataset contains all nutrient and oxygen flux rate measurements from all incubations. Measurements were taken at varying time points/sampling, here named "phases", treatments, and light conditions (incubations conducted during day and night time). #### **File Name:** Average solute rates.csv **Description:** This dataset contains summary statistics of nutrient and oxygen flux rate measurements from all incubations. Data includes mean flux rates, standard deviations, sample sizes, and standard errors under different phases, treatments, and light conditions. #### **File Name:** Fluxrates\_1.R **Description:** This script is used to generate overview plots and summary tables based on Fluxrates_mmol.csv. #### **File Name:** Fluxrates\_stats1.R **Description:** This file is an .R script that was used tanalyzese the fluxrates data. #### **File Name:** PCA\_loading values **Description:** This dataset contains principal component analysis (PCA) loadings for oxygen, ammonium, silicate, and phosphate flux rates. #### **File Name:** Results\_overall PERMANOVA.txt **Description:** This file contains the results from the overall Model applied to identify the effect of Sampling, Light/Dark and Treatment on oxygen and nutrient fluxes. #### **File Name:** Results\_PERMANOVA\_subsets.txt **Description:** This file contains the results from the treatment focused analyses applied to identify the effect of Treatment on oxygen and nutrient fluxes within the subsets of Sampling and Light/Dark. ### File: Temperature.zip **Description:** Contains 1 data file with measured temperatures in each benthic chamber (10 chambers, 15min frequency), 1 data file containing the climatological values necessary for assessing MHWs (Goebeler et al., 2022), one output file included in the supplementary material, and one .R file analysing the temperature data. #### **File Name:** Climatology.txt **Description:** This file contains data related to climatological temperatures based on Goebeler et al., 2022 and allows to classify extreme temperatures.  #### **File Name:** Temperature.csv **Description:** All measured temperatures from all benthic chambers at a 15min frequency between 02.07.2021-15.07.2021. #### **File Name:** MHW\_1.R **Description:** R-script utilized toanalyzee the temperature in the benthic chambers based on the climatological values. #### **File Name:** Temperature data for supplementary.txt **Description:** Output data file summarizing temperature conditions during the experiment presented in supplementary material. ## Access information Data was derived from the following sources: * Climatology.txt derived from [https://doi.org/10.5061/dryad.8cz8w9gtf](https://doi.org/10.5061/dryad.8cz8w9gtf)