DOI: 10.5061/dryad.kprr4xhj0
title: Warming threatens aquatic-terrestrial linkages: evidence from tropical geothermal streams

description: Terrestrial and aquatic ecosystems are connected through energy fluxes
 partially driven by aquatic organisms that migrate to terrestrial
 environments during adulthood. According to the thermal performance curve
 (TPC) framework the physiological performance of organisms is limited at
 low temperatures, which can affect the body mass of freshwater insects,
 stoichiometric imbalances, abundances, and emergence frequency to riparian
 systems. As temperatures approach the optimal point on the TPC, energy
 fluxes to terrestrial ecosystems are expected to accelerate. However, in
 warmer environments, where temperatures exceed the optimal point, organism
 performance can be severely compromised, restricting the occurrence of
 aquatic species and potentially leading to a collapse of energy fluxes
 between ecosystems. Therefore, we predict that terrestrial predators that
 rely on aquatic subsidies (e.g., spiders) will benefit by living near
 water sources with intermediate temperatures, where aquatic insect
 emergence is expected to be highest. We tested these predictions by using
 natural experiments in several geographically independent tropical
 geothermal streams, where we surveyed aquatic and riparian terrestrial
 arthropods upon plants, along contrasting levels of water temperatures
 (range 25.9 to 41.9°C). Structural equation modeling detected a direct,
 hump-shaped impact of temperature on the abundance of aquatic insects and
 an indirect effect on spiders’ abundance and richness, which declined in
 response to the reduction of aquatic insects. This result is substantiated
 by δ13C and δ15N isotopic analyses, which detected a higher consumption of
 aquatic insects in locations with temperatures below 34°C. These results
 highlight that an increase in temperature can disrupt the trophic dynamics
 between aquatic and terrestrial ecosystems. Furthermore, our findings
 reinforce the role of geothermal systems as natural laboratories for
 studying the effects of warming on trophic interactions, providing novel
 insights into how temperature influences cross-ecosystem energy transfer
 and predator-prey dynamics in interconnected aquatic and terrestrial food
 webs.
description: # Warming threatens aquatic-terrestrial linkages: evidence from tropical
 geothermal streams Dataset DOI:
 [10.5061/dryad.kprr4xhj0](10.5061/dryad.kprr4xhj0) ## Description of the
 data and file structure This repository contains the dataset and analysis
 script used in the article **"Warming threatens aquatic-terrestrial
 linkages: evidence from tropical geothermal streams"**, which
 investigates how natural thermal gradients in tropical geothermal streams
 influence the abundance of aquatic and terrestrial invertebrates, focusing
 on energy flow between ecosystems. The dataset includes thermal variables,
 abundances of arthropod functional groups, and geographic coordinates of
 each sampling point. Analyses were conducted using **piecewise Structural
 Equation Modeling (SEM)** and **Moran’s I tests** to assess spatial
 autocorrelation. Field sampling was conducted across seven catchments
 located in Mato Grosso and Goiás, Brazil, between 2021 and 2022, along a
 temperature gradient ranging from 25.9 to 42.4 °C. 
 
 ### Files and variables ### Repository Contents * `Data_thermal.csv`:
 Spreadsheet with invertebrate abundances, environmental variables, and
 geographic coordinates for each sampling point. * `Script_SEM_Moran.R`: R
 script containing the statistical procedures described in the article (SEM
 modeling and Moran’s I tests). 
 
 ### Data Structure (`Data_thermal.csv`) **Sheet:
 "**`Data_thermal`**"** #### **Columns description:** * **Site**:
 Sampling site identifier. * **Location**: Name of the geothermal
 stream/catchment. * **Cyti**: Municipality where the site is located. *
 **Latitude, Longitude**: Geographic coordinates of the sampling site
 (degrees, minutes, seconds). * **Water temperature (°C)**: Temperature of
 the stream water. * **Margin temperature (°C)**: Temperature measured at
 the stream margin. * **pH**: Water pH. * **TDS (mg/L)**: Total dissolved
 solids in water. * **DO (mg/L)**: Dissolved oxygen. * **CD (µS/cm)**:
 Electrical conductivity of the water. * **Litter_kg**: Mass of litter (kg)
 sampled at the site. * **Plant_kg**: Mass of vegetation/plant biomass
 (kg). * **Spider richness**: Number of spider taxa recorded. * **Spider
 abundance**: Total number of spider individuals. * **Herbivores
 richness**: Number of terrestrial herbivore taxa. * **Herbivores
 abundance**: Total number of terrestrial herbivore individuals. *
 **Aquatic richness**: Number of aquatic insect taxa. * **Aquatic
 abundance**: Total number of aquatic insect individuals. The variables
 used in the script correspond: * `Temp_agua`: Water temperature (°C) *
 `N.aqua`: Abundance of aquatic insects with a terrestrial adult phase *
 `N.arac`: Abundance of spiders * `N.herb`: Abundance of terrestrial
 herbivores * `Longitude`, `Latitude`: Geographic coordinates (decimal
 degrees) * `Location`: Identifier for the geothermal catchment Note:
 Transformed and centered variables used in the statistical analyses are
 created within the script and are not included in the original
 spreadsheet. 
 
 ## Code/software ### Script Requirements The file `Psem_thermal.R` was
 written in **R (version 4.2.2)** and requires the following packages: *
 `nlme` * `piecewiseSEM` * `spdep` ### ## Access information ### License
 This dataset is made available under the **CC0 1.0 Universal (Public
 Domain Dedication)** license: free to use, share, and adapt. We would also
 appreciate appropriate attribution. ### How to Cite This Dataset Lopes, A.
 S., Izzo, T., & Romero, G. Q. (2025). *Thermal gradients in tropical
 geothermal streams and their effects on aquatic-terrestrial energy
 fluxes*. Dryad Digital Repository.
 [https://doi.org/10.1002/oik.11310](https://doi.org/10.1002/oik.11310)