Bayat, H. S. | Search bioRxiv

bioRxiv2024

Global thermal tolerance of freshwater invertebrates and fish

Scientists have investigated the thermal tolerance of organisms for centuries, yet the field has not lost relevance as the environmental threats of thermal pollution and global change sharpen the need to understand the thermal vulnerability of organisms in landscapes increasingly subjected to multiple stressors. Freshwater fish and especially invertebrates are greatly underrepresented in recent large-scale compilations of thermal tolerance, despite the importance of freshwater habitats as a crucial resource and biodiversity havens. This inspired us to create a thermal tolerance database for these organisms that includes literature from 1900 until the present day sourced from five languages to counteract geographic bias, and 395 thermal tolerance tests conducted with additional stressors present. The database contains over 5000 records for over 800 species, including 452 invertebrates, providing a valuable resource to test hypotheses on thermal risks to freshwater organisms in present and future environments, and how these might change in multiple stressor scenarios.

ecology↗

bioRxiv2024

Putting the Asymmetric Response Concept to the test: modeling multiple stressor exposure and release in a stream food web

Communities in stream ecosystems often respond asymmetrically to increase and release of stressors, as indicated by slow and incomplete recovery. The Asymmetric Response Concept (ARC) posits that this is due to a shift in the relative importance of three mechanisms: tolerance, dispersal, and biotic interactions. In complex natural communities, these mechanisms may produce alternative outcomes through poorly understood indirect effects. To understand how the three mechanisms respond to different temporal stressor scenarios, we studied multiple scenarios using a stream food web model. We asked the following questions: Do groups of species decline as expected on the basis of individual tolerance rankings derived from laboratory experiments when they are embedded in a complex dynamic food web? Does the response of ecosystem function match that of communities? To address these questions, we aggregated data on individual tolerances at the level of functional groups and studied how single and multiple stressors affect food web dynamics and nutrient cycling. Multiple stressor scenarios involved different intensities of salt and temperature increase. Functional groups exhibited a different relative tolerance ranking between the laboratory and dynamic food web contexts. Salt as a single stressor had only minor and transient effects at low level but led to the loss of one or more functional groups at high level. In contrast, high temperature, alone or in combination with salt, caused the loss of functional groups at all tested levels. Patterns often differed between the response of communities and ecosystem function. We discuss our findings with respect to the ARC. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=106 SRC="FIGDIR/small/601677v1_ufig1.gif" ALT="Figure 1"> View larger version (23K): org.highwire.dtl.DTLVardef@2924f0org.highwire.dtl.DTLVardef@138400aorg.highwire.dtl.DTLVardef@1f45126org.highwire.dtl.DTLVardef@fba006_HPS_FORMAT_FIGEXP M_FIG C_FIG

ecology↗