Large-scale climatic phenomena drive fluctuations in macroinvertebrate assemblages in lowland tropical streams, Costa Rica: The importance of ENSO events in determining long-term (15y) patterns.

Pablo E. Gutiérrez-Fonseca,Catherine M. Pringle,Alonso Ramírez,Miguel Cañedo-Argüelles

doi:10.1371/journal.pone.0191781

Pablo E. Gutiérrez-Fonseca, Catherine M. Pringle + Show 2 more

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https://doi.org/10.1371/journal.pone.0191781

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Abstract

Understanding how environmental variables influence the distribution and density of organisms over relatively long temporal scales is a central question in ecology given increased climatic variability (e.g., precipitation, ENSO events). The primary goal of our study was to evaluate long-term (15y time span) patterns of climate, as well as environmental parameters in two Neotropical streams in lowland Costa Rica, to assess potential effects on aquatic macroinvertebrates. We also examined the relative effects of an 8y whole-stream P-enrichment experiment on macroinvertebrate assemblages against the backdrop of this long-term study. Climate, environmental variables and macroinvertebrate samples were measured monthly for 7y and then quarterly for an additional 8y in each stream. Temporal patterns in climatic and environmental variables showed high variability over time, without clear inter-annual or intra-annual patterns. Macroinvertebrate richness and abundance decreased with increasing discharge and was positively related to the number of days since the last high discharge event. Findings show that fluctuations in stream physicochemistry and macroinvertebrate assemblage structure are ultimately the result of large-scale climatic phenomena, such as ENSO events, while the 8y P-enrichment did not appear to affect macroinvertebrates. Our study demonstrates that Neotropical lowland streams are highly dynamic and not as stable as is commonly presumed, with high intra- and inter-annual variability in environmental parameters that change the structure and composition of freshwater macroinvertebrate assemblages.

Highlights

Global climate change is causing organisms to experience new variability in their environments
Long-term ecological data are scarce [11]. This is a serious challenge in Neotropical regions, where there is only one published long-term ecological study of 15y of duration, linking extreme weather events, and their effects on decapod populations [12]. We examine another long-term (15y) data set to investigate the association between temporal variations in climate and stream environmental factors, and how they affect macroinvertebrate structure and composition in two lowland streams in Costa Rica
Most variables fluctuated without showing a significant trend of increasing or decreasing over time (i.e., NH4+, NO3−, Benthic organic matter (BOM), conductivity, pH, precipitation, DSLS, and SOI; all p>0.05)

Summary

Introduction

Global climate change is causing organisms to experience new variability in their environments. In the context of biodiversity research, a long-term dataset is defined as information on the variety and abundance of species (or other taxonomic units) at one or more locations over a considerable period of time [10] It can be delimited as at least 5 years, which is the minimum time needed to interpret a meaningful representative range of conditions, such as climate-driven wet and dry cycles or cool and warm years [11]. This is a serious challenge in Neotropical regions, where there is only one published long-term ecological study of 15y of duration, linking extreme weather events (e.g., hurricanes and drought), and their effects on decapod populations [12] We examine another long-term (15y) data set to investigate the association between temporal variations in climate (i.e., precipitation and ENSO events) and stream environmental factors, and how they affect macroinvertebrate structure and composition in two lowland streams in Costa Rica

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