Macroinvertebrate community and leaf litter breakdown measures lack concordance associated with singular or multiple stressors

Ben J Kefford; Andrew J Brooks; Susan J Nichols; Jonathan P Bray

doi:10.1016/j.scitotenv.2024.176082

Macroinvertebrate community and leaf litter breakdown measures lack concordance associated with singular or multiple stressors

Sci Total Environ. 2024 Nov 25:953:176082. doi: 10.1016/j.scitotenv.2024.176082. Epub 2024 Sep 5.

Authors

Ben J Kefford¹, Andrew J Brooks², Susan J Nichols³, Jonathan P Bray⁴

Affiliations

¹ Centre for Applied Water Science, Institute for Applied Ecology, University of Canberra, Canberra, Australia. Electronic address: Ben.kefford@canberra.edu.au.
² Centre for Applied Water Science, Institute for Applied Ecology, University of Canberra, Canberra, Australia; New South Wales Department of Climate Change, Energy, the Environment and Water, PO Box 53, Wollongong, NSW 2500, Australia.
³ Centre for Applied Water Science, Institute for Applied Ecology, University of Canberra, Canberra, Australia.
⁴ Centre for Applied Water Science, Institute for Applied Ecology, University of Canberra, Canberra, Australia; Department of Pest Management and Conservation, Lincoln University, PO Box 85084, Christchurch, Canterbury, New Zealand.

PMID: 39244040
DOI: 10.1016/j.scitotenv.2024.176082

Abstract

Freshwater ecosystems are being degraded by a wide range of stressors resulting from human activities. Various structural and functional metrics or indices are used to assess the 'health' or condition of riverine ecosystems. It is uncertain if structural or functional metrics or indices respond to different stressors and whether some are more responsive to stressors in general. Here we conducted a multi-study synthesis, similar to a meta-analysis, across four independent outdoor mesocosm experiments involving the manipulation of various chemical stressors - two types of salinity (synthetic marine salts (SMS) and sodium bicarbonate), two insecticides (malathion and sulfoxaflor), increased nutrients (N and P), increased sedimentation and two combinations of stressors (1: malathion, nutrients and sedimentation, 2: sulfoxaflor, nutrients and sedimentation). We compare the effects of these singular or multiple stressors on stream macroinvertebrate community structure, and Eucalyptus camaldulensis leaf litter breakdown rates by microbes and total (microbes and invertebrates). Macroinvertebrate communities were adversely affected by the two sets of multiple stressors, SMS, and both insecticides yet, and in contrast to several published studies, both microbial and total leaf litter was unaffected. Nutrients and sodium bicarbonate, increased breakdown rates or had a unimodal 'Ո' shaped response, with maxima at intermediate levels. Sedimentation by fine sand, however, decreased total leaf litter breakdown, while not affecting microbial leaf litter breakdown. Divergent responses between the effects of stressors on leaf litter breakdown rates that we observed and those in the literature may be caused by multiple mechanisms, including differences between communities, functional redundancy and differences in stressor magnitude and interactions with other (unknown) variables.

Keywords: Function vs. structure; Leaf litter breakdown; Major ions; Nutrients; Pesticides; Sedimentation; Stream invertebrates.

MeSH terms

Animals
Ecosystem
Environmental Monitoring*
Invertebrates* / physiology
Plant Leaves*
Rivers* / chemistry
Salinity
Water Pollutants, Chemical / analysis

Substances

Water Pollutants, Chemical