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Monthly sampling reveals seasonal fine sediment fluctuations and riverine invertebrate community responses

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posted on 2023-11-27, 14:26 authored by Noah G Davis, Kate MathersKate Mathers, Roger Hodson, Christoph D Matthaei

Managing the impacts of anthropogenically enhanced deposited fine sediment levels in lotic ecosystems requires understanding of how catchment land-use changes have altered the natural sediment regime (erosion, transport, deposition) of rivers. Unfortunately, no existing studies have employed an appropriate sampling frequency over a period encompassing the full range of seasonal flow conditions expected to influence in-stream sediment dynamics. We determined the short-term (monthly) dynamics of deposited fine sediment and invertebrate communities over 12-months in 15 fourth- and fifth-order rivers draining catchments of low, medium and high land-use intensity in Southland, New Zealand to determine when and where fine sediment threatens stream health. We compared the Quorer resuspension method (suspendable inorganic sediment, SIS) and the in-stream visual sediment cover assessment method, and evaluated the effectiveness of four commonly-used invertebrate stream health metrics against their newly developed sediment-specific counterparts. Monthly variability in SIS was substantial across all land-use categories, but became more pronounced as land-use intensity increased. All 15 sites experienced a prolonged period of relatively stable flow which coincided with the largest short-term increase in SIS at 14 of the 15 sites. However, variability in SIS was not mirrored in macroinvertebrate metrics. These findings suggest that controlling inputs of fine sediment to rivers and streams will be most effective when targeted at periods of prolonged stable flow, particularly within high land-use intensity catchments. The resuspension method consistently outperformed visual estimates when considering its relationship with macroinvertebrate metrics, while sediment-specific metrics demonstrated a stronger association with fine sediment than commonly employed metrics e.g. (%EPT). We conclude that restoration/mitigation practices cannot be based solely on short-term, or even long-term, reductions in fine sediment, or on physical measures alone, but should be based on long-term recoveries of sediment-impacted invertebrate communities using concurrent measurements of both biotic and abiotic conditions. 

Funding

Stuck in the mud: addressing the fine sediment conundrum with multiscale and interdisciplinary approaches to support global freshwater biodiversity

UK Research and Innovation

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Environment Southland

History

School

  • Social Sciences and Humanities

Department

  • Geography and Environment

Published in

Science of The Total Environment

Volume

911

Issue

2024

Publisher

Elsevier

Version

  • VoR (Version of Record)

Rights holder

© The Authors

Publisher statement

This is an Open Access Article. It is published by Elsevier under the Creative Commons Attribution 4.0 International Licence (CC BY). Full details of this licence are available at: http://creativecommons.org/licenses/by/4.0/

Acceptance date

2023-11-19

Publication date

2023-11-21

Copyright date

2023

ISSN

0048-9697

eISSN

1879-1026

Language

  • en

Depositor

Dr Kate Mathers. Deposit date: 25 November 2023

Article number

168750

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