Effects of pollution-induced changes in oxygen conditions scaling up from individuals to ecosystems in a tropical river network

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  • Tor Erik Eriksen
  • Jacobsen, Dean
  • Benoît O. L. Demars
  • John E. Brittain
  • Geir Søli
  • Nikolai Friberg

Anthropogenic inputs of nutrients and organic matter are common in tropical lowland rivers while little is known about the pollution-induced changes in oxygen availability and respiratory performance of ectotherms in these high temperature systems. We investigated the effects of agriculture and urban land-use on river water oxygen levels (diel measurements), decomposition rates (Wettex) and macroinvertebrate assemblages (field studies), as well as the oxy-regulatory capacity of eight riverine macroinvertebrate taxa (laboratory study) from a tropical lowland river network in Myanmar. The highest decomposition rates (0.1–5.5 mg Wettex degree day−1) and oxygen stress (≤91% saturation deficits) were found in reaches draining degraded catchments with elevated concentrations of nutrients. All individual macroinvertebrate taxa investigated were to some extent able to regulate their respiration when placed under oxygen stress in the laboratory (regulation value of 0.74–0.89). The oxy-regulation capacity of macroinvertebrate assemblages in the river network were, as predicted, inversely related to diel oxygen stress (maximum deficit; lm, R2 = 0.69), where taxonomic richness and pollution sensitivity (ASPT metric) also declined sharply (lm, R2 ≥ 0.79). Our study shows that eutrophication and organic pollution induce oxygen deficits in tropical rivers but stimulate decomposition rates, which may further deplete oxygen levels. Furthermore, macroinvertebrate oxy-regulatory capacity predicts assemblage composition along gradients in oxygen stress at the ecosystem level. Our findings suggest that tropical lowland river systems could be highly sensitive to pollution by nutrients and organic matter leading to substantial impacts on ectotherm community composition and ecosystem functioning.

OriginalsprogEngelsk
Artikelnummer151958
TidsskriftScience of the Total Environment
Vol/bind814
Antal sider11
ISSN0048-9697
DOI
StatusUdgivet - 2022

Bibliografisk note

Funding Information:
This work was supported by the Royal Norwegian Embassy in Myanmar/Norwegian Ministry of Foreign Affairs and the Norwegian Institute for Water Research (NIVA). The study was a component of a larger collaborative project (The integrated water resources management – institutional building and training) with Department of Forestry (FD), Ministry of Natural Resources and Environmental Conservation (MONREC) of Myanmar and NIVA. We thank Bo Ni, retired director of Watershed Management Division (FD), Zaw Win Myint – the director of Watershed Management Division (FD), Ko Ko Oo (Irrigation and Water Utilization Management Department; IWUMD), Htay Aung (Directorate of Water Resources and Improvement of River Systems; DWIR), Toe Aung (FD) and Ingrid Nesheim (NIVA) for providing facilities and personnel to assist our work. A special acknowledgement is given to Eirin Årstein-Eriksen (NIVA), Johnny Håll (NIVA), Mathias Brink Kjeldgaard and the monitoring sampling team in Myanmar for valuable assistance during the studies, including Phyo Wai (IWUMD), Phyo Thet Naing (FD), Phyo Thet (FD), Mya Htet Aung (IWUMD), Thet Myat (FD), Htay Kywe (IWUMD), Zao Myo (FD), Phyo Thet (FD), Swuam Pyaye Aye Aung (FD), Eai Chit Thu Maung (FD) and Mr. Moe (FD).

Funding Information:
This work was supported by the Royal Norwegian Embassy in Myanmar/Norwegian Ministry of Foreign Affairs and the Norwegian Institute for Water Research (NIVA). The study was a component of a larger collaborative project (The integrated water resources management ? institutional building and training) with Department of Forestry (FD), Ministry of Natural Resources and Environmental Conservation (MONREC) of Myanmar and NIVA. We thank Bo Ni, retired director of Watershed Management Division (FD), Zaw Win Myint ? the director of Watershed Management Division (FD), Ko Ko Oo (Irrigation and Water Utilization Management Department; IWUMD), Htay Aung (Directorate of Water Resources and Improvement of River Systems; DWIR), Toe Aung (FD) and Ingrid Nesheim (NIVA) for providing facilities and personnel to assist our work. A special acknowledgement is given to Eirin ?rstein-Eriksen (NIVA), Johnny H?ll (NIVA), Mathias Brink Kjeldgaard and the monitoring sampling team in Myanmar for valuable assistance during the studies, including Phyo Wai (IWUMD), Phyo Thet Naing (FD), Phyo Thet (FD), Mya Htet Aung (IWUMD), Thet Myat (FD), Htay Kywe (IWUMD), Zao Myo (FD), Phyo Thet (FD), Swuam Pyaye Aye Aung (FD), Eai Chit Thu Maung (FD) and Mr. Moe (FD).

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