Does plastic waste kill mangroves? A field experiment to assess the impact of macro plastics on mangrove growth, stress response and survival
van Bijsterveldt, Celine E.J.; van Wesenbeeck, Bregje K.; Ramadhani, Sri; Raven, Olivier V.; van Gool, Fleur E.; Pribadi, Rudhi; Bouma, Tjeerd J.
(2021) Science of the Total Environment, volume 756, pp. 1 - 11
(Article)
Abstract
The value of mangroves has been widely acknowledged, but mangrove forests continue to decline due to numerous anthropogenic stressors. The impact of plastic waste is however poorly known, even though the amount of plastic litter is the largest in the region where mangroves are declining the fastest: South East Asia.
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In this study, we examine the extent of the plastic waste problem in mangroves along the north coast of Java, Indonesia. First, we investigate how much of the forest floor is covered by plastic in the field (in number of items per m2 and in percentage of the forest floor covered by plastic), and if plastic is also buried in the upper layers of the sediment. We then experimentally investigate the effects of a range of plastic cover percentages (0%, 50% and 100%) on root growth, stress response of the tree and tree survival over a period of six weeks. Field monitoring showed that plastic was abundant, with 27 plastic items per m2 on average, covering up to 50% of the forest floor at multiple locations. Moreover, core data revealed that plastic was frequently buried in the upper layers of the sediment where it becomes immobile and can create prolonged anoxic conditions. Our experiment subsequently revealed that prolonged suffocation by plastic caused immediate pneumatophore growth and potential leaf loss. However, trees in the 50%-plastic cover treatment proved surprisingly resilient and were able to maintain their canopy over the course of the experiment, whereas trees in the 100%-plastic cover treatment had a significantly decreased leaf area index and survival by the end of the experiment. Our findings demonstrate that mangrove trees are relatively resilient to partial burial by plastic waste. However, mangrove stands are likely to deteriorate eventually if plastic continues to accumulate.
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Keywords: Anoxia, Macro plastics, Mangroves, Pneumatophores, Stress response, Environmental Engineering, Environmental Chemistry, Waste Management and Disposal, Pollution
ISSN: 0048-9697
Publisher: Elsevier bedrijfsinformatie b.v.
Note: Funding Information: This work is part of the BioManCO project with project number 14753 , which is (partly) financed by NWO Domain Applied and Engineering Sciences , and co-financed by Boskalis Dredging and Marine experts, Van Oord Dredging and Marine Contractors bv , Deltares , Witteveen+Bos and Wetlands International . The BioManCO project is a collaboration between TU Delft, NIOZ and UNDIP and makes use of the framework set up by Building with Nature Indonesia, a program by Ecoshape, Wetlands International, the Indonesian Ministry of Marine Affairs and Fisheries (MMAF), the Indonesian Ministry of Public Works and Housing (PU) and other partners. Funding Information: The authors would like to thank Silke Tas and Alejandra Gij?n Manche?o and the wider BioManCo team for the fruitful brainstorm sessions and critical feedback. Anneliese Suryaningtyas and Alifiansyah Deto Rahmana Putra for their efforts in preliminary experimental set-ups. We are grateful for the beautiful drone image created by Faiz Hamza Adriano who flew the drone at the study site and Lennart van IJzerloo for the post processing. In addition, we would like to thank Co-REM UNDIP, and in particular Muhammad Helmi and Aris Ismanto for facilitating the research project in Indonesia. Last but not least, we would like to thank Eko Budi Priyanto and Kuswantoro from Wetlands International and the local fishermen Bapak Slamet and Bapak Nur and their family for facilitating our work in the field. This work is part of the BioManCO project with project number 14753, which is (partly) financed by NWO Domain Applied and Engineering Sciences, and co-financed by Boskalis Dredging and Marine experts, Van Oord Dredging and Marine Contractors bv, Deltares, Witteveen+Bos and Wetlands International. The BioManCO project is a collaboration between TU Delft, NIOZ and UNDIP and makes use of the framework set up by Building with Nature Indonesia, a program by Ecoshape, Wetlands International, the Indonesian Ministry of Marine Affairs and Fisheries (MMAF), the Indonesian Ministry of Public Works and Housing (PU) and other partners. Publisher Copyright: © 2020 The Authors
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