The past decades have seen a decline in global mangrove coverage[1]. This is due to both natural and anthropogenic factors including natural disasters, overexploitation, and unsustainable development[2]. More recently, waste has also become an emerging threat with plastic waste found to be the dominant type of waste in mangrove ecosystems[3]. Some of the characteristics that make the mangrove ecosystem unique are also the ones that make it particularly vulnerable to plastics.
The location of mangrove forests plays a factor in determining its exposure to plastic waste. Landward-facing mangroves have been shown to trap more debris than those facing the sea due to proximity to human dwellings where plastic waste is produced.[3],[4],[5]. Furthermore, rivers are known to be notable contributors of plastic waste to oceans[6],[7] and 54% of mangrove habitat is located within 20 km of some of the most plastic-polluting rivers[8]. Factors such as hydrodynamics, vegetation height and density within the ecosystem also contribute to the degree of plastic waste retention in mangrove ecosystems [6].
A notable physical feature in several species of mangrove plants is their expansive and above-ground roots which were developed to weather tides and waves as well as adapt to the mostly anaerobic, inundated, and saline conditions in their surrounding environment[9],[10]. However, these same features also make it easy for plastic waste to get entangled between the plants [14]. These special roots also promote sedimentation[17],[11] burying microplastics suspended in the seawater in the process[12].
As mentioned before, mangrove plants are just one component of the mangrove ecosystem. Thus, plastic pollution that enters mangrove ecosystems causes negative impacts not just to the mangrove plants, but also to other components of the mangrove ecosystem.
The characteristics of the plastic waste also affect their entrapment in mangrove ecosystems. Polymer density and shape were found to affect the movement and retention of macroplastics in mangrove forests [6]. For instance, plastic bags tend to have higher retention compared to bottles and margarine tubs [6]. The resemblance of microplastics of certain shapes, sizes, and color to natural prey make them more likely to be ingested by animals[20],[21]. The attachment of organisms on the surface of plastic waste, also known as biofouling, increases the density of plastics, making it easier for them to sink and get trapped in mangrove sediment [21], [22].
[1] FAO. (2007). The world’s mangroves 1980-2005: A thematic study prepared in the framework of the Global Forest Resources Assessment 2005 (Vol. 153, Ser. FAO Forestry Paper). Food and Agriculture Organization of the United Nations. https://www.fao.org/3/a1427e/a1427e00.pdf
[2] Ashton, E.C. (2022). Threats to mangroves and conservation strategies. In Das, S.C., Pullaiah, & Ashton, E.C. (Eds.), Mangroves: Biodiversity, livelihoods and conservation. Springer. https://doi.org/10.1007/978-981-19-0519-3_10
[3] Luo, Y. Y., Vorsatz, L. D., Not, C., & Cannicci, S. (2022). Landward zones of mangroves are sinks for both land and water borne anthropogenic debris. Science of The Total Environment, 818, 1–10. https://doi.org/10.1016/j.scitotenv.2021.151809
[4] Cappa, P., Walton, M. E. M., Paler, M. K., Taboada, E. B., Hiddink, J. G., & Skov, M. W. (2023). Impact of mangrove forest structure and landscape on macroplastics capture. Marine Pollution Bulletin, 194, 1–7. https://doi.org/10.1016/j.marpolbul.2023.115434
[5] Suyadi, & Manullang, C. Y. (2020). Distribution of plastic debris pollution and it is implications on Mangrove vegetation. Marine Pollution Bulletin, 160, 1–8. https://doi.org/10.1016/j.marpolbul.2020.111642
[6] Lebreton, L. C., van der Zwet, J., Damsteeg, J.-W., Slat, B., Andrady, A., & Reisser, J. (2017). River plastic emissions to the world’s oceans. Nature Communications, 8(1). https://doi.org/10.1038/ncomms15611
[7] Meijer, L. J., van Emmerik, T., van der Ent, R., Schmidt, C., & Lebreton, L. (2021). More than 1000 rivers account for 80% of global riverine plastic emissions into the Ocean. Science Advances, 7(18). https://doi.org/10.1126/sciadv.aaz5803
[8] Harris, P. T., Westerveld, L., Nyberg, B., Maes, T., Macmillan-Lawler, M., & Appelquist, L. R. (2021). Exposure of coastal environments to river-sourced plastic pollution. Science of The Total Environment, 769, 145222. https://doi.org/10.1016/j.scitotenv.2021.145222
[9] Spalding, M. (2010). World Atlas of Mangroves. Routledge. https://doi.org/10.4324/9781849776608
[10] Srikanth, S., Lum, S. K., & Chen, Z. (2015). Mangrove root: Adaptations and ecological importance. Trees, 30(2), 451–465. https://doi.org/10.1007/s00468-015-1233-0
[11] Martin, C., Almahasheer, H., & Duarte, C. M. (2019). Mangrove forests as traps for marine litter. Environmental Pollution, 247, 499–508. https://doi.org/10.1016/j.envpol.2019.01.067
[12] Martin, C., Baalkhuyur, F., Valluzzi, L., Saderne, V., Cusack, M., Almahasheer, H., Krishnakumar, P. K., Rabaoui, L., Qurban, M. A., Arias-Ortiz, A., Masqué, P., & Duarte, C. M. (2020). Exponential increase of plastic burial in mangrove sediments as a major plastic sink. Science Advances, 6(44). https://doi.org/10.1126/sciadv.aaz5593
[13] van Bijsterveldt, C. E. J., van Wesenbeeck, B. K., Ramadhani, S., Raven, O. V., van Gool, F. E., Pribadi, R., & Bouma, T. J. (2021). Does plastic waste kill mangroves? A field experiment to assess the impact of macro plastics on mangrove growth, stress response and survival. Science of The Total Environment, 756, 1–11. https://doi.org/10.1016/j.scitotenv.2020.143826
[14] Sandilyan, S. & Kathiresan, K. (2012). Plastics – a formidable threat to unique biodiversity of Pichavaram mangroves. Current Science, 103(11), 1262–1263.
[15] Ivar do Sul, J. A., Costa, M. F., Silva-Cavalcanti, J. S., & Araújo, M. C. (2014). Plastic debris retention and exportation by a mangrove forest patch. Marine Pollution Bulletin, 78(1–2), 252–257. https://doi.org/10.1016/j.marpolbul.2013.11.011
[16] Bulow, E. S. & Ferdinand, T. J. (2013). The effect of consumptive waste on mangrove functionality: A comparative analysis. Centro de Incidencia Ambiental.
[17] Riascos, J. M., Valencia, N., Peña, E. J., & Cantera, J. R. (2019). Inhabiting the technosphere: The encroachment of anthropogenic marine litter in Neotropical mangrove forests and its use as habitat by macrobenthic biota. Marine Pollution Bulletin, 142, 559–568. https://doi.org/10.1016/j.marpolbul.2019.04.010
[18] Anbumani, S., & Kakkar, P. (2018). Ecotoxicological effects of microplastics on biota: A Review. Environmental Science and Pollution Research, 25(15), 14373–14396. https://doi.org/10.1007/s11356-018-1999-x
[19] Guo, X., & Wang, J. (2019). The chemical behaviors of microplastics in marine environment: A Review. Marine Pollution Bulletin, 142, 1–14. https://doi.org/10.1016/j.marpolbul.2019.03.019
[20] Chen, B. (2022). Current status and trends of research on microplastic fugacity characteristics and pollution levels in mangrove wetlands. Frontiers in Environmental Science, 10. https://doi.org/10.3389/fenvs.2022.1021274
[21] Maghsodian, Z., Sanati, A. M., Ramavandi, B., Ghasemi, A., & Sorial, G. A. (2021). Microplastics accumulation in sediments and periophthalmus waltoni fish, mangrove forests in southern Iran. Chemosphere, 264. https://doi.org/10.1016/j.chemosphere.2020.128543
[22] Kooi, M., Nes, E. H., Scheffer, M., & Koelmans, A. A. (2017). Ups and downs in the ocean: Effects of biofouling on vertical transport of Microplastics. Environmental Science & Technology, 51(14), 7963–7971. https://doi.org/10.1021/acs.est.6b04702
The past decades have seen a decline in global mangrove coverage[1]. This is due to both natural and anthropogenic factors including natural disasters, overexploitation, and unsustainable development[2]. More recently, waste has also become an emerging threat with plastic waste found to be the dominant type of waste in mangrove ecosystems[3]. Some of the characteristics that make the mangrove ecosystem unique are also the ones that make it particularly vulnerable to plastics.
The location of mangrove forests plays a factor in determining its exposure to plastic waste. Landward-facing mangroves have been shown to trap more debris than those facing the sea due to proximity to human dwellings where plastic waste is produced.[3],[4],[5]. Furthermore, rivers are known to be notable contributors of plastic waste to oceans[6],[7] and 54% of mangrove habitat is located within 20 km of some of the most plastic-polluting rivers[8]. Factors such as hydrodynamics, vegetation height and density within the ecosystem also contribute to the degree of plastic waste retention in mangrove ecosystems [6].
A notable physical feature in several species of mangrove plants is their expansive and above-ground roots which were developed to weather tides and waves as well as adapt to the mostly anaerobic, inundated, and saline conditions in their surrounding environment[9],[10]. However, these same features also make it easy for plastic waste to get entangled between the plants [14]. These special roots also promote sedimentation[17],[11] burying microplastics suspended in the seawater in the process[12].
As mentioned before, mangrove plants are just one component of the mangrove ecosystem. Thus, plastic pollution that enters mangrove ecosystems causes negative impacts not just to the mangrove plants, but also to other components of the mangrove ecosystem.
The characteristics of the plastic waste also affect their entrapment in mangrove ecosystems. Polymer density and shape were found to affect the movement and retention of macroplastics in mangrove forests [6]. For instance, plastic bags tend to have higher retention compared to bottles and margarine tubs [6]. The resemblance of microplastics of certain shapes, sizes, and color to natural prey make them more likely to be ingested by animals[20],[21]. The attachment of organisms on the surface of plastic waste, also known as biofouling, increases the density of plastics, making it easier for them to sink and get trapped in mangrove sediment [21], [22].
[1] FAO. (2007). The world’s mangroves 1980-2005: A thematic study prepared in the framework of the Global Forest Resources Assessment 2005 (Vol. 153, Ser. FAO Forestry Paper). Food and Agriculture Organization of the United Nations. https://www.fao.org/3/a1427e/a1427e00.pdf
[2] Ashton, E.C. (2022). Threats to mangroves and conservation strategies. In Das, S.C., Pullaiah, & Ashton, E.C. (Eds.), Mangroves: Biodiversity, livelihoods and conservation. Springer. https://doi.org/10.1007/978-981-19-0519-3_10
[3] Luo, Y. Y., Vorsatz, L. D., Not, C., & Cannicci, S. (2022). Landward zones of mangroves are sinks for both land and water borne anthropogenic debris. Science of The Total Environment, 818, 1–10. https://doi.org/10.1016/j.scitotenv.2021.151809
[4] Cappa, P., Walton, M. E. M., Paler, M. K., Taboada, E. B., Hiddink, J. G., & Skov, M. W. (2023). Impact of mangrove forest structure and landscape on macroplastics capture. Marine Pollution Bulletin, 194, 1–7. https://doi.org/10.1016/j.marpolbul.2023.115434
[5] Suyadi, & Manullang, C. Y. (2020). Distribution of plastic debris pollution and it is implications on Mangrove vegetation. Marine Pollution Bulletin, 160, 1–8. https://doi.org/10.1016/j.marpolbul.2020.111642
[6] Lebreton, L. C., van der Zwet, J., Damsteeg, J.-W., Slat, B., Andrady, A., & Reisser, J. (2017). River plastic emissions to the world’s oceans. Nature Communications, 8(1). https://doi.org/10.1038/ncomms15611
[7] Meijer, L. J., van Emmerik, T., van der Ent, R., Schmidt, C., & Lebreton, L. (2021). More than 1000 rivers account for 80% of global riverine plastic emissions into the Ocean. Science Advances, 7(18). https://doi.org/10.1126/sciadv.aaz5803
[8] Harris, P. T., Westerveld, L., Nyberg, B., Maes, T., Macmillan-Lawler, M., & Appelquist, L. R. (2021). Exposure of coastal environments to river-sourced plastic pollution. Science of The Total Environment, 769, 145222. https://doi.org/10.1016/j.scitotenv.2021.145222
[9] Spalding, M. (2010). World Atlas of Mangroves. Routledge. https://doi.org/10.4324/9781849776608
[10] Srikanth, S., Lum, S. K., & Chen, Z. (2015). Mangrove root: Adaptations and ecological importance. Trees, 30(2), 451–465. https://doi.org/10.1007/s00468-015-1233-0
[11] Martin, C., Almahasheer, H., & Duarte, C. M. (2019). Mangrove forests as traps for marine litter. Environmental Pollution, 247, 499–508. https://doi.org/10.1016/j.envpol.2019.01.067
[12] Martin, C., Baalkhuyur, F., Valluzzi, L., Saderne, V., Cusack, M., Almahasheer, H., Krishnakumar, P. K., Rabaoui, L., Qurban, M. A., Arias-Ortiz, A., Masqué, P., & Duarte, C. M. (2020). Exponential increase of plastic burial in mangrove sediments as a major plastic sink. Science Advances, 6(44). https://doi.org/10.1126/sciadv.aaz5593
[13] van Bijsterveldt, C. E. J., van Wesenbeeck, B. K., Ramadhani, S., Raven, O. V., van Gool, F. E., Pribadi, R., & Bouma, T. J. (2021). Does plastic waste kill mangroves? A field experiment to assess the impact of macro plastics on mangrove growth, stress response and survival. Science of The Total Environment, 756, 1–11. https://doi.org/10.1016/j.scitotenv.2020.143826
[14] Sandilyan, S. & Kathiresan, K. (2012). Plastics – a formidable threat to unique biodiversity of Pichavaram mangroves. Current Science, 103(11), 1262–1263.
[15] Ivar do Sul, J. A., Costa, M. F., Silva-Cavalcanti, J. S., & Araújo, M. C. (2014). Plastic debris retention and exportation by a mangrove forest patch. Marine Pollution Bulletin, 78(1–2), 252–257. https://doi.org/10.1016/j.marpolbul.2013.11.011
[16] Bulow, E. S. & Ferdinand, T. J. (2013). The effect of consumptive waste on mangrove functionality: A comparative analysis. Centro de Incidencia Ambiental.
[17] Riascos, J. M., Valencia, N., Peña, E. J., & Cantera, J. R. (2019). Inhabiting the technosphere: The encroachment of anthropogenic marine litter in Neotropical mangrove forests and its use as habitat by macrobenthic biota. Marine Pollution Bulletin, 142, 559–568. https://doi.org/10.1016/j.marpolbul.2019.04.010
[18] Anbumani, S., & Kakkar, P. (2018). Ecotoxicological effects of microplastics on biota: A Review. Environmental Science and Pollution Research, 25(15), 14373–14396. https://doi.org/10.1007/s11356-018-1999-x
[19] Guo, X., & Wang, J. (2019). The chemical behaviors of microplastics in marine environment: A Review. Marine Pollution Bulletin, 142, 1–14. https://doi.org/10.1016/j.marpolbul.2019.03.019
[20] Chen, B. (2022). Current status and trends of research on microplastic fugacity characteristics and pollution levels in mangrove wetlands. Frontiers in Environmental Science, 10. https://doi.org/10.3389/fenvs.2022.1021274
[21] Maghsodian, Z., Sanati, A. M., Ramavandi, B., Ghasemi, A., & Sorial, G. A. (2021). Microplastics accumulation in sediments and periophthalmus waltoni fish, mangrove forests in southern Iran. Chemosphere, 264. https://doi.org/10.1016/j.chemosphere.2020.128543
[22] Kooi, M., Nes, E. H., Scheffer, M., & Koelmans, A. A. (2017). Ups and downs in the ocean: Effects of biofouling on vertical transport of Microplastics. Environmental Science & Technology, 51(14), 7963–7971. https://doi.org/10.1021/acs.est.6b04702
