Stuck in vegetation: the role of hyacinths in macroplastic debris accumulation in tropical rivers

Water hyacinths are considered one the world’s most invasive aquatic species and are found in most tropical rivers. Hyacinths can form dense patches of several meters of length and width at the water surface and drift due to the combined action of wind and flow velocity. In rivers, hyacinth patches can function as carriers for floating macroplastic debris from rivers into the ocean. In the Saigon river, Vietnam, water hyacinths were found to accumulate a majority of the total floating macroplastic items (Schreyers et al., 2021). Despite their crucial role in macroplastic accumulation and dispersion, precise quantification of both hyacinth coverage and macroplastic concentrations in rivers are currently lacking. We present insights on the accumulation of macroplastics within hyacinth patches based on the analysis of more than 3,000 Unmanned Aerial Vehicle images collected at the Saigon river in 2021. In particular, we explore the relation between hyacinth coverage, patch abundance and floating macroplastic concentrations, and how these vary through time and space. These findings clearly illustrate the complexity of plastic transport in rivers by highlighting its spatiotemporal variability. Our insights can be used for combined clean-up efforts and reduction strategies of both hyacinths and plastic debris in the Saigon river, and support the development of future plastic monitoring strategies in other tropical river systems.   

References

Schreyers, L., van Emmerik, T., Luan Nguyen, T., Castrop, E., Phung, N.-A., Kieu-Le, T.-C., Strady, E., Biermann, L., van der Ploeg, M. (2021). Plastic plants: Water hyacinths as driver of plastic transport in tropical rivers. Frontiers in Environmental Science 10.3389/fenvs.2021.686334