Effects of Microplastics on Kandelia obovata: Investigating Stress and Responses for Conservation and Management

Mangrove resilience to anoxic conditions primarily occurs through adaptations in their root systems. Notably, increased root growth of existing pneumatophores in response to plastic suffocation has been observed in mangroves and can serve as a proxy to assess tree stress. The objective of this study is to determine the impact of varying levels of microplastic pollution on the morphological characteristics of mangrove plants. Fresh Kandelia obovata seedlings were collected from the Cotai Ecological Reserve, cultivated for 27 weeks, and subsequently exposed to polyethylene (PE) particles of 600 μm, 150 μm, and 13 μm in size at concentrations of 5% and 10% (w/w). The wet weight of the plant samples was measured at the beginning and end of the experiment, and morphological characteristics were recorded weekly. Morphological parameters including germination rate, number of leaves, root morphology, and survival rate, as well as environmental conditions (temperature and humidity), were evaluated to determine the influence of microplastic size, concentration, and environmental factors on plant development. Results indicate that smaller microplastics (13 μm) adversely affected the germination rate, leaf production, and survival of K. obovata. Furthermore, a higher concentration (10% w/w) of medium-sized microplastics (150 μm) led to a lower survival rate compared to the lower concentration group. These findings shows the negative impact of microplastic pollution on mangrove species and highlight the importance of addressing plastic contamination for effective mangrove conservation.