Ecological ramifications of marine debris in mangrove ecosystems: Estimation of substrate coverage and physical effects of marine debris on mangrove ecosystem in Negombo Lagoon, Sri Lanka.

ABSTRACT

The adverse environmental impacts on mangrove ecosystems due to anthropogenic marine debris contamination have attracted public attention not only in Sri Lanka but worldwide. Therefore, quantification of marine debris in sensitive ecosystems like mangroves is critical to assess the impacts on ecosystem vitality and services. We conducted this study to assess the abundance and density of marine debris in Negombo lagoon, Western Province, Sri Lanka. We selected two sites (n = 2) using the purposive sampling technique. Marine debris cover and concentration were calculated to explore the extent of pollution from marine debris. The findings revealed that 9.83 ± 1.05 % of the substrate of the mangrove ecosystem is covered by debris. Nine types of marine debris were recorded, and a higher abundance belonged to single-use plastic items. A significantly higher debris cover was found in Kadolkele (18.80 ± 1.74 %, n = 120) than in Molekadolwetiya (0.85 ± 0.03 %, n = 120) (One-way ANOVA, p < 0.05). The study indicated that the mangroves in lagoon are highly polluted with marine debris and act as "litter catchers." Correlation coefficient analysis was used to find the impact of debris cover on physical damage to roots, seedlings, and undergrowth vegetation. Correlation analysis revealed that physical damage to seedlings and branches/barks have a positive correlation with debris cover. To conserve these valuable coastal habitats in Negombo lagoon, it is recommended to take remedial measures to reduce arriving debris loads and to remove the debris present in mangroves.