Are tropical estuaries a source of or a sink for marine litter? Evidence from Sabaki Estuary, Kenya.

Litter surveys were carried out in August and September 2020 to determine the contribution of Sabaki River and estuary in modifying the quantities of litter entering the oceans. The river discharged 0.035 items m-3s -1 translating to an estimated annual litter flux of between 6,622,560 and 614,952,000. The surveys in the estuary revealed that plastics contributed 90.8% of the total litter. Wet and dry zones had mean litter accumulation rates of 2.7 ± 1.1 and 4.4 ± 3.5 items m-1 day-1 respectively. 69.8% and 77.4% of branded litter were of Kenyan origin and food packaging material respectively. The litter turnover was slightly higher in the dry beach zone compared to the wet zone with a Whitakker Beta diversity of 0.36 and 0.33 respectively. Sabaki estuary acted as a sink for litter during flooding (through burial) and as a source (through exposure of buried litter due to wind and rain action).

The influence of monsoons on the spatial distribution and composition of floating marine litter.

Floating marine litter (FML) surveys were conducted in the near shore waters of Mombasa, Kilifi and Kwale Counties of Kenya through trawling using a manta net. A mean density of 26,665 ± 2869 items km-2 composed of 34.8% hard plastic, 40.5% soft plastics and 22.0% plastic lines/fibers was reported in this study. Litter densities in Kwale, Kilifi and Mombasa Counties were not influenced by monsoons, however, litter composition was influenced by monsoons with NEM and SEM being dominated mainly by hard plastics and soft plastics respectively. Litter categories diversity, evenness and richness were also not influenced by the monsoons during both NEM (1.01, 0.78 and 3, respectively) and SEM (1.09, 0.78 and 4, respectively). Fishing and recreational beaches had higher litter densities during NEM compared to SEM attributed to higher beach visitation and increased fishing activities during the calmer NEM season.

Temporal trends of marine litter in a tropical recreational beach: A case study of Mkomani beach, Kenya.

Six marine litter standing stock surveys were carried out to determine the influence of monsoon on the temporal abundance and composition of macro-litter in Mkomani beach, Mombasa Kenya. Foam (0.073 items m-2) and plastic (0.042 items m-2) fragments had the highest densities. The brand audit indicated that 66.9% of branded marine litter was of Kenyan origin. Food product packaging contributed 78.4% of the branded litter with PET bottles being the most abundant type of packaging (48.2%). Foreign products contributed 35.6% of branded marine litter during South East Monsoon (SEM) whereas only 11.7% during North-East Monsoon (NEM). Worth noting, PET packaging dominated during SEM (53.6%) compared to NEM (20.2%). Mkomani beach could be considered "extremely dirty" with a Clean-Coast Index greater than 20. The study concludes that monsoons influences litter diversity, richness and evenness.

The impacts of COVID-19 pandemic on marine litter pollution along the Kenyan Coast: A synthesis after 100 days following the first reported case in Kenya.

The contribution of COVID-19 pandemic to marine litter pollution was studied in Mombasa, Kilifi, and Kwale counties of Kenya, in June 2020 (100 days following the first confirmed case in Kenya). Standing stock surveys were conducted in 14 streets and 21 beaches while 157 transects were surveyed for floating litter. COVID-19 related items contributed up to 16.5% of the total litter encountered along the streets. The urban beaches (Mkomani and Nyali) had the highest quantities of COVID-19 related items (55.1% and 2.6% respectively) attributable to the ability to purchase single-use products and lifestyle. Most of the recreational beaches had no COVID-19 related products which could be attributed to the presidential directive on beach closure as a COVID-19 contingency measure. No COVID-19 related litter was found in the floating litter. Generally, beach closure and cessation of movement reduced the amount of litter that leaked to the marine environment.

Marine macro-litter composition and distribution along the Kenyan Coast: The first-ever documented study.

Macro-litter accumulation surveys were carried out in six beaches in Kilifi, Mombasa and Kwale Counties. Macro litter were collected, quantified and characterized to determine their composition, distribution and accumulation rates. The results showed that the accumulation rates ranged between 1.53 ± 1.23 and 11.46 ± 7.72 (for dry zones) and 2.69 ± 2.13 and 8.93 ± 7.87 items m-1 day-1 (for wet zones). Plastics and foam were the most abundant litter categories. Local products constituted about 88% of all the collected litter. Food packaging products constituted about 91.3% of all branded litter types. Marine litter pollution particularly by plastics was widespread in all studied coastal counties. However, a significant amount of litter encountered in the beaches was of local origin, thus a local solution to waste management (that will eliminate leakage into marine environments) will considerably reduce marine litter pollution in Kenya.