Seite - 109 - in Freshwater Microplastics - Emerging Environmental Contaminants?

valuable baseline data forMPs inLakeVictoria, these investigationsmay serve to informhowresearch couldbe conducted in otherAfrican freshwater bodies. 3.2 Plastics in theTanzanianWaters ofLakeVictoria Lake Victoria is the world’s second largest freshwater lake by area (the largest being Lake Superior in NorthAmerica) and has been described as eutrophic and polluted due to human influences within the catchment area [44]. The area sur- rounding the lake is among the most densely populated in the world, and this population growth is set to continue – by the year 2020, an estimated 53million peoplewill inhabit the lake basin [45]. Themajority of economic activities in the region are associatedwith the lakewith oneof themost important beingfishing. Case Study I details the work of Ngupula et al. [16] in which the authors documented presence and distribution of solid waste including plastic bags and fishing gear at six depth strata reaching 80mbelow the surface. Thus,while they didnot specifically look forMPs in thewaters ofLakeVictoria, theworkof these authorsgreatly increasesourunderstandingofwhereMPsoriginatefrominthelake system. In the secondcase studybyBiginagwaet al. [17], the ingestionofMPsby residentfishspecies inLakeVictoriawasused inplaceofenvironmental sampling. The recovery ofMPs from the gastrointestinal tracts of LakeVictoria Nile perch (Lates niloticus) and Nile tilapia (Oreochromis niloticus), and their subsequent characterization, provided the first evidence of MPs within African inland freshwaters. 3.2.1 CaseStudyI:Abundance,Composition,andDistributionofSolid Wastes inLakeVictoria Todetermine the vertical distribution of solidwastes inLakeVictoria, thewaters were categorized into three main ecological zones: (1) the nearshore, which is describedashighlyinfluencedbyanthropogenic inputandwassampledatdepthsof <10mand10.1–20m;(2) the intermediatezonewhichismoderately influencedby thecatchmentandwas sampledatdepthsof20.1–30mand30.1–40m;and (3) the deep offshore waters which are the most isolated from the human activities and weresampledatdepthsof40.1–50mandthen>50.1.ThemaximumdepthofLake Victoria is 80m; thus, this last depth stratum extended to bottom trawls. Across these threezones andsix strata, 68 sampleswere taken in total during twoperiods, May and late September to early October 2013. Trawls were conducted at three knots anddebris collectedby4mmmesh trawl net. Plastic debris was found at all depths and all sampling locations. Across all trawls, the dominant waste types originated fromfishing activities; multifilament gillnetscompromised44%ofalldebris,monofilamentgillnets(42%), longlinesand hooks (7%),andfloats (1%).Plasticbags (4%)andclothing(2%)accountedfor the Microplastics in InlandAfricanWaters: Presence, Sources, andFate 109