Research into the ecological implications of microplastic pollution has been accelerating over the last several years, making it easier to overlook the impact of macroplastic in aquatic ecosystems.  Unfortunately, macroplastic pollution remains a growing global environmental concern and our understanding of its interaction with aquatic organisms is underdeveloped. We investigated temporal and spatial patterns of macroinvertebrate colonization on macroplastic litters in contrasting stream hydraulic biotopes (riffle, pool, and run) in headwater streams of Eastern South Africa. Plastic substrates of different proportions of natural and plastic litter were deployed across the four sites in four headwater streams. Substrates included 100% natural substrates (NS), 50% natural material and 50% plastic (NP), and wholly plastic (PD). Each substrate was deployed in riffle, pool, and run habitats for six months at each site. Across hydraulic biotopes, macroinvertebrate colonization of substrate types did not differ significantly (PERMANOVA, p > 0.05). However, the relative proportions of macroinvertebrates in NS were higher in the pool habitats (relative abundance: 40%) than in riffles (relative abundance: 28%). In contrast, macroinvertebrate abundance on PD substrates was highest in riffles (relative abundance: 32%) and lowest in pools (relative abundance: 28%). Macroinvertebrate diversity indices were statistically different across substrate types in pools but not in other habitats (PERMANOVA, p <0.05). Our findings contributed to a better understanding of the macroplastics and biological distribution dynamics in stream ecosystems.

Authors:

Frank Akamagwuna, University of Alabama  (akamagwunafrank@yahoo.com)