(131a) The Presence of Waste Plastics and Microplastics in Lakes and Rivers, and Their Impact on the Marine Environment

Waste plastics (>5 mm) and microplastics are tiny pieces of plastics (<5 mm) that have been manufactured, shed from textiles or formed as degradation products of macroplastics. These materials can be taken up by aquatic organisms, which can be uptaken and incorporated into the food chain. Humans can consume microplastics from fish as well as other impacted sources such as bottled water and tap water. Microplastics can pose risks to marine organisms, and also act as vectors carrying additional adsorbed chemical pollutants and pathogens. Microplastics pose significant risks to the biota and fauna.

This presentation describes the presence and impacts of waste plastics and microplastics in freshwater systems such as lakes and rivers. Microplastics are ubiquitous worldwide in surface waters. Microplastics and waste plastics have been detected virtually everywhere on earth. For example, microplastics have been detected in China, Brazil, Tanzania, the Great Lakes in the U.S., Spain, Argentina, Italy, Mongolia, and Canada. Microplastics have even been detected in remote mountain lakes.

Global rivers and effluents act as a dominant transport pathway for land-based plastic debris for the marine environment. This is particularly true for urban environments. Combined sewer overflows likely contribute likely contribute additional plastic loads during high-flow conditions. Waste plastics can degrade due to the mechanical degradation by wave action and sand abrasion.

It is estimated that more than 1,000 rivers account for more than 80% of global annual emissions into the oceans ranging from 0.8 million to 2.7 million tons per year, with smaller urban rivers among the most polluting rivers. The plastics can remain in the aquatic environment for years, decades, and potentially centuries. Hydrometeorological variables such as wind, runoff, and river discharge, mobilize, transport, and deposit plastics in different river components (e.g., riverbanks, floodplains, lakes, and estuaries); these conditions are especially impacted by storms and floods. Flooding conditions exacerbate the concentration of microplastics in rivers globally. Additionally, microplastics can impact marine species in rivers; Nile tilapia and catfish have microplastics detected in their gastrointestinal tracts, present as fibers and films. Plastics detected include polyethylene, polypropylene, and polyethylene terephthalate. Water birds are also impacted by microplastics.

This technical presentation will summarize results of various research studies related to microplastics present in the oceans and rivers, and their impacts on the ecosystem and fauna.