Macro and Micro Litter Accumulation in the San Marcos River San Marcos, Texas, USA




Johnson, Haley

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Litter accumulation in rivers is understudied in the United States and yet is a major problem that is becoming worse. Litter is the focus of recent management attention in urban river systems including the San Marcos River. The San Marcos River is primarily spring-fed by the Edwards Aquifer and provides habitat to seven federally-listed species, some of which are only found within the first few kilometers of the main stem. Thousands of tourists recreate on the San Marcos River during the late spring and summer, and these numbers increase every year. Additionally, San Marcos is in Flash Flood Alley, contributing to large amounts of runoff. Understanding the scope of litter pollution can assist with mitigation tactics that focus on source reduction of pollution. This study investigates litter accumulation in the first eight kilometers of the main stem of the San Marcos River, with a specific focus on the history of the problem and community efforts to clean-up the river. Emphasis is placed on recreation and tourism sources, runoff-based culvert sources, and microplastic accumulation in bed substrates. My research uses existing litter collection data from the Edwards Aquifer Habitat Conservation Plan (EAHCP), Keep San Marcos Beautiful (KSMB), and primary litter and microplastic data I collected from the main stem of the San Marcos River twice a month for 5 months. Results show that the majority of litter found in all three survey locations are microplastics and plastic of various types. Velocity and substrate type of river stretches can be indicative of the amounts of litter found. Sources of litter can largely impact the types of items found. Lastly, current policy and deterrents are not effective in reducing/stopping litter at the source.



plastic, aquatic pollution, litter


Johnson, H. M. (2022). Macro and micro litter accumulation in the San Marcos River San Marcos, Texas, USA</i> (Unpublished thesis). Texas State University, San Marcos, Texas.


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