What is the primary concern with microplastics in surface waters?

Microplastics pose a significant environmental issue in surface waters primarily because they can adversely affect aquatic life. These tiny plastic particles, often smaller than 5 millimeters, can be ingested by various organisms, including fish, shellfish, and zooplankton. Once ingested, microplastics may cause physical harm to the digestive systems of these organisms, leading to malnutrition, decreased reproductive success, and increased mortality rates.

Furthermore, microplastics can also act as carriers for harmful pollutants, such as pesticides and heavy metals, which adhere to their surfaces. When aquatic creatures ingest these microplastics, they may inadvertently consume these toxic substances, leading to bioaccumulation and potentially impacting the entire food web, including humans who consume seafood.

The other options are not aligned with the primary concern regarding microplastics. They do not provide nutrients, are not naturally occurring as they are a product of human activity, and they do not improve water clarity; instead, they can contribute to water pollution and reduce overall water quality.