Objective

Apply descriptive statistics, nonparametric hypothesis testing, and correlation analysis to a real-world ecological data.

Background

Plastic pollution has become a global environmental crisis, threatening marine and terrestrial ecosystems, wildlife, and humans. Microplastics, defined as plastic particles less than 5 mm in diameter, are generated from the degradation of larger plastic debris. Once in the environment, these particles persist and accumulate, entering the food web through both direct and indirect ingestion. For consumers of these microplastics, especially top predators, the risk of contamination is high due to their position in the trophic chain and the potential for bioaccumulation and biomagnification. Check out this video for an in-depth look at how pervasive the plastic problem is.

For example, there is strong evidence for microplastic accumulation in fish, making species such as seals, dolphins, sharks, and humans vulnerable to the negative health consequences associated with contamination. Several studies, including one on the critically endangered Mediterranean monk seal (Monachus monachus), confirmed the presence of these pollutants.

Bottlenose dolphins (Tursiops truncatus), iconic and highly intelligent marine mammals, are another bioindicator species that can provide important insights into the health of marine environments. Recent research has revealed that bottlenose and other species of dolphins are ingesting microplastics, likely through contaminated prey or direct ingestion in the water column. In this case study, we explore microplastic ingestion in bottlenose dolphins stranded along the coastlines of the United States.

The Task

• Describe the abundance and types of microplastics ingested.
• Compare counts across age and sex classes using nonparametric methods.
• Evaluate correlations between dolphin size or gut content mass and microplastic abundance.
• Visualize the distribution of microplastic types and colors.