Plastic debris in aquatic environments presents a significant danger to turtle populations worldwide. Turtles, both marine and freshwater species, frequently encounter various forms of plastic, which can disrupt their normal behaviors and compromise their well-being. The consequences of these encounters extend beyond simple entanglement, encompassing a range of internal problems that affect their survival.
Mistaking Plastic for Food
Turtles often consume plastic because they mistake it for their natural food sources, a deception rooted in both visual and olfactory cues. Plastic bags and other translucent films floating in the water can visually resemble jellyfish, a primary dietary component for many sea turtle species, such as leatherbacks. This visual mimicry makes it difficult for a foraging turtle to distinguish between a nutritious meal and harmful debris.
Beyond visual resemblance, the smell of plastic also attracts turtles due to biofouling. Algae, bacteria, and other microorganisms grow on floating plastic debris, forming a biofilm. This biofilm emits a scent mimicking their natural prey, such as krill or algae, drawing turtles in as they forage. Research shows loggerhead turtles are attracted to the smell of biofouled plastic, associating it with food odours.
Physical Consequences of Ingestion
Ingesting larger pieces of plastic, known as macroplastics, leads to severe physical harm within a turtle’s digestive system. One of the most common and immediate dangers is gastrointestinal blockage. Large plastic items, like bags or rigid fragments, can obstruct the digestive tract, preventing the passage of food and waste. This blockage can lead to severe discomfort, reduced nutrient absorption, and ultimately, starvation.
Sharp or rigid plastic fragments can cause internal injuries, including lacerations or perforations of the stomach and intestinal walls. Such injuries can result in internal bleeding, infections, and peritonitis. Furthermore, ingesting plastic can create a false sense of fullness in turtles. This leads them to stop foraging for actual food, resulting in chronic malnutrition and a gradual decline in health, even if their digestive tract is not completely blocked.
The Impact of Microplastics
Microplastics, defined as plastic fragments smaller than 5 millimeters, pose a distinct threat compared to larger plastic debris. These tiny particles can be inadvertently ingested by turtles through their diet or water filtration. Unlike macroplastics that cause blockages, microplastics can pass through the digestive system or potentially accumulate in tissues.
These minute particles can also carry harmful chemical additives from their manufacturing process, such as phthalates or bisphenol A. Furthermore, microplastics can absorb environmental toxins, like persistent organic pollutants, from the surrounding water. When ingested, these chemicals can leach into the turtle’s body, potentially disrupting endocrine functions, immune responses, or reproductive health.
Vulnerability Across Turtle Species
The threat of plastic ingestion impacts various turtle species, with some facing heightened vulnerability due to their specific diets and foraging behaviors. Leatherback sea turtles, for example, are particularly susceptible because their primary diet consists of jellyfish. Their feeding strategy involves consuming large volumes of water to filter out jellyfish, which makes them prone to accidentally ingesting plastic bags that resemble their gelatinous prey.
While sea turtles often receive more attention, freshwater turtles are also at significant risk from plastic pollution in their habitats. Rivers, lakes, and ponds frequently accumulate plastic debris, exposing species like snapping turtles or painted turtles to similar dangers of ingestion.