Study Finds Plastic Pollution Driving Rise in Toxic Algae Blooms

Toxic algae blooms, commonly known as red tides, are becoming a serious global environmental problem, causing beach closures and widespread marine life deaths from Australia to the Arctic. While agricultural runoff has long been considered the main trigger behind these harmful algal blooms, new research from the University of California, San Diego highlights plastic pollution as a major and unexpected contributor.

A study published in Communications Sustainability reveals that petroleum-based microplastics worsen toxic algae blooms by destroying the algae’s natural predators rather than directly feeding the algae. Researchers conducted a three-month experiment across 30 controlled pond ecosystems to examine how different types of plastics affect aquatic life. They compared conventional fossil fuel-based plastics with newer plant-based biodegradable alternatives.

The findings showed that ecosystems containing petroleum-based microplastics experienced a rapid collapse in zooplankton populations. Zooplankton are tiny aquatic organisms that play a critical role in controlling algae growth by feeding on it. According to lead author Scott Morton, the petroleum plastics either caused zooplankton to die off quickly or significantly reduced their ability to reproduce. In contrast, biodegradable plastics did not produce the same harmful effects.

As zooplankton populations declined in the presence of petroleum plastics, algae growth increased dramatically due to the absence of natural grazing. This imbalance directly led to the formation of algal blooms in the affected ecosystems. Tanks containing biodegradable plastics maintained healthier zooplankton populations, which continued to regulate algae levels and preserved overall ecosystem stability.

The researchers concluded that microplastics, especially those derived from petroleum, can disrupt aquatic ecosystems by altering microbial community structure and function. These disruptions create conditions that favor the rapid spread of harmful algal blooms. The study emphasizes that plastic waste entering oceans and freshwater systems is causing ecological damage that is still not fully understood.

The findings also suggest a potential solution. Transitioning from traditional plastics to materials designed to biodegrade naturally could reduce ecological and public health risks linked to microplastic pollution. By limiting the use of petroleum-based plastics, it may be possible to protect aquatic food webs and reduce the growing threat of toxic algae blooms worldwide.