Plastic’s Deadly Toll on Whales and Dolphins

The ocean’s giants are being killed not only by ghost nets but also by invisible microplastics rising through the food chain.

Last week, we traced how floating plastic waste is swept into five major oceanic gyres – the North Pacific, South Pacific, North Atlantic, South Atlantic, and Indian Ocean gyres – where it accumulates in vast offshore zones. This week, we turn to the largest and most notorious of them all: the Great Pacific Garbage Patch, located within the North Pacific Gyre between Hawaii and California.

This vast accumulation zone is estimated to cover roughly 1.6 million square kilometres — an area larger than the combined landmass of all the states of South India, West India and parts of Central India. Its sheer size makes it one of the most disturbing symbols of the global plastic crisis.

The patch is formed within the North Pacific Subtropical Gyre, a massive system of rotating ocean currents that acts like a slow-moving whirlpool. These currents draw floating debris inward and trap it in a relatively stable, low-energy central zone, allowing plastic waste to build up over time instead of dispersing.

According to a 2022 study by scientists at The Ocean Cleanup Foundation, the Great Pacific Garbage Patch contains around 100,000 tonnes of plastic — roughly the weight of 700 Boeing 777 aircraft. Researchers estimate that it holds nearly 1.8 trillion pieces of plastic, ranging from tiny fragments to large discarded objects, much of which is carried there by currents from different parts of the world.

Almost 94 per cent of those pieces are microplastics. Yet by weight, about 92 per cent of the total mass consists of larger debris such as fishing gear. Nearly 46 per cent of the waste is made up of abandoned or lost fishing nets, often called “ghost nets”, which continue to entangle and kill marine life long after they have been discarded.

Poisoned Waters

The ocean is perhaps the most vulnerable environment when it comes to plastic waste. Once plastic enters the sea, it respects no boundaries and can travel vast distances across the world’s waters.

We already know that plastic can persist in the environment for years without fully breaking down. But in the ocean, waves, currents and storms gradually batter it into smaller fragments, until many pieces become tinier than a grain of sand.

These tiny particles, known as microplastics, are now among the most serious forms of pollution in both water and on land. Because they are so small, they are easily swallowed by marine organisms and can move through the food chain.

It is estimated that plastic pollution in the oceans kills more than 100,000 marine mammals, reptiles and other animals every year. Plastic harms marine species in many ways — through entanglement, injury, ingestion and toxic contamination.

One of the most critical factors is the size of the plastic. Large items can trap or wound animals, while smaller fragments and microplastics can be ingested by different species, causing damage over time in less visible but equally dangerous ways.

Marine Life Toll

Whales and other marine mammals are especially vulnerable to plastic pollution, particularly entanglement in ghost fishing gear. These abandoned or lost nets continue to trap and kill long after they are discarded.

An estimated 300,000 whales, dolphins and porpoises die every year after becoming entangled in ghost gear. For many, escape is impossible. They may drown, suffer deep injuries, or weaken slowly over time.

Marine mammals are also affected in another alarming way — by ingesting plastic, either directly or indirectly through the ocean’s complex food chains and food webs.

A recent study led by marine biologists at Stanford University found that blue whales, the largest animals on Earth, may consume around 10 million pieces of microplastic every day. In some cases, that amounts to as much as 95 pounds daily.

Surprisingly, these whales do not ingest most of these plastics directly from the surrounding water. Instead, much of it comes from the krill — tiny shrimp-like creatures that form their primary food. And that raises an unsettling question: where do the krill get the microplastics from? From the same polluted marine ecosystem that is now contaminating life at every level.

More on this in my next article. Till then, have a great weekend!

(The author is an environmentalist. Views Personal.)