Ocean Microplastics: How Widespread is the Problem?

So we know that Microplastics are a problem. We've talked about what we know and suspect we know about their effects on marine mammals and marine invertebrates. Now lets talk about how widespread the issue is.

The Vast Oceans of Microplastics

Microplastics are not confined to heavily polluted areas; they have been found almost everywhere. Research conducted by the National Oceanic and Atmospheric Administration (NOAA) indicates that microplastics are present at high quantities in every ocean basin, including some of the most remote areas in the world. For example, sampling in the Antarctic Ocean has reported microplastic particles at concentrations of up to 12,000 particles per square kilometer. Because there's no major sources of pollution there, what that reveals is that ocean currents are and have been transporting these particles for thousands of miles, all across the world. Microplastics released anywhere are thus truly a global problem.

Even the depths of the Mariana Trench, the deepest part of our oceans, are not spared from the presence of microplastics. Microplastics, and Macroplastics for that matter, are now being consistently found at depths of over 10,000 meters which paints a sad picture of exactly how far-reaching plastic pollution has become.

Coastal Waters

Coastal regions are particularly vulnerable to microplastic accumulation. For instance, studies in San Francisco Bay have recorded concentrations of around 1.5 million particles per square kilometer. This is because these areas are the ground zero for plastic pollution released by nearby urban centers. The influence of urban runoff especially cannot be overstated: as research indicates that 80% of marine debris can be traced back to land-based sources, which overwhelmingly come from urban settings.

Another study in Chesapeake Bay found that microplastics were more present in urban estuaries than in rural ones, with microplastic concentrations increasing by almost 300% in highly urbanized settings. Though an obvious answer, it proves beyond a shadow of a doubt that where the problem is coming from. Not just industry and waste plastics, but from human activity itself.

Ocean Currents

As previously mentioned, Ocean currents serve as more or less global highways for plastics, carrying them across thousands of miles to totally different regions of the world. The Great Pacific Garbage Patch is probably the best showcase of this phenomenon. There, from across the entire pacific ocean and two continents, plastics accumulate. Its gotten so bad there that some estimates suggest that up to 1.8 trillion pieces of plastic are floating in the area, with a significant portion of this being microplastics.

In addition microplastics accumulate in convergence zones, where seperate ocean currents come together. Places like the horn of Africa. These regions trap floating debris, making them hotspots of microplastic concentration.

The Open Ocean

Even the most remote open ocean areas, places that do not inherently congregate plastic pollution in the same way other areas do are not safe from microplastics. Studies conducted in the South Indian and South Pacific Oceans outside costal areas or major gyres found microplastic concentrations ranging from 100 to 1000 particle per cubic meter

Freshwater Inputs and Their Influence

Humans like being near sources of freshwater, and as we have indicated a large amount of human activity, not just waste, causes microplastic contamination. Microplastics find their way into the ocean through rivers and lakes because of this. The Yangtze River, one of the world's largest rivers, discharges about 330 tons of microplastics into the ocean each year. Similarly, findings from studies conducted in the Great Lakes show that microplastic concentrations range from 10 to 100 particles per liter of water depending on the area in question, affecting local ecosystems before they eventually make their way to the sea.

Stormwater runoff is a particularly critical pathway for microplastic pollution entering freshwater systems. During heavy rain, water can carry plastic litter from urban areas straight into rivers, contributing significantly to coastal microplastic pollution.

Polar Regions

The belief that polar regions are relatively untouched by human influence has been increasingly challenged on multiple fronts, and microplastics are only one of them. Research in the Arctic reveals that microplastics have been found in sea ice, with studies showing concentrations as high as 20 plastic particles per liter of seawater. Furthermore, in Antarctic waters, it has been discovered that there exists a presence of microplastics in the diets of krill, one of the most important keystone species in the Antarctic ecosystem. This could threaten the entire food web in Antarctica as well as threaten bioaccumulation to several migratory species such as whales and sharks.

Benthic Environments: The Ocean Floor

We must remember not to put all of our focus on the parts of the ocean we can see and easily interact with. The surface often garners the most attention because its much more visible but the ocean floor has been silently accumulating microplastics for as long as plastics have been in the oceans. Studies from the Mediterranean Sea have shown microplastic concentrations as high as 4,000 particles per cubic meter on the vast majority of the seabed. Organisms living on the seabed, such as mollusks and crustaceans, are ingesting these particles, leading to potential toxic effects and entering the food chain.