Dr. Richard Kirby, Ocean Drifters

Microplastics in the Marine Environment

Plastic litter in the oceans is a global problem. Perhaps most noticeable to people are the large items of plastic litter washed up on beaches. In fact, it is so common on beaches that sadly many people may simply accept it as a normal feature of beaches today. However, while large plastic objects are the most visible, microplastics are the most common type of plastic in the ocean and therefore also on beaches. Microplastics can include the breakdown products of larger plastic objects or arise from sources such as cosmetic microbeads or the microfibres shed by your clothes every time they are washed. Microplastics measure less than 5 mm in size and consequently, many microplastics are largely invisible to the naked eye. For example, a microfiber is less than 0.01 mm (10 µm) in diameter and so just 1/5 the diameter of a human hair.

Dr. Richard Kirby is studying the plankton food web and how we influence it by climate change, fishing and plastic pollution.

Harming the Marine Food Chain

Large plastic items in the sea, such as plastic bags, cigarette lighters, plastic bottles, and rope can be lethal to marine life when animals such as whales, seals, sea birds, and fish become entangled or mistake the rubbish for food. The small size of microplastics, however, means this plastic can affect the very base of the marine food chain in a similar fashion, when planktonic organisms become entangled (see video 1) or eat the plastic with lethal consequences (see video 2). Once microplastics have entered at the bottom of the food chain, they can then be passed upwards when the plankton are eaten by fish and the fish in turn by their predators, and so on. As plastics can also carry toxins on their surface, this provides a mechanism for the potential bioaccumulation of toxins upwards through the marine food chain.

Marine Plankton

The marine plankton are all those creatures in the sea that drift at the mercy of the ocean currents and while this definition includes the jellyfish, some of which are the largest marine invertebrates, most plankton are invisible to the naked eye and so can only be seen by microscopy.

Fish eggs in spring plankton

With good timing fish eggs appear in the spring plankton

When the larvae hatch they'll be surrounded by food.

Ceratium fusus phytoplankton

Tiny needle-like Ceratium fusus belong to the most abundant phytoplankton at the base of the marine food chain

Young spaghetti worms

Young spaghetti worms, beautiful Terebellidae soon settling to the sea bed

Dr. Richard Kirby

Richard Kirby loves plankton as only a marine biologist can. Fortunately, he is also a master plankton portraitist. It's a celebration of magnificent diversity at the microscopic level.

Natural History Magazine

Invisible Microplastic Pollution

While large plastic debris is easy to see, a recent study (Cozar A et al. (2014) Plastic debris in the ocean  Proc. Natl. Acad. Sci.  111  10239-10244) estimated that 99% of plastic remains unaccounted for in the ocean. In other words, we don’t know where it is. As microplastics can have consequences for the plankton and the marine food chain, it is clear that we need to know much more about the extent of microplastic pollution, and here, observation is a key first step to our understanding.

  • A planktonic arrow worm that is just 6 mm long has consumed a blue plastic microfiber that has coiled and blocked its gut. Just like large plastic items can block the gut and kill a fish, a turtle or whale, this video is evidence that our plastic pollution kills throughout the marine food chain. Video using a ZEISS Axio Zoom.V16 zoom microscope and a 1x Plan Neofluar objective. © Richard Kirby
  • Copepods about 1 mm in length are entangled in plastic microfibres in a plankton sample collected in the sea off Plymouth, UK. Just like marine animals such as sea birds or whales can become entangled in discarded string and ropes, our microplastic pollution can entangle even the smallest of sea creatures. Video using a ZEISS Axio Zoom.V16 zoom microscope and a 1x Plan Neofluar objective. © Richard Kirby
Dr. Richard Kirby

Dr. Richard Kirby

Dr. Richard Kirby is a  former Royal Society university research fellow, an independent marine scientist, filmmaker and expedition scientist and guide.

Dr. Kirby's passion is to bring the secret world of plankton nearer to us all. His popular website and @PlanktonPundit Twitter  and Instagram accounts are famous for excellent footage of all those minuscule creatures that float and roam the biggest ecosystems on our planet – the oceans.

He uses his ZEISS Axio Zoom.V16 zoom microscope with 1x and 2.3x Plan Neofluar objectives to capture images and movies with highest quality from these tiny little organisms in their wet element.

Share this article