ZEISS helps to highlight an invisible problem of global scale
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.
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.
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.
Video 1: 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
Video 2: 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
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Dr Richard Kirby
The passion of marine scientist Dr Richard Kirby is to bring the secret world of plankton nearer to us all. His popular website and @PlanktonPundit Twitter account 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.