Basking Shark Marine Plastic Study

The increase in plastic being introduced into our oceans has increased at an alarming rate. From plastic bottles and containers washing up on beaches to microscopic plastics entering the food chain from broken down plastic pieces or microfibres from laundry waste water. 

At Basking Shark Scotland, we spend a lot of time on the water in the North Atlantic and especially around areas of tidal convergence. These areas are where zooplankton is concentrated (aka basking shark food) but this also means we see a lot of the associated plastic flotsam. Through our science programme we have been studying the relationship between basking sharks and zooplankton along with trialling looking at the plastic constituents of these areas of concentrated plankton. 

Basking shark feed using their unique anatomy called gill rakers, which are large brush like filters which lie in their mouth near the gill slits. These rakers trap the zooplankton as the water passes through the gills. However our concern is that zooplankton, being microscopic size, can be very similar to micro plastics and that basking sharks could be ingesting these plastics at the same time as the zooplankton.

We have very few stranded/dead basking sharks so we can’t gain any knowledge from the remains of stomach contents. However our worry is that plastics could be accumulating within the stomachs of sharks, blocking the nutrition they gain from eating the plankton or having toxic effects on them. The plastics even could be blocking parts of the gill rakers making them feed less efficiently. It may be that the plastics take many years for any effects to manifest but we there hasn't been any work done on this yet. During the summer months we have a seasonal breeding aggregation of sharks and the numbers show this is the biggest aggregation in the whole world so it's important that we look after the environment that sharks spend their summers in.

We simply don’t know how much plastics are contained within these plankton zones and how much the sharks could be ingesting or if it could be a problem for them. In order to get an initial idea we will be continuing with our trials this coming summer season. Our Autumn research programme has seen us trial a study of basking sharks feeding on zooplankton to gain quantitative  estimates of abundance of how much the sharks are eating vs areas where they are not.  We can use a similar methodology to sample to area where the sharks are feedings to then measure how much plastics are contained in these samples. We can then use this data to extrapolate out how much the basking sharks could be eating. This could provide a very important baseline to see how much a problem this could be. 

See here for a some video taken within a zooplankton (& lion mane jellyfish slick) that contained a lot of debris and broken down plastic to give you an idea.

Our study is lucky that we can capture this data whilst conducting our basking shark tours so essentially a highly expensive part of the study is hosted by ecotourism. However we do have some additional costs with additional sampling and lab equipment, along with the expenses of some volunteers to assist with working up the samples and data. All our staff have marine science qualifications so we produce all the information and associated writes up in-house as part of our committed science programme. The big BUT is that we gain no funding for any of the science work we do. Everything is funded by us running a tourism operation. In some ways this is great as we can spend so long in the field, but it does mean we have to fund everything off our own back, which means a lot of the time we simply can’t afford to do the work despite having all the opportunity to achieve it. 

This is where the public can help!!! If you have read our blog on advice on how to reduce plastic you would have seen one of the ways to do this is by using a re-usable drinks cup for take aways teas & coffees. We have commissioned our own sustainably made bamboo cups to help us fund raise to conduct our plankton study where all profits from the cup sales will go to fund this project. Hence plankton not plastic!!! By using the cups, you’ll reduce single use plastic and if you find places that do a discount for doing so, then you could be saving money too (we’ve seen between 10p and 50p off the normal cost). See here to buy one of the cups to help the project and reduce your own plastic footprint.

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