Hermit Crabs LOOOVE Plastic

What food do you love, but know its not good for you?

Comic of Red Hairy Hermit Crab Talking to a Pencil Urchin

A recently released study by the Hull University in England found the chemical additive, oleamide, which is released from plastic gets crabs excited.

The crabs showed elevated respiration rates (an indicator of excitement) when in the presence of even a small amount of oleamide.

Comic of Marine Hermit Crab talking to Pencil Urchin

While this response could be an indicator of sexual excitement, it is also similar to their feeding response.

When arthropods decompose they release oleic acid, which is very similar to the chemical make up of oleamide that is released by the plastic.

Comic of Crab telling an urchin he gets excited by plastic.

As scavengers, and opportunistic eaters, a crabs food is often comprised of dead, decomposing matter that contains the oleic acid. Since the compound found in plastic is so similar to one of the chemicals in their food, it could explain the crab's positive association with the plastic.

What is your favorite type of plastic to eat?

Oh are you going to tell me you don’t eat plastic? Unfortunately, there’s a real good chance that isn’t true. Let me tell you about this study by The University of Queensland, you might want to sit down for this. 

They looked at tissue samples of a variety of different species- 10 oysters, 10 farmed tiger prawns, 10 wild squid, five wild blue crab and 10 wild sardines. They found plastic in 100% of the samples they looked at. 

Of all the species they looked at they found Sardines had the highest amount of plastic. 

The study’s lead author said this “Considering an average serving, a seafood eater could be exposed to approximately 0.7mg of plastic when ingesting an average serving of oysters or squid, and up to 30mg of plastic when eating sardines, respectively …. For comparison, 30mg is the average weight of a grain of rice."

Now before you say “I don’t eat seafood, so I don’t have to worry.” If micro plastics have gotten into the tissues of sessile organisms that live on the bottom of the ocean, don’t for a second think they haven’t infiltrated our land based foods systems as well. 

To Read the full paper: https://pubs.acs.org/doi/pdf/10.1021/acs.est.0c02337

Microplastic Trapping Corals

Which of these catches more plastic particles- sand beds, coral reefs, sea grass beds, or macro-algae?

A study released last month by Jaco C. de Smit et al. looked at how different nearshore habitats trap and collect micro plastics.

They looked how sand/ sediment bed, sea grass, macro algae, and Stylophora (coral) were able to trap 2 different sizes of micro-plastics- 2.5mm and .5 mm.

What they found is that habitats with more complex structures trapped a higher amount of micro-plastics, but the area which trapped the most micro plastics was the sediment, which trapped 1 to 2 times more than any of the other areas.

The reason they believe this happened is because of the near-bed turbulent kinetic energy which is a contributing factor to sediment trapping.

Of the 2 different sizes of microplastics that were trapped, the .5mm particles seemed to be trapped more frequently than the 2.5 mm particles.

We already know micro-plastics are an issue, why does study this matter?

Nearshore ecosystems, like sea grass beds and coral reefs are hugely productive ecosystems and act as nurseries for many species of fish and sharks. According to this study they have large capacity for sequestering plastic. With these areas that are used by animals in vulnerable life stages, being inundated with micro plastics, it is much easier for them to get ingested and cause issues starting from early on. If the inhabitants of these area start to have issues, so too with the areas themselves.

To read their full article search here.