By Dr Mahasweta Saha

18 September 2017 - 20:02

'The rise in ocean acidity levels is causing clown fish larvae to lose their ability to tell which are the best habitats for them to settle.' Image (c) nile, used under licence and adapted from the original.
'The rise in ocean acidity is causing clown fish larvae to lose their ability to pick the best habitats to settle.' Image ©

nile, licensed under CC0 1.0 and adapted from the original.

There are more than 230,000 species of marine life in our ocean. So how do they communicate? We asked FameLab finalist and marine chemical ecologist Dr Mahasweta Saha.
How do sea creatures communicate?
Marine plants and animals, even those that can see and hear, mostly ‘talk’ to each other using chemical signals or cues. These signals make up much of the language of life in our oceans. Collectively, they are called ‘info-chemicals’, and they can be simple molecules or complex compounds.
Chemicals used to communicate within a single species are called ‘pheromones’, and those used to communicate between different species are called 'allelochemicals'.
How do these chemical signals work?
For most marine species, chemical cues determine whether they eat, fight with, run from, or mate with the creature next to them — as well as whether they are eaten by, infected by, or overgrown by natural enemies. They tell each animal how to forage, where to live, and what to eat. Signals from info-chemicals can govern the transfer of energy and nutrients within and among whole ecosystems.
A sea animal can assess sex, social status, and even whether a potential mate is sperm-deficient or sperm-sufficient using chemical cues. These cues can be so powerful that male crabs will guard, carry, and attempt to mate with sponges, air-stones, rocks, or golf balls, if these have been treated with the correct female crab pheromone.
How are climate change and pollution affecting things?
Climate change is threatening this chemical communication between plants and animals. The rise in ocean acidity levels is causing clown fish larvae to lose their ability to tell which are the best habitats for them to settle, and to avoid predators by using scent cues.
Other pollution in the sea, like plastics, can also disrupt this communication. After floating in the ocean for a while, plastics begin to send out a chemical signal called DMS (dimethylsulphide). DMS acts as a foraging cue, and smells like food to many marine species like whale sharks, penguins, fish and albatross.
Micro algae and bacteria can settle and grow on the surfaces of plastic in the sea, during a process called biofouling. These microorganisms then start sending out DMS as part of their metabolic process, which can confuse predatory animals.
What simple steps can we take to protect our oceans and stop further pollution?
Due to the small size of micro-plastics, we cannot currently remove those which are already in the oceans. For example, microbeads, which are tiny bits of plastic added to some exfoliating body washes and facial scrubs, are so small that they can easily pass through water filtration systems. However, we can start cleaning up the bigger pieces of waste, macro-plastics, and stop this source of pollution from further contaminating our waters.
There are lots of ways you can pollute less. Try some of the ideas below.
  • Reduce your plastic consumption by avoiding plastic straws, water bottles, shopping bags or cutlery. Instead, try reusable bags and water bottles and biodegradable cutlery and plates.
  • Check your beauty products and don't buy those that contain microbeads. You can download the Beat the Microbead app, which scans the bar code of your products for microbead ingredients.
  • Skip the helium balloons and fancy packaging at your next party. Consider decorating with recycled tissue paper pom-poms and reusing gift bags instead.
  • When shopping for new clothes, avoid buying synthetic textiles like polyester and acrylic. These fabrics contain tiny plastic fibres, which can shed during washing and travel through wastewater treatment plants into public waterways. A single fleece jacket can release a million fibres in a single wash.
  • Avoid powder laundry detergents, especially those with added oxidising agents to remove tough stains, because they produce the highest fibre loss during washing. Short, gentle wash cycles in cool water are best, and fabric softener can also help to reduce fibre loss.
  • Separate your organic waste into a compost pile. This not only produces nutrient-rich fertiliser, but also reduces the amount of plastic rubbish bags that could end up in the ocean.
  • Volunteer for a local beach clean or perform your own two-minute beach clean during your next outing. Post your clean-up efforts on social media using #2minbeachclean to encourage others to get involved.
  • Take the Sea Change Project pledge, which is a checklist of things you can do to protect our oceans.
You can watch Dr Saha and other talented science communicators present their research in our live-stream of the 'Hall of FameLab' on 29 September 2017, part of Science Uncovered. 

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