Plankton: Small Wanderers in the BIG Blue World.
Karolina Zarzyczny
J.R.R. Tolkien, author of the Lord of the Rings, once said “Not all those who wander are lost...” and he was right. Plankton may be small, wandering the blue world by the means of oceanic currents, but they are certainly not lost, and are facing some of their biggest threats yet.
Human induced climate change is threatening our oceans. Rising temperatures are resulting in coral bleaching and skewing of the sex ratios of sea turtles. All whilst the Arctic ice is shrinking, sea levels are rising, and polar bears are losing their homes. However, you may not know that the impact of climate change on some of the smallest organisms, without which the whole marine ecosystem would collapse. That group of organisms is known as Plankton
Tiny larval crab (megalopa) sitting on my finger. Larvae like these are an important part of the plankton plankton group. Photo: @ritasteyn
What is plankton?
The name “Plankton” is derived from the Greek word “Planktos” meaning “wandering”. It is a group of small organisms which float around in the water column. Plankton includes the bacterioplankton, phytoplankton comprising of algae, and zooplankton which includes small animals such as larvae of fish, crabs, molluscs and echinoderms. Zooplankton can be further divided into holoplankton; animals which remain planktonic throughout their whole life and meroplankton; animals such as larvae of fish which are planktonic for just a portion of it.
Why is plankton important?
Plankton is kind of a big deal, not just for the marine ecosystem, but for the whole planet. Around 50% of the oxygen you breathe is produced by plankton. In case that didn’t make it important enough, plankton is a basic food source for fish, jellyfish, corals and even marine mammals. It feeds a variety of sharks as well as the baleen whales and rays. Without plankton, fisheries would collapse not only severely damaging the economy but also depriving a huge proportion of people of food.
Whale shark - the biggest fish in the ocean - feeds on plankton. Photo: @SamanthaReynolds
How is climate change affecting plankton?
Plankton is negatively affected by human induced climate change. The recent Intergovernmental Panel on Climate Change (IPPC) report has highlighted that around 30% of human produced carbon dioxide has already been absorbed by the oceans, resulting in ocean acidification. In fact, according to the IPPC report the oceans have become more acidic since the industrial period started and are showing the biggest pH change in at least 65 million years! Acidic oceans mean that the shells of animals such as Pteropods (small planktonic snails) are dissolving. These animals have to divert their energy investment into building shells, compromising their growth and reproduction, which has detrimental effects on their populations.
Increasing sea surface temperature has resulted in warm-water plankton shifting their geographic ranges towards the poles. Meanwhile, the cold-water plankton, such as the Atlantic krill which make up a large proportion of marine mammal diet, have seen a vast decline. Furthermore, ocean warming appears to be affecting plankton species at different rates, resulting in varied range shifts which can potentially alter the plankton community.
The impact of climate change on the ocean is so serious that the IPPC has decided to publish a special report, dedicated just to our oceans. This special report will be finalized in September 2019 so make sure to watch this space!
Manta rays are large filter feeders that rely on plankton as a source of food. Photo: @Maldivesunderwateriniative
So, what can you do about it?
Reducing your carbon footprint will not only help protect our oceans but also a wide variety of terrestrial ecosystems, and it’s easier than most people think. Buy local and seasonal produce to reduce your food miles; not only will you be supporting your local farmers, but it is also much easier to buy market produce without the unnecessary packaging! Reduce your red meat intake as it comes from ruminant farming which is one of the biggest producers of greenhouse gas emissions. You could even join the Meatless Mondays movement. It’s a good excuse to experiment with your cooking and it’s helping the environment (just remember to buy local!). Avoid unnecessary purchases and try upcycling or fixing items instead; it’ll reduce your carbon footprint and save you some money! Finally, explore more areas on foot rather than from a car window and enjoy your surroundings.