Phytoplankton

Hi everyone,
Today we're learning about phytoplankton. Phytoplankton are microscopic organisms that live in both salt and fresh water, and are mostly single-celled plants. The name phytoplankton comes from Greek and means 'drifting/wandering plants'. One of the most well-known phytoplankton species is green algae.

Photosynthesis and carbon transport

Phytoplankton contains chlorophyll and photosynthesises. This process absorbs carbon dioxide and creates oxygen, which is released into the surroundings. This is so effective that according to a NASA page: "Through photosynthesis, phytoplankton consume carbon dioxide on a scale equivalent to forests and other land plants." Phytoplankton is accountable for the majority of the carbon dioxide that is transferred from the atmosphere to the ocean. This carbon is carried to other ocean layers when the phytoplankton dies and sinks to the ocean floor or is eaten by animals, that then generate waste and also die. In fact, globally, 10 gigatons of carbon are transported from the atmosphere to the ocean floor in this way every year.

Conditions and habitat

Phytoplankton can be found worldwide but are especially abundant along coastlines. Multiple conditions make an area perfect for phytoplankton to thrive. One of the most important is the availability of nutrients, for example, calcium, iron, nitrate, phosphate, silicate and many others in varying amounts depending on the species. Other conditions include depth, predators, water temperature, wind and currents (which drive nutrients up from the ocean depths).

Blooms

If the conditions are just right, they can lead to explosive growth in the phytoplankton population, known as a bloom. These blooms can cover hundreds of square kilometres and are visible in satellite photos from space! A bloom will typically last for several weeks, however individual phytoplankton have a lifespan of only a couple of days. During these blooms, more oxygen is created and more carbon is absorbed due to increased population size.

They may look pretty, but the impacts of these blooms aren't always good. The dead phytoplankton sink down to the ocean floor and bacteria begin to decompose them. The problem is, that these bacteria use up a lot of oxygen. So much so, that when a lot of plankton die (after a bloom), the bacteria use up all the oxygen in the surrounding water causing marine animals to suffocate and die. Another problem is that some species of phytoplankton produce biotoxins. The blooms cause strong toxins to contaminate the surrounding water, poisoning the animals and the people that eat those animals. This is known as a red tide (harmful algae bloom).

Importance for marine life

Phytoplankton is very important for the aquatic food web and is eaten by a wide range of species, from zooplankton to whales. They produce and release oxygen (through photosynthesis) when they are alive, and dead phytoplankton provide waters with nutrients as well as being good for sand quality. Phytoplankton also plays a vital role in keeping the carbon dioxide levels in the atmosphere and oceans as low as possible.


We hope you enjoyed this post. See you next week!

Your Green World Blog Team💚

Sources:
http://bioresearch.wdka.nl/wp-content/uploads/2020/04/What-are-Phytoplankton_nasa.pdf
https://deepoceanfacts.com/importance-of-marine-phytoplankton

Images:
Microscopic image of a phytoplankton: This image, owned by NOAA Photo Library (on flickr.com) is licensed under CC BY 2.0.
Phytoplankton bloom from space: This image, owned by NASA Goddard Space Flight Center (on flickr.com) is licensed under CC BY 2.0.