What is phytoplankton? Lets take a moment to break the word down into its parts. We have Phyto and plankton Phyto is greek for plant and plankton means free swimming. Technically, plankton is any orgamisn, plant or animals that cannot swim against the current of the ocean. So, phytoplankton is plankton life that is comrpised of plants, and algaes.

It is known that green plants liberate oxygen and produce carbohydrates, a basic link in the food chain of plants to animals to people. Collectively, this chemical process is referred to as photosynthesis (photo = light, synthesis = to make). In these tiny food factories, there is a chemical compound called chlorophyll that, in combination with sunlight, converts carbon dioxide, water, and minerals into edible carbohydrates, proteins, and fats. Thus, these phytoplankton are the basis for the oceanic food chain.
Sea animals cannot perform this biological food-making process. Two-thirds of all the photosynthesis that takes place on this earth occurs in the oceans that yearly create 80 to 160 billion tons of carbohydrates. So numerous are these tiny plant forms that they often turn the water green, brown, or reddish, and are called red tides.

Plankton in general are passivlely drifting or weakly swimming organisms found in both freshwater and marine environments. They can be microscopic single celled organisms, to giant jellyfish tha are meteres in total length. They can be plankton their whole life, like copepods and are called holoplankton. Or they can be plankton just for the larval stages, as is the case with certain fish, arthropods and molluscs and they are called meroplankton. As we have learned, there is plant plankton, aka phytoplankton, and there is also zooplanlton, or animal plankton. Zooplankton are all the larval fishes, mollsuks, and copepods to name a few species.
Plankton make up the basis of the food chain throughout the ocean. These single cell phytoplankton are the main food for millions of other organisms that in turn are food for larger predators, and we can follow this all the way up the food chain to humans. The role of phytoplankton, or microalgae is to cycle andconvert nutrients. Because phytoplankton can utilize sunlight for energy, photosynthesis, they can take minerals and nutrients from their surroundsing and use the light enegry and make enegery. One of the end products of photosynthesis is the production of oxygen. Because the biomass of phytoplankton is so large, the end result oxygen production helps keep our planet hispoitable for us humans to live here.
Like all plants, phytoplankton play a role in nutrient cycling as well. They utilize inorganic minerals and organic compiunds to help themselves grow. By utilizing compounds like ammonia, urea, nitrates, phosphates and potasium and metals like iron, zinc and copper they help distribute these to other organsims and help remove them from the water column. However, this removel is not permanent, as its constantly rereleased by the death and decomposition of the algae cells.
Microalages are the main source of nutrients for many smaller organisms like zooplankton. Because phytoplankton are a rich source of carbohydrates, proteins and fats they are the building block of life in the seas. In a balanced ecosystem, phytoplankton provide food for a wide range of sea creatures including whales, shrimp, snails, and jellyfish. When too many nutrients are available, phytoplankton may grow out of control and form harmful algal blooms (HABs). These blooms can produce extremely toxic compounds that have harmful effects on fish, shellfish, mammals, birds, and even people.
Why do we care? For one, phytoplankton absorb a lot of CO2. In this link, it supports that without phytoplankton the world would be a very different place. This is important to us on land because we can influence the balance of these micro organisms. Our pollution, run off and fertilizers can unbalance this ecosystem and cause the harmful blooms and knock out of whack this balanced system.When conditions are right, phytoplankton populations can grow explosively, a phenomenon known as a bloom. Blooms in the ocean may cover hundreds of square kilometers and are easily visible in satellite images. A bloom may last several weeks, but the life span of any individual phytoplankton is rarely more than a few days.

We all need to be aware of what we put into the ocean and how it can impact the systems. Afterall we depend on the ocean for our health and comfort too.