Yes, of course it’s phytoplankton.

Phytoplankton are tiny marine plants, often just a single cell. They float within the top 100 metres of all the World’s oceans. Their aim in life is simple; capture energy from the sun; turn it into energy, and reproduce. And they are good at it.

If left alone in optimum conditions, one ton of phytoplankton can soon become millions. Phytoplankton are the start of the oceanic food chain but, unlike land plants, they are nearly 100 per cent edible. Virtually all the animals in the open ocean either eat phytoplankton or the animals that feed on them.

Like all plants, phytoplankton need light and a steady supply of nutrients and minerals to grow. In the open ocean, these nutrients come from dead marine life that has sunk to the ocean floor, where they are broken down by an army of deep sea decomposers. These heavy nutrients stay near the ocean floor until they are brought to the surface by oceanic currents or up-wellings.

When these nutrients reach the top 100 metres of the ocean the light is strong enough for photosynthesis. The combination of a rich supply of nutrients and sunlight results in a dramatic increase in the phytoplankton population.

Human activities, such as the removal of large masses of fish and the dumping of incidentally caught unwanted fish, birds and mammals, radically alter the amount of dead marine life that reaches the ocean floor. The changes in the mass of dead marine life has a big impact on fish populations and the ocean ecosystem as a whole.