Phytoplankton are microscopic algae that are responsible for a significant portion of the primary production in marine ecosystems. They use sunlight to convert carbon dioxide and water into organic matter, which serves as the foundation of the food web.

Phytoplankton are responsible for producing a large proportion of the oxygen in the atmosphere through photosynthesis. They use sunlight to convert carbon dioxide and water into organic matter and release oxygen as a byproduct.

Phytoplankton require nutrients such as nitrogen, phosphorus, and silicon for growth. The availability of these nutrients in the water column is often the limiting factor for phytoplankton growth.

A phytoplankton bloom is a rapid increase in the population of phytoplankton. Blooms can be caused by a variety of factors, including nutrient enrichment, changes in water temperature, or increased sunlight.

Red tide, green tide, and brown tide are all examples of harmful algal blooms. These blooms can produce toxins that can harm marine life and humans.

Nutrient enrichment, particularly from agricultural runoff and sewage discharge, is the primary cause of harmful algal blooms. Excess nutrients can stimulate the growth of phytoplankton, leading to blooms that can produce harmful toxins.

Producing toxins is a common defense mechanism used by phytoplankton to avoid grazing by zooplankton. These toxins can deter zooplankton from feeding on phytoplankton, providing them with a competitive advantage.

Sunlight is the main factor that determines the distribution of phytoplankton in the ocean. Phytoplankton require sunlight for photosynthesis, and their distribution is limited to the photic zone, which is the upper layer of the ocean where sunlight can penetrate.

Thalassiosira is an example of a diatom, which is a type of phytoplankton that has a siliceous cell wall. Diatoms are responsible for a significant portion of primary production in marine ecosystems.

Sinking is the term used to describe the process by which phytoplankton cells sink to the ocean floor. This process is important for the transfer of organic matter from the surface ocean to the deep ocean.

Emiliania huxleyi is an example of a coccolithophore, which is a type of phytoplankton that has a calcareous cell wall. Coccolithophores are responsible for a significant portion of primary production in marine ecosystems.

Grazing is the term used to describe the process by which phytoplankton cells are consumed by zooplankton. This process is an important part of the marine food web.

Red tide is an example of a harmful algal bloom that can produce neurotoxins. These toxins can cause neurological symptoms in humans and marine life.

Phytoplankton cells can reproduce through binary fission, budding, or fragmentation. Binary fission is the most common form of reproduction, where a single cell divides into two identical daughter cells.