Phytoplankton

Definition

Phytoplankton are microscopic, photosynthetic organisms that drift in aquatic environments, forming the base of the food web in marine and freshwater ecosystems. They play a critical role in global carbon cycling and oxygen production, making them essential for sustaining life in aquatic biomes. Their presence supports a diverse array of marine species and influences nutrient dynamics within these environments.

5 Must Know Facts For Your Next Test

1. Phytoplankton contribute to about half of the Earth's oxygen supply through photosynthesis.
2. There are two main groups of phytoplankton: cyanobacteria (blue-green algae) and eukaryotic algae, including diatoms and dinoflagellates.
3. Phytoplankton populations can rapidly change based on nutrient availability, light conditions, and water temperature, leading to phenomena like algal blooms.
4. The size of phytoplankton typically ranges from 0.2 to 2 millimeters, making them too small to be seen without a microscope.
5. Phytoplankton are sensitive indicators of environmental change; shifts in their populations can signal changes in water quality and climate conditions.

Review Questions

• How do phytoplankton contribute to the overall productivity of aquatic ecosystems?
  • Phytoplankton serve as primary producers in aquatic ecosystems by converting sunlight into energy through photosynthesis. This process not only produces oxygen but also forms the basis of the food web, supporting various organisms such as zooplankton and larger marine life. The abundance and health of phytoplankton populations directly influence the productivity and biodiversity of these ecosystems.
• What factors can lead to harmful algal blooms involving phytoplankton, and what are the potential ecological consequences?
  • Harmful algal blooms can occur when phytoplankton populations grow excessively due to high nutrient levels, often from agricultural runoff or pollution. These blooms can deplete oxygen in the water, leading to dead zones where marine life cannot survive. Additionally, some blooms produce toxins that can harm aquatic organisms and pose risks to human health through contaminated seafood.
• Evaluate the role of phytoplankton in climate regulation and how changes in their populations might impact global climate patterns.
  • Phytoplankton play a significant role in climate regulation by absorbing carbon dioxide during photosynthesis and contributing to carbon sequestration in ocean sediments. Changes in their populations, due to factors such as temperature fluctuations or nutrient availability, could alter this balance and affect global carbon cycles. A decrease in phytoplankton could result in higher atmospheric CO2 levels, exacerbating climate change effects, while an increase could enhance carbon storage but also disrupt marine ecosystems.

Related terms

Zooplankton: Zooplankton are small, often microscopic animals that drift in aquatic environments and feed on phytoplankton, forming a crucial link in the aquatic food web.

Nutrient Cycling: Nutrient cycling refers to the movement and exchange of organic and inorganic matter back into the production of living matter, crucial for maintaining ecosystem health.

Primary Production: Primary production is the process by which autotrophs, like phytoplankton, convert light energy into chemical energy through photosynthesis, forming the foundation of food chains.