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Writer's pictureDr. Algae

How Phytoplankton Remove Excess Nutrients from Aquatic Ecosystems

Phytoplankton, the microscopic photosynthetic organisms that thrive in aquatic environments, play a crucial role in maintaining the health and balance of ponds, lakes, and oceans. One of their essential ecological functions is the uptake and removal of excess nutrients, which can otherwise lead to water quality issues such as eutrophication (excess nutrients) and harmful algal blooms. In this blog, we will explore how phytoplankton help manage nutrient levels and maintain the stability of aquatic ecosystems.




The Problem of Excess Nutrients  in Ponds and Lakes

Excess nutrients, particularly nitrogen and phosphorus, can enter aquatic ecosystems through various sources, including fish waste, agricultural runoff, sewage discharge, and pollution. When these nutrients accumulate in ponds and lakes, they can lead to several environmental problems:

  1. Eutrophication:

  • Eutrophication occurs when nutrient levels rise, leading to excessive algal growth. This growth can result in algal blooms that deplete oxygen levels, harm aquatic life, and reduce water quality.

  1. Harmful Algal Blooms (HABs):

  • Some phytoplankton species, when given excessive nutrients, can produce toxins that are harmful to fish, humans, and other wildlife. HABs can result in fish kills and pose significant health risks.  The red tide blooms of Florida, blue-green toxic cyano blooms of fresh lakes and some of the beach closure alga bloom of the Great Lakes are good examples of this.

  1. Biodiversity Loss:

  • The dominance of certain phytoplankton species due to nutrient overload can outcompete and displace other species, reducing biodiversity and disrupting ecosystem balance.


How Phytoplankton Remove Excess Nutrients

  1. Nutrient Uptake:


Subculture of algae
Green Phytoplankton

  • Phytoplankton absorb nutrients from their environment for growth and reproduction. Nitrogen and phosphorus are essential components of proteins, nucleic acids, and other cellular structures.

  • Through photosynthesis, phytoplankton convert these nutrients into organic matter, effectively removing them from the water column and reducing nutrient availability.

  1. Biomass Accumulation:

  • As phytoplankton grow and reproduce, they incorporate nutrients into their biomass. This process not only removes nutrients from the water but also forms the basis of the aquatic food web.

  • When phytoplankton are consumed by zooplankton such as Hydralife's copepods, daphnia and moina, nutrients are transferred through the food chain, further contributing to nutrient cycling and the zooplankton feed the next level of organisms.


  1. Sedimentation:

  • When phytoplankton die, their cells can sink to the bottom of the water body. This process, known as sedimentation, sequesters nutrients in the sediment, reducing their availability in the water column.

  • Sedimentation can play a significant role in nutrient removal, especially in lakes and reservoirs where water movement is minimal.

  1. Facilitating Denitrification:

  • Phytoplankton can influence microbial processes that contribute to nutrient removal. For example, by altering oxygen levels and providing organic carbon, phytoplankton can enhance denitrification—a process where bacteria convert nitrate into nitrogen gas, removing it from the aquatic system. Phytoplankton also directly utilize ammonia NH4, nitrite No2 and nitrate NO3 therefore reducing the toxicity of water and relieving much of the work from denitrifying bacteria.  


Benefits of Nutrient Removal by Phytoplankton

  1. Improved Water Quality:

  • By removing excess nutrients, phytoplankton help maintain water clarity, reduce the risk of toxic algal blooms, and support higher oxygen levels, leading to healthier aquatic environments.

  1. Ecosystem Stability:

  • Balanced nutrient levels promote diverse phytoplankton communities, supporting a wide range of aquatic life and ensuring ecosystem resilience.

  1. Support for Aquatic Food Webs:

  • Phytoplankton serve as the primary producers in aquatic ecosystems, forming the base of the food web and supporting fish, invertebrates, and other organisms.

  1. Natural Bioremediation:

  • The ability of phytoplankton to uptake and sequester nutrients makes them a natural solution for mitigating nutrient pollution and improving the health of aquatic ecosystems.


Factors Affecting Phytoplankton Nutrient Uptake

  1. Light Availability:

  • Photosynthesis, the process by which phytoplankton assimilate nutrients, requires sunlight. Light availability can influence the rate of nutrient uptake and phytoplankton growth.

  1. Water Temperature:

  • Temperature affects metabolic rates and nutrient uptake efficiency. Warmer temperatures can increase phytoplankton growth, but extreme temperatures may lead to stress and reduced nutrient removal.

  1. Nutrient Ratios:

  • The ratio of nitrogen to phosphorus can influence phytoplankton community composition and nutrient uptake dynamics. Different species have varying nutrient requirements and preferences.

  1. Water Movement:

  • Water mixing and circulation can affect nutrient distribution and availability, influencing phytoplankton growth and nutrient uptake.


Conclusion


Scenedesmus arcuatus under a microscope
Scenedesmus arcuatus

Phytoplankton play a vital role in removing excess nutrients from aquatic ecosystems, helping to maintain water quality and ecological balance. By understanding and supporting the natural processes of nutrient uptake and cycling by phytoplankton, we can better manage nutrient pollution and protect the health of ponds, lakes, and other water bodies. Hydralife offers diverse and healthy phytoplankton to inoculate or boost your waters.  Phytoplankton is such a wonderful and powerful organism, it can significantly reduce nitrogen and phosphate levels within a week, when in the right conditions.  Phytoplankton communities is essential for sustaining aquatic life and ensuring the resilience of these vital ecosystems.

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