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The Role of Diatoms in Aquatic Ecosystems
2024-10-14
In aquatic ecosystems, algae (microalgae) are important organisms that include both harmful species and those beneficial to the ecosystem. Among them, diatoms are a type of beneficial microalgae with significant ecological value. This article will explore the definition of diatoms, common types, ecological functions, and effective cultivation methods.
I. What Are Diatoms?
Diatoms are tiny algae that are widely found in various aquatic environments. They are heterotrophic organisms that can grow individually or form colonies. Typically, diatoms are unicellular and exist mainly in forms such as Fragillaria, Meridion, Tabellaria, and Asterionella. A distinctive feature of diatom cells is their cell wall made of silica, forming unique diatom frustules. These frustules come in various shapes and typically consist of two asymmetrical halves with a partition. Diatoms prefer cooler water temperatures, thriving particularly in spring and autumn, and are well-suited for growth in silica-rich, flowing water.
II. Common Types of Diatoms
1.Cyclotella
These cells are disk-shaped with characteristic markings. Cyclotella has a high-density cell wall and usually grows in the bottom layer of water bodies. This type of algae plays a crucial role in water quality regulation and has a significant purifying effect in aquaculture. Cyclotella meneghiniana is an ideal feed for juvenile Chinese mitten crabs.
2.Pseudonitzschia
The primary form of this algae is triangular radiating cells, which typically lack a siliceous cell wall, making them suitable for various cultivation conditions.
3.Navicula
Navicula frustules are oval or near-round, displaying distinct striations and are one of the most diverse genera of marine planktonic diatoms.
4.Gyrosigma
This single-celled algae has crescent-shaped frustules with various textures, exhibiting strong adaptability.
5.Stauroneis
Stauroneis frustules can be linear, oval, or egg-shaped, found widely in freshwater, seawater, and brackish environments.
6.Nannochloropsis
An important feed source in aquaculture, Nannochloropsis is rich in DHA and ARA, serving as feed for the larvae of Pacific oysters, scallops, groupers, shrimp, and crabs.
7.Fragilaria
These algae have elongated cells, typically attached to other plants or objects, making them a vital component of freshwater ecosystems
8.Asterionella
Known for its distinctive frustules with lip-like projections, this diatom is common in aquatic environments.
9.Surirella
Featuring long, oval-shaped frustules, Surirella exhibits complex cell structures and wide adaptability.
III. Ecological Value of Diatoms
1.Oxygen Production
Diatoms produce substantial amounts of oxygen through photosynthesis, contributing to 80-90% of dissolved oxygen in water. Their benthic and suspended characteristics allow them to distribute oxygen evenly throughout the water column, preventing hypoxia in the lower layers.
2.Nutritional Source
Rich in vitamins and bioavailable amino acids, diatoms serve as high-quality feed for fish and shrimp. Unlike toxic algae, diatoms do not harm the hepatopancreas of aquatic animals.
3.Water Quality Purification
Diatoms efficiently utilize nutrients and possess metabolic capabilities that help purify water. Their unique metabolic mechanisms reduce ammonia nitrogen and nitrite levels, maintaining a stable pH conducive to fish and shrimp growth.
IV. How to Cultivate Diatom Water
To effectively cultivate diatom water, it is advisable to focus on diatoms and green algae. This combination leverages the self-purifying ability of green algae and the stability of diatoms, resulting in clear, nutrient-rich water. Ideally, the water's transparency should remain between 20-30 centimeters, with a greenish color.
In practice, if beneficial diatoms are already present in the external water source, they can be used directly. Additionally, diatom-specific fertilizers can promote growth. If natural sources are lacking, it is essential to supplement with beneficial diatoms to ensure their dominance in the water body.
Various diatom products are available on the market, including liquids and powders. During usage, powders should be soaked in clean water for 2-3 days before application, while liquid products can be added directly. It is also recommended to use these products alongside beneficial bacteria to enhance nutrient utilization and promote algal growth.
The strategy for cultivating diatom water should involve continuous inoculation from nearby water bodies to develop diatom populations that adapt to local conditions. By regularly supplementing nutrients and diatom-rich water, one can ensure stable growth of diatoms in ponds for at least a week.
Furthermore, introducing a small number of filter-feeding fish and snails in the pond can help balance the ecosystem and reduce grazing pressure on diatoms, enhancing their survival advantage.
V. Conclusion
As an integral part of aquatic ecosystems, diatoms play an irreplaceable role in water quality regulation, oxygen generation, and aquaculture. Through scientific cultivation and management, it is possible to effectively promote the growth of diatoms, ensuring ecological balance and health in aquatic environments. Understanding the characteristics and ecological functions of diatoms will significantly support the sustainable development of aquaculture.