Stunning! The "Underwater Forest" at Liangzi Lake Qirun Base

　　There is a type of plant on Earth that particularly loves water. Not only are its roots deeply embedded in the bottom mud of rivers, lakes, and ponds, but its leaves and other photosynthetic organs are also completely submerged underwater. Due to this characteristic, they are collectively called submerged plants. Like humans, submerged plants also possess amazing survival wisdom.

　　 Liangzi Lake Cultivation Base: A Pioneer in Innovation and Application

　　As one of the company's three main businesses, water ecological restoration follows national environmental protection policies and requirements. Relying on the Liangzi Lake base, it brings together the company's expert wisdom and a team of experienced scientific research and innovation personnel to achieve breakthroughs in key technologies and innovative applications in core areas.

　　The Liangzi Lake base serves as a research center for water ecological restoration technology, undertaking the research and experimental tasks of core technologies and key aspects of water ecological restoration. It also serves as a nursery for plants selected for projects, undertaking the screening and mass production of plants required for different projects.

　　As the most important part of water ecological restoration, the construction of an "underwater forest" has yielded innovative practical results at the Liangzi Lake base, from plant selection, matching, and survival to the restoration of aquatic ecosystems and the formation of new steady states. These results are the source of confidence for the company's development in water ecological restoration. Starting from the Liangzi Lake base, and making full use of its innovative achievements, we are capable of recreating the vitality of "underwater forests" in similar lakes and rivers in Wuhan, Hubei Province, and even the whole country, achieving a magnificent transformation of "clear water, green banks, beautiful scenery, and a healthy ecosystem".

Liangzi Lake Base

　　 Part 1: Have you ever seen an underwater forest?

　　On the eve of the Mid-Autumn Festival, colleagues from the water ecology department drove to the Liangzi Lake aquatic plant cultivation base for research and study. Through different perspectives, they observed the growth and survival characteristics of submerged plants up close, thereby discovering the infinite mysteries of submerged plants and exploring the hidden knowledge of water purification in the plant world.

　　In the northwest corner of the base, looking down from the ridge, the lake water is crystal clear. Strip-like Vallisneria, dark green Ceratophyllum, and clustered Myriophyllum, water plants of various colors and shapes sway with the waves, forming the base's "underwater forest" together with the fish, shrimp, snails, and shellfish in the water body.

　　"Underwater forest" refers to restoring an ecosystem underwater by planting Vallisneria, Hydrilla verticillata, Potamogeton crispus, Ceratophyllum demersum, Najas marina, Elodea nuttallii, etc. This ecosystem absorbs nutrients from the water, reducing eutrophication pollution, and provides habitats for fish, shrimp and snails. It is the most important link in the aquatic ecological chain. By constructing an underwater ecological chain, the plants and animals in the water can coexist and mutually restrict each other, ensuring the balance of the underwater food chain, increasing the water's self-purification ability, making it breathe like a human, and becoming clearer. Because the root system of submerged plants is in the bottom mud, it can absorb pollutants from the water and mud, resulting in a more thorough purification effect than planting floating plants and emergent plants.

　　Part 2: Do you know the survival wisdom of underwater forests?

　　As one of the main primary producers, submerged plants not only have the ability to absorb nitrogen and phosphorus, but also form the basis for maintaining aquatic biodiversity.

　　“Born in the water”

　　The roots, stems, and leaves of submerged plants can directly absorb nitrogen and phosphorus nutrients from the bottom mud and water, and the allelochemicals secreted by submerged plants have a significant inhibitory effect on algae.

　　“Growing in the water”

　　Submerged plants absorb a large amount of nutrients from the water body, becoming excellent varieties, causing algae to lack nutrients and thus inhibiting their development.

　　“Protecting the habitat”

　　Submerged plants can not only effectively increase the dissolved oxygen concentration in the water body, but also promote the sedimentation of biological and abiological suspended matter in the water body and inhibit the resuspension of bottom sediment, effectively increasing the water transparency.

　　“Symbiosis and coexistence”

　　Submerged plants can not only provide food for the complex food chain in the water body, but also provide attachment substrates, habitats, and spawning grounds for other aquatic animals. Aquatic animals prey on phytoplankton, greatly improving water transparency and forming a virtuous cycle. The roots, stems, and leaves of submerged plants in the water body can serve as carriers for microorganisms, facilitating the formation of biofilms, increasing the amount of microorganisms in the water body, and ultimately improving the water's self-purification ability.

　　Part 3: Do you know these plants?

　　According to Chen Xuwu, the person in charge of the base, the base now cultivates seedlings on more than sixty mu of land, including forty mu of submerged plants, ten mu of emergent plants, and twelve mu of floating-leaved plants. The main varieties of submerged plants are Vallisneria, Myriophyllum, Ceratophyllum, and Hydrilla. All plants are propagated from late March to early April. Vallisneria and Myriophyllum can be transplanted throughout the year, spring and summer are the transplanting and growing seasons for Potamogeton crispus, and April to September is the transplanting and growing season for Hydrilla verticillata.

　　 Vallisneria natans (Lour.) Hara The leaves are basal, linear or strap-shaped, 20-200 cm long, 0.5-2 cm wide, green or slightly purplish-red, often with brown stripes and spots, apex obtuse, margin entire or with indistinct fine serrations; no petiole.

　　It is relatively heat-tolerant and alkali-tolerant, and has a strong ability to adapt to wind and waves. The biomass is densely distributed on the bottom, growing in a rosette pattern, with the growing point below the mud surface, and branches growing from axillary buds in the mud. The light compensation point is very low, and it can adapt to low light conditions well.

　　 Vallisneria

　　 Ceratophyllum demersum L. Leaves are in whorls of 4-12, 1-2 times dichotomously branched, segments filiform or filiform-linear, 1.5-2 cm long, 0.1-0.5 cm wide. Ceratophyllum is rootless, and the whole plant is submerged in water, so its growth is closely related to light. Ceratophyllum is a nitrogen-loving plant, and it grows better in water with high inorganic nitrogen content. Ceratophyllum is suitable for water depths within 1 m.

　 Ceratophyllum

　　Hydrilla verticillata (Linn.f.) Royle has branched stems; leaves are whorled, linear, thin, and sessile. Hydrilla removes more than 70% of NHs-N, TP, and COD, and effectively increases dissolved oxygen. Hydrilla can be used to restore lakes and polluted rivers with low flow rates. Furthermore, hydrilla is a favorite food of fish, shrimp, and crabs.

　　 Hydrilla

　　 Myriophyllum verticillatum The stem is smooth and cylindrical, with rhizomes growing in the mud; leaves are whorled, sessile, and filiformly dissected. Egeria densa has strong adaptability and can develop well in various water bodies. It is a light-loving plant and, compared to other submerged plants, has a higher rate of photosynthesis, capable of forming a dense canopy on the water surface that prevents light penetration.

　　 Egeria densa

　　 Part 4: Restoring the "Underwater Forest" - Methods and Strategies

　　 Reduce nutrient concentration in water Pollution source control is a prerequisite for ecological restoration and a very effective means of reducing nutrient levels in water. After pollution source control, relying on the water body's strong self-purification and sedimentation functions, the nutrient concentration in the water will be significantly reduced.

　　 Improve water transparency Transparency is a comprehensive reflection of the amount of phytoplankton and inorganic suspended matter, affected by physical, chemical, and biological factors. Measures to reduce phytoplankton and sediment resuspension can improve water transparency. For example, aquatic plant floating beds and terrestrial plant floating beds can reduce nutrient concentrations; creating enclosures can reduce sediment resuspension.

　　 Remove omnivorous and herbivorous fish This measure has two aspects: it can eliminate sediment resuspension caused by fish foraging in the sediment; and ensure that submerged vegetation is not grazed in the initial stages of restoration in heavily polluted waters.

　　 Dredging and substrate restoration Dredging is an effective measure to prevent the release of phosphorus from the sediment. Substrate restoration includes the restoration of soft and hard substrates in the littoral zone and micro-water areas, which will be beneficial to the construction of different types of aquatic plants in the littoral zone, such as emergent, floating-leaved, and submerged plants.

　　 Lower the water level Under controlled conditions, this can improve the photosynthetic conditions of submerged plants and is an effective measure for restoring submerged plants.

　　 Use soft enclosures to create a calm water environment Using soft enclosures to reduce waves in small lakes or parts of lakes can effectively create a calm water environment and prevent sediment resuspension caused by wind and waves.