Aquatic Plants

Aquatic plants are equally beneficial for the pond water in which they are planted and the surrounding environment in which they are present. They provide oxygen to the pond fish, eliminate or absorb the excessive nutrients in the water, clean and clear the pond water, improve its aesthetics, and act as a shelter and food source for aquatic animals. 

All the Hydrophytes and Macrophytes (except Algae and Microphytes) are adapted to live in the saltwater or freshwater or on soil frequently saturated with water and are named “Aquatic Plants.” Macrophytes are the primary producers in the food chain, food source of some fish and wildlife. Aquatic plants such as submerged Macrophytes have particular morphological adaptations for living in water, and that is the “aerenchyma,” internal air packing cells.  

Different Types of Aquatic Plants based on Growth Habit:

The Depth and Duration of flooding decide which Aquatic Plant will survive in ponds, lakes, or rivers. The four different types of aquatic plants are mentioned below:

Emergent Plants:

The emergent vegetation roots into the water through its stiff stems and partially remain in the air because its leaves are adapted for photosynthesis more effectively in the air. Some examples of emergent aquatic plants and how they affect pond water quality is described below: 

• Cyperus papyrus (paper reed, Nile grass): Suitable for shallow water ponds. It has a long history of multiple uses like papyrus paper (the first paper ever made), food for wildlife, ornamental plants, etc. They efficiently absorb nutrients such as Nitrogen and Phosphorus before being utilized by the nuisance algae. Therefore, they are preferred for constructed wetland filtration systems. 
• Butomus umbillatus (Flowering rush): This emergent aquatic plant is becoming rare and needs to be conserved due to its remarkable phytoremediation properties.
• Lythrum salicaria (purple loosestrife): It is equally adapted for water-saturated, shallow water, damp, and drier conditions, grown in wetland filters (CWFS) and around ponds as an ornamental plant. It is a medicinal herb used in the treatment of diarrhea and dysentery etc. 

Submerged Macrophytes:

As the name indicates, submerged plants grow underwater with roots attached to the pond bottom or without any root system. Some of the commonly grown submerged aquatic plants in ponds or constructed wetland filters are: 

• Ceratophyllum demersum: this free-floating submerged plant is commonly called Coon-tail/Hornwort. This plant develops no root system and is a safe alternative to pond water purification. Its fluffy, spongy leaves provide comfortable cover for newly hatched fish. (Kulasekaran, Gopal, & John Alexander, 2014)
• Myriophyllum alterniflorum: the “Watermilfoil” forms thick mats in and on the surface of water that interferes with the recreational activities of lakes, narrowing space for the juvenile fish in ponds, blocking the sunlight to penetrate into the water, utilizing the nutrients needed for fish to grow hence increase the competition. In short, it dominates in the ponds for both space and food. (Newroth, 1993)
• Myriophyllum spicatum: named as “Eurasian watermilfoil” by local growers. It is native to Europe and Asia but widely grown as a pond plant in the US. Its capacity to grow from the broken offshoot parts makes it a problematic plant in the pond as it spreads rapidly to cover the pond space.
• Hippuric Vulgaris: Mare’s tales, native to North America. It is an oxygenating aquatic plant widely grown in ponds for a clean, healthy pond (absorbs, creates a protected environment for fish and wildlife.
• Echinodorus cordifolius (Mud-King, Creeping burhead): Native to Central and North America. It is widely grown all over the tropical and sub-tropical regions of the world due to its easy-to-grow and ammonia, nitrite, and nitrate removal characteristics. It can efficiently remove: 44.9-91.4% ammonia, 90.8-99.3% nitrite, and 55-89.75% nitrate. (Nakphet, Ritchie, & Kiriratnikom, 2017)  
• Typha latifolia (Reed-mace, Bulrush, Cattail, Punks, etc.): is an aquatic to semi-aquatic flowering perennial herb. Typha is a good Phytoremediator plant widely planted around ponds or wetland filters. Its rhizomatic root system absorbs Fe (highest absorption), Mn, As, Zn, Cr, Cu, Ni, Cd, etc., very efficiently. (Salem, Laffray, Al-Ashoor, Ayadi, & Aleya, 2017)

Floating Leaved:

• Nymphoides aquatic: commonly known as “banana plant or banana lily,” is the beauty of any pond, lake, or aquarium. Its growth rate is fast, efficiently absorbs the nutrients like nitrogen, phosphorus from the pond water acts as a water cleaner, and oxygenates the pond fish. 
• Nymphoides pelatum: the yellow floating heart of the Menyanthaceae, blooms in June and continues to produce beautiful flowers throughout the summer. (Stuckey, 1973)
• Potamogeton crispus: is an aquatic plant (Potamogetonaceae are collectively known as “pondweeds”) with either floating or submerged leaves. It is considered one of the crucial components of angiosperm’s food chain because of its importance as a food source for many aquatic animals and the habitat of water life.

Free-floating:

Free-floating aquatic plants do not have roots anchored in the substrate or bottom of the water body. The various effects of free-floating aquatic plants on the quality of pond water and the habitat (in which they are growing) are mentioned below:

• Salvinia minima (Floating Fern, Water Spangles): It grows on still waterways native to South America. It reproduces and spreads very quickly, forming a thick mat on the surface of pond water. Due to that, the amount of sunlight necessary for the growth of underwater plants decreased, ultimately decreasing the amount of Dissolved Oxygen in the pond water. (Dickinson & Miller, 1998)
• Pistia stratiotes (Water lettuce or Nile Cabbage): It outcompetes algae for food in the water and prevents excessive algal blooms. It can produce bioethanol (at the rate of 0.14-0.17ethanol/g biomass) and contribute to cleaning the pond water. It also absorbs excessive nutrients, including N, P, etc. In constructed wetland filtration systems, water lettuce is planted for sewage wastewater treatment (proven to be the cheapest method of sewage water cleaning). (Soda, Mishima, Inoue, & Ike, 2013) 

The importance of using Native Aquatic Plants:

Native aquatic plant species help preserve biodiversity and a balanced water body. 

• Easy to grow and maintain: native plants are well adapted to the local climatic fluctuations, water, and soil states. There is no need to create artificial conditions to grow them, synthetic pesticides to protect them, and no additional water requirements.
• Fight with Unwanted Pond Weeds: By planting healthy native aquatic plants beds, you can minimize the space for the weeds to infest. Chinese tallow (Triadica sebifera), Alligator weed (Alternanthera philoxeroides), Torpedo-grass (Panicum repens L.), Tiny Water Spangles (Salvinia minima), Hydrilla (Hydrilla verticillata), etc. are some of the plague weed species of aquatic plants in ponds. 
• Act as A Food Source for Aquatic Animals: forage fish, waterfowl, and aquatic invertebrates utilize native aquatic plants (seeds, flowers, stems, and fruit sometimes) as a food source. 
• Help improve water quality: a diverse combination of emergent, submerged, and floating plants means you have collected a variety of excessive nutrient absorbents at one place. They produce oxygen, absorbs the carbon dioxide and other gases produced by either fish or present in the air, at the same time hold the pollutants in their roots, stems, or leaves, and ultimately clean the pond water. 

The US native aquatic plants (suitable for all kinds of ponds, either shallow or natural earth bottom-ponds, etc.) are mentioned below:

• Thalia dealbata, 
• Golden Club,
• Sagittaria Latifolia, 
• Pickerel Cordata, 
• Variegated Water Celery, 
• White Calla Lilly, 
• Canna Cleopatra, 
• Canna Orange Punch, 
• Blue Flag Iris, 
• The locally available varieties are Louisiana Iris (Fortune Finder, Colorific, Red Velvet Elvis, Red-mood, Black Gamecock, etc.)

Ornamental aquatic plants:

• Ludwigia Sedoides (Mosaic Flower): it produces diamond-shaped leaves, thus named as mosaic flower. It has beautiful reddish-green leaves with reddish-pink shoots.
• Myosotis scorpioides (water forget-me-not): is an introduced species to North America, happily grow in ponds, bogs, swamps, etc.
• Cyperus alternifolius (Umbrella palm): it poses an elegant look in your pond by creating a soft backdrop for the smaller plants (its height goes up to 6 feet).
• Nelumbo nucifera (water lotus): you can name it “the beauty of pond” because of its soft-colored pinkish flowers that demand attraction from the viewers.
• Pontederia cordata (Pickerel pond plants): it produces beautiful ornamental purplish flowers, and the bloom is long-lasting. 
• Lobelia cardinalis (cardinal flower): native to Eastern and Western US, prefers the partial shady conditions, produced red-colored flowers. It is considered perennial, but it may be short-lived and has medicinal importance too. 
• Iris spuria (Blue Iris): the beautiful blue iris is the first to bloom in the spring. The genus “Iris” comprises hundreds of irises that have aquatic habitats.
• Acorus calamus (sweet flag): is an emergent to partially submerged aquatic pond plant. It is easy to grow and maintain kind of plant. It adds a bright, colorful spot in your pond with its light green leaves having yellow strips.
• Colocasia esculenta (Taro pond plant): a plant always makes a distinguished appearance in the pond is the Taro plant. This impressive water lover produced corms that are eatable. Taro plant has been planted for its phytoextraction properties in wetlands and ponds. (Madera-Parra, Peña-Salamanca, Peña, Rousseau, & Lens, 2015)
• Pontederia crassipes (water hyacinth): is a free-floating aquatic plant known for its fast-growing and eye-catchy flower colors. Water hyacinth has been studied a lot for its distinguishing phytoremediation properties. It is planted in constructed wetland filtration systems and ponds for the cleaning of kitchen wastewater as well as to reuse the pond water. (Parwin & Karar Paul, 2019)

The careful use of native aquatic plants in a body of water is the absolute best way to control water quality. Humans have been devising and developing many different types of ingenious and environmentally costly gadgets and poisonous chemicals in an attempt to artificially control water quality. The truth is and has always been that using aquatic plants and working on the side of Mother Nature is now and has always been the answer to healthy and clean water.

References:

Dickinson, M. B., & Miller, T. E. (1998). Competition among small, free-floating, aquatic plants. The American midland naturalist, 140(1), 55-67.

Kulasekaran, A., Gopal, A., & John Alexander, J. (2014). A study on the removal efficiency of organic load and some nutrients from sewage by Ceratophyllum demersum. L J. Mater. Environ. Sci, 5(3), 859-864.

Madera-Parra, C., Peña-Salamanca, E., Peña, M., Rousseau, D., & Lens, P. (2015). Phytoremediation of landfill leachate with Colocasia esculenta, Gynerium sagittatum, and Heliconia psittacorum in constructed wetlands. International journal of phytoremediation, 17(1), 16-24.

Nakphet, S., Ritchie, R. J., & Kiriratnikom, S. (2017). Aquatic plants for bioremediation in red hybrid tilapia (Oreochromis niloticus× Oreochromis mossambicus) recirculating aquaculture. Aquaculture International, 25(2), 619-633.

Newroth, P. R. (1993). Application of aquatic vegetation identification, documentation, and mapping in Eurasian watermilfoil control projects. Lake and Reservoir Management, 7(2), 185-196.

Parwin, R., & Karar Paul, K. (2019). Phytoremediation of kitchen wastewater using Eichhornia crassipes. Journal of Environmental Engineering, 145(6), 04019023.

Salem, Z. B., Laffray, X., Al-Ashoor, A., Ayadi, H., & Aleya, L. (2017). Metals and metalloid bioconcentrations in the tissues of Typha latifolia grown in the four interconnected ponds of a domestic landfill site. Journal of Environmental Sciences, 54, 56-68.

Soda, S., Mishima, D., Inoue, D., & Ike, M. (2013). A co-beneficial system using aquatic plants: bioethanol production from free-floating aquatic plants used for water purification. Water science and technology, 67(11), 2637-2644.

Stuckey, R. L. (1973). The introduction and distribution of Nymphoides peltatum (Menyanthaceae) in North America. Bartonia(42), 14-23.