Backyard ponds and lake come in a variety of shapes and sizes. They can be a small backyard pond that is just a fraction of an acre, or as large as several hundred-acre lake, and anywhere in between. Some are man-made, and some are natural bodies of water.
Many backyard ponds, farm ponds, and lakes do not have water quality problem prevention management. The few that are managed, typically are only managed for fixing water quality issues instead of preventing the problem. If not addressed, this can accelerate the aging process and eventually lead to the death of the pond or lake.
There is a natural aging process that ponds and lakes go through, and the erosion process fills in the low areas with eroded earth from the higher areas. This progression causes the pond or lake to fill up. Pond or lake has many zones or segments. Getting to know these zones along with having a general idea of the aging process will help you to manage your pond and slow the aging process.
Pond and Lake life cycle
Ponds or lakes are typically in one of these stages of life, listed from youngest to oldest – Oligotrophic, Mesotrophic, or Eutrophic.
Oligotrophic waterbodies are considered as new or young ponds or lakes. Oligotrophic waterbodies have a lower concentration of nutrients like nitrogen and phosphorus. Typically, they have steep sloping shorelines and are deep with clear, healthy water. Normally the bottom of these ponds or lakes is made up of sand, gravel, or rock. Oligotrophic lakes do not produce a lot of aquatic plants or algae since they have little nutrients in them, so they require less maintenance for water quality problems.
Mesotrophic waterbodies are middle-aged ponds or lakes. Mesotrophic ponds or lakes contain more nutrients than Oligotrophic waterbodies and, therefore, they have more aquatic plants and algae growth. When a pond or Lake ages from Oligotrophic to mesotrophic, the edges of the water body begin to slope lasts, and the bottom of the pond becomes filled with more organic material. The substrate that was once sand, gravel, and rock now contain a layer of mud on top of the rocks. Mesotrophic ponds or lakes will require regular maintenance to slow down the aging process since they have more nutrients, producing more plants and algae.
Eutrophic waterbodies are old or dying ponds or lakes. Eutrophic pond and lakes contain high levels of nitrogen and phosphorus, which leads to an abundance of aquatic plant growth and algae blooms. The edges of the water body continue to flatten out as the pond or lake continues to age, filling the bottom of the pond with organic sediments and muck. This causes the overall depth of the pond or lake to decrease, and the water loses its clarity. As the pond or lake continues to fill, the aquatic plants grow larger, and the water surface area will begin to shrink as well. If left untreated, eventually the pond or lake will fill in completely turning into a wetland or swamp. Many of the existing farm ponds fall in the eutrophic category and require additional maintenance to slow the aging process.
Pieces of the Pond and Lake Puzzle
Each pond or lake contains several segments that divide the water column from side to side and top to bottom. These zones are Littoral, Limnetic, Profundal, Euphotic, and Benthic.
The Littoral Zone of the water body is the shore area. This zone is the area containing the dry land sloping to the open water, which can be narrow or very wide. Normally, Oligotrophic or younger waterbodies have narrow littoral zones due to their steep edges, whereas eutrophic or older waterbodies have wider littoral zones due to the flat and slope of their shoreline. Littoral zones are shallow and receive a lot of nutrients from runoff and nonpoint source pollution. This will typically cause in abundance have aquatic plants and algae growth in this area. Other common Inhabitants in the littoral zone are reeds, cattails, snails, crawfish, insects, zooplankton, and small fish.
The limnetic zone is classified as the open water area of the pond or lake. This is a much larger segment of water in an Oligotrophic or younger pond or lake than it would be for a eutrophic or older waterbody. There are two segments within the Limnetic zone. The top portion of the limnetic zone that is towards the water’s surface is the Euphotic Zone or Epilimnion (warm water region). This section of the water body receives sunlight, and this section ends where sunlight cannot penetrate. The euphotic zone, along with the littoral zone is where aquatic plants and algae thrive. Typically, this is the area that contains dense fish populations due to the higher levels of oxygen from the contact with air.
Under the euphotic zone is the Profundal Zone or hypolimnium, which is the colder region. The Profundal zone is located under the thermocline, where sunlight cannot penetrate. The size of this zone will depend on the age of the pond or lake and clarity of the water. The profundal zone usually has lower fish populations due to lack of oxygen.
The last zone is the benthic zone, which is the bottom of the pond or lake, consisting of organic sediments and soil. The benthic sound acts as a digestive system for the pond or lake. This zone contains bacteria that decompose organic matter from dead aquatic plants, algae, and fish waste. The more organic matter in the water body, the more decomposition takes place. Decomposition can happen aerobically (when oxygen is present) or anaerobically (with no oxygen). Arabic decomposition is ideal because it has a quicker process, and byproducts are easier to handle. The benthic zone increases as the water body ages.