Guide to Different Types of Pond Ecosystems and their Inhabitants
As the natural world is so diverse, both small and large-scale habitats have highly varied features. This makes each one suitable for nurturing a unique combination of relationships – an ecosystem. Ponds are vital sources of water for animal and plant survival, and they serve as shelters for thousands of species across the globe. Oftentimes, they become final frontiers of wildlife in increasingly urbanized and fragmented areas.
Essentially, a pond is a lentic ecosystem, which means that it is a relatively still and enclosed body of water. What differentiates it from other lentic bodies (e.g. lakes, marshes, swamps) are its depth and the extent of light penetration. Ponds tend to be quite shallow, which means that light is able to sustain aquatic life in its deepest zones. It becomes a full-fledged ecosystem when it is present for long enough to house a complex web of organisms and their basic needs.
Pond ecosystems are extremely important due to their contributions to biodiversity. Moreover, they are key sources of hydration for both plants and animals. Depending on their location, longevity, and abiotic components, they can be differentiated from one another. Each type of pond ecosystem below plays a role in the connectivity of life and tells its own natural history.
1) Garden Pond Ecosystem
If you’re accustomed to a more urbanized way of living, this would perhaps be the type of pond that you are most familiar with. Though it may be artificial in nature, its complexity can increase over time to accommodate a self-sustaining ecosystem. The components of this type of pond are often curated to achieve a particular theme. Thus, both plants and animals may have native or non-native origins.
Garden ponds can be classified further into ornamental or wildlife ponds. Ornamental ponds are usually fully lined and equipped with machinery to keep the water clean and clear. These may house highly prized and imported fish species, such as koi and goldfish, along with a varied selection of floating and marginal plants. Features that double as aerators (e.g. fountains, waterfalls, spitters) can enhance the overall appeal.
Wildlife ponds are made to attract fauna that can significantly contribute to the garden’s diversity. These are usually fully naturalized with native grasses and wildflowers that serve multiple purposes: they facilitate the safe entry and exit of small animals, they attract a wealth of pollinators that help mediate the reproduction and dispersal of plants, and they play an important role in carbon cycling and oxygen production in the pond.
Although these types of pond ecosystems are man-made, they become safe havens for wildlife in an increasingly hostile world. The enjoyment that they provide pond owners is also unparalleled. Ownership of a garden pond does come with responsibility. The pond’s contents can directly impact the surrounding environment, so ample research and decision-making must be done prior to pond construction.
2) Freshwater Pool Ecosystem
This type of ecosystem is often the result of water accumulation due to rainfall and flooding. They can also be caused by the creation of canals and dams, natural depressions in the ground, or the reorientation of river flow. Natural ponds can often start off this way – as small pools that accumulate more and more water over time. As water settles, it can change the substrate properties beneath and around the pool. This induces an ecological shift that favors moisture-loving animals and plants.
Freshwater pools eventually house an abundant and diverse community of decomposers, which significantly contribute to carbon and nitrogen cycling in the pond. Bacteria and primary producers break down organic matter that settle onto and line the pool bottom. Their presence has a bottom-up effect on the food chain. This means they tend to determine which higher forms of life (secondary consumers) are able to survive in the pool.
Most amphibians and insects with aquatic life stages require this type of pond to survive. The breeding stages of each generation may even repeatedly return to the same pools to lay their eggs. Hatching success and larval survival would then be controlled by limiting factors, such as space and food availability. Terrestrial animals also rely on freshwater pools for water and food.
3) Salt Pond Ecosystem
A highly specialized ecosystem, the salt pond makes a frequent appearance along the coastlines of tropical and temperate zones. It is characterized by a combination of both freshwater and marine properties. It thus acts as a type of buffer that facilitates the transition between contrasting environments. A constantly fluctuating water chemistry and pond depth are largely influenced by rainfall, wave action, temperature, and runoff from land-based sources.
As a result, the animals and plants that live in salt ponds must be adapted to a wide range of physical parameters. They must also tolerate spikes in salinity and calcium carbonate concentrations. Brackish water or estuarine species are best suited to this type of environment. Migratory and shorebirds have a tight-knit relationship with salt ponds because they can safely rest and feed in their waters.
In tropical regions, expanses of mangroves serve as natural barriers to salt ponds and aid in stabilizing their water properties. Unfortunately, the development of coastal areas into industrial zones and touristic beaches has resulted in major losses of mangrove beds and salt ponds. Their priceless ecosystem services, such as protection from storms, accumulation of terrestrially-sourced nutrients, and production of beneficial bacteria, have been compromised in many parts of the world.
4) Ephemeral or Vernal Pond Ecosystems
Ever notice the small bodies of water that form after extended periods of rainfall? These pools can briefly support their own ecosystems with simple to complex food webs. Those that occur in natural depressions of rainforests and wetlands can sometimes persist for more than half a year, becoming parched after extended dry spells each summer.
Vernal pools are highly variable in size. If rainfall levels through winter and spring are considerably high, they can form expansive pools that are connected to each other by drainage points called “vernal swales”. Water usually settles in these expanses because of the substrate type, such as packed clay or bedrock, and natural slope.
Vernal pools can evaporate several times a year. The plants and animals that thrive in them tend to have life cycles that are timed with the accumulation of water. They also require adaptations (e.g. the ability to become dormant, estivation periods, deep roots) that will help them survive through extreme periods of flooding or droughts.
Remarkably beautiful in spring, vernal pools will usually be lined by row upon row of wildflowers. They are an extremely important and dynamic resource that many animals rely on for clean water each year. These sprawling freshwater ecosystems can quickly transform into barren and dry plains each summer, becoming a testament to the role of seasonal variation in ecology. Threats to vernal pool ecosystems are now rampant due to climate change and land conversion.
5) Underground Pond Ecosystem
Among all types of pond ecosystems, this one is likely the least researched or discussed due to its rarity and location. Underground ponds are freshwater bodies that are, simply put, found beneath the ground. They house complex ecosystems in subterranean caves and are usually associated with springs, aquifers, or river complexes with an underground component.
These mysterious habitats are the exception to the rule when it comes to light exposure in a pond. They can fully be cast in darkness or have minimal light exposure from gaps in the overhanging structure. Thus, the energy input in this unique ecosystem has to do with specialized organisms – those that are able to survive and cycle nutrients without sunlight and with potentially minimal oxygen levels. These include a wide variety of oligotrophic bacteria, which are experts at acquiring and breaking down nutrients in nutritionally poor environments.
A perfect setting for a Lovecraftian novel, the underground pond remains to be an avenue for promising research. Many cavefish, salamanders, insects, amphipods, isopods, and other creepy crawlies make cave ponds their home. Unique adaptations include the lack of pigmentation, regressed traits (e.g. loss of eyes, slower metabolism), and a highly sensitive sense of smell. Some cavefish species may have a heightened capacity for red blood cell formation, allowing them to efficiently use available oxygen.
6) Kettle Pond Ecosystem
This is another rare ecosystem type due to its restriction to glacial regions. When large patches of stagnant ice detach from a main glacier, they can become carried off to plains where they will eventually settle. Over time, they become buried as they melt, forming a considerably sized depression in the ground. Once water accumulates and fills the depression, the resulting body is referred to as a “kettle”.
The sediment trapped by the glacier, with its own combination of microbes and gases, is released into the developing pond. These influence the types of vegetation and animal life that gradually accumulate in the pond, establishing its diversity profile.
Kettle ponds are quite shallow and small, seldom exceeding a depth of 10 meters and a diameter of 2 kilometers. Some kettles experience periods of seasonal dryness, in which case they may also be considered ephemeral pools. They usually receive additional water from rainfall or from a groundwater table. When water is sourced from a river or stream instead, they automatically become reclassified into “kettle lakes”.
7) Aquaculture Pond Ecosystem
Aquaculture ponds are man-made ecosystems. They are used to breed and grow fish or crustaceans for consumption, ornamental use, or as stocking material for seeding lakes. Features of these ponds vary according to the species being reared and the intensiveness of production. Extensive fish pond systems, which are usually situated along coastal areas, tend to be more ecologically diverse than intensive systems. This is due, in part, to their full exposure to outdoor elements.
Many modern aquaculture farms attempt to keep their ponds bio-secure. This means that they may apply additives that prevent the growth of animals and plants other than the desired species. That being said, a fully sterile pond can usually only be achieved indoors, in facilities that make use of multiple filtration steps as a means to remove most microbial life from the water. In this case, the “pond” may no longer be considered an ecosystem.
Important Features of a Pond Ecosystem
Every pond ecosystem consists of the features listed below. Each of these is associated with its own properties and can sometimes be referred to as a microhabitat. Depending on the niche an animal or plant occupies, it may regularly come into physical contact and may biologically interact with organisms of at least one or all zones.
Pond occupants that are found higher up the food chain (i.e. secondary consumers) are more likely to explore all areas of a pond in search of food. Terrestrial visitors may be restricted to a pond’s margins.
- Pond bottom (benthic zone) – Natural ponds with an actual substrate and submerged plants have very diverse pond bottoms. As fish waste and detritus tend to settle here, this is where most decomposers, opportunists, and scavengers may be found. In deep ponds, benthic zones may have markedly low light and dissolved oxygen levels.
- Water column – This can be further subdivided into the following increasingly deep layers: epilimnion, thermocline, hypolimnion (or profundal zone). Shallow pools may have a singular layer as the water column is unlikely to have differences in temperature, pressure, and light levels. Horizontal divisions of the water column include the littoral zone (shoreline) and limnetic zone (open water).
- Pond surface – Oxygen and light enter the water column through this fine division between the water column and air. The amount of light that can enter through the surface significantly influences algal concentrations and photosynthetic rates in the pond.
- Pond margin – Characteristics of the shoreline determine which organisms can enter and exit the water. The margin also serves as an entry point for runoff, which can carry nutrients and debris into the pond. Recreational use of a pond and climate change can alter the structure of shorelines and diminish protective vegetation.