While accounting for only 3% of the Earth's surface, lakes and ponds are vital habitats, and provide essential resources for a wide range of species, including humans. Like zones for plant hardiness there is also 3 zones for life at different levels in a pond or lakes. These zones support different life forms for each zone. We have all seen it but maybe never thought about looking at it with this perspective. We will break down each zone as:
- Littoral Zone
- Limnetic Zone
- Profundal Zone
The Limnetic zone is the layer of open water where photosynthesis can occur. The near-surface open water surrounded by the littoral zone is the Limnetic zone. The limnetic zone is well-lighted (like the littoral zone) and is dominated by plankton, both phytoplankton and zooplankton. Plankton are small organisms that play a crucial role in the food chain. Without aquatic plankton, there would be few living organisms in the world, and certainly no humans. A variety of freshwater fish also occupy this zone.
Very deep lakes have an area known as the Profundal zone where light does not reach. This zone is inhabited by organisms that are either attached to or crawl along the sediments at the bottom of the lake. The sediments support a large population of bacteria and fungi. The decomposers break down the organic matter and release inorganic nutrients.
Most of our ponds are not deep enough to have the Profundal zone, but none the less we do have the same decomposing break down going on but at a lesser depth. Just as an organism has a particular home, or habitat, it also has a certain job to perform in the community. All organisms may be classified into one of three categories. Organisms containing chlorophyll and therefore manufacturing their own food by photosynthesis are known as producers. Organisms that feed directly upon the producers and upon organisms are known as consumers. These organisms are unable to manufacture their own food. Bacteria and fungi that react upon dead matter and free useful compounds, elements, and minerals so that the producers may utilize them once again are called reducers.
|Photo supplied by "The Kansas State Emporia State University"|
The picture above gives a better perspective of the different levels were discussing.
There is one other level to look at Benthic zone. This is an interesting level as it can be found at shallower depths, there are many more photosynthetic microbes. At greater depths, microbes do not have access to light and heat and must rely on detritus for energy. The organisms in the Benthic zone are classified into those which dwell on the surface and those which burrow into the pond floor. We would find this more in mud ponds then in concrete or liner substrates. But none the less does occur in most ponds that may have detritus build up or some form of gravel or rock lining bottom. Benthic microorganisms are almost exclusively microalgae and bacteria, but other others include: ciliates, amoebae, and flagellates. In general, most organisms there are detritivores and scavengers because of the abundance of dead or decaying organic matter. In addition to these heterotrophs, there are chemoautotrophs present that use the substrate to make biomass. There are also photoautotrophs present at shallower depths where sunlight is abundant. The impacts of benthic microorganisms spread, much like the impacts of all other microbes, across the community as a whole. They provide essential energy and nutrients at the lower levels of the food chain and are imperative to the success of other forms of life.
So next time your out feeding your fish and trimming plants or just enjoying your Eco-system take minute and see if you can identify the Zones in your pond.
Until next time............Happy Ponding- Koiman
By: Jason T. Hoverman () & Pieter T. J. Johnson () © 2012 Nature Education