Aquatic ecology and Biodiversity

Unit 9- Freshwater environment

9.3.1. Lentic habitat

Ponds and lakes are bodies of standing freshwater surrounded by land and are not having continuity or connection with the sea. Lakes tend to be larger and deeper, while ponds are often shallow enough that sunlight can reach the bottom allowing rooted plants to grow. There is no clear cut difference between the lakes and ponds except for the size, but they very well behave differently in their ecology.
Ponds

Ponds are very shallow in nature and its average depth may be about 8-10 feet with some exceptions. Since the ponds are shallow, the light penetrates up to the very bottom. In ponds, water temperature is fairly uniform from top to bottom. It changes with air temperature. There is little wave action, because the water is shallow. The bottom of a pond is usually covered with mud. The amount of dissolved oxygen in a pond may vary greatly during a single day. The level of carbon dioxide and other gases is more in the bottom of the ponds as the decomposition process prevails in the bottom. In very cold locations, an entire pond may freeze and form ice.
Based on the origin, the ponds can be of natural types and artificial types. Natural ponds are formed either due to the ageing of the lakes or filled with accumulation of rain water in the natural depressions that occur on the earth surfaces, where as the artificial ponds are man-made ones. Further, ponds are classified into temporary and permanent ponds depending on the duration of availability of water.
• Temporary ponds
• Permanent ponds:
Lakes
Lakes are bigger than ponds and too deep to support rooted plants except near the shore. Some lakes are deep enough and wide enough for waves to form. For example, the Lake Superior is the largest freshwater lake in the world, with a water spread area of 31,000 square miles. Similarly, the Lake Baikal in the Southern Siberia, is the deepest lake in the world, which has a depth of 1,700 meters.
Zonation of lakes and ponds
Lakes and ponds are divided into three different "zones” namely littoral, limnetic and profundal zones, which are usually determined by depth and its distance from the shoreline.