Pond water

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=Introduction

A pond is a body of freshwater smaller than a lake.   Ponds are naturally formed by a depressions in the ground filling and retaining water. Streams or spring water usually fed in to these bodies.  They are also be man-made ponds which can be created by damming a stream, digging a hole. Ponds are usually land locked and have no outflow. Because of this they are considered to be self contained ecosystems.  This ecosystems are often teeming with rich vegetation and diverse orgamismal of life.

Description of Niche

Ponds can be very different from one another depending on their location and climates. Temperatures can vary from moderately warm in the summer to completely freezing over in the winter. Usually ponds have a pH of apporximatly 7 but can be as low as 6 and as high as 10 depending on many factors. Ponds with large populations of algae and other aquatic plants can change a pond's pH depending on the time of day. These organisms take up more dissolved carbon dioxide through photosynthesis during the day and and emit carbon dioxide at during the night though respiration. More carbon dioxide helps maintain pH at around 7 by dissociating in to bicarbonate ions. With a large organic demand for carbon dioxide, the bicarbonate ion concentration and thus buffering capacity of the pond can be significantly reduced and the risk of a rapid pH change increased. Composition of water is murky if it has a high amount of suspended particles and/or organisms. The bottom ofa pond is usually sediment of sand, decaying matter and microorganisms. Pond water is usually stagnant. Nutrients are brought to the pond the streams that feed into it or run off during rain or snow melt off of the surround terrain. This washes in soil, aminal waste, and decaying plant matter into the pond where they are broken down and used to fuel the ponds ecosystem. Many animals that live in the surround area, migrating birds, and near by plants depend on ponds for a rich source of nutrients and water.

Who lives there?

Ponds have a wide variety of microbial life. According to 2000 study, ponds have an average of 184.5 different types of micobs. Different levels of dissolved oxygen and light are present at different depths in the pond. This leads distinctly different niches from green algae and cyanobacteria on the surface to sulfate and methanogens on the bottom.

Anabaena These pearl shaped cyanobacteria are photoautotrophs. They can are able to synthesize their own sugars using carbon dioxide in the are and sunlight. They have been found to form sybiotic relationships with plants such as on the underside of Azolla ferns and other microorganisms. This bacteria is extremely valuable to the ponds ecosystem because of it's rare nitrogen fixing ablility. All organisms need a source of nitrogen to survive but very few can make their own from nitrogen gas in the air due to it's chemical structure. Anabanea can take dinitrogen and convert it in to ammonia which then can be used as a nitrogen source by other organisms. For this reason, they are often used in rice paddies to help fertilize the plants.