The Biodiversity of Organisms Found in Curtz Pond Littoral Photic and Littoral Aphotic Zones
Organisms living in a pond community choose areas based on light, temperature, oxygen, and availability of nutrients. A pond can be broken down into zones based on the amount of light, ambient temperature, oxygen present and the amount of organic or inorganic compounds.
These areas are the open water, the shore area among the weeds, and the bottom of the pond in the mud.
The open area is called the Limnetic Zone. The shore area containing emergent plant life, is called the Littoral Zone. Both the Limnetic Zone and Littoral Zone can be separated into the surface waters and the muddy areas at the bottom. The muddy area at the bottom is called the Benthos.
Lentic environments, or standing water habitats, are not only broken down by areas but by the amount of light and temperature in each.
The Benthic Zone consists of mud and decomposing organic material. This area is below the level of light and contains little to no oxygen. This is called the Aphotic region due to the lack of light present and is also referred to as the hypolimnion which refers to its temperature.
When referring to plant life, the Lentic environment can be broken down into the Trophogenic Zone, where photosynthesis occurs, and the Tropholytic Zone where decomposition occurs.
The purpose of observing the differences in Biodiversity between the Benthic, Aphotic, and Photic Trophogenic regions, in the Littoral zones of a Lentic environment, is to analyze areas that are in close proximity of each other. Hopefully, through this observation one can see the extreme difference of life in a microcosm.
Curtz Lake CA
Two water samples were collected from Curtz Lake, located outside Markleeville CA. Both samples were collected in an area heavy in emergent plant life, mostly Duckweed, on the shores of the lake.
The first specimen was collected from the murky surface waters in the Littoral region.
The second specimen was collected from the muddy area on the bottom or the Benthic Zone.
The distance between the surface water and the mud measures five centimeters.
The mixture of mud and water from the Benthic Zone was collected amid many roots of emergent plants, while the surface water was collected in close contact with the stems of the plants.
The specimens were then mixed well and a small sample was analyzed under a standard light compound microscope. Two slides were examined from each specimen.
One hundred organisms were examined from each slide. After examination the organisms were differentiated and named. A list was made of all organisms present.
Community A were the organisms found in the Benthic Zone while Community B were the organisms found in the Littoral Zone. Each Community was counted to determine species richness and the Simpsons Index (ds) was used to determine distribution of the species.
Community A had a theoretical maximum diversity of 0.929 while the ds value was 0.8043. So the ds value had approximately a 10% variance from the hypothetical diversity. There were fourteen different species identified in the Benthic Zone samples, mostly Green Algae. The number of the species in the Benthic Zone also contained some macroscopic Damselfly Larvae, Water Boatmen Larvae and one species of snail. Seventeen unknown ciliated protozoa were also identified in the Benthic Zone. Eight unidentified motile non-segmented worms were also counted in the Benthic sample.
Community B had a theoretical maximum diversity of 0.917 while the ds value was 0.6336. The ds value had approximately a 30% variance from the hypothetical diversity. there were twelve species identified in the Littoral Zone samples, mostly Green Algae. The Littoral region contained one Damselfly Larvae.
Community A in the Benthic Zone had a more diverse community than that of the Littoral Zone.
The Littoral Zone had organisms that would not thrive in the mud due to lack of oxygen and the lack of sunlight.
From looking at the organisms counted in the sample, one could conclude that unknown flagellated Protozoa, Diatoms, species of Algae including Schizomeris leibleinii, Stigeoclonum lubricum, Heteronema spirali, Closterum acerosum and Desmids desire more oxygen and light for photosynthesis than the species in the Benthic Zone.
There was not as diverse a community of organisms in the Littoral zone than that found in the Benthic Zone.
In the Benthic Zone was found macroscopic Damselfly Larvae, a snail, and Water Boatmen Larvae. There were five different species of Algae identified in the Benthic Zone; Euglena sangeria, Wislouchiella planctonica, Ammodiscus incertus, Binuclearia tatrana, Phorridium groesbeckianium.
So why was the Benthic Zone more diverse?
The Larvae present was found in the muddy area because the Damselfly and Water Boatmen eggs are laid on the stems of the Duckweed where the specimens were collected.
The snail not only fed on the algae but also on the detritus, or the broken down organic substances found in the Benthic Zone.
If Gram Stains were performed on the Benthic slide one would see many anaerobic bacteria that catabolise dead organic material for the nitrogen necessary to their metabolism.
The diversity of Algae in the Benthic Zone is explained by the use of HCO3 by some Algae to acquire the needed carbon and oxygen necessary for metabolism. Some Algae catabolise CaCO3 with addition of water into Ca ions and HCO3.
This increases the alkalinity of the muddy area and the water.
Also Algae require nitrogen, so they use the nitrogen in the detritus and any human nitrogenous waste products that may have been polluting the pond, from irrigation run-off or waste water run-off.
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