Aquatic Environments

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Aquatic EnvironmentIntroduction:The majority of the earth’s surface is covered of water. Nearly ¾ % of the earth is made up of hydrosphere. The on going water cycle brings in lot of minerals to the oceans, seas and the rivers. The input of the various nutrients and biogeochemical cycle enriches the water with the nutrients. This input of the nutrients in the fresh and marine environments supports the microbial community in its niche. The organic matter accumulated in the ocean sinks into the d

Text of Aquatic Environments

Aquatic EnvironmentIntroduction:The majority of the earths surface is covered of water. Nearly % of the earth is made up of hydrosphere. The on going water cycle brings in lot of minerals to the oceans, seas and the rivers. The input of the various nutrients and biogeochemical cycle enriches the water with the nutrients. This input of the nutrients in the fresh and marine environments supports the microbial community in its niche. The organic matter accumulated in the ocean sinks into the depths of the earth creating nutrient rich environment. This nutrient rich environment stimulates the growth of the microbial community. About 98% of the earth is covered by the oceans. the study of marine microbiology began in the latter part of the 19th century. The Galathea Expedition under taken under the guidance of Danish government mainly dealt on the study of the marine ecosystem. The expedition was also an eye opener since many types of microorganisms were discovered. There were total of three expeditions of which the third took place in the year 2006 the largest one. All these experiments were focused on the distribution of the micro organisms in the marine environments. The recent research analysis shows that the study of aquatic microbiology has been diverted from the content to the contribution analysis. The study is more oriented in finding out the involvement of microorganisms in the biogeochemical cycles, microbial symbiosis nitrogen-fixing bacteria in boring mollusks, photosynthetic organisms in corals, and sulfuroxidizing bacteria in hydrothermal-vent organisms, have shown the widespread occurrence of marine symbiosis. Chemoautotrophic bacterial populations at deep-sea vents in symbiotic associations with the giant hydrothermal-vent tube worm, Riftia pachyptila. The temperature and pH also plays a major role in life of the organisms. Hence the organisms living in different depth are accustomed to adopt for different temperature and pH. The temperature can range form -5 to -150 c and 1130 c in geothermal areas. The significance of these obligate pycrophilic microorganisms and their survival at extreme pressures, as starvation survival and feast or famine in the oligotropic conditions opens our horizon towards a broader perspective in marine microbiology.

Aquatic Environment:The aquatic environment involves rivers, streams, lakes, seas and oceans. Each of the following has its own type of environment. They have their own size, geographical location physical and chemical character. Sunlight, temperature, aeration, and dissolved nutrient content differe based on their developmental zones. Another factor which contributes the environment is the constant mixing and movement of the dissolved organic matter. The rivers and streams will be more fed with the nutrients washed away form the land because of the rain. This type of aquatic system varies according to the seasons and the availability of water. The lakes are stratified vertically into 3 zones or strata: photic zone surface to lowest limit of sunlight penetration where most of the phototropic bacteria grow using co2 and sunlight. aphotic zone edge of the photic zone to lake sediment. heterotrophic benthic zone organic debris and mud forming the basin

I the above two zone of the aquatic environment the aphototropic bacteria which use sulphur, hydrogen sulphide, carbonates, nitrogen and other organic nutrients. Stratified horizontally into 2 zones: littoral zone shoreline, relatively shallow water which is rich in dissolved organic matter. pelagic zone open, deeper water which consist of aphotic and heterotrophic benthic zones This example holds good even for the sea and marine environment where the only exception is that the salinity pH and the temperature varies with that from the lakes. The stratification in the ocean habitat can be called as pycnocline which means rapid change of density with depth. It can be explained as follows. Isopycnal surface of constant potential density of water, thermocline buffer zone between warmest and coolest layers; ordinarily prevents the mixing of the two, halocline vertical salinity gradient, thermohaline temperature and salt concentration, and chemocline warmer and cooler water meet. Along with these there are estuaries, the meeting point between the rivers and seas or oceans where fringing vegetation such as grasses and mangrove species are vital to the input of nutrients. It is also calls as brackish environment which means the water is salty from the river water and less salty from the marine water.

Gases :The two gases of major importance in aquatic environment to microorganisms are oxygen and carbon dioxide, while nitrogen, methane, phosphorous and other trace gases are of secondary importance. Microorganisms are involved in most of the geochemical cycles in the oceans..

OxygenThe oxygen cycle is maintained in tow ways. One is by direct interaction between the atmosphere and hydrosphere, secondly by the constant interaction of the cyanobacteria leading to the evolution of oxygen. The solubility of oxygen in aquatic environment is low with high temperature and low pressure. The use of oxygen by the aquatic organisms from the water leads to the formation hypoxic or anoxy zones. These zones allow specialized anaerobic organisms, both chemotropic and phototropic microorganisms to grow

Carbon Cycle:The carbon dioxide being the second important gas in the aquatic environments maintains the pH of the water. The carbon-bicarbonate controls the weak or strong buffered areas. The use of carbon by autotrophic organisms increases the pH of the water. The inflow o carbon takes place through various processes. The water washed from the land contains dissolved organic carbon; the weathering of rocks ads carbonates the water, the dead and decaying organic matter. Oceans also absorb nearly 30-35% of the atmospheric carbon directly. Planktons play a major role in the activation of the carbon cycle. They act like a pump to transport the gases from the surface to the deep. The planktons absorb carbon and store it like a sink unlike the plants. Most of the gas escapes to the air or it is transported into the depths via dead plants, body parts faeces and other sinking materials. Marine snow, known as particulate organic carbon (POC), serves as a vehicle for vertical flux of organic matter and enriched hotspots of microbial respiration and sites of rapid turnover of particulate carbon in the sea

Nitrogen Cycle:The nitrogen fixation in the aquatic environment is done by cyanobacteria and bacteria. The heterocysts present in cyanobacteria fix nitrogen and carries out the formation of nitrogenous compounds. Nitrogen fixation in these organisms requires photosynthetic activity

which means it is light mediated reaction. The recent discoveries show that there are microorganisms which fix nitrogen in the aquatic environments. In the aquatic environment assimilation of nitrogen by the autotropes takes place in two ways: assimilation of dissolved nitrate, nitrite or ammonia and dissolved molecular nitrogen which is converted into dissolved inorganic nitrogen. The heterotrophic bacteria uptake nitrogen which is either organic or inorganic. Dissolved organic nitrogen is a heterogeneous group of organic compounds which is present as urea, ammonia, amino acids, humic and fulvic acids. Yet large group of microorganisms including protozoa, bacteria and algae assimilate low molecular weight nitrogenous compound directly. Some of the organisms which fix nitrogen are Aphanizomenon, Anabaena, Gleotrichia, Nodularia, Cylindrospermum, Synechococcus and Nostoc

Phosphorus Cycle:Phosphorus is the essential element in all the living systems. It is the structural molecule of the cell, storage component and it is also involved in energy transformation. It is present in the aquatic environment as dissolved organic matter, soluble and insoluble organic matter. The phosphorus taken up by the phytoplankton moves through internal loading to the food chain or gets sediment at the bottom of the sea as dead algal cells. The phosphorus which entered the food chain returns back as biomass. In both the cases it ultimately passes back to the water column. Phosphorus dose not have a gaseous cycle. The lack of phosphorus is compensated by nitrogen in the aquatic environment. Phosphorous is also added from the external environment through the runoff water.

Methane cycle:Methane thus is ideal microbial waste product. It is produced under anaerobic conditions. It is released vertically to the environment through water column through oxidation and reduction by bacteria. Hence there is very less toxic waste created by microbes. The methanogenic bacteria use hydrogen and carbon dioxide to give methane. Even the Sulfatereducing bacteria outcompete methanogens for substrates, inhibiting methanogenesis

Nutrients:The nutrient taking rates in the in the aquatic environment depend on the type of environment under study. The nutrients in take in marsh and esturain environment have a rapid rate of nutrient turnover than that of the marine environments. The estuarine and marsh environments are rich in C: N: P ratio which forms the larger breeding ground for the micro

organisms. The oceans cover the large area and the water in flow dose not meet the needs of the marine flora which makes marine environment different from that of fresh water environment. The microbial loop plays a major role in the circulation of the essential nutrients required by the aquatic organisms. The communities involved in the microbial loop are nanoplanktonic algae, microflagelates, picoplanktonic and phytoplanktonic microorganisms. The microorganisms are the major contributors of the nutrients as they convert the organic nutrients and dissolved organic matter into living biomass and particulate carbon which can be calle