Introduction
Aquatic environment range from Marine water to freshwater bodies. The Ecology of Marine and freshwater is similar in general, Some microbiologists consider that microorganisms of both aqua environments co-exist in estuarine and inshore environments. Algal blooms
In an Aquatic environment, photic life is very common where algae and cyanobacteria are of much greater importance in primary production than in terrestrial environments.
Role of Predation in controlling the bacterial population:
heterotrophic nanoflagelates are important consumers of bacteria and play major role in the regeneration of Nutrients. There is diversity of nanoflagelates and their relationship with their prey vary considerably. Bdellovibrio bacteriovorus have importance in restricted niches where the prey density is high. myxobacter, Lysobacter is algicidal and limit the extent of blooms.
Importance of bacteriophage:
The properties of phage are poorly understood in aquatic environment but it is consider that in water bodies viruses are the most numerous microorganisms. Bacterio phages not only limit the number of other micro organisms but also release the nutrients after lysing which are directly available to other organisms for utilization.
Phage activity which is lethal for the individual micro organism is beneficial for the microbial community as a whole and used in maintaining the nutrient availability. Viruses can control the structure of marine microbial communities levels below one infective unit per ml.
Blooms:
There are two types of blooms i.e Algal and Cyanobacterial blooms.
Algal blooms:
Algal blooms occur due to eutrophication, also because human activities especially increased levels of phosphorus and Nitrogen. Spring phytoplankton bloom in temperate and Arctic sea is a well known phenomenon. Blooms are predictable consequences of hydrological changes which increase the nutrient content of upper layer of water. The spring bloom occur due to the onset of the process of stratification and a high nutrient level due to vertical mixing coinciding with increased day length and quantity of solar radiation.
Control of Algal blooms:
under favorable conditions the growth of phytoplankton is exponential. ALgal blooms formation may be controlled due to herbivore grazing vut response is slow.permitting number raises to c 10^8 per ml. Numbers of Algal phages increase rapidly with increasing cel number and metabolic activity. Blooms are usually monospecific,
Recognation of Blooms
they are recognized visually by discoloration of the sea which may be green, brown or red depending upon the algae present. White blooms are the blooms that occur due to calcerous skeletal elements of coccolithophores, such as Emiliania huxleyi, while red tides are caused by dinoflagellates.
Ecological importance of blooms:
The higher levels organic compound produced by the blooms can have beneficial effect on the higher level of food chain. In many cases production of organic matter is so great that demineralization by bacteria consumes very large quantities of dissolved oxygen. Moreover oxygen consumption by the night time respiration of Algae leads to Anoxia and mass mortality among fish and invertebrates. fish can be killed by toxins and H ₂S production. The effect of blooms is more severe in closed systems, like, lakes, ponds etc.
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Cyanobacterial blooms:
cyanobacteria blooms are caused by cyanobacteria. They reduce light which may ultimately lead to the disappearance of larger aquatic plants piscivorous fish. Filter feeding fish become dominant which causes the disappearance of crustacean zooplankton, reducing the grazing pressure on algae.
Undesireable effects of blooms:
- They produces foul smelling
- loss of recreational value both for coastel and inland water
- Produces toxins, which either directly effect the man and animals entering the water, or indirectly through consumption of shell fish.
- Some algae produced toxins as antipredator strategies in supporting the bloom formation. Gymnodiniu catenatum is the example of toxigenic algae that spread geographically from California to Europe and Japan.
Bacterial blooms:
These are less visible than algal and cyanobacterial bloomand have less detrimental effect on environment.
image: SA Scientific American