MICROBIOLOGY AND PHYSICOCHEMICAL PROPERETIES OF HUMIC FRESHWATER ECOSYSTEMÂ IN UKAM STREAM IN MKPAT ENIN LOCAL GOVERNMENT AREA OF AKWA IBOM STATE.
CHAPTER ONE
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1.0Â Â INTRODUCTION
The services provided by freshwater ecosystems to all living organisms on our planet have been at the root of the development of the human race throughout the ages. Humans have learned by experience that a constant and reliable supply of clean water is fundamental to security of the species. Early settlements were located along major rivers, near lakes or springs, which provided not only water but also protein in the form of fish and other aquatic organisms, as well as transportation. Other areas were later occupied when people developed to access water in the dry season, canals to distribute water for agricultural activities over more extensive areas, and means to drain swampy or frequently flooded areas. What humankind took longer to realize was that the services being provided by freshwater ecosystems, such as clean water, proteins, and seasonal enrichment of floodplain soils, are the result of a suite of physical, chemical and biological processes that constantly take place in and around those ecosystems, and are an important component of the hydrologic cycle. Some of the processes are easily seen and understood, such as the deposition of nutrient rich sediments by seasonal floods; others are less visible, such as the purification of surface waters by microorganisms that decompose organic matter.
Humic substances (HS) are major components of the natural organic matter (NOM) in soil and water as well as in geological organic deposits such as lake sediments, peats, brown coals and shale’s.
They make up much of the characteristic brown color of decaying plant debris and contribute to the brown or black color in surface soils. They are major components of NOM in surface waters and at higher concentrations can impart a dark color, especially in brown fresh water ponds, lakes, and streams. In leaf litter or composts, the color may be yellowish-brown to black, depending on the degree of decay and concentration. Humic substances (HS) comprise the majority of dissolved organic matter in freshwater ecosystems. Their concentration exceeds that of all living organisms by roughly 1 order of magnitude (Wetzel, 2001; Steinberg et al, 2003). Because of the chemical building blocks and physicochemical behavior of HS, researchers have postulated that these substances have a xenobiotic(this is a foreign chemical found within an organism that is not naturally produced within that organism) character, particularly the irritation of membranes,  Only very recently, unambiguous evidence of the xenobiotic character of HS presented showed that they have the potential to act as herbicides ( this is a substance that is toxic to plant), (Steinberg et al, 2003, Pflugmacher et al., 2003).
Traditionally, humic lakes are associated with low productivity, species richness and phytoplankton population densities. Dissolved humic substances can influence the physical characteristics of ecosystems (light attenuation, reduction of pH values and nutrient availability), as well as biological aspects in terms of biological enhancing effects and adaptations in the plankton food web. Therefore, lakes with high concentration of humic compounds are identified as a distinct class of systems, easily recognized by their dark-colored water.
Most of the studies on phytoplankton of humic systems are restrict to stratified and deep temperate lakes. In tropical areas, there are very few studies on phytoplankton communities in this kind of system and in South America most of the studies are from black water systems located in the Amazonian region. These studies indicate the presence of an algal flora with a high percentage of desmids and diatoms, with low phytoplankton productivity and population densities. Other studies from humic freshwater coastal lagoons at the Southern and Southeastern regions show, in general, the same properties and an important contribution of small chlorococcal green algae and picoplanktonic cyanobacteria to total phytoplankton biomass ( Pålsson & Granéli 2004). However, little importance is given to the phytoflagellates.
On the global scale with huge geological formations, such as the bedrock shields in the Northern Hemisphere or the nutrient-poor regions in the tropics, the non-calcareous, HS rich freshwater type appears to predominate over the calcareous, HS-poor one. With up to 80%, humic substances (HS) comprise the majority of the organic carbon in any freshwater type, including all organisms. This figure even applies to non-eutrophicated freshwaters which do not have visible brownish colors (Jones 2005, Wetzel 2001). Yet, the knowledge of how HS control freshwater life is comparably scarce. Many HS-rich waters seem to have reduced biodiversity which applies to zooplankton, zoobenthos and fish. Many studies deal with the interaction of natural organic water constituents (dissolvedorganic carbon, HS, etc.) with xenobiotic chemicals and/or heavy metals and show a natural attenuation/quenching of the potentially adverse chemicals (2008a, b) in this series]. The quantitative aspect of these substances is well known: humic substances (HS) exceed the organic carbon in all living organisms by roughly one order of magnitude (Wetzel 2001); the concentrations lie between 0.1 and 8.5 mmol L–1. With >14 mmol L–1, extreme HS concentrations are found in one coastal lagoon in the Restinga de Jurubatiba National Park (Suhett et al. 2004). In obvious contrast to this quantitative significance of HS, the knowledge on the ecological function (qualitative significance) is still small. Only its function as an indirect external energy source has intensely been studied during the last two decades after the energy budget calculation of a humic lake.
Although the microbiological papers were the major opening of the ecological understanding of dead organic matter in freshwaters, this point of view remains still traditional, especially by disregarding HS as natural environmental chemicals. In freshwater systems, HS derive from peat and, the majority, from terrestrial plant debris, lignin building blocks, tannins and terpenoids being the main source material (Leenheer and Rostad 2004). The presence of functional groups such as carboxylic, phenolic, ketonic, aromatic, aliphatic etc. ones, enable HS to interact with both living and non-living matter.
Specific objectives:
- To isolate, characterized and identify the microorganisms in the water samples.
- To determinethe heavy metal content of the water.
- To assess the pollution status of the water as affecting human health.
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