Fareed A. Khan

Eutrophication: An Ecological Vision

The present review deals with the studies conducted on the impact of phosphorus on growth of aquatic plants causing eutrophication in well-known water bodies the world over. The review covers the definition and concept of eutrophication and the adverse effects on quality and ecosystem functioning. The eutrophication of several water bodies leads to significant changes in the structure and function of the aquatic ecosystem. Several activities of human interest, including navigation and power generation, are hampered. A large number of lakes in the United States, Europe, and Asia have recently been found to be highly eutrophic. Water, the precious fluid, is not uniformly distributed throughout the surface of the earth. Most of the water bodies world over are surrounded with densely populated human settlement areas and agricultural fields. The size of smaller water bodies in human settlement areas is on the decrease with rise in population. After treatment, a large quantity of sewage from the households is regularly discharged into the water bodies. The runoff brings down fertilizers and other chemicals from agricultural fields. The phosphorus contained in these effluents is known to promote excessive growth of plants. This review is an account of the role, sources, and monitoring of phosphorus, as well as its cycle. The natural phosphorus cycle originating from the weathering of phosphate rock is now a two-way operation, due to significant addition of phosphorus from anthropogenic sources.The detergents that are the major source of phosphorus inputs into water bodies (through sewage and drainage systems) have been thoroughly discussed. The major part of detergents comprises builders containing polyphosphate salts. An environment-friendly and effective synthetic builder is yet to be developed to replace existing phosphorus containing builders of detergents. The utility of the alternative builders available has been reviewed. Nitrogen has also been reported to affect the phytoplankton production in eutrophic waters in temperate regions. Several environmental factors have also been found to add to the problem of eutrophication in addition to nutrients. Several limiting factors—namely, CO2 level, temperature, pH, light, and dissolved oxygen—are known to affect eutrophic water bodies. Eutrophication not only results in algal bloom but also affects wetland plants and activates early onset of natural succession at a relatively faster rate. Some of the plant species reported and studied world over are the best indicators of the level of eutrophication. The studies on the change in structure, function, and diversity of the ecosystem have been used as parameters to assess the level of eutrophication. In several countries adequate control measures have been adopted in to control eutrophication. But these measures were found to be only partially effective in controlling the phosphorus unloading in water bodies. In this review some control measures are suggested, with emphasis on biological control. The review concludes by taking into account the ecological prospective of the water—the precious fluid and a basis of life on the earth.

Eutrophication: Threat to Aquatic Ecosystems

Eutrophication was recognized as a pollution problem in European and North American lakes and reservoirs in the mid-twentieth century. Since then, it has become more widespread. Surveys showed that most of the lakes in Asia, Europe, North America, South America, and Africa are found in eutrophic state. Eutrophication leads to significant changes in water quality. It lowers the value of surface waters for the industrial and recreational uses. The overpopulation of algae makes water unfit for swimming. The algae growing in long strands often twine around boat propellers and make boating difficult. Eutrophic waters tend to be scummy, cloudy, or even soupy green. The rapidly growing aquatic plants may wash onto the shores in storms or high winds, where these plants die, decay, and produce a bad smell all around such water bodies. The eutrophication in an aquatic ecosystem also causes significant changes in biodiversity. The eutrophication causes an increase in plant and animal biomass, frequency of algal blooms, growth of rooted plants, and decreases the species diversity. Due to eutrophication, an increase in turbidity and anoxic conditions occurs. Because of the high density of aquatic organisms in a eutrophic system, there is often a lot of competition for resources. This high degree of competition and high chemical or physical stress make the struggle for the survival in eutrophic systems higher. As a result the diversity of organisms is lower in eutrophic than in oligotrophic systems.

Aquatic Plant Diversity in Eutrophic Ecosystems

The chapter contains studies conducted on the impact of eutrophication on aquatic plant diversity. It covers the concept of eutrophication, its causes and effects on plant diversity within an aquatic ecosystem. A decrease in species diversity and disappearance of aquatic plants were noted in most of the water bodies of the world as a result of eutrophication. The plant diversity in eutrophic ecosystems was studied with special reference to phytoplankton and aquatic macrophytes. Studies on wetlands in western Europe showed that the nutrient enrichment or eutrophication leads to changes in species composition, declines in overall plant species diversity, and loss of rare and uncommon species. The nutrients are the major limiting factors for the aquatic plant diversity. Various environmental factors play a significant role in determining the aquatic plant diversity in a eutrophic ecosystem. In Europe about 17 lakes underwent eutrophication and have lost all or most of their submerged species and favoured the fast growing species capable of regrowth after weeding. The eutrophication process causes succession of macrophytes with complete loss of submerged vegetation and dominance of phytoplanktons. A direct relation was found between the succession of algae and trophic level of the water body. Few studies on measurements of plant diversity such as density, frequency, abundance, and diversity indices are included in this chapter.

Proline Accumulation in Plants: Roles in Stress Tolerance and Plant Development

Proline accumulation occurs in a wide range of plant species in response to various kinds of environmental stresses. A large body of evidence suggests that a positive correlation occurs between proline accumulation and plant stress tolerance. In this chapter, we will discuss the metabolism of proline accumulation and its role in stress tolerance in plants. Existing literature indicates that despite acting as an osmolyte, proline also plays important roles during stress as a metal chelator and an antioxidative defence molecule. Moreover, when applied exogenously at low concentrations, proline enhanced stress tolerance in plants. However, some reports point out adverse effects of proline when applied at higher doses. Role of proline in seed germination, flowering and other developmental programmes is also presented in this chapter.

Assessment of biotransfer and bioaccumulation of cadmium, lead and zinc from fly ash amended soil in mustard–aphid–beetle food chain

The present study investigates the extent of biotransfer and bioaccumulation of cadmium (Cd), lead (Pb) and zinc (Zn) from fly ash amended soil in mustard (Brassica juncea)-aphid (Lipaphis erysimi)-beetle (Coccinella septempunctata) food chain and its subsequent implications for the beetle. The soil was amended with fly ash at the rates of 0, 5, 10, 20 and 40% (w/w). Our results showed that the uptake of Cd, Pb and Zn from soil to mustard root increased with the increase in fly ash application rates, but their root to shoot translocation was relatively restricted. Increase in chlorophyll content and dry mass of mustard plant on treatments ≥20% even at elevated accumulation of Cd (1.67mgkg-1), Pb (18.25mgkg-1) and Zn (74.45mgkg-1 dry weight) in its shoot showed relatively higher tolerance of selected mustard cultivar to heavy metal stress. The transfer coefficient (TC1) of Cd from mustard shoot to aphid was always >1, indicating that Cd biomagnified in aphids at second trophic level. But, there was no biomagnification of Cd in adult beetles at third trophic level. Zinc accumulation was 2.06 to 2.40 times more in aphids than their corresponding host shoots and 1.26-1.35 times more in adult beetles than their prey (aphids) on which they fed. Lead was only metal whose TC was <1 at both second and third trophic levels. The elimination of Cd via honeydew of aphids was most efficient as the ratio of metal in honeydew to aphid (ranging from 0.21 to 0.26) was higher than the Pb (0.16 to 0.20) and Zn (0.07 to 0.09). The statistically consistent (p>0.05) biomass and predation rate of predatory beetles indicated that all levels of soil amendments with fly ash did not have any lethal or sub-lethal effects on beetles.

Major and trace element geochemistry of lake sediments, India: implications for weathering and climate control

Climate plays an essential role in weathering of rocks, and a rich record of climatic change is preserved in rocks and sediments. The physical and chemical weathering also largely depend on climate prevailing in the area, apart from other factors. In an attempt to understand the dominance of physical over chemical weathering processes, the textural and geochemical studies of Wular Lake sediments from Jammu and Kashmir, northern India, have been taken up in the present study. These sediments documented several attention-grabbing processes that operated during weathering, transportation, and deposition. Investigations have revealed that physical weathering dominated over chemical weathering, resulting in enhanced rates of erosion and consequent deposition of large detritus into the lake. Lake sediments and source rock chemistry are comparable, indicating low to moderate chemical weathering history of the source region which is consistent with cold regions and steep slope areas. Unusual enrichment of Cr values in sediments compared with source rocks signify a process of sediment–water interaction where Cr is removed from water and preferentially adsorbed onto clay fraction of sediments.

Household Detergents Causing Eutrophication in Freshwater Ecosystems

In the present study, the impact of some selected household detergents has been studied on the growth behavior and development of two freshwater duckweeds, namely Lemna minor and Spirodela polyrrhiza. The growth responses of these selected free-floating duckweeds to varying concentrations of “Surf Excel” (the most commonly used detergent) have been studied with special reference to varying temperature and pH. There were three predominant types of growth pattern of both the selected duckweeds treated with 36 selected detergents. Some of the detergents increased the growth of the two duckweeds in almost logarithmic progression showing increase in growth with increasing concentration (10–50 ppm). A few detergents increased growth of both the selected duckweeds to a certain level of detergent concentration and then the growth became stationary with further increase in detergent concentration. In the third type of response, the duckweed growth initially increased in response to a certain level of detergent concentration and declined at higher detergent concentration. It was inferred from the observations that detergents play important role in promoting the growth of duckweeds. Out of 36 detergents studied, certain detergents effectively promoted the growth of duckweeds even in low concentration. Certain brands of detergents resulted in consistent increase in the growth with increasing concentration. The temperature effectively modified the duckweed response to the detergent. The cooler water medium had lesser degree of eutrophication than the moderately warm water medium. Not the phosphorus content alone, but the water quality (turbidity, pH, nutrient concentration, and dissolved oxygen) modified by the detergent aggravated the problem of eutrophication. Therefore, the water bodies receiving acids from any source in addition to detergent are more likely to show a greater degree of eutrophication than a body receiving detergent without acids.

Assessment of aphid infestation levels in some cultivars of mustard with varying defensive traits

Phloem-sucking mustard aphid (Lipaphis erysimi) is a major pest of mustard (Brassica juncea). Pot experiment with randomised block design was conducted with five replicates of each of five cultivars (Alankar, Pusa Jai Kisan, Rohini, Sakha and Varuna) of the mustard for their degree of inherited resistance and/or susceptibility to the mustard aphid infestation. Forty-five days old (from date of sowing) pot-grown plants of all selected cultivars of mustard were exposed to 40 adult mustard aphids. The aphid-infested plants were kept in specially designed net houses of fine mesh to protect from predators and/or migration of aphids from one to other host. The aphid population and some growth attributes of the selected cultivars of mustard were recorded 15 and 30 days later (i.e. at 60 and 75 days after sowing). The aphid population multiplied more rapidly on Rohini than other four cultivars. Cultivar Alankar resisted most and supported to least number of aphid’s off-springs. Statistically analysed growth attributes (fresh plant mass, dry plant mass, protein, chlorophyll and carotenoid contents), resistance attribute (proline) and population demography of aphids revealed that some inherited characteristics of avoidance, antibiosis and repellence to herbivores helped cultivar Alankar to excel despite equal degree of aphid attacks as on other cultivars. Cultivar Rohini for the want of such resisting factors remained vulnerable to aphid herbivory. These two cultivars (Alankar and Rohini) form good research material for comparative studies on plant defences to herbivory and a tri- trophic resistance through volatile chemical signalling.

Roles of Brassicaceae in Phytoremediation of Metals and Metalloids

Heavy metals and metalloids in trace amounts are natural components of environment. Their excessive addition by anthropogenic means posed a serious threat to the stability of ecosystem. Recent concerns of environmental contamination have initiated the development of appropriate technologies for removing or reducing such toxicants from different components of environment. Plants that accumulate greater than 0.1 % metals in leaves or other tissues without showing any visible toxicity symptoms are categorised as hyperaccumulators. These plants may be used as cost-effective and eco-friendly remediators at contaminated sites. In the present review, the key roles of several species of family Brassicaceae have been highlighted with species-level mechanism of phytoremediation. About (25 %) members of the Brassicaceae comprising of about 90 species are metal hyperaccumulators discovered worldwide to date. These Brassicaceae members are potential candidates for phytoremediation technologies. Of these 90 metal hyperaccumulators, species of the genera such as Alyssum, Arabidopsis, Noccaea and Brassica have been studied extensively for their ability to hyperaccumulate, remove, destroy, degrade, sequester, transform, assimilate, metabolise or detoxify majority of trace metals and appear to be model phytoremediators. These species are also attractive candidates for developing transgenics by introducing relevant genes to improve their applicability for phytoremediation. In this review, we elucidate the diversity and role of some of the Brassicaceae members in remediating contaminated sites worldwide and also highlighted the physiological mechanisms of uptake and tolerance, the genetic basis for the metal tolerance mechanisms.

Phytoremediation Systems for the Recovery of Nutrients from Eutrophic Waters

Eutrophication and availability of freshwater for human consumption is one of the main issues in front of the environmentalists. Eutrophication, acidification, and contamination by toxic substances are posing a threat to the freshwater resources and ecosystems. The consequence of anthropogenic-induced eutrophication of freshwater has resulted in severe deterioration of surface water. Effective control measures need to be taken in order to control eutrophication and restore eutrophic water bodies. In this row, phytoremediation is emerging as a simple low-cost clean up technology for wastewater. Phytoremediation is defined as the engineered use of green plants to remove, or render harmless, various environmental contaminates such as inorganic and organic compounds. Development of aquatic plant systems for nutrient recovery from eutrophic water is essentially required to control eutrophication. The performance of phytoremediation system depends upon many factors such as growth performances of the plants selected for phytoremediation, their nutrients removal potential, efficiency to grow in experimental environment. In order to develop high-efficient nutrients phytoremediation systems aquatic plant species in combinations (mono, bi, tri species culture) can be used. Sufficient work has been done and huge amount of capital is invested so far for the restoration of some major water bodies that are falling under direct threat of eutrophication but the results are unsatisfactorily.