7 public questions tagged with this topic.
Cyanobacterial colonies are generally surrounded by a gelatinous sheath and often form blooms in polluted water bodies. Cyanobacteria may be unicellular, colonial or filamentous.
Ref: NCERT Class 11 Biology Chapter 2: Biological Classification Bacteria - Structure and Economic Importance
Eutrophication is enrichment of water with nutrients, especially phosphorus in many fresh waters and nitrogen in many coastal systems. The added nutrients remove a growth limitation on phytoplankton or cyanobacteria, allowing rapid population increase that appears as an algal bloom. Dense blooms reduce water clarity and shade submerged vegetation. When algal cells die, bacteria decompose the organic matter and consume dissolved oxygen; stratified bottom waters may then become hypoxic or anoxic. Fish kills, loss of oxygen-sensitive species, toxin-producing cyanobacteria, unpleasant odours, and
Ref: Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 2-3
Synthetic estrogens such as 17alpha-ethinylestradiol can feminise fish by binding estrogen receptors and altering gene expression during gonadal development and adult reproduction. Effects include male vitellogenin production, intersex tissue, reduced sperm production, female-biased phenotypes, and population decline. Testosterone is androgenic rather than estrogenic, while mercury and PCBs have important toxic effects but are not the clearest specific answer. Trophic transfer can occur when predators consume contaminated prey, although evidence for consistent biomagnification of particle numb
Ref: Campbell Biology, Urry et al., 12th Ed., Unit 8 Ecology
Many pharmaceuticals are consumed, incompletely metabolised, and excreted in urine or faeces. Sewer systems carry the parent compounds and active metabolites to treatment plants, where conventional processes may not remove them completely; treated effluent or untreated sewage then reaches rivers and lakes. Improper disposal can add to this route. Aerosols, fertilisers, and forest runoff are not the dominant general pathway. Because conventional polymers persist, fragmentation redistributes plastic into smaller pieces rather than removing its mass from the ecosystem. Trophic transfer can occur
Ref: Campbell Biology, Urry et al., 12th Ed., Unit 8 Ecology
Excess nitrogen and phosphorus stimulate eutrophication by removing nutrient limitation on algae and cyanobacteria. Dense blooms reduce light penetration, and their eventual decomposition raises microbial oxygen demand, producing hypoxia or anoxia that can kill fish and benthic animals. Some cyanobacteria also release toxins. Mercury, lead, and cadmium are hazardous metals, but they do not drive the nutrient-enrichment process that defines eutrophication. Aquatic effects depend on chemical form, persistence, solubility, dose, and the capacity of organisms to metabolise or excrete the substance
Ref: Campbell Biology, Urry et al., 12th Ed., Unit 8 Ecology
Fertiliser runoff is a non-point source because nutrients leave many dispersed fields through rainfall, overland flow, erosion, and subsurface drainage rather than through one readily identified discharge pipe. Its loading varies with land use, weather, soil, and farm management. A sewage outlet or industrial effluent pipe is a point source whose location can be mapped and monitored directly. Community-level consequences can emerge when physiological injury changes survival, reproduction, species interactions, or the flow of energy through food webs. Aquatic effects depend on chemical form, pe
Ref: Campbell Biology, Urry et al., 12th Ed., Unit 8 Ecology
High nitrate in drinking water can cause infant methaemoglobinaemia, commonly called blue baby syndrome. Gut microbes reduce nitrate to nitrite, which oxidises haemoglobin iron from the ferrous to ferric state, producing methaemoglobin that cannot bind oxygen effectively. Infants are particularly susceptible because of gastrointestinal and enzymatic features. Minamata and Itai-itai diseases involve mercury and cadmium, respectively, while cholera is an infection. Sensitive developmental stages may respond at concentrations that cause little immediate adult mortality, making reproduction and re
Ref: Campbell Biology, Urry et al., 12th Ed., Unit 8 Ecology
