Ecosystems, the intricate webs of interactions between living organisms and their environments, play a foundational role in supporting life. Pollution disrupts these systems, challenging the survival of species and ecosystems alike. This section provides a deeper understanding of specific pollutants and their consequences.
Eutrophication
Eutrophication is an ecological process where water bodies experience heightened levels of nutrients, leading to a series of cascading events detrimental to aquatic health.
Causes of Eutrophication
- Agricultural Runoff: Intensive agricultural practices often involve the use of fertilisers. Rainwater can wash these nutrients into nearby water systems.
- Sewage Discharge: Improperly treated sewage can release high levels of nutrients into aquatic systems.
- Industrial Effluents: Certain industries, such as the phosphate industry, discharge waste containing phosphorus and nitrogen.
Consequences of Eutrophication
- Algal Blooms: When exposed to heightened nutrient levels, particularly nitrates and phosphates, algae proliferate. These blooms cloud the water and block sunlight.
- Oxygen Depletion: Once the algae exhaust the nutrients and begin to die, bacteria break them down. This decomposition process consumes vast amounts of oxygen, creating anoxic conditions.
- Biodiversity Loss: Fish and other aquatic organisms suffocate in the low oxygen conditions. Over time, species that cannot cope with these conditions perish or migrate, leading to reduced biodiversity.
Image courtesy of VectorMine
Biomagnification
Biomagnification is the process wherein toxins become increasingly concentrated in an organism as one ascends the food chain.
Example: DDT
- History: Introduced during the mid-20th century, DDT emerged as a potent weapon against pests, particularly mosquitoes.
- Environmental Persistence: DDT doesn't break down easily, persisting in the environment for long durations.
- Magnification Through the Food Chain: Small organisms like plankton absorb DDT. Small fish consume these plankton, and larger fish eat these smaller fish. With each trophic level, DDT concentration intensifies, reaching dangerous levels in apex predators.
Example: Mercury
- Origins: Industrial processes, waste incineration, and coal-fired power plants release mercury into the environment.
- Biomagnification Pathway: In water, bacteria transform mercury into methylmercury, a toxin. Small fish consume plankton that have absorbed this toxin. As with DDT, larger fish that eat these smaller fish accumulate even higher levels of mercury.
Biomagnification of toxins in a pond ecosystem.
Image courtesy of Estefaniajmz
Impact of Plastics on Marine Ecosystems
The proliferation of plastics, both micro and macro, in our oceans is an alarming concern.
Microplastics
- Origins: These minute particles either fragment from larger plastics or are manufactured as microbeads for products like exfoliating face washes.
- Ingestion by Marine Life: Many marine species, from tiny plankton to larger fish, mistake microplastics for food, leading to ingestion. This not only causes physical harm but also introduces the chemicals within plastics into the organism's system.
- Toxin Adherence: Microplastics can act as magnets for other toxins in the water, enhancing their deleterious effects when ingested.
Macroplastics
- Predominant Forms: These include everyday items like bags, straws, bottles, and discarded fishing gear.
- Physical Threat: Larger marine species, such as sea turtles, often mistake plastic bags for jellyfish, leading to ingestion. This can cause blockages, malnutrition, and even death.
- Habitat Alteration: The accumulation of plastics on the sea floor or in floating patches alters habitats, making them inhospitable or even deadly to native species.
Image courtesy of The Ocean Cleanup
Role of Scientific Communication
Effective communication of scientific findings is pivotal in shaping public opinion and guiding policy decisions.
Informing the Public
- Publication and Media: Scientific journals, documentaries, news stories, and even social media play roles in disseminating research findings.
- Education: Schools, universities, and community programmes can embed environmental science into their curricula, fostering informed future generations.
Influencing Policy
- Direct Consultation: Scientists often collaborate with policymakers to draft evidence-based legislation.
- Lobbying and Advocacy: Many scientific communities actively lobby for environment-friendly policies.
- International Collaboration: Many environmental challenges transcend borders. International conventions, informed by scientific research, aim to address these issues on a global scale.
FAQ
The general public plays a crucial role in curbing both eutrophication and plastic pollution. For eutrophication, individuals can limit the use of fertilisers in gardens and ensure that septic systems are well-maintained. Engaging in community clean-up efforts to prevent litter from reaching waterways can also help. Regarding plastic pollution, reducing plastic consumption by opting for reusable alternatives, supporting bans on microbeads and single-use plastics, and recycling properly are effective measures. Additionally, raising awareness, supporting environmental policies, and advocating for research and initiatives targeting these issues can drive broader societal changes.
Beyond obstructing sunlight, algal blooms can produce harmful toxins known as cyanotoxins. When consumed by aquatic organisms or even humans, these toxins can have harmful or even lethal effects. They can cause various illnesses, from skin rashes and stomach ailments to severe neurological disorders. Additionally, the rapid proliferation and subsequent death of algae can lead to drastic fluctuations in oxygen levels. As these algae die and decompose, the process consumes significant oxygen, leading to hypoxic conditions. Such low-oxygen environments can cause large fish kills and disrupt the ecological balance of the affected water body.
Climate change intensifies eutrophication in various ways. Rising temperatures can promote faster growth of algae and cyanobacteria, leading to more frequent and intense algal blooms. Additionally, increased rainfall and storm events, predicted under many climate change models, can lead to more runoff from land, carrying higher loads of nutrients (from fertilisers or sewage) into water bodies. Warmer water temperatures also reduce the solubility of oxygen, exacerbating hypoxic conditions brought about by algal decomposition. Lastly, altered circulation patterns in water bodies due to temperature stratification can trap nutrients in surface waters, further promoting algal growth.
Heavy metals, such as mercury, primarily enter aquatic systems through human activities. Industrial processes, like coal combustion, mining, and waste incineration, release significant quantities of mercury into the atmosphere. This atmospheric mercury eventually deposits onto land or directly into water bodies through rainfall or dry deposition. Natural processes, like volcanic eruptions and weathering of rocks, can also contribute, albeit to a lesser extent. Once in the water, mercury undergoes a transformation into its more toxic form, methylmercury, through microbial action. This bioavailable form of mercury becomes a major concern for biomagnification in aquatic food chains.
Plastics contain a range of chemicals added during manufacturing to impart specific properties. Some of these chemicals include phthalates, bisphenol A (BPA), and polybrominated diphenyl ethers (PBDEs). Phthalates are plasticisers that increase flexibility, but they can disrupt the endocrine system of marine organisms. BPA, used in producing polycarbonate plastics, has garnered attention for its estrogen-mimicking properties, which can interfere with reproductive systems. PBDEs, which act as flame retardants, can affect the nervous system. When marine organisms ingest plastics, these chemicals can leach out, introducing them to the organism's system and potentially leading to various health issues.
Practice Questions
Eutrophication is an ecological phenomenon wherein an aquatic ecosystem experiences an excessive influx of nutrients, predominantly nitrates and phosphates. Primary causes include agricultural runoff, which carries fertilisers, untreated sewage discharge, and industrial effluents rich in nutrients. As a result of this nutrient surplus, algae proliferate rapidly, leading to algal blooms. These blooms cloud the water, reducing sunlight penetration and, subsequently, photosynthesis of submerged plants. When these algae die, their decomposition by bacteria consumes vast amounts of oxygen, creating hypoxic or anoxic conditions. This oxygen depletion adversely affects aquatic life, leading to fish kills and a significant reduction in biodiversity.
Microplastics, being tiny fragments of plastic less than 5mm, and macroplastics, larger everyday items like bags and bottles, both pose severe threats to marine ecosystems. Marine organisms often ingest microplastics, mistaking them for food. This ingestion can lead to physical harm, chemical contamination, and even toxin adherence from the surrounding waters. Macroplastics, on the other hand, pose entanglement risks and can be ingested by larger marine species, leading to blockages and malnutrition. Scientific communication plays a pivotal role in addressing these challenges. By disseminating research findings through publications, media, and education, the public becomes informed, leading to behavioural changes. Furthermore, evidence-based policymaking, influenced by scientific findings, can implement regulations to reduce plastic pollution.
