Discuss the consequences of reduced surface water flow on aquatic ecosystems and biodiversity
Answer:-
Surface water flow—comprising rivers, streams, and wetlands—is vital for maintaining healthy aquatic ecosystems. A reduction in surface water flow, whether due to drought, damming, over-extraction, or climate change, has serious ecological consequences. It affects water quality, habitat availability, and the survival of aquatic organisms, ultimately reducing biodiversity.
1. Habitat Loss and Fragmentation:
- Lower flow levels shrink river channels, dry up wetlands, and disconnect aquatic habitats.
- Species that rely on specific flow conditions (e.g., breeding fish, amphibians) face loss of breeding grounds and shelter.
- Fragmented water bodies limit movement and migration of aquatic organisms, especially for species like eels or salmon.
2. Decline in Water Quality:
- Reduced flow leads to stagnation of water, increasing temperature and reducing dissolved oxygen (DO) levels.
- This promotes the growth of algae and harmful bacteria, which further deteriorates water quality.
- Poor water quality causes stress and mortality in sensitive species and favors invasive or tolerant organisms.
3. Alteration of Food Webs:
- Reduced flow changes the distribution and abundance of primary producers like algae and aquatic plants.
- This affects higher trophic levels such as zooplankton, insects, and fish that feed on them.
- Predators, both aquatic and terrestrial, are impacted due to a disruption in prey availability.
4. Increased Competition and Predation:
- As habitats shrink, organisms are forced into smaller areas, increasing interspecies competition for food and space.
- Predatory species may have higher success rates in shallow or slow-moving waters, increasing mortality of smaller organisms.
5. Loss of Biodiversity:
- Species that are highly adapted to specific flow regimes may face extinction.
- Endemic and freshwater-dependent species are especially vulnerable.
- The overall species richness and genetic diversity in aquatic ecosystems decline.
6. Disruption of Reproductive Cycles:
- Many aquatic organisms use seasonal flow changes as breeding cues.
- Reduced or unseasonal flows disturb spawning cycles, egg hatching, and larval development in fish and amphibians.
7. Impact on Riparian and Terrestrial Ecosystems:
- Aquatic ecosystems are linked to riparian vegetation, which depends on regular flooding and water tables.
- Reduced flow affects the entire riverine ecosystem, leading to loss of flora and fauna even outside the aquatic zone.