Question

What other natural communities might be altered because of decreased stream flow?

Answer 1

Decreased stream flow alters aquatic ecosystems, affecting fish and amphibian populations, and impacts riparian areas which support diverse wildlife. Changes can also affect downstream ecosystems like estuaries and coral reefs through altered sediment transport.

Step-by-step explanation:

Decreased stream flow can lead to alterations in various natural communities. A notable impact is on aquatic ecosystems, where reduced water levels can directly affect fish populations, especially rare species or those with limited distributions. These species often depend on certain flow regimes and may face declines due to habitat loss. Moreover, amphibian populations also suffer since they require both aquatic and terrestrial habitats to complete their life cycles, and changes in stream flow can disrupt their access to these critical habitats. Beyond aquatic life, decreased stream flow can negatively influence riparian ecosystems, which are areas adjacent to rivers and streams that are rich in biodiversity. The change in water availability affects the plant life within these areas, subsequently impacting the insects, birds, and mammals that depend on them. Additionally, modified stream flows can influence sediment transport, which can affect downstream ecosystems such as estuaries and coral reefs that are sensitive to siltation. Ultimately, alterations in stream flow due to human actions like damming and water removal can have cascading effects on the ecology both within and outside the immediate riverine environment.

Answer 2

This question is incomplete. But I can at least list the biological communities that depend on particular stream flow regimes. Aquatic organisms are adapted to particular flow regimes. These regimes tend to be very seasonal in arid and semi-arid regions. So many aquatic organisms have aligned their life stages to co-inside with flow events. Determining flow regimes to sustain aquatic ecosystems is an entire branch of science called environmental flow determination. This science is particularly mature in semi-arid countries such as Australia. This science has evolved because people have built dams on rivers, which has drastically altered downstream flows. Environmental flows can guide how much water should be released downstream of dams to sustain aquatic ecosystems. Various insect species spend their nymph stages in water, such as mayflies and dragonflies for example. So they need to have some flow in a river to survive. Various species of fish also require particular flow thresholds to survive.