Question

2. Match the following descriptions with the intertidal zone that exhibits the characteristic: A, B, or C: Highest risk of desiccation, highest species diversity, and shallowest area where red, green and brown algae grow.

A) lower intertidal zone B) middle intertidal zone C) upper intertidal zone

3. Which of the following does not determine an estuary's mixing pattern: A) depth of the river upstream B) water density C) nearshore currents

Answer 1

Higher intertidal organisms are at higher desiccation risk, because they encounter high hours of sun. The organisms face extreme dryness.

Lower intertidal zone has the greatest species diversity because there are less fluctuations in salinity, temperature, and water coverage.

Algae found in the middle intertidal zone are mostly brown algae. There are also some red and green algae present there.

3. Depth of the river upstream do not determine the estuary's mixing pattern. Estuaries generally receive large volumes of fresh-water input and the net flow is out of the estuary at all depths.

Density and tidal current determine the mixing pattern because -

Density increases with increasing salinity and decreasing temperature. In an estuary, the lighter fresh water mixes with the heavier salt water from coastal waters and creates a gradient in water density in the estuary. The fresh water gains salt and becomes heavier. The heavy water sinks and fresh water goes up creating a gravitational circulation, and is caused by density and elevation differences between the fresh-water and saltier coastal waters.

Circulation patterns in estuaries are largely determined by the strength of tidal currents relative to the configuration of the river basin.