Answer:
A. They recycle nutrients, purify water, attenuate floods, recharge ground water, and provide habitats for wildlife.
B. Freshwater ecosystem provides water for home and farm use and for power generation.
C. Tourism and recreation activities can have both direct and indirect effects on aquatic ecosystems. While recreational activities that take place in lakes, streams, wetlands and their riparian areas are most likely to negatively impact the aquatic environment, land-based activities can also impact the environment.
D. In a healthy, balanced freshwater ecosystem, photosynthesizing aquatic plants absorb nutrients and carbon dioxide from the water column in the presence of sunlight, transforming them into carbon and releasing oxygen in the process.
E. The availability of nutrients in aquatic systems is also an important aspect of energy or photosynthesis. Many organisms sink to the bottom of the ocean when they die in the open water; when this occurs, the energy found in that living organism is sequestered for some time unless ocean upwelling occurs.
