What are some of the abiotic factors that scientists monitor when dealing with stream ecosystems? what are some of the biotic factors that scientists monitor when dealing with stream ecosystems? what is a "benchmark" in ecology? why are they essential? how does water pollution seem to be affecting diversity in some streams?

The abiotic factors of a stream ecosystem involves salt, water, rocks, sediments and trash. This includes the temperature of the water, how much oxygen it contains, how acidic or basic it is, how fast or slowly, and how much sunlight penetrates the surface. A stream ecosystem is the ecosystem of a river viewed as a system operating in its natural environment, including biotic factors and abiotic factors. 

Where are they though?

Leaves specifically the gas exchange between plants and the environment. while plants undergo photosynthesis, they also partake in cellular respiration. respiration is the process that happens in the leaves of plants.