Watersheds may be contaminated by fertilizers and other pollutants. when these substances enter a waterway, they can cause algal blooms, which are rapid overgrowths of algae. when the algae die, the decay uses up a large portion of dissolved oxygen. declining oxygen levels can then cause large die-offs of animals in the waterway. what will an algal bloom in a watershed most likely cause?

Eutrophication

Watershed is a wetland, that forms when water from a particular source like river, lakes, ponds or ocean gets accumulated through surface runoff into a large depression in land. An estuary, pond and lakes are types of watershed. The fertilizers and other pollutants gets swiped from the surface of agricultural land or from other source and enters into the watershed, contaminates the water. The minerals present in the fertilizers actually useful for growth of aquatic plants like algae present in the watershed. This results in the increase in abundance of the algae typically growing on the surface of water. This causes depletion of atmospheric oxygen in the water, which further results in the death of the aquatic animals residing in the watershed. This effect of growth and abundance of algae on the surface of watershed is called as eutrophication.

answer: decrease

a limiting factor is the one which decrease the abundance, distribution and causes extinction of the population of species in a ecosystem. here, predators including hawks, owls and snakes are the limiting factor for the population of mexican free tailed bat.   although bats are nocturnal animals as they forge for food at night these predators also may remain active during night which can decrease the population of the mexican free-tailed bats. also, these bats eat only one type of insects that are moths. the food can also be a limiting factor as all 400 members are dependent upon same type of food needs that are moths. the decrease in the moth population can cause decrease in population size of the mexican free-tailed bats.

therefore, the scenarios will most likely to decrease the population size of the mexican free-tailed bats.