Headwater Streams, Ecology, Fish, Macroinvertebrates


An in-depth ecological analysis of how and why the aquatic community changes over time was conducted for 6 streams on the Fort Polk military base in Louisiana using data collected from 2001 to 2019. Fort Polk is a unique location as nineteen first-order streams are located on the premises belonging to three separate drainages. The primary goal was to determine whether temporal or between-drainage variation has a larger effect on community structure. To accomplish this the effects of disturbance on fish and macroinvertebrate assemblages was determined temporally and between drainages. Several hypotheses were drawn from this: 1) temporally, assemblages exhibit fluctuations in diversity around disturbance events, but eventually recover to a base-state; 2) the 2012 drought caused a reduction in both fish and macroinvertebrate assemblage diversity and overall quantity in comparison to the other years; and 3) fish assemblages will vary between drainages more so than macroinvertebrate assemblages. A secondary goal was to determine the unique taxa of the drainages. It was found that 1) there was no recognizable pattern to assemblage diversity fluctuations and recovery; 2) the 2012 drought did not cause a significant reduction in fish or macroinvertebrate assemblages compared to subsequent years; and 3) fish assemblages differed by watershed more than macroinvertebrate assemblages, which often differed significantly by year. These ecological analyses present a more comprehensive picture of the ecosystems in the region.