|dc.description.abstract||Leaf litter decomposition is a fundamental part of the carbon cycle and helps
support aquatic food webs along with being an important assessment of the health of
rivers and streams. Disruptions in this organic matter breakdown can signal problems
in other parts of ecosystems. One disruption is rising chloride concentrations.
Chloride concentrations are increasing in many rivers worldwide due to
anthropogenic sources that can harm biota and affect ecosystem processes. Elevated
chloride concentrations can lead to lethal or sublethal impacts. While many studies
have shown that excessive chloride uptake impacts health (e.g. lowered respiration
and growth rates) in a wide variety of aquatic organisms including microbes and
benthic invertebrates). The impacts of high chloride concentrations on decomposers
are less well understood.
My research objective was to assess how increasing chloride concentrations affect
the performance and diversity of decomposer organisms in freshwater systems. I
experimentally manipulated chloride concentrations in microcosms containing leaves
colonized by microbes or containing leaves, microbes and amphipods. Respiration
rate, decomposition, and community composition of the microbes were measured
along with the amphipod growth rate, egestion rate, and mortality.
Elevated chloride concentration did not impact microbial respiration rates or leaf
decomposition, but had large impacts on bacteria community composition. It did
cause a decrease in instantaneous growth rate, and 100% mortality in the highest
amphipod chloride treatment, but amphipod egestion rate was not significantly
affected. The results of my research suggest that the widespread increases in chloride
concentrations in rivers will have an impact on decomposer communities in these