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Accueil du site → Doctorat → États-Unis → 2010 → Effects of the exotic invader, Tamarix spp., on aspects of the aquatic ecosystem at McComb Creek, Presidio County, Texas

UNIVERSITY OF TEXAS AT ARLINGTON (2010)

Effects of the exotic invader, Tamarix spp., on aspects of the aquatic ecosystem at McComb Creek, Presidio County, Texas

Moore, Jane Blaisdell Nelan

Titre : Effects of the exotic invader, Tamarix spp., on aspects of the aquatic ecosystem at McComb Creek, Presidio County, Texas

Auteur : Moore, Jane Blaisdell Nelan

Université de soutenance : THE UNIVERSITY OF TEXAS AT ARLINGTON,

Grade : Doctor of Philosophy (PhD) 2010

Résumé partiel
The effects of saltcedar, Tamarix spp., invasion in riparian zones of the western United States have been well documented. These include, but are not limited to soil salinization, and shifts in hydrology and water use. Comparatively unknown are the effects on the associated aquatic systems and if a significant increase in water salinity accompanies these invasions. Shifts in stream metabolism have been reported, but the impacts of saltcedar invasion on the algal species, which are the dominant primary producers in desert aquatic ecosystems, are unknown. A two year study was conducted in an oligotrophic desert stream, currently experiencing an invasion, to determine the influence of saltcedar on specific environmental factors and their effect on benthic algal assemblages and stream metabolism. Saltcedar presence in this system was expected to increase salinity. A potential increase in phosphorus availability, resulting from this salinity increase, may cause a shift from species-poor communities of oligotrophic and halosensitive algae to species-rich communities of eutrophic and halotolerant species. The invasion may also influence other aquatic environmental parameters that are fundamental determinants of algal community composition, such as temperature, pH, conductivity and nitrogen. Canopy cover of the stream would also be increased, thereby lowering daily photosynthetically active radiation (PAR) and increasing allochthonous input into the stream in the form of leaf litter. A greater allochthonous input is expected to drive an increase in respiration, effectively counteracting any increase in photosynthesis that may result from increased nutrients in the saltcedar invaded reach. Therefore, no significant difference in stream metabolism between the upstream native and downstream saltcedar reaches was anticipated. Species composition and diversity were assessed across reaches by deploying artificial substrates and performing a series of experiments utilizing nutrient-diffusing substrates (NDS) and transplantation of artificial substrates. Environmental measurements of temperature, pH, conductivity, daily PAR, dissolved oxygen, soluble reactive phosphorus (SRP), nitrate-nitrogen and ammonium-nitrogen were measured to determine if saltcedar presence exerted any effects on these parameters.

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