The effects of climate change and introduced species on tropical island streams

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dc.contributor.author Frauendorf, Therese
dc.date.accessioned 2019-08-09T17:22:57Z
dc.date.available 2019-08-09T17:22:57Z
dc.date.copyright 2019 en_US
dc.date.issued 2020-08-01
dc.identifier.uri http://hdl.handle.net/1828/11028
dc.description.abstract Climate change and introduced species are among the top five threats to freshwater systems face. Tropical regions are considered to be especially sensitive to the effects of climate change, while island systems are more susceptible to species introductions. Climate-driven changes in rainfall are predicted to decrease streamflow and increase flash flooding in many tropical streams. In addition, guppies (Poecilia reticulata), an invasive fish, have been introduced to many tropical freshwater ecosystems, either intentionally for mosquito population control, or accidentally because of the aquarium trade. This dissertation examines the effects of climate-driven change in rainfall and introduced guppies on stream structure (resource and invertebrate biomass and composition) and function (nutrient recycling) in Trinidad and Hawaii. In the first data chapter we used a time series to examine how nutrient recycling of guppies changes in the first 6 years after introduction to a new habitat and to examine drivers of these changes. We found that when guppy populations establish in a new environment, they show considerable variation in nutrient recycling through time. This resulted from changes in guppy density in the first two years of introductions, and changes in individual excretion in subsequent stages. In the following chapter we utilized a rainfall gradient that mimics forecasted, climate-driven changes in precipitation and resulting changes in streamflow to examine the effects of climate change on stream food resources and macroinvertebrates. We found that the drying of streams across the gradient was associated with a decrease in resource quality and a 35-fold decline in macroinvertebrate biomass. Invertebrate composition also switched to taxa with faster turnover rates. In the third data chapter we used this same space-for-time substitution approach to determine if climate-driven changes in stream structure also affected stream function. We showed that population nutrient recycling rates declined at the drier end of our rainfall gradient as a result of drops in population densities. We also found that under the current climate scenario, community excretion supplied up to 70% of the nutrient demand, which was ten-fold lower with projected climate changes in streamflow. Lastly, since freshwater ecosystems often face multiple human impacts, including climate change and invasive species, we wanted to understand how climate-driven changes in flow might alter the impact of introduced guppies on stream ecosystems. We selected several streams with guppies and several without guppies along the Hawaii rainfall gradient to examine if the effect of guppies changed with differences in streamflow. We found that the two stressors had synergistic effects on macroinvertebrate biomass and nutrient recycling rates. We concluded that climate change appeared to enhance effects of guppies, through direct and indirect effects. Overall, this dissertation shows that both climate change and species invasion can affect stream ecosystems at multiple levels of organization. This dissertation demonstrates that the effects of anthropogenic stressors are not static through time, and emphasizes the need and utility of using several methodological approaches when measuring the temporal effects of stressors. We also underline the significance of assessing multiple stressor interactions, as more than one stressor often impacts ecosystems. en_US
dc.language English eng
dc.language.iso en en_US
dc.rights Available to the World Wide Web en_US
dc.subject Guppy en_US
dc.subject Nitrogen en_US
dc.subject Phosphorus en_US
dc.subject Size structure en_US
dc.subject Density en_US
dc.subject Trinidad en_US
dc.subject Hawaii en_US
dc.subject Invertebrates en_US
dc.subject Space-for-time substitution en_US
dc.subject Multiple Stressors en_US
dc.subject Streamflow en_US
dc.subject Precipitation gradient en_US
dc.subject Organic matter en_US
dc.subject Nutrient uptake en_US
dc.subject Egestion en_US
dc.subject Excretion en_US
dc.subject Climate change en_US
dc.subject Invasive species en_US
dc.title The effects of climate change and introduced species on tropical island streams en_US
dc.type Thesis en_US
dc.contributor.supervisor El-Sabaawi, Rana
dc.degree.department Department of Biology en_US
dc.degree.level Doctor of Philosophy Ph.D. en_US
dc.identifier.bibliographicCitation Frauendorf T.C., MacKenzie R.A., Tingley R.W., Frazier A.G., Riney M.H. & El‐ Sabaawi R.W. (2019). Evaluating ecosystem effects of climate change on tropical island streams using high spatial and temporal resolution sampling regimes. Global Change Biology 25, 1344–1357. https://doi.org/10.1111/gcb.14584 en_US
dc.description.scholarlevel Graduate en_US
dc.description.embargo 2019-09-01

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