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Using a space‐for‐time substitution approach to predict the effects of climate change on nutrient cycling in tropical island stream ecosystems
Author(s) -
Frauendorf Therese C.,
MacKenzie Richard A.,
Tingley Ralph W.,
Infante Dana M.,
ElSabaawi Rana W.
Publication year - 2020
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.1002/lno.11577
Subject(s) - ecosystem , streamflow , environmental science , climate change , ecology , population , nutrient cycle , nutrient , biology , geography , drainage basin , demography , cartography , sociology
Climate change is expected to alter precipitation patterns worldwide, which can have direct effects on streamflow dynamics. In many tropical regions, climate‐driven changes in rainfall are predicted to decrease streamflow and increase flash flooding, but the implications of these changes for stream ecosystem function are poorly understood. We used a rainfall gradient on Hawaii Island that mimics projected changes in rainfall and streamflow in order to estimate how climate change affects nutrient recycling. We measured per‐capita excretion (nitrogen, phosphorus) and egestion rates of three dominant taxa (shrimp, caddisfly, midge) in eight streams along the gradient for 3 years. We scaled these rates to the population and community levels and measured nitrogen and phosphorus demand of the ecosystem to estimate if the relative contribution of nutrients supplied by invertebrates changes along the gradient. Across all three taxa, population egestion and excretion rates declined by 10‐fold in drier streams. These declines were driven by lower population density, rather than differences in per‐capita rates. Under the current climate scenario, community excretion supplied up to 70% of the nitrogen demand, which was 10‐fold lower with projected changes in rainfall. Conversely, community excretion supplied up to 5% of the phosphorus demand, which did not vary across the rainfall gradient. This difference indicates that climate change may exacerbate nitrogen limitations in tropical island streams, and change the balance of nitrogen and phosphorus dynamics. Our study also demonstrates that space‐for‐time substitutions are a valuable tool to examine implications of climate change on ecosystem function in freshwater systems.