Coral Uptake of Inorganic Phosphorus and Nitrogen Negatively Affected by Simultaneous Changes in Temperature and pH

The effects of ocean acidification and elevated seawater temperature on coral calcification and photosynthesis have been extensively investigated over the last two decades, whereas they are still unknown on nutrient uptake, despite their importance for coral energetics. We therefore studied the separate and combined impacts of increases in temperature and pCO2 on phosphate, ammonium, and nitrate uptake rates by the scleractinian coral S. pistillata. Three experiments were performed, during 10 days i) at three pHT conditions (8.1, 7.8, and 7.5) and normal temperature (26°C), ii) at three temperature conditions (26°, 29°C, and 33°C) and normal pHT (8.1), and iii) at three pHT conditions (8.1, 7.8, and 7.5) and elevated temperature (33°C). After 10 days of incubation, corals had not bleached, as protein, chlorophyll, and zooxanthellae contents were the same in all treatments. However, photosynthetic rates significantly decreased at 33°C, and were further reduced for the pHT 7.5. The photosynthetic efficiency of PSII was only decreased by elevated temperature. Nutrient uptake rates were not affected by a change in pH alone. Conversely, elevated temperature (33°C) alone induced an increase in phosphate uptake but a severe decrease in nitrate and ammonium uptake rates, even leading to a release of nitrogen into seawater. Combination of high temperature (33°C) and low pHT (7.5) resulted in a significant decrease in phosphate and nitrate uptake rates compared to control corals (26°C, pHT = 8.1). These results indicate that both inorganic nitrogen and phosphorus metabolism may be negatively affected by the cumulative effects of ocean warming and acidification

Physicochemical and Biological Conditions in Two Oklamhoma Reservoirs Undergoing Artificial Destratification

Prepared for the Bureau of Reclamation's Reaeration Research Program by the Oklahoma Water Resources Research InstituteThe purpose of this study was to develop more efficient methods of reservoir reaeration and to determine the environmental effects of reservoir destratification. The Garton pump, a low energy, axial flow device, is designed to pump water from the surface downward to destratify and reaerate lakes and reservoirs. A 1.07-m-diameter version of the device was tested in Ham's Lake (40 ha surface area, 10 m maximum depth) near Stillwater, Okla., in 1973 and 1974, and a 1.83-m-diameter version was operated in 1975. Complete thermal destratification was obtained. A 5-m-diameter version of the Garton Pump was operated in Lake of the Arbuckles (951 ha surface area, 27 m maximum depth) near Sulphur, Okla., in 1974 and 1975. Improvements in the design resulted in substantial perturbation of the physicochemical conditions of Lake of the Arbuckles in 1975. This report describes vertical variations in the two reservoirs of: (1) temperature, dissolved oxygen, and several other physicochemical parameters; (2) species composition and density of the algae populations; (3) species composition and diversity of zooplankton; (4) species composition, diversity, and density of benthic macroinvertebrates; and (5) vertical (bathymetric) distribution and growth of fish. The report also includes recommendations for further research

Stream Research in the Long Term Ecological Research Network

Stream research is currently being conducted at several sites in the Long-Term Ecological Research (LTER) Network, although the primary focus of research at most sites is on terrestrial rather than aquatic ecosystems. To stimulate comparative stream research both inside and outside the Network, we have compiled this data catalog from responses to a questionnaire sent to all LTER sites. In this brief overview, I draw upon information from the following chapters to summarize the range of stream conditions found across the Network. The extent of stream research conducted at an LTER site varies considerably across the Network as a consequence of differences in research objectives among sites, the number of stream researchers in the project, and site funding priorities. There is presently no set of parameters being measured in all LTER stream projects. Hence, the data in this overview are incomplete in the sense that information was not available for all variables from all sites. Nevertheless, the existing data demonstrate the wide range of stream environments to be found in the LTER Network