An energy budget for Porites porites (Scleractinia)

An energy budget for Porites porites (Pallas) was determined for specimens from 10 m depth on the Fore Reef of Discovery Bay, Jamaica, between July 1984 and July 1985. Evidence for habitual zooplankton ingestion was not obtained, and P. porites appears to be largely autotrophic. Out of the daily photosynthetically fixed energy, 26% is used for animal respiration and growth, 22% for zooxanthellae respiration and growth, and <1% for colony reproduction as mature planulae; 45% remains unaccounted for. Colony respiration, net photosynthesis, colony skeleton and tissue growth, zooplankton ingestion, reproductive effort and energy content of tissues were measured. Energy loss as continuous mucus secretion was not detected, but may occur by an alternative route via mucus tunics, which occur periodically in situ and in the laboratory. The energy budget suggests that a considerable excess of photosynthetically fixed energy is produced on an ideal sunny day at 10 m depth. This surplus may be required for periodic rather than continuous energy demands, or may be essential to survive less-than-ideal days, when net photosynthetic input is reduced.Contribution No. 357 of the Discovery Bay Marine Laboratory, University of the West Indies     

Assessing Retrospective National Water Model Streamflow with Respect to Droughts and Low Flows in the Colorado River Basin

Streamflow monitoring in the Colorado River Basin (CRB) is essential to ensure diverse needs are met, especially during periods of drought or low flow. Existing stream gage networks, however, provide a limited record of past and current streamflow. Modeled streamflow products with more complete spatial and temporal coverage (including the National Water Model [NWM]), have primarily focused on flooding, rather than sustained drought or low flow conditions. Objectives of this study are to (1) evaluate historical performance of the NWM streamflow estimates (particularly with respect to droughts and seasonal low flows) and (2) identify characteristics relevant to model inputs and suitability for future applications. Comparisons of retrospective flows from the NWM to observed flows from the United States Geological Survey stream gage network over 22 years in the CRB reveal a tendency for underestimating low flow frequency, locations with low flows, and the number of years with low flows. We found model performance to be more accurate for the Upper CRB and at sites with higher precipitation, snow percent, baseflow index, and elevations. Underestimation of low flows and variable model performance has important implications for future applications: inaccurate evaluations of historical low flows and droughts, and less reliable performance outside of specific watershed/stream conditions. This highlights characteristics on which to focus future model development efforts.