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The use of miniaturized digital temperature logging devices on coral reefs is increasing dramatically due to the threat of global warming. Shallow coral reef environments are characterized by extremely high solar radiation and highly transparent seawater, raising the possibility of solar heating of devices deployed in these settings. In this study, we compared temperature measurements under a variety of shading treatments to investigate the potential error associated with high irradiance levels in shallow, clear waters. Results of this experiment showed that mid-day water temperature readings by unshaded loggers were significantly higher by 2.2°C on average compared with shaded loggers. Loggers shielded with reflective tape showed less error but still reported significant heating, with water temperatures that were on average 0.15°C higher than shaded loggers. There were no significant differences among shade treatments during nighttime hours, indicating that irradiance is the source of the errors documented here. Care must be taken to shield temperature loggers from irradiance while providing good circulation of water around the sensors. One option is to place the loggers in a naturally occurring, cryptic or shaded habitat on the reef. When deployed in open reef areas, in mesocosms, or in experimental aquaria, loggers can be shielded in protective, opaque plastic tubes that are open at both ends. [ABSTRACT FROM AUTHOR]

The high cost of building and operating open-flow experimental systems for studies of biological response to ocean acidification (OA) has led to extensive use of short-term incubations in closed-flow systems that do not simulate natural conditions. An inexpensive, highly reliable, open-system that tracks natural diurnal and seasonal changes in water chemistry is described. This approach is based on a gravity-feed seawater supply system that uses a peristaltic pump to regulate CO2 injection rate and a power head that cavitates the injected CO2 into microscopic bubbles that are dissolved immediately. This report describes low-cost methods applicable to small or very large experimental systems. This methodology permits long-term experiments under full sunlight with rapid seawater turnover rate that assures realistic environmental conditions in the experimental chambers. [ABSTRACT FROM AUTHOR]

The article presents a study on the quantitative examination of coral reefs in Hawaii using various descriptive models. It says that the ecological gradient model (EGM) approach provides quantitative method for ranking coral reef condition based on extensive data. It reveals that a series of key ecological metrics are useful in defining the ecological status of a coral reef. Moreover, the natural and anthropogenic ecological factors were significant in determining coral reef condition.