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Quantification of Sediment Stress on Hawaiian Reef Corals: Gregory A. Piniak

Project Title: Quantification of Sediment Stress on Hawaiian Reef Corals
Mendenhall Fellow: Gregory A. Piniak, (831) 427-4729,
Duty Station: Santa Cruz, California
Start Date: March 31, 2003
Education: Ph.D., 2001, Ecology, Duke University
Research Advisor: Michael Field, (831) 459-3428,

Project Description: Human activities such as agriculture, ranching, and urbanization have restructured drainage basins in the tropical Pacific, resulting in increased delivery of Piniak devicesediment and contaminants to coral reefs and other coastal ecosystems. Sedimentation has been implicated as a major cause of recent coral reef degradation, and can influence coral physiology as well as community dynamics. However, the specific mechanisms through which sediment inhibits coral production are not well understood. In an effort to understand the physical forcing functions that regulate sediment load on coral reefs, the USGS Pacific Science Center is studying the relationship between coastal hydrodynamics (waves, tidal currents) and sediment transport in Hawaii. The goal of this Mendenhall project is to describe changes in coral physiology associated with these sediment dynamics. The primary approach will be to use a physiological index called scope for growth (SFG) to quantify sediment stress on corals. Laboratory and field experiments will be used to measure coral energy budgets, including both inputs (photosynthesis by symbiotic zooxanthellae, prey capture by the coral host) and daily expenditures (respiration, metabolic waste, mucus production). SFG is the difference between inputs and losses; a positive SFG indicates energy is available for growth, reproduction, or energy storage. Comparing SFG for selected coral species in sediment-impacted and control areas should help identify the physiological pathways responsible for decreases in coral productivity. This project will explore additional approaches to determine the effects of sediment stress, including direct measurement of coral growth and reproductive effort, measuring short-term effects of sedimentation on coral photosynthesis, and using mass spectrometry to document the incorporation of sediment-derived trace metals into coral skeletons.

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Last modified: 16:08:32 Thu 13 Dec 2012