Project Title: Quantification of Sediment Stress on Hawaiian Reef Corals
Mendenhall Fellow: Gregory A. Piniak, (831) 427-4729, gpiniak@usgs.gov
Duty Station: Santa Cruz, California
Start Date: March 31, 2003
Education: Ph.D., 2001, Ecology, Duke University
Research Advisor: Michael Field, (831) 459-3428, mfield@usgs.gov |
Project Description: Human activities such as agriculture, ranching, and urbanization have restructured
drainage basins in the tropical Pacific, resulting in increased delivery of
sediment 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 updated 1-June-2004 (krw)
