Light on and Above Coral Reefs: Imaging, Signaling, and Effects of Stress.
Dr. Tom Cronin (University of Maryland).

Coral reefs are the most colorful environments on earth. Coral reef inhabitants have exotic and highly capable visual systems, and the ecology of corals and a number of associated plant and animal species are intimately connected to light availability. This project provides a detailed view of light underwater, including the distribution of ultraviolet, visible, and polarized light throughout the day and across various habitats. Results will be used to help identify specific characteristics of healthy, marginal, and disturbed reefs, based on reflected colors and images; specifically, a custom-built instrument will be used to take ultraviolet and infrared images. A new low-light imaging system for monitoring the reef at night will be tested. Additionally, the behavior of several invertebrates and fishes will be monitored and correlated with changing light conditions during dawn and twilight, the periods when many species begin or end their activity periods.

A goal of this project is to identify relatively simple, noninvasive, and potentially remote means of determining and characterizing the condition of coral reefs using detailed images of reefs, individual corals, and various underwater scenes. Aquarius is needed for the substantial bottom time to accurately place instruments and to support the hours of continuous effort required during measurements. Measurements of reef condition, and individual corals monitored as part of coral bleaching studies, will be coordinated with several ongoing programs in the Florida Keys National Marine Sanctuary. The long-term affects of human-caused changes to water quality (from sedimentation, turbidity, and ozone depletion) that affect underwater light, and perhaps animal behavior are unknown. Results from this study will establish baseline images that can be used to evaluate reef condition, in addition to more conventional parameters already used by other monitoring programs.