Effects of Solar UV Radiation on Mediterranean Coastal Periphytic Communities

EU Program: ENVIRONMENT
Coordinator: Regas Santas
Contract #: EV5V-CT94-0425, DG-XII
Status: Completed
Year: 1994
Duration: 24 months
EU contact person: Dr. C. Nolan, DG-XII
Partner: Prof. D. P. Häder - Friedrich-Alexander Universität, Institut für Botanik und Pharmazeutishe Biologie, Lehrstuhl für Botanik I, Staudstr. 5 D-91058 Erlangen, Fed. Rep. Germany

Project objectives

To assess the effects of solar UV-B radiation on:

periphytic community structure,
primary productivity, and
macrophyte pigment and protein content.

The study also investigated some solar UV effects on community dynamics of the invertebrate microfauna associated with the macrophyte assemblages.

Brief project description

Due to the high transparency of the East Mediterranean waters to UV, the region where the photochemical processes can be carried on extends as far as 20 metres below surface. Highly productive and diversified macrophyte communities occurring in this zone are therefore exposed to increasing levels of UV radiation - the result of atmospheric ozone depletion.

This study aimed at assessing the impact of solar UV radiation in such macrophyte communities. Periphytic communities were grown on ceramic tiles placed in partial enclosures in the fiels. Three UV treatments were created (PAR only; PAR + UV-A; PAR + UV-A + UV-B) using different combinations of UV-absorbing filters (UV-transparent plexiglas, cellulose acetate, mylar). The experiment was repeated at 3 depths (50cm, 100cm, 150cm) below the surface of the water. Data were collected during a two-year study period on community development dynamics, structure, and primary productivity. Additional parameters monitored included: seasonal, diurnal and spatial fluctuations of UV incidence; spectral distribution of sunlight in the water column under different weather conditions (clear sky, cloud cover); photosynthetic oxygen production of key macrophyte species in situ; PAM fluorescence; chromophoric groups and protein components of the photosynthetic apparatus; standard physical and chemical parameters (temperature, nutrients, pH, etc.). The correlation of the dependent and independent variables provided insight about the role of solar UV radiation in an area of the marine environment and a community type having received little scientific attention to date.