W. Schramm, H. Gualberto, C. Orosco
Rates of net photosynthesis (mg O2g-1dw h-1) and exudation of dissolved organic matter (mg DOC g dw-1h-1) of six dominant macrophytes (the seaweeds Padina japonica, Laurencia papillosa, Sargassum sp., Gelidiella acerosa, Gracilaria acerosa and the seagrass Thalassia hemprichii) from a tropical reef (Mactan Island, Cebu, Philippines) were determined in the laboratory under standard conditions (35%o salinity, 29 °C, 150 W m-2). Further the effects of desiccation and increased temperature on stress release of dissolved organic carbon from the plants were investigated. Under standard conditions, DOC exudation rates ranged from 4.0 to 9.3% of net primary production. Desiccation and temperatures above 35 °C considerably increased the DOC release. In situ measurements showed that desiccation and temperatures experienced by emerging plants may enhance organic release, although they will seldom reach detrimental levels. Diurnal variations observed in DOC concentrations in the seawater over the reef area may be related to stress release of organic matter from marine benthic macrophytes under natural conditions. © 1984 IEEE
Meeresbotanische Abteilung, Institut fur Meereskunde, D-2300, Kiel, Dusternbrooker Weg 20, Germany; Marine Research Office, University of San Carlos, Cebu, Philippines
