Release of dissolved organic matter by marine seaweeds and distribution of their total organic production to inshore communities

Abstract

Under controlled experimental conditions, release rates of organic matter were estimated for five species of Barents Sea macrophytes and for thirteen species of Black Sea macrophytes. The release rates of different species from the Barents Sea were between 0.9 and 2.9 mg of organic matter per gram (dry wt) of plants per hour (mg g-1 hr-1) in March species from and between 1.7 and 9.8 mg g-1 hr-1 in June. The release rates of different the Black Sea were between 1.25 and 6.1 mg g-1 hr-1 in fast growing plants and between 0.5 and 1.6 mg g-1 hr-1 in slowly growing plants. Approximate quantities of total dissolved organic matter released per year have been calculated to be about 39% of gross production in brown algae, about 38% in red algae, and about 23% in green algae. The rest of the organic matter was released during decomposition of that part of standing stock not consumed by herbivorous animals. About 30% of gross production may be released in this way. Thus, the total flow of dissolved organic matter from seaweeds during growth and after death may be as much as 70% of their gross production. The ecological significance of external organic metabolites released in the surrounding water is discussed.