Production and biomass of the seagrass Enhalus acoroides (L.f.) Royle and its epiphytes

Abstract

Annual production and biomass of seagrasses and attached epiphytes was determined for Enhalus acoroides (L.f.) Royle from Papua New Guinea. The leaf growth rate, assessed with the marking technique, resulted in a constant rate during the first two months and was subsequently followed by a decrease in leaf growth of 0.37 mm day −1. The leaf growth increased with 1.8 mm day −1 for an increase of 1°C in water temperature. Production of the leaf blades and basal plant parts, was 17.5 and 5.2 mg ADW shoot −1 day −1, respectively. Total annual mean plant biomass (above- and below-ground), amounted to 600 g ADW m −2, of which the largest part (73%) was contributed by the rhizomes. Flowering occurred all year round. The maximum number of inflorescences (male and female) was observed in June. Successful fruit formation occurred predominantly between April and August. A total of 66 algal epiphytic species was identified on leaves of Enhalus acoroides of which the majority (in number and in abundance) was found in the shallower stations. Annual mean biomass of epiphytes varied from 22 to 78 mg ADW shoot −1. The epiphytes contributed 3–17% to the total annual mean above-ground plant biomass. Annual mean production of epiphytes ranged from 38.5–65 mg ADW m −2 day −1. An estimated 2–9% of the total annual mean above-ground plant production was produced by the epiphytic community.