Seasonal growth and reproduction of Enhalus acoroides (L.f.) Royle in a shallow bay in the western Gulf of Carpentaria, Australia

Abstract

Seasonal growth of Enhalus acoroides, a tropical seagrass, was measured at Groote Eylandt (14˚S,136˚30′E) by the hole-punch method. Over the one-year study period, only the three youngest leaves of each shoot grew faster than 10 mm leaf^-1 day^-1 . The second-youngest leaf grew the fastest, with peak growth in January when water temperature was highest (33˚C). As a proportion of total leaf length, the youngest leaf grew fastest (3·5% day^-1 ). Leaf growth was highest (13·0–17·0 mm leaf ^-1 day ^-1 ) from September to March, when the water temperature exceeded 30˚C, but significantly less (about 6 mm leaf ^-1 day ^-1 ) in June and July, when water temperatures were 23–24˚C. Leaf growth was positively correlated with water temperature and mean minimum water depth. Leaves were longest in November and shortest in July and August. Leaf length was positively correlated with water temperature, and leaves were longest when their growth rate was high. The production of new shoots was greatest during September–November, as water temperature increased. Shoots decayed and flowers were produced throughout the year.