Hypnea musciformis (rhodophyta): ecological influence on growth¹
1989
Seasonal variations in growth, biomass, phenology, and phycocolloid content were studied in a population of Hypnea musciformis (Wulfen in Jacquin) Lamouroux on the coast of the state of São Paulo. H. musciformis grows epiphytically on Sargassaum cymosum C. Agardh in a zone ca. 0.5 m wide at the lower spring tide. It also epiphytizes, but to a lesser extent, Laurencia scoparia J. Agardh and occasionally Bryothamnion seaforthii (Turner) Kützing and Acanthophora spicifera (Vahl) Bargesen. Seawater temperatures vary from 19°C in winter to 29°C in summer. Variations in H. musciformis biomass (32-190 g dry weight · m⁻²), were controlled by several factors, notably seawater temperature, diurnal lower spring tides on sunny days accompanied by calm seas soon followed by rough water, and by grazine, especially by Gammaridea (amphipods) and Aplysia (sea-hares). Fertile tetrasporophytes were present all year, their frequency varying from 22-99%. Cystocarpic plants were rare; male thalli were not found. Carrageenan fields varied from 48-66% of dry weight. Lowest values of carrageenan occurred when sea-water temperatures were high (26-29° C) and biomass was low or, when biomass was high but frequency of fertile tetrasporophytes was highest. Mean field growth in plastic containers initiated from branches of H. musciformis (ca. 0.1 g) over a 28-day period was 0.48, 0.88, 1.30, and 1.53 g fresh weight, respectively, from summer to spring.
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