| Gloiopeltis furcata (Gigartinales, Endocladiaceae), is one of the common seaweed along thenorthwestern Pacific coast, which distributes widely in China coast. Gloiopeltis furcata occurs in themiddle to high intertidal zone, and maintains regional richness of maritime flora and fauna species withother seaweeds. Gloiopeltis furcata experiences a variety of adverse conditions since tidal motion,including desiccation, high temperature and osmotic stress. In addition, frequently human disturbancereduces species richness. In this study, we investigated the population ecology of Gloiopeltis furcata onXiaoheishan Island in north Shandong peninsula. Early life stage development was described using theoptical microscope with an imaging system; the change of photosynthetic activity of Gloiopeltis furcataduring low tidal in response to desiccation was investigated as well. The main results showed asfollowing:1. Spatial and seasonal variations in biomass and length of Gloiopeltis furcata fromXiaoheishan Island, Shandong, China and the influence factorsAs an important economic red macroalga, Gloiopeltis furcata have been severely depleted due tohuman disturbance. Populations of G. furcata around the Xiaoheishan Island, Shandong, China wereinvestigated to determine their spatial-seasonal variations in biomass and length as well as theirinfluence factors. At island scale, ANCOVA showed that both bottom and Baardseth index hadsignificant effects on the biomass and length of G. furcata. The steady substrate and high Baardsethindex were benefited for its growth. At microhabitat scale, two-way ANOVA showed that wave actionand tidal level had significant effects on the biomass and length of G. furcata. Wave wash and moderatetidal level increased its growth. In addition, one-way repeated measures ANOVA showed that seasonalvariations of biomass and length of G. furcata were significant. The length and biomass of G. furcataincreased rapidly from March to April, and reached peak values in early summer.2. Early life stage development of Gloiopeltis furcata (Gigartinales, Endocladiaceae) fromnorthern ChinaTo enrich information on its life history, the early developmental process of G. furcata from northernChina was investigated using free-hand section and microexamination methods. Early life stagedevelopment includes the formation of carpogonial branch, spermatangia, cystocarp and tetrasporangia andspores germination. Results showed that one auxiliary cell and one adjacent supporting cell constituted an ampulla. Auxiliary cell was usually near the basal part of the ampulla and generated several two-tothree-celled carpogonial branches. One spermatangial mother cell originated in the superficial cortical celland produced single spermatangia. After fertilization, carpogonium formed a connecting filament whichfused with the auxiliary cell ultimately. Many branched gonimoblast filaments were produced from auxiliarycell and generated into carpospores. Mature cystocarps protruded on the thalli surface showing somesubspherical-shaped structures. Tetrasporangium developed from the inner cortical cell generated fourtetrasporangia by cruciform division. Mature tetraspores and carpospores were released, attached to thebottom of Petri dishes through the stickum within12h, and then divided through regular binary fission.Undergoing a month of cultivation the spores grew up to discoid crusts with diameters ranging from55to60μm. Growth of G. furcata was initiated with the dome-shaped apical cell division to form the central axialstructure, being the first to confirm the occurrence of apical growth of this species.3. Photosynthetic activity of Gloiopeltis furcata (intertidal red macroalga) in response todesiccationIn this study, the diurnal changes of photosynthesis activity in response to various tidal patterns,the relationship between photosynthetic activity and tissue water content, and the interactive effect ofdesiccation and irradiance on photosynthetic activity in Gloiopeltis furcata were investigated by usingportable pulse amplitude modulated (PAM) fluorometer. Results showed that Fv/Fmdecreased morerapidly during noon low tide in comparison with that during morning and evening low tide. During themorning low tide, Fv/Fmdecreased slowly in the beginning of desiccation, however, it decreasedrapidly throughout the evening low tide. Fv/Fmrecovered to the initial values on the same day no matterwhen low tide occurred, suggesting the occurrence of dynamic photoinhibition. These featuresendowed G. furcata with an ability to adapt to the periodic desiccation in high intertidal rocks. Themaximum (Fv/Fm) and effective (ΦPSII) quantum yield declined with the decrease of tissue watercontent (TWC). However, photosynthetic activity could recover completely when TWC exceeded6%,showing a strong ability to tolerate desiccation. The relationships between TWC and Fv/Fmand ΦPSIIwere the following: Fv/Fm=0.68+(0.0044-0.68)/[1+(TWC/66.96)5], R2=0.99;ΦPSII=0.585+(0.004-0.585)/[1+(TWC/73)10], R2=0.99. ANOVA result further showed that the interactiveeffect of irradiance and desiccation on photosynthetic activity was significant, and that thephotoinhibition degree increased with elevation of irradiation and duration of desiccation. The extreme condition (6h desiccation at1000μmol photons·m-2·s-1) resulted in a serious photoinhibition, with thelongest period of complete recovery for photosynthesis activity. |
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