Seasonal population dynamics of Sargassum fusiforme (Fucales, Phaeophyta), Suo-Oshima Is., Seto Inland Sea, Japan—development processes of a stand characterized by high density and productivity

Abstract

Seasonal population dynamics of Sargassum fusiforme, one of the most important edible macroalgae in Japan, were studied. Recruits were mainly generated by vegetative reproduction at the margins of filamentous holdfasts. They first appeared in late spring and peaked in summer as upright thalli of the previous generation withered. After producing recruits, holdfasts withered indicating that holdfasts were also annual, the same as upright thalli. All recruits produced main branches and became new upright thalli in early autumn. During this transitional period, the thallus density decreased due to the crowded conditions induced by simultaneous growth initiation. After this early mortality, however, thallus density remained almost constant over much of the growth season. Thallus growth continued during winter and the stand biomass peaked in spring. During this biomass accumulation, development of a thallus size hierarchy was moderate and no size-dependent mortality was observed. Main branch number per thallus was also constant until spring, indicating the main branches also persisted after being produced in early autumn. This lack of severe intraspecific competition both at a thallus and main branch level is supported by the ambient wave condition of the habitat which gives moderate undulation and enables light and nutrients to be supplied to each thallus, and allowed the S. fusiforme stand to maintain its densely-packed feature with a high productivity.

Vegetative Reproduction Is More Advantageous Than Sexual Reproduction in a Canopy-Forming Clonal Macroalga under Ocean Warming Accompanied by Oligotrophication and Intensive Herbivory

“…Sargassum species generally have perennial holdfasts (analogous to rhizoids), stipes (analogous to stems), and annual shoots (i.e., main branches), which show large seasonal variations in biomass and length, with the exception of annual species such as S. horneri [ 18 , 19 , 20 , 21 ]. In temperate Sargassum species, including S. fusiforme , these shoots commonly germinate from stipes during summer, grow between autumn and spring, and decay during the subsequent summer after the production of propagules via sexual reproduction [ 18 , 20 ]. Moreover, vegetative reproduction via the regeneration of new shoots from holdfasts has been reported in several Sargassum species, including S. fusiforme [ 22 , 23 , 24 ].…”

“…This species is edible and has been cultivated in these countries. Due to its commercial importance, several studies on the ecological and physiological traits of this species have been conducted [ 20 , 22 , 33 , 37 ], although the effects of ocean warming, nutrients, and herbivory on its reproductive traits have not been examined. Novel knowledge of the reproductive traits of this species may improve seeding methods for its cultivation.…”

Inhibition Effect of Sodium Concentrations on the Anaerobic Digestion Performance of Sargassum Species

“…Seaweed is a highly attractive energy crop as feedstock for anaerobic digestion with the advantages of nonrequirement for land or fertilizers, rapid growth rates, high biomass yields, high content of easily hydrolyzable sugars, and low lignin content. , Sargassum sp., brown seaweed, is widely distributed in the South China Sea and the East China Sea with 130 taxonomically accepted species and has been commonly used as seafood, heath products for its antioxidant production, and adsorbent for heavy metal sorption in the environment; it can also be used for bioenergy production. , Sargassum sp. is a suitable raw material for methane production, and the biochemical methane potential (BMP) of Sargassum sp.…”

The effects of desiccation and salinity gradients on the PSII photochemical efficiency of an intertidal brown alga, Sargassum fusiforme from Kagoshima, Japan

“…The desiccation treatments were assigned based on the duration of tidal exposure at the study site (e.g. 1–3 h emersion during the spring low tide; Yoshida & Shimabukuro 2017). The ΔF / F m ' of PSII was measured as the response parameter throughout the desiccation and salinity experiments.…”

“…2015). This macroalga dominates its habitat from late winter to early summer and individuals can be found growing on rocky substrata in the lower intertidal zone, which is periodically exposed to air for a few hours during the low tide (Yoshida & Shimabukuro 2017). This species is known as a perennial species; however, with the exception of the holdfast and young new shoots erect thalli featuring branches and primary laterals typically disappear during summer.…”