枸杞岛海域铜藻漂浮周期与生长速率研究OA

To elucidate the drivers of rapid biomass accumulation in floating Sargassum horneri populations in the East China Sea and clarify the regulatory mechanisms governing its growth and ontogenetic transitions,this study conducted an in situ simulated floating experiment using raft-cultivated S.horneri collected from Gouqi Island,spanning from October 2024 to April 2025.Monthly monitoring of algal density and relative growth rate(RGR)was performed to characterize the full floating duration and quantify the contribution of RGR to the formation of"Golden Tide"biomass in the region.The key results are summarized as follows:(1)Raft-cultivated S.horneri from Gouqi Island detaches from its cultivation substrates or undergoes thallus fragmentation around mid-October.The detached fragments maintain buoyancy via specialized air bladders,remaining afloat until a large-scale sinking event occurs in late March,yielding a maximum floating duration of 24 weeks.(2)The density of floating S.horneri exhibits a distinct U-shaped temporal pattern:during the vegetative growth phase(mid-October to mid-February of the subsequent year),algal density progressively decreases concurrent with continuous bladder development.This trend is followed by the reproductive growth phase(mid-February to April),during which the steady proliferation of receptacles and gradual degradation of air bladders collectively drive a continuous increase in algal density until final sinking.(3)The mean RGR of whole thalli and isolated branches of raft-derived floating S.horneri is no less than 3.28%/d and 3.75%/d,respectively.Environmental conditions modulate RGR indirectly by regulating the ontogenetic development of floating S.horneri.During the vegetative phase,high RGR is sustained despite a continuous decline in sea surface temperature(SST)and lower incident light intensity relative to the reproductive phase.Conversely,during the reproductive growth phase,RGR progressively declines until growth ceases entirely,even as ambient temperature and light conditions gradually improve.These findings demonstrate that the extended floating duration,in combination with the high RGR maintained during the vegetative growth phase,synergistically drives substantial biomass accumulation throughout the floating period.This study provides critical baseline data for accurately quantifying the contribution of raft-derived S.horneri to the total"Golden Tide"biomass in the East China Sea.