Preliminary Study The Reason Of Cyclotella Asterocostata Occurrence In Early Spring In The Outlet Of Jialing River

The Cyclotella asterocostata occur in every early spring as expected in the outlet ofJialing river since the alage waterbloom survery in the spring of2005,and occur withvarying degree.In nature,biological growth and activity rhythm are often associatedwith the annual rhythm changes of inmeteorological factors, in the inmeteorologicalfactors, temperature and light change annually, due to the relationshipof the catalytic activities of life activity with temperature is closely, and thus theoccurrence of Cyclotella asterocostata is associated with the annual temperature change.Throughout the year, spring and autumn have the same climate period (the same watertemperature, other water environmental factors are the same). why the Cyclotellaasterocostata activities only occur in the spring, not in the fall, what are thereasons. to unlock the mystery of Cyclotella asterocostata Occurrence only in thespring, after years of exploratory studies and environmental factor analysis experiments onthe mechanism of the algae occurrence in the spring,but have no results, Afteranalysis, the reason of the Cyclotella asterocostata occur in the early spring isassociated with low-temperature-induction-in-winter,sothe low-temperature induction experiment on the alage were carried out in the spring of2009、2010and2011.This study were carried out through on-site monitoring、 sampling、 laboratoryincubation、 growth temperature tests and variable temperature experiments, analyzedthe relationship of the growth of Cyclotella asterocostata and temperature, to determine thethe effect of low-temperature induction on the growth of the alage and reveal the reason ofthe Cyclotella asterocostata occurrence only in the early spring.The results:(1)The growth temperature test: The growth temperature tests showed thatthe three growth temperatur basis points(the minimum, optimum, maximum)of Cyclotellaasterocostata was9.5℃,13.0℃and15.0℃, the growth temperaturerange is9.5~15.0℃.(2) High-low temperature processing test: when the algae cultured followed thesequential temperatures of growth temperature(9.5～15.0℃)、 high-temperature（15.5℃、16.5℃、17.5℃）and growth temperature，growth unimodal only emerged inthe first growth temperature range; while when the algae cultured followed the sequentialtemperatures of growth temperature(9.5～15.0℃)、high-temperature （15.5℃、16.5℃、 17.5℃）、low-temperature（7.0～9.0℃） and growth temperature，both growthtemperature range emerged unimodal, Thus the above analysis shows that the growth ofalage needs the effect of low-temperature induction. induction low-temperature is7.0～9.0℃, the dormancy high-temperature is15.5～17.0℃.(3) high-temperature processing test: when the algae cultured followed the sequentialtemperatures of growth temperature(9.5～15.0℃)、high-temperature （18.0℃、19.0℃、20.0℃）and growth temperature，growth unimodal only emerged in the first growthtemperature range; while when the algae cultured followed the sequential temperatures ofgrowth temperature(9.5～15.0℃)、high-temperature （15.5℃、16.5℃、17.5℃）、low-temperature（7.0～9.0℃） and growth temperature，only in the first growth temperaturerange emerged unimodal,but the growth rate was very low near zero in the second growthtemperature range. Thus the above analysis shows that the alage cultured in the growthtemperature after treatment in the high temperature(18.0℃、19.0℃、20.0℃),the alage didnot grow,and then cultured in the temperature of7.5℃~19.0℃,the alage did resumegrowth also,the critical growth lethal high temperature of Cyclotella asterocostata is18.0℃.(4)The relationship of the low-temperature treatment approach with the algae growth:in the induction low-temperature range（7.0～9.0℃）, the higher the temperature is，thesmaller the maximum growth rate will be, and the longer the processing time takes，thehigher the maximum growth rate will occur.The conclusion:(1)The growth temperature range is9.5~15.0°C, induction low-temperature rangewas7.5~9.0°C,dormance high-temperature range was15.5~17.5°C, lethal hightemperature was18.0℃、19.0℃.(2) The annual activity rhythm of Cyclotella asterocostata were: low-temperature inwinter induces its growth (fission), and sequent dormancy high-temperature leads to thedeverenalization, then the alage stops growing; but the deverenalization will be relieved inwinter, and when Spring comes, the alage recovers growth.