Preliminary Study On The Response Of Foraminifera To Primary Seawater Environmental Factors

Foraminifera is numerous single-celled protozoan species that are distributed globally.They are divided into benthic and planktonic species and live in sediment and seawater,respectively.Foraminiferal individuals are tiny with fast growth and reproduction.Most foraminifera have carbonate shells or cementitious shells that can be preserved in the strata for a long period.Therefore,they are widely used in the reconstruction of paleoenvironments and paleoclimates.Global changes such as global warming,rising sea levels and ocean acidification are influencing marine organisms.Foraminifera is very sensitive to environmental changes and is a good environmental indicator species.Our work focuses on the main environmental factors—temperature,salinity and pH.We study the response of benthic foraminiferal community from the coastal area(Qingdao Bay)to the continental shelf(Yellow Sea)and the planktonic foraminifera Globigerinoides sacculifer from the open ocean(tropical western Pacific Ocean)to these factors.There are four parts of work listed as follows.1.Study on the response of benthic foraminiferal community from the intertidal area in Qingdao Bay to temperatureBenthic foraminiferal community from intertidal zone in Qingdao Bay were cultured at 3 temperatures(6°C,12°C and 18°C)and 4 salinities(15 psu,20 psu,25psu and 30 psu)in laboratory for 10 weeks.A total of 18 species and 2616 living benthic foraminifera were obtained.Our results showed that benthic foraminiferal communities in this area responded very quickly to changes in temperature and salinity,and are particularly sensitive to temperature.Community abundance,species richness,Margalef index and Shannon-Wiener diversity were positively correlated to temperature,and Pielou's evenness was significantly negatively correlated to temperature and salinity.The abundance of the dominant species,Ammonia aomoriensis,A.beccarii and Quinqueloculina seminula,were positively correlated to temperature.The proportion of hyaline Rotaliida was significantly negatively correlated to temperature,whereas the proportion of porcellaneous Miliolida was positively correlated to temperature.The relationships between benthic foraminiferal community parameters and temperature and salinity established in this study can be used to indicate environmental changes in ecological study and may provide a reference for the paleoenvironmental reconstruction.2.Study on the response of benthic foraminiferal community from the intertidal area in Qingdao Bay to pHThe benthic foraminiferal community from the intertidal zone of Qingdao Bay was cultured at 5 pH(pH 8.5,pH 8.0,pH 7.5,pH 7.0 and pH 6.5)for 4 months in laboratory.A total of 15 species and 2246 living benthic foraminifera were obtained.Results showed that the decrease in seawater pH resulted in a significant reduction in the abundance of benthic foraminiferal communities,but increased diversity and evenness.The abundance(N)and proportion(C)of dominant species Ammonia aomoriensis were positively correlated to pH(N=25.6*pH-163.1,p<0.0001;C=0.24*pH-1.36,p<0.0001),and the abundance(N)and proportion(C)of Ammogloblogerina globigeriniformis showed a significant negative correlation with pH(N=-4.1*pH+41.9,p=0.0353;C=-0.21*pH+1.80,p<0.0001).These species could be used as indicator species for the change of seawater pH.Decreased,benthic foraminifera crust type composition changes:vitreous and porcelain foraminifera content decreased and cementitious foraminifera content increased This study indicates that the benthic foraminifera species composition and shell type changes in this area can indicate Changes in seawater pH can be used as a basis for reconstructing the pH value of the ancient ocean.With the decrease of pH,the composition of the benthic foraminifera was altered:the proportions of hyaline and porcellaneous taxa decreased,and the agglutinated taxa increased.Our study showed that the benthic foraminiferal species composition and shell type composition in this area could indicate changes in seawater pH and be used as a basis for reconstructing paleo-ocean pH.3.Study on the response of benthic foraminiferal community from the continental shelf of the Yellow Sea to pHThe benthic foraminiferal community from five stations of different depths in continental shelf of the Yellow Sea was subjected to laboratory culture for 6 weeks and12 weeks at three pH(pH 8.3,pH 7.8 and pH 7.3).A total of 60 species and 5918 living benthic foraminifera were obtained.Our results showed that the declining seawater pH had an adverse effect on benthic foraminiferal community,resulting in a reduction in community abundance,species richness and diversity.The incubation time only had a significant effect on the benthic foraminiferal community parameters in the nearshore stations.With the increase of incubation time,the community abundance increased,while the species richness and diversity decreased.The proportions of benthic foraminifera Lagenammina atlantica,Verneuilinulla advena,V.propinqua,Haplophragmoides applanata,and H.canariensis increased with decreasing pH and these were pH-tolerant species.However,Protelphidium tuberculatum and Cribroelphidium frigidum were highly sensitive to declining pH and decreased with the declining pH.The proportion of hyaline taxa was positively correlated to pH,while the proportion of agglutinated taxa was negatively correlated to pH.Our study showed that the impact of lowering seawater pH on benthic foraminifera varied in different areas in the Yellow Sea.The offshore foraminiferal community was more sensitive to the declining pH than the nearshore one in the Yellow Sea.Especially,benthic foraminifera in the central sea area of the Yellow Sea Cold Water Mass was most vulnerable to the adverse effect of the lowering of seawater pH.4.Study on the response of planktonic foraminifera Globigerinoides sacculifer from the tropical western Pacific Ocean to temperatureThe planktonic foraminiferal community including Globigerinoides sacculifer were collected from the tropical western Pacific Ocean.The individual species were cultured at 22°C and 27°C and the whole communities were cultured at four temperatures(24°C,27°C,30°C and 33°C).The results showed that the growth of G.sacculifer was significantly affected by temperature,and the growth rate(27.72?m/day)at 27°C was significantly higher than that at 22°C(17.28?m/day).The temperature coefficient Q10 between 22°C and 27°C was 2.96.According to the growth rate of body length(17.28-29.72?m/day)obtained in this experiment,it took approximately two weeks for G.sacculifer to reach the adult size(~400?m).Between24°C and 30°C,the equations between length(L)and width(W)of G.sacculifer and temperature(T)were L=(3.87±0.77)T+(75.54±20.33),r~2=0.96 and W=(2.89±0.73)T+(63.66±19.20),r~2=0.94.Our results showed that the length of G.sacculifer would increase 3.87?m with 1°C rise and the width of G.sacculifer would increase2.89?m with 1°C rise.Under laboratory simulated extreme high temperature(33°C),the size of G.sacculifer showed a dramatic decline.We speculated that high temperature had adverse effects on the growth of G.sacculifer.The results also showed that the length/width ratios of G.sacculifer and of the final chamber were basically unchanged between 24°C and 33°C.The morphology(length/width ratio)of G.sacculifer wasn't changed by temperature.