Influence Of Zooplankon Grazing On The Production And Transfer Of Dimethylsulfide

Dimethylsulfide （DMS） is the most important, abundant volatile biogenicorganic sulfide in the ocean. It plays an important role in global climate. Zooplanktoncan promote the DMS production and was an important link in DMS biogeochemicalcycle. The influence of zooplankton grazing on DMS and dimethylsulfoniopropionate（DMSP） were investigated by the culture of short-term （24h） and medium-long-term（8⁹d） experiment in the laboratory, we also studied the influence of the abundanceand distribution of zooplankton in Jiaozhou Bay on DMS and DMSP. The mainresults were as follows:1. Influence of Calanus sinicus grazing on DMS and DMSP（1） The ingestion rates （IR） of C. sinicus increased with the concentration of I.galbana, and peaked at15×10⁴cells/mL, then decreased subsequently. C.sinicusgrazing promoted the production of DMS, and the increasing range was1.80¹0.73%.On the whole, C.sinicus grazing promoted the DMSPdproduction. The promotion wasthe most at the concentration of20×10⁴cells/mL, DMSPdproduction increased by97.95%induced by C.sinicus grazing. Both DMSP_zand DMSP_rconcentrationsincreased and then decreased with the food concentration. The total DMSP_zandDMSP_rconcentrations reached the maximum in the concentration of15×10⁴cells/mL,which was1.93times of the concentration of10×10⁴cells/mL.（2） IR of C.sinicus had a similar trend with filtration rate （FR）, which increasedand then decreased with the increase of salinity in diffferent salinity （20PSU,25PSU,30PSU and35PSU） experiment. IR and FR of C.sinicus peaked at30PSU, whichwere3.1787×10³cells·ind^-1·h^-1and0.2333ml·ind^-1·h^-1, respectively. C.sinicus grazingpromoted the DMS production at four salinity levels, and the promotion increasedwith decreasing salinity. On the whole, C.sinicus grazing decreased DMSP_pproduction. The decrease of DMSP_pproduction was the most in30PSU, which was34.95%. Both DMSP_zand DMSP_rcontents increased, decreased and then increased with the increasing salinity. The total DMSP_zand DMSP_rcontents reached themaximum in30PSU, which was8.84times of that at20PSU.（3） The influence of C. sinicus grazing on DMS was different in different diets（Isochrysis galbana8701, Chaetoceros curvisetus, Gymnodinium sp. and Emilianiahuxleyi） experiment. C. sinicus grazing on I. galbana and C. curvisetus promoted theDMS production, which were7.87%and70.49%, respectively. However, promotionwere not found in teatments of Gymnodinium sp. and Emiliania huxleyi. DMSP_zandDMSP_rcontents of Gymnodinium sp. and E. huxleyi were higher than those of I.galbana and C. curvisetus. The total DMSP_zand DMSP_rproduction in Gymnodiniumsp. treatment was40.87times of those in C. curvisetus treatment.2. The influence of Brachionus plicatilis and Harpacticus grazing on DMS andDMSP production（1） B. plicatilis grazing Chlorella sp. promoted the DMS production, and thepromotion was more significant with the time increasing. The DMS production of thetreatment （with B. plicatilis） was10.32times of the control （without B. plicatilis） atday8. The relationship between DMS and B. plicatilis biomass was significantlypositive （P<0.01）, the decrease of Chlorella sp. cell density was significantlypositively correlated with the increase of DMS （P<0.01）. There was significant differencebetween the DMS and cell indensity of the control and the treatment （P<0.01）.（2） Harpacticus grazing I. galbana promoted the DMS production. Theincreasing range was16.46%. Harpacticus grazing decreased DMSP_pproduction, andthe decreasing range was1.6%³0.15%. The decrease of I. galbana cell density wasnot significantly correlated with the increase of DMS （R=0.31）. There was significantdifference between the DMS, cell indensity and DMSP_pproduction of the control and thetreatment （P<0.01）.3. Influence of the abundance and distribution of zooplankton in Jiaozhou Bay onDMS and DMSP（1） The mean abundance of zooplnkton in Jiaozhou Bay varied in differentmonthes. The hightest value （128.3ind/m³） occured in April, the lowest value （16.05ind/m³） occured in November. The zooplankton abundance was inhomogeneous in its horizontal distribution. The densest of winter was at station C1, and the dentest ofspring were at station A2and E1. The DMSP_pwas significantly positively correlatedwith the abundance of zooplankton in November2010（P<0.05）.（2） The dominant species of copepod in Jiaozhou Bay varied among differentmonthes. C.sinicus was always dominant species through all the cruises. Dominantspecies of copepod accounted for1/2of dominant species of zooplankton.（3） The mean abundance of copepod in Jiaozhou Bay varied among differentmonthes. The hightest value （100.8ind/m³） occured in April, the lowest value （2.494ind/m³） occured in November. The copepod abundance was inhomogeneous in itshorizontal distribution. The densest of winter was at station C1, and the dentest ofspring were at station A2and E1. The DMSP_pwas significantly positively correlatedwith the copepod abundance of November2011（P<0.05）. The DMSPdwassignificantly positively correlated with the copepod abundance of January2011（P<0.05）.（4） The mean abundance of C. sinicus in Jiaozhou Bay varied among differentmonthes. The hightest value （29.94ind/m³） occured in May, the lowest value （1.5356ind/m³） occured in November. The C. sinicus abundance was inhomogeneous in itshorizontal distribution. The densest of winter was at station C1, the dentest of springwere at station C3and E1. The DMS was significantly positively correlated with theC. sinicus abundance of January2011（P<0.05）.