Effects Of Reproduction Of Planktonic Copepods Fed On Diatom Diets:Meta-analyses Of Laboratory Experiments

Diatoms and copepods are the major components of primary producers and primary consumers in marine ecosystem,and there is a complex relationship between them.Since 1993,Ianora et al proposed that diatom diets show an opposite effect on the egg viability of marine planktonic copepods,many researchers have conducted various studies on the relationship between diatoms and copepods.However,it is difficult to have a systematic and comprehensive understanding of the interactions from these conflicting results,due to the various species of diatoms,copepods and control algae,as well as the different experimental conditions and methods.We use the meta-analysis techneques by collecting and screening of research literature published all over the world,extracting data and combining effect sizes,to quantitatively examine and assess the effects of diatom diets on the reproduction of planktonic copepods and their responds.The data were extracted from 32 laboratory studies,and formed 295 matched data(including 140 comparisons of the egg production rate,EPR;114 comparisons of hatching success,HS;and 41 comparisons of fecal pellet production),totally involving 18 diatom species,19 non-diatom species,and 18 copepod species.The subgroup analysis by treatment diatoms,copepods,and control algae were conducted to provide an insight into the inhibition effect from diatom diets and the response of copepods in taxonomic classification.The Results As Follow:1.The diatoms inhibited the Egg Production Rate(EPR)of copepods to a certain extent,SMD+=-0.48(greater than-0.8).There is a large difference between the species of different diatoms,and Thalassiosira spp.(THA,not including T.weissflogii)are a type of diatoms,which promote the EPR of copepods compared to control algae,and Phaeodactylum tricornutum(PHA)is another type of diatom,which inhibits the EPR of copepods compared to control algae.The EPR of the Acartia spp.and Calanus spp.are inhibited by the diatom diets,and it is impossible to judge whether the EPR of the Temora spp.are affected by the diatom diets.In terms of reproductive response to copepod spawning rates,the Prorocentrum spp.(PRO)are significantly better than the diatom diets,and the differences between the diatoms and Rhodomonas spp.(RHO)and Isochrysis spp.(ISO)were not significant.Polyunsaturated Aldehydes(PUA)did not explain the inhibitory effect of copepod egg production rate.The reproductive response of copepod EPR and the nutritional grade and cell morphology of diatom,and feeding preference of copepod were more closely related.2.Diatoms significantly inhibited the Hatching Success(HS)of copepods in SMD+=-1.255(less than-0.8).Different degree of inhibit effect of diatoms have significant differences,including THA,Skeletonema spp.(SKE)and PHA,and the inhibition of THA significantly is greater than other diatoms.The HS in the three main copepod genus were inhibited by diatoms,and the inhibitory effect on Temora spp.was greater than on Acartia spp.and Calanus spp.Compared with diatoms,control algae were more beneficial to the HS of copepods,and PRO was significantly superior to ISO,RHO in between.PUA was a major factor in controlling the HS of copepods.Meanwhile,there are other oxylipin material produce toxic effect on HS of copepods fed on diatom diets.Both of the nutrition and toxic materials in diatom diet influence the HS of copepods,and toxic factors play a major role.3.The Fecal Pellets production rate(FP)of copepods increased significantly,and SMD+=0.891(greater than 0.8).The higher excretion rate means the shorter residence time of diatoms in the copepod guts,indicating that the copepods can't digest and assimilate diatoms effectively.