Effect Of Seawater Acidification On Community Of Meiofauna And Ingestion Rate, Development And Reproduction Of Harpacticoid

Ocean acidification has caused wide attention. In the present study, we evaluatedthe effects of seawater acidification on the community of meiofauna and ingestionrate, development and reproduction of harpacticoid. Main results of present studywere as follows:1. The study was conducted to the meiofauna community from sandy and siltysandybeaches by simulating CO2concentration increasing in carbon dioxide climateincubator to preliminarily evaluate effects of seawater acidification on meiofauna andthe main taxa.For microsocm experiment with meiofauna community from sandy beach, totalabundance of meiofauna was not significantly affected by seawater acidificationbefore day28, while the abundance of copepod, nematode and total meiofauna wassignificantly affected at pH7.30on56d. Especially, the increasement of copepodabundance was significantly inhibited in acidic microcosms contrast with controlmicrocosms on56d. There was distinctly different species composition of copepodand nematode community between control and acidic microcosm on56d. Thedominant species of copepod and nematode were replaced in acidic microcosm.For microcosm experiment with meiofauna community from silty sand beach,the abundance of copepod was seriously inhibited by seawater acidification on56d.Abundance of nematode was significantly decreased by seawater acidification beforeday28but was not significantly affected in the anaphase of experiment. Speciescomposition of copepod and nematode community were also affected by seawateracidification on56d, the dominant species were replaced in acidic microcosms.The56days microcosm experiments demonstrated that the abundance ofmeiofauna and the community structure of nematode and copepod were significantlyaffected at pH7.30, while the reponses to the seawater acidification were different for different meiofauna taxa from different benthic environments under differentexposure time.2. In the present study, we evaluated the effects of seawater acidification oningestion rates of two harpaticiods: Tisbe sp. and Tigriopus japonicus, which wereexposed to seawater that had been equilibrated with CO2and air to reach pH8.10,7.70,7.30and6.50for4hours. The ingestion rate was extremely significantlyaffected for Tis. sp.(p<0.01) and significantly affected for Tig. japonicus (p<0.05) byseawater acidification. With the decrease of seawater pH value, the ingestion ratespresented different trends between the two copepods. The ingestion rate of Tis. sp.remained stable at pH8.10and7.70, and it sharply declined when the pH levels wereless than7.70. While the ingestion rate of Tig. japonicus rose outstandingly when thepH levels were less than7.30, and it was stable when the pH ranged from8.10to7.30.These results demonstrate that the effects of seawater acidification on the ingestionrates of copepods might be species-specific, and the copepods which come fromdifferent habitats might have different tolerant capabilities when facing oceanacidification.3. In the present study, we studied the effect of seawater acidification on thedevelopment and reproduction of Tis. sp. over multiple generations. The acidificationcondition of pH7.30was simulated by the carbon dioxide climate incubator. Theresults showed that: there was no significant effect of seawater acidification on thefollowing indexes: survival rate, developmental time of copepodite and the number ofborn nauplius within24days. Seawater acifdification significantly decreased the ratioof female to male in the second and third generation but not in the first generation.The number of egg clutch was significantly decreased by seawater acidification in thetwo observed generations. The developmental time of nauplius was only lengthenedin the first generation but not in the following two generations, and the developmentaltime of copepodite was not affected in all the three generations so that thedevelopment delay only present in the stage of nauplius and naupliar of Tis. sp. mightadapt the acidic environment gradually. The effects of seawater acidification on the reproduction of Tis. sp. were mainly in the sex ratio and the female reproductivecapacity which could affect the survival of the population.