| The Philippine clam,Ruditapes philippinarum,as a kind of burrowing mollusk,will perform compensatory filter feeding behavior by a characteristic behavior of spraying mud-water.Currently some studies have shown that the mud ejected by the clams has a flocculation effect,and this mud can flocculate pigments,heavy metals and other substances.However,these reports only studied the mud extract,at the present time,whether the clam itself can affect various common substances in the water environment through this characteristic behavior and thus cause certain ecological effects on the seawater environment is not yet clear.In this paper,the common suspended substances in water,such as suspended sediment,marine algae,and microplastics,were used as the objects to explore the effects of the clam filter feeding behavior on turbidity,food particles,and pollutants in the marine water environment and possible mechanisms under different conditions.The main conclusions are as follows:（1）The clam could effectively flocculate suspended sediment in water environment through its filter feeding,the flocculation rate of suspended sediment suspension with a concentration of 0.46 g·L-1 in Zhoushan sea area could reach 95.3%within 60 minutes.This indicated that the filter feeding behavior of clam can effectively reduce the turbidity in the water environment by flocculating the suspended sediment in the seawater,so clam has the ecological effect of purifying the water quality.In addition,the results of Zeta potential detection showed that the mechanism of clam flocculation of suspended sediment was not the principle of electrical neutralization.（2）Among the three marine microalgae,clam had better bioflocculation ability for Phaeodactylum tricornutum（95.7%）and Dunaliella salina（92.2%）through filter feeding within 30 minutes,while for Chlorella vulgaris,the biological flocculation effect was poor（22.3%）.The possible reasons were that Chlorella vulgaris was kind of high-quality bait food particles algae,and its cell size was the smallest among the three algae,so that Chlorella vulgaris was easy for clam to ingest and hardly need to be screened;moreover,the flocculation process of clam on microalgae neither damaged the algae cells nor significantly affects the protein content and amino acid composition of the algae,and the algal cells ccould grow normally after deflocculation;furthermore,The adsorption bridging mechanism mignt be the mechanism of clam flocculating microalgae.（3）The enrichment of microplastics by clam through filter feeding increased with the increase of the concentration of microplastics,and the clam hardly enriched microplastics at low concentrations of microplastics;the accumulation of microplastics by clam through filter feeding decreased with the increase of water depth,and the ability of clams to enrich microplastics was the strongest at 3～4 cm water depth;when the microplastics and algae were in the filter feeding range of the clam at the same time,the enrichment ability of the gill tissues of the clam to microplastics was greatly enhanced,and the gill became the most abundant tissues of the clam;microplastics could first damage the visceral mass of the clam to a certain extent within 24 h,and the SOD activity in the visceral mass was induced faster than CAT;the decontamination experiment showed that the decontamination of microplastics by the clam took more than 3 days.In this study,the filter-feeding process of clam,the effect of filter-feeding and filter-feeding behavior on the ecological effects and mechanisms of various substances in the water environment were discussed,which would be helpful for the cultivation of clam and even other shellfish from the perspective of behavioral ecology,and provide new ideas for water purification,bait delivery,and microplastic pollution prevention and control. |
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