The Physiological And Ecological Characteristics Of Bullacta Exarata In Laizhou Bay And Its Ecological Security Assessment

Bullacta exarata belong to Mollusca, Gastropoda, Opisthobranchia,Cephalaspidae, Atyidae, Bullacta. In the Yellow River Estuary Area, the B. exaratawas not controlled by the cast seedling measures, the distribution range expanded fast.The distribution range in2008was three times of the distribution range in2003(fromthe State Oceanic Administration People’s Replublic of China that is to beunpublished). The B. exarata proliferated fast in the natural waters that far from thebreeding areas and became the dominant species, which will affect the localecological environment and the bentonic organism. From August2011to November2012, the summer distribution of B. exarata and its relationship with the sedimentenvironment, B. exarata physiological ecology, the dispersal ability and the effect onthe ecological envrionmentwere researched in the the Yellow River Estuary Area. Thisstudy provided the basic data for the evaluation of the B. exarata fast proliferation’seffect on the Laizhou Bay ecological environment. And the Analytic HierarchyProcesswas also used to evaluate the ecological security risk of B. exarata in LaizhouBay.This evaluation will be of great importance in safeguarding the ecological safetyof mariculture system, north China Sea.The results were as follows:1Preliminary study on characteristics and living environment of B. exaratapopulation in Yellow River Estuary，ChinaIn order to understand the interaction between B. exarata and sedimentalenvironment, population of B. exarata and sediment characteristics were investigated atthe typical distribution area of the Yellow River Estuary in August,2011. The resultswere as follows．(1) B. exarata was mainly distributed in mudflats with median diameter φ (Mdφ) ranging from3.73-5.25; and the sediment types were composedof silt, salt-sand and sand-salt.(2) The average organic content and Chl-aconcentration in surface sediment was1.39%and2.65μg/g, it was significantly higherin the south intertidal zone than in the north of the Yellow River Estuary which theaverage organic content and Chl-a concentration in surface sediment was1.39%and2.65μg/g.(3) The average population densities was16.7ind/m2, it was significantlyhigher in the south intertidal zone than in the north of the Yellow River Estuary whichthe average population densities was0.6ind/m2. The relationship between populationdensities (x) and average shell length (y) could best be expressed as the linearequation: y=-0.1801x+19.184，R2=0.776. B. exarata individual specifications andpopulation densities was inversely proportional, it was that the higher populationdensities, the smaller individual specifications.(4) Taylor’ power law, Iwao’s patchregression and Morisita index analysis results showed that the spatial pattern B.exarata population in the Yellow River Estuary belonged to the clumped and negativebinomial distribution theoretically.(5) There were positive relationships between thedensity of B. exarata and organic content or Chl-a, suggesting that food source mightbe one of the mainly limited factors for the distribution of B. exarata population.2Influence of salinity on oxygen consumption and ammonia excretion rateofdifferent sizes of B. exarataInfluences of different body sizes and salinity (18,23,28,33,38) on oxygenconsumption rate and ammonia excretion rate of B. exarata were studied in July,2012in the Laizhou Bay. The results were as follows:(1) the effects (P <0.05) of body size,salinity and their combination on oxygen consumption rate and ammonia excretionrate of B.exarata were significant. The oxygen consumption rate and ammoniaexcretion rate significantly increased with increasing salinity in the range of18-28(P<0.05), both raise to the peak value at salinity of28, but decreased with increasingsalinity in the range of33-38(P<0.05).(2) The relationship between oxygenconsumption rate (OR) or ammonia excretion rate (NR) and dry weight of soft-tissue(W) could be expressed as the exponential equation OR or NR=aWb.(4) The O andN mole ratio of B. exarata ranged from8.38to29.16. The O: N ratio value washighest at salinity of33, but it significantly decreased at salinity of38.3Effects of season and different body sizes on energy budget of B. exarata in the Laizhou BayThe energy budget of different body sizes B. exarata were investigated in situ inMay, August, October and December,2012in the Laizhou Bay. The ingestion rate,oxygen consumption rate and ammonia excretion rate of B. exarata were measured inthe four months and the energy budget equation was built. The results were as follows:the highest rates of ingestion (IR), oxygen consumption (OR1) and ammonia (NR1)were found in summer (August), and the lowest values were obtained in winter(December). The relationship between ingestion rate and living weight (W) could beexpressed as the exponential equation IR=aWb, where b ranged from0.32to0.53. Inthe equations erected on the energy budget of the B. exarata, the ratios of growth,respiration, ejection, mucus and excretion make up28.49%～60.45%,16.88%～38.59%,10.84%～31.54%,1.79%～6.22%and <3%of the total energy, respectively.Energy assimilated in growth and those consumed in respiration dominated the modeof the energy allocation of B. exarata. In the spring, summer and fall, the proportion offood energy allocated to growth were significantly higher than the proportion in thewinter（P <0.05）.4The dispersal ability and the effect on the ecological environment of B. exaratain Laizhou BayThe dispersal ability and the effect on the ecological environment of B. exaratawere researched in Laizhou Bay, it showed that the relationship between the B. exaratacocoon volume and the wet weight were significant linearpositive correlation. Thedifferent sizes of the cocoonhave differentsettling rate, the settling rate range is from3.44to6.00cm/s. The relationship between the settling rate and cocoon volume(V) orthe cocoon wet weight(W) are all significant linear positive correlation. Therelationship between B. exarata itselves movement speed and the shell length ispositive correlation, the relationship could best be expressed as the linear equation:y=0.0139x+0.0298, R2=0.8043(n=20，F>0.01). The difference of the biodiversityindex, richness and uniformity between the south and north of Yellow River EstuaryArea is indistinctive. The introduction of B. exarata in Laizhou Bay did not causemuch impact to local biodiversity. The effect of B. exarata to the sediment environmentwas researched in Laizhou Bay, it showed that the B. exarata populations did not causemuch impact to the tidal zone sediment environment, including the organic content,chlorophyll-a content, ammonia nitrogen density and nitrite concentration. In the short term, the introduction of B. exarata in Laizhou Bay did not cause obvious evenpernicious threaten to the sediment environment.5The ecological security risk assessment of B. exatata in Laizhou BayThis chapter is based on completed biological invasion process of B. exatata,which designed6primary indexes and30secondary indexes, and also designed threerisk gradewhich included can be introduced, has certain risk and prohibits theintroduction to construct the risk assessment system. And the invasive risks for B.exatata in Laizhou Bay was assessed through using analytic hierarchy process(AHP).The evaluation came to the conclusion that the introduction has certain risks.