The Effects Of Regulating-controlling Water Quality By Constructed Wetlands And The Daily Feeding Rhythm Of Macrobrachium Rosenbergii, And The Impacts Of NO₂^--N On Its Energy Metabolism

Since its introduction in1976, Macrobrachium rosenbergii has become one ofChinese major economic freshwater shrimp, culture area and annual yield increases yearby year. Currently, Macrobrachium rosenbergii farming in most region of China is stillmainly adopt traditional farming methods of high density and high water exchange rate,a large number of nitrogen, phosphorus, organic matter et al. were accumulated in theculturing process, and the nutrient-rich water is often discharged into around waterswithout treatment, not only undermine the ecological environment surround culturingregion, but also bring a lot of potential harm to Macrobrachium rosenbergii aquacultureindustry. In recent years, with the development of culturing techniques, can use watertreatment equipment to circularly cleanse culturing water and reuse, which can controlwater quality be in culturing safe range, but the issues of high equipment costs, highenergy consumption, a large number of sludge was produced and need carefulmaintenance et al. were widespread on circulating aquaculture systems.As a new wastewater treatment technology, Wetland can effectively removenitrogen, phosphorus, organic matter, suspended particles and blue-green algae, etc. inaquaculture water, through physical, chemical and biological effects. And have theadvantages of low built and running costs, easy maintenance, etc. This paper focuses onthe study of techniques and effects of regulating-controlling water quality forMacrobrachium rosenbergii culture by constructed wetland intermittent operation, andto compare the growth characteristics of Macrobrachium rosenbergii, get its growthequations of growth characteristics.In addition, the studies about the effects of differentlight cycles conducted the daily feeding rhythm and different concentrations of nitriteconducted the energy metabolism for Macrobrachium rosenbergii culture also havebeen proceeded, in order to obtain better results in water quality control, and improvebreeding efficiency, to get the success of productive culture.According to the experimental results, this paper has presented the applicationtechnology and related parameters of cycle processing productive aquaculture water byconstructed wetlands intermittent operation for Macrobrachium rosenbergii culture. This experiment uses a surface flow (FWS) and horizontal subsurface flow (SF)composite constructed wetland systems, wetland area is582.2m2, includes three unitsof slope area, emergent plants area and impounding reservoir, and the area ratio is1.0:2.3:1.4.The experiment was processed from culture early period (31d) and the constructedwetland also started to operate intermittently, each time for about22%of theexperiment pond aquaculture water, hydraulic loading (HLR) is1.03m/d. Theconstructed wetland system has higher removal efficiency for TAN, NO2--N, NO3--N,PO43--P and CODMn, and the removal rate were45.0%,33.3%,66.4%,35.4%and39.6%respectively, also can control the reproduce of Microcystis aeruginosa andreduce its harm.Combined with microvesicle aerators, water purification nets, andhornwort, chub in water reservoir, the constructed wetlands ecosystem was developedwith intermittent operation without changing the water, nor medication conditions,which can ensure major chemical indicators in a appropriate growth and safe range ofMacrobrachium rosenbergii within culture period. Meanwhile, the mode also hasadvantages of economically viable, energy saving, easy management, etc., to ensure theproductive culture to obtain good results of efficient, Green and healthy.Feeding and metabolism of fodder are the basis for water qualityregulating-controlling. In order to make the constructed wetland ecosystems can betterhandle Macrobrachium rosenbergii productive culture water, and provide a scientificbasis and theoretical parameters for Macrobrachium rosenbergii health culture, thispaper still carry out the following practical researches:The effects of day photoperiod on feeding rhythm, digestive enzyme activity anddigestibility of Macrobrachium rosenbergiiThe experiment set LN(natural light), L0h(continuous darkness), L8h(8h light16hdark), L12h(12h light12h dark), L16h(16h8h dark lighting) and L24h(continuous light)6kinds of light cycle groups, each group has4repeats, then divide24h (1d) into sixperiods by4h interval (0:00~4:00,4:00~8:00,8:00~12:00,12:00~16:00,16:00~20:00,20:00~24:00), concrete ponds culture15d indoor under suitable water environment, tostudy the effects of day photoperiod on feeding rhythm, digestive enzyme activity anddigestion ratio of Macrobrachium rosenbergii. The results show that the feeding rhythmof Macrobrachium rosenbergii is an endogenous rhythm, the feeding rhythm unchangedunder six kinds of photoperiodic conditions, there were a feeding peak hours0:00~4:00,and two sub-peaks in the period16:00~20:00and20:00~24:00. In addition, maindigestive enzymes activity in three organizations of Macrobrachium rosenbergii occursthe activity peaks within the feeding peaks, they are significantly effected by theenvironment of light and dark within feeding low ebb time, and the activity under dark state above light state, while the change rule of dry matter digestibility and proteindigestibility have a high consistency with digestive enzyme activity circadian.The effects of nitrite nitrogen on survival, growth and energy metabolism ofMacrobrachium rosenbergiiThe experiment using a design of single factor and6processing, the NO2--Nconcentration of control group water was0.04mg/L, the test group to adjust the waterNO2--N concentrations with NaNO2solution, were2mg/L,4mg/L,6mg/L,8mg/L,10mg/L respectively, other water environment factors were in a suitable range, thenculture15d in blue plastic box indoor, to study the effects of nitrate nitrogen onsurvival, growth and energy metabolism of Macrobrachium rosenbergii. The resultsshowed that the survival, growth and energy allocation patterns of Macrobrachiumrosenbergii were effected by nitrite nitrogen. Under the stress state, the body catabolismenhanced and anabolic weakened, leading to the depletion of certain nutrients; on theother hand it also makes certain nutrients synthesis is blocked, so that Macrobrachiumrosenbergii slowly grew or even be stagnation. In addition, nitrate nitrogen stress effectthe physiological regulation and behavioral patterns of Macrobrachium rosenbergii, itsappetite decreased, foods intake and the efficiency of energy reduced, leading its growthrate to slow down. The productive culture of Macrobrachium rosenbergii needs to payclose attention to the nitrate nitrogen concentration in water, to ensure its growth withinthe range of CNO2--N≤4mg/L.