Effects Of Different Water Exchange Frequency And Water Depth On The Physicochemical Environment Of Sea Cucumber(Apostichopus Japonicus) Culture Ponds

Physicochemical environment of culture ponds is particularly important to thegrowth of sea cucumber. Water exchange is one of the most important factors toaffect the sea cucumber aquaculture during the farming management. The presentstudy examined the effects of different water exchange frequency and water depth onthe physicochemical environment of sea cucumber culture ponds so as to providetheoretical basis for optimizing sea cucumber culture technology. The experiment wasconducted in sea cucumber culture ponds of Jing Bay aquaculture base in HomeyGroup, Rongcheng Shandong from April2012to May2013. Five sea cucumberculture ponds were selected as experimental ponds and different water exchangefrequency and water dept are set: pond1water exchange frequency was set toone-third of monthly tidal rhythm; pond2was set to two-thirds of monthly tidalrhythm and the pond3was used as a control pond and water was changed followingthe monthly tidal rhythm. Water depth of the three ponds is1.7m. Pond3was set tothe lowest water depth, that is1.7m; pond4was set to the middle water depth, that is2.2m; pond5was set to the highest water depth, that is2.5m. The water of differentwater depth ponds was changed following the monthly tidal rhythm. The water, thefallout, the sediment and the adhesion matrix samples were collected from the5pondsevery month. After that, TPM, POM, POC, chlorophyll a, pheophytin, PTN, nitratenitrogen, nitrite nitrogen, ammonia nitrogen, active phosphate of the water andsedimentation rate, organic matter content, organic carbon, chlorophyll a, pheophytin,total nitrogen of the fallout and organic matter content, organic carbon, organicnitrogen, chlorophyll a, pheophytin, total nitrogen, nitrate nitrogen, nitrite nitrogen,ammonia nitrogen, total phosphorus, active phosphate of the sediment and organicmatter content, organic carbon, chlorophyll a, pheophytin, total nitrogen of theadhesion matrix were determined to compare and analyze the effects of differentwater exchange frequency and water depth on the physicochemical environment ofthe sea cucumber culture ponds. Experimental results showed that:1The effects of different water exchange frequency on the physicochemicalenvironment in the upper part of sea cucumber (Apostichopus japonicus) culturepondsIn the water, chlorophyll a in pond1was significantly higher than that in pond2(P<0.05); the nitrate nitrogen in pond2was significantly lower than that in pond 3(P<0.05); ammonia nitrogen, active phosphate in pond2were significantly lowerthan those in pond1and3(P<0.05). In the fallout, sedimentation rate in pond2and3was significantly higher than that in pond1(P<0.05); the organic carbon in pond1was significantly higher than other2ponds (P<0.05); the other physicochemicalindexes had no significant difference in these ponds (P>0.05). Moreover, the bodyweight of the sea cucumber in pond2were significantly larger than those in other2ponds (P<0.05). Hence, it is comprehensively concluded that the water exchangefrequency in pond2with10times per month is the best for the upperphysicochemical environment and the growth of sea cucumber under the experimentalconditions of the present study.2The effects of different water exchange frequency on the physicochemicalenvironment at the bottom of sea cucumber (Apostichopus japonicus) culturepondsIn the sediment, the organic matter content in pond1and2was significantlyhigher than that in pond3(P<0.05); the organic carbon, organic nitrogen andchlorophyll a in pond1were significantly higher than other2ponds (P<0.05); thepheophytin, the total nitrogen, nitrate nitrogen, ammonia nitrogen, total phosphorusand active phosphate in pond2and3were significantly lower than those in pond1(P<0.05). In the adhesion matrix, the organic matter content in pond2and3wassignificantly higher than that in pond1(P<0.05); the organic carbon, chlorophyll a inpond1were significantly higher than other2ponds (P<0.05); the pheophytin in pond3was significantly lower than that in pond1(P<0.05); the total nitrogen in pond2and3was significantly lower than that in pond1(P<0.05). Moreover, the body weight ofthe sea cucumber in pond2were significantly larger than those in other2ponds(P<0.05). Hence, it is comprehensively concluded that the water exchange frequencyin pond2with10times per month is the best for the bottom physicochemicalenvironment and the growth of sea cucumber under the experimental conditions of thepresent study.3The effects of different water depth on the physicochemical environment in theupper part of sea cucumber (Apostichopus japonicus) culture pondsIn the water, chlorophyll a in pond3was significantly higher than that in pond4(P<0.05); the nitrate nitrogen in pond4was significantly lower than that in pond5(P<0.05); ammonia nitrogen, active phosphate in pond4were significantly lowerthan those in pond3and5(P<0.05). In the fallout, sedimentation rate in pond4and5was significantly higher than that in pond3(P<0.05); the organic carbon in pond3was significantly higher than other2ponds (P<0.05); the other physicochemicalindexes had no significant difference in these ponds (P>0.05). Moreover, the bodyweight and survival rate of the sea cucumber in pond4were significantly larger thanthose in other2ponds (P<0.05). Hence, it is comprehensively concluded that thewater depth in pond4with middle water depth (2.2m) is the best for the upperphysicochemical environment and the growth of sea cucumber under the experimentalconditions of the present study.4The effects of different water depth on the physicochemical environment at thebottom of sea cucumber (Apostichopus japonicus) culture ponds In the sediment, the organic matter content, organic carbon, organic nitrogen inpond4were significantly higher than those in pond3and5(P<0.05); activephosphate in pond3was significantly lower than that in pond5(P<0.05); totalnitrogen, total phosphorus in pond3and5were significantly lower than those in pond4(P<0.05); In the adhesion matrix, the organic matter content in pond2and4wassignificantly higher than that in pond5(P<0.05); the organic carbon in pond5wassignificantly higher than other2ponds (P<0.05); chlorophyll a in pond5wassignificantly higher than that in pond3(P<0.05); the pheophytin in pond3wassignificantly lower than that in pond5(P<0.05); the other physicochemical indexeshad no significant difference in these ponds (P>0.05). Moreover, the body weight andsurvival rate of the sea cucumber in pond4were significantly larger than those inother2ponds (P<0.05). Hence, it is comprehensively concluded that the water depthin pond4with middle water depth (2.2m) is the best for the upper physicochemicalenvironment and the growth of sea cucumber under the experimental conditions of thepresent study.To sum up, it is concluded that the moderate water exchange frequency inpond2is the best for physicochemical environment of sea cucumber culture pondsfrom the nitrate nitrogen, ammonia nitrogen, active phosphate in the water,sedimentation rate in the fallout, the organic matter content, the pheophytin, the totalnitrogen, nitrate nitrogen, ammonia nitrogen, total phosphorus, active phosphate in thesediment, the organic matter content, the total nitrogen in the adhesion matrix and thebody weight of the sea cucumber in the barricading; it is concluded that the moderatewater depth in pond4is the best for physicochemical environment of sea cucumberculture ponds from the nitrate nitrogen, ammonia nitrogen, active phosphate in thewater, sedimentation rate in the fallout, the organic matter content, organic carbon,organic nitrogen in the sediment, the organic matter content in the adhesion matrixand the body weight and survival rate of the sea cucumber in the barricading.