Zengjie Jiang

Detrimental effects of reduced seawater pH on the early development of the Pacific abalone

The hatching process of the Pacific abalone Haliotis discus hannai was prolonged at a pH of 7.6 and pH 7.3, and the embryonic developmental success was reduced. The hatching rate at pH 7.3 was significantly (10.8%) lower than that of the control (pH 8.2). The malformation rates at pH 7.9 and pH 8.2 were less than 20% but were 53.8% and 77.3% at pH 7.6 and pH 7.3, respectively. When newly hatched larvae were incubated for 48 h at pH 7.3, only 2.7% of the larvae settled, while more than 70% of the larvae completed settlement in the other three pH treatments. However, most 24 h old larvae could complete metamorphosis in all four pH treatments. Overall, a 0.3-unit reduction in water pH will produce no negative effect on the early development of the Pacific abalone, but further reduction in pH to the values predicted for seawater by the end of this century will have strong detrimental effects.

The distributions of dissolved nutrients in spring of Sungo Bay and potential reason of outbreak of red tide

There are over 20 years of history of shellfish and seaweed polyculture in Sungo Bay.There had not been reported the outbreak of red tide in the Bay.However,in May 2011,there occured large scale red tide outbreak,which almost spread over the total bay,and which caused higher mortality of cultivated shellfish.It is very important to understand the cause of red tide and to provide data for future environmental protection and aquaculture management.We just carried out one survey of environment monitoring before the outbreak of the red tide.Therefore,in this paper,the distributions of sea water temperature,salinity and dissolved nutrients were investigated in Sungo Bay in April 2006 and 2011,so as to understand the cause of the outbreak of red tide.The results showed that the concentration of dissolved inorganic nitrogen(DIN),phosphate(PO3-4)and silicate(Si)in Sungo Bay of 2011 was 5.6,3.2 and 1.3 times of the same period in 2006,respectively.The mole ratio of DIN/P,Si/P and Si/DIN was(66.33±47.16),(35.12±21.44)and(0.82±0.77),respectively,which was seriously deviated from the Redfield ratio.Dissolved nutrients showed obvious block distribution,their horizontal distribution was characterized by a concentration decrease from the open sea to the inner bay,and there were two sub-peak values near the Yatou River and Bahegang areas,the isolines were almost overlaps with low-salinity isolines.The probable causes of red tide outbreak were discussed from four aspects including nutrients,hydrological characteristics,kelp and temperature.

The phosphorus cycle in the Sanggou Bay

The phosphorus cycle is studied during 2013–2014 in the Sanggou Bay (SGB), which is a typical aquaculture area in northern China. The forms of measured phosphorus include dissolved inorganic phosphorus (DIP), dissolved organic phosphorus (DOP), particulate inorganic phosphorus (PIP), and particulate organic phosphorus (POP). DIP and PIP are the major forms of total dissolved phosphorus (TDP) and total particulate phosphorus (TPP), representing 51%–75% and 53%–80%, respectively. The concentrations and distributions of phosphorus forms vary among seasons relative to aquaculture cycles, fluvial input, and hydrodynamic conditions. In autumn the concentration of DIP is significantly higher than in other seasons (P<0.01), and higher concentrations are found in the west of the bay. In winter and spring the phosphorus concentrations are higher in the east of the bay than in the west. In summer, the distributions of phosphorus forms are uniform. A preliminary phosphorus budget is developed, and shows that SGB is a net sink of phosphorus. A total of 1.80×107 mol/a phosphorus is transported into the bay. The Yellow Sea is the major source of net input of phosphorus (61%), followed by submarine groundwater discharge (SGD) (27%), river input (11%), and atmospheric deposition (1%). The main phosphorus sink is the harvest of seaweeds (Saccharina japonica and Gracilaria lemaneiformis), bivalves (Chlamys farreri), and oysters (Crassostrea gigas), accounting for a total of 1.12×107 mol/a. Burial of phosphorus in sediment is another important sink, accounting for 7.00×106 mol/a. Biodeposition by bivalves is the major source of phosphorus in sediment, accounting for 54% of the total.

Effects of temperature and salinity on the development of the amphipod crustacean Eogammarus sinensis

The amphipod crustacean Eogammarus sinensis has useful features that make it suitable for use in the aquaculture of fish and large decapod crustaceans. In this study, we investigated the effects of temperature and salinity on the development, fecundity, survival, and growth rate of E. sinensis. The results show that temperature significantly affected E. sinensis development, but salinity. As temperature increased, the duration of E. sinensis embryonic development decreased. Fecundity was affected significantly by temperature and the combination of temperature and salinity, but by salinity alone. In addition, high temperatures accelerated E. sinensis juvenile growth rates, whereas high salinity reduced it. Therefore, our data suggest that E. sinensis tolerates a wide range of salinities and that temperature has more significant effects than salinity on the embryonic development, fecundity, and growth of E. sinensis. Our results shall be useful for mass production of this species for use in aquaculture.

Applicability of Perinereis aibuhitensis Grube for fish waste removal from fish cages in Sanggou Bay, P. R. China

The present study investigated the applicability of integrated polychaete-fish culture for fish waste removal to offset negative impact induced by organic benthic enrichment. A field study demonstrated that deposition rate was significantly higher underneath the fish farm than that in control area. The material settling under the farm was characterized by a high amount of fish feces (45%) and uneaten feed (27%). Both feeding rate (FR) and apparent digestibility rate (ADR) increased with decreasing body weight, as was indicated by significantly a higher rate observed for the groups containing smaller individuals in a lab study. The nutrient in fresh deposited material (De) was higher than that in sediments collected under the farm (Se), resulting in lower feces production but higher apparent digestibility rate for the De group as feeding rate was similar. Consequently, higher nutrient removal efficiency was observed in the De group. A mass balance approach indicated that approximately 400–500 individuals m−2 is required for removing all waste materials deposited underneath the fish farm, whereas abundance can be lower (about 300–350 individuals m−2) when only the fish waste needs to be removed. The results showed that a significant amount of waste had been accumulated in the fish cages in Sanggou Bay. The integration of fish with P. aibuhitensis seems promising for preventing organic pollution in the sediment and therefore is an effective strategy for mitigating negative effect of fish farms. Thus such integration can become a new IMTA (integrated multi-trophic aquaculture) model in Sanggou Bay.

Environmental remediation potential of Perinereis aibuhitensis (Polychaeta) based on the effects of temperature and feed types on its carbon and nitrogen budgets

ABSTRACT The effects of three temperatures (15°C, 20°C and 25°C) and four feed types (artificial feed, AF; sediment, SM; fish faeces, FF; and fish meat, FM) on the growth, carbon budget and nitrogen budget of the polychaete Perinereis aibuhitensis were evaluated over a 35 day period. The final body weight and specific growth rate (SGR) of P. aibuhitensis were significantly affected by temperature and feed types (T, F = 15.831, P = 0.000; Feed, F = 81.827, P = 0.000), but the interaction between these factors was not significant (F = 0.435, P = 0.848). The worms achieved the highest SGR in the AF group at 20°C. However, the SGR in the SM group was only half that of the other groups. The food conversion efficiency (FCE) was significantly lower at 25°C than at 15°C and 20°C (P < 0.05). The FCE was highest in the FM group (P = 0.000), with a mean of 39.83%. The apparent digestibility rate (ADR) at 25°C was significantly higher than at 15°C and 20°C (P < 0.05). These findings suggest that the higher FCE coupled with ADR (78.48%) resulted in higher SGR in worms that were fed artificial feed at 20°C. The slow growth in the SM group was attributed to the lower organic content in sediment and the higher expenditure of carbon and nitrogen in faeces and metabolism. The proportion of total C and N deposited was lower in groups fed with the higher-quality feed used for fish cage farming. Most of feed carbon and nitrogen were released into the water by polychaetes, which was good for the sediment environment recovery under the fish cages.

The potential of ocean acidification on suppressing larval development in the Pacific oyster Crassostrea gigas and blood cockle Arca inflata Reeve

We evaluated the effect of pH on larval development in larval Pacific oyster (Crassostrea gigas) and blood cockle (Arca inflata Reeve). The larvae were reared at pH 8.2 (control), 7.9, 7.6, or 7.3 beginning 30 min or 24 h post fertilization. Exposure to lower pH during early embryonic development inhibited larval shell formation in both species. Compared with the control, larvae took longer to reach the D-veliger stage when reared under pH 7.6 and 7.3. Exposure to lower pH immediately after fertilization resulted in significantly delayed shell formation in the Pacific oyster larvae at pH 7.3 and blood cockle larvae at pH 7.6 and 7.3. However, when exposure was delayed until 24 h post fertilization, shell formation was only inhibited in blood cockle larvae reared at pH 7.3. Thus, the early embryonic stages were more sensitive to acidified conditions. Our results suggest that ocean acidification will have an adverse effect on embryonic development in bivalves. Although the effects appear subtle, they may accumulate and lead to subsequent issues during later larval development.

Size fraction of phytoplankton and the contribution of natural plankton to the carbon source of Zhikong scallop Chlamys farreri in mariculture ecosystem of the Sanggou Bay

The biomass and size fraction of phytoplankton in terms of chlorophyll a (Chl a) was measured during four cruises conducted in April, July, October 2013 and January 2014 in mariculture area, the Sanggou Bay, China. Results show that total Chl a levels in the surface seawater of the Sanggou Bay generally range from 0.10 to 20.46 μg/L, with an average value of 2.13 μg/L. Nano-phytoplankton was the most important size-fraction and accounted for about 65.1% of total Chl a. In order to evaluate the importance of the “protozoan trophic link” for energy transfer from the microbial loop to filter-feeding feeders, Zhikong scallop Chlamys farreri was then offered a natural planktonic community as potential prey. Results show that scallops obtained carbon source from natural plankton with the rate of 11 033.05 μg/(g·d). Protists (nanoflagellates and ciliates) were the dominant source of carbon retained by scallop (48.78%). The microbial loop provided 58.45% of the carbon source for farmed scallops. These results indicate that the microbial loop represent a valuable trophic resource in mariculture system of the Sanggou Bay.

Effects of temperature and salinity on mortality and metabolism of Ophiopholis mirabilis

Abstract Specimens of the ophiuroid Ophiopholis mirabilis were acclimated at 15°C and 30 PSU and then assessed for temperature and salinity tolerance as these parameters were increased or decreased by 1 unit per day. Oxygen consumption, ammonia excretion, and moisture content were measured at different temperatures (5, 10, 15, 20 and 25°C) and salinities (25, 30 and 35 PSU). Ophiopholis mirabilis could tolerate temperatures of 0–24°C in the experimental situation, and mortality was 0% in the salinity range of 22 to 48 PSU at 15°C. Two-way ANOVA showed that the oxygen consumption, ammonia excretion and Q10 (used to describe the temperature sensitivity of respiration) were significantly affected by temperature and salinity and the interactions between the two factors were significant. The interaction for moisture content was not significant. Respiration of O. mirabilis was most sensitive at 10–15°C. Stepwise multiple regression analysis revealed a significant positive relationship between oxygen consumption, temperature and salinity. Ammonia excretion and moisture content of the brittle stars showed an inverse relationship with salinity but a positive relationship with temperature. The results suggested that the temperature and salinity tolerance of O. mirabilis is determined by a range of values present in its habitat (i.e. 30–32 PSU and −1 to 22°C). The main cause of mortality of ophiuroids in the present study might be a change in tissue moisture beyond their regulatory capacity.

Tolerance, Oxygen Consumption and Ammonia Excretion of Ophiopholis sarsii vadicola in Different Temperatures and Salinities

There are more than 2000 species of brittle stars in the world. For most of them, many scientific questions including basic characteristics of eco-physiology are still unknown. In the present study, Ophiopholis sarsii vadicola acclimated at 15°C, salinity 31, were assessed for temperature and salinity tolerance. Its oxygen consumption and ammonia excretion were studied at different temperatures (5, 10, 15, 20, 25°C) and salinities (25, 30, 35). O. sarsii vadicola could tolerate 0–24°C and no brittle star was dead in the salinity range of 19–48 in the experimental situation. Two-way ANOVA showed that the oxygen consumption and ammonia excretion normalized with both dry mass and wet mass, Q10, which is used to describe the temperature sensitivity of respiration, and moisture content were significantly affected by temperature and salinity, and the combined effects of the two factors were significant. Stepwise multiple regression analysis revealed that logarithmic oxygen consumption and ammonia excretion showed a significant positive relationship with logarithmic temperature and salinity. The logarithmic moisture content of the brittle stars showed an inverse relationship with logarithmic salinity, but a positive relationship with logarithmic temperature. This suggests that the tolerance of temperature and salinity of brittle stars is closely related to their living environment, and that the effects of temperature on oxygen consumption are more significant at higher salinity, and that the ammonia excretion is less affected by salinity at lower temperatures.