DRY-WEIGHT AND CHEMICAL-COMPOSITION (CHN) IN RELATION TO POPULATION-DENSITY OF CULTIVATED TISBE-HOLOTHURIAE (COPEPODA, HARPACTICOIDA)

CARBON

Growth characters and photosynthetic capacity of Gracilaria lemaneiformis as a biofilter in a shellfish farming area in Sanggou Bay, China

Experiments on growth characters and ecological functions of the macroalgae Gracilaria lemaneiformis, collected from south China, were conducted in polyculture areas of kelp and filter-feeding bivalve in Sanggou Bay in Weihai City, Shandong, in north China from May 2002 to May 2003. The results of 116 days cultivation showed that the average wet weight of alga increased 89 times from 0.1 to 8.9 kg rope(-1), with an average specific growth rate ( based on wet weight) of 3.95% per day. The most favorable water layer for its growth was 1.0 - 1.8 m below the surface in July and August, with an average specific growth rate of 8.2% per day in 30-day experiments. Photosynthetic activity changed seasonally, with an average of 7.3 mg O-2 g dw(-1) h(-1). The maximum rate (14.4 mg O-2 g dw(-1) h(-1)) was recorded in July, or 19.3 mg CO2 g dw(-1) h(-1), while the minimum (0.40 mg CO2 g dw(-1) h(-1)) was in April. This study indicated that the culture of G. lemaneiformis is an effective way to improve water quality where scallops are cultivated intensively.

Bioremediation potential of the macroalga Gracilaria lemaneiformis (Rhodophyta) integrated into fed fish culture in coastal waters of north China

Fed fish farms produce large amounts of wastes, including dissolved inorganic nitrogen and phosphorus. In China, fish mariculture in coastal waters has been increasing since the last decade. However, there is no macroalgae commercially cultivated in north China in warm seasons. To exploit fish-farm nutrients as a resource input, and at the same time to reduce the risk of eutrophication, the high-temperature adapted red alga Gracilaria lemaneiformis (Bory) Dawson from south China was co-cultured with the fish Sebastodes fuscescens in north China in warm seasons. Growth and nutrient removal from fish culture water were investigated in laboratory conditions in order to evaluate the nutrient bioremediation capability of G. lemaneiformis. Feasibility of integrating the seaweed cultivation with the fed fish-cage aquaculture in coastal waters of north China was also investigated in field conditions. Laboratory seaweed/fish co-culture experiments showed that the seaweed was an efficient nutrient pump and could remove most nutrients from the system. Field cultivation trials showed that G. lemaneiformis grew very well in fish farming areas, at maximum growth rate of 11.03% day(-1). Mean C, N, and P contents in dry thalli cultured in Jiaozhou Bay were 28.9 +/- 1.1%, 4.17 +/- 0.11 % and 0.33 +/- 0.01 %, respectively. Mean N and P uptake rates of the thalli were estimated at 10.64 and 0.38 mu mol g(-1) dry weight h(-1), respectively. An extrapolation of the results showed that a 1-ha cultivation of the seaweed in coastal fish fanning waters would give an annual harvest of more than 70 t of fresh G. lemaneiformis, or 9 t dry materials; 2.5 t C would be produced, and simultaneously 0.22 t N and 0.03t P would be sequestered from the seawater by the seaweed. Results indicated that the seaweed is suitable as a good candidate for seaweed/fish integrated mariculture for bioremediation and economic diversification. The integration can benefit economy and environment in a sustainable manner in warm seasons in coastal waters of north China. (c) 2005 Elsevier B.V. All rights reserved.

A new three-phase culture method for Manila clam, Ruditapes philippinarum, farming in northern China

Studies on reproduction, hatchery management, and culture of Manila clams Ruditapes philippinarum were carried out in an attempt to optimize their culture conditions and techniques. Results from these studies led to the development of a three-phase culture method for Manila clam farming in northern China. The key components of the new method were: 1) early spawning and over-wintering indoors (greenhouse); 2) optimized larval culture conditions and techniques; 3) juvenile rearing in shallow, fertilized nursery ponds; 4) optimized stocking size and density and substrate for mudflat grow out. Broodstock were maturated indoors for a month from early April to early May. Primarily because of higher water temperatures in the greenhouse the clams spawned more than one month earlier than in the natural environment. From May to July, juveniles were reared for 1-2 months indoors to a size of 2.0-3.0 mm in shell length before being moved to outdoor, pre-disinfected, nursery ponds. Juveniles were then reared in the nursery ponds for one month to about 1.0 cm before being transferred to the mudflat for grow out. Juvenile clams in nursery ponds grew considerably faster than in the natural environment probably because of higher temperatures and more abundant natural food. During grow out, the clams were reared for 4-7 months until they reached a market size (3.0-3.3 cm). Juveniles produced after August were over-wintered in the greenhouse in which the water temperature was about 3 degrees C higher than that of the outdoor environment. Juveniles grew at an average rate of > 20 mu m day(-1), while in the natural environment no growth was observed during winter because of low temperatures. Juveniles in the greenhouse grew to 2-3 mm by the following March before being moved into outdoor nursery ponds. The three-phase culture method not only shortened the production period from spawn to market size from 24-36 months to about 10-14 months, but also prolonged the spawning season from 2 to 7 months, resulting in increased production of seed and market-size clams. Compared with the traditional method, the new method could increase the yield of market-size clams by 10-11 times, and increase the profit per ha mudflat by as much as 124 times and the profit per kg market-size clams produced by 13 times. (c) 2006 Elsevier B.V. All rights reserved.

Hydrogen permeation and corrosion behaviour of high strength steel 35CrMo under cyclic wet-dry conditions

Hydrogen permeation behaviours of high strength steel 35CrMo under different cyclic wet-dry conditions have been investigated by using Devanathan-Stachurski's technique. Four electrolytes were used: distilled water, seawater, seawater containing 1500 ppm H2S and seawater containing 0.03 mol L-1 SO2. The corrosion weight loss of 35CrMo in the wet-dry cycles was measured simultaneously. The experimental results show that hydrogen can be detected at the surface opposite to the corroding side of the specimen during wet-dry cycles and the permeation current density during a wet-dry cycle showed a maximum during the drying process. The hydrogen permeation was obviously promoted by Cl- ions, H2S and SO2. The hydrogen permeation in the real marine atmosphere has also been investigated. There is a clear correlation between the amount of hydrogen permeated and the corrosion weight losses. Results show the importance of hydrogen permeation that merits further investigation.

Hydrogen permeation behavior and corrosion monitoring atmospheric of steel in cyclic wet-dry environment

Hydrogen permeation of 16Mn steel under a cyclic wet-dry condition was investigated by Devanathan-Stachurski's electrolytic cell with a membrane covered on the exit side by a nickel layer and the weight loss was measured for each wet-dry cycle. The results show that hydrogen permeation current change with different atmospheric environment: distilled water, seawater, and seawater containing 100 ppm H2S. The results show that seawater can induce an increase in the hydrogen permeation current due to the hydrolyzation reaction. And after the increase, equilibrium is reached due to the equilibrium of hydrolyzation reaction effect and the block of the rust layer. On the other hand, H2S contamination also can induce an increase in the maximum hydrogen permeation current due to the hydrolyzation reaction. And H2S contamination delays the time that hydrogen permeation is detected because of the formation of the FeS(1-x) film. The FeS(1-x) film can block the absorption of hydrogen onto the specimen surface. The surface potential change and the pH change of the metal surface control the hydrogen permeation current. And a clear linear correlation exists between the quantities of hydrogen permeated through the 16Mn steel and the weight loss. Based on the linear correlation, we monitored the corrosion rate by monitoring the hydrogen permeation current by a sensor outside. Good coherences were shown between results in laboratory and outside.

CO2H2O and energy exchange of an Inner Mongolia steppe ecosystem during a dry and wet year

We used an eddy covariance technique to measure evapotranspiration and carbon flux over two very different growing seasons for a typical steppe on the Inner Mongolia Plateau, China. The rainfall during the 2004 growing season (344.7 mm) was close to the annual average (350.43 mm). In contrast, precipitation during the 2005 growing season was significantly lower than average (only 126 mm). The wet 2004 growing season had a higher peak evapotranspiration (4 mm day(-1)) than did the dry 2005 growing season (3.3 mm day(-1)). In 2004, latent heat flux was mainly a consumption resource for net radiation, accounting for similar to 46% of net radiation. However, sensible heat flux dominated the energy budget over the whole growing season in 2005, accounting for 60% of net radiation. The evaporative rate (LE/R-n) dropped by a factor of four from the non-soil stress to soil water limiting conditions. Maximum half-hourly CO2 uptake was -0.68 mg m(-2) s(-1) and maximum ecosystem exchange was 4.3 g CO2 m(-2) day(-1) in 2004. The 2005 drought growing stage had a maximum CO2 exchange value of only -0.22 mg m(-2) s(-1) and a continuous positive integrated-daily CO2 flux over the entire growing season, i.e. the ecosystem became a net carbon source. Soil respiration was temperature dependent when the soil was under non-limiting soil moisture conditions, but this response declined with soil water stress. Water availability and a high vapor pressure deficit severely limited carbon fixing of this ecosystem; thus, during the growing season, the capacity to fix CO2 was closely related to both timing and frequency of rainfall events. (c) 2007 Published by Elsevier Masson SAS.

Behavioural responses by yaks in different physiological states (lactating, dry or replacement heifers), when grazing natural pasture in the spring (dry and germinating) season on the Qinghai-Tibetan plateau

Using heterogeneous vegetation in alpine grassland through grazing is a necessary component of deintensification of livestock systems and conservation of natural environments. However, better understanding of the dynamics of animal feeding behaviour would improve pasture and livestock grazing managements, particularly in the early part of the spring season when forage is scarce. The changes in behaviour may improve the use of poor pastures. Then, enhancing management practices may conserve pasture and improve animal productivity. Grazing behaviour over 24 In periods by yaks in different physiological states (lactating, dry and replacement heifers) was recorded in the early, dry and later, germinating period of the spring season. Under conditions of inadequate forage, the physiological state of yaks was not the primary factor affecting their grazing and ruminating behaviour. Forage and sward state affected yaks' grazing and ruminating behaviour to a greater extent. Generally, yaks had higher intake and spent more time grazing and ruminating during the later part of the spring season, following germination of forage, than during the earlier dry part of the season. However, the live weight of yaks was less during pasture germination than during the early dry part of the season because the herbage mass is low, and the yaks have to expend much energy to seek feed at this particular time. (c) 2007 Elsevier B.V. All rights reserved.

Digestibility, nutrient balance and urinary purine derivative excretion in dry yak cows fed oat hay at different levels of intake

A feeding trial A as conducted at the farm of Qinghai Academy of Animal and Veterinary Science, Xining, China during 1996 - 1997 with three dry yak cows (initial body weight 163 - 197 kg, age 5 - 6 years) by using 3 x 3 Latin Square Design to determine the effect of levels of feed intake on digestion, nitrogen balance and purine derivative excretion in urine of yak cows. The animals were fed oat hay (nitrogen 13.5 g/kg dry matter (DM), metabolisable energy 8.3 MJ/kg DM), i.e., 0.3, 0.6 and 0.9 of voluntary intake (VI). Each intake treatment lasted for 17 days and the samples (feeds, faeces and urine) were collected during last 7 days of each period. The results indicate that digestibility of dietary DM, OM, NDF and ash declined when intake levels increased from 0.3 to 0.9 VI [DM, from 66.1% to 59.1% (P < 0.05); OM, from 68.1% to 59.9% (P < 0.05); NDF, from 62.1% to 54.3% (P < 0.05); and ash, from 33.9% to 11.8% (P < 0.05)]. Around 0.10 g N/kg W-0.75 was deficient daily in yak cows at 0.3 VI, and positive N balances were observed at 0.6 and 0.9 VI. Intake levels significantly (P < 0.05) affected total PD excretion in yak urine. The proportion of allantoin increased (P < 0.05) and uric acid decreased (P < 0.05) as intake level of feed increased. (C) 2004 Elsevier B.V. All rights reserved.