桑沟湾贝藻养殖区附着生物生态效应研究

附着生物又称污损生物，是附生在海洋设施和生物体表面的动物、植物和微生物等生物的总称（Azis et al., 2001）。附生在养殖器材和生物体表面的数量巨大的附着生物，对贝类养殖和海湾生态系统内的物质和营养盐循环等多个方面产生影响。本研究以北方重要的养殖海湾----桑沟湾为研究对象，对贝藻养殖区附着生物的群落演替及其生态效应进行了研究。主要研究结果如下： ① 2007年5月至2008年5月，采用挂网的方法对桑沟湾栉孔扇贝和海带混养区的附着生物的季节变化进行了研究。结果显示挂网上的附着生物具有显著的季节变化特征，网片上的附着生物湿重与水温的变化相一致，生物量为3~1210 g•m-2。2月份附着生物的生物量最低，8月份最高。2007年9月至11月，对栉孔扇贝养殖笼上和贝壳上的附着生物种类和数量进行了研究。结果显示9月份养殖笼上附着生物的湿重约为1.94 kg，10月份降至0.99 kg，11月份又稍有增加，为1.03 kg。扇贝壳上的附着生物变化趋势与养殖笼上的相同，9~11月份壳上附着生物的数量约0.49~2.09 g。扇贝养殖笼上可鉴定的大型附着生物约23种，包括藻类、海鞘类、苔藓虫类、环节动物、腔肠动物、软体动物、甲壳动物和海绵动物等。玻璃海鞘、柄海鞘、紫贻贝和苔藓虫等是附着生物群落中的优势种。 ② 通过在栉孔扇贝和虾夷扇贝上壳上添加不同重量的“模拟附着生物”（速凝水泥）的方法，研究了贝壳上附着生物的重量对这两种扇贝生长和存活的影响。结果显示水泥重量是上壳重0.5-3倍的各组实验组扇贝的生长和存活与对照组（未添加水泥的扇贝）之间没有显著差异。说明贝壳上附着生物重量为上壳的3倍重时，也不会显著影响扇贝生长存活。9-11月份贝壳上的自然附着生物的重量约为1.47-2.09 g，为上壳重的28.16 (±38.6)%—31.29 ± (31.63)%。因此，贝壳上附着的生物重量不太可能对扇贝的生长存活造成显著的负面影响。 ③ 在桑沟湾现场测定了玻璃海鞘和柄海鞘的生物沉积速率。9月份（水温约24℃）玻璃海鞘和柄海鞘的生物沉积速率分别为32.14和90.06 mg•ind-1•d-1或（858.99 和467.76 mg•gdw-1•d-1），据此计算，养殖笼上的两种海鞘的生物沉积速率约为84.29 mg•m-2•d-1。海区的自然沉积速率为41.49 mg•m-2•d-1；玻璃海鞘和柄海鞘沉积物中有机质含量分别为14.34%和13.77%，对照组海区自然的有机质含量为14.36%；以上三者有机碳的含量分别为24.72%，23.74%和24.76%；氮的含量分别为0.27%和0.25%，自然沉积物中的氮含量为0.30%。9月份扇贝养殖笼上附着的海鞘将产生2588.16吨的沉积物，即向底部沉积363.77吨的有机物、6.99吨的氮和1.79吨的磷。 ④ 通过测定扇贝养殖笼上优势种附着生物--玻璃海鞘、柄海鞘和贻贝的摄食、呼吸和排泄，研究了这些优势种类对贝类养殖和海湾环境的影响。9月份（水温约24.5℃）玻璃海鞘和柄海鞘对颗粒有机物（POM）的摄食率分别为14.30 和17.01 mg• h-1•ind-1。根据实验结果计算这两种海鞘摄取的颗粒有机物相当于312个扇贝的摄取量，大于笼内养殖的扇贝的摄取量；玻璃海鞘和柄海鞘的耗氧率分别约为0.32和0.18 mg•h-1•ind-1，养殖笼上的这两种海鞘消耗的溶解氧约等于75个扇贝消耗的溶解氧。栉孔扇贝、玻璃海鞘、柄海鞘和贻贝的排氨率分别为33.66 ±11.34，117.90±23.46，35.91±6.22，28.08±3.41 ug NH4-N•gdw-1•h-1。以此估算，9月份玻璃海鞘、柄海鞘和贻贝每天排泄的氨氮约为654.08 kg，相当于16467吨栉孔扇贝（鲜重）排泄的氨氮。海鞘和贻贝排泄的氨氮可提供浮游植物等所需的2.75%的氮，可以提供1204吨海带的生长所需的氮。 ⑤ 一个养殖笼内的栉孔扇贝和全部附着生物（Scallop Culture Unit, SCU）在夏季（6-9月）对颗粒有机物的摄食速率约为43.13-98.94 mg/h，平均74.05 mg/h，期间桑沟湾养殖的栉孔扇贝及附着生物摄取的POM约为1279.58吨；同期，SCU对氨氮和磷（PO4-P）的排泄速率分别为125.59-1432.23 μmol•h-1和76.2-252.89μmol•h-1，期间桑沟湾养殖扇贝及附着生物排泄的氮磷分别为211.09 吨和83.79 吨。一串牡蛎及吊绳和牡蛎壳上的附着生物（Oyster Culture Unit, OCU），夏季摄食率为5-41.43μmol•h-1，耗氧率为16.54-41.76μmol•h-1，对氨氮和磷（PO4-P）的排泄速率分别为35.56-489.34μmol•h-1 和9.92-16.68μmol•h-1。以此估算，夏季OCU可摄取POM535.68吨，消耗溶解氧955.58吨，排泄氮磷分别为62.37 吨和15.50 吨。

Integrated cultivation of the red alga Kappaphycus alvarezii and the pearl oyster Pinctada martensi

The effect of simultaneously cultivating the pearl oyster Pinctada martensi and the red alga Kappaphycus alvarezii on growth rates of both species was investigated in laboratory and field studies conducted from December 1993 to June 1995. The two study sites were in subtidal areas 100 km apart off the east coast of Hainan Island, China. Pearl oysters were cultivated in the center of an algal farm and red alga was cultivated in the center of the pearl oyster farm. These field experiments showed higher growth rates of both P. martensi and K. alvarezii in a co-culture system than in a monospecies culture system. Laboratory studies showed that the algae removed nitrogenous wastes released by pearl oysters. Algae treated with pearl oyster wastes grew much faster than those without oyster wastes. Algae treated with the seawater to which NH4Cl, NaNO3 and NaNO2 were added grew at the same rate as those treated with natural seawater containing oyster nitrogenous wastes, suggesting that enhanced growth of algae in the co-culture system was largely due to nitrogenous metabolites of the pearl oysters. In the co-culture, growth of pearl oysters was positively influenced by the presence of rapidly growing algae but when seawater temperature decreased below 20 degrees C, the algae grew slowly and there was no measurable benefit of mixed culture to either algae or pearl oyster.

Seasonal variation in metabolism of cultured Pacific oyster, Crassostrea gigas, in Sanggou Bay, China

Rates of respiration and excretion of the Pacific oyster, Crassostrea gigas, were measured seasonally from June 2002 to July 2003 under ambient conditions of food, water temperature, pH, and salinity in Sanggou Bay, an important mariculture coast in north China. The aim of this study is to obtain fundamental data for further establishing an energy budget model and assessing the carrying capacity for cultivation of C. gigas in north China. Oysters were collected monthly or bimonthly from the integrated culture areas of bivalve and kelp in the bay. Oxygen consumption and ammonium and phosphorus excretion rates were measured, and ratios of O/N and NIP were calculated. One-way ANOVA was applied to determine differences among these parameters that act as a function of seasonal variation. All the physiological parameters yielded highly significant variations with season (P<0.01) The rate of respiration varied seasonally, with the highest oxygen consumption rate in July and the lowest rate in January, ranging from 0.07 to 2.13 mg O-2 h(-1) g(-1) dry tissue weight (DW). Maximum and minimum ammonium excretion rates were recorded in August and January, respectively, ranging from 0.51 to 5.40 mu mol NH4-N h(-1) g(-1) DW. Rates of phosphorus excretion varied from 0.11 (in January) to 0.64 (in July) mu mol PO4-P h(-1) g(-1) DW. The O/N and N/P ratios changed from 9.2 (in January) to 59.8 (in July) and from 4.6 (in January) to 10.9 (in August), respectively. For each season, the allometric relationship between the physiological response (e.g., rate of oxygen consumption, ammonium and phosphorus excretion) and DW of the animal was estimated using the formula: Y=a x DWb. (C) 2005 Elsevier B.V. All rights reserved.

A Novel Counter Sheet-Flow Sandwich Cell Culture Device For Mammalian Cell Growth In Space

Cell culture and growth in space is crucial to understand the cellular responses under microgravity. The effects of microgravity were coupled with such environment restrictions as medium perfusion, in which the underlying mechanism has been poorly understood. In the present work, a customer-made counter sheet-flow sandwich cell culture device was developed upon a biomechanical concept from fish gill breathing. The sandwich culture unit consists of two side chambers where the medium flow is counter-directional, a central chamber where the cells are cultured, and two porous polycarbonate membranes between side and central chambers. Flow dynamics analysis revealed the symmetrical velocity profile and uniform low shear rate distribution of flowing medium inside the central culture chamber, which promotes sufficient mass transport and nutrient supply for mammalian cell growth. An on-orbit experiment performed on a recovery satellite was used to validate the availability of the device.

A Trabecular Bone Explant Model of Osteocyte–Osteoblast Co-Culture for Bone Mechanobiology

The osteocyte network is recognized as the major mechanical sensor in the bone remodeling process, and osteocyte-osteoblast communication acts as an important mediator in the coordination of bone formation and turnover. In this study, we developed a novel 3D trabecular bone explant co-culture model that allows live osteocytes situated in their native extracellular matrix environment to be interconnected with seeded osteoblasts on the bone surface. Using a low-level medium perfusion system, the viability of in situ osteocytes in bone explants was maintained for up to 4 weeks, and functional gap junction intercellular communication (GJIC) was successfully established between osteocytes and seeded primary osteoblasts. Using this novel co-culture model, the effects of dynamic deformational loading, GJIC, and prostaglandin E-2 (PGE(2)) release on functional bone adaptation were further investigated. The results showed that dynamical deformational loading can significantly increase the PGE(2) release by bone cells, bone formation, and the apparent elastic modulus of bone explants. However, the inhibition of gap junctions or the PGE(2) pathway dramatically attenuated the effects of mechanical loading. This 3D trabecular bone explant co-culture model has great potential to fill in the critical gap in knowledge regarding the role of osteocytes as a mechano-sensor and how osteocytes transmit signals to regulate osteoblasts function and skeletal integrity as reflected in its mechanical properties.