Relationship between cooling rates,cryoprotectant concentrations and salinities in the cryopreservation of marine microalgae

The viability of the marine microalgae Rhodomonas baltica Karsten, Isochrysis affinis galbana (Strain T-ISO) Parke, Chaetoceros gracilis Schütt, Tetraselmis chuii Butcher, Nannochloropsis gaditana Lubian and Nannochloris atomus Butcher, cryopreservec employing different cooling rates, either with or without the addition of the cryoprotective compounds dimethyl sulfoxide (DMSO) and methanol was studied at two exposure salinities. A viability index, which considered both cell recovery and the growth capacity of microalgae after thawing, was developed. The growth of thawed algae was compared to that obtained for unfrozen algae grown in liquid medium under the same conditions. Viability (V) was calculated according to the equation: V=(C ₀/C _i)x(C ₇/(a·C ₀ ^b ))x100, where C ₀ and C ₇ are, respectively, the initial and final cell densities measured in the cultures after thawing from-196°C, C _i is the maximum initial cell density (complete cell recovery), and a, b are the regression coefficients obtained for C ₇ as a function of C ₀ in the unfrozen controls. R. baltica was the only species that showed an improved viability when salinity was reduced from 36 (average viability 13.7% for 15% DMSO) to 20 (average viability 36.2% for 15% DMSO). The other five species displayed better viability only at the higher salinity at all tested cooling rates and cryoprotectant levels. T. chuii, Nannochloropsis gaditana, and Nannochloris atomus Butcher could be cryopreserved without cryoprotectant. However, their respective viabilities (32.7, 30.8 and 65.8%) at 36 S were progressively improved on addition of 5% DMSO (70.9, 48.2 and 93.5, respectively) and 15% DMSO (91.9, 57.0 and 94.2%, respectively). Similar improvements were found for Nannochloropsis gaditana and Nannochloris atomus when cryopreserved using methanol concentrations of 1% (average viabilities of 46.9 and 91.8, respectively) and 5% (average viablities of 48.7 and 95.3, respectively). Methanol was completely ineffective in cryopreserving the other four species and caused a lethal effect on T. chuii during freezing. C. gracilis could be cryopreserved with 5% DMSO only at 36 S. This resulted in a similar viability (11.7%) to that obtained using 15% DMSO in 20 S (13.7%). Keeping cryoprotectant concentration at 15% DMSO and raising salinity to 36 significantly improved the mean viability of C. gracilis to 21.6%. A low mean viability of 2.1% was obtained for I. galbana when 15% DMSO was used in full-strength seawater (36 S). Within the range of cooling rates tested (0.25 to 16 C° min^-1), cryopreserved microalgae showed higher viabilities at faster rates in the absence of cryoprotectants at both salinities. Generally, the dependence on cooling rate decreased proportionally to the concentration of DMSO or methanol, as demonstrated by the lack of significance for the slope of the regressions. Only C. gracilis appeared to depend on faster cooling rates in the presence of 15% DMSO.     

Effect of freezing on photosynthesis of intertidal macroalgae: relative tolerance of Chondrus crispus and Mastocarpus stellatus (Rhodophyta)

The effect of freezing on photosynthetic metabolism was studied in the red algae, Chondrus crispus and Mastocarpus stellatus. Plants of both species were collected from the intertidal at Chamberlain or Kresge Point, Maine, USA (43°56N, 69°54W) between February and March 1987. Photosynthetic rates were measured immediately after freezing at-20°C and following recovery periods in seawater. Photosynthesis in C. crispus declined rapidly following freezing, falling to 70% of control values within 1 h and 30% after 3 h exposure. Minimum photosynthetic rates (7 to 9% of controls) occurred following freezing exposures of 12 h or more. Full photosynthetic recovery in C. crispus after 3 h at-20°C required 48 h. Photosynthesis in C. crispus did not fully recover in plants frozen for 6 h or more. In contrast, photosynthesis in M. stellatus was relatively unaffected by freezing exposures of <12 h. Twelve hours or more at-20°C reduced photosynthesis to 55% of controls. Photosynthesis in M. stellatus fully recovered from 24 h at-20°C within 24 h. In both species the reduction of photosynthesis by freezing was associated with damage to the plasma membrane and reduced efficiency of energy transfer from phycobilisomes to chlorophyll a, but did not appear to involve ribulose-1,5-bisphosphate carboxylase oxygenase activity. The freezing tolerance of C. crispus and M. stellatus positively correlates with their respective intertidal distributions, suggesting that freezing may be involved in controlling the distributions of these species on the shore.     

冻融作用下盐碱水田土壤含水率和氮素对有机碳影响研究

选择吉林西部前郭县盐碱水田土壤,进行实验室模拟冻融实验：以-5℃冻结1 d、5℃消融1 d作为1次冻融循环,揭示不同含水率和含氮量处理条件下土壤有机碳（SOC）的变化规律。结果表明,土壤含水率和含氮量是影响SOC含量的2个重要因素,冻融次数、土壤含水率、土壤含氮量以及冻融次数和土壤含水率、冻融次数和土壤含氮量的交互作用对盐碱水田SOC含量的影响显著（P〈0.05）。在1~3次冻融循环过程中,SOC含量明显降低,随着循环次数的增加,SOC含量降低速度减缓;适量的氮素和较低的含水率有利于SOC的稳定,初始含水率为50%的SOC含量明显低于含水率30%和40%的土壤,加入20%硝酸铵的SOC含量明显低于对照组和加入10%硝酸铵的土壤。研究结果对深入研究季节冻土区冻融期盐碱水田SOC变化规律,评估全年候SOC储量有重要意义。     

厌氧条件下剩余污泥中磷及相关指标的释放和变化规律

污水处理过程中产生的剩余污泥富含大量的氮磷元素,从剩余污泥中回收磷是解决磷资源日益缺乏的一种有效途径。探寻出剩余污泥中磷的释放规律是实现剩余污泥中磷回收的首要前提。因此,以实际污水处理厂污泥为研究对象,建立污泥停留时间为5d的中试模型系统。通过系统分析5d停留时间的厌氧条件下污泥中污泥浓度、上清液总磷和氨氮浓度的变化情况,为后续的污泥磷回收提供支撑条件。研究结果表明,在中试系统污泥停留时间5d的厌氧条件下,剩余污泥微生物衰亡自溶或被分解,胞内物质释放,从而使固态物质转化为液态,污泥中磷及相关的氮等物质得到了较大的释放,污泥上清液总磷和氨氮质量浓度可分别达到100和40 mg·L^-1以上。所释放出的氮磷浓度足以满足鸟粪石回收氮磷方法所需的最低经济性要求,为污泥进行厌氧消化后采用鸟粪石的方法回收释放的氮磷提供了重要的基础依据。研究中还发现5d停留时间下, SS和VSS都有不同程度的降低,二者分别减少8.34%和10.14%以上,其中VSS的减少量占SS减少量的65%左右。同时,进入厌氧反应系统的初始污泥浓度对于氮磷的释放有着较大的影响,反应系统的SS在6300~7200 mg·L^-1的条件下,磷和氮的单位质量污泥释放量达到最佳,分别达到单位干污泥0.015和0.006 mg·mg^-1。研究结果为剩余污泥中回收氮磷提供了重要的依据。     

粤北天井山国家森林公园三种林木在2008年特大冰雪灾害后的恢复

自2008年5月至2009年8月（共480 d）,对遭受2008年特大冰雪灾害的广东省北部天井山国家森林公园中受灾点（海拔700 m）和未受灾点（海拔550 m）的3种植物：樟树（Cinnamomum camphora）、荷木（Schima superba）和罗浮栲（CastanopsisFagaceae）进行对比实验。选择生理指标为：光系统II最大光化学量子效率（Fv/Fm）、比叶面积（SLA）、叶干物质重（LDMC）、单位叶面积氮含量（Na）、单位叶面积多酚含量（Phena）。研究结果显示：3受灾种Fv/Fm均无下降;受灾罗浮栲、荷木的其他各指标在300 d后已恢复至正常水平,而受灾樟树的各生理指标在300 d后仍显著低于正常（p〈0.1）;受灾樟树的生长模式由快速生长型改变为积累营养型。研究表明：（1）雪灾损伤对光系统II没有累积效果;（2）雪灾造成的冠层改变对中下林层的营养物质分配有影响;（3）作为人工栽培种的樟树,较自然生长种需要更长的灾后恢复期。     

Hydrocarbon uptake and loss by the mussel Mytilus edulis

The dynamics of accumulation and elimination of hydrocarbons by the blue mussel Mytilus edulis were studied in a continuous-flow system. Mussels were exposed for as long as 41 days to 200 – 400 g/l of diesel fuel adsorbed on kaolin particles. Hydrocarbons were accumulated in the tissues in excess of 1000 times the exposure levels. Upon termination of dosing, the mussels exhibited a rather rapid loss of hydrocarbons for the first 15 to 20 days (biological half-life=2.7 to 3.5 days). Subsequently, however, elimination was reduced to a minimum and a considerable fraction of the hydrocarbons could be recovered from the tissues after as long as 32 days of depuration. The mussels exhibited definite signs of physiological stress due to chronic exposure to diesel fuel, although recovery was rapid upon termination of dosing. It is concluded that mussels could be utilized as a test organism for monitoring long-term hydrocarbon pollution in marine waters. The implications for the mussel culture industry are discussed.     

Respiration and excretion by the ctenophore Mnepiopsis leidyi

Respiration (dissolved oxygen and carbon dioxide) and excretion (dissolved organic carbon, inorganic and organic nitrogen and phosphorus) rates were measured for a variety of sizes of Mnemiopsis leidyi over a temperature range of 10.3° to 24.5°C. Both respiration and excretion rates were a direct linear function of animal weight and very temperature sensitive (Q₁₀4). Oxygen uptake ranged from 155 to 489 g at O/(g dry weight) day^-1 and carbon dioxide release from 43 to 166 M. Organic carbon made up about 38% of the total carbon released. Inorganic nitrogen excretion, exclusively in the form of ammonium, comprised 54% of the total nitrogen release and ranged from 10 to 36 M NH₄/(g dry weight) day^-1. Average release of dissolved primary amines (expressed as glycine equivalents) equaled 43% of the organic nitrogen fraction. Inorganic phosphorus release ranged from 2.0 to 4.9 M/(g dry weight) day^-1 and made up about 72% of the total phosphorus loss. The turnover of elements in the body was calculated as 5 to 19% per day for carbon and nitrogen, depending on the temperature, and an even higher 20 to 48% per day for phosphorus. These values are comparable to rates observed for small, active zooplankton.     

Duckweed Landoltia punctata purifies micro-polluted surface water and produces starch北大核心CSCD

Aquatic plant duckweed has remarkable potential in nutritional water purification and starch accumulation; at present, it has received increasing attention. This study aimed to investigate the ability of duckweed in nutrient recovery from micro-polluted surface water; further, the starch accumulation capacity of duckweed was evaluated. The results showed that duckweed can achieve better depth treatment of the micro-polluted surface water, within 1-day treatment, by duckweed. Ammonia nitrogen and total phosphorus status of Class V and worse than class V water was improved to a superior level; moreover, the nitrogen and phosphorus removal rates were 98.5% and 82.9%, respectively. In addition, duckweed can rapidly accumulate starch during water treatment. The starch content of duckweed was 28.38% and 21.57% (dry weight) in Class V and worse than class V wastewater after 3 days of treatment, respectively, and reached 52.15% and 49.58% on day 15. Moreover, additional carbon dioxide (CO2) supplementation promoted the starch production. The starch content increased by 55.7% compared with that of control, and the average starch accumulation rate increased by 2.72 times in 3 days. Therefore, duckweed can not only rapidly purify micro-polluted water, but also accumulate a large amount of starch. This study forms the basis for wastewater treatment and post-treatment utilization of duckweed biomass. © 2018 Science Press. All rights reserved.     

Effects of sublethal concentrations of mercuric chloride on ammonium-limitedSkeletonema costatum

The effect of sublethal additions of mercuric chloride on the marine diatomSkeletonema costatum (Grev.) Cleve grown in NH₄-limited chemostats and batch cultures was assessed. In short-term Hg exposure experiments (up to 5 h), the effect of Hg on ammonium uptake rates was studied by simulatneously perturbing the culture with 5 M NH₄ Cl and Hg concentrations ranging from 0.04 to 5.52 nM HgCl₂. The threshold of Hg toxicity occurred between 1.8 and 3.7 nM, based on a decrease in ammonium uptake rates. When the NH₄-limited culture was starved of ammonium for 30 h, the threshold of Hg toxicity decreased about an order of magnitude to 0.2 nM. In long-term Hg exposure experiments (679.5 h), NH₄-limited continuous cultures were semi-continuously exposed to 0.37 and 3.68 nM HgCl₂. After 4 days, the cell density in the Hg-treated chemostats began to drastically decline. After about 16 days these populations recovered, even though Hg additions continued. At the end of the experiment (26 days), cell densities had reached the levels observed at the beginning of the experiment. The reason for the recovery is unknown, but several possibilities are discussed. Ammonium uptake rates determined during the time-course of this long-term Hg exposure, indicated that these NH₄-limited cultures exhibited a significant loss in their ability to take up ammonium at low concentrations (e.g. 1 M). Thus, mercury pollution may seriously decrease the ability of a species to utilize the limiting nutrient during periods of seasonal nutrient limitation.     

Freezing tolerance in the intertidal red algaeChondrus crispus andMastocarpus stellatus: Relative importance of acclimation and adaptation

The effect of repeated daily freezing on photosynthesis, growth and phenotypic acclimation to freezing was studied in the red algaeChondrus crispus Stackhouse andMastocarpus stellatus (Stackhouse in With.) Guiry. Algae used for experiments were collected from Chamberlain, Maine, between March and August 1987, and field observations and experiments were carried out at Chamberlain and Kresge Point, Maine between March 1987 and March 1989. After ca 30 d of daily freezing for 3 h at –5°C photosynthesis ofC. crispus was reduced to 55% of control values. Growth rates ofC. crispus were also reduced in fronds frozen daily compared to unfrozen controls, and eventually fronds became bleached and fragmented resulting in biomass losses. Fronds ofC. crispus, frozen daily, had higher photosynthetic rates following freezing events than unfrozen controls indicating that this species can acclimate to freezing conditions. Acclimation to freezing involves the light-harvesting reactions of photosynthesis. In contrast, photosynthesis and growth inM. stellatus were unaffected by repeated daily freezing for 3 h at –5°C for 36 d. No differences in photosynthesis following freezing were observed between frozen and control fronds suggesting thatM. stellatus does not phenotypically acclimate to freezing. The greater freezing tolerance ofM. stellatus relative toC. crispus results, in part, from genetic adaptations associated with plasma membranes and the light-harvesting reactions of photosynthesis.     

Nitrogen turnover in the leaf litter and fine roots of sugar maple

In order to better understand the nitrogen (N) cycle, a pulse of 15NO3- was applied in 1998 to a sugar maple (Acer saccharum) dominated northern hardwood forest receiving long-term (1994-2008) simulated atmospheric N deposition. Sugar maple leaf litter and live fine-root 15N were quantified for four years prior to labeling and for 11 subsequent years. Continuous sampling of 15N following addition of the tracer enabled calculation of leaf litter and fine-root N pool turnover utilizing an exponential decay function. Fine-root 15N recovery peaked at 3.7% +/- 1.7% the year the tracer was applied, while leaf litter 15N recovery peaked in the two years following tracer application at approximately 8%. These results suggest shoots are primarily constructed from N taken up in previous years, while fine roots are constructed from new N. The residence time of N was 6.5 years in leaf litter and 3.1 years in fine roots. The longer residence time and higher recovery rate are evidence that leaves were a stronger sink for labeled N than fine roots, but the relatively short residence time of tracer N in both pools suggests that there is not tight intra-ecosystem cycling of N in this mature forest.     

Nitrogen regeneration by the surf zone penaeid prawn Macropetasma africanus

Nitrogen excretion of individual Macropetasma africanus (Balss) from an exposed beach/surf zone in Algoa Bay, South Africa was monitored under laboratory and field conditions in relation to body mass, temperature and feeding during 1985. Excretion rate experiments were performed on starved prawns at 15°, 18°, 20° and 25°C, as well as on individuals fed on four different diets (mussel, fish, shrimp and natural diet) at 15° and 20°C. The ratios of the excreted compounds to total nitrogen excreted were similar for the four diets despite differences in their nitrogen content and in the amount of food consumed. At 15° and 20°C, ammonia excretion rates of fed individuals were four to seven times higher than in starved prawns. the excretion rates were not correlated with nitrogen content of diets. M. africanus recycles 1 557 g NH₄–N per metre strip per year or 1 832 g total nitrogen m^-1 yr^-1, which constitute 12 and 14%, respectively, of total phytoplankton requirements of the surf zone. This study indicates that large motile crustaceans, when abundant, can play an important role in nutrient recycling in turbulent marine environments.     

厌氧污泥释放磷的规律及鸟粪石法回收磷的应用研究

城市污水处理厂进行脱氮除磷工艺时,大量的磷从水体转入活性污泥中,如不能回收这部分磷,将造成磷的大量流失,这与磷矿稀缺的现状形成矛盾。通过建立污泥停留时间5 d和10 d的两个厌氧反应系统,对污泥中磷的释放规律进行研究,并采用鸟粪石法对上清液中的磷进行回收。研究结果表明,厌氧污泥上清液中的磷含量高达150 mg.L-1,SRT为5 d和10 d的系统,分别在4 d和2 d后磷的质量浓度由14 mg.L-1上升到100 mg.L-1,且基本上都以正磷酸盐的形式存在。将pH从8.3上升到9.0,磷的回收率可以从60%提升到90%,当pH达到8.8时,磷的回收率即可超过80%,表现出了较好的磷回收效果。研究还发现镁离子和磷酸根的摩尔比对磷的回收率的影响较小,在pH=8.8时,将镁磷比从1.43提升到1.83,磷的回收率仅从79.2%提升到85.5%;在pH=9.0时提高镁磷比对磷的回收基本没有影响。     

Post-settlement energy reserves in <Emphasis Type="Italic">Panulirus cygnus</Emphasis>: experimental effects of starvation on survival and nutritional condition

Post-settlement survival success in rock (spiny) lobsters is likely to be influenced by the nutritional condition of the non-feeding pueruli at settlement. Consequently, we predict that survival shortly after settlement depends on food resources being replenished rapidly. In the present study the length of the starvation period on survival in post-puerulus juveniles of the western rock lobster Panulirus cygnus was investigated using laboratory experiments. All experimental pueruli were collected from Seven Mile Beach, Western Australia, using sandwich puerulus collectors. Total lipid, lipid class, fatty acid, total protein and total glycogen analyses were conducted on fed and starved post-puerulus juvenile lobsters, from moult into the first juvenile stage to 30 days post-moult. From a total of 165 samples used in this study, 15 post-puerulus juveniles were sampled initially and five post-puerulus juveniles sampled every 5 days thereafter for biochemical analysis. Post-puerulus juveniles survived up to 34 days of starvation. The maximal starvation time for post-puerulus juveniles from which recovery was observed is estimated to be in excess of 22 days. Lipids, in particular phospholipids, are shown to be the most important source of energy catabolised during the starvation period, with greater than 62% reduction in total lipid at day 30. Proteins were also catabolised during starvation, but to a much lesser extent than lipid, decreasing by 34% in total content at day 25. Carbohydrates were present always as a minor constituent, however their content did not change significantly during starvation. Our results suggest that the pueruli collected in December 2004 were generally in sufficiently good condition to survive further starvation after settlement; nutritional levels of the post-puerulus juveniles were enhanced compared to those observed in previous studies. We suggest that the high levels of energy reserves in rock lobster post-pueruli may provide an adaptive advantage to aid the transition from pelagic to benthic living by minimising stress and the consequences of failing to locate immediately suitable food resources.     

亚热带土壤氮素反硝化气态产物研究

亚热带可变电荷土壤化学性质与温带地区恒电荷土壤有诸多不同特点,使得反硝化具有一些与温带土壤不同的特性,进一步深入研究亚热带土壤反硝化气体产物的组成比例、主要影响因素和机理,将有助于加深对亚热带环境条件下土壤N循环的理解和认识,以及为正确评价亚热带土壤反硝化环境效应提高科学依据。因此,就亚热带土壤厌氧培养条件下反硝化的气态产物问题进行了探讨。土样采自江西典型亚热带红壤地区,在加入K15NO3（10 atom%15N,加入N量为200 mg·kg-1）条件下进行了7 d 30℃、密闭、淹水、充N2的严格厌氧培养试验。试验结果表明：随培养时间推移,15N回收率逐渐下降,土壤总残留的15NO3-质量分数和回收率之间存在显著正相关关系（p〈0.001）,表明反硝化作用越弱的土样回收率越高。总气态氮损失率的估计值和实测值都随培养时间延长呈上升趋势,两者之间存在显著正相关性（p〈0.001）。根据稳定性同位素15N示踪试验结果初步估计,厌氧培养7 d内反硝化作用产生的气态产物中N2O占总气态氮损失的17.1%,N2占8.7%,估计NO可能是主要的反硝化产物之一。以未能回收的氮计算,NO约占总气态氮损失的67.5%~78.6%,平均为74.1%。反硝化气态产物中NO和N2O总量占总气态氮损失的91.3%。NO、N2O和N2分别占总施入氮量的18.6%、4.4%、2.0%。因此,亚热带土壤氮素反硝化过程中主要气态产物可能为NO和N2O,而非对环境无害的N2。     

Toxicity evaluation of a complex metal mixture to the softshell clam Mya arenaria

Adults of the softshell clam Mya arenaria were continuously subjected to a flowing raw seawater solution containing a mixture of salts of manganese, zinc, lead, nickel, copper, and cadmium. Final calculated concentrations, in g l^-1, of the toxicant solution were 7200 Mn, 2500 Zn, 70 Pb, 50 Ni, 50 Cu and 1 Cd; these concentrations approximated highest measured levels within surficial interstitial sediment waters from mid-Narragansett Bay, Rhode Island. M. arenaria were also subjected to a 20% solution, i.e., 1440 Mn, 500 Zn, 14 Pb, 10 Ni, 10 Cu, and 0.2 g l^-1 Cd. One study was conducted for 112 days in winter at 0° to 10°C and another for 16 days in summer at 16° to 22°C. In the winter study, all clams exposed to a 100% solution died between the 4th and 10th week; soft parts of survivors at 6 weeks contained about 19 times more Pb, 15 x more Zn, 12 x more Cu, 10 x more Mn, 3 x more Ni and 0.1 x more Cd than controls; relatively minor changes in whole body elemental content of Ca, Cr, Fe, K, Mg, Na, Sr, and V were observed. Clams exposed to a 20% solution during winter survived the 112 day study; at that time these contained about 5 x more Cu, 4 x more Mn, 3 x more Zn and about 2 x more Pb than controls; comparatively minor changes were observed in other elements examined. In the summer study, all M. arenaria subjected to the 100% solution died between 6 and 14 days; survivors from this group at 7 days contained about 25 x more Pb, 13 x more Cu, 11 x more Zn, 7 x more Mn, and 3 x more Ni than controls; other changes in elemental content were not as pronounced. Mortality in the 20% group during summer was slightly higher than controls during the 16 day study; at 14 days survivors from this group contained about 12 x more Mn, 7 x more Pb, 7 x more Zn, 4 x more Cu, and 3 x more Ni than controls. Survival and bioaccumulation patterns were not altered through feeding a supplemental diet of algae. The significance of these findings are discussed in terms of potential environmental perturbations, especially local dredging practices.     

The effects of feeding or addition of dissolved inorganic nutrients in maintaining the symbiosis between dinoflagellates and a tropical marine cnidarian

The availability of solid food (Artemia nauplii) and dissolved inorganic nutrients (ammonium, nitrate, phosphate) to the shallow-water marine hydroid Myrionema amboinense was manipulated for 1-8 days in order to investigate their role in the growth of intracellular symbiotic dinoflagellates (zooxanthellae) of the genus Symbiodinium. Symbionts from hydroids collected from the field or maintained under laboratory conditions (25°C, 12 h:12 h light:dark cycle, 80 µE m^-2 s^-1 fluorescent lighting) always exhibited a single peak in mitotic index (MI) at dawn. Symbionts in freshly collected field animals had an MI peak of about 15%. Symbiotic dinoflagellates in hydroids fed Artemia nauplii twice daily in the laboratory maintained this dawn peak of MI between 10% and 15%, but in the absence of feeding or added inorganic nutrients, this peak declined to less than 1% within 2-4 days. In contrast, when hydroids were placed in solutions containing ammonium (20 µM NH₄Cl), nitrate (10 µM NaNO₃), and a combination of ammonium and phosphate (2 µM Na₂HPO₄) immediately after collection, the algal MI remained between 5% and 15% for 4-7 days; the addition of 2 µM phosphate did not increase MI relative to unfed rates. When unfed animals were placed in dissolved nitrogen or fed Artemia, the symbiont MI increased from <1% to 10-17% within 2-3 days; P alone had no effect. However, the increase resulting from added inorganic nutrients was temporary, lasting only 5-7 days. These observations suggest that algal division in the host is maintained indefinitely in the field or by feeding particulate foods twice daily in the laboratory, but the addition of inorganic nutrients alone (ammonium, nitrate and ammonium/phosphate) appeared to support the completion of a maximum of one additional round of cell division. Nutrients required for continued growth and division of symbiotic dinoflagellates are linked to host feeding and host growth; without external food, neither host nor symbiont continue to grow. The same phenomenon is seen in zooxanthellate anemones, clams and corals, where total numbers of symbionts appear to be linked to changes in host-tissue biomass (protein), achieving relatively stable densities in M. amboinense, corals and other cnidarian symbioses, depending on their local environmental conditions. The results of the present study help explain the cellular responses of algal symbionts in reef-dwelling invertebrates to additions of dissolved inorganic nutrients to coral-reef ecosystems.     

Evaluation and sensitivity of cyanobacteria,Nostoc muscorum and Synechococcus PCC 7942 for heavy metals stress – a step toward biosensor

This study attempted to determine the effects of heavy metals on the photosynthetic blue-green algae for their potential to use as a biosensor. The bioaccumulation of metals and its effects on pigments of Nostoc muscorum and Synechococcus PCC 7942 were assessed. The culture was grown in BG 11 liquid medium supplied with different metals like mercury (Hg), lead (Pb), and cadmium (Cd) and incubated (µM 20 concentrations) for 10 days under optimal conditions. The accumulated amounts of metals were determined by atomic absorption spectroscopy (AAS). The stress effects on photosynthetic pigment chlorophyll a (Chl a) were monitored by laser-induced fluorescence (LIF). Bio-concentration factor (BCF) reached a peak in cells on the 2nd day of incubation followed by a gradual reduction. The highest reduction in the pigment concentrations (Chl a and β carotene) was observed at 20?µM?L^?1 Hg treatment. The results indicate that, cyanobacteria may serve as both potential species to be used as a biosensor and used to clean up heavy metals from contaminated water. These changes were analyzed with the long-term goal of exploiting cyanobacterial cells as biosensors.     

Nitrogen and phosphorus cycling in shrimp ponds and the measures for sustainable management

Six ponds of age 3 were selected 45 km north from Suzhou in the Tailake region, and research conducted on nitrogen and phosphorus cycling in P. vannanmei (Penaeus vannanme) ponds and M. nipponense (Macrobrachium nipponense) hatchery ponds under normal management. Two treatments each had three replications. The results confirmed that feed was the major path of nitrogen and phosphorus input, each accounted for 61.24% (193.81 kg ha(-1)) and 81.08% (45.20 kg ha(-1)) of the total nitrogen and phosphorus input for P. vannanme ponds; the values for M. nipponense ponds were 43.93% (86.31 kg ha(-1)) and 57.67% (14.61 kg ha(-1)), respectively. Water pumped into ponds contributed on average 83.57 kg ha(-1) nitrogen and 8.48 kg ha(-1) phosphorus for P. vannanmei ponds, and 87.48 kg ha(-1) nitrogen and 7.00 kg ha(-1) phosphorus for M. nipponense hatchery ponds. Shrimp harvest recovered 102.81 kg ha(-1) nitrogen (32.94% of the total nitrogen input) and 7.94 kg ha(-1) phosphorus (14.23% of the total phosphorus input) for P. vannanme ponds; and 43.94 kg ha(-1) nitrogen and 4.46 kg ha(-1) phosphorus for M. nipponense hatchery ponds. The sum of nitrogen losses through volatilization, denitrification and sedimentation was 173.62 and 122.39 kg ha(-1), 54.86% and 62.29% of the total nitrogen input for P. vannanme ponds and M. nipponense hatchery ponds, respectively. Sediment accumulated 41.46 and 14.63 kg ha(-1) phosphorus, 74.37% and 64.85% of the total phosphorus input for P. vannanm ponds and M. nipponense hatchery ponds. Draining and seeping caused 40.06 kg ha(-1) nitrogen (12.66% of total nitrogen input) and 6.36 kg ha(-1) phosphorus (11.40% of total phosphorus input) loss to the surrounding water from P. vannanme ponds in 114 days; 30.14 kg ha(-1) nitrogen (15.34% of the total input) and 4.45 kg ha(-1) phosphorus (17.57% of the total input) to channel water from M. nipponense hatchery ponds in 87 days, respectively. Countermeasures for sustainable pond management include improving feeds and feeding, sediment treatments, machine aerating, chemicals with no pollution, and integrated fish-shrimp cultivation. Management of water resources for pond and methods to reduce nitrogen and phosphorus loading into surrounding water from drainage are elucidated.     

Impact of anaerobically treated and untreated (raw) distillery effluent irrigation on soil microflora, growth, total chlorophyll and protein contents of Phaseolus aureus L

Impact of distillery effluent (untreated and treated) irrigation on soil microflora of the pots used for growing Phaseolus aureus L. was investigated. The growth of the P. aureus plants as affected by distillery effluent irrigation was also evaluated. The irrigation of the pots by 1-10% distillery effluent (anaerobically treated) stimulated the growth of the soil microflora (increased number of bacteria, fungi and actinomycetes) and P. aureus plants (increased shoot and root lengths, biomass, chlorophyll and protein contents). Further, 15-20% distillery effluent (anaerobically treated) had toxic effect on soil micro flora as indicated by reduced number of bacteria, fungi and actinomycetes. Reduction in shoot, root, lengths, biomass, chlorophyll, protein contents of P. aureus was also observed when irrigated by 15-20% treated distillery effluent. All the concentrations of raw distillery effluent reduced the bacterial population. However, the treated distillery effluent concentrations <10% had stimulatory effect on fungal and actinomycetes population. However, raw effluent concentrations >5% reduced the same. Raw distillery effluent was more toxic to P. aureus than treated distillery effluent as concentrations >5%, had reduced the growth (shoot, root length and biomass) of the test plant. Raw distillery effluent had adverse effect to total chlorophyll contents and all the test concentrations reduced the total chlorophyll level. However, untreated (raw) distillery effluent stimulated the protein content initially. It has been concluded from-present study that lower concentrations of the raw distillery effluent (1-5%) and treated distillery effluent (1-10%) had stimulated the growth of P. aureus and soil microflora except soil bacteria (inhibited by all the concentration of the raw effluent). However, higher concentrations (raw effluent: 10-20%; treated effluent 15-20%) had toxicity to test parameters.