COMPARATIVE STUDIES ON NITROGEN BUDGETS OF CLOSED SHRIMP POLYCULTURE SYSTEMS

April to October, 1997 comparative studies on the nitrogen budgets of closed shrimp polyculture systems showed that, in all the studied polyculture systems, nitrogen from feeds and fertilizers were the main input items, which comprised 70.7%-83.9% of the total input nitrogen, 3.2%-7.4% of which was provided by nitrogen fixation. It was in monoculture enclosures (Y 4, Y 11 and Y 12) that the percentage reached the maximum value. The output nitrogen in harvested products comprised 10.8%-24.6% of total input nitrogen, and the highest percentage, 24.6%, was found in shrimp fish tagelus polyculture systems. In shrimp monoculture and shrimp fish polyculture systems, they were 19.1% and 21.9%, respectively. The nitrogen utilization efficiency was different and varied from 12.2% to 20.1%. The highest, 20.1%, was found in shrimp fish tagelus polyculture systems, and the average of 20.0% was found in shrimp tagelus polyculture systems. The lowest, 12.2%, was found in shrimp monoculture systems. All the nitrogen utilization efficiencies in shrimp fish systems or shrimp scallop systems seemed to be higher than that of the monoculture system, but they showed little statistical difference. The main outputs of nitrogen were found in sediment mud, and comprised 48.2%-60.8% of the total input, the lowest percentage was found in shrimp fish tagelus polyculture systems, and the highest percentage in shrimp scallop systems. During the experiment, nitrogen lost through denitrification and ammonia volatilization comprised 1.9%-6.2%, averaged 2.8%, of the total input, and the loss through seepage comprised 5.9%-8.9% of the total. The estimated nitrogen attached to the enclosure wall comprised 3.7%-13.3% of the total, and was highest in shrimp monoculture systems. Compared with the classic shrimp farming industry, the closed shrimp polyculture systems may improve the nitrogen utilization efficiency, and hence reduce the environmental impacts on coastal waters. The nitrogen discharging rates for all the studied polyculture systems ranged from 3.0% to 6.0% of total input nitrogen.

Nitrogen budget in the Changjiang River drainage area

We established a budget model of nitrogen （N） inputs and outputs between watersheds and waterbodies to determine the sources of riverine N in the Changjiang （Yangtze） River drainage area. Nitrogen inputs in the budget included N from synthetic fertilizer, biological fixation by leguminous and other crops, wet/dry atmospheric deposition, excreta from humans and animals, and crop residues. The total N input was estimated to be 17.6 Tg, of which 20% or 3.5 Tg N was transported into waterbodies. Of the total N transported into waterbodies, the largest proportion was N from animal waste （26%）, followed by N from atmospheric wet/dry deposition （25%）, synthetic fertilizer N （17%）, N in sewage wastes （17%）, N in human waste from rural areas （6%） and industrial wastewater N （9%）. We studied the spatial patterns of N inputs and outputs by dividing the Changjiang River drainage area into four sub-basins, from upstream to downstream： the Tongtian River drainage area （TTD, the headwater drainage area, 138 000 l^n2, less disturbed by human activities）; the Jinsha River drainage area （JSD, 347 000 km2, less disturbed by human activities, approx. 3 500 km upstream of the Changjiang estuary）; the Pingshan-Yichang drainage area （PYD, 520 500 krn2, large-scale human disturbance, about 2 000 km upstream of the Changjiang estuary）; and the Yichang-Datong drainage area （YDD, 699 900 km^2, large-scale httman disturbance, approx. 620 km upstream of the Changjiang estuary）. The average N input into waterbodies was 2.3, 7.3, 24.1, and 28.2 kg N/ha in the TTD, JSD, PYD, and YDD sub-basins, respectively, suggesting an increase of N-components of more than 10 times from upstream to downstream areas.

Carbon and nitrogen budget in fish-polychaete integrated aquaculture system

Integrated multi-tropic aquaculture(IMTA)systems have been used in China for many years and have achieved significant economic,social,and ecological benefits.However,there is still a lack of benthic bioremediation species that can effectively utilize the aquaculture particulate organic waste in the system.Polychaete Perinereis aibuhitensis Grube is used as an environmental remediation species for large-scale aquaculture to reduce particulate organic waste,which is of great significance to environmental protection.To improve bio-elements utilization efficiency,P.aibuhitensis was applied for IMTA indoor fish(Hexagrammos otakii)farming.Results showed that in the system,production of 1 kg of the fish discharged 2141-2338 mg of carbon and 529-532 mg of nitrogen,while in the monoculture of the fish,the figures were 3033-3390 mg and 764-794 mg,or 24.84%-35.26%and 30.35%-33.32%less,respectively.This approach promoted IMTA technology that could utilize the particulate organic waste from intensive aquaculture and reduce the adverse environmental effects.

The experimental studies on the carbon and nitrogen budgets of Pseudeuphausia sinica

The carbon and nitrogen budgets were estimated on the adult females, juveniles and post-furcilia larvae of Pseudeuphausia sinica fed on newly hatching nauplii of Artemia salina in the laboratory. It was found that the ingestion rate was linearly related to the food concentration, suggesting high feeding potential. The linear correlation could be established between the respirating rate (carbon consumption rate) and carbon ingestion rate, as well as carbon assimilation rate. The regression coefficients (i.e.specific dynamic action coefficients) were in the range from 9% to 16% (ingested C) or 10% to 17% (assimilated C) respectively, with lower in the post-furcilia larvae. There also existed a linear correlation equation between estimated total nitrogen excretion rate and the rates of nitrogen ingestion and assimilation separately, except for the juveniles. The defecation rates increased with the increase of the ingestion rate; as a result, assimilation efficiency was not related to the ingestion rate, ranging from 0.84 to 0.95. The results inducated that the nitrogen content in food particles was a key factor limiting the growth of P. sinica. The critical ingestion rate was 10 μgN·mg-1 body dry weight per day. Assimilated N was lost mostly by excretion, following allocated to somatic growth. The nitrogen loss by moult only accounted for a minor part. As for carbon budget, respiration and somatic growth also accounted for most of assimilation, but varied with ingestion rates. Moult loss was minor. Estimated reproductive growth (C&N) in the adult females accounted for somewhat higher percent of assimilation than the moult growth. The net growth efficiency (K2) increased with the increase of the ingestion rates, but decreased slightly for juvenile and post-furcilia larvae after the rates up to a certain value.

Nitrogen Budget in Recirculating Aquaculture and Water Exchange Systems for Culturing Litopenaeus vannamei

In order to investigate the culture characteristics of two indoor intensive Litopenaeus vannamei farming modes, recirculating aquaculture system(RAS) and water exchange system(WES), this study was carried out to analyze the water quality and nitrogen budget including various forms of nitrogen, microorganism and chlorophyll-a. Nitrogen budget was calculated based on feed input, shrimp harvest, water quality and renewal rate, and collection of bottom mud. Input nitrogen retained in shrimp was 23.58% and 19.10% respectively for WES and RAS, and most of nitrogen waste retained in water and bottom mud. In addition, most of nitrogen in the water of WES was TAN(21.32%) and nitrite(15.30%), while in RAS was nitrate(25.97%), which means that more than 76% of ammonia and nitrite were removed. The effect of microalgae in RAS and WES was negligible. However, bacteria played a great role in the culture system considering the highest cultivable cultivable bacterial populations in RAS and WES were 1.03×10^(10) cfu mL^(-1) and 2.92×10~9 cfu mL^(-1), respectively. Meanwhile the proportion of bacteria in nitrogen budget was 29.61% and 24.61% in RAS and WES, respectively. RAS and WES could realize shrimp high stocking culture with water consuming rate of 1.25 m^3 per kg shrimp and 3.89 m^3 per kg shrimp, and power consuming rates of 3.60 kwh per kg shrimp and 2.51 kwh per kg shrimp, respectively. This study revealed the aquatic environment and nitrogen budget of intensive shrimp farming in detail, which provided the scientific basis for improving the industrial shrimp farming.

Changes in nitrogen budget and potential risk to the environment over 20 years(1990–2010) in the agroecosystems of the Haihe Basin, China

The nitrogen balance can serve as an indicator of the risk to the environment of nitrogen loss from agricultural land. To investigate the temporal and spatial changes in agricultural nitrogen application and its potential threat to the environment of the Haihe Basin in China, we used a database of county-level agricultural statistics to calculate agricultural nitrogen input, output,surplus intensity, and use efficiency. Chemical fertilizer nitrogen input increased by 51.7% from1990 to 2000 and by 37.2% from 2000 to 2010, concomitant with increasing crop yields.Simultaneously, the nitrogen surplus intensity increased by 53.5% from 1990 to 2000 and by16.5% from 2000 to 2010, presenting a continuously increased environmental risk. Nitrogen use efficiency decreased from 0.46 in 1990 to 0.42 in 2000 and remained constant at 0.42 in 2010,partly due to fertilizer composition and type improvement. This level indicates that more than half of nitrogen inputs are lost in agroecosystems. Our results suggest that although the improvement in fertilizer composition and types has partially offset the decrease in nitrogen use efficiency, the environmental risk has still increased gradually over the past 20 years, along with the increase in crop yields and nitrogen application. It is important to achieve a better nitrogen balance through more effective management to significantly reduce the environmental risk,decrease nitrogen surplus intensity, and increase nitrogen use efficiency without sacrificing crop yields.

Nitrogen and Phosphorus Budget of a Polyculture System of Sea Cucumber(Apostichopus japonicus), Jellyfish(Rhopilema esculenta) and Shrimp(Fenneropenaeus chinensis)

The nitrogen(N) and phosphorus(P) budget and the ecological efficiency of a polyculture system of sea cucumber(Apostichopus japonicus), jellyfish(Rhopilema esculenta) and shrimp(Fenneropenaeus chinensis) were studied in a cofferdam, 120.2 ha in size. The nutrients were supplied by spring tide inflow. In total, 139600 kg N yr-1 and 9730 kg P yr-1 input to the system; while 118900 kg N yr-1 and 2840 kg P yr-1 outflowed from the system concurrently, thus the outflow was 85.7%(N) and 29.2%(P) of inflow. The production of N and P was 889.5 kg yr-1 and 49.28 kg yr-1(sea cucumber) and 204 kg yr-1 and 18.03 kg yr-1(jellyfish and shrimp), respectively. The utilization rate of N and P by polycultured animals was 7.8‰ and 6.9‰, respectively, 21.9% and 38% higher than that of monocultured sea cucumber. Our results indicated that the polyculture system was an efficient culture system of animals and a remediation system of coastal environment as well; it scavenged 14.3% and 70.8% of N and P, respectively. Such an ecological efficiency may be improved further by increasing either the stocking density or the size of sea cucumber or both.

甬江流域氮素收支估算及驱动因素分析

近年来,大量农业氮肥施用、化石燃料使用等人为活动的扰动增加了生态系统的氮输入,导致河流硝酸盐超标、湖库与近岸海域富营养化和土壤酸化等环境问题。长江口-杭州湾是我国近岸海域劣四类水质分布的主要区域,甬江作为汇入杭州湾的重要河流之一,近年来其入海断面总氮浓度和氮通量反弹明显,开展甬江流域的氮收支估算是开展流域氮污染治理与管控、改善近岸海域水质的重要前提。本文利用2021年甬江流域的基本统计数据和相关参数对该区域氮的收支进行估算,阐明了氮收支的主要驱动因素及其对环境的影响。结果表明:2021年甬江流域氮输入量为5.1×10^(4 )t;氮盈余量高达2.17×10^(4) t,占氮输入量的42.56%;流域氮负荷[172.56 kg/(hm^(2)·a)]和陆地氮通量[105.8 kg/(hm^(2)·a)]均高于全国平均水平。氮输入源主要包括人畜排泄、化学氮肥、大气沉降,占比依次为39.11%、26.33%、20.91%;氮输出中,有48%被作物收获带走,有26.98%通过反硝化、氮挥发进入大气,有21.47%以径流的形式进入水环境;从空间分布上,鄞州、镇海等地区面临较为严峻的氮污染潜势。冗余分析(RDA)显示,人口密度、人口数量、农作物种植面积、畜禽数量以及与人类活动有关的工业企业总产值、城镇化程度和GDP是甬江流域氮盈余、氮负荷以及陆地氮通量的主要驱动因素。鉴于甬江流域显著的氮盈余状况,建议采用氮素源头减排治理管控措施以消除氮素盈余对甬江流域氮平衡造成的负面影响。甬江流域氮收支平衡估算可为合理制定氮污染治理管控措施,科学调控流域氮收支和改善近岸海域水环境质量提供科学依据和支撑。

饵料种类及浓度对翡翠贻贝(Perna viridis)生理代谢及碳氮收支的影响

为了探究饵料种类及浓度对翡翠贻贝生理代谢和碳氮收支的影响,在实验室条件下测量了3种微藻饵料(球等鞭金藻、牟氏角毛藻和亚心形扁藻)及3个饵料浓度(2.2、4.4和6.6 mg/L,干重)交互作用下翡翠贻贝的摄食率、呼吸率、排泄率、排粪率及钙化率,继而对翡翠贻贝在相应条件下的碳氮收支进行了计算。研究结果表明:翡翠贻贝摄食率受微藻种类影响不明显,但随饵料浓度的增加而显著增加;呼吸率和排泄率主要受饵料种类影响,且饵料种类和浓度之间存在显著的交互作用,在高饵料浓度条件下牟氏角毛藻组呼吸率高于亚心形扁藻组和球等鞭金藻组;饵料种类和浓度显著影响翡翠贻贝排粪率,在相同饵料浓度下,牟氏角毛藻处理组排粪率高于其他两种微藻组;同种微藻条件下,排粪率随饵料浓度的增加而升高;翡翠贻贝钙化率受饵料种类及浓度影响不显著。碳收支方面,排粪碳与生长碳占翡翠贻贝所摄食碳量的78.37%~96.22%。各饵料组生长碳占比随饵料浓度增加而升高,投喂高浓度(4.4和6.6 mg/L)球等鞭金藻和牟氏角毛藻的翡翠贻贝生长碳占比较高(71.75%~74.49%)。氮收支方面,球等鞭金藻组和亚心形扁藻组翡翠贻贝生长氮随饵料浓度增加而增加,而排泄氮呈相反趋势。低饵料浓度条件下,牟氏角毛藻组生长氮和排粪氮最高,而排泄氮最低。

工程化循环水养殖池塘的氮磷收支研究

为了探寻更清洁高效的养殖模式,研究将淡水池塘循环水养殖系统进行了改良,对5个月试验周期内池塘水体理化指标和氮磷收支情况进行了分析。结果显示,池塘水体的理化指标呈波动性变化,试验结束时总氮、总磷浓度分别为4.85和1.04 mg/L,总氮浓度符合淡水养殖尾水排放二级标准。饲料和底泥是池塘氮磷输入的主要来源,分别占池塘氮元素输入量的50.6%和43.7%,磷元素输入量的49.4%和46.9%;底泥积累是池塘氮磷输出的主要途径,分别占池塘氮磷元素输出量的53.3%和78.7%。试验池塘对氮磷的利用率分别为65.2%和16.6%,其中鲤对氮磷的利用率显著高于其他鱼类(P<0.05),鲢、鳙对磷的利用率无显著差异(P>0.05)。研究表明,改良后的池塘循环水养殖系统有效降低了营养负荷,提高了养殖生物的氮磷利用率,减轻了养殖尾水对周边环境的影响,兼顾生态与经济效益,是一种成本较低且可持续发展的池塘养殖模式。

Nitrogen Flow in the Rural Ecosystem of Mikasa City in Hokkaido, Japan

This study of Mikasa City in 2001, which analyzed N flow between N production and N load in seven agricultural and settlement subsystems, i.e., paddy, onion, wheat, vegetable, dairy, chicken, and citizen subsystems, aimed to compare N flow in each subsystem, to determine the main sources of the N load, and to evaluate the influence of agricultural production and food consumption on N cycling in a rural area. The results showed that in Mikasa city, 38.5% of the N load came from point sources and the remainder from non-point sources with intensive vegetable farming imparting a serious N load. Because of the internal N cycling in the dairy subsystem, chemical fertilizer application was reduced by 70.2%, and 23.72 Mg manure N was recycled to the field; therefore, the N utilization efficiency was raised from 18.1% to 35.1%. If all the manure N in the chicken subsystem was recycled, chemical fertilizer application would be reduced by 8.1% from the present level, and the point sources of N pollution would be reduced by 20.8%.

配合饲料和冰鲜鱼养殖乌鳢池塘氮磷收支及养殖效果比较

为比较不同饵(饲)料对乌鳢(Channa argus)养殖池塘的氮磷收支变化及养殖效果,4月将体质量(310.25±27.72)g的越冬乌鳢鱼种饲养在家庭农场6口池塘中,密度为5000~5300 ind./667m^(2),分别投喂配合饲料和冰鲜鱼,每组设置3口平行池塘,定期监测乌鳢生长和水质,计算池塘氮磷收支,评价生态和经济收益。结果显示:养殖前期冰鲜鱼组乌鳢生长速度快于饲料组,养殖中后期乌鳢生长速度慢于饲料组;饲料是氮磷主要输入来源,分别占饲料组和冰鲜鱼组总氮输入的(88.66±2.06)%和(94.30±2.21)%,占总磷收入的(94.96±2.13)%和(97.10±2.40)%;沉积物是氮磷主要支出方式,分别占饲料组和冰鲜鱼组总氮支出的(39.50±1.17)%和(48.90±1.60)%,占总磷支出的(43.23±1.53)%和(53.78±1.73)%;饲料组氮磷绝对利用率和相对利用率均显著高于冰鲜鱼组,排污系数分别为7.06±0.34和2.10±0.13,均显著低于冰鲜鱼组的21.49±1.01和5.61±0.21;饲料组利润和产出投入比显著高于冰鲜鱼组。综上所述,饲料组生态和经济效益显著优于冰鲜鱼组,应不断优化乌鳢饲料配方,逐步取缔冰鲜鱼,促进乌鳢养殖健康发展。

参虾生态养殖池塘系统氮磷收支、赋存与分布特征研究

为研究生态养殖对池塘氮磷收支、赋存与分布特征影响,采用陆基网式围隔,设置仿刺参(Apostichopus japonicus)(密度:10、15 ind./m^(2))和中国明对虾(Fenneropenaeus chinensis)(密度:0、2、4、8 ind./m^(2))不同放养密度组合。结果表明:收获各组刺参个体重、成活率均无显著差异(P>0.05)。对虾个体重、成活率均较低,且差异显著(P<0.05)。换水是系统氮磷收支主要途径。水层、刚毛藻、渗漏、底质积累、参、虾、吸附等收支都相对较小,组间差异均不显著(P>0.05)。系统水环境氮磷负荷量分别为N-0.7 g/m^(2)、P-0.5 g/m^(2)。系统沉积物氮磷含量呈明显季节性变化,其中总氮(TN)、铵态氮(NH_(4)^(+)-N)、总磷(TP)、有机态磷(简称O-P)含量季节性变化趋势基本一致,即5月、11月低,7月、9月高。特征性磷季节性变化趋势和垂直分布趋势较复杂。相关性分析结果显示,沉积物特征性磷的赋存和分布与TP、TN、NH4+-N含量密切相关。初步揭示出不投喂参虾生态养殖系统氮磷变化规律,以期为海水绿色生态养殖提供基础理论依据。

Designing a Regional Nitrogen Cycle Module of Grassland for the IAP-N Model

Assessment of the nitrogen （N） balance and its long-term trend is necessary for management practices because of the negative environmental effects caused by an imbalance of reactive N in grassland ecosystems. In this study, we designed a module for the IAP-N （Improving Anthropogenic Practices of managing reactive Nitrogen） model to enable it to assess the N budget of regional grasslands. The module was developed to quantify the individual components of the N inputs and outputs for grassland ecosystems using livestock and human populations, grassland area, and fossil-energy consumption data as the model inputs. In this paper, the estimation approaches for individual components of N budget, data acquisition, and parameter selection are described in detail. The model was applied to assess the N budget of Inner Mongolia in 2006 at the county scale. The simulation results show that the most important pathway of N outputs from the grassland was livestock intake. The N output from livestock intake was especially large in the middle of Inner Mongolia. Biological fixation, atmospheric deposition, and livestock excreta deposition were comparably important for the N inputs into the grassland. The N budget for Inner Mongolia grassland in 2006 was -1.7×10 8 ±0.6×10 8 kg. The case study for Inner Mongolia shows that the new grassland module for the IAP-N model can capture the characteristics of the N budget in a semiarid grassland.

The fate of ^(15)N-labeled nitrogen inputs to pot cultured beech seedlings

The partitioning of nitrogen deposition among forest soil （including forest floor）, leachate and above- and belowground biomass of pot cultured beech seedlings in comparison to non-cultured treatments were investigated by adding 1.92 g.m^-2 ^15N tracer in throughfall for two successive growing seasons at a greenhouse experiment. Ammonium and nitrate depositions were simulated on four treatments （cultured and non-cultured） and each treatment was labeled with either ^15N-NH4^＋ or ^15N-NO3^-. Total recovery rates of the applied ^15N in the whole system accounted for 74.9% to 67.3% after ^15N-NH4^＋ and 85.3% to 88.1% after ^15N-NO3^-in cultured and non-cultured treatments, respectively. The main sink for both ^15N tracers was the forest soil （including forest floor）, where 34.6% to 33.7% of ^15N-NH4^＋ and 13.1% to 9.0% of ^15N-NO3^-were found in cultured and non-cultured treatments, respectively, suggesting strong immobilization of both N forms by hetero- trophic microorganisms. Nitrogen immobilization by microorganisms in the forest soil （including forest floor） was three times higher when ^15N-NH4^＋ was applied compared to ^15N-NO3^-. The preferential heterotrophic use of ammonium resulted in a two times higher retention of deposited ^15N-NH4^＋ in the forest soil as compared to plants. In contrast, nitrate immobilization in the forest soil was lower compared to plants, although statistically it was not significantly different. In total the immobilization of ammonium in the plant-soil system was about 60% higher than nitrate, indicating the importance of the N-forms deposition for retention in forest ecosystems.

水氮运筹影响高留残茬黑土稻田碳收支机理分析

为探明水氮运筹对稻田生态系统碳收支的影响,开展大田试验,设置浅湿干灌溉(D)和淹水灌溉(F)两种灌溉模式,及110kg/hm^(2)(当地施肥标准,N1)、99kg/hm^(2)(减氮10%,N2)和88kg/hm^(2)(减氮20%,N3)3个施肥水平,观测高留残茬稻田水稻收获后不同器官的干物质量及碳含量,同时监测稻田CO_(2)和CH4排放通量,计算水稻净初级生产力(NPP)和稻田净生态系统初级生产力(NECB)。结果表明:水氮运筹会影响稻株各器官干物质及碳含量,所有处理中DN2处理NPP最大(8918.02kg/hm^(2)),浅湿干灌溉模式各处理NPP均大于淹水灌溉模式,分别增加12.13%、36.73%、8.01%;浅湿干灌溉模式增加了稻田土壤呼吸的CO_(2)排放通量,减施氮肥则降低了CO_(2)排放通量,浅湿干灌溉减施氮肥降低了CH_(4)排放通量;两种灌溉模式下各处理CO_(2)和CH_(4)排放总量均随氮肥施用量减少而降低,淹水灌溉模式下各处理CH_(4)排放总量均显著高于浅湿干灌溉模式(P<0.05);各处理稻田生态系碳净收支均为正值,黑土区高留残茬稻田生态系统表现为碳“汇”,其中DN2处理NECB最高,为1950.96kg/hm^(2)。综合来看,浅湿干灌溉模式+减氮10%处理的稻田生态系统碳“汇”最强。研究可为寒地黑土保护提供理论参考和技术支撑。

Evaluation of phosphorus and nitrogen balances as an indicator for the impact of agriculture on environment: A comparison of a case study from Poland and Mississippi US

The objective of this research was to quantify the changes of nitrogen (N) and phosphorus (P) balances in Poland and Mississippi (MS), USA. Nutrient balances were calculated as difference between input and output in the agricultural system according to Organisation for Economic Cooperation and Development (OECD) methodology. A positive nutrient balance means that a potential environmental problem may result from that nutrient;a negative nutrient balance means there is a potential yield loss. The N and P soil surface balances for Poland and MS were calculated for the year 1998 through 2008. The results showed that both MS and Poland had positive N and P balances, indicating that there was a surplus of N and P. The average balance for N was 48 kg·ha-1 in Poland and 102 kg·ha-1 in MS. For P, it was 3 kg·ha-1 in Poland and 19 kg P kg·ha-1 in MS per cultivated area. This research demonstrated that the nutrient balance of N or P depended on the efficient use of each nutrient and type and source of fertilizer used. This research is significant for N and P fertilizer management and their impact on agriculture production and environment health.

海洋系统中氮的生物地球化学循环回顾与展望

氮(N)是地球上所有生命必不可少的营养物质,对生态环境有着重大而广泛的影响。近几年来,氮循环的研究在地球生物学、地球化学、海洋科学、大气科学和生态健康等领域取得重大进展。在这里,我们回顾了海洋系统中氮循环的重要进展,总结了现代人类对海洋系统氮循环的影响和相应的反馈,并对未来海洋氮循环进行展望。氮同位素(δ^(15)N)是评估氮循环的重要工具,可信的证据表明氧气(O_(2))的波动对氮循环的演化具有显著的促进作用。海洋氮循环显然与生物演化和环境演变密切相关,特别关注了埃迪卡拉-早寒武世、晚奥陶纪-早志留纪和晚二叠纪-早三叠纪三个阶段全球氮循环对生命演化和环境演变的耦合。自从进入人类世以来,人类活动极大的加快活性氮(Nr)的排放以满足农业和工业的需求,同时大量Nr向海洋系统的输入引起一系列具有成因关联的生物地球化学反馈,对环境变化、其他元素循环和人类健康产生了强烈的影响。随着Nr向海洋系统的持续过量输入,过量的Nr排放已被视为全球环境问题之一,一系列关键性问题亟需研究。

不同生长阶段红鳍东方鲀(Takifugu rubripes)循环水养殖系统的水质调控和氮磷收支研究

循环水养殖系统具有节水、省地、环保等优点,目前在国内外水产养殖中得到广泛应用,养殖过程中水质的动态变化反映鱼类养殖生长环境状况,氮磷收支规律反馈养殖系统是否具有高效性,二者可评估特定养殖生物在特定养殖条件下的养殖效果。为了了解循环水养殖系统水质变化与氮磷收支规律,通过对不同生长阶段(一龄与二龄)红鳍东方鲀循环水养殖系统的水质、鱼体及饲料中氮、磷的定期采样,计算氮、磷的输入与输出量,比较了系统水质变化与氮磷收支规律。结果显示,一龄和二龄的红鳍东方鲀养殖系统分别在投喂后2、4、10、14 h和2、4、14、18 h出现营养盐浓度高值点,建议针对处于不同生长阶段的红鳍东方鲀养殖系统需对不同时间段进行水质重点监测,主成分分析表明亚硝酸盐氮和硝酸盐氮参数可作为红鳍东方鲀循环水养殖水质的指示因子。一龄和二龄的红鳍东方鲀养殖系统中用于鱼体生长发育的氮元素分别占总输出的25.16%和28.41%,用于鱼体生长发育的磷元素分别占总输出的47.37%和51.66%,二龄的红鳍东方鲀养殖系统与一龄养殖系统的氮磷吸收率相比有显著性提高(P<0.05)。实际生产中可通过增加二龄红鳍东方鲀专用饲料蛋白质与磷元素含量,提升养殖产量。研究阐明了循环水养殖系统水质变化与氮磷收支规律,营养物质的来源与归宿,对合理评价系统的经济与生态效益、优化系统工艺参数具有指导意义。