大型溞引导的沉水植被生态修复对滴水湖水质的净化效果

2007年4月-2008年1月,在滴水湖D港中段长950m(水量为10000m3)的修复区内投放大型溞(Daphnia magna),以滤除水华藻类等颗粒有机物,然后移栽伊乐藻、苦草、轮叶黒藻、光叶眼子菜和菹草等沉水植物,逐月监测水体中总氮(TN)、铵态氮(NH4+-N)、硝态氮(NO3--N)、亚硝态氮(NO2--N)、总磷(TP)、活性磷酸盐(PO43--P)和COD等水质指标,分析沉水植被栽培对滴水湖水体水质的净化效果.结果表明:试验期间,修复区水体TN、TP、NO3--N、NO2--N、NH4+-N、PO43--P和COD显著低于对照区(P0.01),溶解氧(DO)增加了50.4%,水体透明度(SD)平均在3.4~3.7m,水质达到国家Ⅱ~Ⅲ类地表水水质标准;2008年3月应用已构建的沉水植被群落对富营养化流水水体水质进行净化试验,7d后修复区流水水体除BOD外,TN、TP、NO3--N、NO2--N、NH4+-N、PO43--P和COD均显著降低(P0.01),DO增加了17.98%,SD提高了30cm.利用大型溞控藻后移栽沉水植物对滴水湖水体水质的净化效果十分显著.     

龙须菜对富营养化海水的生物修复

于2002年至2004年期间,在福建省东山岛的八尺门鱼类网箱养殖区、西埔湾对虾养殖区、乌礁湾鲍鱼养殖区等进行了龙须菜(G racilaria lem aneaf orm is)对动物海水养殖造成的富营养化的生物修复研究。结果表明,从围隔实验到小面积的海区实验到大面积的海区推广试点,龙须菜对富营养化的海水均有良好的修复效果。围隔实验中,龙须菜能使网箱养殖区缺氧的海水达到过饱和状态,对无机氮(IN)、无机磷(IP)的去除率达80%以上;实验海区,修复区的溶解氧(DO)浓度明显高于非修复区,IN、IP、叶绿素(Ch l-a)浓度低于非修复区;推广海区,鲍鱼养殖污水流经龙须菜养殖区后,IN、IP得到有效的吸收,DO浓度得到提高。因此,大面积养殖龙须菜对减轻养殖污水对海区的污染,防止水体富营养化,抑制赤潮的发生有积极作用。     

富营养化河道引清渐推生态修复工程模式研究

2014 年2 月10 日至3 月28 日对滴水湖外围中涟河道实施以引清调水引导的沉水植物生态修复工程, 从临近的D 港引入清水快速提高水体透明度, 然后移栽苦草(Vallisnerianatans)、伊乐藻(Elodea nuttalii)、龙须眼子菜(Potamogetonpectinatus)等沉水植物, 构建水生植物群落。跟踪监测总氮(TN)、氨态氮(NH4⁺-N)、硝态氮(NO3^–-N)、亚硝态氮(NO₂^–-N)、总磷(TP)和磷酸盐(PO₄^3–-P)等水质指标, 分析该生态工程对富营养化河道的修复效果。结果表明: 工程实施后第2 个月, 修复区沉水植物的覆盖率由移栽初期的60%提高到85%, 水体综合营养状态指数比对照区降低了19.31%, 达到中营养水平, 修复效果显著(P<0.05)。6 个月后, 修复河道水体内总氮、氨态氮、硝态氮、亚硝态氮、总磷、磷酸盐的浓度与对照区相比显著降低, 削减率分别为43.86%、61.17 %、51.90 %、72.62 %、43.86 %和55.71%, 水体透明度比对照区提高81.82%, 综合营养状态指数显示修复区水体仍保持在中营养状态。引清渐推生态修复工程对富营养化河道修复效果明显, 为我国南方河网较密集区的河道生态修复提供更多的治理思路。     

太湖五里湖生态修复示范区水质改善效果分析

鱼类清除和沉水植被恢复常是富营养化浅水湖泊生态系统修复的重要手段。为探讨这种生态系统修复方式对亚热带富营养化浅水湖泊太湖五里湖水质的改善效果,论文研究了五里湖生态修复区与未进行任何修复的对照湖区为期6个月(2010年7～12月)的水质监测数据。数据分析结果表明,生态修复区总氮(TN)、总磷(TP)、叶绿素-a(Chl-a)以及悬浮质(TSS)浓度显著降低,分别比对照区低43.4%、48.3%、65.5%和78.9%,透明度则明显升高,约为对照区的3倍。本研究表明以鱼类清除和沉水植被恢复为主要手段的生态系统修复措施能够有效改善亚热带富营养化浅水湖泊水体的水质。     

象山港网箱养殖区与非养殖区的细菌群落分布

近海集约化养殖是导致我国近海污染的主要来源之一。浮游细菌在近海生态系统的物质循环过程中发挥重要作用,研究海洋浮游细菌群落对养殖活动的响应,对于指示和评价海水养殖生态系统健康具有重要意义。采集了象山港网箱养殖区与非养殖区3个深度,包括表层(0.5 m)、中层(2.5 m)、底层(8.0 m)的水样,利用焦磷酸测序技术测定16S rRNA基因,研究浮游细菌的群落结构和多样性。结果表明:网箱养殖活动不仅使得附近区域水体理化性质发生改变,如化学需氧量浓度显著高于非养殖区域,而且显著地(P0.05)改变了浮游细菌的群落结构,但不同深度间群落结构和多样性的差异不显著。网箱养殖区和非养殖区中主要浮游细菌类群为α-变形菌(Alphaproteobacteria)、γ-变形菌(Gammaproteobacteria)、拟杆菌(Bacteroidetes)、放线菌(Actinobacteria)、β-变形菌(Betaproteobacteria)、ε-变形菌(Epsilonproteobacteria)和其它变形菌(Unclassified Proteobacteria),占细菌总序列数的98.64%。有些细菌类群的平均相对丰度从网箱区到非养殖区差异显著,如拟杆菌(P0.01)和放线菌(P0.05)显著降低,而γ-变形菌(P0.05)显著增加。相似度分析表明γ-变形菌、α-变形菌和拟杆菌是造成网箱区和非养殖区群落差异的主要类群,对群落差异总贡献率达到45.02%。偏冗余分析表明,影响细菌群落分布的主要环境因子有化学需氧量、磷酸盐、铵盐和总有机碳,共解释38.18%的群落变异,空间距离单独解释10.66%的群落变异。实验结果表明,养殖活动导致浮游细菌群落的改变,其中拟杆菌、放线菌和γ-变形菌的丰度显著变化,可能用于评价养殖水体的水质状况。     

象山港网箱养殖区水体和沉积物的细菌生态分布

2006年1月和10月对象山港网箱养殖区细菌数量分布及群落结构进行研究,并与周边非养殖海域进行了比较。结果显示水体和沉积物细菌数量均呈现10月份1月份、网箱养殖区网箱外侧对照区近湾顶对照区近湾口对照区的分布特点,其中网箱养殖区水体异养细菌、弧菌数量分别在1.0×106—7.2×107CFU/L和1.6×105—1.3×106CFU/L之间,沉积物异养细菌、弧菌数量分别在5.9×102—6.1×105CFU/g和8.0×101—7.4×104CFU/g之间。网箱养殖区水体分离细菌89株,归属于12个属,其中不动杆菌属(Acinetobacter)、假单胞菌属(Pseudomonas)、弧菌属(Vibrio)等为优势菌属;沉积物分离细菌136株,归属于10个属,其中假单胞菌属(Pseudomonas)、弧菌属(Vibrio)、芽孢杆菌属(Bacillus)、不动杆菌属(Acinetobacter)等为优势菌属。由于长期受到高营养盐、高有机质等外界条件的选择作用,网箱区及网箱外侧对照区海域的细菌群落多样性较低,某些特定的细菌类群富集。研究表明网箱养殖区的细菌分布和菌属组成特征与养殖自身污染密切相关,并且养殖过程对细菌群落产生的影响已扩展至网箱外侧的邻近海域。     

连续可调式沉水植物网床对河道水质的修复

在太湖贡湖水源保护区陆域的一条长约200 m的污染河道内构建了一系列连续可调式沉水植物网床,形成了以菊花草、苦草、伊乐藻、轮叶黑藻和菹草等沉水植物构成的水生植物群落;跟踪监测了总氮(TN)、铵态氮(NH4 +-N)、亚硝态氮(NO2--N)、硝态氮(NO3--N)、总磷(TP)和磷酸盐(PO43--P)等水质指标,分析沉水植物网床引导沉水植被恢复对污染河道的水质修复效果.结果表明:沉水植被网床构建后,水体透明度显著升高,由修复前的0.5m提高到1.7 ～1.8 m;在沉水植被网床构建后的第5天和第20天,TN和TP的削减率分别为35.6％、66.3％和29.4％、63.2％;5个月后,修复河道水体内NH4+-N、NO2--N、NO3--N、TN、PO43--p和TP的浓度比对照组显著降低,削减率分别达到92.4％、76.8％、72.7％、73.9％、90.5％和92.0％.由连续可调式沉水植被网床引导恢复的水生植物群落可用于河道,特别是陆域浅水污染水体的生态修复.     

固定化微生物菌剂与蕹菜对中华鳖养殖污水的净化效果研究

为解决中华鳖(Trionyx sinensis)养殖所造成的水环境污染问题,研究利用海藻酸钠、沸石对复合光合菌剂和枯草芽孢杆菌菌剂分别进行固定化,并研究了不同固定化微生物菌剂与蕹菜对中华鳖养殖污水的净化效果。结果表明:净化处理15d后,利用固定化微生物菌剂与蕹菜共同处理组对中华鳖养殖污水的净化处理效果最好,养殖污水的CODMn、NH 4+-N、NO3-N、NO 2-N、PO34的去除率分别为88.7%、87.3%、90.8%、98.3%、74.9%。蕹菜处理组对于NO3-N、NO 2-N、NH 4+-N的去除率显著高于固定化复合光合菌剂处理组和固定化枯草芽孢杆菌处理组。固定化复合光合菌剂处理组对于NO3-N、NO 2-N、NH 4+-N的去除率显著高于固定化枯草芽孢杆菌菌剂处理组,但固定化枯草芽孢杆菌处理组对于污水的CODMn的去除率最高,可达90.6%。     

围塘清洁养殖模式的构建及其环境效应

采用陆基围隔方法,构建了单养鱼(F)、鱼+藻(FG)、鱼+藻+沙蚕(FGP)以及鱼+沙蚕(FP)4种养殖模式,试验生物包括菊花江蓠(Gracilaria lichenoides)、双齿围沙蚕(Perinereis aibuhitensis)和黑鲷(Sparus macrocephlus),分别对不同养殖模式系统中水体及沉积物的氮、磷等进行跟踪监测,分析其环境效应.结果表明:在4个模式中,放养菊花江蓠1.5kg·m-2、双齿围沙蚕22.5 kg·hm-2的密度下,能够对养殖水体及沉积物起到较好的净化效果,并且能够有效提高黑鲷的收获规格及产量;其中菊花江蓠主要体现在对于水体中DIN和DIP的净化,具藻处理中氮、磷含量均较不具藻处理低(P＜0.05),而具藻处理(FG、FGP)和不具藻处理(F、FP)之间差异不显著(P＞0.05).双齿围沙蚕主要体现在对于沉积物POM的修复,具沙蚕处理的氮、磷含量均低于不具沙蚕处理,这在1～2 cm和2～4 cm 2个层段中特别明显,具沙蚕处理沉积物中总氮、总磷要较不具沙蚕处理分别低7%和9%,两者差异显著(P＜0.05).搭配藻类或沙蚕处理的黑鲷养殖产量都显著高于单养黑鲷处理(P＜0.05),其中FGP处理黑鲷产量比F处理高57%.综合考虑,FGP模式具有最佳的环境效益、产量效益及综合效益.     

虾-鱼-贝-藻养殖结构优化试验研究

本研究建立了一种虾、鱼、贝、藻优化养殖结构及水质调控系统,该系统包括对虾养殖、鱼类养殖、贝类养殖、大型海藻栽培等4个功能不同的养殖区,1个益生菌及微藻培养区和1个水处理区以及1条应急排水渠。通过在封闭循环水养殖系统内不同池塘中放养生态位互补的对虾、口孵非鲫、牡蛎、江蓠等经济动植物,对虾池水质环境进行生物调控与自我修复。结果表明,循环水养殖系统内虾池水层悬浮物数量、COD值、氨态氮和总氮含量比对照组对虾单养池明显降低。养殖后排放水不处于富营养化状态(E<1)。投入每千克对虾饲料生产0.667kg对虾,同时生产0.037kg口孵非鲫、0.738kg牡蛎、0.437kg江蓠,相当于净增产值2.01元。投入与产出比,对虾单养为0.671,优化生态养殖为0.235,明显降低。该养殖模式不仅实现了虾池水质环境的自我修复与调控及养殖期间用水的零排放,而且饲料利用率大幅度提高,经济效益显著增加,还具有防病性、环保性、高效性等优点。     

Seasonal ammonium uptake kinetics of four brown macroalgae: Implications for use in integrated multi-trophic aquaculture

Journal of Applied Phycology - The combined culture of fed species (bivalves, fish) and macroalgae, known as integrated multi-trophic aquaculture (IMTA), has been suggested as a method of...     

Growth of <Emphasis Type="Italic">Mytilus galloprovincialis</Emphasis> (mollusca,bivalvia) close to fish farms: a case of integrated multi-trophic aquaculture within the Tyrrhenian Sea

A current practice of marine aquaculture is to integrate fish with low-trophic-level organisms (e.g. molluscs and/or algae) during farming to minimise effects of cultivation on the surrounding environment and to potentially increase economic income. This hypothesis has been tested in the present article experimentally, by co-cultivating fish and mussels (Mytilus galloprovincialis) in the field. Integrated multi-trophic aquaculture (IMTA) experiments were started in July 2004 by transplanting mussel seed at two depths (−3 and −9 m) within 1,000 m downstream to fish cages and at 1,000 m upstream from cages. Mussels were cultured in nylon net bags for 12 months and the growth recorded biometrically. The outcome of our field experiment corroborated the idea of IMTA effectiveness. In fact, in the study area, the organic matter from fish-farm biodeposition caused changes in the chemical environment (i.e. controls and impacted sites were significantly different for organic matter availability and chlorophyll-a) and this induced changes in growth performance of co-cultivated mussels. Mussels cultivated close to cages, under direct organic emission, reached a higher total length, weight and biomass than mussel cultivated far from farms.     

Availability and utilization of waste fish feed by mussels Mytilus edulis in a commercial integrated multi-trophic aquaculture (IMTA) system: A multi-indicator assessment approach

Fish feed waste enhancement of the particulate food supply and performance of mussels Mytilus edulis suspended near salmon cages at an integrated multi-trophic aquaculture (IMTA) site was assessed using a multi-indicator approach. Dietary indicators included bulk measurements of seston quantity and nutritional quality, proximate analysis (PA), fatty acid (FA) and stable isotope (SI) composition. Mussel tissue indicators consisted of PA and FA composition. Mussel performance was assessed from physiological integrations (scope for growth, SFG), growth efficiency (K₂) and condition index (CI). All measurements were made over 2 days at a commercial IMTA farm and a monoculture mussel farm in the Bay of Fundy (Canada). Significant differences detected in seston quantity and quality were within the range of natural spatial variability. The SFG of IMTA mussels was lower (28.71 J h⁻¹) than monoculture mussels (38.71 J h⁻¹) and reflected site differences in natural food availability and composition that affected absorption rate. PA of mussel organs didn't reflect a significant fish feed contribution to the mussel diet. However, dietary enhancement and assimilation of fish feed waste was demonstrated by significantly higher levels of feed FA biomarkers 20:1ω9, 18:2ω6, 18:1ω9 and low ω3/ω6 ratio in seston, mussel tissues and feces at the IMTA site than at the mussel farm. SI (δ¹³C and δ¹⁵N) in seston and mussel feces significantly differed among sites and IMTA mussels had significantly higher CI (21%) than monoculture individuals (16%). It was concluded that bulk indicators of the diet, short-term physiological integrations, and PA of mussel tissues have a limited capacity to detect dietary enhancement at IMTA sites. FA and SI tracers of fish feed waste were shown to be more sensitive for detecting the low-levels of diet enhancement within the large range of natural seston variation.     

微生态制剂对刺参幼参在封闭式循环养殖系统中的应用研究

目的对循环水养殖系统水质指标和刺参幼参的生长代谢进行分析。方法在水温（16±1）℃的循环养殖系统中投喂不同的微生态制剂。结果30d实验结果表明：循环养殖系统具有一定自净能力,微生态制剂能够显著延长循环养殖系统的自净周期。其中“EM菌剂”在控制溶解氧含量等方面具有优势。结论复合微生态制剂“海微净水剂”和“hEM菌剂”在降解氨氮、亚硝酸盐、磷酸盐和化学耗氧量等方面效果较单一微生态制剂“EM菌剂”效果好,并且刺参的生理活动也较强。此外“NEM菌剂”能够显著提高刺参幼参的生长速度。     

Planktonic and sediment bacterial communities in an integrated mariculture system

An integrated multi-trophic aquaculture (IMTA) system, with one fish cage model surrounded by an island and shellfish rafts, was used in the current study. Planktonic and sediment bacterial communities in the IMTA system were monitored over four seasons in 2019. In both plankton and sediment samples, the most dominant phyla were Proteobacteria and Bacteroidota. Sediment bacterial samples were more similar and had higher levels of biodiversity than planktonic bacterial samples. Obvious seasonal variations were found in plankton samples, but not in sediment samples. No obvious inter-site variations in planktonic and sediment bacteria (fish cages, shellfish rafts and control sites) were found and the results suggested that no obvious impact of feeding operations in fish culture cage model on bacterial communities in the IMTA system was observed in this study. Based on the sequence data, some faecal indicator bacteria and potentially pathogenic bacterial species were detected. According to the results, the bacterial water quality in the IMTA system was acceptable. PICRUSt (Phylogenetic Investigation of Communities by Reconstruction of Unobserved States) analysis revealed that the primary difference in potential functional roles of planktonic and sediment bacteria was amino acid transport and metabolism, which was active in different seasons.     

Accounting for inventory data and methodological choice uncertainty in a comparative life cycle assessment: the case of integrated multi-trophic aquaculture in an offshore Mediterranean enterprise

Purpose

Integrated multi-trophic aquaculture (IMTA), growing different species in the same space, is a technology that may help manage the environmental impacts of coastal aquaculture. Nutrient discharges to seawater from monoculture aquaculture are conceptually minimized in IMTA, while expanding the farm economic base. In this study, we investigate the environmental trade-offs for a small-to-medium enterprise (SME) considering a shift from monoculture towards IMTA production of marine fish.

Methods

A comparative life cycle assessment (LCA), including uncertainty analysis, was implemented for an aquaculture SME in Italy. Quantification and simultaneous propagation of uncertainty of inventory data and uncertainty due to the choice of allocation method were combined with dependent sampling to account for relative uncertainties and statistical testing and interpretation to understand the uncertainty analysis results. Monte Carlo simulations were used as a propagation method. The environmental impacts per kilo of fish produced in monoculture and in IMTA were compared. Twelve impact categories were considered. The comparison is first made excluding uncertainty (deterministic LCA) and then accounting for uncertainties.

Results and discussion

Deterministic LCA results evidence marginal differences between the impacts of IMTA and monoculture fish production. IMTA performs better on all impacts studied. However, statistical testing and interpretation of the uncertainty analysis results showed that only mean impacts for climate change are significantly different for both productive systems, favoring IMTA. For the case study, technical variables such as scales of production of the species from different trophic levels, their integration (space and time), and the choice of species determine the trade-offs. Also, LCA methodological choices such as that for an allocation method and the treatment of relative uncertainties were determinant in the comparison of environmental trade-offs.

Conclusions

The case study showed that environmental trade-offs between monoculture and IMTA fish production depend on technical variables and methodological choices. The combination of statistical methods to quantify, propagate, and interpret uncertainty was successfully tested. This approach supports more robust environmental trade-off assessments between alternatives in LCAs with uncertainty analysis by adding information on the significance of results. It was difficult to establish whether IMTA does bring benefits given the scales of production in the case study. We recommend that the methodology defined here is applied to fully industrialized IMTA systems or bay-scale environments, to provide more robust conclusions about the environmental benefits of this aquaculture type in Europe.

     

刺参对浅海筏式贝类养殖系统的修复潜力

浅海筏式养殖滤食性贝类产生大量的粪便和假粪（总称生物沉积物）,对海水养殖环境产生一系列影响;而沉积食性海参能够有效清除颗粒有机物,在海水养殖系统中扮演“清道夫”的生态角色.为评估刺参在浅海筏式贝类养殖系统中的生物修复潜力,本文在不同季节现场研究了贝 参混养模式下刺参对贝类生物沉积物的摄食及生长和排泄特征.结果表明: 刺参能够在新设计的养殖设施中与滤食性贝类混养,最大生长率达0.34%·d^-1; 并可通过摄食有效清除贝类生物沉积物, 摄食率为0.1746 g·g^-1·d^-1（夏季,21.2 ℃）、0.0989 g·g^-1·d^-1（秋季,19.2 ℃）和0.0050 g·g^-1·d^-1（冬季,7.7 ℃）;刺参主要通过排泄溶解形态的NH₄⁺N和PO₄^3- -P来促进沉积物中营养盐的再生,其排泄率也呈现明显的季节变化.基于现场试验数据,估算了刺参在桑沟湾的生物修复潜力, 刺参与贝类混养可摄食4.5～159.6 kg·hm^-2·d^-1生物沉积物、排泄1 382.5～3 678.1 mmol·hm^-2·d^-1NH₄⁺ -N及74.6～335.7 mmol·hm^-2·d^-1PO₄^3--P.表明刺参对浅海筏式贝类养殖系统具有较大的生物修复潜力,贝-参混养模式不仅能够取得较大的生态效益,而且能显著增加养殖生产的经济效益.     

Potential of the seaweed Gracilaria lemaneiformis for integrated multi-trophic aquaculture with scallop Chlamys farreri in North China

In this study the red alga, Gracilaria lemaneiformis, was cultivated with the scallop Chlamys farreri in an integrated multi-trophic aquaculture (IMTA) system for 3 weeks at the Marine Aquaculture Laboratory of the Institute of Oceanology, Chinese Academy of Sciences (IOCAS) in Qingdao, Shandong Province, North China. The nutrient uptake rate and nutrient reduction efficiency of ammonium and phosphorus from scallop excretion were determined. The experiment included four treatments each with three replicates, and three scallop monoculture systems served as the control. Scallop density (407.9 ± 2.84 g m⁻³) remained the same in all treatments while seaweed density differed. The seaweed density was set at four levels (treatments 1, 2, 3, 4) with thallus wet weight of 69.3 ± 3.21, 139.1 ± 3.80, 263.5 ± 6.83, and 347.6 ± 6.30 g m⁻³, respectively. There were no significant differences in the initial nitrogen and phosphorus concentration between each treatment and the control group (ANOVA, p > 0.05). The results showed that at the end of the experiment, the nitrogen concentration in the control group and treatment 1 was significantly higher than in the other treatments. There was also a significant difference in phosphorus concentration between the control group and the IMTA treatments (ANOVA, p < 0.05). Growth rate, C and N content of the thallus, and mortality of scallop was different between the IMTA treatments. The nutrient uptake rate and nutrient reduction efficiency of ammonium and phosphorus changed with different cultivation density and time. The maximum reduction efficiency of ammonium and phosphorus was 83.7% and 70.4%, respectively. The maximum uptake rate of ammonium and phosphorus was 6.3 and 3.3 μmol g⁻¹ DW h⁻¹. A bivalve/seaweed biomass ratio from 1:0.33 to 1:0.80 (treatments 2, 3, and 4) was preferable for efficient nutrient uptake and for maintaining lower nutrient levels. Results indicate that G. lemaneiformis can efficiently absorb the ammonium and phosphorus from scallop excretion and is a suitable candidate for IMTA.     

THE USE OF SEAWEEDS IN INTEGRATED AQUACULTURE: THE CHILEAN EXPERIENCE

Buschmann, A. H. Departamento de Acuicultura, Universidad de Los Lagos, Casilla 933, Osorno, Chile.abuschma@ulagos.cl In Chile, salmon cultivation is well established, and produces over 200,000 tons yr-1. Integrated aquaculture has been proposed as an environmentally friendly way of recycling the waste of intensive aquaculture practices. An initial approach has been considered which contemplates the use of culture lines surrounding fish cages. Several studies have demonstrated under these conditions seaweeds can maintain higher production levels and present higher nitrogen contents as compared to cultures without the presence of fish cages. However, success has not been total, partly because the amount of seaweeds required to remove a significant proportion of the waste produced from intensive large-scale cultivation systems is very large. In this context, the use of a multi-layered seaweed cultivation of Gracilaria and Macrocystis is suggested. On the other hand, land-based systems have been proposed as a technological alternative for integrated aquaculture. The latter type of systems are technically feasible, although, the high level of investment required at present. Our results indicate that Gracilaria is capable of removing a significant proportion of the ammonium excreted by fish. These studies indicate that annual fish production can reach over 30 kg.m-3, with an associated Gracilaria production of 49 kg (wet). m-2. y-1. Finally, the environmental benefits associated with the development of integrated tank cultivation were assessed indicating that by integrating seaweed cultivation into a fish farm, the economic profitability of a commercial fish operation is not affected when internalizing the environmental costs which could be incurred for environmental compliance. (Grant: FONDEF D991/1101)     

元素硫和双氰胺对蔬菜地土壤硝态氮淋失的影响

采用温室盆栽淋洗试验,以NH₄HCO₃为氮肥源,研究了元素硫(S₀)和双氰胺（DCD）对种葱和不种作物土壤NO₃^--N淋失量和NO₃^--N、NH₄⁺-N浓度的影响.结果表明,在12周试验期间,与对照相比,S₀+DCD和S₀处理NO₃^--N淋失量分别低83%～86%和83%;NH₄⁺-N淋失量分别高16.8～21.0 mg·盆^-1和20.4～25.0 mg·盆^-1;而同期无机氮（NO₃^--N、NH₄⁺-N）淋失量则低60%.试验结束后,,S₀+DCD和S₀处理土壤无机氮含量分别比对照高79.9%～85.4%和74.9%～82.6%,以NH₄⁺-N为主.S₀+DCD处理无机氮淋失量比S₀和DCD处理分别低4.6%～14.4%和15.4%～30.1%;试验结束后土壤无机氮分别高6.1%和16.8～36.0%.在Na₂S₂O₃+DCD、Na₂S₂O₃和DCD处理中也发现类似结果.可见S₀施入土壤具有与DCD同样的氨稳定和硝化抑制作用.S₀与DCD配合施用可使DCD的硝化抑制性增强,其作用机理是S₀氧化中间体S₂O₃^2-、S₄O₆^2-,具有抑制硝化和DCD降解作用,延缓DCD硝化抑制效果.S0与DCD配合施用可用于延缓太湖流域蔬菜地土壤NH₄⁺-N向NO₃^--N转化,减少氮向水体迁移风险.