海带对富营养化水体的生物修复效果与固碳能力

选择舟山市桃花岛碳汇渔业示范区作为调研对象,于2013年2-8月对网箱养殖区、海带养殖区、海带养殖区上游(对照点)和海带养殖区下游各站位水质参数以及海带生物量的变化进行了为期7个月的跟踪调研。调查结果显示,海带在减轻海水富营养化方面效果显著,在去除海水无机氮方面尤为明显。与对照点相比,海带养殖区下游无机氮平均浓度降低了15.3%,水体富营养化得以改善,网箱养殖区海水与对照点相比,无机氮平均浓度显著降低(P0.05),海带养殖未使海水中有机质含量升高。在固碳能力方面,该海域海带的年固碳能力为0.234kg/m~2,通过标准化转换,固碳速率最高达403t/(km~2·年),通过海带养殖,该示范区一年总共可吸收碳(C)31 200 kg,吸收氮(N)2130 kg,吸收磷(P)300 kg。本研究说明海带具有一定的生物修复与固碳能力,可为建立鱼藻生态复合养殖系统提供参考。     

长牡蛎夏季死亡与养殖环境及自身体质关系的初步研究

选取桑沟湾和爱连湾两个典型牡蛎养殖区为研究对象,调查了两个海区高温季节牡蛎的死亡情况,监测了不同养殖区的水温、盐度、pH和DO等环境指标,并测定了牡蛎体内超氧化物歧化酶(SOD)活性和生长指标的差异,初步探讨了桑沟湾养殖长牡蛎夏季高温死亡的原因。结果表明,实验期间(5～10月)桑沟湾崖头养殖海区(E122.498,N37.151)长牡蛎夏季累积死亡率为37%,最高死亡率出现在8月17日,高达51%,而爱连湾养殖海区(E122.582,N37.179)的累积死亡率仅为2.5%,最高死亡率出现在9月28日,为4.5%。单因子方差分析(ANOVA)表明死亡率与水温具有很强的正相关(R=0.804,P0.01),与溶氧呈明显负相关(R=-0.377,P0.01);死亡率与体重、软体湿重、性腺湿重等生长状况指标呈明显的负相关(R分别为-0.690、-0.498、-0.358),与SOD活性呈正相关(R=0.21,P0.05)。     

夏季桑沟湾养殖水域有机碳的平面分布特征及其来源分析

根据2012年8月对桑沟湾养殖海域18个站位取得的溶解有机碳(DOC)、颗粒有机碳(POC)和叶绿素a(Chl-a)数据,基于不同区域的养殖特点,分析了DOC和POC的平面分布特征,并对POC的来源进行了初步探讨。结果表明,整个调查海域表层DOC的浓度范围为1.70～2.82mg/L,平均值为2.03mg/L,大致呈自西向东递减的趋势。表层POC的浓度范围为0.04～1.33mg/L,平均值为0.55mg/L,大致呈自南向北逐渐递增的趋势。网箱养殖区表层DOC和POC含量最高,其次为桑沟湾近岸海域,而海带养殖区最低,这表明有机碳的含量与养殖品种和模式有直接的关系。根据POC/Chl-a比值对POC来源进行初步分析,表明贝类养殖区、海带养殖区、贝藻混养区、桑沟湾近岸海域以及外海对照点的POC主要来自活的浮游植物,而网箱养殖区存在降解的有机物质。     

桑沟湾养殖海带生长的模型预测

海带(Saccharinajaponica)是一种常见的大型经济褐藻,是海洋生态系统重要的初级生产者,也是我国北方沿海主要的养殖藻类。本研究旨在建立海带个体生长数值模型,并以此预测中国北方近海大规模筏式养殖条件下海带的生长情况。本研究以桑沟湾养殖海带为例,利用可视化模型软件STELLA描述海带生长的关键过程及其与环境参数的关系,以净生长量(N_(growth))=总生长量(G_(growth))–呼吸作用(resp)–枯烂(E_(kelp))为基本框架,模拟和预测海带的生物量和叶片长度变化。海带的总生长用光照、温度、盐度、海带体内营养盐(包括N和P)等强制函数定义,其中,光照参数来自桑沟湾气象记录,盐度、温度和营养盐为现场调查实测值。模型模拟桑沟湾养殖海带的长度与干重结果与实测值的拟合度R~2值分别为0.936、0.963,说明该模型能够很好反映海带的真实生长情况。可靠的个体生长模型是评估海带养殖容量的基础,并可为水产养殖区的空间规划提供决策依据。     

海水鱼类网箱养殖水域沉积物有机质的来源甄别

利用稳定碳氮同位素示踪技术,对南沙港网箱养殖水域沉积物中有机质的来源进行了分析研究。结果表明,网箱养殖区(距离网箱边缘100 m范围内)及对照区(距离网箱边缘大于500 m)沉积物的δ13C值分别为(-17.72±1.2)‰和(-12.73±0.38)‰,δ15N分别为(6.44±0.2)‰和(5.61±0.2)‰。网箱养殖区沉积物的有机质来源主要为残饵和鱼类粪便,比例分别占47.70%和27.71%。随着与养殖网箱距离的增加,网箱养殖源有机质(残饵和鱼类粪便之和)的比例降低,变化趋势符合指数方程y=97.167e-0.007 4x(R2=0.848 1),在潮流驱动的沉积物再悬浮及野生鱼类的扰动影响下,网箱养殖源有机质的水平位移可达400 m。鱼类网箱养殖的养殖废物是南沙港水域沉积物有机污染的主要来源。     

桑沟湾海带标准化养殖模式的优势探析

针对桑沟湾养殖海区海带(Laminaria japonica)的超容量养殖现象，研究了该海区中标准化养殖模式和传统养殖模式的海带生长差异。结果显示，在标准化养殖模式下，海带长、宽、平均厚度、湿重、投影面积和特定生长率均高于传统养殖模式，单棵海带重量显著提高，且海带的碳、氮和蛋白质含量明显高于传统养殖模式，海带品质大大提升。养殖后期，标准化养殖海区养殖海带垂直投影面积之和与对应养殖海区面积之比为6.33，而传统养殖模式的比值为9.15；标准化养殖海区海带所处水层下方的光照强度显著高于传统养殖区，海带所处水层的海流流速也高于传统养殖区。研究表明，桑沟湾海带标准化养殖模式使海带养殖密度降低，海带生长速度和品质均得以提高；在标准化养殖模式下，海带重叠较小，接受的光照比传统养殖模式充足；较快的海流使标准化养殖海区营养盐更新速度更快，这两方面可能是导致2种养殖模式下海带生长和品质产生差异的原因。     

海水养殖贝类体中TPH和PCBs的分布和积累研究

根据2005年4月和10月对厦门海域贝类养殖区养殖贝类体中有毒有害物质含量的调查资料,对4种养殖贝类(僧帽牡蛎、菲律宾蛤仔、泥蚶和缢蛏)体中石油类(TPH)和多氯联苯(PCBs)含量的分布和积累特征进行了研究。结果表明,厦门海域4种养殖贝类体中TPH和PCBs含量范围分别为(2·89~34·6)mg/kg,湿重和(5·06~45·7)μg/kg,湿重,总平均值分别为12·3mg/kg,湿重和15·5μg/kg,湿重。总体上,养殖贝类体TPH和PCBs含量的区域分布,潮间带养殖贝类>浅海养殖贝类>虾池养殖贝类,呈西海域和同安湾内较高,大嶝海域较低的格局。养殖贝类体TPH和PCBs含量季节变化呈春季(4月)高于秋季(10月)之势。养殖贝类体内组织对TPH和PCBs吸收和积累能力的高低为胃(包括胃含物)>肌肉组织>外套腔液。缢蛏体对TPH的吸收和积累能力较强,泥蚶对PCBs吸收和积累能力较强。这与其自身对TPH和PCBs的吸收和排泄能力有密切的关系。厦门海域养殖贝类受到PCBs轻度污染,一些养殖区的缢蛏、泥蚶和僧帽牡蛎受到TPH的不同程度污染。     

象山港中部养殖海区营养盐的季节变化及富营养化

根据2014年11月，2015年1月、3月和7月在象山港中部养殖海区开展的海洋调查所获得的海水营养盐数据，分析了该海域营养盐含量的季节变化，评价了海水的富营养化状况。结果显示，该海域无机氮平均含量秋季最高，春季次之，冬季最低；活性磷酸盐平均含量秋季最高，夏季次之，冬季最低。对不同养殖区域分析，宁海海藻养殖区和西沪港海带养殖区的无机氮浓度除冬季1个站位点外均劣于国家海水四类水质标准(0.50 mg/L)，活性磷酸盐浓度在春、秋两季劣于国家海水四类水质标准(0.045 mg/L)。全年各水层的N/P比值均高于Redfield比值，磷相对缺乏。根据富营养化评价模式，象山港中部养殖海区营养水平属于磷中等限制潜在性富营养型。     

三都湾网箱鱼类养殖容量的估算

以底质硫化物为指标,采样实地调查估算法,估算福建宁德三都湾网箱鱼类养殖容量。选取的5片网箱养殖区底质硫化物调查结果,每片网箱养殖区底质硫化物的含量从网箱养殖区的中心向边缘递减,网箱养殖区外侧硫化物含量均没有超标;利用SPSS软件的双变量相关性分析功能,分析底质硫化物与单位水体养殖密度之间的相关关系,得到指数增长曲线方程:y=81.858e1.214x,经相关性分析,得到R=0.989,R2=0.977,p0.01(n=6),相关性显著。根据该方程和底质硫化物评价标准,计算得出三都湾网箱适养水域的鱼类养殖容量为1.07kg/m3。     

水产养殖对亚热带海湾氮磷营养盐时空分布的影响——以深澳湾为例

文章对典型的亚热带养殖海湾——深澳湾海水中无机氮(DIN)、磷酸盐(PO_4-P)浓度的时空变化特征进行了分析,研究了鱼类网箱和贝藻筏式等规模化养殖活动对营养盐时空分布特征的影响,并对营养盐的潜在限制性进行了探讨。结果显示,深澳湾DIN和PO_4-P浓度及分布呈明显的季节变化:DIN在秋季最高,夏季最低;PO_4-P在冬季最高,夏季最低。春季网箱区的DIN浓度和氮磷比(N/P)低于贝藻养殖区和对照区,而其他3个季节,网箱区的DIN和PO_4-P浓度以及N/P均高于贝藻养殖区和对照区。贝藻养殖区和对照区之间在各个季节,氮、磷营养盐和N/P之间均无显著差异。各个季节DIN和PO_4-P浓度均高于理论上浮游植物生长的营养盐阈值,不存在营养盐的绝对限制。夏、冬季的N/P分别为13.6、13.1,低于Redfield值,说明存在N的潜在限制;春、秋季的N/P分别为16.6、19.0,说明P的潜在限制性较强。深澳湾的年均N/P为14.3,全湾受N潜在限制性较强。除夏季外,硝酸盐(NO_3-N)是DIN的主要组成,比例介于51.7%～92.7%,其次为NH_4-N (5.2%～43.8%),亚硝酸盐(NO_2-N)比例最低(2.1%～27.2%),说明深澳湾的氮营养盐达到了热力学平衡状态。与2001年相比,深澳湾海区的DIN和PO_4-P浓度均有下降,由中度营养型转变成贫营养型,年平均N/P更接近Redfield值,说明深澳湾的生产力水平依然受氮限制,营养盐的时空分布特征一定程度上体现了规模化贝藻养殖的影响。     

烟台四十里湾浅海养殖生物及附着生物的化学组成、有机净生产量及其生态效应

对四十里湾养殖海区一些双壳贝类和藻类收获时的化学组成和有机净生产量进行了分析，不同双壳贝类软体有机碳含量差别不大，而N含量差异较大，栉孔扇贝软体N含量最高（12．36％），而牡蛎，毛坩相对较低（8％－9％），贻贝和菲律宾蛤仔贝壳N含量最高，为0．55％和0．56％，而栉孔扇贝壳则较低（0．1％），且贝壳，C，N，P在扇贝C，N，P总含量中所占的比例分别为6．2％，7．5％和6．9％，海带和石莼元素组成说明海区营养元素N的不足，海带的不同部位N含量差别很大，且在不同海区有较大变化，贻贝贝壳C，H，N和P含量在整个贻贝中占有相对大的比例，分别为30．4％，30．2％，31．8％，29．6％，菲律宾蛤仔，长牡蛎和中国蛤蜊等贝类贝壳中这些元素的相对含量也较高，布扇贝贝壳却较低，四十里湾海区每年因贝类和藻类的养殖，海区将至少减少850tN和78tP，其中贝壳的营养损失占据着相当比例，在海水交换受到一定限制，营养不很丰富，海区，养殖生物收获本身也会对海区的营养状况产生影响，根据贝壳N，P的含量，笔者认为在营养不很丰富的沿岸海区，贻贝，牡蛎最好不养或尽可能少养。     

Effect of dietary protein and energy levels on growth,oxygen consumption,haemolymph and digestive gland carbohydrates,nitrogen excretion and osmotic pressure of Litopenaeus vannamei (Boone) and L. setiferus (Linne) juveniles (Crustacea,Decapoda; Penaeidae)

The influence of protein and energy levels on growth rate, survival, pre- and post-prandial oxygen consumption, ammonia excretion, haemolymph glucose (HG), glycogen in digestive gland and osmotic pressure (OP) in white shrimp Litopenaeus vannamei (Boone) and L. setiferus (Linne) juveniles was studied. Diets containing a high-quality protein at a protein/energy (P/E) ratio of 16, 26, 31 and 36 mg kJ⁻¹ were fed at 20% of shrimp body weight of two sizes: < 1 g and > 1 g. Both species showed a optimum P/E ratio of 36 mg kJ⁻¹ (33–44% protein and 6–23% carbohydrate) in juveniles < 1 g. For shrimp > 1 g, L. setiferus showed a higher growth rate in the diet with 16 mg kJ⁻¹ (27% protein; 32% carbohydrate) and L. vannamei between 26 and 36 mg kJ⁻¹ (33–44% protein and 6–23% carbohydrate). In both experiments, the growth rate of L. vannamei was 2–3 times that observed in L. setiferus. Routine oxygen consumption and apparent heat increment (AHI) of L. setiferus juveniles was two times higher than that observed in L. vannamei juveniles, which could indicate that L. setiferus has a higher metabolic rate. The O/N ratio varied according to protein level, with higher values (O/N = 180) with a 16-mg kJ⁻¹ diet and lower values (O/N = 73) with a 36-mg kJ⁻¹ diet in L. setiferus juveniles. A similar variation in O/N ratio was obtained in L. vannamei fed with all diets with an interval between 22 and 50. An inverse relation between ammonia excretion and HG, and digestive gland glycogen (DGG) in relation to an increase in the P/E ratio indicate that both shrimp species are well adapted to use carbohydrates and/or proteins from their diet. The higher values of hyper-osmotic capacity (hyper-OC) were observed in L. setiferus < 1 g fed with 36 mg kJ⁻¹ and the lowest in L. vannamei < 1 g fed with 31 mg kJ⁻¹. Intermediate values of hyper-OC were observed in both species fed all diets indicating that osmotic factors of juveniles < 1 g of both species are more affected by the P/E ratio than juveniles > 1 g. All results showed that juveniles > 1 g of both species are less dependent of P/E ratio than juveniles < 1 g. Litopenaeus vannamei is a most tolerant shrimp species with a high capacity to use a wide range of dietary P/E ratios for growth, which may be due to its lower energy requirements. Litopenaeus setiferus showed a lower capacity to accept different P/E ratios but the optimum P/E ratio obtained with this species shows that L. setiferus accept diets with a high carbohydrate level as well. These results demonstrate that there are nutritional and physiological differences that explain the differences that have been observed when both species were cultured in commercial ponds.     

Effects of lining and drying on the chemical composition of sediments and influence of organic carbon on carp growth in aquaculture ponds

Chemical characteristics and P‐fractionation of sediments from the Deroua fish culture farm (Beni Mellal, Morocco) were analysed in 1998 and 1999. The high concentrations of organic N and organic C in the sediments reflect the high productivity of phytoplankton in the lined ponds. Despite the fact that these ponds were not frequently fertilized, inorganic P was more important in the sediments. The P released from CaCO₃≈P was the principal source of P for phytoplankton. The mineralization rate of organic C during the drying period was about 87 µg g^?1 day^?1 in the sediments. The mineralization rate of organic N seems to be less, compared with organic C. The experimental results indicate that the C:N ratio and texture of sediments could explain the immobilization of organic N. All forms of P remained almost unchanged after the drying period except for Fe(OOH)≈P. The ferric (oxy) hydroxides protect NaOH_ext‐P from the bacterial lyses and stabilize therefore their concentration. The inorganic P represented about 88% of Total P in the sediments and may influence the mineralization rate of organic P. The growth of silver carp were reduced in presence of high concentrations of organic C in sediments (> 30 mg/g). Compounds toxic to fish such as Fe²⁺, Mn²⁺, H₂S and CH₄ were then released in the water column.     

Oxygen consumption and ammonia excretion of common wolffish Anarhichas lupus Linnaeus 1758 in an experimental-scale, seawater, land-based culture system

The oxygen consumption (0₂) and ammonia excretion (N) of juvenile and adult common wolffish was measured in culture tanks in the laboratory. The oxygen consumption and ammonia excretion were affected by temperature (C), fish size and feeding rate. For juveniles (0.5 kg; 7C) the diel oxygen consumption rate varied between 37 and 62 mg O₂ kg^-1 h^-1 and ammonia excretion between 2.3 and 5.7 mg N kg^-1 h^-1. The corresponding rates for adult fish (6.9 kg; 7C) were 29-44 mg O₂ kg^-1 h^-1 and 1.2–3.1 mg N kg^-1 h^-1. The weight-specific oxygen consumption (mg O₂ kg^-1 h^-1) was described by the following formulae: O₂ (7C) = 0.17* W^0.83 and O₂ (12C) = 0.39 * W^0.73 and the corresponding ammonia excretion (mg N kg^-1 h^-1) by: N(7C) = 0.024 W^0.75 and N(12C) = 0.073 W^0.60, where W is fish weight in g.     

Dietary protein level and C/N ratio manipulation in zero‐exchange culture of Litopenaeus vannamei: Evaluation of inorganic nitrogen control,biofloc composition and shrimp performance

A 30‐day experiment was conducted to evaluate inorganic nitrogen control, biofloc composition and shrimp performance in zero‐exchange culture tanks for juvenile L. vannamei offered a 35% (P35) or 25% (P25) crude protein feed, each feed supplemented with additional carbohydrate to increase the C/N ratio to 20:1 (CN20) or 15:1 (CN15). Sucrose was used as a carbohydrate to manipulate the two C/N ratios based on the carbon and nitrogen content of both the feeds and sucrose. The four treatments were referred to as: P35 + CN20, P35 + CN15, P25 + CN20 and P25 + CN15. Each treatment consisted of four replicate tanks (125 L), each stocked with 28 shrimp (equivalent to 224 shrimp m^?3). Bioflocs formed and developed based on initial inoculation in all four treatments; and monitored water quality parameters were maintained within acceptable ranges for shrimp culture throughout the experiment. No significant effects (P > 0.05) of dietary protein level, C/N ratio or their interaction were observed on biofloc development (BFV, TSS and BFVI) and inorganic nitrogen (TAN, NO₂^?‐N and NO₃^?‐N) concentrations. At the end of the experiment, proximate analysis of the bioflocs collected from the four treatments showed crude protein levels of 21.3% ~ 32.1%, crude lipid levels of 1.6% ~ 2.8% and ash levels of 43.4% ~ 61.4%. Extracellular protease and amylase activities of the bioflocs were 9.9 ~ 14.4 U g^?1 TSS and 293.5 ~ 403.8 U g^?1 TSS respectively. Biofloc composition and enzyme activity were both affected by dietary protein level (P < 0.01) and C/N ratio (P < 0.05). Survival, per cent weight gain and protein efficiency ratio of shrimp were not affected (P > 0.05) by dietary protein level, C/N ratio or their interaction; however, the feed conversion ratios were significantly lower (P < 0.05) in treatments with high dietary protein (P35) compared with those in treatments with low dietary protein (P25). The results from this study demonstrate that dietary protein level and C/N ratio manipulation can have important implications for water quality, biofloc composition and shrimp performance in intensive, zero‐exchange biofloc‐based culture systems.     

Assessment of different ionic adjustment strategies in low-salinity water on the growth of Litopenaeus vannamei and microbial community stoichiometry in a synbiotic nursery system

The aim of this study was to evaluate different ionic adjustment strategies in oligohaline water on the growth of Litopenaeus vannamei and C:N:P stoichiometric ratios of the floc microbial community (MC) in synbiotic nursery system. A 35-day culture (2000 PL's/m³) was carried out in 60 L units in a completely randomized experimental design, with three treatments: T1—seawater diluted to a salinity of 2.5 g/L (control), T2—water with a salinity of 2.5 g/L with potassium (K?) adjusted and T3—water at a salinity of 2.5 g/L with its Ca:Mg:K ratio adjusted to 1:3:1, each treatment in triplicates. The MC of flocs and the dissolved fraction (DF) was separated by filtration, where MC >1.6 µm and DF <1.6 µm. The juveniles reached a final weight of 0.40 ± 0.09–0.49 ± 0.04 g, survival above 80% and an average yield of 0.69 ± 0.18–0.81 ± 0.02 kg/m³, without significant differences among the treatments. A stabilizing trend of C:P, C:N and N:P ratios of MC was observed considering the variations of C:N:P in the DF, indicating a homeostatic behaviour of the floc MC, as occurs in systems with high nutrient availability. Our results indicate that the major ions initial concentrations (Ca²⁺: 25.07 mg/L, Mg²⁺: 89.75 mg/L and K?: 25.00 mg/L), total alkalinity 100.00 mg/L and total hardness 433.30 mg/L provide conditions that do not limit shrimp growth in oligohaline water synbiotic nursery system.     

桑沟湾春季有色溶解有机物(CDOM)吸收光谱特性及空间分布特征

有色溶解有机物(CDOM)是水生态系统中碳的重要来源,其光学性质可示踪海水中溶解有机物组分的动态信息。利用紫外可见吸收光谱手段,分区域测定了桑沟湾春季水体及表层沉积物间隙水中CDOM的吸收光谱特征,探讨了CDOM的来源组成、空间分布特征、迁移转化过程及其与养殖活动的关系。结果表明,(1)波长为355_的吸收系数(a(355))范围为0.23~9.09 /m,不同水层空间分布差异显著,表层和底层均从近岸区向贝藻区逐渐降低,之后在海带区升高后向外海逐渐降低；海带区从表层向底层先降低后升高,高密度、规模化的海带养殖释放了大量的CDOM,各区域沉积物间隙水a(355)是其表中底之和的1.3~2.5倍,CDOM在沉积物间隙水中富集并逐渐累积。(2)光谱斜率(S_275-295)范围为0.013~0.036,外海区和海带区S_275-295均值显著高于其他各区,海带区和外海区CDOM中海源有机质占主要成分,而近岸区以陆源有机质为主；近岸区CDOM中的腐殖酸类物质含量从表层到底层逐渐降低,沉积物中积累的富里酸类物质含量较高,海带区和外海区呈相反趋势。(3)比紫外吸光度(SUVA₂₅₄)范围为4.60~14.10 L/(mg.m),贝类区、贝藻区和藻类区SUVA₂₅₄均呈现出从表层到底层逐渐增大的趋势,CDOM的芳香性逐渐增强并在沉积物间隙水中达到最大；海带区和外海区沉积物间隙水中的SUVA₂₅₄显著高于其他各区,表明海带区的规模化养殖活动向养殖海区及邻近海域贡献了较多的惰性溶解有机物,暗示着海带养殖活动有较强的碳汇效应并通过海流作用向外海输送。     

水生植物分解过程中生态化学计量学特征

为揭示水生植物分解过程中的生态化学计量学特征，选取沉水植物苦草（Vallisneria natans）和马来眼子菜（Potamogeton malaianus）以及漂浮植物浮萍（Lemna minor），分别置于温室（处理组A、B）和池塘中（处理组B），实验周期为5周，每隔1周随机从各重复组中取1份样品，测定干物质重和总氮（TN）、总碳（TC）、总磷（TP）含量，分析其残存干物质的分解过程。结果表明，在整个分解过程中，3种植物的C/N为7.43~10.06，低于全球水平22.5，C/P为43.09~91.77，明显高于全球水平23.2，说明同一种植物在相同的同化C能力前提下，对N的利用效率较高，对P的利用率较低；N/P为4.71~9.24，小于14，说明植物主要受N的限制。沉水植物苦草和马来眼子菜的C/N在温室和自然条件下规律一致，而漂浮植物浮萍则变化较大，说明沉水植物分解C和N的速率一致且不受环境影响，而漂浮植物浮萍分解C和N受环境影响较大；苦草和浮萍残存干物质C/N在开始有一个快速增长期，说明这2种植物N的释放速率超过C；3种植物残存干物质的C/P和N/P都在第1周快速增长且各处理变化较大，说明3种植物P分解速率都在1周内超过C和N，且受环境影响较大。研究结果将对水生态修复过程中是否移除残存水生植物提供理论依据。     

Effect of dietary protein, lipid and carbohydrate ratio on growth, feed efficiency and body composition of pikeperch Sander lucioperca fingerlings

Pikeperch Sander lucioperca fingerlings were fed nine practical diets containing three levels of protein (P=34%, 43% and 50%), lipid (L=10%, 16% and 22%) and carbohydrate (C=10%, 15% and 20%) for 10 weeks in a recirculating water system at 23°C. Dietary treatments were distributed by orthogonal design with dietary energy content ranging from 15.5 to 23.1 MJ kg^?1 diet. Significant differences (P<0.05) in weight gain (%) and feed efficiency (FE) were observed after feeding trial. Relatively low growth and FE were found in fish fed diets containing 34% dietary protein level compared with that of fish fed diets with 43–50% protein levels, suggesting that 34% dietary protein probably is below the protein requirements of pikeperch fingerlings. Fish fed diets containing P43L10C15, P43L22C20 and P50L16C20 had significantly (P<0.05) higher weight gain and FE than fish fed the diets containing other dietary P/L/C ratios. There was no significant difference in weight gain and FE between fish fed diets of P43L10C15, P43L22C20 and P50L16C20. These results may indicate that pikeperch require at least 43% of dietary protein for adequate growth and FE, and considering the fish growth and feed ingredient cost P43L10C15 diet is more cost‐effective formulation for pikeperch fingerling. However, protein efficiency was not significantly affected by dietary P/L/C ratio.     

Short-Term Dinoflagellate Bloom in a Shrimp Pond in Bahía de La Paz,Gulf of California

From mid-August to mid-September 1998, a dinoflagellate bloom in a shrimp pond near La Paz, Baja California Sur, was studied. Daily samples were taken of phytoplankton, dissolved oxygen, nutrient concentrations, photosynthetic pigments and proteins. The bloom occurred at temperatures of 29.7 to 33.2?°C. High densities of a Scrippsiella-like dinoflagellate (15.9?×?10⁶ cells/L) occurred on the first day of sampling, reaching a peak of 249?×?10⁶ cells/L on Day 13, and declining to 4 to 7?×?10⁶ cells/L by Day 26. Chlorophyll a varied from 8.63 mg/m³ on Day 4 to 141.38 mg/m³ on Day 13. Total nitrogen varied widely (0.2–11.50 μM) while phosphates peaked only once on Day 13 (4.14 μM). Proteins ranged from 523 to 6387 μg/L; the latter value occurred two days after the maximal peak of nitrates and coinciding with the highest level of phosphates. Fertilizers added to the ponds increased nutrient concentration and stimulated phytoplankton growth. In turn, the food supply to cultured shrimp noticeably increased throughout the bloom.