An improved technique for preparing eel otoliths for aging

The New Zealand Waters Pollution Regulations 1963, referring to recreational water to which the public can gain access, states that the “coliform bacteria content shall not consistently exceed 1,000/100 ml”. This standard is now under revision, and the suggested new standard is a median faecal coliform index of 200/100 ml with a maximum value not exceeding 400/100 ml.

Recent literature supports the use of faecal coliform sub‐group bacteria as the best indicator of faecal pollution and reference is made to the membership of this sub‐group. Inherent inaccuracies of the Most Probable Number (MPN) method of assessing bacterial populations are pointed out, such as experimental variations with different cultural media, and possible errors in interpretation of results. In North America, there is evidence that an MPN for the total coliform group of 1000/100 ml indicates a faecal coliform sub‐group MPN of 200/100 ml, and epidemiological experience supports these values as standards.

We tabulate and discuss evidence that the usual ratio of faecal coliforms : coliform group bacteria is typically 1 : 1 in fresh and marine waters of the Wellington region, and that a more attainable standard would be 500 faecal coliforms/100 ml. In ratios quoted in this paper, ‘coliform group’ means the remainder of the coliform group excluding faecal coliforms. The World Health Organisation (1963) definition, of the entire group of coliforms, is not intended. The ratio is different in other parts of New Zealand; in Auckland, for example, the ratio is close to that found in the United States.     

胶州湾大肠菌群丰度变化及对环境污染的指示

采用MPN计数法对胶州湾大肠菌群丰度进行7年（84个月）连续监测,结果表明,大肠菌群丰度的周年变化明显,全年最高丰度与最低丰度相差约2.2倍。胶州湾大肠菌群丰度自2005—2009年明显下降,降幅达67%,说明胶州湾环境质量有所好转。研究还发现大肠菌群丰度变化具有明显的区域特征,河口区最高,湾内区最低,差异近11倍。大...     

Comparison of procedure for fecal coliform enumeration in coastal waters

INTRODUCTION Fecal coliform has been used as an indicator of water pollution for about a century. Recently, Standrige et al (1981), Reasoner et al (1979) and Pagel et al. (1982) improved, with good results, the bioassy methods for fecal coliform in drinking water and waste water. To provide a method appli-     

Factors affecting the accumulation and elimination of silver (110mAg) in marine isopods

The bioaccumulation and elimination of silver-110 m was investigated in Idothea primastica. The retention of ^110mAg in the fecal pellets of Idothea was also investigated. The concentation factor was found to be relatively high (> 10³) at equilibrium and the bioaccumulation process was independent of temperature at 10°C and 20°C. It was also found that neither the loss rate from the animals nor the loss rate from fecal pellets were influenced by temperature. However, the loss rate from fecal pellets was significantly greater than that from whole animals. The retention half-times were found to be 130 days for the fecal pellets and 231 days for the animals. The loss rate of ^110mAg was higher in seawater than in brackish water.     

Water quality of a lowland stream in a New Zealand dairy farming catchment

A small stream in a predominantly dairying catchment in the Waikato region of New Zealand was monitored for 2 years at three sites. Total nitrogen (TN) concentrations were up to 7.09 g m^‐3 in winter, with the bulk comprising nitrate nitrogen (NO^‐ ₃‐N). During summer NO^‐ ₃‐N was near zero and TN mostly comprised organic nitrogen. Maximum concentrations of total phosphorus (TP) and dissolved reactive phosphorus (DRP) were 1.64 and 0.555 g m^‐3, respectively, and peaks coincided with spring and autumn applications of phosphorus fertiliser. Ammoniacal nitrogen concentrations exceeded 1 g m^‐3 on several occasions and mean concentrations at the three sites were 0.165–0.272 g m^‐3. Faecal coliform and enterococci bacteria concentrations were 64–26000 and 7–23000 cfu per 100 ml, respectively. Specific yields of TN and NO^‐ ₃‐N (35.3 and 30.7 kg ha yr^‐1, respectively) were much greater than any previously reported for New Zealand pasture catchments, whereas TP and DRP yields (1.16 and 0.54 kg ha yr^‐1, respectively) were more in accord with other studies. Greater use of land treatment of liquid wastes will reduce stream inputs of faecal organisms, NH₄‐N and P.     

2016年秋季热带西太平洋网采浮游植物群落结构

作者于2016年9月27日～10月25日对热带西太平洋(0°～20°N, 120°～130°E)10个站位的网采浮游植物群落结构进行了采样调查。应用Uterm?hl方法对调查海域浮游植物的物种组成、细胞丰度、优势物种以及群落多样性等相关生态特征进行了分析。希望为热带西太平洋提供一些基础的背景资料,为以后的研究奠定基础。结果表明, 鉴定出浮游植物共计4门、66属、243种(包括变种、变型), 含硅藻门(Bacillariophyta)34属、103种, 甲藻门(Pyrrophyta)28属、133种, 金藻门(Chrysophyta)2属、4种,蓝藻门(Cyanophyta)2属、3种。浮游植物细胞丰度1 965.573×10³ 细胞/m³ , 其中蓝藻的细胞丰度为1 945.169×10³ 细胞/m³ , 决定了浮游植物的分布格局, 占总细胞丰度的98.96%, 高值区分布在0°N130°E-10°N130°E的4个站位(E130-13、E130-15、E130-17、E130-19); 硅藻丰度在20°N断面N20-4站位存在高值区; 甲藻丰度在130°E断面的3个站位(E130-10、E130-13、E130-15)存在高值区。本次调查的优势种依次为铁氏束毛藻(Trichodesmium thiebaultii)、扁形原甲藻(Prorocentrum compressum)、扁豆原甲藻(Prorocentrum leniculatum)、胞内植生藻(Richelia intracellularis)、菱形海线藻(Thalassionema nitzschioides)、细弱海链藻(Thalassiosira subtilis)、具边线形圆筛藻(Coscinodiscus marginato-lineatus)、科氏角藻(Ceratium kofoidii)、鲁比膝沟藻(Gonyaulax lurbynaii)、中华半管藻(Hemiaulus sinensis)、霍氏半管藻(Hemiaulus hauckii)、小等刺硅鞭藻(Dictyocha fibula)。Shannon-Weiner多样性指数的均值为2.440,Pielou 均匀度指数的均值为0.163。相关分析结果显示浮游植物空间分布主要受PO₄-P、NH₄-N的影响,且由蓝藻的相关性决定的。聚类分析得出群落结构分为大洋群聚和近岸群聚两种类型(其中大洋群聚的站位又划分为0°～10°N纬度范围聚集和10°～20°N纬度范围聚集)。     

深圳海域弧菌种类组成、数量分布及其与环境因子的关系研究

研究了深圳海域2008年4月、9月的水体弧菌数量、种类组成及其分布,探讨了弧菌总数及各优势类群的数量分布与环境因子间的相关关系。结果表明:弧菌总数分布具有季节性,东部海域春季(4月)的弧菌数量高于秋季(9月)的,其均值分别为1.50×104,8.89×102CFU/cm3;在西部海域秋季的略高于春季的,其均值分别为5.09×102,2.66×102CFU/cm3;弧菌数量最高值出现在大亚湾(4.40×104CFU/cm3)。弧菌的优势类群具有季节性分布特征:春季特有的优势类群有Vibrio gigantis类似种和V.splendidus类似种,秋季特有的优势类群有V.natriegens类似种;V.alginolyticus类似种是两个季节共有的优势类群,其数量春季高于秋季的。弧菌种类、数量与海水温度、盐度及细菌总数、Chl-a等环境因子有一定的相关性,其中盐度为弧菌种类及数量分布的主要影响因子。     

深圳海域弧菌种类组成、数量分布及其与环境因子的关系研究

研究了深圳海域2008年4月、9月的水体弧菌数量、种类组成及其分布,探讨了弧菌总数及各优势类群的数量分布与环境因子间的相关关系。结果表明:弧菌总数分布具有季节性,东部海域春季(4月)的弧菌数量高于秋季(9月)的,其均值分别为1.50×10⁴ ,8.89×10² CFU/cm³;在西部海域秋季的略高于春季的,其均值分别为5.09×10²,2.66×10² CFU/cm³;弧菌数量最高值出现在大亚湾(4.40×10⁴ CFU/cm³)。弧菌的优势类群具有季节性分布特征:春季特有的优势类群有Vibrio gigantis类似种和V. splendidus类似种,秋季特有的优势类群有V. natriegens类似种;V. alginolyticus类似种是两个季节共有的优势类群,其数量春季高于秋季的。弧菌种类、数量与海水温度、盐度及细菌总数、Chl-a等环境因子有一定的相关性,其中盐度为弧菌种类及数量分布的主要影响因子。     

Particle–water interactions of 2,2′,5,5′-tetrachlorobiphenyl under simulated estuarine conditions

A batch sorption technique for the determination of particle–water interactions of hydrophobic organic micropollutants under simulated estuarine conditions is described. Results are presented for the behaviour of 2,2′,5,5′-tetrachlorobiphenyl (2,2′,5,5′-TCB) in river and sea waters, both in the presence and absence of estuarine suspended particles. Adsorption onto particles in sea water was enhanced compared with adsorption in river water owing to salting out of the compound, and possibly of the particulate organic matter, in the presence of high concentrations of dissolved ions. The particle–water distribution coefficient, K_D, decreased from about 120×10³ to 10×10³ ml g⁻¹, and from about 150×10³ to 20×10³ ml g⁻¹, in river water and sea water, respectively, over a particle concentration range of 10–1000 mg l⁻¹. Incomplete recovery of compound from the reactor walls is partly responsible for a particle concentration effect, while artefacts relating to inadequate sediment and water phase separation were ruled out following further experiments. The particle concentration effect, which is replicated in many field studies of hydrophobic organic micropollutants, including 2,2′,5,5′-TCB, is incorporated into a simple partitioning model and is discussed in the context of the likely estuarine behaviour of such compounds.     

胶州湾微微型浮游植物丰度及其与环境因子的相关性分析

利用流式细胞仪对胶州湾微微型浮游植物4个季节的丰度分布进行了研究,并分析了微微型浮游植物与环境因子的相关性。结果表明,聚球藻的丰度在2.17×102—2.329×104个/ml之间,高值区主要分布在湾内西部和湾口海域;仅夏季、冬季丰度之间有显著性差异;夏季在垂直分布上差异显著,在B3、C4、D5连续站昼夜变化趋势基本一致,分别在13:00和3:00出现峰值。微微型真核浮游植物的丰度分布在1.028×103—8.651×104个/ml之间,主要活跃于湾内西部海域;四季丰度在垂直分布上差异不显著;春、夏季丰度明显高于秋、冬季;夏季连续站昼夜变化趋势与聚球藻基本一致。通过主成分分析表明,聚球藻和微微型真核浮游植物丰度在不同季节受不同环境因子的影响,在冬季与温度有关,温度升高,二者的丰度增高。在其它季节,二者丰度主要受营养盐等环境因子的影响。     

全国海水浴场及经济贝类中腺病毒的分布

为分析全国海水浴场、贝类增养殖区人类肠道腺病毒的污染状况,采用超滤浓缩方法,TaqMan探针实时定量PCR技术对其进行了定量。结果表明,全国10个海水浴场表层海水中腺病毒的阳性检出率为35%,含量为1.1×107~2.8×107 copies/L。在离岸100m和1 000m处腺病毒的分布无显著差别(p0.05);在调查的162份贝类样品中,腺病毒的阳性检出率为11.7%,含量为2.4×104~3.1×105 copies/g。6类经济贝类中牡蛎带病毒量最高。由此可见,全国范围内海水浴场表层海水和主要增养殖区经济贝类中腺病毒污染比较普遍,尤其以山东、辽宁和浙江三省最为严重,给洗浴者和消费者健康造成潜在威胁。人类肠道腺病毒可以很好地指示粪便污染,调查其在海水浴场和经济贝类中的分布,可以帮助公众预警胃肠道病毒的暴发流行,本研究为开展全国腺病毒的环境风险评估和分子流行病学调查奠定了良好的基础。     

赤潮异弯藻(Heterosigma akashiwo)对蒙古裸腹溞(Moina mongolica)和日本新糠虾(Neomysis japonica)的毒性影响

采用生物急性和慢性毒性实验的方法,研究了赤潮异弯藻对蒙古裸腹溞和日本新糠虾的毒性影响,并初步探讨了赤潮异弯藻导致二者较快死亡的机制。结果发现,赤潮异弯藻不仅对蒙古裸腹溞和日本新糠虾的存活有显著影响,而且使其个体变小、产幼前发育时间延长、总生殖量降低、平均存活时间缩短,种群数量增长受抑制。显微观察发现,蒙古裸腹溞能摄食赤潮异弯藻,但摄食后,其粪便紧紧地粘在蒙古裸腹溞的肠道末端;日本新糠虾不摄食赤潮异弯藻,但该藻粘附在其触须、附肢以及腹部、尾部的刚毛上,以及作为食物的卤虫幼体也被大量粘附在一起,聚集成团,或通过赤潮异弯藻粘附在日本新糠虾的附肢上。因此赤潮异弯藻很可能通过干扰蒙古裸腹溞和日本新糠虾正常的生理活动,而导致其快速死亡。     

Impacts of the wintertime mesozooplankton community to downward carbon flux in the subarctic and subtropical Pacific Oceans

We compared wintertime depth distributions of the mesozooplankton community and dominant copepods between the subtropical (S1) and subarctic (K2) Pacific Oceans to evaluate the relative importance of actively transported carbon by vertical migrants to sinking particulate organic carbon flux. Primary production was higher and the ratio of sinking particulate organic carbon flux to primary production was lower at S1 compared with those at K2. The mesozooplankton community was lower in abundance and biomass at S1 compared to K2. Copepods were the dominant group among both mesozooplankton abundance and biomass throughout the water column down to 1000 m at both sites. The depth distribution showed that diel vertical migration was obvious for the mesozooplankton abundance and biomass at S1 but was not apparent for the abundance at K2, because the dominant component was diurnally migrating species at S1 and overwintering species residing at mesopelagic depths at K2. The major components of diel migrants were copepods and euphausiids at S1 and only euphausiids at K2. Respiratory flux by the diurnally migrating mesozooplankton was estimated to be 2 mgC m⁻² day⁻¹ at S1 and 7 mgC m⁻² day⁻¹ at K2. The respiratory flux was equivalent to 131% of sedimentary fecal pellet flux at S1 and 136% of that at K2. Because pathways of downward carbon flux are facilitated by the mesozooplankton community, the actively transported carbon (respiration of dissolved inorganic carbon, excretion of dissolved organic carbon and egestion of fecal pellets at depth) might be larger during winter than the flux of sinking fecal pellets.     

多肽菌素在长牡蛎人工育苗生产中的应用

多肽菌素作为一类具有抗菌活性的生物短肽,是一种可以替代抗生素的生物肽。为了推广多肽菌素在水产养殖中的应用,本研究以长牡蛎(Crassostreagigas)人工育苗为基础,以添加2×10_–6 mol/L青霉素钠为对照组,以添加5个不同浓度(2×10_–6、4×10_–6、6×10_–6、8×10_–6、10×10_–6 mol/L)多肽菌素为实验组,研究多肽菌素在长牡蛎人工育苗生产中的应用。结果显示:(1)在长牡蛎种贝培育方面,培育前8天各组差异不显著(P> 0.05),培育后期添加6×10_–6 mol/L多肽菌素组存活率均最高,对照组最低,且培育至32天时该实验组均显著高于其他组(P<0.05)。(2)在长牡蛎幼虫培育方面,幼虫壳高日增长量在添加6×10_–6 mol/L多肽菌素组中最大,为11.57μm/d,而对照组仅为9.61μm/d;幼虫存活率方面对照组始终最低,而添加6×10_–6 ...     

Helium isotopes of seawater in the Japan Sea

We have collected fifty-five seawater samples at seven stations at various depths in the Yamato and Japan Basins of the Japan Sea and measured their helium isotopic ratios. The ³He/⁴He ratios vary from 0.997 R_atm to 1.085 R_atm where R_atm is the atmospheric ratio. The maximum ³He excesses about 8%, are observed at mid-depth (1000 m), and these values are significantly lower than those observed in deep Pacific waters. This implies that mantle-derived helium in deep Pacific water cannot enter the Japan Sea since it is an almost landlocked marginal sea. The observed 8% excess ³He may be attributable to the decay product of tritium. Slightly higher ³He/⁴He ratios in the Bottom Water were observed in the Yamato Basin than in the Japan Basin. The ventilation ages of seawater shallower than 1000 m are calculated as about 5 to 20 years, which is consistent with the CFC ages reported in the literature. There is a positive correlation between the apparent oxygen utilization and ³H-³He ages. The estimated oxygen utilization rate from the correlation in a layer between 500 m and 1000 m is about 3 μmol/kg/yr, which is similar to that in the eastern subtropical North Atlantic.     

The fate of production in the central Arctic Ocean - top-down regulation by zooplankton expatriates?

We estimated primary and bacterial production, mineral nutrients, suspended chlorophyll a (Chl), particulate organic carbon (POC) and nitrogen (PON), abundance of planktonic organisms, mesozooplankton fecal pellet production, and the vertical flux of organic particles of the central Arctic Ocean (Amundsen basin, 89-88° N) during a 3 week quasi-Lagrangian ice drift experiment at the peak of the productive season (August 2001). A visual estimate of ≈15% ice-free surface, plus numerous melt ponds on ice sheets, supported a planktonic particulate primary production of 50-150 mg C m⁻² d⁻¹ (mean 93 mg C m⁻² d⁻¹, n = 7), mostly confined to the upper 10 m of the nutrient replete water column. The surface mixed layer was separated from the rest of the water column by a strong halocline at 20 m depth. Phototrophic biomass was low, generally 0.03-0.3 mg Chl m⁻³ in the upper 20 m and <0.02 mg Chl m⁻³ below, dominated by various flagellates, dinoflagellates and diatoms. Bacterial abundance (typically 3.7-5.3 × 10⁵, mean 4.1 × 10⁵ cells ml⁻¹ in the upper 20 m and 1.3-3.7 × 10⁵, mean 1.9 × 10⁵ cells ml⁻¹ below) and Chl concentrations were closely correlated (r = 0.75). Mineral nutrients (3 μmol NO₃ l⁻¹, 0.45 μmol PO₄ l⁻¹, 4-5 μmol SiO₄ l⁻¹) were probably not limiting the primary production in the upper layer. Suspended POC concentration was ∼30-105 (mean 53) mg C m⁻³ and PON ∼5.4-14.9 (mean 8.2) mg N m⁻³ with no clear vertical trend. The vertical flux of POC in the upper 30-100 m water column was ∼37-92 (mean 55) mg C m⁻² d⁻¹ without clear decrease with depth, and was quite similar at the six investigated stations. The mesozooplankton biomass (≈2 g DW m⁻², mostly in the upper 50 m water column) was dominated by adult females of the large calanoid copepods Calanus hyperboreus and Calanus glacialis (≈1.6 g DW m⁻²). The grazing of these copepods (estimated via fecal pellet production rates) was ≈15 mg C m⁻² d⁻¹, being on the order of 3% and 20% of the expected food-saturated ingestion rates of C. hyperboreus and C. glacialis, respectively. The stage structure of these copepods, dominated by adult females, and their unsatisfied grazing capacity during peak productive period suggest allochthonous origin of these species from productive shelf areas, supported by their long life span and the prevailing surface currents in the Arctic Ocean. We propose that the grazing capacity of the expatriated mesozooplankton population would match the potential seasonal increase of primary production in the future decreased ice perspective, diminishing the likelihood of algal blooms.     

2006年冬季北黄海网采浮游植物群落结构

根据2006年12月30日—至2007年1月17日北黄海的调查资料,对该海域浮游植物的种类组成、优势种、丰度及其分布和多样性等基本状况进行了分析。本次调查共鉴定浮游植物4门68属131种,主要以温带近岸和广布性种为主,其中硅藻有53属113种,占总种数的86.3%,甲藻有11属16种,占总种数的12.2%。浮游植物丰度平均值为88.89×104个/m3,硅藻丰度平均值为86.58×104个/m3,甲藻丰度平均值为2.28×104个/m3,硅藻丰度分布趋势决定了浮游植物丰度的分布趋势。辽宁南岸是浮游植物密集区,山东半岛北岸其次,而北黄海中部是浮游植物的稀疏区。优势种为:短角弯角藻(Eucampia zodiacus)、具槽帕拉藻(Paralia sulcata)、尖刺拟菱形藻(Pseu-do-nitzschia pungens)、密连角毛藻(Chaetoceros densus)、柔弱角毛藻(Chaetoceros debilis)、刚毛根管藻(Rhizosolenia setigera)。浮游植物群落Shannon-Weiner物种多样性指数平均值为1.80,Peilou均匀度指数平均值为0.42。与1959年1月相比,2007年1月北黄海浮游植物丰度由150.00×104个/m3降为88.89×104个/m3,下降了近41%,硅藻丰度由148.00×104个/m3降为86.58×104个/m3,而甲藻丰度由1.25×104个/m3上升为2.28×104个/m3,占浮游植物丰度的比例由0.8%上升为2.5%。主要优势种及优势属也发生了一定程度的变化,但浮游植物群落结构仍以硅藻为主、甲藻其次,浮游植物丰度总的分布格局变化不明显。     

Ecological energetics of the tropical sea urchin Diadema antillarum Philippi in Barbados, West Indies

The common tropical sea urchin Diadema antillarum Philippi is the dominant herbivore on fringing coral reefs in Barbados, West Indies. The biological importance of Diadema as an agent of energy transfer was evaluated from energy budgets constructed for the population and for individuals of 10 size groups. Monthly energy budgets for urchins of various size groups balance within 1 kcal except for urchins of the largest size group examined. Approximately 20% of the monthly net benthic primary production of the fringing coral reef is consumed by Diadema. This percentage is considerably larger than the 7% reported for the consumption of benthic algal production by a population of the temperate water sea urchin, Strongylocentrotus droebachiensis, feeding in kelp beds but is lower than the 47% reported for the consumption of sea grass by the tropical urchin Lytechinus variegatus. Higher rates of secondary production of Diadema compared to that of Strongylocentrotus may be in part due to higher net and gross growth efficiencies exhibited by Diadema. It is apparent that Diadema is more efficient at converting its algal food resources into urchin biomass than is Strongylocentrotus of similar size. In comparison to Strongylocentrotus and Lytechinus, Diadema releases as much energy to the benthos in the form of fecal pellet detritus as do the other two species. The production of fecal pellet detritus is the most important pathway of energy transfer on the fringing coral reef. Fecal pellet detritus contributes approximately 26 kcal m⁻² month⁻¹ to the benthic community. This amount is equivalent to 7·4% of the monthly net primary production of the benthic algae or approximately 37% of the caloric intake of the urchin population. In addition fecal pellet detritus produced by Diadema contains about 10 times the caloric content of surface sediments found to the north and south of the fringing reef and approximately 1·7 times the caloric content of sediments within the reef. The utilization of this energy-rich fecal pellet detritus by other reef organisms is discussed briefly.     

Biogenic debris from the pelagic tunicate, Oikopleura dioica, and its role in the vertical transport of a transuranium element

The accumulation and retention of ²⁴¹Am by the pelagic tunicate Oikopleura dioica were examined using laboratory cultures and radiotracer methodology. Animals (i.e., trunks and tails) and discarded empty houses accumulated Am from seawater, giving volume/volume concentration factors of 59±8 and 10±1, respectively. The half-time for retention of Am in empty labelled houses transferred to non-contaminated seawater was 29 h; the retention half-time of Am in houses discarded by larvaceans feeding on Am-labelled diatoms was 219 h; the half-time of Am in fecal pellets produced by animals feeding on a monospecific diet of diatoms was 134 h, and 247 h for fecal pellets from animals fed a mixed diet. Approximately 30% of filtered cells remained in houses after the houses were discarded. Sinking rates of discarded houses and fecal pellets were found to vary with temperature and size, ranging from 26–157 m day^?1 (house) and from 25–166 m day^?1 (fecal pellets). The ubiquity and abundance of appendicularians, together with their prodigious production of houses (e.g., 10±2 houses day^?1 at 17°C for each experimental animal) point to their potential significance in the vertical transport of Am, and probably other reactive metals, to intermediate depths in the ocean.     

稀土对球等鞭金藻生长的影响

于１９９５年８－１２月,利用单因子实验法,首次研究了混合稀土对球等鞭金藻（Ｉｓｏｃｈｒｙｓｉｓｇａｌｂａｎａ）生长繁殖的影响,结果表明,海水中稀土最佳浓度范围为１．６６－６．６０ｍｇ／Ｌ,细胞浓度和叶绿素含量分别提高１１．６％－２３．２％和１９．９％－４５．２％混合稀土加入浓度高于９．９ｍｇ／Ｌ对球等鞭金藻的生产产生抑制作用,稀土对球等鞭金藻生长的促进作用与其他营养盐类浓度有关,当细胞处于指数生长