洪湖水体藻类藻相特征及其对生境的响应

藻类是水生态系统的重要成分,它的群落结构、细胞密度变化与水环境相适应,随水环境的变化而改变,因此藻相变化是评价水体质量的一项重要指标。2009—2010年在洪湖水面不同方位布点采样,对水体的浮游藻类藻相(群落结构、密度)和水质状况(水位(water level,H)、水温(water temperature,tw)、透明度(transparency,SD)、总氮(total nitrogen,TN)、总磷(totalphosphorus,TP)、高锰酸盐指数(permanganate index,CODMn)和叶绿素含量(chlorophyll a,Chl-a)等)进行了逐月的调查、监测,采用湖库营养状态指数法对湖泊富营养化评价,并运用多元逐步回归方法建立水体藻类与生境因子的回归方程。结果表明:洪湖水体总体上已达到轻度富营养化状态;藻类以蓝藻门、硅藻门和绿藻门为主,共鉴定出7门65属,藻细胞密度为1.14×106—3.24×107个/L,藻相季节变化特征明显。藻类组成以蓝藻门密度最高(52.93%),硅藻门(25.96%)和绿藻门(16.83%)次之,隐藻门(1.98%)、金藻门(1.64%)、裸藻门(0.42%)和甲藻门(0.25%)相对较低。藻类藻相及优势种在不同季节有所差异,冬春季节(12—5月)以硅藻门的直链藻、小环藻和针杆藻为优势种,夏秋季节(7—11月)以蓝藻门的鱼腥藻和微囊藻为优势种;湖泊藻类细胞密度与tw、CODMn呈正显著相关关系,与H、TN、TP、SD相关关系不显著;藻细胞生长逐步回归方程为y=3.7815+0.0794tw+0.5670CODMn-1.3467SD,藻细胞生长主要受水温和有机污染物等的影响,氮磷不是藻类生长的控制因子;在湖泊不同区域,环境条件存在差异,导致藻类生长过程中起主导作用的环境因子存在一定的差异,蓝藻生长主要受tw、CODMn和SD控制,绿藻生长主要受H、tw和CODMn影响,而硅藻生长决定于水体CODMn。     

城市小型浅水人工湖泊浮游藻类与水质特征研究

研究了广州城区某富营养化小型浅水人工湖泊浮游藻类和水质特征及其变化规律。根据镜检共鉴定出7门54属浮游藻类,以绿藻门、蓝藻门、硅藻门和裸藻门为主,其中绿藻门的绿球藻目占绝对优势,达26属62种,占总属数的45.6%;在整个观测期内,浮游藻类密度均较高,05年2月藻类密度高达10.8×106cell·mL-1;根据Kolkwitz划分的水域类型,该湖泊中浮游藻类属于α、β-中污带指示种类的最多。由以修正的卡森(Carlson)指数为基础的综合营养型评价方法和Margalef生物多样性指数判断,该湖泊水体属重富营养化水平,受到重污染,且污染水平季节变化明显:冬季>秋季>夏季。     

深圳石岩水库浮游植物群落时空动态特征及其影响因素分析

于2013 年5 月至2014 年4 月对深圳石岩水库进行采样, 研究了深圳石岩水库浮游植物群落组成、时空动态及其主要的环境影响因素, 以期为该水库水质的保障和改善提供科学依据。石岩水库全年共检测到浮游植物7 门90属, 以绿藻门(41.1%)、硅藻门(30.0%)和蓝藻门(20.0%)为主。浮游植物的种类在9 月份最丰富, 有61 种, 8 月份最少, 仅有18 种。各采样区的浮游植物丰度, 在6 月份达到最大值, 为1.76×108 cells·L^–1, 在10 月份出现最低值, 为2.74×106 cells·L^–1。绿藻、硅藻和蓝藻的丰度之和在全年所占比例都较高, 变化范围为96.74%-100%, 以蓝藻居多, 占51.55%-92.23%,其中, 绿藻门的优势属为十字藻属(Crucigenia)、栅藻属(Scenedesmus)、小球藻属(Chlorella); 硅藻门的优势属为直链藻属(Melosira)、小环藻属(Cyclotella); 蓝藻门的优势属为假鱼腥藻属(Pseudanabaena)。冗余分析(Redundancy analysis,RDA)表明: 全部样品分布在轴1 与轴2 构成的4 个象限内, 轴2 左侧与冬(春秋)季对应, 轴2 右侧与夏季对应; 绝大多数藻类分布在冬(春秋)季对应的象限内, 少数藻类包括硅藻门的卵形藻属(Cocconeis)、蓝藻门的平裂藻属(Merismopedia)、尖头藻属(Raphidiopsis)和鞘丝藻属(Lyngbya)以及绿藻门的衣藻属(Chlamydomonas)分布在夏季所对应的象限内; 研究结果表明影响石岩水库浮游植物群落结构动态的主要驱动因子是水温(Temperature, TEMP)、总有机碳 (Total Organic Carbon, TOC)、硝酸盐氮(NO3-N)和总氮(Total Nitrogen, TN)。     

黑河秦岭河段浮游植物群落结构研究

为研究黑河秦岭河段的浮游植物群落结构特征,于2009年8月至2010年3月对黑河秦岭河段4个采样断面的浮游植物进行了调查和分析。鉴定结果显示该河段浮游植物共4门119种(属),其中硅藻门最多,占藻类总数比例69.4%;绿藻门次之,占藻类总数比例28.2%。种类数季节变化明显,随春夏秋冬依次递减;一年中浮游植物密度浮动于0.36×10~4~21.21×10~4 cell/L之间,季节上为春冬夏秋逐渐降低;生物量变化在0.050 2~1.624 2 mg/L之间,季节上为春夏秋冬逐渐降低;浮游植物物种多样性指数介于2.27~4.73之间,表明该河段浮游植物群落结构稳定,抗外界干扰能力强;Palmer藻类污染指数介于1~14之间,均属轻污染,说明水质良好,但低海拔样点处的污染指数季节性变化大,这表明调查河段水生态环境季节性波动较大。     

宁波港压载水浮游植物多样性的研究

为了避免压载水作为媒介转移外来物种并造成污染危害,利用分子生物学技术研究宁波港来自印度洋、新加坡和美洲的压载水浮游植物。结果显示,新加坡和美洲的压载水没有检测到浮游植物。而印度洋的压载水里面含有硅藻门的直链藻属(Aulacoseirasp.)、海链藻属(Thalassiosirasp.)、骨条藻属(Skeletonemasp.)、冠盘藻属(Stephanodiscussp.)和星盘藻属(Discostellasp.);隐藻门的全沟藻属(Teleaulaxsp.)和斜片藻(Plagioselmissp.);绿藻门的括小球藻属(Chlorellasp.)、卵囊藻属(Oocystissp.)和Pseudococcomyxasp.;链形植物门包括新月藻属(Closteriumsp.)。同宁波港的港池浮游植物相比,生长速度快、抗逆性强的硅藻数量明鲜增多,有些种类是外来的。     

西藏工布自然保护区藻类植物区系及分布特点

基于对西藏工布自然保护区藻类植物的调查采集,共鉴定出189种(含变种),隶属5门,28科,50属。其中以硅藻门(Bacillariophyta)种类最多,有9科,18属,109种;绿藻门(Chlorophyta)为亚优势门类,有9科,20属,50种;蓝藻门(Cyanophyta)次之,为8科,10属,28种;红藻门(Rhodophyta)和金藻门(Chrysophyta)最少,各为1科,1属,1种。主要群落类型有7种,即颤藻群落、胶须藻群落、念珠藻群落、水树藻群落、桥弯藻群落、丝藻群落和双星藻-转板藻-水绵群落。指示藻类分析显示,目前该地区水体状况良好,基本未受到严重污染,大部分水体为β-中污带,其余部分为寡污带。该地区藻类植物的分布特点表现为高原冷水山溪急流种类典型、高山源头性种类明显但耐污种类较少。对该地区水体和藻类植物多样性保护提出了建议。     

引黄水库藻类变化特征及其影响因素研究

以济南鹊山引黄水库为研究对象,系统研究了2008-2012 年间其水中浮游藻类的种类和数量变化特征以及藻类细胞密度与总氮、总磷浓度的相关性,并在实验室模拟条件下分析了温度、光照、氮磷营养盐等条件对其藻类生长影响。结果表明,该水库水藻密度年际、年内变化较大,年平均值均在500 万个/L 以上,藻种共7 个门,37 个属,蓝藻和硅藻为水库的优势藻种。该水库藻类生长的最佳温度为25℃,光强为3 000 lx,氮磷营养盐对藻类生长影响排序为硝酸盐>磷酸盐>亚硝酸盐>氨氮。磷可能是藻生长的限制性因子,在夏、秋季及水库磷浓度大幅变化时易发生水华。     

汾河太原河段浮游植物多样性及微囊藻产异味物质成因

2012年7月和10月,对汾河太原河段浮游植物多样性及微囊藻产异味物质进行了调查研究,并对其水质进行了评价。结果显示:(1)共鉴定出浮游植物6门65属126种,其中绿藻门种类最多,有25属57种,其次为硅藻门,有26属40种,蓝藻门有9属20种,其它门种类相对较少,包括裸藻门2属5种,甲藻门2属2种,隐藻门1属2种;(2)2012年7月份的优势种为蓝藻门的微小平裂藻(Merismopedia tenuissima)、不定微囊藻(Microcystis incerta),硅藻门的尖针杆藻(Synedra acus),绿藻门的四尾栅藻(Scenedesmus quadricauda)、美丽网球藻(Dictyosphaerium pulchellum)和甲藻门的微小多甲藻(Peridinium pusillum),10月份的优势种为蓝藻门的微小平裂藻、阿氏浮丝藻(Planktothrix agardhii)、两栖颤藻(Oscillatoria amphibia),硅藻门的尖针杆藻,绿藻门的四尾栅藻和隐藻门的啮蚀隐藻(Cryptomonas erosa);(3)2012年7月份和10月份迎泽桥段浮游植物平均细胞密度分别为188.28×106个/L和58.66×106个/L,南内环桥段浮游植物平均细胞密度分别为83.78×106个/L和65.99×106个/L,表明水体为富营养型;(4)Margalef多样性指数(D)为2.04—2.68,Shannon-Wiener多样性指数(H)为0.49—1.00,Pielou均匀度指数(J)为0.13—0.26,数据分析显示汾河太原河段水质为中度污染至重污染;(5)通过对分离纯化的微囊藻挥发性异味物质的检测,8株微囊藻中有6株可产生明显的异味。经过嗅味判断及与常见异味种类标准品的比对,确定这6株微囊藻产生的异味物质主要为β-环柠檬醛(β-cyclocitral)。     

徐闻珊瑚礁自然保护区可培养富脂海洋微藻的生物多样性

从徐闻珊瑚礁自然保护区(20°10′–20°27′N, 109°50′–109°24′E)潮间带采集海水和泥沙样品, 用f/2-medium 培养液富集培养其中的海洋微藻, 采用基于96 孔板的“稀释分配”结合“微吸管剔除”的方法分离培养海洋微藻, 采用微藻形态学观察、18S rDNA 序列分析及其系统进化树构建的方法分析鉴定分离培养的藻株, 采用尼罗红染色法检测和分析海洋微藻细胞中的脂质。目的就是要分析研究徐闻珊瑚礁自然保护区潮间带可培养富脂海洋微藻的生物多样性, 为富脂海洋微藻的研究开发奠定基础。结果分离、培养、鉴定并储藏了118 株海洋微藻(Genbank 登录号为KU561102 ~ KU561219),含48 个种, 分布于硅藻门(Bacillariophyta)、绿藻门(Chlorophyta)和定鞭金藻门(Haptophyta) 3 个门的6 纲、22 目、24 个科、28 个属。其中, 有37 株为富脂微藻, 含22 个种, 分布于硅藻门和绿藻门2 个门的4 纲、11 目、12 个科、16 个属; 优势属为双眉藻属(Amphora), 含22 株,占分离培养藻株的18.6%; 含脂量最高的种群为辐节藻属(Stauroneis), 含Stauroneis anceps, Stauroneis gracilior, 和2 株Stauroneis kriegeri, 共4 株海洋微藻。这表明徐闻珊瑚礁自然保护区潮间带可培养的富脂海洋微藻的物种丰富多样, 可能是发掘多不饱和脂肪酸和生物柴油的理想资源。     

大庆新华湖藻类植物群落结构与环境因子的相关性

2014年5-10月对大庆新华湖藻类植物群落结构与环境因子的关系进行了初步研究, 为湖泊状况的动态监测提供基本数据。调查期间, 共发现藻类植物135种, 隶属5门63属, 其中硅藻门56种, 绿藻门49种, 蓝藻门15种, 裸藻门12种, 甲藻门3种。新华湖优势种共24种, 包括绿藻门14种, 蓝藻门6种, 硅藻门3种, 裸藻门1种, 且季节更替明显, 可以初步推断新华湖藻类植物群落组成为绿藻-硅藻型。新华湖藻类植物细胞丰度变化范围为37.57×10⁶-72.37×10⁶ cells·L^-1, 平均值为52.13×10⁶ cells·L^-1。多样性指数变化为: Simpson生态优势度指数(D)在0.642-0.928之间, Shannon-Weaver多样性指数(H')在1.698-3.1之间, Pielou均匀度指数(J)在0.324-0.561之间, 3种指数变化趋势一致, 均在秋季最高, 春季最低。研究表明, 水温、pH值、总磷、生化需氧量、溶解氧和水动力是影响新华湖藻类植物群落结构的主要因子。     

稻虾共作水体浮游植物群落结构特征分析

为认识稻虾共作水体浮游植物群落结构特征, 于2016年4月至12月对江汉平原4处稻虾共作水体浮游植物和理化因子开展了逐月调查与分析。共鉴定出浮游植物7门124种, 其中绿藻78种、蓝藻16种、硅藻15种、裸藻3种、隐藻2种、甲藻7种、金藻3种。6—9月浮游植物的种类数、细胞密度、叶绿素a含量达到最大值, 最小值出现在12月份; 浮游植物细胞密度波动范围在1.37×105—2.93×108 cells/L, 叶绿素a含量的变化范围为0.15—208.60 μg/L。调查期间浮游植物的优势种共28种, 主要优势种有颤藻、蓝纤维藻、微囊藻、小球藻、隐藻等。浮游植物Shannon-Wiener多样性指数周年变化范围为0.64—6.3, 多样性指数最高出现在10月份, 最低出现在8月份。结果显示, 稻虾共作水体浮游植物群落结构较复杂, 细胞密度变化显示时空的一致性, 优势种组成以及优势度存在明显的空间差异(P<0.05), 稻田的浅水环境以及小龙虾的养殖行为显著影响浮游植物群落的结构。鉴于藻类作为初级生产者对于水生态环境和小龙虾健康具有重要作用, 关注种养结合水体中藻类群落的演变规律对于保障稻田种养的综合效益具有积极意义。     

三峡库区甘井河水域牧场浮游植物群落结构及水质评价

为了解三峡库区的忠县甘井河段水域牧场生态渔业对水环境的影响, 于2013 年3、6、9 及12 月按季度对该河段4 个站点进行了浮游植物群落结构及水体理化因子的监测, 并采用生物多样性指数法和综合营养状态指数法对水体营养状况进行了评价。结果表明, 该河段浮游植物有7 门93 个属种, 其中绿藻门的物种数最多, 有37 种, 占浮游植物群落总数的39.79%, 其次为硅藻门和蓝藻门, 物种数分别为26 种和13 种,分别占浮游植物群落总数的27.96%和13.98%;浮游植物的年均丰度为757.67104 ind./L, 变化范围(3.065743.99)104 ind./L, 年均生物量为4.40 mg/L, 变化范围0.0317.67 mg/L;水体的年平均透明度为1.18 m, 叶绿素a、总磷、总氮含量分别为8.54 g/L、0.13 mg/L、1.95 mg/L;浮游植物香农多样性指数(H')、均匀度指数(J)年均值分别为2.90 和0.88, 全年综合营养状态指数值为37.5971.86, 由此推断, 甘井河水质属于中污染轻污染状态、中营养型富营养型。在鱼类生长旺季的6 月, 甘井河段养殖区内的水质优于非养殖区, 这可能与养殖区内放养滤食性鱼类有关, 证实了水域牧场没有带来水环境的污染, 反而能提高生物多样性, 在一定程度上改善了水体。       

MEASUREMENTS OF PHYTOPLANKTON-PROTEIN CONTENT WITH THE HEATED BIURET-FOL1N ASSAY1,2

The heated biuret-Folin method for determining protein consistently measures 90% of the total nitrogen of filtered algae samples as protein-N without the need of mechanical disruption as long as the heating period in biuret is 100 min at 100 C. Data indicate this protein assay measures total protein on all species tried and for naturally occurring mixtures of species plus detritus. Dilute algal suspensions with as little as 0.05 μg-atom particulate protein N.liter ^-1 can he concentrated by fltration on glass fiber filters to 1.0 μg-atom particulate protein-N per filter, the optimal amount of sample for a 5 ml volume of biuret. The filtered algae samples can be stored for several weeks frozen before assaying, if necessary.     

用藻类监测和评价图们江的水污染

在图们江上、中游进行了人工基质着生藻类调查和室内栅藻检测,以监测和评价水污染状况。在所采用的野外监测指标中,以着生藻类总数与污染程度的关系最为明显。为便于比较和综合,采用了相对藻类总数(PN) 根据调查结果,提出了可作为图们江污染的指示种类。多样性指数与污染的关系,因受到其他非污染因子的影响,并不稳定。研究结果表明:图们江的主要污染源是尾矿废水(悬浮物)和纸浆废水(悬浮物、色度和有毒物质)。最严重污染江段为菜队到图们江段,次之为南坪江段。       

沱江浮游生物群落时空分布及相关环境因子分析

为研究沱江浮游生物群落结构的时空特征,并探讨影响其形成的环境因子,于2013年对沱江10个采样断面按季节进行采样分析。研究期间共检出浮游甲壳动物13种,以中小型枝角类和剑水蚤为主; 尽管桡足类密度与枝角类接近,但由于体型原因桡足类生物量始终占据优势地位。检出浮游植物7门95种,优势属7个,全年均以硅藻为主。两类生物在上游资阳市区的断面中总生物量最高,中游农村断面最低; 其生物量季节变化也趋于一致,均在丰水季节8月取得最高值,枯水季节2月最低。与历史数据相比,呈现出浮游植物增多,浮游甲壳动物减少的趋势。根据结构方程模型(SEM)和冗余分析(RDA)的结果,浮游甲壳动物生物量在浮游植物生物量和溶氧高的环境中较大,桡足类对溶氧的要求比中小型枝角类高。浮游植物对高温、高营养和高pH较偏好,尤其是一些优势属。尽管受浮游植物生物量影响,浮游动物对浮游植物的控制力却极弱。在流速缓慢且污染较严重的城市江段浮游植物密度已高达2.7107 cells/L,浮游动物尽管能选择性地以部分浮游植物为食,对其控制力却极弱,如不加强污染控制,沱江可能有暴发水华的危险。     

A comparison of different methods used for the quantitative evaluation of biomass of freshwater phytoplankton

Although in a strict sense the term phytoplankton biomass only refers to living algal material, in aquatic ecology the term has been associated with a variety of biological and biochemical procedures used to quantify the particulate matter suspended in natural waters. Relative merits of different biomass characteristics have been studied in three Dutch freshwater lakes with great differences in absolute biomass. Parallel determinations have been made of seston dry weight and supplementary elementary and caloric analyses of seston, of chlorophyll-a concentration and supplementary paper chromatographic analyses of pigment extracts, of particle concentration and particle size distribution as studied with an electronic particle counter, and of phytoplankton cell volume as calculated from the results of microscopic enumeration and sizing of algae. In this way an attempt was made to create a detailed picture of the nature of the seston of the three freshwater lakes.Different analytical techniques give strikingly different information, the accuracy of any method is largely dependent on the circumstances present, and different biomass characteristics therefore are only of value in limited spheres. It is suggested to distinguish between total seston characteristics (e.g. seston dry weight, particulate organic carbon, total particle volume) and strictly algological biomass characteristics (e.g. chlorophyll-a concentration, phytoplankton cell volume). The pattern of growth of phytoplankton populations shown by e.g. chlorophyll-a concentration may differ markedly from that indicated by e.g. total particle volume or seston dry weight. Also, to more or less extent the wax and wane of phytoplankton populations may go undetected among the total seston. Apparently, there is no one method of estimating biomass and no conversion factor that may serve for general purposes. In general, unambiguous information on the nature of the seston of natural waters may only be obtained by estimating total seston characteristics and algological biomass characteristics simultaneously. Depending on the objective of the investigation supplementary component analyses should be carried out to guarantee the correct interpretation of the results.     

COLONIZATION AND STANDING CROPS OF EPILITHIC ALGAE IN THE SUSQUEHANNA RIVER,PENNSYLVANIA1

A SCUBA diver, using a bar-clamp sampler, collected quantitative epilithic algae samples from artificial substrates (slate and acrylic plates) and river stones at two stations on the Susquehanna River bottom in 1974. At Falls, Pennsylvania, algal colonization on monthly plates (submerged for ca. 30 day periods) was most rapid between September and October. In winter, when algal density on cumulative plates (submerged 2–13 mo) and on stones present in the river peaked at 18,100 and 21,900 units/ mm², respectively, colonization of clean monthly plates nearly ceased. Similar colonization patterns were observed in a portion of the river polluted by coal mine drainages (SSES), but expansion of the algae population at SSES was inhibited by iron in the effluents, and densities never exceeded 2,400 units/mm² on stones or plates. Diatoms composed 95% of the overall standing crop at Falls and 65% at SSES.     

The distribution of phosphorus between soluble and particulate phases for seven Scottish East Coast rivers

Phosphorus (P) fractions were quantified in water samples collected on four occasions from sites at the lower tidal limit of seven Scottish East Coast rivers. Individual catchment characteristics ranged from those dominated by semi-natural land use to those where agriculture predominated. Together the rivers displayed attributes ranging from nearly pristine to those impacted by point and diffuse sources of pollutants. Sampling times were chosen to coincide with periods of low river flows where conditions should result in low concentrations of suspended particulate matter (SPM) but favourable for phytoplankton growth. Total phosphorus (TP) concentrations were < 0.004 mg l^–1, 0.005–0.048 mg l^–1 and 0.28–2.2 mg l^–1 for pristine, agricultural and point source impacted rivers respectively. Soluble reactive phosphorus (SRP) represented from < 5% to > 90% of TP and dissolved P dominated all samples. The total phosphorus content (TPC) of SMP ranged from 0.1 to 1.1% and was significantly related to SRP. Organic matter was a significant component of SPM and organically bound phosphorus was the dominant form of particulate P. The C/P ratio of organic matter was wide, between 500–1200 for the more pristine systems which narrowed to < 400 for heavily impacted rivers. Exchangeable P increased during the summer but was generally a minor component of TP and therefore likely to be a significant source of SRP only in pristine rivers. Phytoplankton constituted between 5 and 46% of organic matter and concentrations of chlorophyll-a were significantly correlated with both TP and SRP.     

D2O effects on association behavior and binding properties of phospho- and dephospho-cytoplasmic malic dehydrogenase

Changes in the concentration of three major carbohydrates, e.g., glycogen, trehalose, and cellulose, were determined during differentiation of Dictyostelium discoideum in a stage study. These three carbohydrates consituted 50–63% of the total carbohydrates. Total carbohydrate content per cell aliquot did not change between the aggregation and sorocarp stages of differentiation. The isolation, purification, and characterization of cellulose is described. Cellulose consisted of an alkali-insoluble (alpha) and an alkali-soluble (beta) fraction. Total cellulose accumulated from very low amounts in late pseudoplasmodium cells to about 35% of carbohydrates in mature sorocarps at a rate of 0.07 μmole glucose equiv/min/ml packed cell volume. Purified alkali-insoluble cellulose constituted about 19% of total carbohydrates in mature sorocarps and accumulated at a rate of 0.035 μmole glucose equiv/min/ml packed cell volume. Trehalose constituted 10–11% of the carbohydrates in sorocarps and accumulated at a rate of 0.035 μmole glucose equiv/min/ml packed cell volume. Glycogen, comparing several methods of determination, was rapidly degraded between the culmination and sorocarp stages of differentiation at an average rate of 0.05 μmole glucose equiv/min/ml packed cell volume. The major portion of glycogen was soluble in TCA and constituted 35% of total carbohydrates in aggregated cells and about 11% in mature sorocarps. A minor fraction of glycogen, about 15% of total carbohydrates in aggregated cells, was solubilized by KOH from a TCA precipitate. A mild acidic treatment of solubilized cell constituents increased the glycogen content by 55%, as judged by an enzymatic assay.     

EFFECTS OF SUSPENDED SEDIMENT ON BIOMASS AND CELL MORPHOLOGY OF CLADOPHORA GLOMERATA (CHLOROPHYTA) IN THE COLORADO RIVER, ARIZONA

This study assessed changes in biomass, filament length, and cell morphology in Cladophora glomerata (L.) Kütz. along a suspended sediment gradient in the Colorado River below Glen Canyon Dam, Arizona. Suspended sediments ranged from 2.0 mg·L⁻¹ at Lees Ferry (Rkm 0.8) to 4.2 mg·L⁻¹ at Gorilla Island (Rkm 352). There was a 74% decrease in Cladophora biomass along the river transect through Grand Canyon National Park and a significant decrease in filament and cell length, but cell width increased. Similar changes in cell morphology occurred after 19 days when C. glomerata was transplanted from a low suspended sediment site (2.0 mg·L⁻¹) at Lees Ferry to a habitat with high suspended sediments (≥20.0 mg·L⁻¹). Cell length increased and cell width decreased when plants were transplanted back to the low suspended sediment habitat for 24 days. In situ studies with reduced light in the absence of suspended sediments showed no change in cell morphology. These in situ experiments imply that changes in cell morphology by C. glomerata in waters with high suspended sediments are adjustments in structural integrity to accommodate the abrasive force of suspended particles. Our study suggests that cell dimensions in Cladophora might be too plastic under varying environmental conditions to be used in taxonomic determinations.