初析赤潮成因研究的围隔实验结果Ⅱ.浮游植物群落演替与甲藻赤潮

探讨了甲藻赤潮与浮游植物演替的关系．多次国隔生态系实验结果表明,在水体相对稳定的生态系中,富营养后总是先发生硅藻的水华或赤潮．随后浮游植物会演替成占优势的甲藻,甚至形成甲藻赤潮．维生素Ｂ（１２）的异常增多可能加速这种演替的进程．但这种稳定水体若受到扰动,将干扰演替,使硅藻水华持续不断地发展,阻碍甲藻形成优势．这可以防止甲藻赤潮的生成．     

海洋围隔生态系中无机氮对浮游植物演替的影响

本文评述了１９９２年秋冬季在厦门进行的一次海洋围隔生态系实验的结果。实验重现了围隔水体连续富营养引发了甲藻赤潮的现象。间歇性的供给无机氮,不会影响浮游植物演替的顺序,但会导致甲藻赤潮出现时间长短和优势种的差异。实验结果还表明,演替过程对甲藻赤潮的形成起着重要的作用。而不同种属甲藻的生活习性和它们的自养能力使它们的生存能力存在差异。这是形成甲藻赤潮优势种的一个主要因素。甲藻赤潮的发生并不完全依靠水体中营养盐浓度的大小。     

不同营养盐条件下赤潮高发区围隔生态系内多胺的变化

在东海赤潮爆发区域运用围隔生态系实验方法,研究了不同营养盐条件下围隔生态系内多胺浓度变化。结果表明:2010年选用东海原甲藻赤潮爆发处海水,东海原甲藻是各围隔生态系内主要优势种,没有种群演替现象发生。两种营养盐添加方式下各围隔内精胺浓度维持较高水平,都呈现先波折下降后波折上升的趋势,与东海原甲藻的生长变化正好相反;各围隔内腐胺浓度水平较高,变化起伏较大,其中有两个实验组腐胺整体变化趋势与东海原甲藻生长趋势类似;所有围隔内亚精胺浓度最低,波动较小。2011年取用中肋骨条藻赤潮爆发处海水,所有围隔生态系内优势种都发生了从中肋骨条藻到东海原甲藻的演替。各围隔生态系内腐胺浓度最高,在中肋骨条藻生长初期腐胺浓度下降,随着中肋骨条藻的生长有所上升,实验后期随着东海原甲藻的生长又整体呈现出下降趋势;各实验组精胺浓度较低,在中肋骨条藻消亡东海原甲藻出现的种群演替期间,都呈现出较大波动;各围隔内亚精胺浓度较低,在整个种群演替过程中没有明显的变化。围隔生态系中补充营养盐,通过对浮游植物生长的影响,间接影响围隔生态系内的多胺变化。     

围隔藻类水华演替过程中二甲基硫化物的含量动态

于2005年6月至7月,研究了海洋围隔不同藻类水华演替过程中二甲基硫化物的含量动态,并考察了相关环境参数对二甲基硫化物含量的影响。2个围隔实验组均出现未知藻水华-硅藻水华-甲藻水华的演替过程,这3次不同藻类水华分别对应了二甲基硫化物含量的3次高峰,表明藻类水华对二甲基硫化物含量有重要贡献。不同藻类水华的贡献有较大差异,甲藻水华的贡献最大,硅藻次之,未知藻类水华的贡献最小。实验结果还表明PO4^3-、NO2^-和NH4^＋主要通过影响藻类生长状态,进而影响DMSP和DMSO的含量;NO2^-和NH4^＋亦可能通过调节DMSP和DMSO在藻细胞内的生理功能,影响DMSP和DMSO的含量;PO4^3-、NO2^-和NH4^＋与DMS含量无显著相关。     

东海两种赤潮生物种间竞争的围隔实验

1998年5月和2002年5月在东海赤潮高发区进行了两次添加营养盐诱发赤潮的围隔实验,结果表明,1998年5月实验开始时,具齿原甲藻和中肋骨条藻分别占群落总量的85％和11％,对照围隔中,具齿原甲藻一直处于优势,高峰时所占比例接近99％．加磷围隔中,中肋骨条藻显示出很强的竞争能力,第五天的数量与具齿原甲藻相等．2002年5月用4个围隔装置进行实验,在不同营养状况下两个种的增殖速率不同,营养盐浓度高的围隔中,中肋骨条藻的增殖速率比具齿原甲藻快得多,在营养盐限制条件下,具齿原甲藻比中肋骨条藻存活的要好。表明在营养盐丰富情况下,中肋骨条藻以其快速的繁殖在竞争中取得优势地位,导致中肋骨条藻形成的赤潮持续时间较短,消亡也快,而具齿原甲藻赤潮形成期较长,但在营养盐很低的情况下,还能维持较长时问．     

大亚湾浮游植物群落特征

于2002年冬、春、夏和秋季对大亚湾浮游植物进行采样调查,分析了浮游植物的种类组成、丰度、优势种、多样性及群落结构的季节变化特征和平面分布特征。并讨论了浮游植物与营养盐、水温及环流等环境因子之间的关系。2002年大亚湾浮游植物共鉴定出48属114种(包括变型和变种),丰度范围在5.79×104~5.37×106cells/m3之间,平均值为1.14×106cells/m3。其中硅藻共37属84种,其种数和细胞丰度都占绝对优势,平均丰度为1.08×106cells/m3,其次为甲藻,9属23种,平均丰度为9.91×104cells/m3。此外还鉴定出蓝藻和金藻。大亚湾浮游植物丰度变化呈单一周期型,春夏季高,秋冬季节低。虽然硅藻的丰度占优势,但秋季硅藻丰度降低(占总丰度75.8%)使甲藻和蓝藻所占比例上升。研究得出春夏季大亚湾浮游植物主要以沿岸暖水性种类为主,秋季和冬季除沿岸暖水种之外,广布种和大洋种也较多,尤其在冬季后者占优势。大亚湾浮游植物优势种类多,不同季节既有交叉又有演替。与以往调查资料相比,部分优势种发生变化,优势程度顺序和细胞丰度发生了一定改变,个体较大的细胞丰度优势逐渐增加。另外,受季风、潮流、地理位置及人类活动影响,大亚湾浮游植物丰度和群落结构有一定的季节和平面分布特征。大亚湾浮游植物的多样性在夏季偏低,尤其在大亚湾核电站和大鹏澳养殖区附近表现明显。大亚湾浮游植物的丰度、种数、优势种演替及群落结构等其它群落特征与营养盐尤其是氮、磷和N/P、水温、环流等环境因子密切相关。     

汉江中下游春季浮游植物群落结构特征及其影响因素

针对汉江中下游春季硅藻水华频繁暴发的现状,研究了水华暴发不同时期浮游植物群落结构特征,并结合水体理化因子分析,揭示硅藻水华发生的主要影响因子。结果表明:汉江春季水华暴发期间,共鉴定出浮游植物7门48属64种(含变种),其中硅藻种类所占比例最大(18属23种),不同样点所占比例介于44.13%~51.29%,其次是绿藻类(16属22种),不同样点所占比例介于28.21%~35.14%,蓝藻门和隐藻门种类数在水华期间较少,各样点仅发现2~3种,金藻门和甲藻门种类最少;水华发生期间主要优势种为硅藻门的小环藻,水华暴发初期和中期往往形成单优种,而水华末期随着其优势度的降低,蓝藻门、隐藻门和硅藻门其他种类也会形成优势种;水华暴发期间浮游植物密度最高可达2.34×107cells·L-1,其中小环藻种群数量最高可达2.06×107cells·L-1,占浮游植物群落总数的88%;浮游植物多样性指数中,Margalef物种丰富度指数无显著时空差异,Shannon多样性在水华中期较低,而水华初期和末期相对较高,Berger-Parker指数变化与Simpson指数相反;浮游植物与理化因子的冗余分析(RDA)发现,浮游植物总数量与磷酸盐、溶解氧、总磷呈正相关,与硝酸盐、温度、透明度呈负相关。     

在不同蓄水位下三峡库区春季水华特征及趋势分析

基于2004—2015年三峡库区支流春季水华的监测数据,开展了三峡库区不同蓄水位下春季水华特征及趋势分析。结果表明:总共有26条支流发生春季水华,香溪河为水华发生概率最高的支流。水华藻类优势种主要是硅藻和甲藻,甲藻水华出现的概率随着蓄水位的增加而增加,但是在持续几年175 m蓄水之后,甲藻水华出现的频率下降,硅藻水华出现的频率增加。在175 m蓄水之前,水华发生期藻类密度、叶绿素a含量及水体营养盐水平相对较低,此后都有了较高的提升,但是在持续几年175 m蓄水之后,藻类密度、叶绿素a浓度以及营养盐浓度都有下降趋势。对藻密度及叶绿素a含量与主要环境因子进行主成分分析(Principal components analysis)发现,藻密度和叶绿素a与总磷、总氮、高锰酸盐指数聚类一簇,藻密度、叶绿素a浓度与总磷、溶解氧、高锰酸盐指数显著正相关。在蓄水之后,三峡库区支流营养水平有所增加,随着蓄水位的增加,三峡库区支流断面的平均流速降低,在合适的温度下,三峡库区支流水华易发生。     

深圳市污染物排放总量与其东部水体赤潮发生的关系

探讨了深圳市污染物排放总量对深圳东部海域赤潮发生的影响.结果表明：深圳市总氮(TN)、总磷(TP)净排放量以及排污中的N∶P与东部海域甲藻赤潮发生频率呈明显正相关;推算出东部甲藻赤潮爆发的TP、TN年排污阈值分别为3.917×10³ t和2.123×10⁴ t;而近岸排污与硅藻赤潮发生的相关性不明显.举例说明了深圳排污总量控制的具体方式.     

2006年春夏期间浙江南麂海域浮游植物群落结构特征

研究了2006年春夏期间(4~6月)浙江省南麂列岛海域的浮游植物群落结构,共观察到68种浮游植物,其中硅藻53种,甲藻13种,金藻和蓝藻各1种。调查期间,该海域浮游植物群落结构变化明显,原甲藻赤潮的形成和持续是最显著的特征,三角棘原甲藻和东海原甲藻分别在5月中、下旬先后引发赤潮。原甲藻赤潮的形成与水温有密切关系,其生消引起海水中营养盐结构的相应变化。     

Ecological restoration in eutrophic Lake Wuli: A large enclosure experiment

A large-scale enclosure experiment for lake restoration was carried out in Lake Wuli, a northern bay of shallow and eutrophic Lake Taihu in China. The large enclosure with an area of 10 ha was set up in the littoral zone and was bordered by waterproof fabric which did not cover the sediments. Multiple approaches were used and included fish removal, piscivorous fish stocking, shoreline reconstruction, aquatic macrophyte planting, benthic macro-animal stocking, and silver carp cultivation in pens for reduction of cyanobacteria. The results showed that the coverage of aquatic macrophytes increased from 0% to 45.7%. Mean concentrations of TN and TP inside the enclosure from May 2004 to May 2008 were 22.2% and 26.0% of those outside, respectively. Secchi depth was 0.40 m outside the enclosures and 0.75 m inside. However, responses of phytoplankton to the restoration project lagged behind improvement of water quality and reestablishment of aquatic plants. The phytoplankton biomass gradually decreased after the third year of the restoration. Stocking piscivorous fish and planting submerged macrophytes could not increase zooplankton biomass and enhance graze pressure on phytoplankton, most likely due to high omnivorous fish density and lower nutrition inside the enclosure. Higher grazing pressure of zooplankton on phytoplankton was observed in May and October every year. Zooplankton to phytoplankton biomass ratios were significantly negatively correlated with phytoplankton biomass outside (r = −0.440, p < 0.01) and inside the enclosure (r = −0.336, p < 0.05) from February 2004 to March 2007. Therefore, phytoplankton biomass inside and outside the enclosure was lower in May and October. Higher grazing pressure of zooplankton on phytoplankton in spring may result in occurrence of the clear-water phase that facilitated growth of submerged macrophytes in the littoral in Lake Wuli, and a clear-water state and improved water quality would likely be sustained throughout the year after reestablishment of submerged macrophytes.     

Biogeochemistry and effects of copper,manganese and zinc added to enclosures in Island Billabong,Magela Creek,northern Australia

Three large plastic enclosures (5 m diam, volume 40 m³) were used to study the effects of copper, manganese and zinc, on the phytoplankton community in Island billabong, a floodplain billabong (waterhole) situated in the Magela Creek in tropical northern Australia. Copper was added to one enclosure, and manganese and zinc to another, to give initial concentrations around ten times the normal wet season values. The enclosures and the billabong were monitored over a ten week period towards the end of the dry season, with the enclosures allowed to stabilise for four weeks before the metals were added.The control enclosure adequately simulated the temperature and pH changes in the billabong. The trends in conductivity, dissolved oxygen and major ion concentrations were similar in the enclosure and the billabong, with the minor differences observed attributed to either epiphytic growth on the enclosure walls (influenced dissolved oxygen, pH and bicarbonate concentration) or ingress of sulphate-rich groundwater into the billabong (influenced sulphate concentration and conductivity). Major differences in both the composition of species and the size of the phytoplankton populations were observed between the three enclosures and between the control enclosure and the billabong. This variability reflects the great natural variability in the phytoplankton communities in tropical lentic systems, and means that enclosures are unlikely to adequately simulate the biological communities in the billabongs.The control enclosure appeared to simulate quite well the longer term changes in total concentration and speciation of the three metals (copper, manganese & zinc) in the billabong. The mean concentrations of copper and zinc were similar in the two systems, although the mean concentration of manganese in the billabong was almost double that in the enclosure, possibly due to ingress of manganese-enriched groundwater. Particulate forms dominated the speciation of copper and manganese. There was considerable short term variation in both total metal concentration and speciation in both the enclosure and the billabong. This variability appears to be a feature of these small tropical waterbodies.The added heavy metals were found to have minimal detrimental effect on the phytoplankton community in each metal-loaded enclosure. The high natural variability in the phytoplankton community in these tropical systems will make it difficult to separate natural changes from those caused by low level contamination from mining operations should this occur.All three metals were rapidly removed from the water column, so that by the end of the six week period, only ca. 5% of each added metal remained in the water column. Association with the particulate matter (phytoplankton, abiotic particulate matter and MnO_x in enclosure 2) followed by sedimentation was the major removal pathway. Epiphytes growing on the enclosure walls appeared to have a minor influence (<10% of the total amount of metal added) on the removal of the added metals. For copper, uptake by phytoplankton followed by sedimentation was the major (65%) removal process. Manganese and zinc, added together, were found to influence each other. The major manganese removal process (60%) was rapid (ca. 3 days) involving bacterial oxidation and sedimentation of the MnO_x formed. This material appeared to have little influence on the behaviour of zinc, possibly because other particulate matter competed more effectively for the zinc. A further 30% of the added manganese was removed via initial adsorption to other particulate matter, possibly phytoplankton. Approximately one third of this adsorbed manganese (10% of the total added) appeared to undergo delayed oxidation some 8 days after the initial additions, and the heavier particles settled out more rapidly. This path was responsible for removing the major amount (ca. 60%) of the added zinc. We hypothesis that the sorbed zinc inhibited the bacterial oxidation of the manganese. A further 25% of the zinc was removed in association with a burst of phytoplankton activity. The occurrence of bursts in the phytoplankton activity, when populations can increase very substantially and then decrease again, all within the space of a day, appears to be an important mechanism for removing copper and zinc from the water column in these tropical water bodies     

Effects of physical refuges on fish–plankton interactions

1.Refuges that reduce fish-induced mortality of zooplankton are considered to be key factors in controlling phytoplankton growth in lake ecosystems. In order to better understand the role of physical refuges for zooplankton on zooplanktivorous fish-plankton relationships, an enclosure experiment was run in a mesotrophic lake. Even-link systems (zooplankton and phytoplankton) and odd-link systems (zooplanktivorous fish, zooplankton and phytoplankton) were established. We also established an odd-link system with a physical refuge for zooplankton where fish predation was limited in the upper half of the enclosure.
2.Fish negatively affected density and mean body length of herbivorous zooplankton and total zooplankton, filtering rates with some intermediate effects in the presence of the refuge. A clear refuge effect was observed for the dominant herbivore, Ceriodaphnia . On the other hand, the refuge seemed to increase the vulnerability of those taxa that aggregated in upper layers of the water column. Grazing was thus reduced in both odd-link systems.
3.The lack of significant correlation between nutrient availability and phytoplankton biomass in enclosures suggested a top-down control of algal growth in our experimental systems. In both odd-link systems ('fish' and 'refuge') phytoplankton biomass was significantly enhanced, and transparency was reduced in comparison with the even-link system.     

The role of fish in the regulation of nutrient cycling in Lake Balaton, Hungary

SUMMARY. 1. In 1984 an enclosure experiment was carried out in order to elucidate the importance of nutrient supply from fish to phytoplankton during the critical summer period in eutrophic Lake Balaton. One enclosure was stocked with fish and the other left empty.
2. Two peaks were recorded in primary production reaching maximum values in the fish enclosure.
3. In the enclosure with fish, inorganic nitrogen concentrations increased gradually till the end of the experiment, with ammonia making up the largest component. Lower dissolved phosphorus concentrations in the fish enclosure, with its higher primary production rate, may indicate an intense cycling of this nutrient.
4. The biological and chemical changes occurring in the enclosure suggest that bream removal can be an effective tool in water quality control for Lake Balaton.     

Mixing an enclosed, 1300m3 water column: effects on the planktonic food web

The nutrient, phytoplankton, and zooplankton dynamics in threeenclosed water columns (1300 m³) are described. Two of the enclosureswere mixed using a bubbling chamber at depth. Young chum salmon(Oncorhynchus keta) were added to one of the mixed enclosuresand the unmixed enclosure. No other manipulations were imposed.Copepods appeared in large numbers (e.g. especially Pseudocalanusminutus s.l. and Paracalanus parvus) and population growth rateswere estimated. Ctenophora did not appear in large numbers despitepresumably ideal food environments; it is suggested that inone enclosure this is a consequence of fish predation on thectenophores. The fish experienced high mortalities and low growthrates presumably due to unsuitable prey size. Weekly collectionsof sediment permitted isolation of two major sediment contributors,the first from phytoplankton sinking and the second from biogenkfallout associated with herbivore production. It was found thatthe more oligotrophic enclosure (unmixed) experienced proportionallyhigher utilization of organic carbon. Some of these resultsare explained by our data while others require more sophisticatedexperimentation, both in the design of the containers and inthe types of observations.     

The impact of planktivorous flsh on the structure of a plankton community

SUMMARY. 1. The abundance of pianktivorous juvenile yellow perch, Perca flavescens , was manipulated in three 750 m³ enclosures in a eutrophic lake.
2. There was a significant negative relationship between fish and zoopiankton biomasses. At high fish densities the zooplankton community was dominated by small filter-feeding cladocera. primarily bosmi- nids. At low fish densities the zooplankton community was dominated by large filter-feeding cladocera, primarily daphnids.
3. There was no significant relationship between zooplankton and phytoplankton biomasses when considered over the whole experiment but there was a trend towards lower phytoplankton biomass in the enclosure dominated by daphnids during mid-summer.
4. We conclude that although planktivorous fish have a strong negative impact on zooplankton community biomass and size structure, the relationship at the next lower trophic level, zooplankton and phytoplankton, is much weaker. Therefore, the biomanipulation of planktivorous fish populations as a management technique to control phytoplankton abundance is largely ineffective.     

Impact of whitefish on an enclosure ecosystem in a shallow eutrophic lake: changes in nutrient concentrations,phytoplankton and zoobenthos

Large bag-type (75 m³) and tube-type (105 m³) enclosures were set up in the shallow eutrophic Lake Suwa and were each stocked with exotic planktivorous whitefish (Coregonus lavaretus maraena). The release of whitefish caused the increase in nutrient concentration in the tube-type enclosure whereas no such increase was observed in the bag-type enclosure. Bottom sediment seemed to be an important source of chironomid food for whitefish. The proportion of phytoplankton measuring<10μm and 20–40μm, which respectively corresponded toOchromonas spp. andCryptomonas sp., were lower in the fish enclosures than in the control, which might have been caused by high grazing pressure by rotifers. The predation by whitefish might have affected the species composition of phytoplankton through reducing copepod predation on rotifers, not through reducing the densities of cladocerans which directly feed on phytoplankton as many investigators have reported. The phytoplankton biomass was not affected much by the release of fish. Possible reasons are that the increase in density of rotifers reduced the biomass of available phytoplankton and also that inedible Cyanophyceae were in the decreasing phase of their seasonal succession and could not increase successfully in spite of elevated nutrient levels.     

Changes in the plankton community following introduction of filter-feeding planktivorous fish

1. We conducted enclosure experiments in a shallow eutrophic lake, in which a biomass gradient of the filter-feeding planktivore, silver carp, Hypophthalmichthys molitrix Valenciennes, was created, and subsequent community changes in both zooplankton and phytoplankton were examined.
2. During a summer experiment, a bloom of Anabaena flos-aquae developed (≈ 8000 cells mL⁻¹) solely in an enclosure without silver carp. Concurrent with, or slightly preceding the Anabaena bloom, the number of rotifer species and their abundance increased from seven to twelve species (1700–14 400 organisms L⁻¹) after the bloom in this fish-free enclosure. Protozoans and bacteria were generally insensitive to the gradient of silver carp biomass.
3. During an autumn experiment, on the other hand, large herbivorous crustaceans were more efficient than silver carp in suppressing the algae, partly because the lower water temperature (≈ 24 °C) inhibited active feeding of this warm-water fish and also formation of algal colonies. Heterotrophic nanoflagellate and bacterial densities were also influenced negatively by the crustaceans.
4. Correspondence analysis (CA) was applied to the weekly community data of zooplankton and phytoplankton. A major effect detected in the zooplankton community was the presence/absence of silver carp rather than the biomass of silver carp, whereas that in the phytoplankton community was the fish biomass before the Anabaena bloom, but shifted to the presence/absence of the fish after the bloom.     

罗非鱼对水质的影响

鱼类是影响水库等水质的重要因素,以我国南方主要养殖鱼类之一的罗非鱼为对象,通过广东大镜山水库原位围隔实验,研究了鱼类对水质的影响。结果表明,与对照组相比罗非鱼围隔中总氮,总磷和叶绿素a浓度分别升高了42%,129%和347%。罗非鱼的排泄增加了水体营养负荷,为浮游植物生长提供大量的营养盐,引起浮游植物生物量增加,水体透明度降低。罗非鱼通过营养盐释放所产生的上行效应明显大于由其牧食导致的下行效应。     

Enclosures study of trophic level interactions in the mesotrophic part of Lake Balaton

Enclosures, open to the bottom sediments and to the atmosphere, containing about 17 m³ of lake water in the mesotrophic area of Lake Balaton, were used to elucidate the role of the benthivorous fish bream (Ambramis brama L.) in the lake during 1984–1986.Throughout the whole period water was less transparent in the enclosure containing fish, which strongly influenced the concentrations of suspended solids and chlorophyll a.Both phytoplankton biomass and production readily responded to nutrient increase in the enclosure with fish. In 1985 diatoms were replaced by cyanobacteria whereas in 1986, at a lower fish stocking, a shift in algal structure towards chlorophytes was observed.Egested organic substances and the resuspension of sediment particles by fish increased bacterial production.