Research Article
TheScientificWorld (2001) 1, 337–356
ISSN 1532-2246; DOI 10.1100/tsw.2001.67
*Corresponding author
?2001 with author. 337
Practical Success of Biomanipulation using
Filter-feeding Fish to Control Cyanobacteria
Blooms
A Synthesis of Decades of Research and Application in a Subtropical Hypereutrophic Lake
Ping Xie * and Jiankang Liu
Donghu Experimental Station of Lake Ecosystems, The State Key Laboratory for Freshwater Ecology and Biotechnology of China, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, P.R. China Email: Xieping@https://www.doczj.com/doc/6b13840846.html,; Liujk@https://www.doczj.com/doc/6b13840846.html,
Received June 11, 2001; Revised June 25, 2001; Accepted June 25, 2001; Published August 8, 2001
Lake Donghu is a 32-km 2 shallow, subtropical lake near the Yangtze River (P.R. China) that has experienced dramatic changes in the past five decades. These changes include: (1) a trophic state change from mesotrophy to hypertrophy; (2) dense blooms of cyanobacteria during every summer from the 1970s to 1984; (3) a cessation of blooms starting in 1985, with no recurrence; and (4) an increase, coincident with bloom declines, in the production of silver and bighead carp (filter-feeders) by more than tenfold. There are several possible explanations for the disappearance of blooms, including changes in nutrient concentrations, increased zooplankton grazing, and increased grazing on algae by fish. The long-term data suggest that changes in nutrients or in zooplankton were not important, but that the remarkably increased fish densities might have played the key role. To test this hypothesis, in situ enclosure experiments were conducted in three years. The main conclusions are as follows: (1) an increased stocking of the lake with carp played a decisive role in the elimination of cyanobacteria blooms; (2) both silver and bighead carp can eliminate cyanobacteria blooms directly by grazing; (3) zooplankton cannot suppress the blooms; and (4) the lake still is vulnerable to the outbreak of blooms, should fish grazing decline. The critical biomass of carp is approximately 50 g m 3. The results suggest the applicability of a new food-web manipulation (increased stocking with filter-feeding fish) for controlling cyanobacteria blooms in hypereutrophic lakes. The approach differs from traditional biomanipulation in Europe and North America, where piscivores are added to control planktivores, and this in turn increases zooplankton and decreases algae. The new biomanipulation method is being used or being tested to counteract cyanobacteria blooms in many Chinese lakes such as Lake Dianchi
in Yunnan Province, Lake Chaohu in Anhui Province, and Lake Taihu in Jiangsu Province. The method has great potential as an important component of an integrated approach to counteract cyanobacteria blooms, especially in lakes where nutrient inputs cannot be reduced sufficiently, and where zooplankton cannot effectively control phytoplankton production.
KEY WORDS: Cyanobacteria blooms, filter-feeding fish, biomanipulation, subtropical lake, silver carp, bighead carp, Microcystis, zooplankton
DOMAINS: freshwater systems, ecosystems and communities, ecosystem manage-ment, environmental management and policy
GENERAL FEATURES OF THE LAKE DONGHU ECOSYSTEM
Lake Donghu (30o33′N, 114o23′E) (Fig. 1) is located in Wuhan City, the capital of Hubei Province. It has a total surface area of 32 km2 and a surface that is ~21 m above sea level. The outlet of the lake joins the Yangtze River through the Qingshan Canal and is approximately 5 km from the river. The mean and maximum water depths are 2.2 and 4.8 m, respectively. Hydraulic residence time of the lake is ~0.4 y. The catchment area is ~97 km2.
In the latter half of the 1960s, Lake Donghu was divided into several sections by artificial dikes; Guozhengu Hu, Tanglin Hu, Hou Hu, and Niuchao Hu are the major lake sections. Since there remain only minimal interconnections, these sections are effectively isolated from each other. The Guozheng Hu (the site of sampling Stations I and II) is the most heavily impacted by anthropogenic nutrient inputs
Lake Donghu has multiple uses to society, including water supply, recreation, and commercial fishing. The lake is intensively used for fish production; stocking of the planktophagous silver and bighead carp increased the fish production more than tenfold in recent decades. The northwestern shoreline has a park and recreation area for the citizens of Wuhan, with museums, a botanical garden, observation towers, restaurants, swimming sites, and sight- seeing boats. There are approximately 100 factories (including a large steel plant) around the lake.
Dissolved oxygen concentrations in the lake water are often high. Super-saturation frequently occurs in the warm season, and nowhere is there an oxygen-free layer that might be insufficient for aquatic animals. The minimum monthly temperature (usually in January) varies from 2.6o to 4.6o C, and the maximum monthly temperature (usually in July) varies from 28.8o to 31.4o C[1]. Vascular aquatic plants are scarce in the lake, and their contribution to total system primary production is negligible[2]. Phytoplankton production, on the other hand, is very high. The dominant fish are the filter-feeding silver carp (Hypophthalmichthys molitrix) and bighead carp (Aristichthys nobilis). There also are some large piscivorous fish, but they occur at much lower densities. Research has indicated that fish grazing might significantly impact the lake’s plankton[3]. THE RISE AND FALL OF CYANOBACTERIA BLOOMS IN LAKE DONGHU
The annual average gross productivity of phytoplankton displayed a steady increase from the 1960s to early 1980s and then remained relatively stable (Fig. 2). The composition of the algal community also displayed marked changes in the 1950s and 1970s. In terms of individual numbers, in 1956 to 1957 Pyrrophyta ranked the first and Bacillariophyta were second; the two
FIGURE 1. Map of Lake Donghu, P.R. China, showing major sections of the artificially divided lake.
phyla constituted 60 to 70% of total algal density. Cyanophyta and Chlorophyta were far less abundant. After the 1960s, Cyanophyta and Chlorophyta increased in density and accounted for >50% of the total algae[5]. No data were available to estimate biomass of phytoplankton before 1979 (i.e., cells or colonies were counted, but not measured). However, we suspect that the relative biomass of Cyanophyta also increased dramatically because the taxa that became dominant (including Anabaena, Aphanizomenon, and Microcystis) occur as large colonies[1].
The most visible sign of cultural eutrophication in Lake Donghu was the outbreak of cyanobacteria blooms, with unsightly and odorous scum on the water surface every summer from the 1970s until 1984 (Fig.3). In 1985 blooms did not occur for the first time, and they have not re-appeared in the last 16 years. A comparison of the average proportion of annual biomass of dominant phytoplankton at two sampling stations of Lake Donghu in 1979–1982 vs. 1989–1992 indicates this change (Fig. 4). During 1979–1982, when heavy cyanobacteria blooms occurred in the summer of each year, colony-forming Microcystis and filamentous Anabaena and Oscillatoria dominated the phytoplankton. During 1989–1992, the dominant phytoplankton taxa were Cyclotella (a centric diatom) and Cryptomonas (a cryptomonad). Cyanobacteria were mainly comprised of Oscillatoria and Merismopedia[3]. These cyanobacteria do not generally form
noxious blooms.
FIGURE 2. Annual mean gross primary production at Stations I and II of Lake Donghu (adapted from Xie et al.[4]).
FIGURE 3. Cyanobacteria blooms in Lake Donghu on October 9, 1981 (photo by K. Tatsukawa).
FIGURE 4. Annual mean biomass (%) of dominant phytoplankton at two sampling stations of Lake Donghu between 1979–1982 and 1989–1992 (1979–1982 data from Wang[6]).
HISTORICAL CHANGES IN NUTRIENTS, ZOOPLANKTON, AND FISH Nutrients
Cultural eutrophication has occurred over the past decades in Lake Donghu[5,7,8]. Water samples collected at the mid-lake Station II indicate that ammonia nitrogen increased from 0.043 mg/l in 1957 to 0.361 mg/l in 1998. The mass stocking of fish has been suggested as a possible cause. However, neither feed nor fertilizer is applied to the lake for the stocked fish; the stocked fingerlings feed just like the wild population, solely on the food organisms naturally present, and then are removed from the water annually[1]. Hence, there probably is a net removal of nutrients from the lake by fish. In contrast, with the ever-increasing human population and rapid development of industry, agriculture, and animal husbandry in the drainage basin, larger amounts of nitrogen and phosphorous have been entering the lake each year in the form of semi-treated
effluents[5,7].
FIGURE 5. Annual mean concentrations of total dissolved nitrogen (TDN) and total dissolved phosphorus (TDP) at mid-lake Station
II of Lake Donghu during 1973–1998 (adapted from Tang and Xie[7]).
During the 1970s and 1990s, the concentrations of TDN and TDP showed great variation but no obvious downward or upward trends (Fig. 5) that might explain the changes in phytoplankton observed in that time period. Likewise, the ration of TDN to TDP did not systematically vary.
Zooplankton
Densities of protozoa, rotifers, copepods (including nauplii), and cladocerans were evaluated from 1956 to 1996 (Fig. 6). Although protozoan densities varied from year to year, they did not systematically increase or decrease. Densities of rotifers, cladocerans, and copepods all peaked in the early 1980s, and then declined greatly. The copepods were mainly comprised of predaceous cyclopoids, while the herbivorous calanoids are relatively low in numbers. Before 1987, two large-bodied species, Daphnia galeata and Daphnia carinata, dominated the cladoceran community. Later, these species were replaced by the smaller Moina micrura. The population of Diaphanosoma brachyurum, an intermediate-sized cladoceran, remained rather stable[4]. Because declines in large cladocerans occurred in approximately the same time frame as the disappearance of cyanobacteria blooms, one cannot attribute the loss of blooms to increased zooplankton grazing. Rather, one might presume that some common factor led to the zooplankton
changes and bloom demise.
FIGURE 6. Annual mean densities of total Protozoa, Rotifera, Copepoda (including nauplii), and Cladocera at Stations I and II of Lake Donghu (adapted from Xie and Yang[9]).
Fish
Commercially harvested fish constitute the major part of the fishery in Lake Donghu[1]. The state-owned Donghu Lake Fish Farm was established in 1951, and since 1971 it has stocked the lake every year with mainly planktivorous filter-feeding silver and bighead carp. As indicated, the carp are not provided with fertilizer or other food sources, but rather, they feed on natural food items available to them in the lake water. In the 1950s and 1960s, the annual fish yield of Lake Donghu varied from 39 to 178 kg/ha, with a mean of 92 kg/ha (Fig. 7). During 1972–1978, a series of measures were taken to increase the fish yield of the lake. These included increasing the stocking density and the proportion of large-sized (>13 cm) fingerlings (Fig.7), reconstructing the fish screens, controlling the predatory fish[10], and adopting the method of bulk harvesting (Fig. 8). Of the total stocked fingerlings during the periods 1973–1978 and 1983–1997, silver carp constituted 46.5% (range 28.4–73.4%), bighead carp constituted 40.3% (range 18.4–63.2%), and a smaller percentage was of other fish.The annual fish yield increased steadily from 124 kg/h in 1971 to 1,068 kg/ha in 1997 (Fig. 7). From the 1970s on, more than 85% of the total fish yield was comprised of stocked species, especially in recent years, when >90% was from silver and bighead carp[11]. Taking into account the annual fish yield, the exploitation rate by the fishmen[12], and the daily ration of the fish[13], the estimated fish biomass in the lake is several times higher than that of the total plankton.
Grazing pressure by the planktivorous fish should be rather strong in the lake[3,4,9].
FIGURE 7. Annual fish yield and the number of stocked fingerlings (A), the percentage composition of the fish yield (B), the number of the stocked silver carp fingerlings of different sizes (C), and the number of the stocked bighead fingerlings of different sizes (D) (adapted from Xie et al.[4]). Stocking with fish-fry before the 1970s resulted in poor fish yield.
EXPERIMENTAL STUDIES
To clarify the possible role of silver and bighead carp in the disappearance of cyanobacteria blooms from the lake since 1985, in situ enclosure (2.5 × 2.5 × 2 m) experiments were conducted in 1989, 1990, and 1992. The detailed results have been published elsewhere[14,15,16,17], so a general summary is provided here.
First Experiment — 1989
This experiment was performed in order to determine (1) how the stocking of silver and bighead carp influences the community structure of phytoplankton, and (2) if dense stocking of these fish could eliminate a cyanobacterial bloom. Eight 2.5 × 2.5 × 2 m deep enclosures were set up in the Shuiguo basin of the Guozheng Hu section of the lake in May 1989. Only three of the eight enclosures could be used because strong winds destroyed the others. The enclosures of polyethylene sheets were open to air above and in direct contact with sediment underneath. The
volume of the water in each enclosure was about 12.5 m3.
FIGURE 8. The harvested silver carp and bighead (lower left), the bulk harvesting by the fishermen (lower right), testing of echo-sounder ashore a fish pond (upper left) by scientists to estimate fish population of the lake, and the artificial dikes across Lake Donghu (upper right) (photos by K. Tatsukawa).
After initial sampling on May 17, six fish of both species were introduced into enclosure 3, twelve bighead carp into enclosure 5, and no fish were added to enclosure 7. The average individual weights at stocking were 75 g for silver carp and 380 g for bighead carp. The introduction of fish resulted in dramatic changes, not only in the total algal volume but also in the dominance of certain taxa in the phytoplankton community (Fig. 9). In terms of average algal volume, the dominant phytoplankton in the fish-stocked enclosures and the lake were quite similar, i.e., Cryptophyceae (mainly Cryptomonas) ranked first, Bacillariophyta (mainly Cyclotella) second, and Chorophyceae third. However, the situation in the fish-free enclosure 7 was quite different, where a bloom of Microcystis appeared after mid-June and persisted throughout the experiment. Despite the lack of replication, the dramatic differences in treatments and similar responses of the experimental units to what had been observed historically in the lake supported the hypothesis of fish control of phytoplankton blooms.
Second Experiment — 1990
After the finding of a cyanobacteria bloom in the fish-free enclosure in 1989, a second experiment was conducted in order to (1) induce water blooms in more enclosures, (2) introduce silver and bighead carp to the enclosures with blooms to determine if the fish could graze down
the algae, and (3) monitor changes in the size structure of the phytoplankton biomass.
FIGURE 9. Changes in the biomass of Microcystis and other phytoplankton in the enclosures and the surrounding lake water in Lake Donghu during May-October, 1989 (adapted from Xie and Liu[14]).
Six enclosures were used with the same location and design as in the previous year. Initial sampling was done on April 5. On the next day, four silver carp and two bighead carp were introduced into enclosures 3 (average weight 21g/ind. for silver carp and 32 g/ind. for bighead) and 4 (average weight 23 g/ind. for silver carp and 32 g/ind. for bighead). The other enclosures were not stocked with fish. There were pronounced phytoplankton responses to the treatments, both in terms of total biomass (measured as chlorophyll a) and biomass of small phytoplankton (measured as chlorophyll a in 30 μm filtered water) (Fig. 10). In the enclosures stocked with fish (3 and 4), total chlorophyll a remained low throughout the experiment, and, on the average, more than 80% of the biomass was attributed to small taxa. During April and May the enclosures with fish displayed a similar situation in terms of chlorophyll a. However, dramatic changes followed.
A bloom was observed in enclosure 2 in mid-June, in enclosures 1 and 5 in late-June, and in enclosure 6 in mid-July. With the appearance of blooms in these fish-free enclosures, the dominant phytoplankton shifted to Microcystis. These results confirmed the findings of the 1989
study. On July 20, after water samples were taken for phytoplankton analysis, six silver carp
(average weight 148 g/ind.) were introduced into enclosure 1, six bighead carp (average weight 176 g/ind.) into enclosure 2, and three silver carp (average weight of 152 g/ind.) plus three bighead carp (average weight 172 g/ind.) into enclosure 5. No fish were stocked into enclosure 6 throughout the experiment. The introduction of fish caused drastic declines in the total biomass of phytoplankton in enclosures 1, 2, and 5. In enclosure 1, the cyanobacteria bloom disappeared within 10 days, and in enclosures 2 and 5, blooms disappeared 18 days later. In all cases the dominant phytoplankton shifted to <30 μm taxa. In the fish-free enclosure (6), the cyanobacteria bloom persisted throughout the experiment.
FIGURE 10. Changes in chlorophyll a amount in both total phytoplankton and those <30 μm phytoplankton in enclosures and the surrounding lake water in Lake Donghu during April-August, 1990 (adapted from Xie and Liu[15]).
Third Experiment — 1992
A third experiment addressed the question of whether a different fish (grass carp— Ctenopharyngodon idellus) could have similar effects on phytoplankton blooms. In this case the treatments included: (1) two planktivorous carp at different densities stocked into enclosures with resurgent blooms; (2) grass carp stocked into enclosures with blooms; and (3) monitoring of responses in terms of phytoplankton biomass and size, as above. A total of eight enclosures were used (two per treatment, plus controls) at the same location as in previous years. The experiment was carried out during July–September. The lake water was isolated in the enclosures on July 6, and the first sampling was made on July 7. At the beginning of the experiment, no blooms occurred. Two weeks later, a thin water bloom of mainly green algae appeared in most of the enclosures. Subsequently, the dominant taxa changed to cyanobacteria, mainly Microcystis. By the end of July, a dense Microcystis bloom occurred in most enclosures, and by mid-August, all enclosures had this condition. As noted previously, the open lake did not support cyanobacteria blooms at this time in its history. On August 21, three grass carp were stocked into enclosure 3 (average weight 187 g/ind.) and 4 (average weight 229 g/ind.), three silver carp into enclosure 5 (average weight 137 g/ind.), two silver carp (average weight 133 g/ind.) into enclosure 6, and four bighead carp into both enclosures 7 (average weight 233 g/ind.) and 8 (average weight 216 g/ind.). No fish were stocked into enclosures 1 or 2. The introduction of bighead carp to enclosures 7 and 8 caused dramatic declines in total phytoplankton biomass (Figs. 11, 12), and about two weeks later, the cyanobacteria blooms disappeared. The introduction of silver carp to enclosures 5 and 6 also decreased phytoplankton biomass, but there was still a bloom in these enclosures at the end of the experiment. The introduction of grass carp to enclosures 3 and 4 did not reduce phytoplankton biomass, and dense blooms persisted until the end of the experiment. In the fish-free enclosures, heavy blooms also persisted. Changes in the size structure of phytoplankton were variable among the enclosures. In the fish-free enclosures and the enclosures stocked with grass carp, phytoplankton biomass was dominated by the larger (>30 μm) size class. In enclosures stocked with the planktivorous fish (silver and bighead carp), phytoplankton biomass was dominated by the smaller (<30 μm) fraction, especially at higher fish densities. There have been contradictory reports in the literature on the impact of silver carp on phytoplankton. Through enclosure experiments in a small Polish lake (Lake Warniak), Kajak et al.[18] found that silver carp reduced blue-green algae and total phytoplankton biomass while increasing the proportion of dinoflagellates and nano-plankton. However, it also was reported that silver carp stimulated phytoplankton and might be ineffective for the control of algal blooms[19,20,21]. Our results provide strong support for the view that the latter conclusion is not always valid and that, in fact, silver and bighead carp are highly effective in controlling noxious blooms of algae.
Summary of Experimental Results
Based on the results of the three in situ enclosure experiments, the following conclusions are reached: (1) the increased stocking of the filter-feeding silver and bighead carp played a decisive role in the elimination of water bloom from Lake Donghu after 1985; (2) the lake remains vulnerable to the outbreak of Microcystis blooms; and (3) both silver and bighead carp can eliminate cyanobacteria blooms directly by grazing. Our results also indicate that zooplankton cannot suppress the blooms in this lake. When the experimental results are integrated with echo-sounding records of fish biomass and the fishery production of the lake over the years, it is concluded that the recurrence of blooms can be prevented if the biomass of silver plus bighead carp is held at or above ~50 g/m3.
FIGURE 11. Changes in chlorophyll a amount in both total phytoplankton and those <30 μm phytoplankton in enclosures and the surrounding lake water in Lake Donghu during July–September, 1992 (adapted from Xie et al.[16]).
DIGESTION OF CYANOBACTERIA BY SILVER AND BIGHEAD CARP
Another issue that has been a subject of debate is the digestibility of cyanobacteria grazed by silver and bighead carp. Examinations of gut contents from silver carp in a culture pond indicated that most of the algae present appeared intact in both the fore- and hind-gut[22,23,24]. A prerequisite to the utilization of the cell contents is breakdown of the algal cell wall by one of three mechanisms, i.e., acid hydrolysis, enzymatic digestion, or mechanical trituration[25]. In filter-feeding fish with no stomachs, such as silver carp, the pH of the gut fluids usually is >6. No cellulase in the gut of silver carp was found[26], and in vitro incubation of a filamentous cyanobacterium (Anabaena flos-aquae) with digestive juices of silver carp resulted in only 10% of the algal protein being hydrolyzed to free amino acids[24]. It was concluded that silver carp
are omnivorous rather than herbivorous[25,26].
FIGURE 12.Microcystis blooms collected from the surface of enclosures 3 and 7 on September 2. On August 21, 932 g of bighead carp was stocked into enclosure 7, while 561 g of grass carp was stocked into enclosure 3.
Xie[27] examined the process and digestion of the centric diatom Cyclotella in the alimentary canal of silver carp. The results indicate that 67% of the cells was damaged as a result of ingestion and digestion by silver carp, of which as much as 52% occurred in the esophagus while only 15% could be attributed to digestion in the intestine. In other words, mechanical crushing of a sufficient proportion of ingested algal cells occurred apparently as a result of grinding by the pharyngeal teeth in the esophagus. Similar results were obtained for bighead carp[28].
On the other hand, studies using radioisotope techniques indicate that silver carp digests green algae and cyanobacteria efficiently. Using cultured Anabaena flos-aquae labeled with 14C, silver carp fry ingested 10–13% of their body weight per day, and 17% of the ingested algae was assimilated[29]. Using cultured, 14C-labeled green algae as food, silver carp were found to assimilate 42% of Closterium and 14% of Selenastrum[30]. A series of tracer experiments using Anabaena spiroides collected from a fish pond and then labeled with 32P indicated that silver carp ingest algae at a rate of 12–22% of their body weight per day, and that 65% of the ingested material is assimilated[31]. Tracer experiments with 32P also indicate that silver carp assimilate 35–48% of ingested Microcystis aeruginosa, 17–36% of Euglena, and 44–60% of Scenedesmus obliquus[32,33]. Similarly, bighead carp assimilate 23–38% of ingested Microcystis aeruginosa and 25–53% of Euglena sp.[33].
Based on these results, the feeding mechanisms of silver carp are summarized as follows. The breakdown of cell walls of ingested algae mainly takes place in the esophagus by mechanical grinding by pharyngeal teeth[27]. Some algal cells remain intact, with the proportion varying among species. On passage through the intestine, few or only a very small proportion of the intact
algae are destroyed, especially those algae with cellulose cell walls such as green algae, due to the
lack of cellulase in the intestine. This explains the erroneous conclusion by some authors that stomachless fish do not use algae as a food resource[22,24,25,26]. Assimilation of the contents of broken algal cells takes place in the intestine even though the intact algal cells may change little in their proportion on passage through that organ, explaining the effective assimilation of silver carp on some cyanobacteria and green algae observed with isotope techniques. The presence of intact or mobile alga in the hind-gut or feces[22,23,24] does not necessarily mean that the species are indigestible, since Xie[27] shows that only one third of the ingested Cyclotella remained intact in the feces. The incomplete digestive mechanism on algae may reflect an adaptive strategy for stomachless filter-feeding fish that continuously feed on small, suspended particles including not only plankton but also large amounts of organic detritus of low nutritional value. A similar mechanism also occurs in bighead carp[28].
POTENTIAL FOR USE OF SILVER AND BIGHEAD CARP TO CONTROL CYANOBACERIA BLOOMS
Measures for the Control of Cyanobacterial Blooms
There are several commonly used measures to counteract cyanobacteria blooms in hypereutrophic lakes[34]. These include: (1) chemical algicides, especially copper sulfate; (2) nutrient input reduction and manipulation (e.g., N:P ratios); (3) vertical de-stratication through mechanical mixing or bubbling; (4) enhanced water flushing to reduce retention time; and (5) biological control. Option 1 is neither practical nor advised in larger ecosystems or any waters to be used for fishing, drinking, and other animal and human use, since algicides may have toxic effects to non-target species. Option 2 is the most commonly used and the method with the longest history in lake management. However, it is expensive and, in certain cases, where much of the input is from non-point sources, difficult to achieve in an effective manner. Some shallow lakes with high internal nutrient loading also do not respond for long time periods to external load reductions. Option 3 may be used in small, relatively shallow (i.e., <5 m) systems. Option 4 may be possible if abundant water supplies (i.e., upstream reservoirs) are available for flushing. Biological control (5) still is in an experimental stage but has been effectively applied to a number of lakes. It involves modifying the biological community in a manner that results in increased grazing pressure on the cyanobacteria. A common (traditional) biomanipulation approach is one where piscivorous fish are added to a lake in order to reduce the abundance of zooplankton-eating planktivores. This allows large-bodied zooplankton like Daphnia to increase, and with their increased grazing the biomass of phytoplankton is reduced. There is some controversy about the general applicability of this method of biomanipulation.
Limitations of Traditional Food Web Biomanipulation
Limnologists traditionally considered pelagic communities to consist of components linked through a unidirectional flow of influence from nutrients ! phytoplankton ! zooplankton ! fish[35]. In the 1970s, it was recognized that a significant reduction of zooplanktivorous fishes through enhancement of piscivorous fish could result in higher densities of zooplankton and consequently a substantial decline in algal biomass by zooplankton grazing[36,37]. Further experimental work by Shapiro et al.[38] led to subsequent investigations of this method of biomanipulation. This traditional approach (Fig. 13) may be effective in lakes that are not heavily enriched with nutrients, and with algae composed of small species. However, it may not be as applicable in hypereutrophic lakes, which tend to have large algae and sometimes only small zooplankton.
FIGURE 13. Conceptual diagram of traditional biomanipulation for the control of algal blooms.
The typical algal dominants may have (in addition to large size) defenses against grazers such as gelatinous or hard sheaths, and some produce toxins. It is reported that cyanobacteria blooms often are associated with a decline of zooplankton biomass and replacement of dominant zooplankton by smaller species of cladocerans, copepods, or rotifers[39,40,41,42,43]. It also is known that increased grazing pressure by zooplankton can shift the phytoplankton community toward large taxa, with little or no net change in total algal biomass[44,45,46].
Advantages of Biomanipulation with Filter-feeding Fish
By manipulating the abundance of filter-feeding silver and bighead carp, we have been successful in eliminating heavy cyanobacteria blooms from hypereutrophic Lake Donghu for a period of 16 years. This practice disclosed the applicability of a new food-web manipulation, i.e., it is quite possible to eliminate the unsightly and odorous cyanobacterial blooms in hypereutrophic lakes by increasing the filter-feeding silver and bighead carp through stocking (Fig. 14). In contrast to particle-feeding fish that visually select individual prey items (primarily larger zooplankton)[47], filter-feeders collect food by passing water through their filtering apparatus, feeding on phytoplankton (usually >10 um), suspended detritus, and also zooplankton if they are unable to evade the fish. In this sense, silver and bighead carp are not only zooplanktovores but also algivores. This new method of biomanipulation is being used or tested to counteract cyanobacteria blooms in many Chinese lakes, including Lake Dianchi in Yunnan Province, Lake
Chaohu in Anhui Province, and Lake Taihu in Jiangsu Province.
FIGURE 14. Conceptual diagram of the new biomanipulation by using filter-feeding silver and bighead carp to counteract cyanobacteria blooms.
Silver and bighead carp are native to eastern Asia[48]. Silver carp occur in rivers and lakes of China, North Vietnam, and Siberia. The natural range of bighead carp is smaller. This fish is found in China, from the Yellow River in the north to the Pearl River in the south. Silver and bighead carp contribute greatly to the world catch of freshwater fish (Fig. 15), and have been cultured for centuries in mixed cultures with other fish species, increasing total yield due to utilization of primary production. Since the 1960s, silver and bighead carp have also been introduced worldwide (Fig. 15). It is relatively easy to regulate the population size of the carp since they cannot reproduce naturally in lakes. In other words, if the stocking is stopped, the fish will decline gradually. Hence there may be great potential for using silver and bighead carp to counteract the worldwide problem of cyanobacteria blooms in hypereutrophic lakes. The successful practice in Lake Donghu suggested the possibility of this new biomanipulation as an important component of an integrated approach to counteract cyanobacteria blooms, especially in
circumstances when nutrients cannot be reduced sufficiently.
FIGURE 15. (A) Proportions of silver carp and bighead in the world's total catch of inland waters in 1989 (data from FAO[49]), and (B) a summary of introduction of silver carp and bighead carp in the world (data from Welcome[50]).
ACKNOWLEDGMENTS
We wish to give our deep thanks to Dr. K. Havens for his many valuable comments on the manuscript. Prof. Y.F. Shen of the Institute of Hydrobiology, CAS, also gave useful suggestions on this manuscript. Thanks are also due to all the members of the Donghu Experimental Station of Lake Ecosystems for their assistance in carrying out the field work. This work was mainly supported both by the Key Project of CAS (No. KZCX2-403) and the State Key Basic Research and Development Plan (G2000046800). Facilities of the Donghu Experimental Station and the State Key Laboratory for Freshwater Ecology and Biotechnology of China were used in this study.
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_________________________________________________________________________________________________ This article should be referenced as follows:
Xie, P. and Liu, J. (2001) Practical success of biomanipulation using filter-feeding fish to control cyanobacteria blooms. TheScientificWorld 1, 337-356.
Handling Editor:
Karl E. Havens, Principal Editor for Freshwater Systems – a domain of TheScientificWorld.
_________________________________________________________________________________________________
1、名词： 中心法则：首先由Crick于1958年提出，是遗传信息传递的一般规律，遗传 信息可由DNA复制而遗传，由转录、翻译而产生功能产物，信息也可由反转录从RNA进入DNA。 Gene：产生功能性产物（RNA或者蛋白质）所必需的全部DNA序列。 重叠基因：两个或者更多基因使用同一DNA区段作为编码序列，这种形式的基因称为重叠基因。 断裂基因：基因的编码区被非编码序列分隔开来，编码区呈断裂状态，称为断裂基因。 基因重复：在同一个基因组内存在2个或者2个以上拷贝的同源基因序列。Exon：外显子，DNA 与成熟RNA间的对应区域。 Intron：位于基因编码序列之间，与编码序列同时转录转录，但是在随后加工形成成熟RNA的过程中被去除的序列。 C值：是指真核生物细胞中,单倍细胞核(受精卵或二倍体体细胞中的一半量)里所拥有的DNA含量。 C值反常现象：指一个关于真核生物各物种的基因组大小差异的难题，也就 是生物的C值（或基因组大小）并不与生物复杂程度相关的现象。例如植物与原生动物，可能具有比人类更大的基因组。 Genome：基因组，特定生物体单倍体细胞中遗传物质的总和。 1、名词 切刻（nick）：双链DNA的一条单链出现磷酸二酯键的断裂，称为切刻或者切口。nick translation：切刻平移，是DNA聚合酶同时行使5’→3’聚合和5’→3’外切功能，导致双链DNA切刻超3’端移动的现象，可用于DNA的同位素标记。Klenow 片段：也称为Klenow酶，是DNA聚合酶I经蛋白酶处理后形成的羧基端大片段，具备5’→3’聚合和3’→5’外切活性。 端粒：线性染色体的末端，由一段富含G的正向重复序列（共有序列为TxGy）与相应的端粒结合蛋白共同组成 端粒酶：是一类核糖核蛋白体（ribonucleoprotein ，RNP），实质是自带RNA 模板的反转录酶，其模板能与端粒DNA的3'凸出端配对，以端粒DNA的3'-OH 起始端粒DNA的延长。 重组：DNA分子间或DNA分子内部的DNA片段的重排或交换。 转座子：是DNA上可自主复制和位移的基本单位。狭义上也专指DNA转座子，直接以DNA的形式在基因组中发生位移的DNA元件。 返座子：是能通过转录形成的RNA进一步反转录后插入到染色体DNA中的一
对水体中藻类的正确认识及合理科学利用 总述：正确认识藻类:藻类是水体的初级生产者，是水体中物质循环最重要最关键的一个环节，也是水体生产力的体现，明确藻类生长繁殖的生态意义。控藻是要让藻类在水体中生长繁殖，通过生态系统食物链的更高一级来消化生长繁殖的藻类；通过精准地对于目标水域进行水生动物特别是鱼类的控制来调整水体水生动物生物种群数量与群落总量，准确地控制水体中藻类的总量。这对恢复水域生态系统和治理水体富营养化都有着极其重要的意义。 一、对于藻类的认识 平常我们一提到藻类，首先想到的是水体的富营养化现象，想到的是“蓝藻”的爆发，“水华”的发生，“藻毒素”对于人体的危害等等。这实际上是我们对藻类的一个很偏面认识，而事实上： 1、藻类是水体的初级生产力，是水体生产力的体现。 浮游藻类在水域生态系统中属于初级生产者，体内具有叶绿素，通过光合作用等将CO2、水体中的氮磷等无机物转变为葡萄糖等有机物，供其他次级消费者利用，这在水生态系统中具有重要的地位。浮游藻类是水域生态系统食物链的开端，是无机环境与有机环境的承接者，对物质循环和能量转化起着重要作用。它们提供氧气、提供饵料、物质转化。 浮游藻类是水域生态系统食物链中非常重要的环节，所有高等水生生物的生存最终依靠藻类的存在。 2、藻类是自然界物质循环最为重要的一个环节。 从藻类的分子式近似地为C106H263O110N16P（藻类原生质）可以看出，自然界的碳、氮、磷的循环都得依靠藻类来完成，藻类在自然界中是很重要的一类物质。“8种科学的末日预言”中的第四条预言就是关于藻类的：藻类危机（有某一日，地球上的硅藻不利用太阳能将水形成氧气与氢气而是变种不能利用水分子或者其他的替代物，它有可能转化为利用盐为原料时，结果释放出氯气，没多少年就足以毁掉整个地球。），这足见藻类在自然界的重要性。 3、了解藻类生长的关联因素。 温度、水体的PH值、水体中的氮、水体中的磷、光照等等都对藻类的生长繁殖有关联。其中的温度、水体的PH值、光照等等都是自然界的因素，都不是人为可以控制的。水体中的氮磷与人类活动有很大的关系，但是水体中的氮磷的含量高低不是决定水体藻类爆发的直接因素。营养物质含量的多少只是提供了一个“后缓支持”而已。控制水体中的营
原文标题：Xie, P. and Liu, J. (2001) Practical success of biomanipulation using filter-feeding fish to control cyanobacteria bloom s – a synthesis of decades of research and application in a subtropical hypereutrophic lake. TheScientificWorld 1, 337-356. 全文翻译如下：用滤食性鱼类控制蓝藻水华的生物操纵理论在实践上的成功——对一亚热带超富营养型湖泊中数十年研究和应用的综合 谢平刘建康 中国科学院水生生物研究所东湖湖泊生态系统试验站、 淡水生态与生物技术国家重点实验室 Email: xieping@https://www.doczj.com/doc/6b13840846.html,; liujk@https://www.doczj.com/doc/6b13840846.html, 收到：2001. 6.11; 修改：2001.6.25; 接收：2001. 6.25; 出版：2001. 8.8 东湖靠近中国长江，面积32平方公里，属于一个亚热带浅水湖泊，在过去五十年中东湖经历了若干巨大的变化，包括：（1）营养状况由中营养型转变为富营养型；（2）从上世纪70年代至1984年爆发了严重的蓝藻水华；（3）从1985年起蓝藻水华开始消失，而且不再发生；（4）鲢鳙鱼的产量比以前增加10倍多，随之而来蓝藻水华消失。对于蓝藻水华消失有几种可能的解释，包括：营养盐的变化，浮游动物对藻类牧食压力的增加，鱼类对藻类牧食压力的增加。长期变化的数据表明营养盐和浮游动物的变化是不重要的，而鱼类密度的显著增加可能起了关键作用。为了验证这些假设，在东湖进行了3年原位实验，主要的结论如下：（1）东湖中增加鲢鳙鱼的放养在消除蓝藻水华中起了决定性作用；（2）鲢鱼和鳙鱼均能通过牧食直接消除蓝藻水华；（3）浮游动物不能抑制蓝藻水华；（4）如果鱼类牧食压力下降，东湖仍可能爆发蓝藻水华，消除水华所需的鱼类临界的生物量约为50克/立方米。研究结果表明了在超富营养湖泊中应用一种新的食物链操纵理论（增加滤食性鱼类的放养）来控制蓝藻水华的可行性。本研究中采用的方法与欧洲及北美的经典生物操纵理论不同，经典的生物操纵理论是通过增加食鱼性鱼类来控制食浮游动物的鱼类，进而增加浮游动物来控制藻类。用这种新的生物操纵理论来抑制蓝藻水华正被许多中国湖泊如云南滇池、安徽巢湖和江苏太湖等利用或验证。该方法作为控制蓝藻水华爆发的综合方法之一特别是对于那些营养盐输入不能被有效减少或浮游动物不能有效控制藻类生产力的湖泊具有很大的潜力。 关键词：蓝藻水华、滤食性鱼类、生物操纵、亚热带湖泊、鲢鱼、鳙鱼、环境管理和政策领域：淡水生态系统、生态系统与群落、生态系统管理、环境管理和政策 东湖生态系统的一般特征 东湖（30 o 33’，1114 o 23’）（图1）位于湖北省省会武汉，面积32平方公里，海平面高度21米。东湖距长江约5公里，通过青山港与长江相通。湖泊平均水深与最大水深分别为2.2米和4.8米，湖水滞留时间为0.4年，流域面积97平方公里。 在上世纪60年代后半期，东湖被人工堤岸分割为几个部分，其中，郭郑湖、汤林湖、后湖和牛巢湖为几个主要的湖区。由于仅有小水道相连，几个湖区保持了相对的独立。郭郑湖（采样点I和II）是被人为营养盐输入影响最严重的湖区。 东湖具有多功能性，包括供水、娱乐和商业渔业。湖泊被用来养鱼，食浮游动物的鲢鳙鱼产量在近几十年增加了十倍以上。湖泊的东北沿岸是武汉市的公园和娱乐场所，同时还有博物馆、植物园、了望塔、旅馆、游泳池和观光船。湖泊沿岸大约有100多家工厂（包括一个大型钢铁厂）。 湖水中的溶氧一般是很高的，在暖和的季节里溶氧过饱和现象经常发生，一般不致造成
第10卷 第8期 中 国 水 运 Vol.10 No.8 2010年 8月 China Water Transport August 2010 收稿日期：2010-05-17 作者简介：宋益峰（1978-），浙江海盐人，学士，上海市金山区水文站助理工程师，主要从事水环境监测与治理研究。 我国典型浅水湖泊蓝藻水华治理技术研究进展 宋益峰1 ，兰 林2 ，吴 江3 （1上海市金山区水文站，上海 201508；2江苏省水利厅，江苏 南京 210029； 3太仓市环境监测站，江苏 太仓 215400） 摘 要：蓝藻水华成为我国浅水湖泊的重大水环境问题。根据蓝藻水华的形成机制，采取相应控制技术减少其带来的影响具有重要的生态和环境意义。文中综述了目前我国典型浅水湖泊蓝藻水华治理中物理控制法、化学控制法、生物控制法的研究进展。 关键词：浅水湖泊；蓝藻水华；治理技术 中图分类号：X524 文献标识码：A 文章编号：1006-7973（2010）08-0154-02 一、前言 我国目前66%以上的湖泊、水库处于富营养化的水平，其中重富营养和超富营养的占22%，富营养化成为我国湖泊目前与今后相当长一段时期内的重大水环境问题[1]。与湖泊富营养化相伴随的一个普遍现象就是蓝藻水华[2]，蓝藻水华广泛地存在于淡水生态系统中并产生一系列严重的水环境问题[3]。蓝藻水华控制是世界性难题[4~6]，迄今采用的控制蓝藻水华的技术有几种：物理控制法、化学控制法和生物控制法。 二、蓝藻物理强化控制技术 1．机械除藻技术 机械除藻技术包括移动式富集湖面蓝藻“水华”技术、气浮捕集蓝藻“水华”技术。沈银武等[7]利用振动重力斜筛、旋振筛和卧螺离心脱水方法，在单机运行的条件下，在滇池于2001年4月和9月的145天中开机1,700h，共收获富藻水17,000m 3，折合干重为325t。试验区收获的蓝藻干粉经检测其平均总氮(N)为8.51％；总磷(P)为0.49％、总钾(K)0.70%和粗有机物43.47％。依此结果计算，相当于从试验区取出氮(N) 27.66 t、磷(P) 1.6t、钾(K ) 2.28 t 和粗有机物141.28t。有效降低了富营养化湖泊的氮、磷等水平和减轻或缓解了大量暴发的蓝藻生物量。 2．水动力控藻技术 吴张永等[8]对流体动力处理蓝藻技术进行了前期室内试验研究，发现实验条件下除藻率可达100%，且不会对水体造成二次污染。太湖在闾江口到马山岛之间马围长堤附近修建马山大桥，把大堤打通，沟通马山西的太湖与梅梁湖、贡湖、五里湖的水流，促使流入口袋的水流，从袋底顺利流入西太湖，促使湖水在夏季向西北部分流，冬季西太湖水流灌入两湖以冲洗滞水。如此可把两湖与西太湖整体形成循环水流，以使湖水通过自净、分流促使快速换水，抑制蓝藻暴发。 3．超声波控藻技术 超声波技术是近年来发展起来的一种新型的环境技术，被称为环境友好技术[9]，具有操作和控制容易，便于引进自动化操作手段，在处理中不引入其他化学物质，而且反应条件温和，反应速度快等优点。功率超声在水体中空化效应产 生的高压、冲击波、声流和剪切力能够有效破坏藻类的细胞结构，抑制叶绿素的合成，降低蓝藻细胞类囊体膜上藻胆蛋白和某些酶的活性。目前有研究将超声波技术应用于自然水体，通过超声短时间的辐照抑制水体中藻类的生长，从而达到控制水华爆发的目的[10]。 三、太湖蓝藻化学强化控制技术 1．湖底充气扬水筒技术 扬水筒技术，将积聚于表层的藻类驱赶至水库底层，由于光照极低以及温度骤降等原因，藻类失去活性而逐渐消亡，并能显著降低水库底层铁、锰浓度。在荷兰阿姆斯特丹Nieuwe Meer 水库中，扬水筒技术实施结果得到证明：其生物量降低为未处理前的1/20，藻类种群结构也由原先以蓝藻为主转变为硅藻、绿藻为主；此外整个水体中的溶解氧浓度可一直维持在5mg/l 左右，从而扩充了鱼类的生存空间。 2．黏土除藻技术 黏土除藻华技术最早来源于絮凝原理，曾被作为在海洋赤潮暴发时的一种应急技术，取得了一定的效果。早在1997年，就有专家在国际权威科学期刊《自然》上撰文指出，使用黏土除藻可能是治理藻华的最有发展前途的方法。但由于絮凝除藻机理不清、黏土投量太大、藻华复发和二次污染等问题，许多将黏土除藻技术应用于淡水湖泊中清除藻华的尝试一直没有成功，其技术定位为应急措施。 潘纲等[11]通过改性黏土的快速除藻除浊作用启动并强化沉积物中的生物地球化学反应使其自动地进行长期连锁的健康修复过程，发展了既能快速消除水华又能长期治理湖泊富营养化的一系列改性黏土技术。通过对26种不同黏土与藻细胞之间多项絮凝性质的研究发现高效黏土絮凝除藻的黏土架桥网捕作用，根据上述科学发现在架桥网捕性能方面对黏土进行改性，结果改性后的黏土不仅特别适合于淡水藻华的清除，而且黏土的投入量也从国际先进的200mg/l，降到了10mg/l，除藻效率达到95％以上。这种环境友好的天然改性剂可以使各种原先不具有除藻能力的当地黏土/沉积物变成高效除藻剂。 3．化学除藻剂
罗非鱼治理蓝藻水华研究 尹春华,宣劲松,吕乐,闫海 (北京科技大学应用科学学院生物科学与技术系,北京100083) 摘要 [目的]为有效控制蓝藻水华污染提供方法支持。[方法]通过现场设置围隔研究利用罗非鱼控制蓝藻水华污染的效果。[结 果]投放罗非鱼后水体中蓝藻颗粒浓度在5d 后下降到4.0@105/m ,l 而空白对照组(C K)蓝藻颗粒浓度基本维持在1@106 /m l 。与CK 相比,投放罗非鱼组水体中亚硝酸氮下降迅速,4d 后降低到0.02mg/L 。罗非鱼对水体中硝酸氮和磷酸根的去除作用更为显著,分别在2d 后和4d 后降低到基本检测不出。对于水体中氨氮的浓度,罗非鱼的影响则不明显。[结论]高密度投放罗非鱼能显著减少水体中的蓝藻,迅速降低水体中硝酸氮、亚硝酸氮和磷的含量。关键词 蓝藻水华;罗非鱼;控制中图分类号 S931.1 文献标识码 A 文章编号 0517-6611(2009)23-11112-03Study on C o n trolli ng C yanobacter i a B loo m with T ilapia YIN C hun 2hua et a l (Depart ment ofB i ol ogi cal Sc i ence and Technol og y ,Coll ege ofApplied Sc i ence ,Univ ersit y of Sc i ence and Technol og y Beiji ng ,Be iji ng 100083) Abstr act [Objecti ve]The purpose was t o supplym et ho dol ogi cal support f or co ntrolli ng the poll uti o n caused by cyano bact er i a bl oo m effec 2ti vely .[Method]The eff ect of controlli ng t he poll uti o n caused by cyanobacteri a bl oo m wit h tilapia was st udi ed t hroug h setti ng enc l osures on site .[R es ult]After t he til ap i as were put i ntowater ,the co ncn .of cy anobacteri a particleswas decreased to 4.0@105 a fter 5d .The co ncn . of cyano bact er i a particles i n t he control group (CK)was kept above 1@106 /m l basica ll y .The concn .of nitrite nitro gen i n t he wa t erbo dy of the tilapia group was 0.02mg/L after 4d ,which decreased more quick than that of C K .The concn .of nitrate nitrogen and phos phate radica l i n t he wa t erbo dy aft er til api as were putti ng i nt o was decreasedmore sig nifi cantl y ,wh i ch coul d not be detected out basi cally a fter 2d and 4d ,respecti vely .The change of a mmoni a nitrogen concn .i n t he waterbo dy had no si g n ificant difference fro m t ha t of t he co ntrol gro up .[Concl u 2si on]Putti ng til api as i ntowaterbo dy a t hi gh density coul d reduce its cyano bact er i a si g n ificantl y ,decrease its co ntents of nitra t e nitrogen ,ni 2tr i te nitrogen and phosphoro us rapi dl y .K ey wor ds Cyanobacteri a l blo o m ;Til ap i a ;Co ntrol 基金项目 北京市教委共建计划资助项目。 作者简介 尹春华(1972-),男,湖南茶陵人,博士,讲师,从事环境生 物学研究。 收稿日期 2009204215 近年来,随着大量含氮磷废水排入天然水体,水体的富营养化程度加剧以及全球气候变暖的影响,中国乃至世界范围内蓝藻水华的爆发呈迅猛增加的趋势。由于水华蓝藻 产生以微囊藻毒素(m icroc ysti n ,MC)为主的多种藻毒[1-2] ,给生态环境和人类健康已构成严重威胁 [3-4] ,北京市延庆县 妫水湖位于北京饮用水源地官厅水库上游,水体面积达 33313h m 2 ,是北京市郊区的著名旅游景区。近年来由于氮磷负荷的加重,每年夏季已经有逐渐形成蓝藻水华的发展趋势,如何进行有效控制迫在眉睫。 目前,治理湖泊蓝藻水华有物理、化学和生物等多种方法 [5] ,虽然一些物化方法的实施能取得迅速、短期的效果, 但常带来一些二次污染。如采用重金属铜等杀藻剂可以杀死蓝藻,但其残留将导致重金属污染。有学者提出了非经典的生物操纵理论,即利用滤食性鱼类直接进行对浮游植物的生物操纵,因为滤食性鱼类能滤食浮游动物和浮游植物。国内东湖、滇池、巢湖、千岛湖和太湖等许多湖泊的富营养化治理都应用了投放鲢、鳙鱼等滤食性鱼的措施并取得了良好的效果[6-9]。国外也有许多采用滤食性鱼类成功控制蓝藻水华的报道,如巴西Pavo noa 大型水库中放养白鲢,成功控制了该水库微囊藻/水华0[10] 。滤食性鱼类主要包括鲢、鳙鱼和罗非鱼,目前采用滤食性鱼类控制蓝藻水华的研究主要集中于鲢、鳙鱼,对罗非鱼的报道相对较少。笔者在北京市延庆县妫水湖现场设置围隔进行投放罗非鱼控制蓝藻水华的试验,结果发现罗非鱼对水华蓝藻控制有良好效果。 1 材料与方法 1.1 围隔设置及实验条件 试验围隔设计成漂浮式长方体状,采用不锈钢框架和防水布制成(水下部分长宽各100c m , 高150c m 的围隔,可容纳水体近1.5m 3 )并与外界水体隔绝。2008年7月在妫水湖中安装了试验围隔,试验分2组处理:1投放罗非鱼组。罗非鱼购自北京常兴庄渔场,投放密 度为80g/m 3 ;o无鱼对照组。2次重复,试验数据取2次重复的平均值。试验开始后每天14:00取样进行蓝藻颗粒浓度、总氮和磷酸浓度等参数的测定。试验时间为2周,水体表层温度维持在28~32e ,p H 维持8.0~9.5。1.2 检测方法 蓝藻颗粒浓度测定采用血球计数板在显微镜放大400倍下进行计数。采用携带有总氮测定装置的TOC 仪测定水体中的总氮。采用离子色谱仪直接测定水体中的亚硝酸、硝酸和磷酸。 2 结果与分析2.1 罗非鱼控制蓝藻水华的效果 图1显示,在对照组围隔内水体表面漂浮着很多蓝藻,已经形成蓝藻水华(图1a)。而在投放罗非鱼的水体中,水体表面看不到任何明显的蓝藻漂浮(图1b),但可能是由于罗非鱼的搅动和排泄物的影响,水体的透明度没有明显改善。说明投放罗非鱼能有效滤食蓝藻,显著控制蓝藻水华。 图2显示,在整个试验期间对照组的蓝藻颗粒浓度有所波动,但基本维持在1@106 /m l 以上。投放罗非鱼后,蓝藻颗粒浓度迅速下降,5d 后蓝藻颗粒浓度降到较低水平(4.0@105 /ml)并维持基本不变,蓝藻生物量较C K 降低了60%,显 示出投放罗非鱼快速持续降低蓝藻数量的效果。2.2 罗非鱼对水体中各种形式氮含量的影响 图3显示,投放罗非鱼后水体中总氮浓度总体变化逐渐下降,但有一定的波动。在试验初始3d ,与C K 相比,投放罗非鱼能够迅速 责任编辑 罗芸 责任校对 卢瑶 安徽农业科学,Jo u r n al ofAnhu iAgr.i Sc.i 2009,37(23):11112-11114
第36卷 第4期 水生生物学报 Vol. 36, No.4 2012年7月 ACTA HYDROBIOLOGICA SINICA Jul., 2 0 1 2 收稿日期: 2011-09-17; 修订日期: 2012-03-14 通讯作者: 向文英(1965—), 女, 重庆市人; 博士, 副教授, 硕士生导师; 主要从事高压水射流理论、水力学与水文学、河流动力 学方向的研究。E-mail: xwy829@https://www.doczj.com/doc/6b13840846.html, DOI: 10.3724/SP.J.1035.2012.00792 不同水生动植物组合对富营养化水体的净化效应 向文英 王晓菲 (重庆大学城市建设与环境工程学院, 重庆400045) REMEDIATION OF DIFFERENT AQUATIC ANIMALS AND PLANTS ON EUTROPHIC WATER BODY XIANG Wen-Ying and WANG Xiao-Fei (College of Urban Construction and Environmental Engineering , Chongqing University , Chongqing 400045, China ) 关键词: 富营养化; 生态修复; 生物操纵; 鲢; 鳙; 水生植物 Key words: Eutrophication; Ecological restoration; Biomanipulation; Silver carp; Big Head; Aquitic plant 中图分类号: X142 文献标识码: A 文章编号: 1000-3207(2012)04-0792-06 随着城市经济的快速发展, 湖泊、水库等水生生态系统的富营养化已成为世界普遍存在的环境问题之一。水体富营养化源于流入水体中的过量营养物质(如N 、P 等)。在温度和光照作用下, 富营养化水体中的藻类大量繁殖, 致使水质下降, 水体功能退化, 甚至失去资源和景观价值。不但湖泊、河流、水库等水体的营养物质负荷量不断增加, 水体不断恶化[1, 2], 而且人工湖泊、景观池等人工水体也受到富营养化影响。 富营养化水体的净化技术主要有物理法、化学法和生物法。生物法较其他两种方法具有不易产生二次污染、廉价和易操作等特点。在生物修复方法中利用水生植物处理富营养化水体的研究日益增多, 已经受到广泛关注, 并且取得一定成果[3—5]。同时在生物修复中生物操纵技术也成为富营养化水体净化研究的热点。生物操纵技术的基本概念, 最早是由Shapiro 提出来的, 其主要原理是调整鱼群结构, 保护和发展植食性的浮游动物, 从而控制藻类的过度生长, 其核心是利用浮游动物(Zooplankton)滤食浮游藻类, 增加水体透明度[6, 7]。生物操纵在我国武汉东湖等地方已有实践证明, 利用鲢鱼、鳙鱼等滤食性鱼类直接滤食浮游植物, 从而可以有效的净化富营养化水体 [8] , 这种方法属于非经典生物操纵[9—12]。但也有研究表明, 鲢鱼和鳙鱼的引入可能使藻类小型化, 而藻类的密度和 总生物量不降甚至升高[13]。 众多研究表明, 水体富营养化作为生态问题, 单纯依靠单一动植物或者单一的方法, 很难有效的控制水体富营养化。因此本文研究利用多种水生植物和滤食性鱼类的不同搭配组合, 构建多个小型生态系统, 对静态富营养化水体进行生态修复, 研究其对富营养化水体的净化效果, 从而选择出较为高效的水生动植物搭配, 为富营养化水体的净化研究提供参考。 1 材料与方法 1.1 试验方法 本试验采用人工模拟的室内实验, 于2011年5月至2011年7月在实验室内进行。试验用水取自重庆大学民主湖湖水, 水质的初始总氮(TN)为6.1 mg/L, 总磷(TP)为0.67 mg/L, 叶绿素a 含量为0.165 mg/L, pH 为7.8, 各项指标均显示水体已呈富营养化状态。 试验共设置长宽高分别为60 cm 、30 cm 、30 cm 的玻璃鱼缸8个, 光照采用实验室窗户射入的自然光光照。向每个实验玻璃鱼缸中加入50L 民主湖湖水, 先将试验水体静置两天使实验系统初始状态基本一致, 然后测定各组合的初始水质, 再引入水生动植物开始试验。实验期间, 水温在20—29℃之间, 用蒸馏水补充蒸发的水量, 并
运用非经典生物操纵技术治理水华 浙江杭州千岛湖发展有限公司陈来生洪荣华 何光喜 任丽萍 摘要针对水体“水华”的蓝藻过度繁殖及死亡腐败,运用非经典生物操纵技术,在清除凶猛鱼的基础上,对该区域实施网围养殖式围隔,每年投放大规格鲢鳙鱼种(鲢鳙比约1.5∶1)50万kg 以上, 计1000万尾,使网围养殖区水域的存鱼量达到8.5g/m 3 ,同时对网围养殖实施禁渔。经3年试验,至今水华已不再出现,初步实现了千岛湖水域生态环境良性循环。 关键词 千岛湖 水华网围养殖 基金项目:浙江省海洋与渔业局科研项目(04K001) 1998年和1999年,在千岛湖中心湖区和西北湖区的威坪水域2次发生了异常,饮用水发现有“六六六”的气味。经鉴定,该区域5～7月份水质发生异常的主要原因是蓝绿藻(鱼腥藻、微囊藻和束丝藻为当时优势种)过度繁殖所形成的“水华”。因此在1999年8月,把中心湖区和威坪水域划为常年鲢鳙网围养殖禁渔区,在大规模清除凶猛鱼类基础上,在规定的界限上设置8道拦网,拦截水面积在标高108m 高程时为21.7万亩,实行3年(2000～2002年)保水养殖,每年投放大规格鲢鳙(鲢鳙比约1.5∶1)鱼种50万kg 以上。运用非经典生物操纵技术遏制水华再现,已取得显著成效。 1 试验区水质明显改善 投放鲢鳙鱼后的2000～2002年连续3年无水华现象出现,表明在大型深水水库的特定区域,用拦网建成网围养殖区,大量放养鲢鳙鱼可有效遏制该区域水华发生。浮游生物分析显示,2000年以前的优势种已为小环藻、直链藻、小球藻和蓝隐藻所取代。这种方法对遏制大型水域局部区域水华发生经济有效,方便易行。2水质平衡关系与平衡点 水产养殖与旅游是两个要求不全一致的产业,而且对养殖或旅游环境(如透明度)各有要求。就渔业而言,争取最大生产效益而又不破坏资源,寻找一种渔业经济发展与水环境保护之间的最佳动态平衡是渔业工作者追求的最终目标。 若养殖生产者缺乏生态意识,盲目追求“高产、高效”则会破坏脆弱的水域生态。不合理的生产活动极易将氮、磷、碳等营养元素及有机物质输入库内,或溶于水中或沉淀库底,进而使库水富营养化,其最直观的现象就是浮游生物增加,透明度减少,时而发生“水华”,有碍旅游,甚至居民的饮水质量。旅游业则要求:阳光、秀水、绿色、美丽而恬静优雅的环境。就千岛湖而言,满足旅游需要其透明度要求保持4m 以上,给人以干净、优雅的视觉。倘若此时浮游植物为150万个/L,浮游动物为900个/L,能提供938.75万kg 鲢鳙鱼产潜力,假如其中50%被捕捞,即可达到469.38万kg 的产量,可满足养殖生产的需要。而透明度处于2m 或6m 时,只能满足旅游和水产养殖中一方的 需要,或者妨碍旅游,或者不利水产养殖,只有两 者处于平衡点之时,才能取得“双赢” (表1)。3放养鲢鳙可以遏制水华出现 按2002年5～7月鲢鳙蕴藏量估算,其单位存鱼量为8.5g/m 3 ,离武汉东湖遏制水华所需鲢 鳙生物量(46～50g/m 3 )有很大距离。考虑到千岛湖浮游生物量只有武汉东湖的1/7,故本试验提出了适用于千岛湖遏制水华的最低存鱼量为 6.5g/m 3 (469.38万kg /21.7万亩)。这一结果与青岛海洋大学在水库围隔试验提出的有效遏制水华的最低存鱼量5.6g/m 3 相接近,表明具有一定合理性。□ (下转第46页)
水体富营养化程度分析评价 水体富营养化(eutrophication)是指在人类活动的影响下，氮、磷等营养物质大量进入湖泊、河口、海湾等缓流水体，引起藻类及其他浮游生物迅速繁殖，水体溶解氧量下降，水质恶化，鱼类及其他生物大量死亡的现象。 提到富营养化，普遍想到的就是营养盐总磷、总氮超标。诚然，总磷总氮等营养盐是发生富营养化的必要条件。如果水体中总磷总氮浓度很低，不可能发生富营养化；但是，反之则不然，水体中总磷总氮浓度的升高，并不一定能发生富营养化问题。富营养化发生发展是由于水体整个环境系统出现失衡，导致某种优势藻类大量繁殖生长的过程。因此，了解富营养化的发生机理和发生条件，实质上需要了解的是藻类生长繁衍的过程。尽管对于不同的水域，由于区域地理特性、自然气候条件、水生生态系统和污染特性等诸多差异，会出现不同的富营养化表现症状，也即出现不同的优势藻类种群，并连带出现各种不同类型的水生生物种类的失衡。但是，富营养氧化发生所需的必要条件基本上是一样的，最主要影响因素可以归纳为以下三个方面：（1）总磷、总氮等营养盐相对比较充足；（2）缓慢的水流流态；（3）适宜的温度条件；只有在三方面条件都比较适宜的情况下，才会出现某种优势藻类"疯"长现象，爆发富营养化。其中的水流流态主要指以流速、水深为要素的水流结构。 一、水体富营养化的主要原因： 水体富营养化的根本原因是营养物质的增加。一般认为主要是磷，其次是氮，可能还有碳、微量元素或维生素等。受控生态系统装置和试验湖区的研究结果表明磷是主要“限制因子”。Vollenweider等关于磷负荷和初级生产关系的研究也表明磷的重要性.在氮磷比低于10: 1时，或在某个季节，氮也可能成为限制因子。导致富营养化的营养物按其来源可分为点源和非点源(或面源)。前者是排放集中、位置固定的污染源，也较容易测定:非点源污染是通过地表径流、降水、地下水等进入水体，较难以测定和控制。 二、水体富营养化的监测和评价指标： 常用指标： 水体富营养化的监测和评价指标包括地理、理化、生物等指标，标准也有差异。一般有: ⑴ Ac/V指标： Ac——总集水区 V ——胡泊容积
湖泊科学 生物操纵与非经典生物操纵的应用分析及对策探讨 刘恩生 安徽农业大学合肥 摘要 分析了生物操纵和非经典生物操纵理论的原理应用条件及局限性提出了在局部水体治理湖泊富营养化的对策分析认为生物操纵的核卜内容是利用浮游动物控制藻类但浮游动物不能有效控制丝状藻类和形成群体的蓝藻水华我国的大型浅水湖泊浮游动物数量一般并不多对浮游植物摄食压力不大在浅水湖泊浮游动物摄食藻类后很快分解释放又进入物质循环因此不能治理湖泊富营养化浮游动物是浮游植物和鱼类等经济水生动物之间重要的营养通道过分追求保护浮游动物是值得思考和研究的问题而非经典生物操纵的核卜内容是利用鱼类直接控制蓝藻水华当链鲸鱼达到阈值密度可以控制蓝藻水华但很难控制所有藻类和降低 治理湖泊富营养化在局部水体治理湖泊富营养化的对策是把鱼类控藻水生植被恢复和局部水域生态系统重建相结合形成具有利用与控制蓝藻生产鱼类吸收氮磷净化水质功能的水质生物调控单元 关键词 生物操纵非经典生物操纵对策富营养化 我国湖泊已经面临富营养化问题富营养化已成为我国水环境最为重要的问题湖泊和水库的富营养化是与植物营养主要是磷和氮的富集造成的结果导致湖泊富营养化的根本原因是氮磷过量积累富营养化湖泊最普遍的现象是蓝藻水华的暴发从理论上说治理湖泊富营养化的关键是控制氮磷排放或去除水体中过量氮磷由于蓝藻暴发造成的危害很大因此如何控制水体富营养化及伴随的蓝藻水华暴发一直是环境科学淡水生态学和湖沼学研究的热点之一国内外科学家一直在探索着治理湖泊富营养化和控制蓝藻的方法和理论 科技部巢湖水专项项目和安徽农业大学引进与稳定人才项目联合资助收稿收修改稿刘恩生男年生博士教授
生物操纵在退化湖泊生态恢复上的应用 姚雁鸿1，3，余来宁2 (1.华中农业大学,武汉430070；2.江汉大学医学与生命科学学院，武汉430056； 3.中国水产科学研究院长江水产研究所，湖北荆州434000) 摘要：介绍了退化湖泊生态恢复的概念及生态恢复的步骤．描述了生物操纵的概念、应用、存在的问题及前景．作为常用的退化湖泊生态恢复技术，生物操纵主要利用了下行效应原理．几十年的生物操纵实践表明，即使存在一些影响生物操纵能否取得成功的限制因素，生物操纵依然是一种花费相对低廉、有吸引力的退化湖泊生态恢复技术． 关键词：生物操纵；恢复技术；富营养化；退化 中图分类号：S917文献标识码：A文章编号：1673-014302-0081-04 湖泊生态系统是人类生活环境的重要组成部分，它给人类提供了众多的服务，如：防洪、航运、灌溉、生活用水、水产品供给、旅游娱乐等．但由于人类活动的过度干扰，来自点源和面源的氮、磷等营养源向湖泊水体的过度排放，造成湖泊富营养化现象日益严重,湖泊水生态系统日益退化，表现为水华频繁爆发、水体发黑发臭、鱼类死亡、水生高等植物分布面积缩小甚至基本消失，它严重地影响湖泊生态系统服务功能的提供，甚至威胁到人类的健康．随着湖泊富营养化现象日益严重，各国普遍开展了富营养化产生的原因及防治与退化湖泊恢复的研究与探索，也产生了诸如底泥疏浚、水底通氧、构建沿岸带湿地、投放化学药物等治理措施，并在一定范围内进行了用于水体富营养化防治的实践．生物操纵就是湖泊内源治理的方法之一，它是退化湖泊生态恢复的一个重要方法． 1退化湖泊生态恢复 1.1恢复的目标 按生态恢复的定义，湖泊生态恢复就是恢复湖泊的结构与功能特征，重建湖泊受干扰前的结构与功能及有关的地理、化学和生物学特征．但是恢复目标难以确定，这也是“恢复”这个概念受到责难的原因之一．恢复是一个动态的过程， 水域生态系统的自愈能力极强，在减轻人类干扰（如限制营养盐向水体排放等）后，只要适当地引进关键种，水域生态系统就会很快恢复．湖泊恢复也不是无限地恢复到湖泊干扰前的状态，绝对的恢复是不可能达到的.因为恢复还涉及到一个代价问题，如果恢复的代价过大，大大超过人们从恢复中获得的湖泊服务功能价值，则选择这样的恢复状态是不理性的.如相对富营养化湖泊而言，贫营养化湖泊更接近于受干扰前的状态，但我们不能因此决定湖泊恢复就是要恢复到贫营养化状态，不仅因为恢复到贫营养化状态的代价太大，而且因为一个水草繁茂，水质清澈的富营养化湖泊更符合人类的需要． 1.2湖泊生态恢复的步骤 湖泊生态恢复的步骤为：⑴诊断问题并建立恢复目标，即分析湖泊退化的原因，确定恢复所要达到的状态；⑵除去已存的或潜在的退化促进因素；⑶削减营养负荷；⑷生物操纵；⑸重建水生植被；⑹重建适当的鱼类种群；⑺检测恢复的结果． 退化湖泊生态恢复的措施很多，主要分外源治理和内源治理：外源治理主要是通过各种措施和手段控制营养盐向湖泊过度排放；内源治理则是采取生物、物理、化学的方法使退化湖泊由藻型浊水态恢复到草型清水态．生物操纵是湖泊内 收稿日期：2007－01－19作者简介：姚雁鸿(1972
2010年现代生命科学进展考试试题 1、达尔文雀喙的适应性进化及其分子机制。 达尔文雀主要有三个类群：地雀、树雀和类莺雀。地雀主要分布在岛屿的沿岸地带，常在地面活动，以植物的种子为食；树雀主要分布在岛屿的森林中，常在树上活动，除植食雀外，其他树雀均以昆虫为主要食物；类莺雀找哦昂的莺雀栖息于林缘和灌丛中，繁殖期主要以昆虫为食，剑食物嫩芽和果实，而其中的可岛雀食性广泛，取食昆虫、花蜜、浆果、小坚果和小型爬行动物。 达尔文雀不同种类有着不同的喙，这是通过长期的适应性进化形成的，达尔文雀喙的适应性进化研究主要是根据达加拉帕戈斯群岛的不同种类的雀喙的形成进行的。由于种群数量的逐渐增长，由于资源限制和竞争的因素等作用，达加拉帕戈斯群岛的雀喙开始发生不同的变化，以利于他们的生存，为了生存，他们这些有利的变异被慢慢地保存下来，从而形成了不同的物种。 达加拉帕戈斯群岛气候的变化使得岛上的雀的食物发生大量的变化，在干旱时期，食物中小颗粒种子不宜存货而变得越来越少，大颗粒的种子相对较易存活，其比例增加，这样对于那些小喙的雀来说就不宜生存下去而逐渐向大喙的雀发展，而大喙的雀为了更好的生活，它的喙会继续增大。而在雨量多的时期里，许多禾本科植物生产出大量小颗粒种子，大颗粒的比例会大幅度下降，这时对于喙小的雀来说比较方便取食，而喙大的雀则不宜取食，这些雀为了生存下去，不得不随着自然的变化而改变喙的大小。达加拉帕戈斯群岛气候变化改变了食物的组成，食物组成的变化通过自然选择作用雀的喙的形状。 达尔文雀喙的适应性进化主要是通过自然选择作用，自然选择的主要内容包括变异和遗传、生存竞争和选择等。变异是选择的原材料，在生存竞争中，有利的变异将较多地保存下来，有害的变异则被淘汰。有利变异在种内经过长期积累，导致性状分歧，最后形成新种。生物就是这样通过自然选择缓慢进化的。
1、水环境承载能力：在一定水域，在水体功能能够继续保持并仍保持良好生态系统的条件下，容纳污水及污染物的最大能力 2、空间异质性：生态学过程和格局在空间分布上的不均匀性及其复杂性，可理解为是空间缀块性和梯度的总和 3、地下水：存在于地表以下岩（土）层空隙中各种不同形式水的统称 4、水体富营养化：指湖泊等水体由于接纳过多的氮、磷等营养物质而使其生产力水平异常提高的过程 5、污染生态效应：污染物进入水环境后，对水生生态系统的结构和功能产生某些影响，这种表现在生态系统中的响应即为污染生态效应 6、水文循环：水在海洋、大气和陆地之间无休止的运行 7、空气吹脱：在一定压力条件下，将压缩空气注入受污染区域，将溶解在地下水中的挥发性化合物、吸附在土壤颗粒表面上的化合物以及阻塞在土壤空隙中的化合物驱赶出来 8、湖滨带：湖泊水域与流域陆地生态系统间的生态过渡带 9、含水层：能够透过并给出相当数量水的岩层 10、隔水层：不能透过与给出水，或者透过与给出水的数量微不足道的岩层 11、水体季节性分层：具有较大水深的湖泊和水库由于水体中热量传递不均匀而出现季节性的温度分层现象 12、承压水：充满于两个稳定隔水层之间的含水层中的地下水 13、饱和渗流：饱和带的潜水和承压水在重力作用下运动 14、湖泊：地面上洼地积水形成比较宽广的水域 15、河流廊道：指与河流联系紧密的河岸带和洪泛区等生态系统，包括陆地、植物、动物及其内部的河溪网络 16、景观破碎化：景观中各生态系统之间的各种功能联系断裂或连接度降低 生物放大：同一食物链上的高营养级生物通过吞食低营养级生物蓄积某种元素或难降解物质，使其在体内的浓度随营养级数提高而增大的现象 污染生态效应：污染物进入水环境后，对水生生态系统的结构和功能产生某些影响，这种表现在生态系统中的响应即为污染生态效应。 潜水：饱和带中第一个具有自由水面的含水层的水渗流：地下水在岩土空隙中的运动现象 经典生物操纵：即通过去除食浮游生物者或添加食鱼动物降低浮游生物食性鱼的数量，使浮游动物的生物量增加和体形增大，从而提高浮游动物对浮游植物的摄食效率，降低浮游植物的数量 非经典生物操纵法： 通过控制凶猛鱼类及放养食浮游生物的虑食性鱼类（鲢、鳙）来直接牧食蓝藻水华的生物操纵方法 水体季节性分层影响因素：气温和太阳辐射 浅水湖泊沉积物中污染物迁移扩散，积累和分布受湖泊风生环流的控制。 河流生态系统具有自我调控和自我修复功能，主要通过系统的抵抗力和恢复力体现 水环境承载能力具体体现在纳污能力上 在湿地生态系统各组成要素中，水文条件是湿地形成、发育和演化的最关键因子 地下水的补给径流和排泄是决定地下水循环的两个基本环节，是地下水径流形成的基本因素 湖沼学作用过程控制重金属的迁移转化和毒性效应 沉积物—水界面的氮循环对上覆水体具有营养供给和对营养化湖泊自然净化的双重作用 湖水运动的主要驱动因素是：河湖水量交换及湖面气象因素等（尤其是风） 经典生物操纵无法将营养盐移除湖泊 非经典生物操纵中营养层次低的鰱，鳙生长期短，易于捕捞，可将营养盐移除湖泊。 湖沼学特征：季节性水体分层和植被群落的圈层分布 水产养殖自身污染：营养物污染、药物污染、底泥富集污染 风涌水是指：风成湖流 ．．．．在向前运动时遭遇到湖岸的阻拦而在迎风岸引起水位的上升。 我国北方水源地水质状况劣与南方 河流生态系统的组成： 非生物环境： （1）无机物质（2）有机物质（3）气候条件 生物环境： （1）生产者（2）大型消费者/吞噬者（3）微型消费者/分解者