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1.
Ecological environment changes in Daya Bay, China, from 1982 to 2004   总被引：7，自引：0，他引：7  
Data collected from 12 marine monitoring stations in Daya Bay from 1982 to 2004 reveal a substantial change in the ecological environment of this region. The average N/P ratio increased from 1.377 in 1985 to 49.09 in 2004. Algal species changed from 159 species of 46 genera in 1982 to 126 species of 44 genera in 2004. Major zooplankton species went from 46 species in 1983 to 36 species in 2004. The annual mean biomass of benthic animals was recorded at 123.10 g m−2 in 1982 and 126.68 g m−2 in 2004. Mean biomass and species of benthic animals near nuclear power plants ranged from 317.9 g m−2 in 1991 to 45.24 g m−2 in 2004 and from 250 species in 1991 to 177 species in 2004. A total of 12-19 species of hermatypic corals and 13 species of mangrove plants were observed in Daya Bay from 1984 to 2002.  相似文献   

2.
Long-term impacts of increased metal loading (Hg, Cu, Cd, Zn and Pb) on phytoplankton communities of large limno-corrals (diameter 12 m, depth 10 m) were studied. Increased metal concentrations initially lowered phytoplankton biomass, as well as species number and photosynthetic activity of phytoplankton. They caused changes in metal speciation and shifts in phytoplankton community structure, favoring less susceptible species. Although adaptation was not sufficient to completely prevent the metal-induced depression of photosynthesis, due to depressed zooplankton grazing, at the end of the experiment even higher phytoplankton densities were observed in the metal-loaded corrals than in the control.  相似文献   

3.
Coral species composition of drilled cores from emergent bank reefs, and coral cover of the surface of old and living reefs located along the coast of the state of Bahia, Eastern Brazil, revealed that there is a marked change in the occurrence of the major building coral species in different time intervals of the reef structure, as well as in the living surface of reefs located in two different geographical sites. Holocene core sections from two reef areas (12 degrees 40'S-38 degrees 00'W and 18 degrees 00'S-39 degrees 00'W) have as major reef builders, on its topmost core interval (3 to 4 ky old), the endemic coral Mussismilia braziliensis Verrill, 1868, which also dominate on the 2.5-3.5 ky old surfaces of truncated reef tops. At the base of the cores (the 2m lower interval, older than 4 ky BP), another endemic coral Mussismilia harttii Verrill, 1868 is the dominant reef component. The relative abundance of M. braziliensis on the living surfaces of shallow reefs from both areas, shows that in the southern area, it is up to 98% on reefs located 60 km off the coast, in depths between 3 and 4m, but do not exceed 1.3% on the surface of the northern reefs located 1-2 km off the coast in depths 4-5m. The Holocene falling sea level that occurred along the coast of Brazil since 5.1 ky BP, causes an increasing runoff into the area of coastal reefs. This phenomenon may have affected the nearshore reef building fauna, replacing a more susceptive coral fauna with one better adapted to low light levels and higher sediment influx. The high turbidity associated with early Holocene shelf flooding, should also be responsible for the absence of M. braziliensis during the initial stages of reef buildup in Brazil. At the present time, the rapidly increasing human pressure, due to changes in land uses of the coastal zone (increasing sedimentation rate, nutrification of coastal waters, industrial pollution) and underwater practices, such as overfishing and an intense tourism, is aggravating the recovery capacity of this already naturally threatened coral community. If this situation coupled with increasing sea surface temperature persists, modern coral reef growth, in Brazil cannot be maintained and the major reef building coral species of the reefs in Bahia, a remnant endemic coral fauna will very soon appear in the list of endangered species.  相似文献   

4.
This study combined measurements from multiple platforms with acoustic instruments on moorings and on a ship and optics on a profiler and an autonomous underwater vehicle (AUV) to examine the relationships between fluorescent, bioluminescent, and acoustically scattering layers in Monterey Bay during nighttime hours in July and August of 2006 and May of 2008. We identified thin bioluminescent layers that were strongly correlated with acoustic scattering at the same depth but were part of vertically broad acoustic features, suggesting layers of unique composition inside larger biomass features. These compositional thin layers nested inside larger biomass features may be a common ecosystem component and are likely to have significant ecological impacts but are extremely difficult to identify as most approaches capable of the vertical scales of measurement necessary for the identification of sub-meter scale patterns assess bulk properties rather than specific layer composition. Measurements of multiple types of thin layers showed that the depth offset between thin phytoplankton and zooplankton layers was highly variable with some layers found at the same depth but others found up to 16 m apart. The vertical offset between phytoplankton and zooplankton thin layers was strongly predicted by the fraction of the water column fluorescence contained within a thin phytoplankton layer. Thin zooplankton layers were only vertically associated with thin phytoplankton layers when the phytoplankton in a layer accounted for more than about 18–20% of the water column chlorophyll. Trophic interactions were likely occurring between phytoplankton and zooplankton thin layers but phytoplankton thin layers were exploited by zooplankton only when they represented a large fraction of the available phytoplankton, suggesting zooplankton have some knowledge of the available food over the entire water column. The horizontal extent of phytoplankton layers, discussed in the second paper in this series, is likely an important factor contributing to this selective exploitation by zooplankton. The pattern of vertical offset between phytoplankton and zooplankton layers was consistent between studies in different years and using different combinations of platforms, indicating the importance of the relationship between zooplankton layers and the fraction of phytoplankton within a layer at night within Monterey Bay. These results highlight the value of integrating measurements of various types of organisms to understand thin layers processes and the importance of assessing ecological interactions in plankton thin layers within the context of the properties of the entire water column, like the animals themselves do.  相似文献   

5.
Coral reefs in Jakarta Bay have been subjected to scientific studies since the 1920s. Also from that time on biological collections were made. The reefs in the Jakarta Bay have been under long-term natural and anthropogenic stress. With the biological collections and historical documents the coral species richness in Jakarta Bay around 1920 was reconstructed. New data from this bay and the adjacent offshore Thousand Islands archipelago were obtained during a 2005 research expedition. A comparison of the coral assemblages between 1920 and 2005 reveals a clear decline in species numbers. The most prominent results include the near-shore disappearance of species belonging to the families Acroporidae, Milleporidae, and to a lesser extent Poritidae. The overall coral species composition of the reefs has changed considerably, which is partly reflected in a strong decline in coral species richness. About half the number of species recorded in 1920 was found again in 2005.  相似文献   

6.
The seasonal and interannual variability in the phytoplankton community in Liverpool Bay between 2003 and 2009 has been examined using results from high frequency, in situ measurements combined with discrete samples collected at one location in the bay. The spring phytoplankton bloom (up to 29.4 mg chlorophyll m−3) is an annual feature at the study site and its timing may vary by up to 50 days between years. The variability in the underwater light climate and turbulent mixing are identified as key factors controlling the timing of phytoplankton blooms. Modelled average annual gross and net production are estimated to be 223 and 56 g C m−2 year−1, respectively. Light microscope counts showed that the phytoplankton community is dominated by diatoms, with dinoflagellates appearing annually for short periods of time between July and October. The zooplankton community at the study site is dominated by copepods and use of a fine mesh (80 μm) resulted in higher abundances of copepods determined (up to 2.5 × 106 ind. m−2) than has previously reported for this location. There is a strong seasonal cycle in copepod biomass and copepods greater than 270 μm contribute less than 10% of the total biomass. Seasonal trends in copepod biomass lag those in the phytoplankton community with a delay of 3 to 4 months between the maximum phytoplankton biomass and the maximum copepod biomass. Grazing by copepods exceeds net primary production at the site and indicates that an additional advective supply of carbon is required to support the copepod community.  相似文献   

7.
Song X  Huang L  Zhang J  Huang X  Zhang J  Yin J  Tan Y  Liu S 《Marine pollution bulletin》2004,49(11-12):1036-1044
Environmental factors, phytoplankton biomass (Chl a) and primary production of two water areas in Daya Bay (Dapeng'ao Bay and Aotou Bay) were investigated during the transition period from spring to summer. Chl a ranged from 3.20 to 13.62 and 13.43 to 26.49 mg m(-3) in Dapeng'ao Bay and Aotou Bay respectively, if data obtained during red tides are excluded. Primary production varied between 239.7 and 1001.4 mg Cm(-2) d(-1) in Dapeng'ao Bay. The regional distribution of Chl a and primary production were mostly consistent from spring to summer in both bays. Seasonal transition characters have been found in Daya Bay from spring to summer, including high values of DO, nitrate and silicate. Size structures of phytoplankton and its primary production do not change very much from spring to summer, with micro-phytoplankton dominating and contributing about 50% of the whole. In Daya Bay, phytoplankton is limited by nitrogen in spring, and by phosphate in summer. Artificial impacts are evident from high temperature effluent from nuclear power stations, aquaculture and sewage. During the investigation, a red tide occurred in Aotou Bay, with a maximum Chl a of 103.23 mgm(-3) at surface and primary production of 2721.9 mg Cm(-2) d(-1) in the red tide center. Raised water temperature and nutrient supply from land-sources help to stimulate annual red tides.  相似文献   

8.
The seasonal variations in biomass, abundance, and species composition of plankton in relation to hydrography were studied in saline lake Namuka Co, northern Tibet, China. The sampling was carried out at approximately monthly intervals from June 2001 to July 2002. The salinity ranged from 5.5 to 26 g/L. The mean annual air and water temperature showed a clear seasonal pattern, which was approximately 4.4 and 7.4°C, respectively, with the lowest water temperature in winter (from December to March, −1°C) and the highest in June and July (18°C). The results showed that 36 taxa of phytoplankton and 16 taxa of zooplankton were identified. Both the biomass and abundance of total phytoplankton were lower in the winter and peaked once or twice during the summer and spring in the early August (8.23 mg/L and 158.2 × 106 ind./L). The seasonal variation in total zooplankton biomass and abundance was characterized by lower values in both winter and early spring, and one maximum (90.5 mg/L and 935 ind. L−1) occurred in the late summer. Major phytoplankton species were Gloeothece linearis, Oscillatoria tenuis, Gloeocapsa punctata, Ctenocladus circinnatus, Ulothrix sp., and Spirogyra sp. And major zooplankton species included Vorticella campanula, Brachionus plicatilis, Daphniopsis tibetana, Cletocamptus dertersi, Arctodiaptomus stewartianus. The production of D. tibetana was 420.3 g m3 a−1. The total number of plankton species has a significant negative correlation with the salinity.  相似文献   

9.
2001年9月和2002年8、9月对内蒙古锡林郭勒盟几个小型盐湖的浮游生物群落特征进行了研究调查.共检出浮游植物59种(属),优势种类为:线形粘杆藻、针晶蓝纤维藻、小席藻、微小平裂藻、舟形藻、绿裸藻、普通小球藻、盐生杜氏藻和衣藻等;浮游动物34种(属),优势种类为:膜袋虫、裸口虫、四膜虫、纤毛虫、褶皱臂尾轮虫、萼花臂尾轮虫、蒙古裸腹溞、卤虫、咸水北镖水蚤和新月北镖水蚤等．浮游植物生物量以达格尔淖最高,平均为166.56mg/L;其次是扎格斯台淖为106.77mg/L;再次是夏日淖和桑根达莱淖,分别为6.39mg/L和2.83mg/L,变动幅度较小.浮游动物生物量以桑根达莱淖最高,平均为24654mg/L,变动幅度较大;其次是扎格斯台淖为27.24mg/L,再次为夏日淖和达格尔淖,分别为12.01mg/L和2.76mg/L.文中讨论了内陆盐水浮游生物的种类组成、分布、生物量和盐度耐性与盐度、营养盐、碱度、pH及离子组成的关系等问题.  相似文献   

10.
谷孝鸿 《湖泊科学》1992,4(1):71-78
1987-1989年对山东省禹城渍涝洼地新开鱼塘水体中浮游动物进行了调查。1987、1988、1989年成鱼养殖期间共检出浮游动物种类分别为29、34、52种,平均数量为11911、39366.1、77889.2个/L,平均生物量为5.145、5.7675、9.6285mg/L。1988、1989年,鱼塘水体中浮游动物的数量高峰在7月。新开鱼塘养鱼前,只检出5种。数量为600个/L,生物量为0.0585mg/L。养鱼后三年来,鱼塘水体中浮游动物种类、数量及生物量的逐年增加,表明了新开鱼塘富营养化的演变程度。鱼塘施肥前后,水体中原生动物与轮虫的数量均有明显变化,其中原生动物变化更为明显。  相似文献   

11.
A photographic analysis was conducted at five shallow reef sites (5-6 m) at Eilat (northern Red Sea) to study changes in live coral cover during a 2-year period. Logit regression analysis showed that levels of total oxidized nitrogen (TON; NO(2)+NO(3)) and the presence of SCUBA divers were significant explicative variables of coral partial mortality, while sedimentation rate was not significant. Sites exposed to mean TON levels above 0.4 microM TON showed significantly lower live stony coral cover and abundance per m(2), and higher partial mortality of coral colonies than sites exposed to lower TON. These findings may be useful in establishing limits for TON levels at Eilat, but must be interpreted with caution due to the complexity of nutrient dynamics in coral reefs, the uncertainty of the effects of nutrients on coral physiological processes, and the possibility of interactions among multiple coral stressors.  相似文献   

12.
A mass balance model is applied to assess the biotic energy flux in ecosystems of the operating Zeiskoe and Bureiskoe reservoirs and the anticipated Lower Zeiskoe and Lower Bureiskoe Reservoirs. A forecast of the mean annual biomass and annual production of phytoplankton, macrophytes, epiphytes, and phytobenthos (primary producers), bacterioplankton, bacteriobenthos (decomposers), “peaceful” and predatory zooplankton, zoobenthos, plankton-feeding, benthos-feeding, and predatory fish (consumers).  相似文献   

13.
Metazooplankton abundance, biomass (<80μm, 200-500μm and >500μm) and community structure in the Ahe atoll were studied together with their relationships with environmental factors (temperature, salinity, wind) and trophic factors (phytoplankton, bacteria, heterotrophic nanoflagellates (HNF) and ciliates) during three periods in 2008-2009. Meroplankton, mainly bivalve and gastropod larvae, was dominant. Holoplankton was dominated by copepods, the main species being Oithona spp., Paracalanus parvus, Clausocalanus spp., Corycaeus spp., Acartia fossae and Undinula vulgaris. The results suggest a clear wind influence on the structure and horizontal distribution of the zooplankton communities. The metazooplankton appeared to be controlled mainly by food resources, suggesting a bottom-up control. The low nanophytoplankton biomass in contrast to the high abundance of picophytoplankton, HNF and nano-particle grazers (mainly Oithona spp., Paracalanus and bivalve larvae) highlighted the importance of the microbial loop in the food web.  相似文献   

14.
渍涝洼地鱼塘中浮游动物的变化   总被引：2，自引：2，他引：2  
1987—1989年对山东省禹城渍涝洼地新开鱼塘水体中浮游动物进行了调查。1987、1988、1989年成鱼养殖期间共检出浮游动物种类分别为29、34、52种,平均数量为11911、39366.1、77889.2个/L,平均生物量为5.145、5.7675、9.6285mg/L。1988、1989年,鱼塘水体中浮游动物的数量高峰在7月。新开鱼塘养鱼前,只检出5种。数量为600个/L,生物量为0.0585mg/L。养鱼后三年来,鱼塘水体中浮游动物种类、数量及生物量的逐年增加,表明了新开鱼塘富营养化的演变程度。鱼塘施肥前后,水体中原生动物与轮虫的数量均有明显变化,其中原生动物变化更为明显。  相似文献   

15.
Coral bleaching, involving the expulsion of symbiotic zooxanthellae from the host cells, poses a major threat to coral reefs throughout their distributional range. The role of temperature in coral bleaching has been extensively investigated and is widely accepted. A bleaching event was observed on the marginal high-latitude reefs of South Africa located at Sodwana Bay during the summer months of 2000. This was associated with increased sea temperatures with high seasonal peaks in summer and increased radiation in exceptionally clear water. The bleaching was limited to Two-mile Reef and Nine-mile Reef at Sodwana Bay and affected <12% of the total living cover on Two-mile Reef. Montipora spp., Alveopora spongiosa and Acropora spp. were bleached, as well as some Alcyoniidae (Sinularia dura, Lobophytum depressum, L. patulum). A cyclical increase in sea temperature (with a period of 5–6 years) was recorded during 1998–2000 in addition to the regional temperature increase caused by the El Niño Southern Oscillation phenomenon. The mean sea temperature increased at a rate of 0.27 °C year−1 from May 1994 to April 2000. High maximum temperatures were measured (>29 °C). The lowest mean monthly and the mean maximum monthly temperatures at which coral bleaching occurred were 27.5 and 28.8 °C, respectively, while the duration for which high temperatures occurred in 2000 was 67 days at 27.5 °C (4 days at 28.8 °C). Increased water clarity and radiation appeared to be a synergistic cause in the coral bleaching encountered at Sodwana Bay.  相似文献   

16.
Ecological restoration of eutrophic lakes using aquatic macrophytes is an important and practical technology. Here, we investigated the response of phytoplankton and zooplankton to a large-scale 2015-built aquatic macrophyte enclosure (AME, 200,000 m2) screened of by a PVC net in Baima Lake, a eutrophic lake, from spring to autumn of 2019. AME significantly improved water quality by increasing water transparency, and reducing total nitrogen, total phosphorus, and chlorophyll-a content during the growing season. AME significantly decreased phytoplankton abundance and biomass and marginally increased zooplankton abundance and biomass. Phytoplankton and zooplankton communities were closely related to environmental factors, such as water temperature, conductivity, total phosphorus, chemical oxygen demand, and chlorophyll-a inside and outside the AME. The zooplankton:phytoplankton biomass ratio inside was slightly higher than outside the AME. Zooplankton and phytoplankton biomass were significantly positively correlated inside and outside the AME, as were chlorophyll-a and total phosphorus. We found phosphorus to be a key factor limiting primary productivity in Baima Lake, and that bottom-up effects were the main driver to control phytoplankton in the AME. Using aquatic macrophytes to reduce nutrient loads is an effective way to manage eutrophication in Baima Lake.  相似文献   

17.
太湖梅梁湾与五里湖浮游植物群落的比较   总被引：19，自引：4，他引：15  
富营养化和风浪是影响大型浅水湖泊浮游植物群落的重要因素,本文于2003年10月至2004年9月对太湖梅梁湾和五里湖理化环境因子(水温、透明度值、悬浮质浓度和氮、磷营养盐浓度)和浮游植物群落进行了逐月监测,通过对两个湖区理化因子和浮游植物群落结构在周年内季节变化的比较研究,探讨富营养化程度以及风浪对浮游植物群落结构的影响,结果为:(1)梅梁湾由于受风浪影响悬浮物含量较高,五里湖则富营养化水平更高.(2)周年内五里湖浮游植物平均生物量(6.85 mg/L)高于梅梁湾的平均生物量(4.99 mg/L),两个湖区都呈现夏秋高峰、冬季低谷的变化特征.梅梁湾浮游植物群落季节演替的模式基本为:冬季硅藻(小环藻属Cyclotella spp.)和隐藻(隐藻属Cryptomonas spp.)-春季绿藻(细丝藻属Planctonema sp.)-夏季绿藻(绿球藻目Chlorococcales种类)和蓝藻(微囊藻属Microcystis spp.和浮游蓝丝藻属Planktothrix spp.)-初秋蓝藻(微囊藻属)和硅藻(浮游直链硅藻Aulacoseira spp.)-秋季隐藻(隐藻属).五里湖的季节演替模式没有梅梁湾明显,全年隐藻(隐藻属)都占优势,在此基础上,秋冬季硅藻(小环藻属和浮游直链硅藻属)占优势,裸藻(裸藻属Euglena spp.)在冬春季占优势,绿藻(绿球藻目种类和团藻目衣藻属Chlamydomonas spp.)在整个春季和初夏的优势地位在夏季被蓝藻(微囊藻属和浮游蓝丝藻属)所取代.群落构成的差异是浮游植物对两个湖区不同风浪条件和富营养化水平的响应结果.(3)通过与PEG(Plankton Ecology Group)模式的比较,梅梁湾和五里湖浮游植物群落的季节演替主要受水温、光照、营养盐(氮、磷)浓度和浮游动物牧食等因子的影响,因此,大型富营养化浅水湖泊浮游植物群落演替规律需要进一步的研究.  相似文献   

18.
Bacteria and phytoplankton are integral in the mobilization and transfer of organic matter to higher trophic levels. Hence, we examined their role in zooplankton diets and assessed trends in their nitrogen isotopic variability. We performed feeding experiments with natural particulate organic matter (POM) and four zooplankton groups (Daphnia, Holopedium, large calanoids and small calanoids) to (1) examine whether there are differences in consumption (presented as clearance and ingestion rates) of phytoplankton and bacteria, and (2) determine whether differences in zooplankton clearance and ingestion rates are correlated with their δ15N isotopic signatures. In general, phytoplankton and bacteria clearance rates and biomass ingested per animal varied significantly among different zooplankton groups within lakes and between lakes for a given zooplankton group. Within a given lake, Daphnia and Holopedium had the highest phytoplankton and bacteria clearance and ingestion rates, followed by large calanoids, and then small calanoids. For a given zooplankton group, bacteria and phytoplankton clearance rates varied among lakes. In contrast, phytoplankton ingestion rates were consistently highest in Dickie Lake for all taxa, whereas bacteria ingestion rates were more variable among lakes for the different zooplankton taxa. The percentage contribution of different phytoplankton taxa to the biomass of phytoplankton ingested also varied significantly among lakes for a given taxa, but there were few differences within a given lake among zooplankton. Zooplankton δ15NDOMC values were correlated with their size adjusted phytoplankton and bacteria clearance and ingestion rates. The correlations were stronger with (1) phytoplankton compared to bacteria, and (2) clearance rates compared to ingestion rates of biomass. Together our results suggest that zooplankton taxa with low phytoplankton and bacteria clearance and ingestion rates and higher δ15NDOMC are likely exploiting food sources from higher trophic levels.  相似文献   

19.
The seasonal pattern of size-fractionated phytoplankton biomass, primary production and respiration was investigated along the longitudinal axis of the Nervión–Ibaizabal estuary (Bay of Biscay) from April 2003 to September 2004. Environmental factors influencing phytoplankton dynamics were also studied. Chlorophyll a biomass showed a longitudinal pattern of increase from the outer Abra bay to the inner estuary. On a seasonal scale, in the intermediate and inner estuary phytoplankton biomass maxima were registered in summer, the warmest and driest season, whereas in the outer bay chlorophyll a peaks occurred in May 2004, but were delayed to August 2003, likely due to a very rainy spring. Data suggest that river flow exerts a marked influence on the timing of phytoplankton biomass maxima in this estuary, decreased river flows providing a lowering of turbidity and an increase in water residence time needed for chlorophyll a to build up. Nutrient concentrations were high enough not to limit phytoplankton growth throughout the annual cycle, except silicate and occasionally phosphate in the outer bay during summer. Silicate concentration correlated positively with river flow, whereas ammonium and phosphate maximum values were generally measured in the mid-estuary, suggesting the importance of allochthonous anthropogenic sources. In the intermediate and inner estuary phytoplankton biomass was generally dominated by >8 μm size-fraction (ca. 60%), but in August 2003 <8 μm size-fraction increased its contribution in the intermediate estuary. It is argued that the lower nutrient concentrations measured in August 2003 than in August 2004 could have played a role. This is the first study in which phytoplankton primary production rates have been measured along the longitudinal axis of the Nervión–Ibaizabal estuary. Throughout the annual cycle these rates ranged from 0.001 to 3.163 g C m?3 d?1 and were comparable to those measured in nearby small estuaries of the Basque coast and other larger estuaries on the Bay of Biscay. Surface plankton community respiration rate maxima were measured during the spring 2004 chlorophyll a peak in the Abra bay and in summer months at the mid and inner estuary, coinciding with chlorophyll a biomass and primary production maxima. In general, respiration rates showed a positive correlation with temperature. In order to compare results from the Nervión–Ibaizabal estuary with other nearshore coastal and estuarine ecosystems within the Bay of Biscay a review of existing information on phytoplankton biomass and primary production dynamics was performed.  相似文献   

20.
太湖霍甫水丝蚓(Limnodrilus hoffmeisteri Claparède)的时空格局   总被引：1，自引：1，他引：0  
2005年1-12月对太湖霍甫水丝蚓进行了逐月调查.太湖霍甫水丝蚓年均密度和生物量分别为3273.75 ind./m2和4.697 g/m2,均在2月份达到最大值.根据体长频数分布的周年变化,推测太湖霍甫水丝蚓一年有三代.太湖霍甫水丝蚓密度和生物量在空间上表现出明显的差异性,且随季节变化较小,其高值区域均出现在太湖北部梅梁湾和竺山湾及西部河口湖区,而在其它区域的现存量均较低.分析表明太湖霍甫水丝蚓空间差异可能与营养水平、底质类型、可摄食的食物及生境的稳定性等因素有关.  相似文献   

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