Abstract:
Plankton are an important part of aquatic ecosystems and are often used as indicators of the quality of the aquatic environment due to their sensitivity to the state of the aquatic environment. In order to study the characteristics of plankton community in Baiyangdian and its relationship with environmental factors, the plankton and environmental factors of five sampling points in Baiyangdian district were investigated and analyzed in spring (May), summer (August) and autumn (October) of 2018, and the relationship between the structural changes of Baiyangdian plankton communities and the interrelationship of major environmental factors was analyzed by Pearson correlation analysis. The results show that according to the concentration values of water quality parameters such as TP, NH3-N, CODMn and TN, the water quality of Baiyangdian water body is class V water in summer and iv. water in spring and autumn. A total of 74 species of phytoplankton and 22 species of zooplankton were detected in the baiyangdian study area. The community structure of Plankton in Baiyangdian varies significantly from season to season, and the summer abundance of both types of plankton reaches the maximum. Phytoplankton have an absolute advantage in spring and summer, such as cyanobacteria and green algae phylum, and in autumn, there are dominant taxa such as diatom phylum, bare algae phylum, dinoflagellate phylum and cryptoalgae phylum. Zooplankton are predominantly grouped in all seasons with rotifers. According to the water quality category analysis based on the plankton community characteristic index, Most of the index of Baiyangdian in different seasons shows medium pollution. The water pollution status reflected in the planktonic biodiversity index and the water quality evaluation results of physical and chemical factors are relatively consistent with the seasonal trend. The phytoplankton diversity index was more correlated with TP, CODMn and DO, and the zooplankton diversity index was more correlated with CODMn, NH3-N and TN.
Keywords: Baiyangdian; Plankton; Community structure; Environmental factors; Correlation analysis; Water quality assessment; Water environment;
About author:Zhou Xushen (1982-), male, senior engineer, doctoral candidate, mainly engaged in water ecology research. E-mail:[email protected]; *Sun Bowen (1987-), male, associate professor, Ph.D., mainly engaged in ecological hydraulic research. E-mail:[email protected];
Fund: National Natural Science Foundation of China (51621092, 51609166);
Citations: Zhou Xushen, Li Na, Sun Bowen, et al. Seasonal variation of plankton community structure in Baiyangdian and its relationship with environmental factors[J]. Water Resources and Hydropower Engineering, 2021, 52( 8): 110-119. ZHOU Xushen，LI Na，SUN Bowen，et al． Seasonal variation of plankton community structure in the Lake Baiyangdian and the relationship with environmental factors［J］. Water Ｒesources and Hydropower Engineering，2021，52( 8) : 110-119.
<h1 class="pgc-h-arrow-right" data-track="8" >0 Introduction</h1>
Large shallow lakes are important freshwater wetland ecosystems with unique ecosystem characteristics that play an important role in maintaining natural ecological balance, improving natural resource conditions and providing ecosystem services. In recent years, under the influence of climate change and strong human interference, more and more lakes are facing crises such as water volume reduction, water pollution, biodiversity reduction and ecological service function decline. Plankton is an important biological component of aquatic ecosystems, a natural food for aquatic animals such as fish, and an important part of the production and transmission of nutrients in water bodies, which plays an important role in maintaining the richness and stability of food webs. Plankton has the characteristics of strong vitality, fast reproduction rate and sensitive response to environmental changes, and the changes in its community structure are closely related to the changes in the surrounding environmental factors, so they are often used as important indicators to reflect the ecological status of lakes and water quality evaluation. For example, JIN et al. studied the main influencing factors of the phytoplanto functional groups of Ulanso Haihu Lake, and proposed to use the presence of certain phytoplankton functional groups to indicate the current lake conditions; Chen Hong et al. used the phytoplankton community structure, abundance, diversity index and water physical and chemical indexes to comprehensively evaluate the water quality status of the urban section of the Bahe River, and discussed the relationship between its community structure and environmental factors. In addition, due to the differences in the spatial environment and the complexity of the interactions between organisms, the key factors affecting the structure of plankton communities vary greatly in different water bodies. Cai Yang et al. found that water temperature and electrical conductivity were the key factors driving the ecological distribution of plankton communities in Jingpo Lake; AFONINA et al. used methods based on correlation matrix to find that the key factors affecting the structure of 15 plankton communities in 15 salt lakes in Russia were pH, water temperature and water depth; Cheng Rong et al. used redundancy analysis (RDA) to find that chemical oxygen demand was the key factor affecting the abundance of plankton in the North Canal. It also proposes to strengthen the treatment of non-point source pollution and other measures to improve the pollution situation of the North Canal. Therefore, exploring the characteristics of plankton communities of different water bodies and their relationship with environmental factors can help to make an accurate assessment of the water environment status, and can also partially make up for the lack of physical and chemical monitoring and evaluation, which is of great significance for the monitoring and management of the lake ecological environment and the formulation and adjustment of ecosystem restoration and protection programs.
Baiyangdian (113°40′E-116°20′E, 38°10′N-40°00′N) is located in Xiong'an New District, Hebei Province, which belongs to the South Branch Lake of Daqinghe in the Haihe River Basin, with a water area of 366 km2 and an average annual water storage capacity of 1.32 billion m3. Baiyangdian is the most important water body functional area under the jurisdiction of Xiong'an New Area, and also the largest freshwater lake in North China, with rivers such as Tang River, CaoHe River, Fu River, Ping River and Baigou River entering the lake. In recent years, with the rapid development of the economy and the continuous increase of the population, the water quality of Baiyangdian has gradually deteriorated, and only the Fu river, Xiaoyi River and Baigou Diversion River of the 9 rivers in the upper reaches have water all year round, and the remaining 6 rivers have basically stopped flowing or seasonally have water, and the ecosystem of Baiyangdian Basin has shown a trend of degradation. In recent years, Chinese scholars have carried out a large number of studies on the structural characteristics of plankton and benthic communities in Baiyangdian and their relationship with environmental factors. For example, Li Na et al. studied the community structure changes of phytoplankton in Baiyangdian during the flood and non-flood seasons and the key factors during the flood season were total phosphorus (TP) and dissolved oxygen (DO). Sun Xiaoqiong et al. showed that temperature, transparency, nutrient salts, etc. affected the abundance and community composition characteristics of Baiyangdian branches and copepods; Yang Yufeng et al. showed that transparency, chlorophyll a, water depth, water temperature, dissolved oxygen, ammonia nitrogen, nitrate nitrogen and redox potential in the water environment factors were the key factors affecting the distribution of benthic animals. Although more studies have been carried out above, they are limited to the analysis between a single biological taxon and environmental factors, and the structural characteristic index of phytoplankton and zooplankton communities and aquatic environmental factors are not studied at the same time. In addition, since 2018, due to the construction of Xiong'an New Area and several ecological replenishments, the environment of Dian district has undergone certain changes, so it is particularly important to discuss the relationship between plankton community indicators and environmental factors in Dian District. In May, August and October 2018, sample collection and laboratory analysis of the water quality, phytoplankton and zooplankton of Baiyangdian were carried out respectively, and the temporal dynamic changes of plankton communities were analyzed according to the test results, and the water environment status of Baiyangdian area was evaluated according to the status of plankton. In order to provide certain scientific support for in-depth study of the dynamic change mechanism of the ecosystem in the Baiyangdian River Basin and the restoration of the water ecological environment in Xiong'an New Area.
<h1 class="pgc-h-arrow-right" data-track="11">1 materials and methods</h1>
<h1 class="pgc-h-arrow-right" data-track="12" >1.1 sample point layout</h1>
In this study, Baiyangdian was sampled three times in spring (May), summer (August), and autumn (October) in 2018. A total of five sampling points were set up in the study area, namely S1 (Nilizhuang), S2 (Wangjiazhai), S3 (Guangdian Zhangzhuang), S4 (Circle Head) and S5 (Duancun). Among them, S1 is located at the mouth of Fuhe and Pinghe, S5 is located at the mouth of Tanghe and Xiaoyihe, and S2-S4 is located in the center of Dianqu District, with developed tourism. The sampling point distribution is shown in Figure 1.
<h1 class="pgc-h-arrow-right" data-track="16" >1.2 Sample collection and processing</h1>
There are 7 environmental factors, including water temperature (WT), pH (pH), dissolved oxygen (DO), permanganate index (CODMn), ammonia nitrogen (NH3-N), total phosphorus (TP) and total nitrogen (TN). The sample analysis method was determined with reference to the "Water and Wastewater Monitoring and Analysis Method".
The qualitative phytoplankton samples were dragged for 3 min at 0.15 m underwater as a "∞" type at 0.15 m, and the collected phytoplankton were loaded into a 100 mL specimen bottle, plus 3 mL formalin fixed and brought back for analysis; the phytoplankton quantitative sample was taken from the vial, and 15 mL Of Rugots solution was added to the laboratory for analysis. Species identification was based on "Freshwater Algae in China— Systems, Classification and Ecology", and counted by 0.1 mL plankton counting frame. The qualitative samples of zooplankton were slowly trawled in the horizontal and vertical directions of No. 13 plankton net in the horizontal and vertical directions according to the "∞", and the quantitative samples were set in 3 upper and lower layers at each sampling point, and the water samples were collected with a 5 L water collector, and 20 L water samples were collected per layer, filtered and loaded into plastic bottles with No. 25 plankton nets, and fixed with 5% formalin solution (formaldehyde) and microscopically examined in the laboratory. Species identification refers to "Chinese Freshwater Rotifers", "Chinese Zoology • Freshwater Copepods", "Zoology of China • Freshwater Branches", and counted by 1 mL plankton counting frame.
<h1 class="pgc-h-arrow-right" data-track="19" >1.3 data analysis</h1>
The community characteristics of phytoplankton were analyzed by Shannon-Wiener Diversity Index, Margalef Species Richness Index, Pielou Uniformity Index, Biological Abundance, Density and Dominance, and the calculation formulas and evaluation criteria of each index were listed in Table 1.
Table 1 Community characteristic index and evaluation criteria
Table 1 Community characteristic index and evaluation criteria
The Kolmogorov-Smirnow (K-S) normal distribution test is used to determine whether the environmental factors conform to the normal distribution. The results show that the environmental factors all conform to the normal distribution. SpSS20.0 statistical software was used to perform independent sample t-tests on environmental factors. Using SPSS20.0 statistical software, the Pearson correlation analysis between the Baiyangdian plankton community characteristic index and environmental factors was carried out, where the R value represented the correlation size, the P value represented the significance between the two variables, generally requiring P<0.05 to be meaningful, the absolute value of R was generally strongly correlated between 0.7 and 1.0, weakly correlated between 0.3 and 0.7, and no correlation below 0.3 was considered to be relevant. In the correlation analysis, because the units of the community diversity index and the environmental factor are not uniform, the standard deviation of the community diversity index and the environmental factor data needs to be standardized.
<h1 class="pgc-h-arrow-right" data-track="40" >2 Results and analysis</h1>
<h1 class="pgc-h-arrow-right" data-track="41" >2.1 Baiyangdian physicochemical factor</h1>
In this study, the main water environment factors of Baiyangdian were mainly detected, and the results of the environmental factors of Baiyangdian water bodies during the survey period were listed in Table 2, and the seasonal differences of environmental factors were significant (P<0.05). The pH values of the three seasons of the water body were 8.60, 8.22 and 8.88, respectively, and the water body in the lake area was alkaline as a whole. DO, CODMn and TN decline from spring to summer and rise from summer to autumn, while TP does the opposite. NH3-N is on the rise overall. According to the "Surface Water Environmental Quality Standards", the Baiyangdian water body is class V water in summer and IV water in spring and autumn.
Table 2 Physical and chemical indicators of Baiyangdian water body
Table 2 Physicochemical water quality parameters in the Lake Baiyangdian
<col style="width: 88px;">
<col>
Period
Projects
WT
/℃
pH
DO'S
/mg· L-1
CODMn
NH3-N
TP
TN
Spring
average value
21.30
8.60
10.76
6.56
0.22
0.11
1.85
maximum
23.50
8.80
13.10
7.00
0.53
0.21
3.52
minimum
19.10
8.40
7.57
6.20
0.07
0.05
1.08
standard deviation
3.11
0.28
2.63
0.30
0.18
1.00
Summer season
30.54
8.22
2.67
6.40
0.56
0.16
1.25
31.00
4.75
7.80
1.19
0.35
2.19
30.20
7.90
1.42
5.60
0.06
0.84
0.31
0.26
1.32
0.85
0.39
0.13
0.54
Autumn season
16.06
8.88
7.40
6.94
0.81
2.08
19.30
9.41
8.96
2.17
0.20
4.88
15.00
5.36
0.29
0.98
1.83
0.38
1.31
0.88
0.78
1.60
<h1 class="pgc-h-arrow-right" data-track="153" >2.2 Characteristics of plankton communities in Baiyangdian</h1>
2.2.1 Species composition and dominant taxa
A total of 6 phytoplankton species and 74 species were detected in the Baiyangdian study area. Among them, the green algae phylum has the most species, a total of 32 species, accounting for 43.24% of the total number of species, followed by the diatom phylum, a total of 19 species, accounting for 24.68%, the remaining phyla have 14 species of cyanobacteria, accounting for 18.92%, 4 species of naked algae phylum, accounting for 5.41%, cryptoalgae phylum 3 species, accounting for 4.05%, and dinodiolum phylum 2 species, accounting for 2.70%. As can be seen from Figure 2, the Yodo area has the fewest species of phytoplankton in the summer and the most in the autumn. The dominant species of phytoplankton in Baiyangdian are 11 species in spring, 8 species in summer and 19 species in autumn. In spring and summer, cyanobacteria and green algae phylum dominate, while in autumn the dominant taxa of Diatom phylum, phylum naked algae, dinoflagellate phylum and cryptoalgae phylum appear (see Table 3).
A total of 22 species of zooplankton were detected in Baiyangdian, of which 16 species were rotifers, accounting for 72.73% of the total number of species; There are 4 species of phylum, accounting for 18.19% of the total number of species; There are 2 species of copepods, accounting for 9.09% of the total number of species. As can be seen from Figure 2, the Yodo area has the most zooplankton species in summer and the least in autumn. The dominant species of Zooplankton in Baiyangdian are 9 species in spring, 11 species in summer, and 8 species in autumn, all of which are absolutely dominant with rotifers. In addition, Brachionus calyciflorus, Brachionus angularis, Asplanchna priodonta, and neighboring Cyclops vicinus are dominant species in all three seasons with higher frequencies (see Table 3).
Table 3 Dominant species of plankton in Baiyangdian
Table 3 Dominant species of plankton in the Lake Baiyangdian
Category
Species class
Planktonic
plant
Cyanobacteria phylum
Point-shaped plasmodium (Merismopedia punctata)
+
Microcystis aeruginosa
Micro-flat crack algae (Merismopediatenuissima)
Fibrillant fishy algae (Anabaena osicellariordes)
Spirulina major
Chroococcus minor
Pseudo-ichthyosa (Pseudanabaena sp.)
Merismopedia minima
Phormidum tenus
Phylum Green Algae
Chlorella vulgaris
Scenedesmus quadricauda
Scenedesmus dimorphus
Schroederia spiralis
Crucigenia quadrata
Right-angled cruciferousis (Crucigenia roctangularis)
Oligocystis lacustris
Actinastrum hantzschii
Phylum Diatoms
Synedra acusvar
Cyclotella catenata
Melosira granulata
Short boat-shaped algae (Navicula exigua)
Cymbella pusilla
Nitzschia acicularis
Dinoflagellate phylum
Gymnodinium aerucyinosum
Naked algae phylum
Euglena oxyuris
Euglena deses
Cryptoalgae phylum
Cyanotic algae (Chroomonasv caudata)
Cryptomonas erosa
animal
Rotifers
Calyx calyciflorus (Brachionus calyciflorus)
Brachionus urceus
Brachionus capsuliflorus
Brachionus angularis
Brachionus diversicornis
Brachionus budapestiensis
Asplanchna priodonta
Keratella cochlearis
Curved-legged tortoise beetle (Keratella valga)
Lecane lunainermis
Cylindrum cylindrica
Needle cluster polygonal rotifer (Polyarthra trigla)
Filina longiseta
Branches
Simple arc flea (Bosmina coregoni)
Moina rectirostris
Copepods
Nearby cyclops vicinus
Valiant Sword Flea (Cyclops strenuus)
Note: The "+" in the table indicates that the species is the dominant species for this season
2.2.2 Plankton abundance
The average lake abundance of phytoplankton in spring was 403.50×105 cells/L, ranging from 330.93 ×105 to 454.21 ×105 cells/L; the average abundance of the whole lake in summer was 701.81×105 cells/L, with variations ranging from 415.30 ×105 to 1 005.6 ×105 cells/L; the average abundance of the whole lake in autumn was 131.12×105 cells/L. The variation range is between 85.20×105 to 145.4 ×105 cells/L (see Figure 3). The species of cyanobacteria and green algae phylum are the main taxa in spring, accounting for 72.05% and 24.07% of the total abundance, respectively, the cyanobacteria phylum occupies an absolute advantage in summer, accounting for 90.07% of the total abundance, and the autumn is similar to the spring, and the cyanobacteria phylum and the phylum green algae are the main taxa, accounting for 63.51% and 14.77% respectively.
The average density of zooplankton was 1 238 Ind./L in spring, ranging from 657 to 1 620 Ind./L; the average density of the whole lake in summer was 784 Ind./L, ranging from 250 to 1 610 Ind./L; and the average density of the whole lake in autumn was 586 Ind./L, ranging from 270 to 860 Ind./L (see Figure 3); Spring rotifers occupy an absolute advantage of 93.60%, summer succession is dominated by rotifers and copepods, the proportion of which is 83.16% and 10.97%, the proportion of radial feet in autumn increases to 29.19%, and the proportion of rotifers decreases to 60.74%.
2.2.3 Plankton community characteristic index and water quality evaluation
The phytoplankton community characteristic index is shown in Figure 4. The Shannon-Wiener Diversity Index averaged 1.490 in spring, 1.226 in summer, 2.036 in autumn, and α-medium pollution in spring and summer, and β-medium pollution in autumn. The Pielou Uniformity Index has a spring average of 0.531, a pollution level of Light Pollution, a Summer of 0.495, a Pollution Rating of Moderate Pollution, and a Fall of 0.805, and a Pollution Level of No Pollution. The Margalef Species Richness Index was 2.290 in spring, 1.500 in summer, 2.563 in autumn, and the pollution levels in spring and autumn were β-medium pollution, and the summer pollution level was α-medium pollution.
The zooplankton community characteristic index is shown in Figure 4. The Shannon-Wiener Diversity Index has a mean of 1.556 in spring, 1.863 in summer and 1.359 in autumn, with pollution levels of α-medium pollution. The Pielou Uniformity Index has an average of 0.845 in spring, 0.905 in summer, and 0.950 in autumn, with pollution levels of pollution-free. The Margalef Species Richness Index was 1.347 in spring and 1.727 in summer, with a pollution level of α-moderate pollution in spring and summer, and 0.630 in autumn, with a pollution level of heavy pollution.
The water pollution status reflected by the Baiyangdian plankton community diversity index is relatively consistent with the water quality evaluation results of the physicochemical factors in Baiyangdian, and the water pollution status reflected in the seasonal changes is also similar to the water quality evaluation results of the physical and chemical factors, which also shows that the diversity index has high application value in the water environment assessment.
<h1 class="pgc-h-arrow-right" data-track="370" >2.3 Relationship between plankton community structure and environmental factors</h1>
Pearson correlation analysis methods showed that (see Table 4), the Shannon-Wiener diversity index and Pielou uniformity index of spring phytoplankton communities showed a significant positive correlation with CODMn and TP (P<0.05), and Margalef species richness showed a significant negative correlation with WT and TP (P<0.05). The Shannon-Wiener diversity index and Pielou uniformity index of summer phytoplankton communities showed a significant negative correlation with TP (P<0.05), and Margalef species richness showed a significant negative correlation with pH and DO (P<0.05). The species richness of Margalef in autumn showed a significant negative correlation with DO and CODMn (P<0.05)
The Shannon-Wiener diversity index of the spring zooplankton community showed a significant positive correlation with CODMn (P<0.05), and the Margalef species richness showed a significant negative correlation with NH3-N and TP (P<0.05) and A significant correlation with TN (P<0.01). The Shannon-Wiener diversity index of summer zooplankton communities showed a significant negative correlation with NH3-N and TN (P<0.05), the Pielou uniformity index showed a significant positive correlation with CODMn (P<0.05), and the Margalef species richness showed a significant negative correlation with DO (P<0.05) and a significant positive correlation with TP (P<0.05). The Autumn Pielou Uniformity Index showed a significant positive correlation with CODMn (P<0.05).
In this study, the phytoplankton diversity index was most closely correlated with TP, CODMn and DO, with 4, 3 and 2 significant correlations, respectively, and the zooplankton diversity index was most closely correlated with CODMn, NH3-N and TN, with 3, 2 and 2 significant correlations, respectively.
<h1 class="pgc-h-arrow-right" data-track="374" >3 Discussion</h1>
<h1 class="pgc-h-arrow-right" data-track="375" >3.1 Community structure analysis of plankton in Baiyangdian</h1>
In this study, the community structure of Plankton in Baiyangdian changed significantly from season to season. From the analysis of phytoplankton community structure, due to the high nutrient salt content and suitable temperature in summer, the abundance of phytoplankton reaches a high level, mainly based on cyanobacterial phylum. This is due to the fact that cyanobacteria are more tolerant to high temperatures than other algae, and they usually gain a competitive advantage at high temperatures (25 to 35 °C) with rapid growth r countermeasures; In addition, when the phosphorus concentration in the water body is less than 0.2 mg/L, it is a restricted nutrient salt for cyanobacterial growth, and the higher phosphorus concentration in Baiyangdian in summer also promotes the growth and reproduction of cyanobacteria. The rapid reproduction of cyanobacteria in summer also inhibits the growth of other phytoplankton, resulting in a minimum phytoplankton species in the summer. The dominant species are mainly from the blue, green algae phylum and a small amount of diatom phylum in spring to the cyanobacteria phylum in summer and a small amount of green algae phylum and then to the more balanced community structure of each phyla in autumn, the summer community structure is more single, and the community characteristic index also reflects this, which is similar to the phytoplankton community structure of Taihu Lake.
From the perspective of zooplankton community structure, spring, summer and autumn species are similar in composition, and rotifers dominate. Rotifers have the characteristics of small individuals, short cycles and rapid development, and can quickly adapt to changes in the physical and chemical environment and changes in hydrological conditions in water bodies, so rotifers often occupy a dominant position in river and lake habitats. Zooplankton have a predatory relationship with phytoplankton, cyanobacteria have low nutritional value and the production of toxins is not conducive to the growth of zooplankton, but rotifers have high tolerance, so there are the most species of zooplankton in summer, and rotifers have an absolute advantage, but the density is relatively low. Spring-growing phytoplankton such as naked algae, green algae, and organic detritus formed after the death of aquatic organisms in the previous year are the bait that rotifers like to eat, and predators are less vigorous in the low temperature season, so rotifers can multiply in large numbers in the spring to form a peak. In addition, there are more species of clades than copepods, but the density is relatively low, which is similar to the results of many studies on the distribution of zooplankton taxa in rivers and lakes.
<h1 class="pgc-h-arrow-right" data-track="378" >3.2 Relationship between plankton communities and environmental factors in Baiyangdian</h1>
Plankton community structure is affected by a combination of environmental factors, and the effects of environmental factors on community structure in different water bodies are also different [9]. In this study, through the correlation analysis between the plankton community diversity index and the main environmental factors in Baiyangdian, it was found that the key factors affecting the characteristics of the phytoplankton community in spring were WT, CODMn and TP, pH, DO and TP in summer, DO and CODMn in autumn, NH3-N, CODMn, TN and TP in spring, DO, CODMn, NH3-N, TP and TN in summer, and CODMn in autumn. The key environmental factors that affect the characteristics of plankton communities are different in different seasons, indicating that the environmental factors of Baiyangdian have changed under the seasonal drive, and the changes in environmental factors will also lead to changes in the structure of plankton communities. Water temperature is an important environmental factor affecting the growth, development and community composition of phytoplankton, 10 ~ 30 °C diatoms have appeared, green algae can grow well at 18 ~ 30 °C, cyanobacteria can grow at a high water temperature of 40 °C, Baiyangdian in the spring, summer and autumn temperature range of 19 ~ 31 °C, suitable for the reproduction and growth of phytoplankton and zooplankton, consistent with the characteristics of a wide variety and abundance of plankton in Baiyangdian. The pH value has an important influence on the phytoplankton community structure, the alkaline environment is conducive to the photosynthesis of phytoplankton, and the alkaline water body has high algal productivity. Phosphorus, as an important nutrient in the composition of algal bodies, is considered to be one of the important limiting factors for phytoplankton growth. Studies have shown that green algae is more suitable for environments with high nitrogen and phosphorus ratios than cyanobacteria, and the phosphorus concentrations in the three seasons of Baiyangdian are similar, and the highest nitrogen concentration in autumn has a higher nitrogen-to-phosphorus ratio, so the number of green algae species in autumn is the highest. CODMn is a comprehensive index reflecting the degree of pollution of water bodies by organic pollutants and reducing inorganic substances, and has a significant positive correlation with the growth of phytoplankton. Community succession in zooplankton is generally closely related to food, predation, and competition, and environmental factors indirectly affect the community structure of zooplankton by acting directly on phytoplankton. Some cyanobacterial species such as microcystis are prone to form groups, and some filamentous cyanobacteria have relatively large particle sizes and are not easily preyed upon, thus affecting the growth of zooplankton. In addition, studies have shown that higher concentrations of ammonia nitrogen have a toxic effect on some zooplankton species, affecting their growth and reproduction. XIANG et al. studies have shown that when the concentration of NO2-N exceeds 1 mg/L, some zooplankton have a decrease in maternal reproduction. No concentrations of NO2-N were determined in this study, but the spring and summer zooplankton community characteristic indices were inversely correlated with nitrogen concentrations. The increase in water temperature in summer promotes the growth and reproduction of plankton in large quantities, and the oxygen consumption in this process leads to a decrease in the concentration of DO in the water, so the competition of plankton for dissolved oxygen makes dissolved oxygen a key factor affecting its community structure. The key factors affecting plankton are more complex in spring and summer, mainly affected by climate, and there is more rain in spring and summer, and frequent changes in the hydrological environment have an impact on environmental factors and plankton community structure, and plankton community structure changes are affected by a variety of factors.
Table 4 Correlation between plankton community indicators and environmental factors
Table 4 Correlation between plankton community indicators and environmental factors
phytoplankton
Shannon-Wiener
Diversity index
Pielou uniformity
index
Margalef species
Richness Index
-0.458
-0.171
-0.954*
0.291
0.413
-0.642
0.069
0.033
-0.735
-0.725
-0.758
-0.255
0.500
0.637
-0.806*
0.453
-0.587
-0.062
0.213
0.318
-0.278
0.426
0.507
-0.761*
-0.697
-0.693
-0.976*
0.894*
0.956*
0.366
0.100
0.232
-0.440
-0.043
-0.165
-0.856*
-0.378
-0.411
-0.106
-0.055
-0.163
0.340
0.834
0.617
0.829
0.999*
1.000*
-0.999*
-0.786*
-0.834*
0.662
0.347
0.812
0.077
-0.510
-0.554
-0.156
0.026
-0.071
0.238
0.859
0.602
0.807
zooplankton
-0.420
-0.621
0.386
0.491
-0.619
0.506
0.392
0.438
-0.575
-0.316
-0.495
0.020
-0.211
0.609
-0.02
0.511
0.372
0.472
0.595
-0.729*
-0.177
0.259
-0.793
0.779*
-0.253
0.526
0.552
0.783*
0.023
0.495
0.493*
0.265
-0.449
0.374
-0.781*
-0.825*
-0.474
0.331
0.165
-0.118
0.498
-0.175
0.325
-0.707*
-0.512
-0.603
0.740*
0.068
-0.326
-0.577
0.457
-0.879**
-0.787*
-0.370
0.322
-0.075
0.524
Note: * Significantly correlated at the 0.05 level (bilateral) and ** Significantly correlated at the 0.01 level (bilateral).
<h1 class="pgc-h-arrow-right" data-track="546" >3.3 Baiyangdian water quality evaluation</h1>
The dominant species of phytoplankton in Baiyangdian are mainly green algae and cyanobacteria that indicate the eutrophication status of the water body in spring and summer, and the dominant species in autumn are more average, and the water quality is better than that in spring and summer. Zooplankton mesopods such as horned arm-tailed rotifers, anterior segmental tyropod rotifers, Puda-tailed rotifers, and needle cluster multi-limbed rotifers are considered to be indicator organisms of α-medium fouling to β-medium stains and eutrophicationic water bodies.[44] In addition, based on the Shannon-Wiener Diversity Index, Pielou Uniformity Index and Margalef Species Richness, the water bodies in Baiyangdian are moderately polluted in spring and summer, and light-to-moderately polluted in autumn.
<h1 class="pgc-h-arrow-right" data-track="548" >3.4 Limitations and deficiencies of the study</h1>
This study continues the conventional sample points in the selection of sample points, which is conducive to further development of relevant research and reference in the future, but only 5 sample points are laid out in the whole Dian district, and the sample points are relatively few, which cannot fully display the situation of Baiyangdian compared to the complexity of the ecological environment in the Dian district. Due to time constraints, the monitoring of longer sequences has not been carried out, and it has not been reflected in seasonal changes and interannual changes, which is the shortcoming of this study, and future studies will be continued for a longer period of time, more samples, more water quality and environmental factors will be investigated in depth and related research will be carried out.
In this study, the influence relationship between environmental factors and phytoplanktonic biodiversity was ignored in the correlation analysis of water quality environmental factors, such as the effect and contribution rate of NH3-N on TN concentration, plankton organisms also contributed a large number of TP, TN, CODMn, phytoplankton photosynthesis and other submerged plants are the producers of DO, DO is an environmental factor affected by aquatic plants, rather than a driving factor, and the analysis parameters should be distinguished and selected in future studies.
<h1 class="pgc-h-arrow-right" data-track="551" >4 Conclusion</h1>
(1) According to the concentration values of water quality parameters such as TP, NH3-N, CODMn, TN, etc., the water quality of Baiyangdian water body is class V water in summer, and class IV water in spring and autumn.
(2) A total of 74 species of phytoplankton and 22 species of zooplankton were detected in the baiyangdian research area. The community structure of Plankton in Baiyangdian varies significantly from season to season, and the summer abundance of both types of plankton reaches the maximum. Phytoplankton are overwhelmingly dominant in spring and summer by cyanobacteria and green algae phylum, while in autumn diatom phylum, bare algae phylum, dinoflagellate phylum and cryptoalgae phylum are dominant taxa. Zooplankton are predominantly grouped in all seasons with rotifers.
(3) According to the water quality category analysis of the plankton community characteristic index, most of the index of Baiyangdian in different seasons shows medium pollution, and a small amount is light pollution or heavy pollution. The water pollution status reflected in the planktonic biodiversity index and the water quality evaluation results of physical and chemical factors are relatively consistent with the seasonal trend.
(4) The correlation between the phytoplankton diversity index and TP, CODMn and DO is larger, and the phytoplankton diversity index is more correlated with CODMn, NH3-N and TN.
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