Cấu trúc quần xã thực vật phù du trong các hồ chứa ở cao nguyên Lâm Viên, tỉnh Lâm Đồng (2)

- Species composition, density and distribution of phytoplankton in Xuan Huong reservoir, Tuyen Lam reservoir and Dan Kia reservoir.. OVERVIEW 1.1 The characteristics of tropical lakes a

INTRODUCTION

Currently, the pollution from agricultural activities and sources of domestic waste

in the Lam Vien highland has caused eutrophication to some water bodies, altering structure and function of aquatic ecosystems, in that phytoplankton communities are affected directly and indirectly The common phenomenon is the excessive growth of phytoplankton groups, usually cyanobacteria, damaging to other organisms in the water bodies To control this situation, we need identifying sources of impacts on basins and aquatic organisms In basins, phytoplankton is an important link in food web and is also the subject that affected by environmental factors Phytoplankton groups have different reactions when environmental conditions impact on them, through changes in composition, distribution, and growth Therefore, integrated analysis of phytoplankton responses to environmental factors can elucidate furthermore the effects of environmental conditions on phytoplankton From there, identifying which environmental factors that impact on the entire of aquatic ecosystem

Worldwide, the study factors that impact on phytoplankton was done quite soon and mostly in temperate areas These researches are less and later in the tropics There are a lot of lakes and reservoirs in Vietnam but are not yet much researches about them In particular, the studies on relationship between environmental factors and phytoplankton as well as between phytoplankton and other organismal groups have not been mentioned adequately Most researches are focusing on taxonomy

Until now, the researches on the impact of environmental factors on phytoplankton community structure in Vietnam as well as in Lam Vien highland based on year database have not been implemented Therefore, the study "Structure of phytoplankton communities in reservoirs at Lam Vien highland, Lam Dong Province"

in addition to contribution on taxonomy for the flora of freshwater microalgae in Tay Nguyen area of Vietnam, it also help understanding clearly the responses of phytoplankton to environmental conditions as well as identifying dominant environmental factors that impact on aquatic ecosystems

At the practical level, identifying which main impact on aquatic organisms, including phytoplankton community, will be the basis of science, support to management, protection of biodiversity of water resources in Lam Vien highland

- Species composition, density and distribution of phytoplankton in Xuan Huong reservoir, Tuyen Lam reservoir and Dan Kia reservoir

- The status of the waters of Xuan Huong reservoir, Tuyen Lam reservoir and Dan Kia reservoir

- The relationship between phytoplankton and environmental characteristics of each reservoir

- The impact of nutrition and grazing on growth of phytoplankton

- Simulation and forecasting trends of change in ecosystem of reservoirs by modeling

 Scientific contributions and applied aspects

- Complementing database for tropical phytoplankton flora in general, tropical highland in particular Providing some information for phytoplankton researches and applications

- Determining impacts of environmental factors on water bodies as well as on phytoplankton, the basis for building management solutions, effective use and proper exploitation of local water sources

- Contributing to find causes of excessive growth of phytoplankton in lakes and resaervoirs, the basis for restricting outbreak of phytoplankton, especially cyanobacteria blooms in reservoirs at Lam Vien highland

CHAPTER I OVERVIEW 1.1 The characteristics of tropical lakes and reservoirs

1.1.1 Overview

1.1.2 The temperature, stratification and mixing in water column

1.1.3 Radiation and clarity

1.1.4 Nutrition and solutes

1.1.5 Food webs, top-down and bottom-up control in lakes and reservoirs

1.2 Morphological characteristics and classification of freshwater phytoplankton 1.2.1 Morphological characteristics and classification of freshwater phytoplankton 1.2.2 Groups of freshwater phytoplankton

1.3 Ecology of phytoplankton

1.3.1 Light and photosynthesis of phytoplankton

1.3.2 Influence of temperature, stratification and mixing on phytoplankton

1.3.3 Metabolism and nutritional absorption of phytoplankton

1.3.4 Survival strategies of phytoplankton

1.4 Variation in phytoplankton community over time

1.4.1 The short-term changes (changes in molecules and cells)

1.4.2 Changes in medium term (phytoplankton community succession)

1.4.3 The long-term fluctuations (fluctuates by year)

1.5 Spatial distribution of phytoplankton

1.5.1 Voluntary movement of phytoplankton in water column

1.5.2 Passive movement of phytoplankton in water column

1.5.3 Loss phytoplankton in basins

1.6 AQUATOX model

1.6.1 AQUATOX model overview

1.6.2 Application of AQUATOX model

1.7 Some characteristics of studied area

1.7.1 Natural conditions of Lam Vien highland

1.7.2 Characteristics of reservoirs in Lam Vien highland

1.8 Situation of phytoplankton study in the world and Vietnam

CHAPTER 2 MATERIALS AND METHODS 2.1 Studied subjects

Phytoplankton and characteristics of water in 3 reservoirs, Xuan Huong, Tuyen Lam and Dan Kia

2.2 Materials and methods

2.2.1 At the field

At each reservoir, sampling at 3 stations At each station, sampling and measuring water parameters at 2 layers Frequency of survey is once a month, from 11/2013 to 10/2014 Flow rate, water temperature, depth of reservoir, Secchi depth, pH, DO, turbidity, light intensity were measured by handheld electronic devices Collecting water samples for analyzing chemical and biological parameters

2.2.2 Experiments

2.2.2.1 Fixing cells, qualitative and quantitative phytoplankton

Samples were fixed with 1% Lugol solution and formaldehyde solution of acetic acid (FAA) 2% Phytoplankton identification was based on classification keys of freshwater phytoplankton Quantitative forms, one liter of water was fixed by Lugol 1% and 2% FAA, within about 48 hours, siphon off above portion of water to remain

100 ml of water Let standing within 24 hours and then siphon off 20 ml remain water Taking 1 ml of this one for counting by using Sedgewich – Rafter chamber 2.2.2.2 Fixed cells, qualitative and quantitative zooplankton

Samples of quantitative zooplankton were fixed by a solution to final formadehyde concentration is 4% Analysizing zooplankton at Marine Plankton Department, Institute of Oceanography Zooplankton taxa were photographed, the quantitative zooplankton results are managed on MS-Excel

2.2.2.3 Analysis of chemical parameters

Nutrition parameters are defined according to APHA (1995, 2005) Determination of chlorophyll a by UV-Vis 1020 – H, according to APHA (1995) Fecal coliform is determined by culturing multiple tubes method, most probable number, 9221 APHA (1999) Pesticide residues were analyzed at Environmental Research Institute, Dalat University

2.2.2.4 Experiments to determine plankton biological rates

Bottom-up experiments arranged by Severiano (2012) Top-down experiments arranged by Landry & Hasset (1982) and Evans et al., (2003)

2.2.2.5 Calculation of phytoplankton biomass

Phytoplankton biomass is calculated according to Wetzel et al., (2001)

2.2.2.5 Running AQUATOX model

AQUATOX model was applied to assess impact of flows into Dan Kia reservoir 2.2.2.6 Application of statistical softwares and models

Analyzing significant differences between two properties by analysising variances (ANOVA) base on MS-excel Data normalization, correlation analysis, regression by Statgraphic 5.0 statistical software Canonical-correlation analysis (CCA) between phytoplankton and environmental factors base on CANOCO 4.5 software Correlation analysis - RDA (Redundancy Analysis) for estimating biomass variability of morphological groups of phytoplankton and environmental factors was performed base on CANOCO 4.5 software Analysis Shannon index (H'), Simpson dominance index (D) with Primer 6.0 software

CHAPTER 3 RESULTS AND DISCUSSION 3.1 Species composition, density and distribution of phytoplankton in the reservoirs 3.1.1 Species composition of phytoplankton in Xuan Huong, Tuyen Lam and Dan Kia

3.1.1.1 Species composition of phytoplankton in Xuan Huong reservoir

Total taxa of phytoplankton in

reservoir are 112, belonging to 7 phyla, including Chlorophyta (60 taxa, 53%), Cyanophyta (18 taxa, 16%), Euglenophyta (16 taxa, 14%), Bacillariophyta (8 taxa accounting for 7%) Dinophyta (4 taxa, accounting for 4%) Both Cryptophyta and Chrysophyta has 3 taxa, accounting for 3% of total taxa of phytoplankton (Figure 3.1)

Species composition of phytoplankton in Xuan Huong reservoir is a typicalone of phytoplankton in lentic waters with dominant species belong to green algae, and also has characteristics of eutrophic water-bodies with advantage of Cyanophyta density

Cyanobacteria density accounting for 80% of phytoplankton in the reservoir throughout the year (Figure 3.1B) Of the seven phyla in Xuan Huong reservoir, Chrysophyta density is the lowest Although Euglenophyta do not contribute significantly in density, they contributed significantly in biomass due to their cell size

Of three reservoirs, Xuan Huong had the highest number of taxa, as well as the density phytoplankton concentrated in a few taxa Xuan Huong reservoir receives water from upstream sides So, phytoplankton species composition perhaps related to addition of these taxa from its basins

Overall, the number of phytoplankton species in Xuan Huong reservoir is high but there are many species in low frequency, this maybe related to additional species temporarily from basins The density and biomass of phytoplankton are concentrated

in some taxa of Cyanophyta phylum, the group dominant throughout the year

3.1.1.2 Species composition of phytoplankton in Tuyen Lam reservoir

There are 6 phyla

in Tuyen Lam reservoir, with 43 taxa Among

them, Chlorophyta contained 25 taxa, accounting

Bacillariophyta and Cyanophyta contained 6 taxa, accounting for 14%; Dinophyta and Chrysophyta contained 3 taxa, accounting for 7% and 2 taxa, accounting for 5% respectively Euglenophyta phylum only has 1 taxon, representing 2% (Figure 3.2)

Phytoplankton in Tuyen Lam reservoir also featured lentic waters with advantage belonging to Chlorophyta phylum (Figure 3.2A) According to density, Cyanophyta has the highest density (Figure 3.2b) but base on biomass, Dinophyta was the most dominant group (Figure 3.2C) Some Chlorophyta genera are common, they are Desmids group (Desmidium, Coelastrum, Elakatothrix, Pleurotaenium, .), these genera usually present in less dirty waters (Reynolds, 2006)

There are two dominant phyla in Tuyen Lam reservoir, Cyanophyta and Dinophyta However, while filamentous cyanobacteria was dominant in Xuan Huong

reservoir, colony cyanobacteria was dominant in Tuyen Lam reservoir Two Dinophyta dominant genera are Ceratium and Peridinium

3.1.1.3 Phytoplankton species composition of Dan Kia reservoir

Dan Kia reservoir has 44 taxa, distributed in 7 phyla, including Chlorophyta, 17 taxa, accounting for 39%; Bacillariophyta, 11 taxa, accounting for 25%; Cyanophyta,

6 taxa, accounting for 14%; Chrysophyta, 5 taxa, accounting for 11%; Dinophyta, 2 taxa, accounting for 4.5%; Euglenophyta also 2 taxa, 4.5% and 1 Cryptophyta taxon, representing 2% of total number of phytoplankton species in Dan Kia reservoir Though number of Chlorophyta taxa was lower than the others, this phylum was still

dominant in number of species (Figure 3.3a) Bacillariophyta was dominant in Dan Kia reservoir both in species composition, density and

biomass Cryptophyta accounting for only 2% of total taxa but they contributed not less in density and biomass of phytoplankton (Figure 3.3a, 3.3b and 3.3C)

In short, species composition of phytoplankton was not the same in three reservoirs Th number of phytoplankton species was the highest in Ho Xuan Huong,

112 taxa Two remaining reservoirs had similar numbers, 43 and 44 taxa respectively for Tuyen Lam and Dan Kia Especially, comparing with similar reservoirs in the region (Le Thuong, 2010) showed that while Chrysophyta and Cryptophyta were found in studied reservoirs but they are completely absent in Eanhai reservoir, Easoup reservoir and Dak Ming reservoir Maybe, these groups distribute typically in some high mountains, low heat background around year Percentage of phyla in studied reservoirs is similar to reservoirs in the region, especially there is abundance and diversity of Chlorophyta in all

3.1.1.4 Biological diversity of phytoplankton in the reservoirs

No seasonal differences in species diversity

phytoplankton in Xuan Huong reservoir (T-test,

p = 0.106) and Dan Kia reservoir (T-test, p = 0.285), but this difference occurred in Tuyen Lam reservoir (T-test, p = 0.016) Species diversity index of phytoplankton was highest in December in Tuyen Lam reservoir (2.24) and the lowest in October in Xuan Huong reservoir (0.51) H’ index of Tuyen Lam reservoir, Dan Kia reservoir was higher of Xuan Huong reservoir (T-test, p = 0.048; p = 0.004) Meanwhile, there was no difference between Dan Kia reservoir and Tuyen Lam reservoir (T-test, p = 0.382) on this index Phytoplankton species diversity of Xuan Huong reservoir was the lowest among them

3.1.1.5 Characteristics of phytoplankton community structure base on morphological

Table 3.6 Morphological - function groups presence in the studied reservoirs

According to Reynolds et al., (2002), D and Y group were in Xuan Huong reservoir and Dan Kia reservoir but completely absent in Tuyen Lam reservoir D and

Y are the groups that characterized distribution in the shallow, turbid reservoirs, and

susceptible to change or are affected by outside activities In this case, environmental and biological data in Dan Kia, Xuan Huong are consistent with above statements Among groups according to Reynolds et al., (2002), only LM present in three reservoirs, this group is known commonly present in high level of nutrition Thus, LM

is not a good indicator for nutritional status but it is an evidence that functional morphological groups reflects nature of ecosystem The groups only present in Xuan Huong reservoir is H1 (typically in eutrophic, shallow, non-stratified reservoir), W1 (rich organic) and W2 (shallow, medium - eutrophic nutrient water bodies) all fit physic, chemical conditions that has been investigated for the reservoirs Similarly, N group (distributed at mixing reservoirs, 2-3 m thickness), was present only in Tuyen Lam reservoir WS group (in rich organic water bodies from decomposition process of plant; neutral pH), was present only in Dan Kia reservoir

Figure 3.5 RDA chart of environmental factors and functional - morphological groups according to Reynolds et al., (2002) Trans = Transparency Secchi, L

= light intensity, T = temperature, Cond

= conductivity, DO = dissolved oxygen,

TP = total phosphorus, phosphate PO4 =;

TN = total nitrogen, NH4 = ammonium nitrate NO3 =

Overall, the survey results on hydraulic, physic, chemical conditions in studied reservoirs fitted with ecological characteristics that morphological - function groups indicated However, there were some groups that featured in each water body where

they present no resemblance to the survey results For example, A group (at Xuan Huong and Dan Kia) distribute in clean, deep, poor nutrient water bodies (Reynolds et al., 2002) while these reservoirs are not clean, shallow and eutrophic So, we can not completely rely on this system for monitoring quality, which should be combined with multivariate analysis between morphological-function groups and environmental factors Multivariate analysis techniques are often applied is RDA (Legendre, 1998) RDA analysis results between environmental factors and functional-morphological groups according to Reynolds et al., (2002) at Xuan Huong reservoir (Figure 3.5A) shows that in the first axis, morphological-function groups (including A group) correlate mainly with light intensity, concentration of nitrate and TN Meanwhile, the second axis correlates mainly with TP RDA chart (Figure 3.5C) also shows that A group correlate with nitrogen and phosphorus Thus, the presence of A group maybe related to nutritional status of water bodies Overall, three functional - morphological systems can be applied to evaluate characteristics of aquatic ecosystems

3.1.2 Variation of phytoplankton density in Xuan Huong, Tuyen Lam and Dan Kia

3.1.2.1 Variation of phytoplankton density in Xuan Huong reservoir

Except Cyanophyta and Chlorophyta, all remaining phyla in Xuan Huong reservoir did not differ according to layer (Table 3.8)

Table 3.8 Density of phytoplankton in Xuan Huong reservoir

The dominance of Cyanophyta density is one of the characteristics of phytoplankton in Xuan Huong reservoir At time of algae blooms, density of Cyanophyta at the surface increased up to hundreds of millions of cells/liter The studied results showed that shallow, eutrophic, turbidity and no stratification reservoir

could be characteristics enabling algae blooms in Xuan Huong reservoir These conditions are close to ecological characteristics for excessive development of Cyanophyta (Reynolds, 2006) Density of phytoplankton groups in Xuan Huong reservoir varied according to season (Table 3.8) Density of most groups did not differ according to layer, except Cyanophyta (ANOVA, p = 0.039) and Chlorophyta (ANOVA, p = 0.001)

3.1.2.2 Variation of phytoplankton density in Tuyen Lam reservoir

Among phyla of phytoplankton in Tuyen Lam reservoir, Cyanophyta and Chrysophyta did not differ according to layer (Table 3.9) On other hand, only Cyanophyta (ANOVA, p = 0.022) and Chlorophyta (ANOVA, p = 0.046) are different according to season at the surface layer and cell density higher than in dry season

Table 3.9 Density of phytoplankton Tuyen Lam reservoir

Density of Chlorophyta, Bacillariophyta, Dinophyta fluctuated according to layer,

at the surface layer was higher than at the bottom layer Density of diatoms in bottom layer varied according to season (ANOVA, p = 0027), in dry season is higher in rainy season

Phytoplankton density of Tuyen Lam reservoir was much lower than in Xuan Huong reservoir Cyanophyta is also dominant group in this one However, while filamentous cyanobacteria is dominant in Xuan Huong reservoir, colony cyanobacteria is dominant in Tuyen Lam reservoir Perimidium and Ceratium are dominant genera in density and biomass, due to size of their cells These genera is typical for organisms that has K strategy, advantage in environments that density of higher organisms and concentration of nutrients is low relatively (Sigee, 2004) 3.1.2.3 Variation of phytoplankton density in Dan Kia reservoir

Density of Bacillariophyta and Dinophyta are different according to season and layer, at the surface layer is higher than at the bottom layer In particular, density of

Bacillariophyta was higher in dry season than in rainy season Density of algal cells in Dan Kia reservoir was very low Most of algal density was higher in rainy season than

in dry season, cell density in the surface layer was higher than in the bottom layer (Table 3.10)

Density and biomass of Chrysophyta was quite high in Dan Kia reservoir Chrysophyta are known as adapting to changes of nutrient concentrations in water Especially, Dinobryon is a mixotrophic genus (Kristiansen, 2005), dominant throughout year While concentration of inorganic nutrients (N, P) in Dan Kia reservoir unlimited growth of phytoplankton, sources of remaining energy, such as light, is very noticeable Dan Kia reservoir is also very high turbidity, this is the factor limiting penetration of light into water In this case, the mixotrophic lifestyle will advance over nursing Diatom is dominant in Dan Kia reservoir both density and biomass Some diatom species are suitable for high turbidity conditions and rich nutrient (Bellinger & Sigee, 2010) Obviously conditions, environmental water of Dan Kia reservoir is quite suitable for the growth of diatoms

Table 3.10 Density of phytoplankton in Dan Kia reservoir

In short, most of phytoplankton groups in the reservoirs have seasonal fluctuations While filamentous cyanobacteria was dominant in Xuan Huong reservoir, colony cyanobacteria was dominant in Tuyen Lam reservoir Besides, in Tuyen Lam reservoir also appeared more a dominant one, that is Dinophyta While, Diatoms and Chrysophyta are dominant in Dan Kia reservoir

3.2 Assessment water status of Xuan Huong, Tuyen Lam and Dan Kia reservoir 3.2.1 Water status of Xuan Huong reservoir

Hydraulic, physical, chemical and biological parameters of water in Xuan Huong reservoir were surveyed from 11/2013 to 10/2014, are shown in Table 3.11

Table 3.11 Hydraulic, physical, chemical and biological parameters of water in

Xuan Huong reservoir Hydraulic, physical,

chemical and

biological

parameters

Dry season (From November to March)

Rainy season (From November to March)

Significant differences p≤0.05 Min Max Average

±SD Min Max Average ±SD

Seas

on Layer Water depth (m) 0.9 4.6 2.61±1.44 1.0 4.9 2.86±1.46 0.616 * Secchi depth (m) 0.25 0.4 0.34±0.06 0.25 0.6 0.45±0.11 0.001 * Light intensity (lux) 353 4213 2215±940 1466 31033 8147±7898 0.006 * Water temperature (°C)

Surface layer

Bottom layer

15.07 15.20

22.80 22.87 19.69±2.60 19.65±2.58

15.57 15.53

22.13 22.1

18.86±2.32 18.16±2.27

0.321 0.075 0.465

pH

Surface layer

Bottom layer

7.81 7.57

9.53 9.50 8.97±0.45 8.91±0.48

6.28 6.30

8.80 9.57

7.94±0.83 7.83±0.96

0.001 0.001 0.675

DO (mg/l)

Surface layer

Bottom layer

4.60 4.77

6.33 6.24 5.36±0.56 5.37±0.44

3.89 4.12

6.54 6.86

5.07±0.65 5.18±0.72

0.188 0.389 0.314 Conductivity

(µS/cm)

Surface layer

Bottom layer

231.67 216.33

254.00 252.67 234.33±13.6 235.00±11.9

174.33 174.67

238.17 240.00

200.17±20.4 201.13±20.1

0.001 0.001 0.880 Turbidity (NTU)

Surface layer

Bottom layer

33.57 33.83

89.73 104.67 57.55±19.29 59.35±21.26

20.86 23.10

60.97 104.33

39.76±14.62 49.27±25.85

0.003 0.224 0.221

3.07 3.93 18.95 23.74

12.30±4.42 12.51±5.52

0.001 0.001 0.862

5.12 5.80 2.07±1.55 2.31±1.68

0.74 0.79

3.17 3.24

1.95±0.74 2.01±0.68

0.749 0.472 0.624

TN (mg/l )

Surface layer

Bottom layer

3.97 3.01 18.73 18.89 10.56±4.71 11.07±4.53

7.76 8.38 24.43 30.94

17.85±4.62 18.19±6.15

0.001 0.001 0.781

2.08 1.99 1.10±0.58 1.24±0.47

0.17 0.17

2.53 3.39

1.10±0.60 1.42±0.99

0.975 0.522 0.14

TP (mg/l )

Surface layer

Bottom layer

3.35 4.06

8.33 8.08 5.38±1.70 5.76±1.31

0.69 0.51

3.68 13.47

2.26±0.92 3.75±3.63

0.001 0.048 0.096 N:P

Surface layer

Bottom layer

1.13/1 1.08/1

2.87/1 2.46/1 1.98±0.66 1.91±0.54

3.55/1 1.59/1 22.77/1 20.52/1

10.32±6.24 9.05±7.32

0.014 0.057 0.771 Pesticides (µg/l)

* 10.23±7.68

0.010 0.024 0.519 Chlorophyll a (µg/l)

Surface layer

Bottom layer

49.51 19.84 247.93 173.34 165.96±55.5 114.56±43.2

32.79 15.61 161.19 131.71

103.37±39.65 55.27±30.73

0.001 0.001 0.001 Cladocera(indi./l)

Surface layer

Bottom layer

0.00 0.08

3.14 8.50 1.15±1.19 3.83±2.77

0.83 1.25 13.75 12.92

7.34±3.68 6.99±3.50

0.001 0.006 0.805 Copepoda (indi./l)

Surface layer

Bottom layer

0.00 1.08 19.92 18.20 3.60±4.87 6.98±5.56

0.00 1.33

9.80 13.44

5.20±2.81 5.70±3.06

0.221 0.381 0.079 Rotatoria (indi./l)

Surface layer

Bottom layer

0.00 0.00 17.50 9.32 3.33±4.54 3.55±2.95

1.67 0.33 28.22 27.13

10.92±7.16 10.21±6.94

0.001 0.001 0.842 Larvae (indi./l)

Surface layer 0.00 35.33 5.95±10.56 0.89 10.33 5.29±2.68 0.788 0.999