Int. J. Aquat. Biol. (2016) 4(6): 360-369; DOI:
ISSN: 2322-5270; P-ISSN: 2383-0956
Journal homepage: www.ij-aquaticbiology.com
© 2016 Iranian Society of Ichthyology
Original Article
Diversity of Phytoplankton of a sub-tropical reservoir of Mizoram, northeast India
Bhushan Kumar Sharma*,1 Lalthlamuana Pachuau
Freshwater Biology Laboratory, Department of Zoology, North-Eastern Hill University, Permanent campus, Shillong-793 022, Meghalaya, India.
Article history:
Received 4 August 2016
Accepted 29 October 2016
Available online 2 5 December 2016
Keywords:
Abundance
Composition
Richness
Diversity indices
Ecology
Abstract: Phytoplankton of Khawiva reservoir of Mizoram, northeast India (NEI) revealed a total
of 55 species; nearly concurrent mean monthly richness and high community similarities (vide
Sørensen index) during two years affirmed homogeneity in its species composition. Phytoplankton
comprised dominant component (61.1±14.3%) of net plankton and recorded wider density variations.
Chlorophyta influenced phytoplankton abundance with quantitative importance of Staurastrum spp.
> Xanthidium spp. > Cosmarium spp. in particular. Bacillariophyta formed subdominant group;
Cryptophyta and Cyanophyta showed limited importance; and Euglenophyta and Dinophyta recorded
poor densities. Phytoplankton is characterized by moderate species diversity, high evenness and low
dominance but with wide variations. Richness, abundance and species diversity followed no definite
patterns of monthly variations during two years. Insignificant influence of individual abiotic factors
on phytoplankton assemblages coupled with low cumulative influence of fifteen abiotic parameters
(vide CCA) yielded little insight on overall role of abiotic parameters.
Introduction
Limnological studies in India began nearly one
century ago and culminated in several investigations
on reservoir ecology from different regions (Jana,
1998) and dealing with phytoplankton diversity.
There is yet paucity of information on phytoplankton
of sub-tropical environs of this country in general
and from northeast India (NEI) in particular
(Sharma, 2015). The related studies from NEI are
limited to analysis of these primary producers and
fish-food organisms of certain reservoirs of
Meghalaya (Sharma, 1995; Sharma and Lyngdoh,
2003; Sharma and Lyngskor, 2003), while other
notable contributions related to certain floodplain
lakes of this region (Sharma, 2004, 2010, 2012,
2015). The present study forms a part of first
limnological endeavor undertaken by the authors
from Mizoram state of NEI; the results on
zooplankton diversity are published earlier by
Sharma and Pachuau (2013). Nevertheless, this
communication on phytoplankton diversity of
* Corresponding author: Bhushan Kumar Sharma
E-mail address: profbksharma@gmail.com
Khawiva reservoir merits ecological value in view of
the stated lacunae. The observations are made on
monthly variations of phytoplankton assemblages of
the sampled reservoir for a period of two years with
emphasis on composition, richness, community
similarities, abundance, species diversity, domin-
ance and evenness. In addition, individual and
cumulative influence of abiotic factors is analyzed to
assess their limnological value vis-à-vis phyto-
plankton diversity.
Materials and Methods
Our observations are based on limnology study
(November, 2005-October, 2007) of Khawiva
reservoir (22o35'N, 93o 47'E; area: about 10 ha;
maximum depth: 40 m), Lunglei district, Mizoram
state (Fig. 1A-C), NEI; located nearly 12 km from
Lunglei town, it was commissioned in 1988 on
Khawiva River with a capacity of generating 1050
kw power. This reservoir is surrounded by
Phyllanthus sp., Cyperus sp., Eupatorium sp.,
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Int. J. Aquat. Biol. (2016) 4(6): 360-369
Farmaria sp., and Centella sp., and itself lacked any
aquatic vegetation.
Water as well as qualitative and quantitative
plankton samples was collected at monthly intervals
at two sampling stations for a period of two years as
per details of Sharma and Pachuau (2013). Water
temperature, pH and specific conductivity were
recorded using the field probes; rainfall data was
collected from Lunglei meteorological station;
Winkler’s method was used for estimation of
dissolved oxygen and APHA (1992) was followed to
analyze the rest of the abiotic factors. The
phytoplankton was identified following the works of
Islam and Haroon (1980), Adoni et al. (1985) and
Fritter and Manuel (1986). Quantitative enumeration
of phytoplankton and its constituent taxa was done
with a Sedgewick-Rafter counting cell and
abundance was expressed as n/L. Phytoplankton
community similarities, species diversity, domin-
ance and evenness were calculated vide Sørensen,
Shannon, Berger-Parker and Pileou indices,
respectively (Ludwig and Reynolds, 1988;
Magurran, 1988). ANOVA (two-way) was used to
ascertain significance of temporal variations of
different parameters; and SPSS (version 20.0) was
used for the hierarchical cluster analysis. Pearson’s
correlation coefficients (r) were used to analyze
ecological correlations amongst abiotic-vis-biotic
attributes; P-values were calculated and significance
was ascertained following Bonferroni corrections.
XLSTAT (2012) was used for the canonical
correspondence analysis to assess cumulative
influence of fifteen abiotic factors namely rainfall,
water temperature, specific conductivity, pH,
dissolved oxygen, free carbon dioxide, total
alkalinity, total hardness, chloride, sulphate,
phosphate, nitrate, silicate, dissolved organic matter
and total dissolved solids on phytoplankton
assemblages.
Results
The variations in abiotic parameters (annual ranges
and mean ±SD) of Khawiva reservoir observed
during two years as well as during the study period
are indicated in Table 1. Water temperature ranged
between 22.1±4.0oC and total monthly rainfall
ranged between 270.5±302.6 mm during the study
period; specific conductivity, pH, dissolved oxygen,
free carbon dioxide, total alkalinity, total hardness,
chloride and sulphate varied between 40.5±11.0 µS
cm-1, 6.64±0.31 mg L-1, 7.7±1.6 mg L-1, 11.5±3.0
mg L-1, 31.6±4.7 mg L-1, 30.0±8.0 mg L-1, 7.9±3.5
mg L-1 and 1.890±1.478 mg L-1, while phosphate,
nitrate, silicate and dissolved organic matter varied
Figure 1. (A) Map of India showing Mizoram state (red color), (B) district map of Mizoram showing Lunglei district with location of Khawiva
reservoir and (C) Khawiva reservoir (Google photo) with sampling station marked by dots.
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Sharma and Pachuau/ Phytoplankton diversity of Khawiva reservoir of Mizoram, northeast India
between 0.089±0.093 mg L-1, 0.185±0.088 mg L-1,
0.417± 0.364 mg L-1, and 0.302±0.582 mg L-1 during
the study period, respectively. ANOVA registered
significant annual variations of pH (F1, 23=7.553,
P=0.019) and sulphate (F1, 23=9.465, P=0.011),
while specific conductivity (F11, 23=3.589, P=0.022)
and hardness (F11, 23=3.238, P=0.032) recorded
significant monthly variations.
The richness and density variations (ranges and
mean ±SD) of phytoplankton are presented in Table
2. We observed 55 species of phytoplankton; the
monthly richness (Fig. 2) ranged between 24-38 and
20-41 species, and community similarities varied
between 51.7-84.4% and 50.0-95.8%. Chlorophyta,
the diverse group, is represented by 22±4 and 23±6
species during two years, respectively. The
hierarchical cluster analyses, based on Sørensen’s
community similarities, are presented in Figures 3-4.
The phytoplankton density varied between 132-1199
(369±253 n/L) and it comprised 61.1±14.3% of net
plankton; Chlorophyta exhibited wide density
variations (57-1087, 239±238 n/L) and it formed
between 59.5±21.9% of total phytoplankton during
the study period; Bacillariophyta (71±62 n/L),
Cyanophyta (24±52 n/L) and Cryptophyta (26±44
n/L) comprised 21.2±15.2%, 8.1±17.7% and
6.1±6.9% of phytoplankton abundance, respectively
in this study while Euglenophyta (9±19 n/L) and
Dinophyta ((1±1 n/L) depicted poor abundance. The
species diversity (1.693-3.399, 2.607±0.451),
dominance (0.080-0.649, 0.265±0.151) and
evenness (0.472-0.921, 0.760±0.119) recorded wide
variations. The monthly variations of abundance of
phytoplankton, Chlorophyta and Bacillariophyta,
and that of species diversity are presented in Figures
5-8, respectively. This study indicated quantitative
importance of Staurastrum spp. (100±142 n/L),
Xanthidium spp. (73±83 n/L) and Cosmarium spp.
(32±30 n/L); Staurastrum inflexum (36±42 n/L),
S. nonanum (23±57 n/L), S. kurzianum (13±16 n/L),
S. chaetoceras (11±20 n/L), Oscillatoria sp. (23±52
n/L), Frustulia sp. (22±17 n/L) and Navicula sp.
(19±23 n/L) are important individual taxa.
Our results lacked significant influence of any
individual abiotic parameter on richness and
abundance of phytoplankton as well as on abundance
of the Chlorophyta, Bacillariophyta and Cyanophyta
Table 1. Temporal variations of abiotic parameters (Modified after Sharma and Pachuau, 2013).
Parameters
First year Second year Study Period
Range, Mean±SD Range, Mean±SD Range, Mean±SD
Rainfall (mm) 0-890.0, 268.7±283.4 0-901.8, 272.4±320.7 0-901.8, 270.5±302.6
Water temperature (°C) 14.5-28.0, 22.4±4.0 14.0-27.0, 21.7±3.9 14.0-28.0, 22.1±4.0
Specific conductivity (µS cm-1) 20.0-62.0, 42.8±13.5 28.0-50.0, 38.3±7.2 20.0-62.0, 40.5±11.0
pH 6.34-7.18, 6.81±0.24 5.86-6.83, 6.48±0.29 5.86-7.18, 6.64±0.31
Dissolved oxygen (mg L-1) 5.6-10.4, 8.1±1.5 4.8-9.6, 7.2±1.6 4.8-10.4, 7.7±1.6
Free carbon dioxide (mg L-1) 8.0-16.0, 12.8±2.6 6.0-14.0, 10.2±2.8 6.0-16.0, 11.5±3.0
Total alkalinity (mg L-1) 24.0-40.0, 32.3±5.5 26.0-34.0, 30.8±3.6 24.0-40.0, 31.6±4.7
Total hardness (mg L-1) 18.0-46.0, 30.3±9.5 22.0-38.0, 29.7±6.2 18.0-38.0, 30.0±8.0
Chloride (mg L-1) 1.0-12.0, 9.2±3.6 4.0-11.0, 6.6±2.8 1.0-11.0, 7.9±3.5
Sulphate (mg L-1) 0.714-2.584, 1.055±0.640 0.285-4.638, 2.725±1.601 0.285-4.638, 1.890±1.478
Phosphate (mg L-1) 0.017-0.445, 0.079±0.115 0.017-0.221, 0.100±0.061 0.017-0.445, 0.089±0.093
Nitrate (mg L-1) 0.074-0.392, 0.199±0.105 0.074-0.238, 0.171±0.065 0.074-0.392, 0.185±0.088
Silicate (mg L-1) 0.037-1.384, 0.482±0.456 0.037-0.664, 0.353±0.221 0.037-1.384, 0.417±0.364
Dissolved organic matter (mg L-1) 0.016-2.236, 0.413±0.797 0.025-0.452, 0.192±0.138 0.016-2.236, 0.302±0.582
Total dissolved solids (mg L-1) 0.018-0.296, 0.191±0.221 0.075-0.347, 0.183±0.081 0.018-0.347, 0.187±0.166
Figure 2. Monthly variations in species richness of
phytoplankton.
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Table 2. Variations (range, average and SD) of phytoplankton.
Nov. 2005-Oct. 2006 Nov. 2006-Oct. 2007 Study Period
Richness Phytoplankton > Zooplankton
Phytoplankton 55 species: 24-38 32±4 55 species: 20-41 34±7 55 species: 20-41 33±6
% similarity 51.7-84.4 50.0-95.8
Chlorophyta 40 species: 15-27 22±4 40 species: 11-30 23±6 40 species: 22-30 22±5
Abundance Phytoplankton > Zooplankton
Net Plankton n/L 254-1344 589±296 276-1077 550±234 254-1344 570±267
Phytoplankton n/L 132-1199 430±288 138-836 308±265 132-1199 369±253
% composition 41.3-89.2 68.8±12.7 39.1-77.6 53.4±11.3 39.1-89.3 61.1±14.3
Species diversity 1.922-3.086 2.534±0.314 1.693-3.399 2.680±0.546 1.693-3.399 2.607±0.451
Dominance 0.144-0.590 0.285±0.127 0.080-0.649 0.245±0.127 0.080-0.649 0.265±0.151
Evenness 0.545-0.919 0.756±0.107 0.472-0.921 0.764±0.130 0.472-0.921 0.760±0.119
Different groups Chlorophyta > Bacillariophyta > Cyanophyta > Cryptophyta > Euglenophyta > Dinophyta
Chlorophyta n/L 83-1087 306±265 57-739 171±184 57-1087 239±238
% composition 37.7-93.3 67.5±19.7 17.3-88.3 51.5±21.1 17.3-93.3 59.5±21.9
Bacillariophyta n/L 6-313 83±83 27-101 58±24 6-313 71±62
% composition 2.1-59.8 20.1±19.4 8.8-38.5 22.4±9.1 2.1-59.8 21.2±15.2
Cyanophyta n/L 0-54 6±15 2-192 42±68 0-192 24±52
% composition 0-23.8 2.5±6.4 0-73.5 13.7±22.9 0-73.5 8.1±17.7
Cryptophyta n/L 1-192 31±51 1-130 21±34 1-192 26±44
% composition 0.7-25.8 6.2±6.9 0.7-23.5 6.1±6.9 0.7-25.8 6.1±6.9
Euglenophyta n/L 0-21 2±6 3-96 16±25 0-96 9±19
% composition 0-9.2 1.0±2.5 0.3-33.9 7.0±9.0 0-33.9 4.0±7.8
Dinophyta n/L 0-6 1±2 0-2 0±1 0 - 6 1±1
% composition 0-2.6 0.5±0.9 0-0.9 0.2±0.3 0-2.6 0.4±0.7
Important genera (n/L)
Staurastrum spp. 11-663 108±175 27-367 92±97 11-663 100±142
Xanthidium spp. 1-290 12±88 0-215 35±56 0-290 73±83
Cosmarium spp. 14-106 43±31 3-88 20±25 3-106 32±30
Important species (n/L)
Staurastrum inflexum 2-186 45±49 1-100 26±32 1-192 36±42
S. nonanum 0-257 27±71 3-96 16±25 0-257 23±57
S. kurzianum 0-65 10±18 2-45 16 ±13 0-65 13±16
S. chaetoceras 0-7 2±2 2-80 20±24 0-80 11±20
Oscillatoria sp. 0-44 5±12 0-192 41±68 0-192 23±52
Frustulia sp. 1-76 21±21 9-47 23±11 1-76 22±17
Navicula sp. 1-100 23±30 4-30 15±8 1-100 19±23
Figure 3. Hierarchical cluster analysis of phytoplankton (First year).
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Sharma and Pachuau/ Phytoplankton diversity of Khawiva reservoir of Mizoram, northeast India
during the study period. The canonical
correspondence analysis (CCA) with fifteen abiotic
factors explained 57.6% of cumulative variance of
phytoplankton assemblages along axis 1 and 2 (Fig.
9).
Discussion
The sub-tropical Khawiva reservoir is characterized
by ‘soft, slightly acidic-circum neutral and well-
oxygenated waters with distinctly low specific
conductivity, low free CO2 throughout the study
period, low chloride content, and low concentration
of nutrients and other abiotic factors (Sharma and
Pachuau, 2013). Of these, pH and sulphate recorded
significant annual variations (vide ANOVA) while
specific conductivity and hardness recorded
significant monthly variations thus indicating
limited temporal variations during this study.
Fifty-five species of phytoplankton, belonging to
six groups, observed from Khawiva reservoir
Figure 4. Hierarchical cluster analysis of phytoplankton (Second year).
Figure 5. Monthly variations in abundance (n/L) of phytoplankton.
Figure 6. Monthly variations in abundance (n/L) of Chlorophyta.
Figure 7. Monthly variations in abundance (n/L) of
Bacillariophyta.
Figure 8. Monthly variations in species diversity of phytoplankton.
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exhibited fairly diverse nature of these primary
producers compared with the richness known from
sub-tropical reservoirs of Meghalaya (Sharma, 1995;
Sharma and Lyngdoh, 2003; Sharma and Lyngskor,
2003) and with the reports from Kashmir (Zutshi et
al., 1980), Bihar (Baruah et al., 1993; Sanjer and
Sharma, 1995) and Assam (Sharma, 2004). On the
other hand, it broadly compared with the results from
two floodplain lakes of NEI (Sharma, 2012, 2015).
The richness indicated no definite pattern of annual
variations but exhibited peaks during April (first
year) and September (second year) while lowest
richness is observed during October (first year) and
April (second year). The occurrence of all
phytoplankton species during both years asserted
homogeneity in their overall composition; this
generalization is also supported by high community
similarities during two years with values between
60-80% in majority of instances (88.0%) in the
matrix during first year while 58% instances
affirmed the stated range in the following year. Peak
phytoplankton similarity is observed concurrently
between January-February communities in both
years. The hierarchical cluster analysis showed
differences in clusters groupings during two years
with high associations during January-February and
most divergence in December during first year. High
affinities are observed between January-February,
August-September and December-July phytoplank-
ton while divergence is noted in April in the
following year.
The most diverse Chlorophyta largely contributed
to phytoplankton richness and thus mainly
influenced phytoplankton similarities; these features
Figure 9. CCA ordination biplot of phytoplankton and abiotic factors of Khawiva reservoir. Abbreviations: Abiotic: Alk (alkalinity), Co2 (free
carbon dioxide), Cl (Chloride), Cond (conductivity), DO (dissolved oxygen), DOM (dissolved oxygen matter), pH (hydrogen-ion concentration),
No3 (nitrate), PO4 (phosphate), Rain (rainfall), Sio2 (silicate), So4 (sulphate), TDS (Total dissolved solids), Trans (transparency) and Wt (water
temperature). Biotic: An.con (Anthrodesmus convergens), CR (Chlorophyta richness), PR (Phytoplankton richness), Bac (Bacillariophyta), Chl
(Chlorophyta), Cryp (Cryptophyta), Cry.sp (Cryptomonas sp.), (Cyan (Cyanophyta), Eugl (Euglenophyta), Phy (phytoplankton), Stuar
(Staurastrum), St.gl (S. gladiosum ), St.inf (S. inflexum ), St.ku. (S. kurzianum), St.non (S. nonanum), Cos. (Cosmarium), Na.sp (Navicula sp),
Fr.sp. (Frustulia sp), Xan (Xanthidium), Xan sp (Xanthidium sp), Osc.sp (Oscillatoria sp).
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Sharma and Pachuau/ Phytoplankton diversity of Khawiva reservoir of Mizoram, northeast India
agreed with the reports from NEI (Sharma, 1995,
2009, 2010, 2012, 2015; Sharma and Lyngdoh,
2003). The slightly acidic-circum neutral soft waters
with low ionic concentrations exhibited high desmid
richness (Payne, 1986) while Karikal (1995)
observed that soft waters with low nutrients favored
the growth of desmids. These remarks hold true for
de-mineralized soft waters of Khawiva reservoir
with Staurastrum (11 species) > Cosmarium (10
species) > Micrasterias (4 species). The importance
of desmid richness concurred with those from
reservoirs of Meghalaya indicating identical
characteristics (Sharma, 1995; Sharma and
Lyngdoh, 2003; Sharma and Lyngskor, 2003) and
also with the reports of Sharma (2009, 2010, 2012,
2015) from NEI.
Phytoplankton recorded wider density variations
with more difference during first year; it registered
insignificant monthly and annual differences (vide
ANOVA). It formed main component of net
plankton and significantly influenced their density (r
= 0.946) during the study with >50.0% of abundance
of the former throughout first year except in
December while their contribution is >50.0% in the
months of November, February and August through
October during second year. In general, quantitative
importance of phytoplankton in Khawiva reservoir
concurred with the results (Sharma, 1995; Das et al.,
1996, Sharma and Lyngdoh, 2003; Sharma and
Lyngskor, 2003) from certain reservoirs of
Meghalaya state of NEI and also with the reports
from the floodplains of Kashmir (Kaul and Pandit,
1982), Bihar (Rai and Dutta-Munshi, 1982; Sinha et
al., 1994; Sanjer and Sharma, 1995), Assam (Yadava
et al., 1987) and Kerala (Krishnan et al., 1999). On
the contrary, our results differed from phytoplankton
sub-dominance reported by (Sharma, 2004, 2009,
2010). The present study showed no definite annual
pattern of abundance while peak density is noticed in
May (summer) and November (autumn) during two
years, respectively; the former concurred with the
report of Sharma (2015) but differed from winter
peaks reported by Yadava et al. (1987), Wanganeo
and Wanganeo (1991), Sharma and Lyngdoh (2003)
and Sharma (2009).
The Chlorophyta, dominant component,
significantly influenced phytoplankton abundance
(r=0.935) and contributed to its peaks during two
years. The green algae registered insignificant
monthly and annual density differences during the
study; they exhibited annual peaks during March and
November during two years, respectively. The
average densities of this group are high than the
reports from sub-tropical environs of Meghalaya
(Sharma, 1995; Das et al., 1996; Sharma and
Lyngdoh, 2003; Sharma and Lyngskor, 2003) as well
as than the results of Yadava et al. (1987) and
Sharma (2004, 2009). The Chlorophyta is
characterized by high abundance of Staurastrum spp.
>Xanthidium spp. >Cosmarium spp.; the first two
genera in particular largely influenced density
variations of the former and contributed to
Chlorophyta peak abundance. In general,
quantitative significance of desmids agreed with the
reports of Sharma (1995, 2009, 2010) and Sharma
and Lyngdoh (2003). Rao and Govind (1964)
recorded desmid maxima in summer and winter
while Doddagauder (1989), Karikal (1995) and
Hulyal and Kaliwal (2009) reported their winter
peaks. Our results did not affirm any such
generalizations but indicated peak in autumn
(November) during the second year. Staurastrum
spp. and Cosmarium spp. registered concurrent
peaks in March but Xanthidium spp. showed peak
density in September during first year. Staurastrum
inflexum > S. nonanum > S. kurzianum >
S. chaetoceras are notable desmid species.
The Bacillariophyta comprised 21.2±15.2% of
phytoplankton abundance and recorded relatively
high abundance during first year. The diatoms
followed oscillating but different annual patterns and
peak densities during October and March during two
years, respectively not concurrent with phytoplank-
ton peaks. Our results recorded higher diatom
abundance than the results of Sharma (1995, 2009,
2010), Das et al. (1996), Sharma and Lyngdoh
(2003) and Sharma and Lyngskor (2003). Frustulia
sp. and Navicula sp. are important diatoms in this
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Int. J. Aquat. Biol. (2016) 4(6): 360-369
study. The Cyanophyta > Cryptophyta showed
importance during certain months. The former
recorded relatively high abundance during second
year and January through March in particular with
peak density in March attributed to Oscillatoria sp.
Cryptophyta occurred in low densities except for
peaks during April and February during two years,
respectively attributed to Cryptomonas sp.
Euglenophyta > Dinophyta recorded poor densities;
the former showed peak density in March during
second year.
The phytoplankton species diversity (1.693-
3.399; 2.607±0.451) recorded relatively wider
variations during second year. High values (>3.0) are
observed only during July during first year, and
during December and August during second year
while low diversity (below 2.0) is observed in
August (first year) and during January and March in
the following year. The diversity followed multi-
modal and bimodal patterns during two years
respectively, and ANOVA registered its
insignificant annual and monthly variations.
Khawiva reservoir indicated higher phytoplankton
diversity than the reservoirs of Meghalaya (Sharma,
1995; Sharma and Lyngdoh, 2003; Sharma and
Lyngskor, 2003). An equitable abundance of
majority of species resulted in general higher
phytoplankton evenness (0.760±0.119) during the
study except in August-September during first year
and in January-March during second year. It is
positively correlated with species diversity (r=0.843,
P<0.0001), thereby, indicating that periods of high
diversity correspond with high equitability. The
evenness followed oscillating annual variations. This
study indicated relatively wide variations in
dominance (0.080-0.649) indicating period of very
low dominance to certain months. On the other hand,
Xanthidium sp. mainly resulted in high dominance
in August during first year while its peak value in
January during second year is attributed to
abundance of Oscillatoria sp. and Xanthidium sp.
The dominance is inversely corrected with species
diversity (R=-0.839, P<0.0001) and evenness (r=-
0.868, P<0.0001). In general, high evenness and low
dominance affirmed the previous reports from sub-
tropical reservoirs of Meghalaya (Sharma, 1995;
Sharma and Lyngdoh, 2003; Sharma and Lyngskor,
2003) and also concurred with reports from various
ecosystems of NEI (Sharma, 1995, 2004, 2009,
2010, 2012, 2015).
This study lacked significant influence of any
individual abiotic parameter on phytoplankton
richness and abundance as well as on abundance of
Chlorophyta, Bacillariophyta and Cyanophyta. This
interesting feature is concurrent with the report of
Sharma (2009) but differed from importance of
various abiotic factors reported by Sharma and
Lyngskor (2003), Sharma and Lyngdoh (2003) and
Sharma (2010). Our results explained lower (57.6%)
cumulative variance of fifteen abiotic factors along
first two axes (vide the canonical correspondence
analysis) on phytoplankton assemblages; and
recorded importance of hardness, DOM, rainfall,
chloride and phosphate. Staurastrum, S. gladiosum,
S. kurzianum, S. nonanum, and Chrysophyta
abundance are influenced by hardness and dissolved
organic matter. S. inflexum density is influenced by
conductivity and nitrate; pH influenced Cosmarium
abundance; richness of phytoplankton and
Chlorophyta and phytoplankton abundance is
influenced by phosphate; high rainfall influence
abundance of Chlorophyta, Frustulia sp. and
Navicula sp. while high rainfall and chloride
influenced Bacillariophyta abundance. In general,
this study thus yielded little insight on overall
importance of abiotic parameters on variations
phytoplankton taxa.
Conclusions
The fairly rich phytoplankton of Khawiva reservoir
indicated homogeneity in its composition. High
richness of Chlorophyta and diverse nature of
desmids with Staurastrum > Cosmarium >
Micrasterias are interesting. Phytoplankton and its
dominant component Chlorophyta indicated wider
density variations; Bacillariophyta showed sub-
dominance; and Cryptophyta and Cyanophyta
exhibited limited importance; Staurastrum >
368
Sharma and Pachuau/ Phytoplankton diversity of Khawiva reservoir of Mizoram, northeast India
Xanthidium are quantitatively important genera
while S. inflexum > S. nonanum > S. kurzianum >
S. chaetoceras> Oscillatoria sp. > Frustulia sp. >
Navicula sp. are notable individual taxa. Richness
and abundance followed no definite pattern of
monthly variations. Phytoplankton indicated
moderate species diversity, high equitability and low
dominance. With lack of significant influence of
abiotic factors and CCA with 15 abiotic factors
explaining low cumulative phytoplankton variance,
this study yielded little insight on overall role of
abiotic parameters. The results thus suggested
importance of biotic factors associated with
microhabitat variations.
Acknowledgments
The authors are thankful to the Head, Department of
Zoology, North-Eastern Hill University, Shillong for
laboratory facilities. We thank S. Sharma, Shillong
for valuable suggestions on the draft of this paper.
The authors have no conflict of interests.
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