Analysing Long-Term Dynamics of Zooplankton Abundance in

Karakalpakstan Lakes

Gulistаn Ismаilоvnа Turemurаtоvа

, Hаmid Sаlаvаt ugli Nаgmetоv

Kаrаkаlpаk Stаte University, Nukus, Uzbekistаn

Irkutsk Stаte Аgrаriаn University, Irkutsk, Russiа

Keywords: Zооplаnktоn, Reservоir, Lаke, Regime, Biоmаss Аnd Diversity, Hаbitаt, Wаter Minerаlizаtiоn.

Abstract: The аrticle presents the lоng-term dynаmics оf zооplаnktоn аbundаnce аnd the results оf hydrоbiоlоgicаl

studies оf the fоur lаrgest lаkes оf Kаrаkаlpаkstаn.

1 INTRODUCTION

The lоng-term dynаmics оf zооplаnktоn were

аnаlyzed, аnd the results shоwed thаt the periоd оf

intense аgriculturаl wаter runоff pоllutiоn оf the

reservоir wаs mаrked by а greаter аmplitude оf

fluctuаtiоns in the cоmmunity's quаntitаtive

indicаtоrs аnd а significаntly higher number оf

indicаtоrs thаn the mоdern stаge. А significаnt

pоsitive cоrrelаtiоn between the аverаge аnnuаl level

оf the lаke аnd zооplаnktоn biоmаss wаs reveаled.

2 MАTERIАLS АND METHОDS

The selection of hydrobiological materials was

conducted from 2018 to 2022 in the waters of the

lakes of Karakalpakstan. Zooplankton sampling

occurred seasonally in spring, summer, and autumn.

Using a small Jedi net, zooplankton samples were

obtained by thoroughly fishing the water column.

Multiple net lengths were established from the bottom

to the surface at depths of less than 1.5–2 metres,

using mill gas No. 70. Samples were fixed in a

formalin solution containing 4%. The MBS-10

microscope was utilised in the lab to identify and

count the zooplankton samples that had been

gathered. Relevant groupings and individual genera

were determined using determinants. A portion of the

sample was used for the calculation of organisms

under a microscope, and the remaining portion was

https://оrcid.оrg/0000-0002-5088-1294

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examined to identify big and uncommon individuals.

The following groups of animals were counted and

measured separately: adult females, females with egg

sacs, males, copepodites at the 1-3 and 4-5 age stages,

nauplii, branchious females with eggs or juveniles in

a brood pouch, sterile females, males, and immature

individuals. Upon examining the complete sample,

the number of members of uncommon species and

individuals with morphological anomalies was

discovered.

Equations relating to linear weight dependency

were used to determine each zooplankter's specific

weight. The quantity and mass of all developmental

stages of each variety of crustacean were totalled.

Subsequently, the numbers and weight indices for all

species in the major categories of organisms and the

community at large were totalled. For one millilitre

(m3) of the water column, the mass and number of

zooplankton were determined. The number of

dominant species (in terms of abundance and

biomass), the ratio of crustacean and rotifer biomass,

the proportion of rotifers, branchious, and copepods

in the number and biomass of zooplankton, the

proportion of cyclops in the number and biomass of

copepods, the size of mature individuals, and the sex

ratio in paddle head populations were all used to

characterise the structure of zooplankton. thoroughly

fishing the water column. Multiple net lengths were

established from the bottom to the surface at depths

of less than 1.5–2 m, using mill gas No. 70. Samples

were fixed in a formalin solution containing 4%. The

MBS-10 microscope was utilized in the lab to identify

1144

Turemuratova, G. and Nagmetov, H.

Analysing Long-Term Dynamics of Zooplankton Abundance in Karakalpakstan Lakes.

DOI: 10.5220/0012955100003882

Paper published under CC license (CC BY-NC-ND 4.0)

In Proceedings of the 2nd Pamir Transboundary Conference for Sustainable Societies (PAMIR-2 2023), pages 1144-1147

ISBN: 978-989-758-723-8

3 RESULTS

In the period of 2018-2022, zooplankton studies were

carried out in the four largest lakes of Karateren,

Atakul, Saykul, and Akshakul in Karakalpakstan. A

total of 65 zooplankton species were identified in

these reservoirs (rotifers - 20, branchiopods - 25,

copepods - 20) (Table 1), with thicket forms

accounting for 35.0% and planktonic forms for

32.2%. Eurytopic species made up 5% of the total.

The remaining part consisted of benthic, benthic

forms, and inhabitants of shallow reservoirs. Among

the rare species, the thermophilic cyclops

Mesocyclops aequatoriales can be noted, with its

known northern border of the range being Uzbekistan

and Karakalpakstan. Of the representatives of the

order Calanoida, only one species has been found -

the thermophilic Sinodiaptomus arsi.

A significant proportion of thicket forms, especially

among rotifers, reflected the shallow status of the

reservoir. Background species included rotifers

Asplanchna priodontata, crustaceans Bosmina

longirostris, Daphnia galeata, as well as Euchlanis

phryne, Alona rectangula, Chydorus sphaericus, and

Cyclops vicinus. Quantitative indicators of

zooplankton were significantly lower, with rotifers

and branchiopods dominating. The composition of

the dominant species varied somewhat over the years

of research, with the relatively constant presence of

B. longirostris, Thermocyclops taihokuensis, and D.

galeata. The population of T. taihokuensis was

dominated by males, and Acanthocyclops trajani was

dominated by females.

Table 1: Quantitative indicators of zooplankton in the lakes

of Karakalpakstan during summer.

Lаkes Rоtiferа Clаdоcerа Cоpepоdа Tоtаl

Number, thоusаndcоpies/m3

Kаrаteren 10,9±6,4 9,6±2,6 7,4±0,8 27,8±5,6

Аtаkul 3,8±0,8 8,4±3,1 28,3±12,5 40,5±14,3

Sаykul 8,9±0,7 77,5±34,9 97,7±30,8 184,1±62,2

Аkshаkul 18,1±7,9 15,0±13,5 11,8±8,9 44,9±30,2

Biоmаss, g/m3

Kаrаteren 0,3±0,2 0,4±0,2 0,05±0,02 0,7±0,2

Аtаkul 0,06±0,02 0,5±0,2 0,3±0,1 0,8±0,2

Sаykul 0,2±0,02 0,6±0,2 0,8±0,3 1,6±0,5

Аkshаkul 0,3±0,05 0,7±0,6 0,04±0,03 1,0±0,7

Quantitative indicators of zooplankton were close

to those of the communities of the Karateren lakes

(Table 1). Copepods dominated in number, while

branchiopods dominated in biomass. The leading

species included the crustaceans Bosmina

longirostris, species of the genera Daphnia, and

Thermocyclops taihokuensis. Zooplankton were

represented by large individuals, with an average

size-mass index of 0.026± 0.004 mg. Paddlefoot

populations were dominated by females, and the

diversity of the community by biomass was at a

reduced level (1.35±0.16 bits/mg).

Widespread in the water areas of the lakes were

rotifers Polyarthra luminosa, Asplanchna priodontata,

A. sieboldi, crustaceans Moina brachiata,

Diaphanosoma lacustris, Daphnia galeata, Bosmina

longirostris, Thermocyclops taihokuensis,

Mesocyclops aequatorialis.

The diversity and abundance of zooplankton were

at a relatively high level, with a moderate amount of

biomass (Table 1). With a subdominant position of

branchiopods, paddleheads constituted the basis of

the indications. The dominant complex included the

usual lake species - B. longirostris, T. rylovi, A.

priodontata.

Zooplankton were developed to a moderate

degree. The basis of the number was formed by

rotifers, with branchiopods dominating in biomass.

A. priodontata and B. longirostris reached high

numbers. The structure of species dominance was

characterized by the location of the biomass curve

above the abundance curve, with their significant

divergence.

Keratella quadrata, Diaphanosoma orghidani, D.

dubium, Daphnia cucullata, Leptodora kindtii,

Thermocyclops taihokuensis, Cyclops vicinus,

Sinodiaptomus sarsi were most often found in Lake

Karateren.

Zooplankton was the most abundant in a number

of the studied lakes, dominated by paddleheads, with

Analysing Long-Term Dynamics of Zooplankton Abundance in Karakalpakstan Lakes

1145

a subdominant position in the biomass of

branchiopods. The dominant complex included

crustaceans D. cucullata, T. taihokuensis, T. crassus,

Acanthocyclops trajani, Leptodora kindtii.

Crustacean communities were at a relatively high

level. The dominance of crustaceans caused a high

value of the indicators of the size-mass structure - on

average 0.028 ± 0.001 mg.

Studies of zooplankton in the largest lakes of

Karakalpakstan have shown that the community of

shallow Lake Atakul was characterized by the

greatest diversity in the number of species, where a

significant proportion were thicket forms.

Zooplankton of lakes Karateren and Akshakul, with a

sharp increase in depth from the shore, consisted

mainly of pelagic species and were less diverse. The

number and biomass of zooplankton in lakes

Karateren, Akshakul, and Atakul were at a moderate

level. Zooplankton of Lakes Karateren and Akshakul

reached a relatively high abundance. The size

structure of the communities was characterized by the

predominance of large species in the summer, with an

average individual mass of 0.018± 0.028 mg. Due to

the pronounced dominance of several and a reduced

number of species that make up the community, the

diversity of zooplankton was low, especially when

calculating the index value by biomass. With the

exception of Akshakul, the predominant zooplankton

species structure of the 2019 lake was identified by

the placement of the biomass curves above the

abundance curves. In populations of cyclops from

Lake Akshakul, Thermocyclops taihokuensis T.

rylovi Acanthocyclops trajani was dominated by

males; in other cases, female dominance was noted.

The number of zooplankton in Lake Saykul is much

higher compared to the numbers of zooplankton in

other lakes.

Table 2: The number of zooplankton in lakes Karateren,

Atakul, Saykul, Akshakul by year.

Lаkes Yeаrs Number, thоusаnd cоpies/m3

Rоtifer

Clаdоce

rа

Cоpepо

dа

Tоtаl

Kаrаteren 2019 -

2022

2,9±1,

0,4±0,3 1,6±0,5 5,2±2,1

Аtаkul 2019 -

2022

0,8±0,

0,3±0,2 0,1±0,0

1,6±1,2

Sаykul 2019 -

2022

13,2±5

55,4±14

85,3±18

154,0±16

Аkshаkul 2019 -

2022

10,4±6

8,5±7,5 22,6±4,

47,5±3,4

Table 3: The biomass of zooplankton in lakes Karateren,

Atakul, Saykul, Akshakul by year.

Lаkes Yeаrs Biоmаss, g/m3

Rоtifer

Clаdоce

rа

Cоpepо

dа

Tоtаl

Kаrаteren 2019-

2022

<0,01 0,03±0,

0,02±0,

0,05±0,0

Аtаkul 2019-

2022

<0,01 <0,01 <0,01 <0,01

Sаykul 2019 -

2022

0,2±0,2 0,8±0,1 0,5±0,0

1,6±0,1

Аkshаkul 2019 -

2022

0,2±0,0

1,0±0,9 0,3±0,1 1,4±1,1

The basis of the number was made up of

paddleheads, with branched-moustached ones

dominating in biomass. Dominant groups of

zooplankton included: Diaphanosoma lacustris,

Bosmina longirostris, Thermocyclops scrassus,

Mesocyclops leuckarti, and Asplanchna sieboldi.

Among the species were Daphnia galeata, D.

longispina, Moina brachiata, Ceriodaphnia

quadrangula, Alona rectangula, Bosmina longirostris,

Eucyclops serrulatus, Cyclops vicinus, Mesocyclops

leuckarti, Thermocyclops crassus. Previously, the

lake was dominated by the cyclops Acanthocyclops

vernalis. Currently, it turns out that A. traiani lives in

Lake Saykul, and in Lake Karat A. salinus. Compared

with the 80s of the XX century, the number of

zooplankton in Lake Karateren was higher orders of

magnitude, with a smaller amount of biomass.

Currently, the dominant of the past years is

Diaphanosoma lacustris (previously identified as D.

brachyurum), retaining its leading position. At the

same time, the dominant complex included the

previously small Bosmina and Thermocyclops.

Under conditions of unstable water mineralization

(3.0-6.5 g/dm3), quantitative indicators of planktonic

invertebrates varied from 234.5 thousand ex/m3 and

4.1 g/m3 in 2019 to 38.3 thousand ex/m3 and 1.1

g/m3 in 2020. This year, paddleheads attached great

importance, in particular, the joint use of the species

T. crassus, T. vermifer, D. orghidani, D. cucullata, A.

sieboldi in 2019 on A. salinus, C. vicinus, K. squares.

The variety of zooplankton dramatically declined as

lake water mineralization increased. The average size

of individuals increased from 0.0140±0.0020 to

0.0230±0.005 mg. When using T. vermifer, females

dominated, T. crassus and C. Vicinus had large

females. The number of zooplankton reached a high

level, with a moderate intensity of biomass (Tables 2,

3). The paddle-legged, dominant complex included

rotifers B. calyciflorus, A. sieboldi, crustacean

PAMIR-2 2023 - The Second Pamir Transboundary Conference for Sustainable Societies- | PAMIR

1146

Thermocyclops taihokuensis, T. vermifer. Thus,

studies have shown that in the summer period, the

abundance of zooplankton in shallow and small lakes

of Karakalpakstan by area was most often at a low

level, which may be closely related both to their

strong overgrowth (up to 40-55%), as well as to high

water temperatures. Zooplankton were developed to a

greater extent in mineralized lakes Atakul, as well as

deeper and larger lakes Karateren, Saykul, Akshakul.

Thicket species of rotifers and crustaceans formed the

communities' backdrop. Some of the Thermocyclops

genus's two-component combination ozeravid

species, occasionally in conjunction with

diaphanosoma. When there is a shift in the

mineralization of the water, as was observed in the

Atakul lakes, the composition of the dominating

species completely changed. The analysis of

zooplankton diversity in general for all lakes showed

that with an increase in the total, average number of

species per sample and the number of dominant

species (P=0.50-0.60, P<0.05), the average individual

weight of zooplankton (g=-0.20) decreased

unreliably. In shallow overgrown lakes, adult

individuals of paddleheads were absent. In the larger

Karateren Lake, mature cyclops were recorded in

single specimens. Suicidal behavior of males was

observed in Thermocyclops crassus (Lake Akakul),

etc. chervets (Lake Saykul) when dominating females

or with moderately active absorption of irrigation in

the population of paddleheads from other reservoirs.

4 CОNCLUSIОNS

Thus, studies have shown that in the summer period,

the abundance of zooplankton in shallow and small

lakes of Karakalpakstan by area was most often at a

low level, which may be due to both their strong

overgrowth (up to 40-55%) and high-water

temperatures. A tendency to increase the number of

planktonic animals during the high-water phase of the

hydrological cycle, accompanied by irregular

changes in biomass, was found in the long-term

dynamics of the number of zooplankton in the lakes

of Karakalpakstan. There were changes in the

structure of the lake ecosystem, including the value of

an individual's average mass and taxonomic

relationships, as well as an increase in the amplitude

of fluctuations in quantitative indicators and

instability in the composition of dominant species

during this period of increased anthropogenic impact.

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