Spatio-temporal distribution of nekton community structure and diversity change in Hangzhou Bay, CHINA

Reporter: Dongrong Zhang

Date： 05. 08. 2020

CONTENTS

Subject background

Research object

Research results

Summary

01

02

03

04

Content

Subject background

01 PART

（1）Estuarine bay (complexity salinity, high turbidity and well-mixed ) is closely related to human life and

productive activities as a unique ecosystem (Barbier et al., 2011);

（2）Population dynamics and influence mechanism of nekton in the estuarine bay was seriously disturbed by

human activities;

（3）Estuarine bay waters serve as spawning, feeding and nursery grounds for fish larvae, juvenile and adult

nekton (Nyitrai et al., 2012).

Subject background

Hangzhou Bay

Typical area

Research object

02 PART

Research object

Estuarine nekton

Bait

Fo

od

org

an

ism

Rich sources of nutrients

Diverse habitats

High abundance and biomass of nekton

Complex spatial patterns of nekton

Research results

03 PART

Research results-1 Nekton assemblages and composition

Eco-group

Species number Mean Biomass Mean Abundance

Spring Summer Autumn Winter Spring Summer Autumn Winter Spring Summer Autumn Winter

Fish 20 15 21 16 108.52±67.68 41.04±27.00 90.99±104.07 136.61±215.36 8.10±11.51 10.61±6.22 13.83±8.35 4.03±3.29

Shrimp 8 11 7 5 8.38±6.68 39.93±26.77 35.48±24.06 2.64±2.27 17.30±14.19 55.12±36.01 80.58±67.27 5.03±3.29

Crab 3 5 5 4 14.55±9.38 2.33±2.77 9.54±10.56 3.93±3.75 2.21±1.85 0.42±0.36 1.55±1.43 0.18±0.11

Total 31 31 33 25 131.46±73.71 83.30±47.44 136.01±108.76 143.18±215.77 27.60±17.88 66.15±39.12 95.96±67.09 9.24±4.86

（1）57 taxa distributed among 23 families （2）Mean nekton biomass：Winter(fish)> Summer(shrimp) （3）Mean nekton abundance: Warm seasons(summer, autumn) >cold seasons (winter,spring) （4） Nekton of HZB were mainly composed of small near-shore species

Research results-2 Spatial distribution of nekton community

Spatial distribution of nekton biomass (kg/km2) in HZB

Spatial distribution of nekton abundance (×103ind./km2) in HZB

Research results-3 Dominant species of nekton

Dominant species (IRI>1000) :

Fish: Miichthys miiuy,

Collichthys lucidus ;

Shrimp: Exopalaemon

annandalei, Palaemon gravieri;

Crab : Portunus trituberculatus.

Research results-4 Nekton species diversity

Spring Summer Autumn Winter

0

1

2

3

4

a

a

a

Bio

mas

s div

ersi

ty i

nd

ex (

H')

One-way ANOVA test (a)

a

Spring Summer Autumn Winter

0.0

0.3

0.6

0.9

a

a

a

One-way ANOVA test

Bio

mas

s ev

enn

ess

ind

ex (

J')

(b)

a

Spring Summer Autumn Winter

0

1

2

3

aa

a

a

Non-parametric Kruskal-Wallis H test

Bio

mas

s ri

chn

ess

ind

ex (

d)

(c)

Spring Summer Autumn Winter

1

2

3 acbc

b

Abu

nd

ance

div

ersi

ty i

ndex

(H

')

(d)

a

Non-parametric Kruskal-Wallis H test

Spring Summer Autumn Winter

0.0

0.3

0.6

0.9 c

b

ab

Abu

nd

ance

ev

enn

ess

index

(J'

)

(e)Non-parametric Kruskal-Wallis H test

ac

Spring Summer Autumn Winter

0.0

0.4

0.8

1.2a

a

a

Abu

nd

ance

ric

hn

ess

index

(d

)

(f)One-way ANOVA test

a

0

50

100

150

200

250

-80

-60

-40

-20

0

20

40

60

Spring Summer Autumn Winter

Alt

ernat

e in

dex

(A

I)

Mig

rate

ind

ex (

MI)

Migrate index

Alternate index

Diversity index (H'), evenness index (J') and richness index (d): (i) Warm seasons>cold seasons (biomass); (ii) Opposite result (abundance in H' and J')

AI : 94 to 218 MI :-73 to 35 Large variation and unstable

Research results-5 Seasonal differences of nekton community structure

A01

A10

A02

A04

A07

A03

A08

A05

A06

A09

Sam

plin

g sites

50 60 70 80 90 100 Bray-Curtis similarity coefficient(%)

(a) Hierarchical cluster analysis of nekton biomass in spring

B08

B10

B09

B07

B04

B06

B05

B01

B02

B03

Sam

plin

g sites

40 60 80 100

Bray-Curtis similarity coefficient(%)

(b) Hierarchical cluster analysis of nekton biomass in summer

C10

C05

C07

C04

C06

C09

C08

C03

C01

C02

Sam

plin

g sites

50 60 70 80 90 100 Bray-Curtis similarity coefficient(%)

(c) Hierarchical cluster analysis of nekton biomass in autumn

D03

D01

D02

D10

D06

D08

D07

D09

D04

D05

Sam

plin

g sites

40 60 80 100 Bray-Curtis similarity coefficient(%)

(d) Hierarchical cluster analysis of nekton biomass in winter

(a) Spring : 3 groups(60%);

(b) Summer : 4 groups(65%);

(c) Autumn: 3 groups(65%);

(d) Winter: 3 groups(55%).

ANOSIM analysis results :

difference between seasons

reached the significance level

(Global R=0.616, P=0.0001)

Research results-6 Relationship between nekton and environmental variables

Redundancy analysis (RDA): (a) negative correlated with salinity； (b) DO and surface salinity positive

correlated; negative correlated with DIP;

(c) Depth showed a significant positive correlation;

(d) Chla and surface temperature were highly positive correlated.

Summary

04 PART

Summary

The community of nekton in Hangzhou Bay showed significant spatio-temporal variation

With the index of H', J', d, AI, and MI , the community was not stable comfortably

The community of nekton could be divided into 3~4 groups in the 55%~65% similarity levels in four seasons

Physico-chemical factors were highly correlated with the nekton biomass

Thank you for

your attention！