Seasonal variation in elemental composition of certain seaweeds...

Available online at www.worldscientificnews.com

( Received 02 May 2019; Accepted 20 May 2019; Date of Publication 21 May 2019 )

WSN 129 (2019) 147-160 EISSN 2392-2192

Seasonal variation in elemental composition of certain seaweeds from Mandapam and Kilakarai

coast, Gulf of Mannar biosphere reserve

Muthukumarasamy Thillaivasan, Kaliyamoorthy Kumar

and Kathiresan Silvakumar*

Division of Algal Biotechnology, Department of Botany, Annamalai University, Annamalainagar – 608 002, Tamil Nadu, India

*E-mail address: [email protected]

ABSTRACT

Vegetative plants of certain seaweeds were collected from the natural habitat of Kilakarai and

Mandapam coast were subjected to SEM-energy dispersive spectroscopic analysis and quantified the

following minerals viz., Na, Mg, Si, S, Cl, K, Ca, Mn, P, Fe, Zn and Cr during summer, pre-monsoon,

monsoon and post-monsoon seasons in 2007-2008. The order of preferential accumulation of elemental

composition during summer 2007 in Sargassum wightii: Ca > Mg > Na > S > Fe > Si > Cl > K > Mn;

Stoechospermum marginatum: Ca > Si > S > Mg > Mn > P > Na; Gracilaria corticata: Ca > Mg > Na > Si

> Cl > S > Mn > K > Fe > P; Gracilaria verrucosa: Ca > Cl > Si > Mg > Na > P > S > Mn > Fe > K and

Grateloupia filicinia: Ca > Cl > P > Si > Na > Cr > K. Seasonal distribution of elemental composition in

the seaweeds showed that most of the minerals were high during the summer followed post-monsoon

and monsoon seasons. This could perhaps be due to an ambient concentration of these minerals was

high during these seasons thereby facilitating their uptake by seaweeds.

Keywords: Seaweeds, SEM-EDS, Summer, Pre-monsoon, monsoon, Post monsoon, Gulf of Mannar,

Sargassum wightii, Stoechospermum marginatum, Gracilaria corticata, Gracilaria verrucosa,

Grateloupia filicinia

http://www.worldscientificnews.com/

World Scientific News 129 (2019) 147-160

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1. INTRODUCTION

Seaweed is one of the most important vegetable sources of calcium. They have rich source

of minerals, especially macro and micronutrients necessary for human nutrition, however the

nutritional properties of seaweeds are usually determined from their bio-chemical composition

viz., protein, carbohydrates, vitamins and amino acids etc. [1, 2]. Seaweeds are used as regular

components of diet and have been consume regularly by the coastal people. Significant amount

of seaweeds are harvested world wide for the production of phycocolloids. It is only source for

the production of phycocolloids. In the present study on attempt has been made on the seaweeds

namely Sargassum wightii (Greville Mscr.) J.G. Agardh, Stoechospermum marginatum (C.

Ag.) Kuetz., Gracilaria corticata var. Cylindrica J. Ag., Gracilaria verrucosa (Huds.) Papenfus

and Grateloupia filicinia (J.V. Lamouroux) C. Agardh. They grow abundantly along the coast of

Mandapam and Kilakarai. Seasonal changes in elemental composition for a period of one year

between January 2018 to December 2018. Physico-chemical characteristics of seawater

samples collected in different seasons were also recorded. Further, the seaweeds were subjected

to EDS and the results of these studies are presented in this paper.

2. MATERIALS AND METHODS

Samples of Sargassum wightii (Greville Mscr.) J.G. Agardh, Stoechospermum

marginatum (C. Ag.) Kuetz., Gracilaria corticata var. Cylindrica J. Ag., Gracilaria verrucosa

(Huds.) Paperfus and Grateloupia filicinia (J.V. Lamouroux) C. Agardh (Plate 1) were

collected from the natural habitat in the intertidal area of Gulf of Mannar Biosphere (Fig. 1).

The collection was made during the morning low tide. They were transported to the laboratory

in plastic packets, brushed off the epiphytes and washed several times in filtered seawater

followed by distilled water. These five alga species of 2-3 mm were fixed in 3% glutaradehyde

for scanning electron microscopic studies. Then they were dehydrated through a graded series

of acetone with 12-15 m interval at 4 C up to 70%. They were further dehydrated in 90% and

100‰ of acetone and kept at room temperature for 2-3 h. Finally the dehydrated samples treated

with critical point drier (CPD). Then they were mounted on a stub and the specimens were

coated [3]. They were examined with JOEL JSM-56010 LV with INSA-EDS and

photomicrographs were taken selectively from computer screen at central sophisticated

Instrumentation Laboratory, Department of Physics, Annamalai University, Annamalainagar,

Tamil Nadu, India. Physico-chemical parameters of seawaters were collected for the estimation

of temperature, salinity, pH and DO using water and soil analysis kit model 1160-E.

3. RESULTS AND DISCUSSION

Physico-chemical parameter such as atmospheric temperature, surface water temperature,

salinity, pH, DO are presented in Tables 1 to 4.

The seasonal variation in surface water temperature and air temperature invariably

showed high values during pre-monsoon and low in post monsoon. The air temperature varied

from 33.6 to 36.0 C. The surface water temperature varied from 33.1 to 34 C. The salinity of

seawater shows high during summer and low in monsoon period.


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Table 1. Correlation matrix between different physico-chemical parameters of seawater

samples during post monsoon (January-March, 2018).

Air

temperature

(C)

Surface water

temperature

(C)

Salinity

(‰) pH

Dissolved

oxygen (ppm)

Air

temperature

(C)

1.000**

Surface water

temperature

(C)

1.000** 1.000**

Salinity (‰) 0.800* -0.500* 1.000**

pH 1.000** 1.000** -0.500* 1.000**

Dissolved

oxygen (ppm) 0.500* 0.500* -1.000** 0.500* 1.000**

* Significant at 5% level

**Significant at 1% level


samples during summer (April-June, 2018).

Air

temperature

(C)

Surface water

temperature

(C)

Salinity

(‰) pH

Dissolved

oxygen (ppm)

Air

temperature

(C)

1.000**

Surface water

temperature

(C)

-1.000** 1.000**

Salinity (‰) 0.500* 0.500* 1.000**

pH 1.000** -1.000** -0.500* 1.000**

Dissolved

oxygen (ppm) -1.000** -1.000** -0.500* 1.000** 1.000**




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samples during pre monsoon (July-September, 2018).

Air

temperature

(C)

Surface water

temperature

(C)

Salinity

(‰) pH

Dissolved

oxygen (ppm)

Air

temperature

(C)

1.000**

Surface water

temperature

(C)

0.970* 1.000**

Salinity (‰) -0.866* 1.000** 1.000**

pH 1.000** 0.866* 0.866* 1.000**

Dissolved

oxygen (ppm) 1.000** 0.866* 0.866* 1.000** 1.000**




samples during monsoon (October-December, 2018).

Air

temperature

(C)

Surface water

temperature

(C)

Salinity

(‰) pH

Dissolved

oxygen (ppm)

Air

temperature

(C)

1.000**

Surface water

temperature

(C)

0.866* 1.000**

Salinity (‰) -0.600** -0.500* 1.000**

pH 1.000** 0.866* 0.000 1.000**

Dissolved

oxygen (ppm) -0.600* 0.866* 0.000 1.000** 1.000**




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The salinity varied from 33 to 34.2‰. The pH of seawater shows high during summer

and pre monsoon seasons. The pH seawater shows high during summer and pre monsoon

seasons. The pH varied from 7.1 to 7.5. The DO shows high value during post monsoon season.

The DO varied from 4.1 to 4.7 ppm. Analysis of the different elemental composition of the 5

seaweeds using SEM-EDS was carried during the different climatic conditions of the period

January 2018 post monsoon to December 2018 Monsoon. The experiment carried out for four

seasons i.e. summer, pre monsoon, post monsoon and monsoon. The result of the study showed

a distinct amount of each element.

Table 5. Elemental composition of seaweeds using SEM-EDS during post monsoon

(January-March, 2018).

Seaweeds

Minerals (wt %)

Na Mg Si S Cl K Ca Mn P Fe Zn Cr Total

S.

wig

hti

i

11

.14

0

.11

27

.96

0

.15

4.6

3

0

.09

4.1

0

0

.09

3.6

0

0

.07

2.4

4

0

.06

41

.38

0

.20

1.5

0

0

.07

-

3.2

2

0

.08

- -

99

.97

0

.18

S.

ma

rgin

atu

m

5.4

0

0

.14

12

.71

0

.10

19

.20

0

.08

11

.43

0

.13

- -

41

.70

0

.20

6.8

2

0

.08

2.7

3

0

.07

- - -

99

.99

0

.23

G.

cort

ica

ta

13

.36

0

.52

17

.25

0

.25

11

.66

0

.21

6.6

5

0

.14

10

.33

0

.10

1.7

1

0

.13

34

.01

0

.22

2.2

3

0

.07

1.1

6

0

.04

1.6

0

0

.17

- -

99

.96

0

.24

G.

verr

uco

sa

8.4

7

0

.11

15

.27

0

.19

14

.84

0

.16

5.4

3

0

.07

17

.42

0

.19

1.4

8

0

.06

25

.13

0

.20

3.8

1

0

.08

5.6

4

0

.12

2.4

7

0

.75

- -

99

.96

0

.12

G.

fili

cin

ia

7.9

4

0

.09

4.6

5

0

.07

11

.0

0

.09

-

20

.93

0

.14

3.6

7

0

.08

32

.85

0

.22

-

13

.05

0

.10

- -

5.8

8

0

.07

99

.97

0

.20

Values are expressed as the mean SD; n = 3


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Table 6. Elemental composition of seaweeds using SEM-EDS during summer

(April-June, 2018).

Seaweeds

Minerals (wt %)


S.

wig

hti

i

9.0

6

0

.12

23

.13

0

.18

2.9

0

0

.09

3.7

1

0

.08

3.0

4

0

.08

-

33

.36

0

.19

-

3.9

2

0

.08

4.2

5

0

.11

4.8

3

0

.08

11

.77

0

.11

99

.97

0

.18

S.

ma

rgin

atu

m

2.2

0

0

.07

10

.02

0

.35

18

.79

0

.08

8.8

6

0

.11

3.0

5

0

.07

1.5

4

0

.06

31

.3

0

.29

4.8

1

0

.08

2.9

4

0

.07

1.8

6

0

.06

10

.90

0

.13

3.8

5

0

.07

99

.99

0

.23

G.

cort

ica

ta

10

.64

0

.11

13

.14

0

.15

10

.95

0

.18

8.9

3

0

.08

9.7

3

0

.09

1.7

3

0

.06

29

.10

0

.22

1.7

5

0

.07

1.9

3

0

.07

1.6

2

0

.06

4.0

6

0

.05

6.3

8

0

.06

99

.96

0

.24

G.

verr

uco

sa

6.2

4

0

.13

11

.40

0

.11

12

.42

0

.13

3.1

0

0

.04

16

.91

0

.14

1.9

0

0

.06

21

.89

0

.19

3.5

4

0

.04

4.9

3

0

.08

6.7

0

0

.14

5.0

7

0

.10

5.8

6

0

.11

99

.96

0

.12

G.

fili

cin

ia

5.9

2

0

.12

4.4

4

0

.15

9.7

1

0

.08

3.5

7

0

.05

19

.83

0

.19

-

27

.33

0

.22

6.1

0

0

.10

9.7

1

0

.08

5.6

0

0

.10

7.7

5

0

.08

-

99

.97

0

.20


The order of elements in different seaweeds as follows S. wightii, Ca > Mg > Cr > Na >

Zn > P > S > Fe > Cl > Si > K > Mn; S. marginatum, Ca > Si > Zn > Mg > S > Cr > Mn > Cl > P >

Na > Fe > K; G. corticata, Ca > Mg > Si > Na > Cl > S > Cr > Zn > Mn > Fe > K; G. verrucosa,

Ca > Cl > Mg > P > Cr > Zn > Na > Fe > P > Mn > S > K and G. filicinia, Ca > Cl > P > Si > Fe >

Cr > Zn > Na > Mg > K (Tables 5 to 8).

Seaweeds collected during post-monsoon season showed maximum contribution of

calcium. They were ranging between 23.92 0.30 to 39.54 0.37 total weight. Minimum values

were varied among species during monsoon period. In G. corticata least values were obtained


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for phosphorus (1.39 0.06), S. wightii, Mn (1.34 0.06), S. marginatum, Cr (1.61 0.07), G.

filicinia, S (2.08 0.10) and G. verrucosa, K (1.82 0.07) (Tables 5 to 8).

Table 7. Elemental composition of seaweeds using SEM-EDS during pre monsoon

(July-September, 2018).

Seaweeds

Minerals (wt %)


S.

wig

hti

i

8.9

5

0

.11

22

.60

0

.17

2.5

2

0

.04

3.6

7

0

.08

2.8

2

0

.03

1.9

1

0

.06

33

.17

0.2

3

1.8

1

0

.06

3.9

9

0

.09

3.8

6

0

.08

4.5

2

0

.09

10

.13

0

.14

99

.95

0

.15

S.

ma

rgin

atu

m

2.1

4

0

.10

9.5

3

0

.08

17

.98

0

.13

8.6

6

0

.12

3.8

2

0

.07

1.3

9

0

.08

29

.26

0

.31

4.3

4

0

.08

2.6

4

0

.09

1.4

4

0

.06

12

.46

0

.11

6.3

1

0

.04

99

.97

0

.23

G.

cort

ica

ta

10

.47

0

.11

13

.08

0

.11

10

.90

0

.08

8.8

0

0

.09

9.0

6

0

.10

1.4

9

0

.05

28

.92

0

.20

2.5

3

0

.04

1.1

0

0

.04

1.6

0

0

.06

3.9

6

0

.07

8.0

6

0

.07

99

.97

0

.27

G.

verr

uco

sa

6.1

1

0

.13

11

.32

0

.13

10

.81

0

.09

2.9

3

0

.08

16

.41

0

.19

2.0

9

0

.05

21

.16

0

.17

4.5

0

0

.08

4.9

3

0

.07

5.1

5

0

.06

6.6

1

0

.08

7.9

4

0

.12

99

.96

0

.33

G.

fili

cin

ia

5.1

0

0

.11

3.8

7

0

.11

9.1

4

0

.12

2.6

2

0

.06

19

.36

0

.17

2.8

0

0

.09

25

.77

0

.23

1.3

0

0

.07

9.8

7

0

.12

8.9

7

0

.07

5.4

5

0

.11

5.7

1

0

.08

99

.96

0

.19


Two stations selected in the present study are located along the Tamil Nadu coast. The

atmospheric temperature fluctuations are suggested to be Ocean’s thermal inertia which

changes the lay between absorption and release of solar energy to the atmosphere [4].

Atmospheric temperature at Kilakarai and Mandapam station had positive correlation with


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surface water temperature, pH and salinity but negatively correlated with dissolved oxygen

(Tables 1 to 4).

Table 8. Elemental composition of seaweeds using SEM-EDS during monsoon

(October-December, 2018).

Seaweeds

Minerals (wt %)


S.

wig

hti

i

10

.70

0

.14

26

.40

0

.32

3.1

5

0

.06

3.7

7

0

.11

3.0

4

0

.08

2.1

5

0

.06

38

.67

0

.06

1.3

4

0

.06

-

3.0

8

0

.11

4.7

3

0

.08

2.9

3

0

.09

99

.96

0

.24

S.

ma

rgin

atu

m

3.7

3

0

.08

11

.41

0

.14

18

.68

0

.16

11

.81

0

.13

3.2

0

0

.10

-

39

.54

0

.37

5.1

8

0

.12

2.5

9

0

.08

-

2.8

4

0

.06

1.6

1

0

.07

99

.96

0

.31

G.

cort

ica

ta

12

.36

0

.16

16

.70

0

.12

10

.76

0

.10

5.9

3

0

.09

9.8

6

0

.13

1.9

2

0

.07

30

.67

0

.29

1.9

6

0

.06

1.3

9

0

.06

1.8

5

0

.06

4.6

1

0

.07

1.9

5

0

.05

99

.96

0

.18

G.

verr

uco

sa

7.1

0

0

.08

13

.64

0

.05

13

.65

0

.11

4.7

5

0

.07

16

.03

0

.14

1.8

2

0

.07

23

.92

0

.30

3.1

8

0

.04

6.0

9

0

.14

1.9

4

0

.08

2.7

3

0

.07

5.1

0

0

.08

99

.95

0

.17

G.

fili

cin

ia

6.8

4

0

.12

4.2

7

0

.06

9.8

3

0

.13

2.0

8

0

.10

19

.74

0

.29

3.1

0

0

.08

29

.96

0

.30

-

11

.56

0

.19

-

6.6

9

0

.07

5.9

0

0

.21

99

.97

0

.29


The maximum surface water temperature at Mandapam and Kilakarai (34 C) was

recorded during the pre-monsoon season in August, 2007 and the minimum temperature 33.1 C

was observed at the post monsoon season in February, 2008. Difference in surface water

temperature pattern is quite evident as surface water temperature depends on the solar energy


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input and it seems to be influenced by several environmental conditions and factors such as

inflow of freshwater, solar radiation, warming, evaporation, cooling, wind pattern and mix up

with flow from adjoining neurotic waters. Similar seasonal variations were reported from east

coast of India (Figure 1) [5].

Fig. 1. Map showing collection spot

The monthly surface water temperature fluctuation were different for the west coast of

India as compared to that of the east coast of India [6-8] However, there is a significant and

positive correlation between atmospheric temperature and surface water temperature in the east

and west coasts of India [9].

pH remained alkaline throughout the study period at Kilakarai and Mandapam with

maximum values during the summer season. These observations supported the earlier report from

Rushikulya estuary [10]. The uptake of CO2 by the photosynthesizing organism especially

phytoplankton from the estuarine water could have increased the pH levels during the summer

season. In general, pH was low during the monsoon season and this was associated with lesser

salinity regimes.

Distribution of minerals such as Ca, Mg, Na and Cl was high in the selected species of

seaweeds in the study area. Significantly higher concentration of elements such as Ca, Mg and

K were encountered in the various type of seaweeds during summer and post-monsoon periods

which reflect the capacity of these seaweed to accumulate more amount of elements during

these seasons. The concentration of Na was also found to be high during summer and pre-

monsoon seasons which coinciding with peak period of growth [11]. Moreover, differences in


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element concentration of seaweeds in the study area, during the various seasons might be related

not only to different mineral level in water but also to different ecological conditions such as tidal

range, temperature and salinity [12]. Generally, bioaccumulation of the elements in the seaweeds

depends upon the pH, salinity, dissolved O2 and the osmotic potential of the system [13]. Marine

algae exhibit high content of ash [14] mainly due to the presence of Na, K, Ca and Mg cations

(Fe and S will be of minor importance).

Higher accumulation of Mg and Fe was mostly observed in seaweeds during summer

season, it may be explained here that the accumulation elements in situ was more due to the

reduction in osmoregulation activities usually affected by the increase in salinity. Though the

silicon and Cl concentrations in ambient water exceeded those of other elements, the

accumulation in seaweeds was very low and the most preferred being Ca, Mg and Na. This

probably due to the fact that Ca and Mg are the predominant occupants of the uptake binding sites

of the seaweeds which would inhibit accumulation of silicon and Cl by their competition for

binding sites [15]. The enhanced bioaccumulation of most of the elements in seaweeds during

summer and pre-monsoon seasons could perhaps be due to the following reasons: (i) ambient

concentration of these elements was high during these seasons thereby facilitating their uptake by

the seaweeds, (ii) seasonal variation in mineral content in seaweed may be related to growth

rates and metabolic activity. [12, 16, 17]. The quick uptake of elements during summer and

slow uptake during winter and (iii) ecological implications are important in metal uptake by

seaweeds [18]. This was evident as dissolved oxygen and pH of the water samples during

various seasons in the present study showed the variations of correlation between various

elements in the seaweeds. Our results showed maximum values of oxygen during summer and

minimum during the winter. The higher values of oxygen during summer (April-June) are

associated with the rise in seaweeds population [20]. These observations are in agreement with

those of who reported that the seasonal variations of the mineral concentration in aquatic biota

may be due to seasonal fluctuation in tissue mass and changes in physico-chemical

characteristics of the surrounding water [20-28].

4. CONCLUSION

Seaweeds possesses most of the nutrients. This growth and distribution were varied for

the altering seasonal influence in Kilkarai and Mandapam costal region of Gulf of Mannar

biosphere reserve.

Acknowledgements

Authors are thankful to Centralized Instrumentation Service Laboratories (CISL) generously providing SEM-EDS

studies and also would like to sincerely thank to Professor and Head, Department of Botany, Annamalai University

to provide Phytochemical Laboratory studies

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Plate 1. Morphology of brown and red seaweeds


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Plate 2. Scanning electron microscopic observation

Seasonal variation in elemental composition of certain seaweeds...

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