SURVEY OF MANGROVES OF COCHIN

u Introduction

Brief History of Cochin

Geography of Cochin

u Materials and Methods

Sampling Stations Selected

Procedure of Survey

u Observation

u Discussion

SCJRVEY OF MANGROVES OF COCHlN

INTRODUCTION

Kerala lies towards the South - West coast of India, a segment barred by

the Westerrl Ghats It extends between the latitudes 8" 18' and 12' 48' north and

longitudes 71" 53' and 77" 24' east with an area of about 38863 sq. kms (Ganeadharan,

1999). Length of Kerala coast is approximately 580 km with a northern limit at

Manchesuaram and Southern limit at Pozhiyar. Temperature varies between 25' to 35' C

during summer. and 20" to 30" C during winter. The area under wetland in Kerala

estimated using satellite remote sensiny data is 127930.07 ha, out of which inland

uetlands cover 31199 57 ha (Anonymous, 2000~). hlastaller (1996) reported that some

70,000 ha of rliangroves of Kerala were cleared at the turn of this centuary. hlangrove

forest area of'the Eranakulam district is estimated to be 250 kmz (Anonymous; 1999a)

Biological diversity is now increasingly recoynised as a vital parameter to

assess global ar~d local envirorimental changes and sustainability of developmental

activities (Lovejoy. 1995). M)el-s (1990) identified areas of exceptional species richness

and endemicity on the global scale and referred them as 'hot spots' of diversity. A broad

scale classification of different types of landscapes i:r a use&] step towards the

biodiversir) assessnient (Nagendra and Gadgil, 1998). A survey is necessary to

understarid thc diversity of species in a vegetation. Diff'erent methods such as direct

countiny. quadrat ar~d transect can be employed to study the vegetation of an area. Line

transect methods were employed by Kunte el crl (1999) for the biodiversity study in

Western (illalr

Mangrove vegetation in Cochin area are seen along with the back water

channels and along the banks of estuarine water bodies, in the form of patches or

narrow continuous belt. Very little is known about the diversity and distribution patterns

of mangroves of Cochin area. An intensive survey programme was conducted in the

Cochin area for inventorying and monitoring the species diversity of mangroves of

Cochin Data were collected by field observations, ac,tual measurements, personnel

interviews, photography and through chemical analysis of plant, water and soil,

General information regarding the Cochirl area are given below (after

Naseer, 1996)

District - Ernakulam

Area - 87.341 sq. km.

Population - 11,39,543 (1996 census)

Latitudes and Longitudes - 9' 58' North, 76' 17" East.

Altitude

Rains

- Sea level

- South West monsoon (heavy rainfall) : June -

August, North East monsoon (light rainfall):

September - November

Annual rainfall - 310cm.

Climate - Moderate through the year

Temperature

Minimum : 2 2 . 5 ' ~

- Summer < Maximum : 35'C

Minimum : 20' C

- Winter < Maximum : 3 2 ' ~

A Brief History of Cochin

Coch~n came into existence as an important port in 1341 A D when the

flooded Periyar river destroyed what up to then had been a world renowned port,

Kodungallur. just north of Cochin. It is believed that the formation of a cluster of islets at

the end of the river Periyar, whic,h is emptying into Cochin backwaters, is the result of the

deposit of silt due to the catastrophic deluge which occurred in 1341 AD (Gopalan,

1992). The massive uncontrolled flood eventually lead to the accumulation of large

amount of silt giving birth to the various islets in the Cochin backwater region of

Vembanadu lake. The Vembanadu lake that we see now was also shaped at that time. The

new Cochin port found its echo in the neighbouring villages of Vytilla, Edapally,

Mamangalam, Palarivattom, Ernakulam, Vypeen, Vallarpadom, Thopumpady,

Kannamali. Edakochi and Palluruthy, which began their integration into Cochin from

then. The ideal location of its natural harbour helped Cochin emerge as a bustling centre

of commercial activity. After independence, the corporation of Cochin was formed in

1967 and the city took its present shape.

Geography of ('ochin

('ochin has one of the best natural harbour!; in the world. The Cochin back

water extends along the western side of the Cochin area which in turn is the northern part

of the Vembanad lake. The Ve~nbanad lake is the biggest and most extensive one in

Kerala I t extends between 9":s' and 10' 10' N and longitudes 76' 13' and 76' 31' E. The

lake covers an area of 7503 8 ha and Cochin backwater covers 2257.89 ha. Near the

nor their^ end of this lake is situated the port of Cochin where the lake is permanently

connected to the sea by a narrow channel. During flood tides the sea water (Lakshadweep

sea) enters the Cochin estuary via Cochin barmouth (12 m depth) and the flow reverses

during the ebb tides. In Cochin backwaters there exists many thickly populated islands.

Vembanadu lake and connected Cochin backwaters are considered to be

an example for mangrove estuary. The rich particulate organic matter derived primarily

from the decomposed mangrove foliage is nutritionally very rich and hence forms an

important source of food for juvenile fishes and shrimps, Formerly, a highly productive

lagoon system bordered by lush mangrove forsets were present in the Cochin area, but

now the bay 1s secluded. On land Cochin area is midway between Alapuzha and Trichur

districts on south and north sides respectively. The main occupation of the people apart

from trading is fishing; but it has prosperous agncultural hinter- land which benefits from

the rich alluv~al soil of the region.

MATERIALS AND METHODS

The Sampling Stations Selected for the Present Study

After conducting a preliminary survey in and around Cochin, eleven

mangrove growing sites were identified (Figure 5) where coastal fishery and traditional

aquaculture are in vogue. All these sites had a mangrove distributional area of two

hectare and above The sampling sites were widely separated, had dissimilar sediment

character~st~cs, and u'ere influenced highly by monsoon These stations were selected so

as to have a M ~ d e representation of the prevailing complex environmental conditions.

Station No. I Katlnamali

The first station selected was at Kannamali, a typical mangrove area near

Chellanuni This station is directly under the influence of 1,akshdweep sea. Mangroves of

this area protect the coastline by acting as wave break. They stabilise coastline, promote

coastal accretion and serve as natural barriers against torrential storms. In this way they

preserve the coastline and prevent shoreline erosion.

Station No. 2 Kumbalangi

The station 2 is Kumbalangi island, a typical coastal area, lying parallel to

the Perumbadapu, coastal village. Kumbalangi is thickly populated island, where due to

encroachment to the estuarine domain not only the mangrove vegetation and its habitat is

reduced but also the ecological niche of its coastal belt is changed.

Station No. 3 Kumbalam

Station three is Kumbalam near Thripuriithura which is more or less

completely surrounded by Cochin backwaters. This is a thickly populated area and

mangrove ecosystem of this region is subject to population pressure. Extensive land

filling has affected the mangrove vegetation. This station is extended upto Panangad.

Station No. 4 Nettoor

Fourth station is Nettoor near Thirunettoor Railway station. A number of

creeks and canals are found to traverse the area fringed with mangrove plants.

Eranakulani - Alapuzha railway line and National highway 47 are also passing the

through th~s area. Extensive land filling has been made in this station through very thick

mangrove forests

Station No. 5 Rlangnlavanam

Mangalavanam mangrove forest is located i n the heart of the Cochin city

on Dr Salini Ali Road near the Hish Court of Kerala This is declared as a bird sanctuary

by the Governnient of Kerala This area is considered to be hnctioning as the lungs of

the city Large scale storage tanks for petroleum products of Indian Oil Corporation is

situated verv close to this station

Station No. 6 Panambukad

Station six selected for this investigation is a small island in Vypeen block

Panambukad. This island is surrounded by the estuarine waters of Cochin backwater. The

island has an area of 9.27 sq, km. Except for the human dwellings, the island is occupied

by traditional prawn cum fish farms fringed by mangroves. This station is coming under

the purview of Goshree project proposal of district administration. The project involves

the land filling of several hectares of estuarine habitat for the construction of a network of

bridges

Station No. 7 Puthuvypu

This station is situated half kilometer away from lighthouse of Vypeen

island An extend of 101 ha of land supporting mangroves in patches exist at Puthuvypu

There are several tidal channels. sand pits and creeks which support good mangrove

vegetatiotr

Statiou No. 8 Pallipuram

Station number 8 is a Pallipuram which is situated towards the northern

end of Vypeen island near Munambam. This area is lying parallel to the Lakshadweep

sea with a direct tidal influence Lying on two sides of the Pallipuram are backwater.

There are many channels and creeks fringed with luxuriant mangrove vegetation. Isolated

species could also be seen in detached water bodies and reclaimed lands along the coastal

tract.

Station No. 9 Karumallor

Station number 9 is Karumalloor situated near Aluva. This area is directly

connected by backwater system, which is highly influenced by tidal incursion. Most of

the mangrove area of this site has been converted into coconut plantation, paddy fields

and used for human settlement

Station No. 10 Pattanam

The area ofthis station is more or less completely land filled. A long canal

is traversing through this station. Patches of mangrove species are growing along the

banks ofthis canal

Station No. I I Moothakunnam

Station number I I is at Moothakunnam, which is also a land filled area

surrounded b!; creeks on one side and backwater on the other side. Patches of mangroves

are yrowing here and there. Hiyhly restricted occurrence of the mangroves of this area is

directly attributed to the gross interference of man's activities.

Procedure of Survey

In the present investigation the distribution and density of the mangrove

vegetation and the varying hydrological conditions of the estuary were studied for 3 years

from Januaq 1996 to January 1999. In the first phase of the study a detailed survey of

mangrove tlora was conducted during the year 1996. Documents regarding the number of

species, total number of specles, area occupied, nature of spread, morphological

peculiarities, special adaptations and other details connected to the mangrove and

associated tlora were collected from each station during the survey. Further changes in

the community area of mangrove spread and depletion were noted time to time and

updated till January IO99.

111 order to study the distribution pattern of mangrove and associated

species, quadrat analysis were done in all the stations (Michael, 1984). After conducting a

preliminary survey size of the quadrat was determined as 10 x 10 m. the number and

position of all species at each station were accurately marked on a chart. To confirm the

precision of the data quadrats were taken in each station at different locations.

Phytosociological analysis such as density, abundance and diversity were calculated from

the quadrat data (Trivedy et a]., 1'187; Krebs, 1999). Diversity Index was calculated using

the following Shannon-Wiener fUriction

S HI = c (pi) log 2 pi)

1 = 1

Where H' Information content of sample (bitsfindividual)

or

Diversity Index of the species

s - Number of species

pi = Proportion of total sample belonging to i th species.

Theoretical maximum diversity was calculat.ed using the equation

L,og10 s H ,,, = log 2 S =

-

120g,o 2

S = Number of species

Ratio of observed diversity to the theoretical maximum diversity was also

computed

where E = equitability (range 0 - 1:)

D~stribution and succession pattern of mangrove and associated flora were

assessed from the data collected

Flowering twigs of mangroves and associated species were collected form

all the eleven stations. Analysis of habit, vegetative characters, morphological features

and adaptations were done. The species of mangroves and associated flora were

identified based on its vegetative and floral morphologica.l characteristics with reference

to the published flora (Gamble, 1967; Dewit, 1967; Matthew, 1983) and by comparing

with the herbarium specimens The distribution map of the mangroves in all the selected

stations of [ochin area were prepared.

OBSERVATION

In Cochin area ten true mangrove species belonging to seven genera were

enumerated through the survey (Table 1). Table I1 a, Table I1 b and Table 111 show the

mangrove spread area, total number of species, density and diversity at each station. In

the Cochin area Acattthrrs i1icrJol;zr.s L. was found in maximum number followed by

A~licettt~ia offiotra1i.c L. Rhizophora carzdelaria DC. and Kattdelia candal L. were found

in minimum Maximum diversitv was noticed at Kumbalam station. Different mangrove

species of Cochin area are known in different local names based on their colour and

special features Accordingly red mangrove (Rhizophora species), orange mangrove

(Hrr~gzriercr species), black mangrove (Aiicetutia species) and milky mangrove

(Excoecuntr species) are recognized. Acarlthrrs i/ic~fo/;lrs L. was found distributed in all

stations except Karun~allor. In Karumallor, Excoecaria itzdica Willd. was observed. This

species was found endemic to this region. Other species of Excoecaria was represented in

other stations A~Vceta~icr c?Cficirrtrlis L. was surveyed in almost all stations except in

Pattanam and Kammalloor. At Pattanam only are species such as Acattfhlcs ilicfotizrs L.

was present. Maxinl~nn number of mangrove species were observed at Panambukad

where seven species of mangrove plants were seen. Katid~lia cartdel L. and Riti:ophora

cc~t~delcrrrcr DC. were obsewed at Nettoor and Panarnbukad stations respectively.

H ~ I I ~ I I I L ~ ~ . I I fi).n~t~orhizl~ Lamk was observed in Puthuvypu and Panambukad. However

this plant was also scarcely distributed at Mangalavanam. It was noticed that mangroves

of Mangalavanan] station is terribly affected by the urbanization and oil spill form the

nearly located storage tanks of Indian Oil Corporation. Panambukad, Karumalloor and

Nettoor stations showed the presence of Sotrtlerafia cuseolcrri.s L. A depletion of

Table 1 The mallgrove plant species at different sampling stations observed during the survey

I i 1 ~~ ~ - - L . i~ ~ - I

t~ 1 + - - + ~ - - + + ; i 1 . 4 ~ , 1 ~ c ~ / f t l t ~ / o/~lclrirr/i.c L. Aviceniaceae - + i~ I ,~ ~

+ 1 J 1 . . + j _

I I ! I . I / / / I ~ / . \ t / i f / . I. .\cantllaceae + + + 1 q - + ! +

1 . 1 , . I I i<hizo!jhor.o mrrr~!.o!itr!rr + i + i ~ - - : + i

L a n k

I ilhiropho/.n cntr~Jc/trr.;n

!

cylitrdric~r m

i Rhizophoraceae + - + + - -

WA -

6 Rrrrgr~iercr gymtlorhyzn Rhizophoraceae - - - + + + - - - Lamk.

-

7 Kntidrlin catidel L. Rhizophoraceae - + - - - - - 8 .\i)nr~erntic~ co.seo/aris L. Sonneratiaceae - - - + - + - - + - . 9 Excoecnrin npllocha L. Euphorbiaceae + - - - - + + - - - 10 Excoecnrin it~dicn Willd. Euphorbjaceae - - - - - - - + - -

+Present, - Absent.

Table 11 a

The density of mangrove species of the various sampling stations found during the survey

! Station (1) Kannaniali Station (4) Nettoor 1 - - - - - - -- -. ~ ~

Sps. : 7-- i

i - No. + 1 - - M~lngrove -. s ~ i e s present , I Density1 - ~~ ha .+ i - No + Mrl~lgrove speciegresent -~ 1 Density1 ha I I 'I l 1 1 1 1 1 1 1 c 1 1 1 1 1 I 8 ( ~

-- . .- ~

ilicifo1111.r L -----

3 rRhizophorn ~nrrcrot~nttr Lamk.

4 I Rr~rg~riern cy/irrdr.icn W A .

- I I 1 I

-- Station (2) Kumbalangi Station (5) Mangalavanam - Sps. Sps.

Station (3) Kumbalam 40 1

No. 1

2 Acn~r/hlis i1icifolirr.s L Acarrfhrrs i1icifolin.s L

Mangrove species present Avicrrrr~io qfficirmli.~ L

1760

Mangrove species present A~licer~rlia oflcilialis L

3 Rhizophorn mrrcroiratn Lamk. HR I I

Density1 ha 2500

No 1

Mangrove species present A~~icernria qflcirra1i.s L

Density1 ha 2600

1 S P ~ . I ! i No. Mangrove ~~ ~ speries - . present p~~~~-~- -~ ---- ~- M x t ' o v e - 1 i 1 , ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ l ~ ~ ( ~ ~ L . ~ I I ~ I I ~ . s I . ! A I, IL.~II I I ILI O/~~~L~III~ZI;.V . . L

Table 11 b The density of mangrove species of the various sampling s t a t i o ~ ~ s found during the survey

. -- / ~ / ~ i z o ~ h % m~rcror~rrtrr Lamk +-- 1 3 6 0 j ~ ! , h o r . ~ ~ ~ c r / ~ r ~ a m k :-- 1 -- &--++ ---* Rhizophora cn~rdelorirr DC. 4 I L3xcoecnri~~ ogizl loc/~~~ L. 3620 1

2:: Rrlig~iiern cylirldricn \NA. Station (9) Karumallor

/ Station (6) Panambukad Station (8) Pallipuram 1

A- ...+ - - -7 k Rrl~g~~ierrr ,gyn~rrorh~ztr 1,arnk. 100 Sps.

g 7 Sor~ricrofiir crrseo/nri.s L. 160 --

Station (7) Puthuvypu

No 1

2

Mnngrove species present Sorn~ercrficr ct1.seo1~1ri.s L

E:xcoeccrrin irldicn Willd.

Density1 ha 400

1140

720 --

1940

60

40

Sps. No. 1

2

3

4

5

6

Mangrove species present Ai:icer~r~in ofJici11n1i.r L

Ae~urthu.~ i l i c ~ f u l i ~ ~ ~ L pppp--

Rhizophom 1~711cro11nltr 1,amk .-

Hrrlg~~iern cylitldricn WA.

Rrrrgtiern gyn~r~orhyzn Lamk

Excoecnrin ngnflocha L.

Station (10) Pattanam

Sps. No Mangrove species present -~ - Density1 ha 1 1 Acnr1~1~11s i / i c i j L K ~ 2400

Stnlioe (I I ) M o o t h a k u ~ ~ a a m

Sps. No 1

2

--

M a n g r - s p e c i e s present Avicern~in t?ff ici~~al is L

Acnt~thr~.~ i l ic i fol i r~.~ L

Density1 ha 920

3040

Table In

The dominant species and nomberlha of mangroves sampling stations ohsewed during the Suwey. - ~p ---

I-- . - . Station ! Name of Station ! Dominant Species 7 N u m h e r / h a ;

Mangalavanam A i~icrro~in c?fficirmli.s L 2600 2

. ~. . --

Panambukad Rhitcy~horn mi~cronnta Lam k . 1360 I 1

Puthuvypu Hrriprrem cyli~idrica WA

9

10

I 1

Karumallor ppp

Pananam

Moothakunnam

Excorcnrin irrdicn Willd.

A C O I I ~ ~ I I S ilicijbli~is L

Acar~thrrs ilicifoliri.~ L

760

2400

3040 -

mangrove area of Nettoor site was noticed due to the newly constructed Eranakulam

Alapuzha railway line and Eranakulam Thiruvananthapuram bypass road (Plate 1 to

Plate 25).

Different plant species growing in different statior~s follows difference in

their growth and distribulion pattern In the present study frequency of Aco~ithrrs

ilicrfolir~.~ L. was maximum. Km~delia cniidel L, and Rhizophorn catidelorin DC. was

minimum in the Cochin area Whenever Khizophoro species were present at stations they

,.,ere seen along the banks of'water logged areas such as ditches and ponds.

Figure b shows the variation in number of mangrove plants growing in

different station s studied Species variation observed during the survey is also given in

the figure 6 . Maximum denljity of mangrove plants was observed at Kumbalam station

the Aviceti~~io ( ~ f f i c ~ ~ ~ ~ r l r s L represented in 3800lha. Marked variation in the density of

different Mangrove species was noticed in all the stations (Table IIa and Table Ilb).

There was a difference in the dominant species of mangrove plants in different stations

(Table 111). Ac~u1lhli.t 111c1folirr.s L. was dominated at 4 stations, Excoecnrin at 3 stations

and A~~icerrtrirr at 2 stations. lfiizophorcr and Hrrrgrriern were dominant at one station

each. In the community structure mangrove plants resembled climax species. Occurrence

of competition was limited and if at all present was intraspecific.

Maximum number of mangrove plants were noticed at Panambukad, the

value of Shannon Wiener index was 2.02 bitslindividuals. Diversity value was zero at

Pattanam were the station represent onlv one species. At Kumbalam eventhough only two

species were represented they showed maximum possible natural diversity (Table IV).

Table IV

The diversity index of mangrove sampling stations found out during the survey

Shanon Wiener Diversity index bitslindividual . T

~-

H m u x I E I 1 + ~ -- -4 r ' - 232 I

0 76 I +--159--1 -

I t 076 -1 I

- _ _ i 1.00

4 ' Nettoor 2.32 0.68 i ~~

O g 6 ._I -

G, +- 2.00

2.81

2.59

2.00

100

0.00

l .OO

5

6

7

8

9

10

11

4

10

0.63

0.72

0.75

0.78

0.17

0.00

0.79

Manyalavanam

Panambukad

Puthuvypu

Pallipuram

Karumallor

Pattanam

Moothakunnam

4

7

1.25

2.02

10 1.93

- 5

3

3

5

4

2

1 ,

2

- 1.55

0.17

0.00

0.79

Distribution of mangroves in different sampling stations of Cochin area is given in Figure

6A to F i ~ u r e 6 K

In the present study 4 species of semi mangroves and 6 species of

mangrove associated plants were identified at different stations (Table V and Table VI).

Acro.sfichtrnt urn-ermr L was seen in the most of the stations however, Manglavanm,

Puthuvypu and Pallipuram lack this plant. Plants such as Dolichartdrort spaiheceae L. and

('oesa//)~)ttnu trtrgu I.. were observed only at Kammallor. UerrIs r~l~gtosa Benth. was

noticed in all stations except Kammallor and Pananam. None of the semi mangrove plant

species was observed in common to all stations. Moreover in all stations semi mangrove

plants were seen along with the true mangrove species. Kammalloor station showed

maximum number of semi mangroves in present survey (Plate 24 to Plate 27).

.Amon$ the mangrove associated species C~olophyllrrm ittophyllzlnn L. was

observed only at Panambukad, an island station. Ipon~oen,prscaprrne Sweet. was seen in

Puthuvypu and Pallipuram stations situated in Vypeen island. Thespe.~iapoptrIttea L. was

observed in all stations except in Mangalavanam and Ka~umallor. Clerodetrdr-ort itrernti

L was observed commonly in Kannamali, Nettoor, Panambukad, Puthuvypu, Pallipuram

and Pattanam .\ijlttrc.r nttth~is irrdictrs L. was observed in all stations except in Kannamali,

Kumbalam. I'uthuvypu, Kammallor and Pattanam. Maximum mangrove associated plant

species were seen at Panambukad and minimum at Karurna.llor (Plate 28 to Plate 33).

Table V

Semimangrove p l a n t species a t d i f ferent sampl iog stations observed during the survey , . . ~~~ 7..-.-.p-- ~-~ --

S1 Scmin~;~nero!c sllecics F;~rnil? riGi-rXtYn11~1 I K e r n n N r t t ~ ~ l n x l i l 1 panam 1 ~ u t h u v j ~ a l l i ~ Karu I ~ a t t r !'Tithali7 I , 'VIP I I iu~ei ' i n I \;III;I~ : bukatl 1 )IIII ; warn , m a l l , I un~lilrn 1

I 2 / : 4 5 6 7 8 , 9 1 0 11

/ 3 / Derrix iilipii?oso Ucntl~. ) Fahaceac + i 1 I I + - 1 - 1 + i i i i + + + I

Tab le VI

Mangrove associated species a t d i f ferent sampl ing stations observed during the survey

1 I Cerrhero oifollnnr Gaertn Apocyanaceae + + + + 2 C ' I e r ~ ~ ~ l c ~ i ~ ~ I r ~ i n ttirrtttt L / VC~~~IIWCC~C + + + + + I -

+ Present. - Absent.

T Z n T

Nett oor 4

Puthu \ )pu

7

Palli lu ram

8

Mootha kunnam

11

Mangla vanam

5

Kalv mallor

9

Panam bukad

6

Pat1a nam 10

Fig - 6.A

Fig - 6.B

EJq

Fig - 6.C

Fig - 6.F

LEGEND

Rhizophora mucronata Larnk. - - E3nib.u iera cylindrica WA.

Fig - 6.G

LEGEND m I

49

Fig - 6.H

LEGENB WATER -u

LAND - STUDY AREA -0

U N T S Acanthus ilicifolius L. - I

TATION - 11, MOOTHAKUNNAM

DISCUSSION

The mangrove vegetation possesses marly structural and physiological

peculiarities, and is composed of species with strongly marked characteristics grouped

under 'true mangroves'. There are also plants with less strongly marked characteristics

which are known as semimangroves (Tansley and Fritsch, 1905). There is yet another

group of plants which grow adjoining the mangrove areas but thrive on the land which

does not yet submerged by brackish water even during the high tides but with saline soil. . .

They can withstand some amount of brackish water stagnation for a very short period.

These can be grouped as mangrove associated species (Basha, 1992). In the present study

10 species of true mangroves, 4 species of semimangroves and 6 species of mangrove

associated plants were identified. The pattern of distribution in all the eleven stations

were discontinuous and in patches of varying extent.

I n the Cochin area Acatt/hrr.s i/icifo/ius L,, was found distributed in all . .

stations except one followed by Avice~n~in oflcitra/is L. The later was absent From 2

locations Act~~li711.s i1ictfOlit1~ L. has been reported to occur in varied habitates in the east

and west coasts (Mudaliarr~rd hntm4954). According to them, it was forming large

formation at the edge of back waters of Chirakkal, Tellicherry, Kasaragod and Udupi of

Kerala and tiarnataka states, which is similar to the distribution in the Puthuvypu station

of the present study Other places where Acntttl7tr.s i/ic~fi)i'itts L. formed large formations

in Chiplun uhere it dominated (Joshi and Jamale, 1975) and Bombay (Navalkar, 1973)

where i t existed alor~g with A ~ ~ i c ~ t n ~ i n . Acattlhtrs ilic~fo;folirrs L. is conspicuously absent

from Karumallor This station shows only 17% of possible diversity and can be

considered as the n~aximum affected area in the present investigation. Eventhough back

water zone is surrounding the station expected diversity is absent. The reason may be the

anthropological intervention of the mangrove habitat. Rao and Sasthry (1972) reported

that Acnr~~hri.s i1rc;folius L. is occupying the third zone from estuarine water along with

Excoecnrm agalltxha L., similar to the Pallipuram station of the present investigation.

Kannamali, Pallipuram and Ka~mal lo r stations were dominated by the

genus l<xc~oectrrrtr. ?'his is an indication of the presence of more or less similar

environmental factors prevailing over these stations. According to Joshi and Jamale

(1975) the limits of migration in mangroves are possibly due to their capacity to increase

uptake of potassium and calcium and to reduce the uptake of sodium and chloride ions.

They pointed out that Acatrthzr.~. Excoecnria and Kai~delia are less efficient in these

characters 11 appears that potassium and calcium are responsible for developing salt

tolerance in mangroves. &corcrnin ngallocha L. and Ai~ice~raia rnarirra were the main

species of south coastal Andhra pradesh (Jayasundramma, 1987). At Muthupet mangrove

forests AI~ IL .~ ,~ I I I IU I)KII.IIIU. was the most common and abundant species followed by

Excorcari~r trgi~llocha I,. and Acc~r~/hrr.r. ilic~jolitrs (Kannan el' nl., 1998)

Mukherjee (1975) described Acntithus ilicrfolir~s L as occupying reclaimed

areas, alons embankments and edges of creeks, which resembled the distribution pattern

of Puthuvq-pu, Pattanam and Nettoor. All these areas are developed by reclamations.

Acnr~fh~ts rl t<.~fi) l i~~s L is less efficient in competing with Ai~iceirnia in regions of lesser

inundation 'The stunted growth of Accrr~ll?~~s ilicifolirrs L. in Moothakunnam, and

Pallipurarn are indicative of this factor. in Panambukad and Kannamali the luxuriant

growth of AL.CIII~/III.Y mav be due to the higher inundation rate

In a11 earlier investigation Suma (1995) found that Vypeen block of

Cochin was composed of Ac~zrrfhrrs ilicrfolius L. along with Rhirophora mzrcronata and

A~?crrrtotr oficirm1i.s .. L. At Puthuvypu area Avicerzrria seems to be the early colonizer

followed bv i<hihizoyhora, Derris and Acatzthus respectively (Mohanan, 1997). Hence

Acar1fhrr.s has no pioneer role in the migration of a mangrove community to an area. This

seems to be an evidence of the fast changes in the mangrove vegetation of Cochin area.

In the present investigation Acarrthlis ilicifolius L. and .Avicennia ofJicir~alis L. were

found most frequent in the Cochin coast. It was observed that species diversity gradually

tapers from the Mahanadi and Sunderbans delta of the East mast to the Andaman and

Nicobar islands and Southwards to the Godavari - Krishna and Cauveri delta of the East

coast and is much less along the West coast regions including Kerala coast (Banerjee and

Gosh, 1998) I'his may be due to the large physical forces of saline tide water and lack of

stable substrate At Pattanam onlv one species of mangrove was present i.e., Acarrlh~is

i/ic!fi,liri.\ L According to Venu (1999) land fills, industrial estates and housing estates

for human habitation destroyed mangroves of India.

I t Mas seen that i(/ri:ophorn rnrmotrnta Lanlk. and Hrrrg~riera cylirrdrica

WA. form the dominant vegetation with highest spread over the areas in Panambukad.

While A L . ~ N ~ I / ~ I I . Y i/ic!fi)/lr~s L. together with Hnr~rreru cylirrdricn dominated in Puthuvypu

and A~~icerriritr (?fficirr~~/i.c. together with Fkcoecaria agrrllocha dominated over the

Pallipuram statioris. ilctrtrthri.\ ~I~c!fi~Ii~rs together with Al~icetrnin c~ f i c i r~ l i s were

dominated in stations like hlan~alavanam, Kumbalam, Kumbalangi, Nettoor and

hloothakunuam 'l'his may be due to the effect of same type of environmental factors

prevailing over. these stations. .A riel* association was noticed in Kammallor. They were

mangrove species lixi:ot,caria it~dica Willd. and semi mangrove species Dolicha~~dro~~e

spathac~,tr I..

Maximum diversity of species in the present study was observed at

Kumbalam, where theoretical species diversity was calculated as 1 bitlindividual and

actual computed diversity was .96 bitslindividual. 96% of the possible species diversity

was present at t h ~ s station. It is clear that the maximum possible diversity will occur when

all the species show equal probabilities to occur with exactly equal dominances in the

ecosystem Such type of ecosystem will be more complex, stable and less predictable in

terms of species (Trivedy el a / . , 1987).

Panambukad station is an island which is surrounded by Cochin estuary

and may be least affected by external interference. At Panambukad two species

Xhizophorcr tnr~crontrutn Lamk and Rrzrg~iera cyl~t~drrc~!~ WA, more or less dominate

together as in Kumarakam estuary. Ramachandran and Mohanan (1987) studied about the

mangroves of Kumarakam estuary and observed the presence of a mixed population of

Rhirophoru cr/)rcrrlu/tr~ atld Hrrrgttiera ~).n~tiorhiza bordering the estuary. The mangroves

of the station Panambukad is threatened by the construction of a network of bridges

connecting ('ochin and Kodungallore. If necessary steps 1:o protect the highly diversified

mangroves of this station is not done,devastating effect of bridge construction will result

in col ossal damage of mangroves of that area.

Lotdrlin cattdc.1 L is only noticed in the estuarine margins of Nettoor

station as described hy Ramachandran and Mohanan (1987). This plant shows very fast

disappearance from the mangrove locations of Cochin Nettoor station is drastically

affected by the land filling for house constructions, road and rail expansion. There are no

attempts of conservation of mangroves and as result backwater connection channels and

creaks to the mangrove habitat are now more or less totally hindered by the land filling

activity and water bodies are completely dried off.

.4 f eu species like Excoecaria itidica and Bniguiera parv~jlora are very

rare in Kerala and show restricted distribution in both the coasts (Malabar and

Travancore) indicating fast disappearance of the species due to speedy conversion of land

for alternate land use (Basha, 1992). In the present study the unique species Excoecaria

itldica was frequently observed in station 9, Karumallor. Uolochandrorie spnthacea L.

were reported bv Gamble (1967) in the Malabar coast but now they are not seen near

mangrove locations (Basha, 1992). But in this study i3olichatdrone spathacea L. is

found to be associated with b;xcoecarin itidicn Willd. in some of the areas of Karumallor.

According to Basha (1992), mangrove vegetation along the coastline is

generally the association of KhIzophora species and Hniguiera species, where soil in this

zone gets inundated by the sea water twice in a day. Typical example of this pattern of

associat~on was observed in Panambukad station of the present study and they were

dominant in that station. The mangrove exhibited zonation depending on the soil, salinity

and tidal inundation. Waisel ( 1972) have included Rhizophorn mucrotlata Lamk. in

inundation class 1 i.e., the mangrove floor reached by all tides. MacNae (1968) has

opined that complete zonation would be found only in the areas having considerable

intertidal range So tidal inundation is the most significant factor controlling the

distribut~on of i(hizo/)horn rnric,r~trnln Lamk. In Panambukad and Puthuvypu where the

tidal inundation of all tides occur Khizoph~rn ntricrotmttr Lamk. was found in excess in

the current investigation. Maximum mangrove species were represented in these stations.

Tides help in washing away salt, mixing of nutrients, reducing water temperature and

distributing seedlines (Mohanan, 1997). Rhizophora carldelaria DC. is exclusively found

only in the 6'' station Panambukad. Khizophora was not at all found in station 3,9,10 and

11. This may be due: to low tidal action in all these stations. Ecological condition of

mangrove system and its associated coastal water is influenced by stratification caused by

slow currents and weak tidal mixing ( Anonymous, 1987; Suma 1995).

Some species like Sorrrleratia caseolaris L. shows abundance in

Travancore coast, but was seen rarely in restricted localities at Malabar (Blasco, 1975).

The plant Sororercr~io caseolaris L. was found frequently in Panambukad and rarely in

Nettoor and Karumallor and totally absent in the other eight stations. It shows that this

plant is rapidly disappearing from the region.

Heddome (1866) has described Hr~rgr~irra tzylitrdrica WA. as occuning in

Malabar and Travancore coasts and Brrrgrriera caryophyNoi& in Malabar coast. Hooker

(1972) has also described the above species and further enumerated yet another species,

Hrzrgrriertr n~trltrhto.~ca as found occurring in Malabar. Dn~ry (1864) and Ramarao (1914)

also mentioned Hrrr~:uiercr n~crlahcrriccr as occuring along the Malabar coast. From the

descriptions of the above authors, it is clear that once there existed all the three species in

Kerala coast H u t recent workers have described all the three species to be one and the

same, /.tJ . Nrrrgrrier.tr cylirrdr~cn WA a as ha, 1992).

Both .Yrr~g~~iertr tylir~dricn WA, and Hrrr&v~iera gyrnr~orlliza were present

in Panambukad, and Puthuvypu stations. Brrrgr~iera ,symrorhiza Lamk. was seen only at

Mangalavanam. and Hrrtguic,r~r cylirrdrico WA. at Kannitmali. In all other stations this

genus was not observed. This shows the gradual extinction of this plant from the Cochin

backwater belt Mangroves of Mangalavanam is considered to be a secondary growth

developed after the closing of a timber depot (Mohanan, 1997). This station is

represented by 4 mangrove species. Only 63% of the expected diversity has been

observed in this stati0.n. This reduction in the diversity may be due to the toxic effect of

spilled oil from the storage tanks of Indian oil corporation situated near the

Mangalavanam. Anonymous (2000a) has reported about the devastating effect of oil

pollution to the Nigerian mangroves. Mangroves of Mangalavanam are also often used as

open garhage dumps.

Successional Patterns of Mangroves

Uns~~ccessful natural regeneration because of biotic interference results

in complete loss of ~mangroves. in such conditions only Acroslicirni alireirni L. and

Acnrr/hri.c .s/)eotJ.\ invade the area and become dominant (Singh et al. , 1990). The very

same condition was observed in typical land filled area in Pattanam station. There the

mangrove species Acorrthrr.~ iliclfoliris L. was only found with A c rosficrrrn aureuni L. It

is believed that the succession of the mangrove vegetation is governed by the three

factors namely. natul-e of substrata, soil salinity and biotic disturbances. Due to biotic

interference the mangrove vegetation was fast disappearing. Only those species which are

more hardv and resistant can tolerate and are able to colonize in such environment. The

most important invader species of the environment i:i A~licernin oflcinalis L. and

A~~icerrtr~lr nr~u.~ir<r, being of hardy nature and its higher range of adaptability (Singh et nl..

1990). At Pichavaram Avi~~ctrtrln c?fficitmlis is represented by large trees mixed with

1~lri-o~~hor.tr at the borders of channels (Kannupandi and Kannan, 1998). The limit of

tolerance of each species is determined by its specific environmental requirements. Thus

at the sea front Avia;.rrrrin and Someratia are often the pioneers. Usually species with

large propagule size are sorted towards water front while those with smaller propagules

and ability to withstand less salinity to hinterlands (Mohanan, 1997).

4 common observation during this study is that the reclaimed lands are

first colonized by A~~icnirria ~flicirialis L. followed by A~:atrfhzrs ilicifoliz~s L. Mangrove

plants are not allowing any understory species and hence no stratification was observed.

Semimangroves and Mangrove Associated Plants.

In the present study Derris ulignosa Benth. the semimangrove, is found to

be closely associated with true mangrove species especially Avicetrnia oflcinalis L.

Derris t,li~vro.v~r Benth is found in all stations except in 9* and 1 0 ~ stations where

A~~/crt~tt/tr (?fliotta/is L. is totally absent.

Uone of the mansrove associated species is observed in common to all

stations But ('errhr(z tdollani Gaertn is noticed in 7 sttations out of 11 studied. No

speciality. specificity or relationship between the occurrence of mangrove associated

species and mangrovt: species were observed (Suma, 1995).