Mangroves of India: History and palynostratigraphy of Chilka Lake, Orissa
H. P. Gupta & Asha Khandelwal
Gupra, H I' & Khandelwal, Asha 1990. Mangro\cs of India: Hisl,)r)" and palvnosrraligraphy of Chilka Lake, Orissa. 117: Jain, K. P. & Tiwari. R. S. (eds )-1>roc. SI'JlZp. 'Vislas in Ilidiall ealaeo!Jo[CIIlj'. Palaeobolallisl 38 : :379 393
Fine resolution palynostratigraphy cenrred on Chilka Lake is aimed at the reconsrruClion of histolY of mangrove vegctalion in tidal nat, salt marsh and fresh water wetland el1\·ironments. Pollcn analyses of air catches, lake water, lake bOllom mud and surface soil samples have been collecrively used to <.juanriFy rhe dispcrsal and preservarion ot' pollen in relation to the modern \·egetation. Pollen analvsis of a 'i. 50 m deep prof; Ie from Halugaon al the weSlcrn nank of the lake in prograded della zone has been done which provides information about the changes in vegetation and deposilional environments from apprOXimately 3,100 radiocarbon years 13.1'. to the prescnt. The results obtained suggest that (i) air catches are devoid of mangrovc taxa instead seasonal non·arboreals and planted trees dominate, (ii) lakc ,vatcr. surface sedimeI1ls and lake bOllom mud samples have recorded the occurrence of both core mangrm'es and mangrove associates to thc extenr of JO·33 and 'i0·H3 per cent. respectivelv, and (iii) Balugaon profile portrays the existence of marine. brackish and fresh warer bioassemblages. On the basis of subtle changes in rhe vegetarion, various depositional eJwironmellts, rransgressive and regreSSive facies have been detcrmined.
Key-words- MangrO\'es, Palynostratigraphv. l'alaeoenvironmel1l, Chilka I.ake, Quaternary (India l.
H. P. Cupla & Asha KIJandelu'al, lJirbal Sabni h,slilille oj ealaeo/Jo/(lny, 53 (illil'enil)' Noad, LIICkllou' .!26 007, India.
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'""" ~ ~ : ~ ~ ~ 1fh:f"" ~ ~ 4 ~~ ~I~ ~ ~ ~ ~ ~;p;;?t ~ 4(1'"0If~il>fuxn 1Tm if; WG'>T -q if; qful:fOT ~ -~ 0fIT~ ~ ~ ~ ~ ~ 5.50 l\tv:: ~ qf{~fi;ifiof; .r 3.100 '(i'\;,ilil>lal'1 qq '!'l'.r 3lf'jf ~ ~ ~ ~ ~I~u ~ ~ ~ ~ ~-'RJlTiliUT~ ~ 'f( .r fu; (i) 'flJ:'IT-q 3fC!e\tlif ~ ~ ~ ~ (f'/IT 50-83 qfu-!ffif ~ -q~~, (f'/IT (iii) ~ qf<~~il>1~, mt ~ ~ ~ ~ R~ ~ ~ ~ ~I ~ if; 3ITUR 'f( filf\r>r (f'/IT 3l'rnrtTl!!f 3!f'lTmfT CHILKA lAKE (Lat 19'5'-20', Long. 85'6') south them is Bhargavi, pour into the lake at its northern west of Puri, is an open lagoon and measures to flank. Thus, the salinity of the lake fluctuates about 65 km NE-SW and 20 km E-W at the widest periodically depending upon (he incoming of water point The word Chilka denotes the birds' paradise. from sea or rivers. The salinity effect is more south Chilka lagoon is connected with bay of Bengal eastward and decreases north-westward causing through narrow channel at its eastern flank; there is floral, faunal and depositional distinctions. It is a regular sea water entry into the lake particularly shallow Water eutrophic lake and proVides an abode during storm surges and hurricanes. Several to the life to dwell in. distributaries of Mahanadi River, prominent amongst Two types of islands are common in Chilka Lake 379 .380 THE PAlAEOROTANIST immediately on the lee of the spit. This geomorphological feature is one of the important aspects which might ha\'e caused tile origin of this brackish \Vater lake (Ahmad, 1972), The alluvial islands within the lake and at its mouth are the depositional features. This line of islands is faced leeward by 40 km long spit which is remarkably straight and only a few meters wide. Behind this spit there is a belt of small islands (2-3 km wide), and bordered seaward by a narrow creek OS" bervveen the spit and alluvial belt of islands. l'UoIKIRO S(llU81~ ~ ___~ [ -W\' s...,lT 1£11.. X[O FO~U' Laterally the allUVial belt has been breached bv ~.""''''"'~''''''.,''~~ ~ D(fORHJ[O..l ....1010,.,,'" (II ..... ,. "001010\ u;~.------= u·\ numerous transverse creeks that connect Chilka Lake with sea and provide passage for the ebb and flow of Text-figure I-Panoramic "iew of Chilka Lake. Mahanadi Delta. Orissa. tielal water. The islands off the mouth of Mahanadi are composed of newer alluvium. The geology of rocky (i) rocky granitic mounds up to a height of 15 m islands near north-western flank of Chilka Lake is the which are perhaps the result of orogenic trend of same as that of adjoining area consisting of base rock, and (ii) muddy islands which are the later Khondalites, the richly garnitiferous gneisses and emergence of land after recession of sea water, schists containing graphite and marked by an generally inundated during rainy season (Text-fig. abundance of sillimanite (Ahmad, 1972, p. 33). 1). Prominent amongst muddy islands is the As regards the age of deltas, the Chandbali Nalabana (10 sq km) on the south-eastern flank Formation, an ancient shoreline in Brahmani located almost in the centre of the lake. There are a Baitarni deltaic complex, was formed during the last n umber of small and big mud islands, collectively 6.000 years synchroniZing last global rise of sea level known as 'Parikud' island. (Mallick el aI., 1972). Niyogi (1971) delineated the ancient shorelines at the Orissa coast ancl recognised GEOLOGY AND GEOMORPHOLOGY various geomorphiC features such as (i) rocky shoreline near Ganjam (--18 km), (ii) sandy spit near General tOpography of coastal region in Chilka Lake (64 km), (iii) deltaic shoreline from Mahanadi delta is marked by mangrove swamps Brahmagiri to Talpada 004 km), and (iv) sandy abutting the shore but towards inland it is a plain shoreline near Balasore (64 km). Earlier, it has been country traversed by distributaries of Mahanadi. The thought that the development of Orissa shoreline land surface along north-east and east of Chilka lake was initiated nearly 5,000 years B.P., the period is low plain but north-western and south-western when depressed sea level was restored to the ends of the lake abound in rocky projections. In all original level or nearly so (Coleman & Smith, 1964). probabilities Chilka Lake represents an embayment The ancient shoreline after full restoration of a sea in the local shoreline and the formation of sand spits level has been plotted across Ganjam to Balasore at the mouth of Chilka Lake has begonen a protected covering the ebb of Chilka Lake and Cuttack (Niyogi. body of water where sedimentation could be marked 1971). Thereafter, Mahanadi and Brahmani rivers PLATE 1 --+ (All x 1000) 16.17 f\canrhaceae 1. Carvophyllaceae 18. Palmae 2,). Casllarina 19. PhoeniX 4. Trilete fern spore 20. f'abaceae S Unidentified pollen 21 Fern spore 6. Fern spore 22. llnidentified pollen 7 Unidentified pollen 23. Cyperaceae 8,9. Auicennia 24. Pal mae 10, II Borasslis 25. Acacia 12,13. LagerSlroemia 26. Unidentified spore 14,15. Unidenlified pollen GUPTA &. KHANDEL\X/AI.-i\IAJ'JGRO\'ES OF INDIA 3Hl ..' '-~.'!:::,....._,'" " ~ .-~; .,'\ .~' ... H ,,'" 'r .. ; , .• ·'da -.. ,' •• : ~ ~~~.l·.~ It~ ~..., ~ .-?~~:l\ll"• . I' \. ''=~....\.% ~._:.t·: ....' ~.' 11 . )& ~,..,.C(f . 'I '. ~\;.~..'" . (.:~~.t',h}j" , .,.( J ~'.~ •'I\'\'1 , ~).. --:~., . 21 . \ .•. t"i ~ ... . j,~:" . \ .""I'll' t'\~'.• , , ,,\ ~ ( ... [J .;:. . ) '. •.. l1 • 1 '. •• .I '''. - II'. • I' ~ • At , , ~ .{, ""1,." • i ~~.... ':.. . ! -.... '~ '.~0. • ~. • • • •.J".•• " .,. , • f ..... (I PLATE 1 • )82 THl I'ALAEOBOTANIST starred pouring deltaic sediments into the (.,..."...\...... , -'"."" structurally controlled bay and quickly built forward ~) -' :,'! an arcuate delta. Sediments shed by the fast eroding '...., ."\.~\ spurs near Ganjam were moved north-east by littoral (' \... ,, ~. currents and a spit was thrown from Ganjam This .~. spit ultimately connected with the rapidly bUilding delta and in this process formed the Chilka lagoon. VEGETATION AND ECOZONES n.." ....o:1. , ,C.""'iIlGo<:lHG Mangrove vegetation in the recent past had been ;-11.000,,",<1.,, O SEA -INTRA TIDAL IN TER TIDA..::L---=-c:-=-:-=----:-::-:-_=_ SUPRA TIDAL-LAND EUES TUARtNE PROES TUARtNE (oMANGROVESCRUB) TIDAL MANGROVE I" PROHAL~NEEUHALINE SALiNTY< 50'/. ~ (SALT W.A.T.ER.MIXED FOREST) ( BRACKISH WATERMIXEDFOREST) .~L..O~/.. .1 ...."'~~"';\)'...... ••..•.:i·>"::~::~:;,::"",,,,~L -·ORY:Pj.';'SE· WE(PHASE: .:;::;:,' ._,. .".', :,.~,- ~ Phoenix oaludosa Rhllophora rnucronata Bro .....o!owij A.canthus Illcifolius Porteresia coar Text-figure 3-0verview of deltaic complex in India with special reference to Mahanadi Delta. Orissa Mahanadi delta shoWing a great degree of fidelity to MATERIAL AND METHOD their respective zones (Chowdhury, 1984; Banerjee & Rao, 1985; Banerjee, 1987)- The taxa encountered During the survey of Chilka Lake, covering a from different zones in estuarine complex are distance of about 20 nautical miles starting from the mentioned in Te>-.1:-figure 3, western flank of lake near Barkul Panth Niwas to Banerjee (1987) has identi fied two broad based Parikud island in the south, around 13 modern sections in Mahanadi delta, an outer funnel-shaped samples of surface soil, lake bottom mud and lake estuary along the river mouth and a narrow inner water were collected and analysed in order to have estuary behind the river mouth corresponding to the pollen/spore display, and actuo euestuarine and proestuarine, respectively_ He pollen/vegetation relationship. In addition, a 5_5 m considered effective wave action development of deep soil profile from Balugaon, about 4 km north stranded beach ridges on tidal flats and absence of west of Barkul, was procured and studied Rbizophora to delimit outer estuary from the inner palynologically to reconstruct palaeof]oristics, estuary_ The outer estuarine zone covers mostly tidal Lithosrratigraphically, sediments could be flats and is dominated by Auicennia marina except broadly classified as sticky clay with silt and sand in for newly exposed areas which are inhabited with different denominations up to a depth of about 3 m saline grass, such as Porleresia coarClala and the from the surface, Thereafter, sediments become upper units are covered by Sonneraiia grllfilbii, S_ more compressed and composed of blackish grey, alba, Bruguiera cylindrica, B. paruzjlora, Auicennia stiCky clay with abundance of fish scales_ In addition, alba, Lumnilzera racemosa, Ceriops lagal, Aegialilis interbedded bands of black organic mud are also rotundifolia and occasionally Pboenix paludosa_ In recorded at places, The details of lithostratigraphy the inner estuary, on the basis of soil/salinity and are as follows: vegetation fraternity, three ecozones are identified, 0_0-10 m Brownish-grey clay with coarse sand_ viz_, (i) a zone of typical mangrove habitat with Organic matter negligible_ members of Rhizophoraceae adapted by means of 1.01-1')0 m Brownish-grey clay 'l..-ith medium to vivipaly and stilt roots, (ii) a zone of less coarse sand Organic matter negligible. pronounced mangrove habitat grouping different 151-2')0 m Grey sticky clay with silt and fine sand, with 1-2 cm thick sand band at 220 m taxa and adapted by means pneumatophores and of depth. buttresses, and (iii) a zone of transition between 2_51-300 m Blackish-grey, sticky clay with sill and mangrove and upland taxa. organic matter. 38'1 THE I'ALAIDl30TANIST •5- .. 23 2 o PLATE 2 ClJPTA &. KI-IANI)ELWAL-MA.l\JGRO\TS or INDIA 3H') II SAMPlE NO. II \011 SAMPlE 110.1 SAMPlE NO. J SAMPLE NO 41\01) ------~ BARKUL/~ :-"'§ALUGAON ' __ -- - _ ,/----- /fiS~]';. ~ IN()fX ....., J 1~.~O:ne9,.:::9::::f:'~te''',,-A'(A R:. /C) ,<--J ]}J AQu.tic fijXiJ C--- ...... _- 9 lV DrIfted fOlilJ(OJ ,--- RMfBHA KAWA : 1I Fer,., spor. \ _~/(J""f\...:f'.....~ ) IWABA A e VI Oi.tom I ,~... ~ '-"~ ~ 7 Y1l Dinar/agel/at. I .8 VlD. (onc.nrricysris \ BHARGAVIR. ~ rx M,croforafT),nifrrij -- - ~ --- :'A IV __ FvngOil spore SAMPLE NO 13 X. SAMPlE NO. S ":? ,,'~~..-'; ..._..::,.... // , SAMPlE NO. 12 SAMPLE NO.6 SAMPlE NO.11 1\011 SAllPLE 110.10 SAMPlE NO.9 SAMPlE 110.11\01) SAMPLE 110.7 Text-figure 4- Pollen deposition model at Chilka Lake. 3.01-<.00 m fllackish-gre\', 'Iick:r cla\' with g\'uja and pollen/vegetation relationship, a variety of samples 0.51 em thick bands of black organic such as air catches (Text-fig. 5) lake water, lake mud one each at 3.'i0 m, 3."0 m and bottom mud and surface soil (Tex,-fig. 6), has been 40 m le\els. il1\·estigated. An area of about 20 nautical miles from '\.01-550 111 - Blackish·grey. ,Iicky cla~'admixed \"jlh black organic mud and g\1tja wilh Barkul at the western flank of the Chilka to the abundant fish scales. Parikud island at the south-east and further south· west at Rarnbha has been covered. Core rnangroves, POLLEN DEPOSITION MODEL AND MODERN mangrove associates, aquatics and long distance VEGETATION drifted taxa have been put together for To evolve the pollen deposition model (Text understanding their relative frequencies. For fern fjg. 4) at Chilka Lake and to work out the modern spores, diatom frusrules, dinoflagellate cysts, +- PLATE 2 1· 2. Terminalia, x 500. I') Nvpa jrutiCGns, x 'j00. ,'1,4. Avicennia, x 'i00. 16. Apoc:rnaceae. x 'i00. 'i Chenopodiaceae. x 'i00 17,18. Coscinodiscus, x 1000 (Girdle and valve \'iews). 6. Unidentified pollen, x'iOO. 19. Mal\'aceae, x 'i00. 7 Pandanlls. x 500. 20·24. Trilete fern spores. x 500. 8. Rh iwphoraceae, x 1000. 25. Cocos nucifera, x 500. 9. Caesalpinia, x 'i00 26 Unidel1lified pollen, x 500. 10. jatropba, x 500. 27,28. Acanr!JIIs ilicijolius, x 500. I l. Aburilon, x 'i00. 29. Polygonil I/J, x 'i00. 12. Unidentified pollen. x 500. 30 Unidentified pollen. x 1000. 13. Sonneraria. x 500. 31. Barrillgronia, x 500. 14. Unidentified pollen, x'iOO. 386 THE PALAEOBOTANIST concentricystis cysts, microforaminiferal inner t.UMSER Of PCUf N GRAINS "U"B£R OF FU~GAlSPORtS Co :;, d linings and fungal spores, the qualitative system of ~ ~ "nJU ,.....---,1'1J08 :nJU 2J.) IS" relative abundance has been adopted (Andrews, POA([A[ 2'-3.U AI TEPNAPIA 2~'> IS! 1966) Each taxon is, thus, rated as follows: CYPfRA([Af Abundant-Atleast one specimen in all fields of URfOOSPOPf AR(j[NON[ view. OF PUCCINIA Common-Atleast one specimen in many fields RI[{HUS [[AOOSPOPIUH ~ J of view. ~ TERHINALIA fPICO((UH Rare-One or two specimens in entire slide. = H[UACfA[ ~ Air catches-Pollen calendar frorn the air =- ASPfRGlllUS catches prepared at the bank of Chilka Lake near XAHTHIUH ~ ([RCOSPOPA Barkul during the later half of March. 1988, a r HELlOTROP/UN blooming time for most of the trees, has depicted ~ NlGROSPOPA b (ROTON TfTflAPLOA that none of the taxon belonging to core mangrove ~ ~ I or mangrove associate has been recorded. The (HfNO-AHS. TORULA ~ pollen taxa recorded in the air catches belong AS TfPACfAf UNIOENTlF/fO mainly to the ground vegetation. Nevertheless, TAXA k HORUS arboreal pollen encountered in this assemblage J belong to Morus, Ailanthus, Holoptelea, Myrtaceae, HOlOPTflfA Meliaceae, Pandanus, Terminalia, etc. which are r either drifted from hinterland zone or planted in the MIHOSA Is AILANTHUS near vicinity. In addition, a large number of fungal ~ spores have been encountered and important AI TfRNANTHfPA ~ amongst them are Alternaria, Helminthosporillm, PANOANUS Cladosporium and uredospores of Puccin ia. ~ Lake water-The study of samples 0, ],4,8 and APIACfAf r 11 of Chilka Lake water amounting 500 cc each has HYRTA([Af F revealed that the quantitative pollen potential of UNiOENTlFlfO core mangrove and mangrove associate taxa is low. TAXA However, pollen spectra obtained from each sample Text-figure 5-Air catches at the western nank of Chilka LIke, depict the dominance of mangrove associates Barkul, Orissa followed by core mangrove taxa, but the values for these taxa are inconsistent. For example, core mangroves are better represented in samples 4 and forest recorded in the modern samples are ]I whereas mangrove associates are rich in samples Rhizophoraceae, Aegialitis, Heritiera, Sonneratia, o and 1. Holoptelea has exceedingly high values in Nypa jruticans, Acanthus ilicijolius, Xylocmpu5, samples 8 and n. Casuarina pollen is higher (12%) t"xcoecaria, etc. whereas mangrove associates are in sample 0 but much reduced in samples 8 and 11 represented by Cocos, Borassus, Pandan'us, and absent from samples 1 and 4. The ubiqUitous Lumnitzera, Anacardium, Ban-ingtonia, Palmae and taxa like Poaceae, Cyperaceae and Chenopod iaceae several herbaceous elements including grasses, are present in greater values in all the samples. sedge s, ferns and chenopods. Amongst aquatiC taxa, Potamogeton and Typha are Lake bottom mud-Samples 2, 3, 5 and 6 were richly present in samples 0 and 1 only. Long distance collected from the bottom mud of Chilka Lake. The drifted pollen are represented in good frequency in pollen analysis has revealed the expansion of core all the samples. The core constituents of mangrove mangrove taxa and reduction of mangrove associates PLATE 3 - 12. Uni~entifiedbodies, x 1000 11.12. Fungal spores, x 500 3. Pediastrum. x 500. 13. Tetraptoa, x 500. 4. Microthyrioid SlrUClUre. x 1000. 14·19. Dinoflagellate CYSl, x 1000. 5,6. PinIlularia. x 500 20.21. Fungal spores, x 1000. 7 Fungal spore, x 1000 22. Tetraploa, x 1000. 8.9 Ammonia. x 500 23. Fungal hyphae, x 1000. 10. Pediastrum. x 500. 51->- , ; 5 = if ~-....: .~ :':; ~ "-t~~ .-;;... .. ... .. -'-~, ~F.:-:-);~:. ~ ~ ~'1=' \J. i l~i ~'i=> ~~ J:::"., ~-."'~, r, '~~. ~ . :1 ' i: ,., i. .. ~(.~ 1 • ~~~ ~!iU Ifl'j' ! :"';,,·ii~ '~'11 I·j ~~II' ',r \~i' ":1"] : , 6 .... \ .. ~ INI)!." 4 OF . 10 "- .:1: '.- .. . I. .. ,;...; '.' • J ...... '··'c· '- 3 . , ::: _ .:,. '-.( ! . ,'~~ 8 . -'-~ .", ~ • '. - . '.;' ".~ .. ~: " PLATE "'$ ~ . " K~V\NDELWAL-MANGRO\'l':S 22 & '- ,r!' oil~" 9' t(," GUPTA '<'000:)) 21 .F \_ ,~, .;(::;, ft. /; ," "" ~ .c I~ ::'.(i ~~"15 4-11, .',- ~,. 388 THE PALAEOBOTANIST ~ •~ -rj ~~I r' S .. MPl[ . aonol-! o .. .< u, ::t .....l.e.., ... ~ i' ~ r: .tn ..'Hl'o oc;",UiA, , 1. , ·. ~~ o ....L... a..."'... ~ ·Oro... ~ o;AUJ"" ""T MVO ) • U r • + ~ N ~ IN'S.C ....!L>( ... ..J . 8rTW!:£,. ,PARIICVO "'...L ...S ...,. ... f5II.TW(['" IC.. LI)....! .... « HAl ....' ,U.l ... :l sn UNP TH ~ ..,V:~~,~:rclA.. 0:{ P"'!"!"'''''''''S, eARICV\. "::"1 1I 1 I I 1 1 I I I. II IIIII.IIIIIIIII II III I I '_ i ~ ~ ~ l !l! l o S000 000 0 000 10 (l 0 0 (I 0 0 0 5 0 0 0 0 0 ft 0 0 0 0 n It .. " X ...I, . "'_ ,.. ..I,< 1\ W F W .W . • ~ U f :! 1. • W• ~ Z r: w Z Text-figure 6-Modern pollen spectra at Chilka Lake. in general. Casuarina (14%) is considerably high in No mangrove taxa was recorded from sample samples 2 and 6 but absent from samples 3 and 5. no. 15 though it has good representation of taxa like Poaceae is constantly high in all the samples. Termina[ia, Lagerstroemia and Azadirachta. Cyperaceae and Chenopodiaceae remained Poaceae, Cyperaceae and Chenopodiaceae are moderately high in samples 2 and 3 but Cyperaceae present in low values. Aquatic taxa are represented declined and Chenopodiaceae improved in good frequencies as the sample was procured proportionately in samples 5 and 6. Amongst aquatic from the bank of an artificial lake. taxa, Potamogetol1 is higher in sample 2 but The analysis of all the samples has revealed that subsequently declined in rest of the samples. Lemna except Casuarina and ubiquitOus taxa, the and Typha are present in low values in samples 2 mangrove associates dominated and core mangroves and 3 respectively. Long distance drifted pollen are co-dominated the vegetation. This pattern of pollen absent except for sample 2. spectra is incoherent with the present day vegetation SUijace SOil-Samples 7, 9, 10 and l2 were mosaic in and around Chilka Lake. Present day collected from the surface sediments from in and condition of mangrove degradation is wide spread around the lake and sample 15 was collected from all over the area. In view of prevailing contrast Nandankanan, a ,;vild life sanctuary near features between the present day vegetation mosaic Bhubaneshwar, away from marine innuence and and pollen record of the surface samples, it could be shall be dealt with separately. Sample 9 records deduced that the core mangrove pollen taxa are highest values for Rhizophoraceae followed by derived from nearby mangrove forest abutting the Auicennia and Excoecaria. Rhizophoraceae has sea shore. Owing to the fact that several contrivances considerably reduced but Excoecaria has shown are present in the mangrove taxa, their pollen remarkable increase in sample 12. Rhizophoraceae is transportation from far off places can not be ruled absent from samples 7 and 10. Mangrove associates o\lt. The mangrove associates may have derived from on the whole are scatteredly moderate. Casuarina midland as well as upland vegetation zones. pollen. record exceedingly high values in all the samples. Poaceae and Cyperaceae continued to be in POLLEN DIAGRAM AND PALAEOFLORISTIC higher values but Chenopodiaceae pollen are absent COMPOSITION from samples 7 and 10 and low in sample 12. Aquatics and long distance drifted taxa have Based on pollen statistics in a vertical profile registered low frequencies. from Balugaon covering a time span of 3,100 ± 270 GUPTA & KHANDELWAL-MANGROVES OF INDIA 389 ~~ ~f ~~ ! ~ )lQO:270y,s 8P II'lOEX ~ . < ,. . ,- w ~ ~ <{ .... uJ « j ~ ' Text-figure 7-Pollen diagram from Balugaon, Ori,sa. years 13P., a pollen diagram (Te>..1:-fig. 7) has been hracki:-,h \\'~lterconditions and i~,ll.II.I,ll'll..,lll (>\ prepared and relati\'e frequencies of each lagoons \\'ith fluctuating \yater lc\ ,I.~It I~,lbu ....lld pollen 'spore taxon have been plotted. In all, fi\'e tlut it can withsund saJini[\' of lip Iii ')1) p,-'r (L'lll pollen assemblage zones ha\'e been proposed in albeit in c.hyarf cOlldition (l3ranes, 1'):-;11) 1.\\(I('t(II'liI ascending order and prefixed with the site initial, is consisten,tly moderate througl1uut lile I. U Ill: e.g., f)-I ro E-V and the zone g-\, has been further Heriliera is presenr in moder3tely WHld \~"L1CSin the subdivided inro three zonules, viz., a, b. c. This has first half of the zone and later \·ani:-.hld ;11 the point been done to express biostratigraphic units in terms of peak formation of Rhizophoraceae. AI'ieeliliia of palaeO\'egetation and to translate significant reappeared at top of the lone. Nypu jrlllicCllIs and events and episodes since the time of deposition of SOlilieratia, inhabitants of high nitches, appeared ill l:3alugaon sediments. Each zone has been separately good fr~quenciesin the bottom samples but discussed. \'anished from rest of the zone Mangrove associate taxa in this zone are Zone B-1 (5.50-4.40 m) inconsistent and sporadically high at places For This zone is marked by an overall dominance of example Cocos, Pandanlls, BorasslIs, Palmae, core mangrO\'e t3xa. All the four taxa, viz .. Cerhera, Termina/ia, etc. and fabaceae, Rbizopb ora, Ceriops, Br/lglliera and Kandelia are Barringwllia, Lagerstroemia, Ahllti/on, /:'mhhea, etc. clubbed together under Rhizophoraceae. It are recorded from the LIpper and lower parts of the predominated the vegetation and attained maximum zone respective!v. Hinterland vegetation is spo('adic values in the first half, attaining a peak of about 20 and scarce, The taxa belonging to upland vegetation per cent. Thereafter, it declined and later attained are iVleliaceae, ./usticia and Artemisia. Poaceae, another peak at the close of the zone. Auicennia and Cyperaceae and Chenopodi3ceae are grouped under Acrosticb/lm made the humble beginning but ubiquitous taxa in view of the fact that their improved later and attained peaks coinciding with members occur in all possible habitats and the Rhizophoraceae. AI'iceJ1l1ia has preference for palynology does not help much ill discriminating 390 THE PALAEOBOTANIST the mangrove taxa from the taxa of other habitats. and at the same time fresh water discharge increased Nevertheless, the symphonic behaviQur with the proportionately encouraging the influx of salt mangrove taxa could help in evaluating them for tolerant taxa to withstand. further interpretations. Aquatic taxa are represented by Myriophyllum in good values throughout but Zone B-III (3.59-2.40 m) declined at the close of the zone. Typha is locally This zone has witnessed the total disappearance high in the lower half of the zone. Both monolete of Rhizophoraceae and significant improvement in and trilete fern spores are abundant. Nypa jruticans, Heritiera and Sonneratia values. The palaeofloristic picture of zone B· I suggests Avicennia, 1:.xcoecaria and Acanthus are present in that the arborescents were quite high attaining a red uced freque ncies. peak of 60 per cent in the middle of the zone. It has An overall spurt in the values of mangrove also revealed that Rhizophoraceae, Avicennia, associate taxa has been recorded, albeit different Acanthus and Acrostichum were the dominant, taxa have shown different behaviour. Palmae, followed by Excoecaria, Hen'tiera and Sonneratia as Cerhera, Ban'ingtonia and Emhlica maintained co·dominant taxa. This feature of the vegetation higher values in the upper half of this zone, whereas depicts that the typical deltaic conditions prevailed Urticaceae retained consistently good values during this phase encouraging widespread of core throughout. Taxa like Borassus, Terminalia, mangrove taxa. Fabaceae, Ahutilon and Malvaceae remained sporadically high. Likewise hinterland taxa in Zone B-II (4.39-3.60 m) general have improved. The values for Holoptelea, It records the overall supression in the values of Meliaceae, Oleaceae, Artemisia and Caryophyllaceae Rhizophoraceae as compared to the preceding zone. are more or less consistent. Poaceae and Cyperaceae This supression in Rhizophoraceae is dotted with have improved further maintaining considerably phenomenal rise in 1:.xcoecaria and Heritie;a. high values throughout the zone but twO are not Acanthus and Acrostichum continued almost in the compatible. Myriophyllum is a dominant taxon same values as before except that the former amongst the aquatic taxa and maintains considerably experienced depression in the lower half and high value throughout forming a peak of 22 per cent disappeared from the upper half of this zone. in the middle of the zone. Typha, Lemna, and Amongst the mangrove associates, some of the Potamogeton are sporadically high in the lower and taxa such as Ballingtonia and Emhlica have upper halves of this zone respectively. Both trilete achieved consistency. And rest of the taxa and monolete ferns have almost disappeared except enumerated in the preceding zone remained for they reappeared at the close of the zone. sporadically high. However. some taxa like Zone B-III is marked by considerable decline in Terminalia and Cerhera are absent from this zone, the total values of arboreals in the beginning though and Heliotropium which was absent before, is locally it improved later scaling a peak in the middle of the high. Hinterland taxa maintain more or less same zone and thereafter again declines. Disappearance of status as in Zone B· I. Poaceae, Cyperaceae and Rhizophoraceae alongwith significant suppression in Chenopodiaceae show high values throughout, in Avicennia and corresponding rise in Nypa jruticans, the upper half of the zone. Heritiera and Sonneratia suggest the cessation in Amongst aquatic taxa Myriophyllum continued the tidal magnitude giving pace to limnobios to in almost the same value but Typha disappeared. thrive. Nypa is a palm of quiet estuaries Or shallow Lemna and Potamogeton are sporadically high. lagoons in which fresh water runs. It prefers brackish Trilete fern spores continued in reduced values water and does not occur on shores exposed to while monolete fern spores disappeared. The long much wave action and never in hypersaline distance, drifted taxa belonging to coniferae are condition (Tomlinson, 1966). Likewise, Heritiera recorded in greater values in the upper half of this and Sonneratia also favour brackish water fringing zone which were otherwise sporadic in zone B· I. the swamp forest and make their expansion in pure The vegetation mosaic in Zone B-I1 differs stands in the habitat with greater amount of fresh slightly from the preceding zone. There is an overall water discharge. impovhishment in the arborescent vegetation and Zone B-IV (2.39-1.35 m) the values do not exceed more than 30 per cent of the total counts. The supression in Rhizophoraceae There is significant change over in the and significant rise in Avicennia, Excoecaria and vegetation mosaic from B·III to B-IY. Heritiera supports the view that this phase Rhizophoraceae which disappeared in the preceding experienced slight recession in the tidal magnitude zone has reappeared in high frequencies and GUPTA & KHANDELWAL-MANGROVES OF INDIA 391 continued throughout this zone. However, constituents are low as compared to non·arboreals Avicennia, Nypa fruticans, Heritiera and Excoecaria and do not exceed 20 per cent of the total have either reduced considerably or they became vegetation. sporadically high. Sonneratia and Acrostichum have Subzone B· Vb (0.79·0.45 mY-This subzone is vanished but Acanthus maintained its consistency dotted by overall reduction exclUSively in m~ngrove throughout. components. Rhizophoraceae and Avicennia have Mangrove associates, in general, have recorded reduced drastically but Heritiera and Phoenix an improvement. Lumnitzera, Terminalia, Fabaceae improved proportionately. Tenninalia and Fabaceae and Urticaceae are found in greater values than have gained values. Lumnitzera, Cerbera, preceding zone. Casuarina, supposedly an exotic Lagerstroemia, Malvaceae, Urticaceae and Asteraceae tree, has earmarked in the middle of the zone and are represented by good frequencies but most of the date for this event could be extrapolated to them are not consistent. around 800 years B.P. Hinterland taxa too, have Poaceae declined, Cyperaceae improved and improved and are marked by sporadically high Chenopodiaceae maintained constant rise attaining values of Meliaceae, .!usticia, Brassicaceae and summit at close of the subzone. AquatiC taxa, except Caryophyllaceae. Holoptelea, Oleaceae, etc. which for /vlyriophyllum, have ei ther vanished or declined were present earlier are absent in this zone. Poaceae to negligible as compared to the preceding subzone. and Cyperaceae have reduced but Chenopodiaceae Fern spores continued to be in lower values. has gained tremendously. Asteraceae has appeared Subzone B- V c (0.44-0.0 m)- This subzone and continued in good frequency in the first half and is marked by total extermination of mangrove thereafter, declined from rest of the phase. Aquatic constituents. The area is characterized by heathland taxa have dWindled except for Myriophyllum which except for Terminalia, Fabaceae, Cocos, Phoenix and continued in low potential than before. Nymphoides Acanthus which are either sporadic or present in has appeared in this zone and gained high patches. percentage in the beginning but vanished later. The evaluation of this zone reveals that the Ferns have regained prominence and are present mangrove taxa experie'nced setback in general and throughout the zone in considerably high values. displayed erratic behaviour. The mangrove associate This zone displays the overall dominance of and hinterland taxa have gained considerably, The Rhizophoraceae and Chenopodiaceae depicting the first phase of this zone is marked by almost high magnitude of tides. Chenopods are tolerant of extermination of Rhizophoraceae and expansion of submersion and can colonise the shallows and even Avicennia. The midland and upland taxa improved extend into the fresh water influenced zone. significantly. In the second phase Rhizophoraceae lost stability; Avicennia declined; Heritiera and Zone B-V (1.34-0.0 m) Phoenix improved. Besides, midland and upland On the basis of subtle but significant changes in taxa continued to rise. The third subphase is marked the mangrove taxa and also being an important by total extermination of mangrove components and phase of human holocaust covering a time span of improvement in the midland and upland taxa, both about 600·700 yrs B.P. has been subdivided into quantitatively and qualitatively. three subzones, viz., B·Y, a, b, c. It is obvious from the foregoing account that Subzone B· Va (1.34·0.80 m}-It records high during this phase covering a time span of 600·700 values of Avicennia followed by PhoeniX, yrs B.P., the tidal magnitude ceased and incoming of Excoecaria, Lumnitzera and Tenninalia. Casuarina fresh water increased causing considerable loss for is on its climax maintaining significantly high values the gro'wth of exclUSively mangrove components throughout. The other taxa of significant values are but, at the same time, human holocaust can also not Malvaceae, Urticaceae, .!usticia, Artemisia, be -uled out as there are legendary records of Brassicaceae and Asteraceae. increasing biotic pressure over the swamp forest in Poaceae and Chenopodiaceae are present in the near past. their maxima but Cyperaceae has considerably reduced. There is an overall spurt in aquatic taxa in DISCUSSION AND CONCLUSION this subzone. Typha and Myriophyllum are represented throughout in moderate values whereas Investigation of air catches conducted at the Lemna and Nymphoides, though confined in the western flank of the lake near Barkul Panth Niwas lower half of this subzone, are present in high has brought to our knowledge that none of the core frequencies. Both monolete and trilete ferns have mangrove or mangrove associate taxon is improved than before. The total arboreal encountered in the pollen assemblage; rather, :'>92 THE PAIAI::O~OTANIST pollen arc !11llstly derived from heath land Zone B-1 took about 700 years for its I egetatlon development and sedimentation is estimated 10 be The an~lh'sisof samples from different points laiel down at the rate of 1 em per 7 years. This zone Ilithin the Ia~chave yielded rich pollen assemblage. enjoyed the luxuriant growth of core mangroves. Al1lllngst them the taxa belonging (() peripheral Amongst aII the taxa encountered, Rhi zophoraceae mallgrm c....or mangrove associates predominate and predominated the vegetation in the first half; the CUlL' mangrol'es rank second. However, core AuicenJ7ia and Acrosticbum came intO the mangrm c taxa are bener represented in sample nos. prominence in the later half of this zone. Excoecaria ~ ;lilt! II and Heritiera remained moderate. Nypa jruticans ThL' ....tllth tlf lake bonom mud samples has and Sonnerafia were encountered during early pan !·t'll'.linl th,11 thc core mangrove taxa are present in of the zone. Mangrove associates and hinterland taxa hi~hl'ruluL':-' a:-.L'ompared ro lake water samples and remained inconsistent and sporadic throughout. The Ll 1!Tc"'pllndillg rcducrioll in the mangn)\"(; ac,sociate palaeofloristic piclUre depicts that the deltaic u"a Ius IWL'1l not iced cnvironments prevailed and encouraged reasonably Thc pollen ,1I1,th'sis of surface soil samples from good spread of core mangrove taxa. In view of the 111 ~lI1dar()ul1d lhilka Lake does not shmv \'egetal variations in lower and upper pans of this comparability in all the samples. For instance, phase. it is clear that during early pan there had "'~lIl1pk11.J l) rct"tlrds highest I'alucs for core been more sea water influence which enabled m,lI1gn1\" 1';l'\~1II hl'rcas they arc poor ill sample 110S. Rhizophoraeeae 10 flourish and advance. It declined ~ ~IndIII in ,he later half owing 10 fluclUation in the sea level 'I hilS. thl' 0\'<.:1' icw of modern samples analysis Zone B·Il spanned for about 500 years and the h.l.... hl'ougln flllw,lrd rhat they do not hold rare of sedimentation is more or less similar 10 the lIlllf, Irtllil~'III ~tllproh.thilities, this could be preceding phase. This phase is marked by steep l'\pl:lil1L'd as due to the unuer watcr channels or depression in Rhizophoraceae and phenomenal rise CllllCIns 1111Il'h gm'ern the mOl'emem of the water in Excoecaria and Heritiera. Acantbus, 100, reduced huth from St':l and ril'er into the Chilka Lake and, and Acrosfichwn disappeared from the second half Iht'rl!()l'c. dt'\wndillg upon the sampling site. the of this phase. Barringtonia and I~mblicaimproved p()lkn asst'mhl:lge mal' or mal' nOl record marine ancl maintained consistency. The reduction in 1111h1CIKe. In gener:l1. mangrove associates remained Rhizophoraceae, significant rise in Avicennia, l!'}ll1inal1l and core mangroves co·dominant in the f:'xcoecaria, Heritiera, etc. and spun in mangrove pullen assemblage This assessment is exclusive of associate taxa suggest that this change over in the C·(h/wrilla-an introduced plaI1l, and ubiqUitous vegetational influx might have been due 10 the [;1:\.1 Ii kL' Poaceac, Cyperaceae and Chenopodiaceae. recession in the tidal magnitude and at the same The p,lltern of pollen spectra so obtained does nor time increase in the fresh water discharge. matCll Iyjth the present day vegetation because the Zone B-III. in general, is a period for luxuriant prL·I·ailing condition of mangrove degradation exists growth of mangrove taxa, like Nypa jruticans, far and wide all around the lake owing (() the heavy He/'itiera and Sonneratia. Nevertheless. hilltic pressure. In view of the above faers the Rhizophoraceae is absent all through and Avicennia, interplal' of pollen from far off distances cannot be /:'xcoecaria, Acantbus, etc., have reduced ruled oul. and thi,5 has been considered as an considerably than before. Mangrove associate and intricate problem for the reconstruction and hinterland taxa have shown remarkable iI1lerprctation of palaeofloristics. improvemeI1l. Values for aquatic taxa have also Ti,e pollen diagram constructed from Balugaon improved. This set up in the mangrove vegetation has been phased into five zones in ascending wherein Rhizophoraceae is either absent or sporadic chronological order and the IOtal time taken in the characterises the progradation of delta as a result the development of Balugaon sedimeI1ls is ca 3,100 exposed land is flooded more with the fresh water years. While discussing the pollen diagram, we have rather than sea water. This condition lasted for about categorized the whole vegetation as core mangrove, 800 years which is the IOtal period taken for the mangrove associate, hiI1leriand, ubiquilOus, aquatic development of this phase. and IOrTg distance drifted taxa. This has enabled us Rhizophoraceae which vanished in the (() assess the vegetation mosaic and also the drift of preceding zone has reappeared and continued in pollen grains from their provenance. In addition, the high frequencies throughout the Zone B-IV. information obtained from modern sample slUdy has Acantbus and Chenopodiaceae behaved been considered instrumental for the correct symphonically with Rhizophoraceae and maintained evaluation of vegetal complexes. high consistency throughout. AlJicennia, Nypa GUPTA &. KIiANDEL\\'AL-J\'\.i\l'lGROVES OF INDIA 595 jruticans, Heritiera, Fxcoecaria. etc., ha\'e either water flow carrying a huge amount of sediments ancl significamly reduced or remained sporadically high. depositing at the mourh of river. This feature is Sonneratia and Acrostichu117 have disappeared from noticeable by virtue of qUick sedimeI1lation at this zone. Mangrove associates and hinterland taxa Paradip which is estimated to be at the rate ?f I cm have experienced an improvemeI1l. Aquatic taxa in less than two years. have registered a decline and ferns ha\'e improved. This phase spanned for about ')00 years and is REFERENCES characterised by regular inundation of landmass. In all probabilities, the depressed sea level during the Ahmad, r. 19"'2. Coastut ~('()l11orpholog,l'of India \\'. 1-1 preceding phase was restored to the original level in I'al\vardhan. Ne'" Delhi. this phase or else Storm surges, hurricanes, etc., Andre"s, G. \X' 1966. Lale Pleislocenc dialOm~from Ihe Tempe produced high water levels creating congenial aleau'\'alle\ \Xi~consin.Ceol SI/n' profess pap 523A : IT, \VashingILJn. conditions for Rhizophoraceae members 10 colonize. Banerjee, l.. K. & I{ao, T. .A.. 19H'). 1\langals of ~Iahanadidella Zone B-V covers a time span of about 600-700 CUllack OistiCl, Orissa Slale, India, III: Krishn:lmunh). \' years and is over burdened by immense human U:d. )-.\Iarine plul'lls. l!Jeir bio/o!J.J'. cbellli,-l,)' und ntilizu· pressure. This phase on the basis of subtle but lion. I'roc. All Illdia )J'Jllp. Mar. Pian Is, pp. 1.r· I ~2,Dona significaI1l changes in the mangrove and hinterland I'aula, Goa. Banerice. l.. K. 1987 Ecological sluclies on lhe mangals in lhe vegetation has been subdivided into three Mahanadi eSluarine-della, Orissa, India. Trop, Fcol. 28: 11'" sUbphases. Subphase 'a' lasting for about 300 years, 125 records good existence of Auicennia, Excoecaria, Blasco, F. 197). The lTIangJ'(i\'e of India. hell'. Sec. Sci. Tech, Inst Acanthus, Lumnitzera, Terminalia, etc. Casuarina is Francais, Pondicben), 14( I) 1-17~ present in its cl imax whereas Rhi zophoraceae (lranes, R. S, K, 1980. Coastal lagoons, Call1bndge slndies in modern biologyl. Cambridge lin i\' Press, experienced a steep fall in its values, Subphase 'b' is Champion, H. G. 1936 A preliminary su[\'e)' of [he foresl rypes of recognised by an overall depression in mangrove India and Rurma Indian for Rec (NS) 1 1-286. componems and subphase 'c' is dOlled with lOlaI Champion, HG & Selh. S. K, 1968 A re/lised sllrue)' of lhe foreSI extermination of mangrove constituents. This rhase, lypes of India. nle Manager of I'ublications, Delhi, ChIW,'dhLII,', B. I' 1984 A glimpse imo the vegetation of Rhitar· in the hislOry of mangrove vegetation development, kanika wild life sanclL!ary in the Slale Orissa, Indian bot. is important as it signifies the degraded mangrove Neplr 3 (2) 121124 vegetation owing to the biOtic holocausl. The man Coleman, J. M. & Smilh. W G. 1964. Late recent rise of sea !e\'e1 entered into the landscape with greater force and HIIII. geol. Soc. rim, 75 : H33840 better understanding of mangrove wealth causing Gupla, H, 1'. 1981. Palaeoen\'ironments during Holocene time in flengal flasin, India a., reOeCled Iw paJ)'noslraligraphy, 10 irrepairable loss the foresl. Similar results are l'ala!!obolClnisl 27 (2) . 138- 160 obtained from Sunderban-Gangetic plain, Bengal Gupla, H, 1'. & Yada\'. R. It 1990. Hislory of mangrove vegelalion (Gupta, 1981). in Paradip and Jambu islands, Orissa, India for the pasl ')00 Palynostratigraphical analysis of a 3.0 m deep \'ears 13.1'.: A palynological as~essmenl.f'alaeobolamsl 38 : profile at Paradip Island near the mouth of Mahanadi j~9·369 Mallick, S. K., Bhallacharva, A. & Ni\'ogi, D 19~2A compar;Hive River has revealed a degraded mangrove pallern of slud)' of lhc Quaternary formal ion in lile Baitarni \'alle\" vegetation since the time of sedimentation around Orissa with Ihose of Oamodar-Aiay delta area, Lower Ganga 500 yrs B.P, (Gupta & Yadav, 1990). The perio Rasin. Proc. Sem. Ceomo1ph Ceohydrol., Ceoteet. Cunga diciry and intensiry by both pasroralists and lJasin 91-104, IIT, Kharagpul'. araba lists ha ve been assessed in terms of vegetation Ni)'ogi. D. 19~I :'vl'lrpholob')' and e\ollllion of the flala~oreshore· development step by step, In the last phase of line, Orissa. SIIid. I:arlh Sci (K G. Wesl cOlTImem. \'oJ): 289 304 Paradip pollen diagram covering total time span of Rao, \'. S. 19~9.Obsen-ations on Ihe mangro\'c \'egelation of about fifty years, ruthless damages lO the vegetation Goda\'ari eSluar\, I'roc. \)'l11p .l/angrol'e 1957: 36·44. could be correlated with the record date around 35 Rao. T A. Mukheriee, A. K. & Ranerjee. L. K. 1973 Is Acrosl/cb II iii years B.P., when construction of Paradip port came alirelll11 l.. truelv a mangrove fern' Cllrr, Sci. 42( I ~): ~-i~. into being and a vast land was denuded. The lOlaI