E. Demetrescu- Thechlorococcalean alga Botryococcus THE CHLOROCOCCALEANALGA BOTRYOCOCCUS AND ITS SIGNIFICANCEIN HYDROCARBONEXPLORATION EmanuelDevernrscu GeologicalInstiiute of Romania 1 CaransebesStreet, 78344 Bucharest 32, Romania Abstract. The chlorococcalean(Dictyosphaeriaceae), "oil-forming" alga Botryococcusand the significanceit bears in the explorationprocess of varioushydrooarbon iypes are considered,Morphological structure and characteristicsof boththe livingand the fossilspecimens, as well as the ecologicalrequirements - as they all controlthe chainof hydrocarbon-formingmechanisms - are discussed.A concisereview of itstypical forms (physiological states), relative to ihe basicrelationships with the corresponding hydrocarbonsare presented. Igl1yglglllynglggy,. Chloroc.occales,Bot4zococcas, morphology, (paleo)ecology, hydrocarbons It consistsmostly of darkgrey to dark brownclay and l.INTRODUCTION coaly clay interbeddedin the Pliocene coal-bearing sequencesdeveloped along the South Carpathians The colonialalga Botryococcushas arousedinterest Depression An important quantity came from the for many yearsnow due to its astonishingcapability to Miocenesediments of the BlackSea, offshore Romania. synthesizedifferent types of hydrocarboncompounds The laboratorytreatment followed the standard and,by doingso, havingthe essentialprecursory role in palynologicalprocedure involving maceration with HCL contributingto the formationof distinctivehydrocarbon 30o/oand HF 45o/o.Where necessaryto put in evidence categories. the humic content of certain samples,to emphasize Throughtime, there were qrritesome attemptsto put some specificrelationships, vlhich Bofryococcusshows it in a cedainplace inside the PlantKingdom which it with such chemical compounds,KOH 5% has been belongsto and this mainlybecause of its very peculiar consideredtoo, andthe data processingused the Humic status as comoaredwith other fresh- and/or brackish Concentrationscale (HCS) (Demetrescu, rn press), water algae (Fremyand Dangeard,1938; Kiss, '1939; Traverse'1955; Chadfaudand Emberger,1960; Gray, 1960; Nagy, 1967; Combaz,19BA', Pop ef a/., '1983; 3. MORPHOLOGICSTRUCTURE AND CHEMICAL Wingate,1983; Alpern, 1987; Glikson el a/.,'1989;) CHARACTERISTICS Morphologicaland (paleo)ecologicalresearch, as well as experimentalinvestigations tried to explainthe Blakburn(1936) was the firstwho has approached morphological changes as response to specific the morphologicbackground and has givena schematic modificationsof the host habitatconditions, plus have view of this chlorococcaleanalga. The basic structural elements beenapproached too (e. 9., Blakburn,1936; Temperly, are shownin Fig. 1; from baseto top they are: 1936;Round, 1965; Potonie and Rehnelt,1971, Cane, pedunculus,cupula and mucilage. 1976;Tappan, 1980; Wake and Hillen,1981; Wake, Two or more branchesform the pedunculus,each 1983;Kedves, 1986 a, 1988,Kelts, 1988, Guy-Ohlsson, branchincluding one or two pairsof individualswhose 1992,V6r, 'l994; Demetrescu,rn press) growthtook place during one season of development. The basic relationshipsbetween different stages of The mother cell is caught in a cuticleformed of two morphologicaldevelopment ol Botryococcusand the parts:the cutrcleof the mothercell, which has a basal nature of resulted hydrocarbonproducts were also position and emerges from each branch of the investigared(Brown, 1969; Douglas et al.,1969; Anders pedunculus(namely the "polypier"of Chadefaudand and Robinson,1971', Demetrescu, rn press). Emberger,1960), and the cuticleof each individualcell In this study,the discussedspecimens are assigned developedinside the cupulae,Each cell containsseveral to Chlorophyta,Chlorococcales, Dictyosphaeriaceae, protoplasmicorganelles such as nucleus,oil drops, BotryococcusK0tzing 1849, as treated in Pop ef a/ starch, plastids, pigments, and other cytoplasm (1 983) constituents,and has the capacityof storingkerogen. lt appearsthat the mucilaginousstructure representing the hydrocarbonmatrix is bi-functional(Fig. 2). As an 2. MATERIALAND METHOD envelopingstratum ii playsa protectiverole to the outer part of the colony branches,whereas in the form of The materialused in this study has been collected extendedstrings it helpsto link simplecolonies to one over the years and analyses have been performed another and produce a compound colony, either duringa seriesof laboratorystages as requiredby a branchedor unbranched.Cellulose plus pectinous particulartheme that was in progressat a giventime. GEO-ECO-MARINA,4/1999 15_5 Nationallnstitute of MarineGeology and Geo-ecotogy Proc.lntern. Workshop on "Modernand Ancientsedimentary Environments andProcesses'; in Moeciu, Romania,oct. g-15, lggg E. Demetrescu- Thechlorococcalean alga Botryococcus 4 ,l t. I l: ti I I f, rl I t;o ,l,/ 0t 0t / Fig. 1. Botryococcusbranch of a simplecolony: longitudinal section (modified after Blakburn, 1936). (1 )nucleus; (2) oildrops; (3)starch; (4) hydrocarbonmatrix (mostly white hyaline amorphous carbohydrates); (5) cellcap madeup of cellulose and pectinoidsubstances; (6) cellulosic wall; (7) cuticle; (8) cuticle of the mothercell; (9) kerogen; (10) part of the proximalregion of pedunculus. substancesform the cellularwall and conferthe colonya Hillen,1981), but the most adequateis a eutrophic highresistance to decay. mediumand slight acidic pH. The alga dimensionsrange from several microns The salinityof most of the freshwaterlakes is less (usually5 pm to 12 pm in the caseof unicellularstage), than 57oo(normally less than 3oloo),unless more to one millimeterfor mature colony (commonlythe concentratedsolutions are introducedfrom outsidethe coloniesrange between 40 and 100 pm). The main lake. This value representsthe apparentthreshold of colour is brown but it changes to bright green in salinity tolerance of most fresh-water aquatic responseboth to seasonalchanges - that may modify microorganisms(Collinson, 1978 b). lt is consideredthat the lightintensity and nitratecontent - and age plusthe this limit may also be characteristicof deeper lakes reproductivestage of the colony(Guy-Ohlsson, 1992). wherea low salinitylevel can be maintainedby escape of more concentratedwater as ground water through surroundingpermeable soils. As an effect of reversed 4. REOUIREDDEVELOPMENTAL CONDITIONS mechanism,for instance,salt water influxes entering the AND SEDIMENTARYCONTROLS freshwater body through the bottom floor of the respective habitat (which increases the salinity of The habitatin which Botryococcusaccommodates depositionalenvironment beyond the tolerancelevel), a and developsis controlledessentially by climaticand regressionln the developmentof this alga may be depositionalfactors that co-operatewith one anotherto inflicted,regardless the particularstage of growththat enablea successfulgrowth ofthe alga has tc face this change.Conversely, a fresheningof Inland, shallow and oxygenatedfreshwater lakes, even slightsaline ambience by high rainfallmay trigger ponds,pools or slowmovingwaters plus ditches,bogs signiflcantblooms (Cane, 1976).All these suggestthat and puddle or plashy sites accompaniedby a wide when found in sedimentsof marineenvironment (as a spectrumof climaticconditions through the year (Guy- constitutiveelement of an assemblagedominated by Ohlsson,1992) appear as the most commonsettings marinepalynomorphs), this clearlyindicates an influxof and surroundinginfluences, which together, strongly freshwaterinside the marinedepositional settino. or re- contributeto Botryococcusdevelopment. lt may Inhabit depositron. oligo-to mesotrophicwaters with variouspH (Wakeand i56 GEO-EC O- MARIN A, 4/19 99 National Instituteof Marine Geology and Geo-ecology Proc. lntern Workshopon "Modernand AncientSedimentary Environments and Processes"in Moeciu,Romania, Oct. 8-15, 1998 E. Demetrescu- Thechlorococcalean alga Botryococcus l;;_i l;let Esl 15Fm - Fig. 2 Polarview of simplecolony shown in Fig,3/5; at highfocus kerogen becomes visible toward the of colony(K) The way different types reflecting various developmentsand shouldbe followed* afterdeposition developnrentalstages appear suggests significant - by rapid burial to avoid decomposition by climaticand/or sedimentogenetic changes. Any change microbial/bacterialactivity. lf the coloniesare found in in the environmentconditions, such as cold, moist samplescharacterized by high quantitiesof amorphous conditionsor, on the contrary,dry and hot conditions, organic matter (particularlyof aquatic origin), this may be relatedto correspondingmodifications in form indicatesthet the accumulationprocess took place in shownby the livingalga (Blakburn, 1936). dysoxic-anoxicconditions. The input of siliciclasticfraction by increased During an entire developmentalcycle the differing sedimentationrate (due to an accentuatedfluvial stagesmay occurtogether ranging from the unicellular erosion,or a significantinflow of waters carryinghigh stageto skeletonmatrix, or even completelydegraded, amountsof humicsubstances), may drasticallydiminish structurelessand fluffy mass. This happens in cases or even interrupt a given stage of development when all basic morphotypesare found in one and the (Demetrescu,in press).Although a humicsforerunner at same sample, indicatingthat a series of seasonal one given point of grovrth,Botryococcus cannot stand a changes have influencedtheir life cycle prior to the dystrophicambience ancl has never been found in depositionalprocess, as well as duringthe intervalof sedimentsrich in humiccompounds (rbid.) time when this process was in progress. When, It is quiteobvious