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<?xml version="1.0" ?> <tei> <teiHeader> <fileDesc xml:id="0"/> </teiHeader> <text xml:lang="en"> <head>INTRODUCTION<lb/></head> <p>In spite of the abundance, variety and dimen-<lb/>sions of the Nicaraguan inland waters, reports<lb/> concerning their freshwater flora are at present<lb/> scarce and not detailed. <ref type="biblio">GOLDMAN and HORNE (1975)<lb/></ref> and <ref type="biblio" >JUAREZ (1977)</ref> carried out an inventory study of<lb/> Lake Managua phytoplankton. Their samples were<lb/> incidentally collected from the Southern and Central<lb/> regions of the Lake. <ref type="biblio">GOLDMAN and HORNE (1975)<lb/></ref> reported 43 species; 13 of them were Cyanophyta, 17<lb/> were Chlorophyta, 10 were Bacillariophyceae, 2 were<lb/> Chrysophyceae and 1 belonged to the Cryptophyceae.<lb/> The dominant genera were Microcystis, Chroococ-<lb/>cus, L yngbya, Westella, and Melosira. <ref type="biblio">KATUNIN et aL,<lb/> (1983)</ref> also carried out a quantitative analysis of Lake<lb/> Xolotl~n phytoplankton and on several ponds of the<lb/> Pacific region as well. They found that cyanophytes<lb/> were dominant in Lake Xolotl~.n, contributing with<lb/> 49% to the total biomass, followed by diatoms<lb/> ( 29.2%), green algae (18.4%) and other groups<lb/> (3.1%). They reported 15 species and mentioned<lb/> Microcystis, Cyclotella, Scenedesmus acuminatus<lb/> and Oictyosphaerium as dominating.<lb/></p> <p>They further observed that diatoms were the<lb/> most abundant, with relative biomass of 96% in Lake<lb/> Apoyo and 93.2% in Lake Xiloa, whereas in Lake<lb/> Masaya bluegreen and green algae made up 50%<lb/> each of the total biomass. The study of <ref type="biblio">KATUNJN etaL,<lb/> (1983)</ref> is the only existing report about Lake Nica-<lb/>ragua phytoplankton. They identified 46 species, viz.<lb/> 20 Chlorophyta, 13 Bacillariophyceae, 8 Cyanophyta,<lb/> 3 Dinophyceae and 2 Euglenophyceae. The most<lb/> common were: Melosira ambigua, Melosira sulcata,<lb/> Cymbella, Anabaena, Microcystis aeruginosa, Scene-<lb/>desmus and Actinastrum. The biomass of diatoms<lb/> was 44.1% followed by that of green algae (27.6%),<lb/> bluegreens (22.5%) and other groups (5.9%).<lb/> <ref type="biblio">ROSTRAN (1975)</ref> made a list of planktonic and<lb/> benthic algae from Tiscapa Lake. In 1985, <ref type="biblio">RUlZ and<lb/> PUM (1986)</ref>, started a detailed research on the<lb/> specific composition and biomass of phytoplankton<lb/> in Lake Xolotl~n. They reported 26 Cyanophyta, 23<lb/> Chlorophyta, 19 Bacillariophyceae, 2 Euglenophy-<lb/>ceae and 1 Xantophyceae (93 species in total).<lb/></p> <p>The present study is based on samples collec-<lb/>ted monthly in Lake Xolotl~.n from July 1986 to<lb/> November 1988. This is a contribution to the 'Catalog<lb/> of the Freshwater Algae from Nicaragua'.<lb/></p> <figure type="table">Table 1. Phytoplankton species list<lb/> Cyanophyta<lb/> Anabaena sp.<lb/> Anabaenopsis elenkinii fa. circularis (G.S. West)<lb/> Anabaenopsis raciborskii Wolosz, 1912<lb/> Anabaenopsis sp.<lb/> Aphanizomenon sp.<lb/> Aphanocapsa sp. ad A. delicatissima W. et G.S. West, 1912<lb/> Aphanocapsa sp.<lb/> Aphanothecesp. ad A. c/athrataW, et G.S. West, 1906<lb/> Aphanothece sp.<lb/> Chroococcus dispersus (KeissL) Lemm., 1904<lb/> Chroococcus/imneticus Lemm., 1896<lb/> Chroococcus/imneticus vat, elegans G.M. Smith, 1920<lb/> Chroococcus turgidus (Kutz), 1849<lb/> Chroococcus sp.<lb/> Coe/osphaerium sp.<lb/> Cy/indrosfJermum sp.<lb/> Oactylococcopsis sp.<lb/> Gomphosphaeda aponina Kutz, 1636<lb/> Gomphosphaeria/acustris Chodat, 1896<lb/> Lyngbya circumcreta G. S. West, 1907<lb/> Lyngbya contorta Lemm., 1898<lb/> Merismopedia sp. N. 1<lb/> Merismopedia sp. N. 2<lb/> Microcystis aeruginosa Kutz., 1845 -49<lb/> Microcystis e/abens Kutz., 1845 -49<lb/> Microcystis sp, ad M. incerta Lemm.<lb/> Osci/latoria raciborskii Wolosz., 1912<lb/> Spiru/ina sp. ad S. Laxissima G. S. West, 1907<lb/> Spiru/ina subsa/sa Oerst., 1842<lb/> Chlorophyta<lb/> Actinastrum sp.<lb/> Ankistrodesmus sp. ad A. bibraianus (Reinsch) Kars., 1953<lb/> Ankistrodesmus falcatus (Corda) Ralfs, 1848<lb/> Ankistrodesmus sp. N. 1<lb/> Ankistrodesmus sp. N. 2<lb/> Ankistrodesmus sp. N. 3<lb/> Chlamydomonas sp.<lb/> Chlorella vulgaris Beijerinck., 1890<lb/> Chlorot)ion braunii (Nag.) Kon., 1979<lb/> Ciosterium sp.<lb/> Coelastrum micropomm Nag. in A. 8r,, 1855<lb/> Coe/astrum sp.<lb/> Cosmarium sp. N. 1<lb/> Cosmarium sp. N. 2<lb/> Crucigenia sp.<lb/> Oictyosphaerium sp. ad D. tetrachotomum Printz, 1914<lb/> Oimorphococcus sp.<lb/> Kirchneriella sp. ad K. aperta Tell., 1912<lb/> Kirchnerie//a sp. ad K./unaris (Kirchn.) Moeb., 1894<lb/> Lagerheimia genevensis (Chod.)., 1895<lb/> Lagerheimia sp. ad L. ciliata (Lagerh.) Chod., 1895<lb/> Lagerheimia sp.<lb/> Monoraphidium sp. N. 1<lb/> Monoraphidium sp. N. 2<lb/> Neg/ectalla sp.<lb/> Oocystissp. ad O, borgeiSnow, 1903<lb/> Oocystis sp. ad O. e/liptica W. West, 1892<lb/> Oocystis sp. ad O. marssonii Lemm., 1898<lb/> Oocystis sp. ad O. lacustris Chod., 1897<lb/> Oocystis sp. ad O. tainoensis Kom.. 1983<lb/> Oocystis sp.<lb/> Pediastrum boryanum (Turp.) Meneg., 1840<lb/> Pediastrum dup/ex Meyer 1829<lb/> Pediastrum simp/ex Meyer 1829<lb/> Pediastrum tetras (Ehrenb.) Rails, 1844<lb/> Scenedesmus acuminatus (Lagerh.) Chod.<lb/> $cenedesmus ecornis (Ehrenb.) Chod.<lb/> Scenedesmus quadricauda (Turp.) Breb. sensu Chod., 1913, 1926<lb/> Scenedesmus sp. ad S. bicaudatus Dedus, 1925<lb/> Scenedesmus sp. ad S. ob/iquus (Turp.) Kutz., 1833<lb/> Scenedesmus sp. ad S. perforatus Lemrn. 1904<lb/> Scenedesmus sp. ad S. serratus (Corda) 8ohl., 1902<lb/> Scenedesmus sp. sub-section Aldavei<lb/> Scenedesmus sp. N. 1<lb/> Scenedesmus sp. N. 2<lb/> Scenedesmus sp. N. 3<lb/> 9 Scenedesmus sp. N. 4<lb/> Staurastrum sp.<lb/> Tetraedron minimum (A. 8r.) Hansg., 1888<lb/> Tetraedron regu/are Kutz., 1845<lb/> Bacillariophyceae<lb/> Amphora sp.<lb/> Anomoeoneis sphaerophora (Kutz) Pfitzer<lb/> Coscinodiscus sp.<lb/> Cyc/ote/la comta (Ehr.) Kutz. 1849<lb/> Cyclotella meneghiniana Kutz:, 1844<lb/> Cyclotella sp.<lb/> Oiatoma sp.<lb/> Diploneis ova~is (Hilse) Cleve, 1891<lb/> Fragilaria pinnata var. trigona (Brun u. Hedbaud Hust<lb/> Fragilaria sp.<lb/> Melosira sp.<lb/> Me/osira granu/ata (Ehrenberg) Rails<lb/> Melosira ambigua (Grunow) Mueller<lb/> Melosira distans var. africana (Ehrenberg) Kuetzing<lb/> Navicula cryptocephala Kutz., 1884<lb/> Navicu/a cuspidata (Kutz.) Kutz., 1844<lb/> Navicu/a gragaria Oonkin, 1861<lb/> Navicu/a incertata Lange-Bertalot, 1965<lb/> Navicu/a halophi/a (Grun.)<lb/> Nitzschia acicu/aris (Kutz.) W. Smith, 1930<lb/> Nitzschia acicularis var. closteroides (Grun.)<lb/> Nitzschia pa/ea (Kutz.) W. Smith<lb/> Nitzschia tryb/ionel/a Hantzsch<lb/> Pinnu/aria sp.<lb/> Stauroneis sp.<lb/> Stephanodiscus sp.<lb/> Synedra acus Kutz., 1844<lb/> Synedra u/na (Nitzsch.) Ehr., 1838<lb/> Thalassiosira sp.<lb/> Tetracyc/us tacustris Rafts<lb/> Cryptophyceae<lb/> Cryptomonas sp.<lb/> Rhodomonas sp.<lb/> Dinophyceae<lb/> Peridinium sp.<lb/> Euglenophyceae<lb/> Euglena pisciformis Klebs<lb/> Eug/ena sp.<lb/> Phacus sp.<lb/></figure> <head>MATERIALS AND METHODS<lb/></head> <p>Samples were collected monthly during a 30<lb/> months period from eleven points spread over the<lb/> lake. A Van Dorn bottle was employed to obtain water<lb/> samples at 1 m intervals along the vertical profile.<lb/> They were preserved with lugol and formalin (4%).<lb/> The identification of algae was made on fresh<lb/> material collected with a plankton net (36 microns).<lb/> Samples were allowed to sediment and then obser-<lb/>ved. Drawings were made using a light chamber. A<lb/> scanning electronic microscope was employed for<lb/> diatom observation and photographs. Dimensions<lb/> given for each alga are average values of a variable<lb/> number of individuals measured from 1986 to 1988.<lb/> Drawings and photographs of the algal species are<lb/> available from the authors.<lb/></p> <head>RESULTS AND DISCUSSION<lb/></head> <p>One hundred and twenty taxa were identified.<lb/> Fifty-two of them are Chlorophyta, 29 are Cyano-<lb/>phyta, 33 are Bacilladophyceae, 2 are Crypto-<lb/>phyceae, 3 are Euglenophyceae and 1 belonged to the<lb/> Dinophyceae <ref type="table">(Table 1)</ref>. Dominant among Cyano-<lb/>phyta were Lyngbya contorta. Chroococcus limneti-<lb/>cus, Chroococcus sp., Anabaenopsis sp., whereas<lb/> Cyclotella meneghiniana, Nitzschia sp., Nitzschia<lb/> acicularis, Fragilaria pinnata and Navicula sp., were<lb/> the dominant Bacillariophyceae, and Oocystis sp.,<lb/> Scenedesmus sp., and Cosmarium sp., the dominant<lb/> Chlorophyta. They are common inhabitants of alkali-<lb/>ne waters with elevated nutrient concentration.<lb/></p> <p>Cyclotella meneghiniana shows halophilous<lb/> tendencies, prefers pH above 8, high sulphur con-<lb/>tent, high temperatures and eutrophic conditions<lb/> <ref type="biblio">(ROUND, 1981)</ref>. IS has been included in the alfa-beta<lb/> mesosaprobic category by <ref type="biblio">SLADECEK (1973)</ref>. This<lb/> species tolerates scarcity of oxygen and it is adapta-<lb/>ble to variable light. Nitzschia acicularis and Nitzschia<lb/> palea grow better in nutrient-rich water with high<lb/> alkalinity <ref type="biblio">(ROUND, 1981)</ref>. This explains the develop-<lb/>ment of dense populations of these two species in<lb/> Lake Xolotl~n. Fragilaria pinnata develops in meso-<lb/>trophic environments of high salinity; it is an alkali-<lb/>philous species <ref type="biblio">(ROUND, 1981)</ref>.<lb/></p> <p>Aphanocapsa and Microcystis blooms are fre-<lb/>quent in eutrophic lakes. The species tolerate a wide<lb/> range of high temperatures, high pH and salinity<lb/> variations. The strong wind activity probably pre-<lb/>vents formation of Microcystis blooms in Lake<lb/> Xolotl~.n.<lb/></p> <p>From the point of view of its microflora, Lake<lb/> Xolotl~.n shares many common features with other<lb/> tropical water bodies which are also alkaline and<lb/> eutrophic. Lake George, for example, shares with<lb/> Lake Xolotl~n the dominance of Microcystis, Lyng-<lb/>bya, Anabaenopsis and various species of Nitzschia.<lb/> Lake Oloidien (Kenya), of moderate salinity (electrical<lb/> conductivity: 660 i~S.cm-1), has a phytoplankton<lb/> assemblage composed of 60-90% of bluegreen<lb/> algae. It is different from the less saline Lake<lb/> Naivasha (E.G. 285 p.S.cm -1) whose algal biomass is<lb/> dominated by diatoms and bluegreens <ref type="biblio">(KALFF and<lb/> WATSON, 1986)</ref>. Lake Valencia, with a ionic content<lb/> similar to Lake Xolotl,~n has a dominance of Micro-<lb/>cystis and Lyngbya.<lb/></p> <p>Another important fact is that a great Chlorop-<lb/>hyta diversity is common to all these lakes, although<lb/> their contribution to the total biomass is poor. Some<lb/> diatoms (Nitzschia, Gomphonema and Surirella),<lb/> considered to be benthic in temperate regions,<lb/> should be considered real planktonic in tropical lakes<lb/> and not accidentally removed from the sediment<lb/> <ref type="biblio">(ROUND, 1981)</ref>.</p> </text> </tei>