HYOROBIOL. 8ULL. 25(2), 117-120 (1991)

SPECIES COMPOSITION OF PHYTOBENTHOS IN THE LITTORAL OF LAKE XOLOTI,.AN (MANAGUA)

MARTHA GUERRERO and LESBIA RODRIGUEZ

KEYWORDS: Phytobenthos; littoral zone; tropical lake

ABSTRACT

The species composition of the phytobenthos in the littoral of Lake Xolotl~n (Managua) was determined. Sampling was carried out in November 1987 (end of the rainy season) and in July-August 1988 (rainy season). Sixty-eight taxa were identified; viz. 47 Bacillariophyceae, 13 Cyanophyta and 8 Chlorophyta. The presence of diatom species like Navicula veneta, Nitzschia amphibia and Nitzschia paler indicate eutrophic conditions, high ionic concentration, alkaline conditions and intense organic pollution.

INTRODUCTION

All kind of materials beneath the water surface (sand, stones, macrophytes, diverse objects) serve as substratum for micro-organisms and they are usually covered with a dense film of sessile algae and animals. Among the algae, many species of diatoms use to be present and these are commonly used as indicators of water quality.

Inventory studies of freshwater algae from Nicaragua are scarce and they are totally lacking on phytobenthos. This is the first contribution to the knowledge of benthic algae in Nicaraguan fresh waters. Most attention has been given to diatoms because of their usefulness in water quality as- sessment.

MATERIALS AND METHODS

Phytobenthos samples were collected in No- vember 1987 on rocks, stones, fine sand and macrophytes. The eulittoral and the upper infralittoral zone (WETZEL, 1981) were sampled. Cyanophytes and chlorophytes were identified before preservation with formalin (4%). Diatoms were separated from

inorganic particles by sedimentation and treated with sulphuric acid, potassium dichromate and hydrogen peroxide to remove their organic content (BARBER and HAWORTR, 1981). Afterwards, they were included in Naphrax for permanent mountings.

All diatom species were counted and their relative abundance on each sampling point was calculated. Those species with a relative abundance (Table 1 and 2) of 5% or more were considered as

Table 1. Relative abundance of diatoms in the most polluted zone.

Species November 1987 July-August 1988 Nitzschia amphibia 0.0 38.0 Achnanthes minutissima 0.0 2.6 Nitzschia pa/ea 43.3 5.5 Gomphonema affine 3.3 16.8 Rhopalodia gibba 0.0 0.0 Navicula veneta 0.0 1.0 Nitzschia claus# 0.0 1.0 Navicula goeppertiana 35.6 0.0 Nitzschia acicularis 17.7 0.0 Achnanthes exigua 0.0 4.0 Nitzschia sp. 0.0 20.5 Amphora coffeaeformis 0.0 8.7 Nitzschia tryblionella 0.0 0.0 Fragilaria brevistriata 0.0 0.0

117

118 M. GUERRERO and L RODRIGUEZ

Table 2. Relative abundance of diatoms in the less polluted zone.

Species November 1987 July-August 1988

Nitzschia amphibia 3.2 9.1 Achnanthes minutissima 36.8 3.3 Nitzscltia palea 7.9 20.3 Gomphonema a#ine 13.8 25.4 Rhopalodia gibba 14.1 7.0 Navicula veneta 4.7 2.0 Nitzschia clausii 0.0 0.3 Navicula goeppertiana 0.0 0.0 Nitzschia acicularis 3.3 0.0 Achnanthes exigua 0.0 0.0 Nitzschia sp. 0.0 1.5 Amphora coffeaeformis 2.1 10.6 Nitzschia tryblionella 1.0 1.8 Fragilaria brevistriata 9.1 0.0

Table 3. Phytobenthos species list. * Phytop/ankton.

gacilladophyceae

Achnanthes minutissima KiJtzing Achnanthes exigua Gmnow Amphora coffeaeformis, (Agardh) KOtzing Anomoeoneis sphaerophora (Ehrenberg) Pfitzer *Cyc/otella meneghiniana KOtzing *Cyc/ote//a kiJtzingiana Thwaites Cymbe//a sp. Oiplo'neis sp. Epithemia sp, Fragi/am construens (Ehrenberg) Grunow Fragi/aria brevistriata Grunow (?) Fragilaria pinnata Ehrenberg "Fragilaria pinnata var. trigona (erun & Herib.) Hust Fragl7aria sp. Gomphonema affine KiJtzing Gomphonema parvulum KOtzing Gyrosigma acuminatum (KiJtzing) Rabenhorst Mastogloia smithii Thwaites Melosira granulata (Ehrenberg) Rails Melosira sp. Navicula capitata var. hungarica (Grunow) ross Navicula cryptocephala KQtzing Navicula cuspidata (K~tzing) Navicula eidrigiana Carter (?) tVavicula elegans W. Smith Navicula goeppertiana (Bleisch) H.L. Smith Navicula minima Grunow (?) Navicula pupula KQtzing Navicula pygmaea KOtzing Navicula seminulum Grunow Navicula veneta KQtzing Navicula sp. *Nitzschia acicularis W. Smith Nitzschia angusteforaminata nov. spec. (?) Nitzschia amphibia Grunow Nitzschia clausii Hantzsch N#zschia dissipata (KOtzing) Grunow Ni~zschia fonticola Grunow (?) Nitzschia microcepha/a Grunow N#zschia pa/ea (KQtzing) W. Smith

Nitzschia tryblionella Hantzsch Nitzschia sp. 1 Nitzschia sp. 2 Nitzschia sp. Rhopa/odia gibba (Ehrenberg) O. MOil Rhopa/odia paral/e/a (Grunow) O. MOll var. parallela Stephanodiscus sp. Surire//a sp. Synedra ulna Ehrenberg Thalassiosira sp.

Cyanophyta

*Aphanocapsa sp. Calothrix parietina Thwel Calothrix sp.

�9 *Chroococcus limneticus Lemm. Homoethrix sp. Gloetrichia sp. *Lyngbya contorta Lemm. Leptochaete sp. Nostoc sp. Oscillatoria brevis (KOtz) Gore. Phormidium sp. Pleurocapsa minor Hansg. Stigonema sp.

Chlorophyta

Cladophora sp. Cosmarium sp. * Kirchneriella sp. Oedogonium sp. *Oocystis sp. *Scenedesmus sp. Spyrogyra sp. Tribonema sp.

dominant for this point, those with a relative abun- dance over 30% were predominant and species present in 70% of all the sampling sites were considered most dominant. Of nearly all species photographs or drawings were made. These can be obtained from the authors.

RESULTS AND DISCUSSION

Sixty-eight species were identified in the phyto- benthos of Lake Managua (Table 3). Navicula and Nitzschia species predominated. The majority of the diatom species in this littoral zone preferred eutro- phic waters (N. veneta), or high ionic concentrations ( Gomphonema affine, Navicula pygmaea) and were also tolerant to alkaline conditions (A.exigua, A. coffeaeformis, F. brevistriata, G. affine). Others were common because of their tolerance to organic pollution. (Navicula goeppertiana, N. veneta, N. pygmaea, Nitzschia palea, IV. clausii, etc.). Nitzschia palea is a good indicator of pollution as stated by

Phytobenthos species composition 119

Table 4. Comparison of the algal composition of lake Xolotl~n with other waterbodies. (Modification of the table in DOR, 1974).

Total number Author, waterbody, location Chlorophyta % Diatoms % Cyanophyta % of species

Lake Xolotl~tn, Managua Nicaragua, 1987 8 11.8 47 69.1 13 19.1 68 Aswan Reservoir Egypt Abdin, G. (1950) (benthos) 7 24 16 55 6 20 29 Lake Tiberias (phytobenthos) Dor, I. (1971) 12 13 25 27 54 58 94

CHOLNOKY (1968) and LANGE-BERTALOT (1979). This last author considered N. palea as one of the most tolerant species to pollution. In fact, the highest relative abundance of this diatom in Lake Xolotl~n was observed in the most polluted zone.. Nitzschia is probably more tolerant to organic pollution than Cyclotella meneghiniana (PALMER, 1975). A high variation in population density of these two diatoms in Lake Xolotl~n suggests a significant organic pollution.

In River Moruya (Australia), the predominant genera were Navicula, Nitzschia and Achnanthes (POTTER, CANNON and MOORE, 1975). The same genera had also a high frequency at other latitudes (DOUGLAS, 1958; PEABODY and WRITTON, 1968; MOORE, 1972; ROUND, 1970). Regardless of the locality there is a frequent association of Nitzschia and Navicula with eutrophic conditions (HANCOCK, 1973; 1979).

Another abundant alga in the littoral of Lake Xolotl:~n was Achnanthes exigua. It was more fre- quent in those localities of the lake that showed a moderate pollution. At the discharge zone of the geothermic plant, Nitzschia amphibia showed a very high relative abundance (40%) over the year. This cosmopolitan species, typically reaches high po- pulation densities when pollution is not extreme (LANGE-BERTALOT, 1977).

The percentage of diatoms among Lake Xolot- I,~n phytobenthos seems to be higher (69%), than for

lakes at other latitudes (Table 4). Volcanic influence, enhancing silicium content, may favour the develop- ment and diversification of diatoms.

CONCLUSIONS

The phytobenthos of Lake Managua seems to be dominated in numbers and diversity by the diatoms (69% of all species). Cy~nophyta and Chlorophyta represent 12% and 19%, respectively, of the total. More detailed studies should confirm this preliminary conclusion.

The dominant species, were Nitzschia palea and Navicula goeppertiana, suggesting intense pollution and eutrophic conditions, especially in those loca- lities where higher relative densities were found.

ACKNOWLEDGMENTS

We express our appreciation to Dr. Manfred Pum for assistance with sample collection, labo- ratory analyses and species identification and Lic. Ninoska Chow for helping in the photographic part (SEM) of this work. The Unidad de Microscopia Etectr6nica (Universidad de Costa Rica) provided all facilities for the SEM work.

REFERENCES

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Publication No. 44. England, p. 105-109. CHOLNOLKY, B.J., 1968. Die Oekologie der Diatomeen in 8innengew~ssern. Cramer, Braunschweig, 699 pp. DOUGLAS, B., 1958. The ecology of attached diatoms and other algae in a small, stony creek. J. Ecol., 46: 295-322. DOR, I., 1974. Considerations about the composition of benthic algal flora in Lake Kinneret. Hydrobiologia. 44: 255-264. GIFFEN, MH., 1966. Contributions to the diatom flora of South Africa. II. Diatoms from the Hog's Back region of the Amatola Mountains, East

Cape Province, South Nrica. Nova Hedwigia, 21: 123-160. HANCOCK, F.D., 1973. The ecology of the Diatoms of the Klip River, Southern Transvaal. Hydrobiologia, 42: 243-284. HANCOCK, F.D., 1979. Diatom associations and succession in Lake Kariba, South Central Africa. Hydrobiologia, 67: 33-50.

120 M. GUERRERO and L. RODRIGUEZ

KARI M, A.G.A., 1975. Studies on the freshwater algae o~ the Sudan II. The Distribution of the Bacillariophyceae of Wadi Galol, Jebel Marra. Hydrobiologia, 47: 31-42.

LANGE-BERTALOT, H., 1977. Eine Revision zur Taxonomie der Nitzschiae/anceo/atae Grunow. Die 'Klassischen' bis 1930 beschriebenen SOsswasserarten Europas. Nova Hedwigia, 28: 253-307.

LANGE-BERTALOT, H., 1979. Pollution tolerance of diatoms as a criterion for water quality estimation. Nova Redwigia, 64: 285-304. MOORE, J.W., 1972. Composition and structure of algal communities in a tributary stream of Lake Ontario. Can. J. Bot., 50:1163-1874. PALMER, C.M., 1975. Algae. In: Perrish, F.K., Ed., Keys to water quality indicative organisms of the Southern United States. US Environmental

Protection Agency, Cincinnati, OH. PEABODY, A.J. and B.A. WI-IITTON, 1988. Algae of the River Wear. 1. Diatoms. Naturalist, 906: 89-96. POTIER, I.C., D. CANNON and J.W. MOORE, 1975. The ecology of algae in the Moruya River, Australia. Hydrobiologia, 47: 415-430, ROUND, F.E., 1970. The Biology of the Algae, Edward Arnold, London. WETZEL, R.G., 1981. Limnologia. Ediciones Omega, S.A., Barcelona, p. 320-377.

Address of the authors:

CENTRO PARA LA INVESTIGACION EN RECURSOS ACUATICOS DE NICARAGUA, Apartado Postal 4598, Managua, Nicaragua.