Author Institution: Department of Biology, University of AkronSHEPPE, WALTER. Observations on the Animal Life of Some Zambian Hot Springs. Ohio J. Sci. 75(1): 26, 1975

Sheppe, Walter

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26 PAUL H. FREYTAG Vol. 75OBSERVATIONS ON THE ANIMAL LIFE OF SOMEZAMBIAN HOT SPRINGS1WALTER SHEPPEDepartment of Biology, University of Akron, Akron, Ohio 44325SHEPPE, WALTER. Observations on theAnimal Life of Some Zambian Hot Springs.Ohio J. Sci. 75(1): 26, 1975.Three groups of hot springs had maximumtemperatures of 63° O88° C and total dis-solved solids of 450 ppm, 1600 ppm, and1800 ppm. Eight species of invertebrateswere found in one or more of thesesprings, at temperatures of 31° C-53° C.Much the most abundant animals were twospecies of ostracods (Eucypris spp.) foundin the more saline springs. Two specieswere ubiquitous and six were found in only-one spring each. Spring habitats werecomplex and variable and the occurrence ofanimals was closely correlated with thesedifferences.There are many hot springs in theZambezi basin of Zambia. The animallife and physico-chemical conditions inthree of these were observed during thecourse of other work in the area. Gwishoand Bwanda hot springs lie 3 km apartin Lochinvar National Park (16-00 S,27-15 E), at 1000 m above sea level.Manuscript received December 14, 1973(73-80).Fifty-mile Hot Springs (author's name)is on the Great East Road approximately80 km east of Lusaka (15-15 S, 29-00 E),at 1200 m above sea level. All threeconsist of numbers of small springsemerging in dense grass.METHODSGwisho Hot Springs was visited a number oftimes in 1967-68, and all three Springs werevisited in August-September, 1970 and Septem-ber, 1971. Water temperatures were mea-sured to ±0.5°C with a YSI Model 42SF Tele-thermometer with No. 418 probe. Dissolvedoxygen was measured by the Winkler method(azide modification), acidity was determinedwith pH paper, and water samples were col-lected for chemical analysis.Ostracods were plainly visible in the springs,and the shells of dead ostracods were visibleon dark bottom sediments; their presence andrelative abundance were noted on all visits.Other animals also were found in variousplaces. Animals and algae were collected in1970 and 1971.RESULTSMost of the springs are small roundedpools with water welling up from theNo. 1 ANIMAL LIFE OF ZIMBIAN HOT SPRINGSFIGURE 1. Spring 10 at Bwanda Hot Springs. The spring is filled with dead grass covered by analgal mat, except where water wells up in the center.bottom (fig. 1). They range from 20 cmto 2 m in diameter and from 4 cm to morethan 1 m in depth. Gas bubbles up frommost of the springs. They are drained bysmall outlet streams. Total dissolvedsolids at Gwisho were 1800 ppm, atBwanda 1600 ppm, and at Fifty-mile 450ppm, based on a single sample each. ThepH ranged from 4.0 to 5.5. Dissolvedoxygen ranged from 0 ppm to 4 ppm(seven determinations).Maximum temperatures in each springranged from 44.5°C to 78°C at Gwisho,from 51°C to 88°C at Bwanda, and from40°C to 63°C at Fifty-mile. There wasgreat variation within springs, with dif-ferences of as much as 5°C within hori-zontal distances of one or two centimeters.Such differences were caused either by thecomplex flow patterns in open water or bythe barrier effect of spring vegetation.Vertical temperature differences wereslight. Temperatures varied from timeto time by as much as 14°C, and droppedrapidly in the outlet streams.Most springs had a layer of dead grasson the bottom, usually overlain by analgal mat 2-3 mm thick or a layer of darkorganic sediment. The algal mats con-sisted of masses of filamentous blue-greenalgae, primarily Oscillatoria sp., imbeddedwith diatoms and in some springs manygreen sulfur bacteria (Microchloris sp.).Eight species of invertebrates were foundliving in the water of one or more springs(table 1). In addition, small gray spidersoften were seen running across the sur-face of the floating algal mats at all threesprings, and a water beetle (Dytiscidae)was found on a mat at Bwanda.Two species were found in all threesprings, the other species in only onespring each. The overall temperaturerange was similar at the three springs,from that of the ambient air to tempera-tures too hot for animal life. The re-stricted distribution of most of the ani-mals may have been caused by differencesin the chemical content of the water.Ostracods were found only in the moreheavily mineralized water at Gwisho andBwanda. Distribution within each springwas determined largely by temperature,and there is no evidence that pH or dis-solved oxygen limited the occurrence ofthe animals.28 WALTER SHEPPE Vol. 75TABLE 1Animals found in the springs, and the temperatures (°C) at which they were living.Oligochaeta, NaididaeNais sp.Ostracoda, CypridaeEucypris sp. AEucypris sp. BAnisopteraundet., nymphDipteraDasyhelea sp. (Ceratopogonidae), larvaeChironomidae, undet., larvaAcarinaNilotonia (s.s.) thermophila(Lundblad) (Anisitsiellidae)Trimalaconothrus sp. (Malaconothridae)No. of SpeciesBwanda31-524541.5-4944.54Gwisho31.5-5346.531.53Fifty-mile43.540.5-43.540.540-4543.55Dasyhelea was never common, but afew were found in algal mats at all threesprings. The temperature range was40.5°C to 49°C. A single chironomidlarva was living with Dasyhelea in analgal mat at 40.5°C, and a single dragonflynymph was living in an outlet stream at45°C.The mite Nilotonia was found in algalmats at three places at Fifty-mile andone at Bwanda, and in open water at oneplace at Gwisho. It was always at orjust below the surface, at 31.5°C to 45°C.The oligochaete Nais and the mite Tri-malaconothrus were found in an algal matin a small spring at Fifty-mile, living withDasyhelea and Nilotonia. The watertemperature was 43.5°C, and there wasno measurable dissolved oxygen.Ostracods were by far the most com-mon of the animals in the springs. Theirdistribution and abundance at Gwishoand Bwanda were influenced primarily bywater temperature, and they were foundonly at temperatures between 31°C and53°C. They were rarely found at theextreme temperatures, but were found atmost sites with temperatures of 36°C to50.5°C {Eucypris sp. A at 82% of 62sites, Eucypris sp. B at 90% of 21 sites).Populations were also more dense at theintermediate temperatures. Ostracodswere influenced by the rate of flow of thewater. Fast-flowing water had none, ex-cept a few carried along by the current,and the densest populations were in areasof still water.The springs are complex habitats, withmarked changes in temperature, rate offlow, and nature of substrate within adistance of a few millimeters. These dif-ferences were reflected in equally greatdifferences in the ostracod populations.Typically the water just emerging fromthe ground in the center of the spring wastoo hot for ostracods. Around the sidesof the spring and in the outlet streamsthere was a patchy distribution ofostracods, depending on temperatureand flow. Ostracods disappeared fromthe outlet streams as the temperaturedropped.The algal mat often acted as a mechani-cal barrier separating the hot water at thecenter of a spring from the cooler periph-eral water. In many springs there wereostracods in the water just outside thefloating edge of the mat but none in themuch hotter water lying over the mat.The water currents within a spring orstream were constantly shifting, and thelife of the ostracod depended on its re-maining in water at a suitable tem-perature. In one large pool, densepopulations were swimming rapidly inwater at 48°C, but as the current shiftedslightly those on the edge were con-tinually being swept into water at 61°C.These died almost immediately and wereswept away by the current.Ostracod populations varied from timeto time. There were great fluctuationsin a large pool at Gwisho in 1967-68.In September, 1967 there were manyNo. 1 ANIMAL LIFE OF ZAMBIAN HOT SPRINGS 29ostracods living at 48°C in the center ofthe pool. In 1970 the temperature therewas 10°C higher and there were noostracods, but in 1971 the temperaturehad fallen to 47°C and ostracods wereagain common. Populations in a fewother pools observed over a period oftime showed similar fluctuations.Acknowledgments. Determinations were madeby J. H. Olive, University of Akron (algae andbacteria); L. D. Delorme, Canada InlandWaters Branch (ostracods); K. R. Smith, OhioState University (Nais); \V. \V. Wirth (Dip-tera); D. R. Cook, Wayne State University(Nilotonia); and D. E. Johnston, Ohio StateUniversity (Trimalaconothrus). A. C. Pliod-zinskas did the chemical analyses. Olive,Delorme, and R. G. Wiegert of the Universityof Georgia read an earlier version of the manu-script. Peter Haas helped with some of thefield work. The Zambia Department of Wild-life, Fisheries and National Parks gave permis-sion to work at Loehinvar National Park. Thefield work was supported in part by NationalScience Foundation grant GB-16508.

Observations on the Animal Life of Some Zambian Hot Springs

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Observations on the Animal Life of Some Zambian Hot Springs

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