The submerged, floating, and emergent vascular flora of Lake East Okoboji, Dickenson County, Iowa, was surveyed by the senior author in the summer of 1961, with collections made at 21 stations. Emergent species and one hybrid, and 7 submerged or floating species were found. A comparison is made with a 1915 survey in which a very rich flora of about 18 emergents and 26 submerged or floating species was reported. Pollution by sewage and by agricultural fertilizers and other factors that may have caused changes in the vascular flora are discussed

Smith, S. Galen

Volker, Roger

University of Northern Iowa

Proceedings of the Iowa Academy of Science Volume 72 Annual Issue Article 14 1965 Changes in the Aquatic Vascular Flora of Lake East Okoboji in Historic Times Roger Volker Webster City Junior College S. Galen Smith Iowa State University Let us know how access to this document benefits you Copyright ©1965 Iowa Academy of Science, Inc. Follow this and additional works at: https://scholarworks.uni.edu/pias Recommended Citation Volker, Roger and Smith, S. Galen (1965) "Changes in the Aquatic Vascular Flora of Lake East Okoboji in Historic Times," Proceedings of the Iowa Academy of Science, 72(1), 65-72. Available at: https://scholarworks.uni.edu/pias/vol72/iss1/14 This Research is brought to you for free and open access by the Iowa Academy of Science at UNI ScholarWorks. It has been accepted for inclusion in Proceedings of the Iowa Academy of Science by an authorized editor of UNI ScholarWorks. For more information, please contact scholarworks@uni.edu. 1965] ALGAE OF LAKE AQUAHBI 65 blooms generally dissipate by the middle of November their presence results in a disagreeable odor that detracts from the recreational value of the lake. . ' Cladophora is abundant during summer and fall, usually at-tached to rocks along the northern and western shoreline and along the spillway. Extensive growths of Hydrodictyon reticulatum were found throughout late summer and fall along the spillway and in the shallow pools at station 2. This species occured in large masses containing colonies of various sizes. One species of Spirogyra was prevalent at stations 1, 2 and 3, especially in the shallow pools of the spillway. It was found at all other stations in lesser numbers. The six most common and widespread genera of algae found in the lake are Cladophora, Hydrodictyon, Spirogyra, Aphanizo-menon, Microcystis and Oscillatoria. Initial observations of some of these genera during the collecting period indicate considerable fluctuations in the numbers of individuals. Studies now 'linder-way will attempt to correlate the seasonal variation and distribu-tion of these and other species of algae with both the physical and chemical factors of the lake water. Literature Cited 1. Hennemuth, R. C. 1955. Iowa State University Jour. Sci. 30:119-137. 2. Prescott, G. W. 1951. Algae of the western great lakes area. Cranbrook Institute of Science. 3. Smith, G. M. 1950. Fresh-water algae of the United States. McGraw-Hill Book Co., Inc., New York. Changes in the Aquatic Vascular Flora of Lake East Okoboji in Historic Times RoGER VoLKER1 ANDS. GALEN SMrrn2 Abstract: The submerged, floating, and emergent vascular flora of Lake East Okoboji, Dickenson County, Iowa, was sur-veyed by the senior author in the summer of 1961, with col-lections made at 21 stations. Emergent species and one hybrid, and 7 submerged or floating species were found. A comparison is made with a 1915 survey in which a very rich flora of about 18 emergents and 26 submerged or floating species was re-ported. Pollution by sewage and by agricultural fertilizers and other factors that may have caused changes in the vascular flora are discussed. -----1 Webster City Junior College, Webster City, Iowa. • Iowa State University, Ames, Iowa. 1Volker and Smith: Changes in the Aquatic Vascular Flora of Lake East Okoboji in HisPublished by UNI ScholarWorks, 196566 IOWA ACADEMY OF SCIENCE [Vol. 72 INTRODUCTION This paper not only serves as a record of the aquatic flora of Lake East Okoboji in 1961, but also presents a comparison with the flora recorded in 1915 ( 6). Most of the work on the fauna and flora of the Okoboji lakes has been done at Lake West Okoboji by workers at the Iowa Lakeside Laboratory. Papers on the plants of the Lake West Okoboji were published early in this century by Ewers ( 5), Jones (7), and Wylie (17). In 1960 Bovbjerg and Ulmer (3) compared the present snail population in Lake West Okoboji to collections made earlier by Shimek ( 12). With the exceptions of the worrk of Weber ( 16) and Volker ( 14, 15) Lake East Okoboji has rarely been included in such studies. The two lakes, however, are quite different in many ways although they are connected by a narrow channel. Data obtained ail: Lake West Okoboji therefore cannot readily be applied to Lake East Okoboji. Lake West Okoboji is deep enough to form a thermocline and become stratified, whereas Lake East Okoboji is so shallow that it does not become stratified. Lake West Okoboji is a long, single body of water with several large bays, whereas Lake East Okoboji is actually a chain of three lakes connected by narrow, shallow channels. Lake East Okoboji always supports a dense bloom of blue-green algae (according to our observations prin-cipally Aphanizomenon) in summer, whereas the populations of blue-green algae seldom reach bloom proportions in Lake West Okoboji. Lake East Okoboji extends from the southeastern side of Lake West Okoboji east and northeast for two or three miles, then bends north for about four miles and almost meets the southern end of Big Spirit Lake. Big Spirit Lake empties into East Okoboji at Orleans through a small creek which was formeTly periodically dammed at its mouth by gravel deposited by ice and waves ( 6, p. 53), but the flow is now regulated by a weir. The outlet into the Gar Lakes at the south end of East Okoboji has been controlled by a small dam since before 1916. Lake East Okoboji is about rn miles wide at its widest point, about seven' miles long, and varies in depth from about 7 to 24 feet. It and the surrounding lake are apparently glacial in origin ( 4, 9). The water chemistry as reported by Bachman ( 1 ) and in moire detail by Volker ( 14) appears to be generally similar to other Iowa lakes in the Wisconsin glacial sheet region, including Lake West Okoboji. Most of the watershed is used intensively for agriculture. The town of Spirit Lake and many homes and cabins line much of the shore. 2Proceedings of the Iowa Academy of Science, Vol. 72 [1965], No. 1, Art. 14https://scholarworks.uni.edu/pias/vol72/iss1/141965] AQUATIC VASCULAR FLORA OF EAST OKOBOJI 67 THE 1915 SURVEY The flora of Lake East Okoboji and 14 other lakes in northern Iowa w:as reported by L. H. Pammel in 1916 as part III of the State Highway Commission report on Iowa Lake and Lake Beds. Field work was conducted by Pammel and L. W. Durrell in 1915. The abundance of each species for each lake was scored on a five-point scale from "very abundant and dominant" to '1ess frequent". Water-depth ranges for each species also were recorded. Collection stations at each lake unfortunately were not included in the report. Part II of the same report includes brief descriptions of the lakes. 13-----#Al\l\OWS LEGEND L&keSbore -------~ RockReeli. ---------~ RockPiiu-- ---------- llJtl. Wffd&d•---------·------ · ;'.~!::.=_ ~o~ds ...................................... .-_ ...... -R•ilrolld1 -~----------·----·~ F~re 1. Collecting stations used in the 1961 survey ·of aquatic vascular plants of Lake East Okoboji. 3Volker and Smith: Changes in the Aquatic Vascular Flora of Lake East Okoboji in HisPublished by UNI ScholarWorks, 196568 IOWA ACADEMY OF SCIENCE [Vol. 72 The vascular flora of Lake East Okoboji in 1915 was exception-ally rich and almost identical to that of Lake West Okoboji. It included at least 21'1 species of submerged or floating plants and 18 emergents, or a total of 44 species of acquatics (excluding several strictly wet-soil plants such a Caltha palustris listed by Pammel. The next richest aquatic flora repoded by Pammel consisted of only 16 species, recorded from Spirit Lake. The genus Potamogeton alone was represented at East Okoboji by all 13 species recorded in the entire 15-lake survey. Although most of the species were recorded as rather infrequent (?) ( 4-5 on the frequency scale), the submerged species Elodea ioensis (E. nuttallii), Myriophyllum spicatum and Ceratophyllum dem-ersum were reported to be very common in water 3 to 5 feet deep. Data from the 1915 survey is summarized and compared with data from the 1961 survey in T~bles 3 and 4. Table 1. Aquatic vascular plants found at each collection station in the 1961 suivey of Lake East Okoboji NARROWS Lemna minor Phalaris arundinacea Phragmites communis Sparganium eurycarpum Spirodela polyrhiza Typha angustifolia Typha X glauca Typha latifolia STATION 1 Ceratophyllum demersum Potamogeton foliosus Potamogeton pectinatus Potamogeton richardsonii Scirpus validus Zannichellia palustris STATION 2 Potamogeton · richardsonii. STATION 3 Scirpus validus STATION 4 Scirpus validus STATION 5 Potamogeton pectinatus Potamogeton richardsonii Scirpus sp. STATION 6 Potamogeton pectinatus STATION 7 Potamogeton pectinatus STATION 8 Phalarus arundinacea Scirpus validus STATION 9 Lemna minor Scirpus acutus Scirpus heterochaetus Scirpus validus Spirodela polyrhiza Typha angustifolia Typha X glauca Typha latifolia STATION 10 Scirpus acutus Scirpus validus STATION 11 Potamogeton pectinatus STATION 12 Sagittaria sp. STATION 13 Scirpus acutus Scirpus validus STATION 14 Scirpus fluviatilis STATION 15 Potamogeton pectinatus Scirpus acutus S cirpus flviatilis Scirpus validus Typha angustifolia Typha X glauca Typha latifolia STATION 16 Ceratophyllum demersum Potamogeton pectinatus Scirpus fluviatilis Typha angustifolia Typha latifolia STATION 17 Lemna minor S cirpus fluviatilis Scirpus validis Spar,ganium eurycarpum Typha angustifolia Ttjpha X glauca Typha latifolia STATION 18 Phalaris arundinacea Potamogeton pectinatus STATION 19 Potamogeton pectinatus STATION 20 Scirpus acutus Scirpus fluviatilis Scirpus validus STATION 21 Scirpus validus 4Proceedings of the Iowa Academy of Science, Vol. 72 [1965], No. 1, Art. 14https://scholarworks.uni.edu/pias/vol72/iss1/141965] AQUATIC VASCULAR FLORA OF EAST OKOBOJI 69 THE 1961 SURVEY In early August, 1961, the senior author made collections at each of 21 stations on Lake East Okoboji as indicated in Figure 1, using a small boat. We identified the plants from both dried and fresh material, retaining dried herbarium specimens as vouchers. The species collected at each station are listed in Table 1 and the cumulative species list is given in Table 2. Table 2. Cumulative species list of aquatic vascular plants found at Lake East Okoboji in 1961 Species Scirpus validus Potamogeton pectinatus Scirpus acutus S cirpus fluviatilis Typha angustifolia Typha latifolia Typha X glauca Lemna minor Phalaris arundinacea Number of stations where it occurs 13 9 7 5 5 5 4 3 3 Number of stations where it Species Potamogeton richardsonii Ceratophyllum demersum Spirodela polyrhiza Sparganium eurycarpum Phragmites communis Potamogeton foliosus Sagittaria spp. Scirpus heterochaetus Zanniehellia palustris occurs 3 2 2 2 1 1 1 1 1 DISCUSSION In the 46 years between 1915 and 1961, the total number of aquatic vascular species in Lake East Okoboji apparently has been reduced by about 60% from about 44 to 18 species. The re-duction in the submerged flora is especially striking (Table 3). Of 23 species recorded in 1915, only five were recorded in 1961. Among the species apparently eliminated from the flora are Elodea nuttallii and Myriophyllum spicatum, both of which were veiy common in 1915 and are among the commonest aquatics in Iowa today ( 2). In addition, Ceratophyllum demersum, also very common in Iowa, was recorded as the most abundant plant in 1915 but was found at only two stations in 1961. The only fairly common species in 1961 was Potamogeton pectinatus, which is remarkably tolerant of brackish, very hard, and turbid waters. In addition to containing a depauperate flora, Lake East Okoboji in 1961 was nearly barren in many places with shallow water apparently ideal for vascular plant growth. This condition contrasts markedly to that reported by MacBride in 1899: " .... the shallow waters are now rapidly filling up with vast quantities of aquatic vegetation." Records of emergent plants (Table 4) are more difficult to compare in the two surveys than are records of the submerged plants. This is partly due to difficulties in defining an aquatic, for 5Volker and Smith: Changes in the Aquatic Vascular Flora of Lake East Okoboji in HisPublished by UNI ScholarWorks, 196570 IOWA ACADEMY OF SCIENCE [Vol. 72 Table 3. Comparison of submerged or floating vascular plants reported from Lake East Okoboji in 1915 and 1961 Species Heteranthera dubia Potamogeton americanus (P. nodosus) Potamogeton amplifolius Potamogeton dimorphus (P. diversifolius) Potamogeton epihydrus Potamogeton friesii Potamogeton foliosus Potamogeton heterophyllus Potamogeton natans Potamogeton pectinatus Potamogeton praelongus Potamogeton pusillus Potamogeton richardsonii V alli.meria spiralis Ceratophyllum demersum Rannuculus aquatilis Myriophyllum spicatum Ridens beckii Lemnaminor Lemna trisulca Spirodela polyrhiza W olffia punctata Potamogeton zosteriformis Zannichellia palustris N aias fiexilis Elodea canadensis Elodea ioensis (E. nuttallii) Totals 0 EXPLANATION OF FREQCENCY NUMBERS: 1915 Freq. No. 1961 "Frequency 1915 1961 4 4 4 4 4-5 5 4 5 5 3-4 3 2 5 4 5 5 3-5 1 5 5 1-3 3 5 4 4 5 5 5 5 5 4 4-5 2-3 26 7 "Very abundant to dominant" 1 13 or more stations "Abundant" 2 10-12 stations "Common" 3 7-9 stations "Frequent" 4 4-6 stations "Less frequent'' 5 1-3 stations some emergent species recorded as aquatics in 1915 may have been interpreted as non-aquatic in 1961 and therefore not re-corded. Also, in contrast to the submerged aquatics, of which all of the species recorded in 1961 were also recorded in 1915, four emergent species and a hybrid recorded in 1961 were not recorded in 1915. Of these, the hybrid cattail T. X g"lauca ( T. angustifolia X "latifolia) was not recognized in North America until recently ( 13) and the round-stemmed bullrushes Scirpus acutus and S. heterochaetus hyb1idize with S. validus so that their distinctions are confused ( 8 and Smith, unpublished data) and all three could have been named S. validus in 1915. On the other hand, the observations of one of us (Smith, I.e.) also in-dicate that Typha angustifolia, T. X glauca and Scirpus acutus usually occupy disturbed habitats. It therefore is reasonable that these taxa were introduced since 1915 and survived because of man-caused disturbances of the ecology of the lake. Even allowing for problems in comparing the two surveys, the changes in the vegetation as herein described are striking 6Proceedings of the Iowa Academy of Science, Vol. 72 [1965], No. 1, Art. 14https://scholarworks.uni.edu/pias/vol72/iss1/141965] AQUATIC VASCULAR FLORA OF EAST OKOBOJI 71 Table 4. Comparison of emergent aquatic vascular plants reported from Lake East Okobojie in 1915 and 1961 Species Typha latifolia Typha angustifolia Typha X glauca Sparganium arnericanum Sparganium eurycarpum Sparganium simplex Sagittaria latifolia Echinodoms cordifolius Alisma plantago-aquatica Phragmites communis Glyceria nervata Glyceria grandis Phalaris arundinacea Eleocharis acicularis Eleocharis ovata Eleocharis palustris Scirpus fiuviatilis Sirpus validus Scirpus acutus Scirpus heterochaetus Iris versicolor Radicula palustris Bidens cernua Totals " See footnote in Table 3 for explanation. "Frequency 1915 1961 4 4 4 3 4 3-4 5 4-5 4-5 4-5 4-5 3-4 5 4 4-5 3-4 4 4 4-5 18 4 4 5 5 5 5 4 1 3 5 11 and not likely to be due to chance alone. The responsible fac-tors appear to us to be related to the increasingly intense human use of the land and water of the Lake East Okoboji region as follows: 1. Increased nutrient content of the water of the lake, re-sulting from (a) increased use of agricultural fertilizers on the land and ( b) increased sewage effiuent from the growing human population. 2. Increased blooms of planktonic algae, principally blue-greens, probably due to the increased nuhient concentrations. 3. Increased siltation due to more intense cultivation of the land. 4. Use of copper sulfate and other chemicals to control algal blooms ( 10, 11) and aquatic vascular plants. 5. Changes in the amount and timing of fluctuations of water level and currents due to the construction of a wier at the inlet and a dam at the outlet. The actual elimination of many of the submerged vascular plants from Lake East Okoboji may have been accomplished by shading due to algal blooms or silt, by toxins produced by the algae, by low oxygen content due to decomposing algal masses, or by other, less apparent factors such as the copper sulfate used in control of algae. Blooms of blue-green algae are so massive and frequent on Lake East Okoboji that copper sulfate has been 7Volker and Smith: Changes in the Aquatic Vascular Flora of Lake East Okoboji in HisPublished by UNI ScholarWorks, 196572 IOWA ACADEMY OF SCIENCE [Vol. 72 applied to the lake at the extremely high rate of about 25 pounds per acre per season over the past four seasons ( 11), and it is difficult to escape the conclusion the algal blooms somehow are responsible for changes in the vascular flora. Our data on the vascular flora of Lake East Okoboji are strikingly parallel to published data on gastropods. Bovbjerg and Ulmer ( 3) and Shimek ( 12) reported a marked reduction in both numbers of individuals and species of gastropods in Lake West Okoboji between about 1915 and 1935 and related this change to pollution by sewage effiuents. The obvious common factors in the two lakes are increased sewage effiuents and per-haps agricultural fertilizers. It therefore is reasonable to assl).me that these forms of pollution are the major causes of the ob-served changes in the vegetation of Lake East Okoboji. The present flora of Little Miller's Bay on Lake West Okoboji how-ever is almost identical to the flora described in 1915. Pollution of Lake East Okoboji is therefore evidently much more severe than Lake West Okoboji. Literature Cited 1. Bachman, R. W. 1964. Mimeo. Conference on Limnology in Iowa, Iowa State Univ., Ames. 2. Beal, Ernest 0. and Paul H. Monson. 1954. State Univ. Iowa Stud. Nat. Hist. 19(5):1-95. 3. Bovbjerg, B. V. and Uhner, M. J. 1960. Proc. Iowa Acad. Sci. 67:569-577. 4. Cannan, E. J. 1915. Iowa Geol. Surv. (Reports and Papers) 26:233-456. 5. Ewers, A. F. 1915. Okoboji Protective Assoc. Bull. 11: 13-18. 6. Iowa State Highway Commission. 1916. Iowa Lakes and Lake Beds. State of Iowa, Des Moines, Iowa. (Issued March 1917.) 7. Jones, E. N. 1925. Proc. Iowa Acad. Sci. 32:181-188. 8. Koyama, Tetsuo. 1962. Canad. Jour. Bot. 40:913-937. 9. MacBride, T. H. 1899. Iowa Geol. Surv. (Reports and Papers) 10:189-239. 10. Moen, T. 1962. 1962-1963. Iowa State Cons. Comm. Quarterly Biol. Reports 15 ( 4) : 38-40. 11. Moen, T. 1964. Mimeo. Conference on Limnology in Iowa, Iowa State Univ., Ames. 12. Shimek, B. 1935. Nautilus 48 ( 4): 109-111. 13. Smith, Galen. 1962. (Abstr.) Amer. Jour. Bot. 49:678. 14. Volker, R. P. 1962. Proc. Iowa Acad. Sci. 69:99-107. 15. -------. 1963. Unpublished M.S. Thesis. Iowa State University, Ames, Iowa. 16. Weber, C. I. 1958. Proc. Iowa Acad. Sci. 65:166-173. 17. Wylie, R.R. 1911. Okoboji Protective Assoc. Bull. 7:10-20. 18. -------. 1920. Proc. Iowa Acad. Sci. 27:91-97. 8Proceedings of the Iowa Academy of Science, Vol. 72 [1965], No. 1, Art. 14https://scholarworks.uni.edu/pias/vol72/iss1/14

Changes in the Aquatic Vascular Flora of Lake East Okoboji in Historic Times

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Changes in the Aquatic Vascular Flora of Lake East Okoboji in Historic Times

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