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Deal, Robert

Kantz, John

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Algal Populations ♦  77IntroductionMonitoring over the past four years in the two createdwetlands provides evidence of ongoing shifts in thepopulations of the macroalgal dominants. While bothplankton and algal mat samples have been monitored, themat (or “clump” samples) are consistently the mostproductive in terms of number and frequency of all formsof algae. Annually, the most visible changes in themacroalgae of the wetlands are fluctuations in thepopulations of Hydrodictyon, Cladophora, Rhizocloniumand Spirogyra. These fluctuations take place month-to-month and in different parts (inlet, mid-basin, and outlet) ofeach wetland.Although several genera appear either consistently butat low population levels, or sporadically at higher densitylevels, the four genera (above) appear to be the majorcompetitors and the most important in providing suitablehabitat for the numerous genera of microalgae that havebeen identified.MethodsCollections were taken by a systematic sampling offloating mat and plankton tows in the inlet, mid-basin andoutlet areas of each wetland. Mat samples were a collectionof different “clumps” within each basin area. PlanktonComparison of macroalgal dominants in the two Olentangy Riverexperimental wetland basinsJohn Kantz, Jr. and Robert DealDepartment of Natural SciencesShawnee State University, Portsmouth, Ohiosamples were the compilation of three tows within eachbasin area. The number of months sampled have varied,from as few as four to as many as eight in a year.Each sample was surveyed by preparing three slides.Mat samples were prepared using forceps to collect filamentsthat appeared to be different in color and texture in order toidentify as many different genera as possible. Planktonsamples were swirled and each sample was taken from thevortex. The sample under each 22 mm2 coverslip wassystematically surveyed at 100x magnification in a back-and-forth pattern; greater magnification was used as neededfor specific identification. As a genus was identified, it wasrecorded on a spreadsheet.Results and discussionOne of the primary goals of all wetland research at theOlentangy Research Park is to establish physical andbiological trends of the experimental wetlands (Mitsch etal., 1998). Our specific goal of the algal survey is to identifyas many of the algae in the sample as possible. Thefollowing data are based on whether a genus was identifiedin a given sample from one of the following six sampleareas: Wetland 1-inlet, mid-basin, outlet and Wetland 2-inlet, mid-basin, outlet. Present/absent criteria were used toestablish the annual frequency percentages  (Fig. 1)  and theFigure 1. Annual frequency of macroalgal dominants in Wetland 1 (black squares) and 2 (open squares).Hydrodictyon0102030405060708090100annual frequency (%)0102030405060708090100Cladophora1995 1996 1997 19980102030405060708090100Rhizoclonium102030405060708090100Spirogyra01995 1996 1997 1998annual frequency (%)78  ♦  The Olentangy River Wetland Research Parkcumulative average frequency percentages (Fig. 2) forCladophora, Hydrodictyon, Rhizoclonium, and Spirogyra.Specific data to note include that in 1995 all four generahad higher sampling frequency in Wetland 2 than inWetland 1. Also, of the four genera (above), Spirogyra wasthe only one to appear in 90% or more of all samples fromWetland 2 each of the four years.The shifts in sampling frequencies of Rhizoclonium andCladophora over the four-year period provide an interestingcomparison. While both genera exhibited higher samplingfrequency in Wetland 2 than in Wetland 1 during 1995,their frequencies in both wetlands were quite similar in1996 (Fig. 1). However, through 1997 and 1998, theirsampling frequencies flip-flop as almost mirror oppositesyear-to-year. The data suggest that Rhizoclonium wasmore abundant in Wetland 1 during 1997, while Cladophorawas more abundant in Wetland 2; in 1998 the oppositeoccurred. The shifting population dynamics of these two1995 1995-1996 1995-1997 1995-1998Wetland 10102030405060708090100Hydrodictyon Rhizoclonium Cladophora SpirogyraCumulative average frequencies0102030405060708090100Hydrodictyon Rhizoclonium Cladophora SpirogyraCumulative average frequenciesWetland 2Figure 2. Four-year cumulative average frequencies in ORWRP Wetlands 1 and 2.genera are especially interesting in light of the fact that theyare closely related coenocytic algae.While the annual frequency percentage data suggestshifting population densities of these genera between thetwo wetlands from year to year, the cumulative averagefrequency percentages (Fig. 2) suggest that all four generahave been more abundant in Wetland 2 than Wetland 1.This analysis suggests shifting and inconsistent populationdensities for three of the genera (Cladophora, Hydrodictyon,and Rhizoclonium); for Spirogyra it supports visualobservations that this algae is becoming more abundant inWetland 2 and less abundant in Wetland 1.ReferencesMitsch, W.J., X. Wu, R.W. Nairn, P.E. Weihe, N. Wang,R. Deal, and C.E. Boucher. 1998. Creating andrestoring wetlands. BioScience 48: 1019-1030.

Comparison of macroalgal dominants in the two Olentangy River
experimental wetland basins

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Comparison of macroalgal dominants in the two Olentangy River experimental wetland basins

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