Zooplankton abundance, species composition and ecology of tropical high-mountain crater lake Wonchi, Ethiopia
<p>The highlands of Ethiopia represent some of the remnants of undisturbed aquatic ecosystems; they are however highly threatened by significant socio–economic developments and associated anthropogenic impacts. Lake Wonchi is one of the few remaining fairly pristine high–mountain crater lakes...
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| Format: | Article |
| Language: | English |
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PAGEPress Publications
2014-11-01
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| Series: | Journal of Limnology |
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| Online Access: | http://www.jlimnol.it/index.php/jlimnol/article/view/986 |
| _version_ | 1818216097559609344 |
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| author | Fasil Degefu Michael Schagerl |
| author_facet | Fasil Degefu Michael Schagerl |
| author_sort | Fasil Degefu |
| collection | DOAJ |
| description | <p>The highlands of Ethiopia represent some of the remnants of undisturbed aquatic ecosystems; they are however highly threatened by significant socio–economic developments and associated anthropogenic impacts. Lake Wonchi is one of the few remaining fairly pristine high–mountain crater lakes in the central highlands and has never been investigated in detail. We present a first study on zooplankton taxa composition, abundance and biomass conducted over more than one year including the underlying environmental drivers. The lake is basic (pH 7.9-8.9), dilute (specific conductivity 185-245 µS cm<sup>-1</sup>) and oligotrophic with mean trophic status index of 36. The zooplankton community composition showed low species richness comprising a total of fourteen taxa with six cladocerans, one copepod and seven rotifers. Simpson´s index of diversity with values between 0.6 and 0.8 pointed towards a homogenous taxa occurrence within the single sample units. The overall mean (±SD) standing biomass of zooplankton was 62.02±25.76 mg dry mass m<sup>-3</sup>,which is low compared to other highland and rift valley lakes in Ethiopia. Cyclopoid copepods, in particular <em>Thermocyclops ethiopiensis</em> were the most abundant group and contributed 50% to the total zooplankton abundance followed by cladocerans (38%) and rotifers (12%). Non-metric multi-dimensional scaling resulted in a 3-dimensional model, which revealed similar community composition on successive sampling dates except in December/January and May. Temperature, alkalinity, conductivity and nitrate-N had significant influence on this seasonal pattern. A weak, but significant positive correlation (r=0.482, N=20, P=0.037) between Chlorophyll <em>a</em> and zooplankton biomass mirrors a bottom-up effect of phytoplankton biomass on zooplankton dynamics. The zooplankton of Lake Wonchi displayed some degree of segregation along the epi– and metalimnion during this study, but diel vertical migration was not observed. The results show that fish predation is not the key factor in structuring the vertical distribution of zooplankton in Lake Wonchi.</p> |
| first_indexed | 2024-12-12T06:46:33Z |
| format | Article |
| id | doaj.art-3603c97003d74d68acb724b1bb44d9c2 |
| institution | Directory Open Access Journal |
| issn | 1129-5767 1723-8633 |
| language | English |
| last_indexed | 2024-12-12T06:46:33Z |
| publishDate | 2014-11-01 |
| publisher | PAGEPress Publications |
| record_format | Article |
| series | Journal of Limnology |
| spelling | doaj.art-3603c97003d74d68acb724b1bb44d9c22022-12-22T00:34:11ZengPAGEPress PublicationsJournal of Limnology1129-57671723-86332014-11-0174210.4081/jlimnol.2014.986696Zooplankton abundance, species composition and ecology of tropical high-mountain crater lake Wonchi, EthiopiaFasil Degefu0Michael Schagerl1National Fisheries and Other Living Aquatic Resources Research CenterUniversity of Vienna<p>The highlands of Ethiopia represent some of the remnants of undisturbed aquatic ecosystems; they are however highly threatened by significant socio–economic developments and associated anthropogenic impacts. Lake Wonchi is one of the few remaining fairly pristine high–mountain crater lakes in the central highlands and has never been investigated in detail. We present a first study on zooplankton taxa composition, abundance and biomass conducted over more than one year including the underlying environmental drivers. The lake is basic (pH 7.9-8.9), dilute (specific conductivity 185-245 µS cm<sup>-1</sup>) and oligotrophic with mean trophic status index of 36. The zooplankton community composition showed low species richness comprising a total of fourteen taxa with six cladocerans, one copepod and seven rotifers. Simpson´s index of diversity with values between 0.6 and 0.8 pointed towards a homogenous taxa occurrence within the single sample units. The overall mean (±SD) standing biomass of zooplankton was 62.02±25.76 mg dry mass m<sup>-3</sup>,which is low compared to other highland and rift valley lakes in Ethiopia. Cyclopoid copepods, in particular <em>Thermocyclops ethiopiensis</em> were the most abundant group and contributed 50% to the total zooplankton abundance followed by cladocerans (38%) and rotifers (12%). Non-metric multi-dimensional scaling resulted in a 3-dimensional model, which revealed similar community composition on successive sampling dates except in December/January and May. Temperature, alkalinity, conductivity and nitrate-N had significant influence on this seasonal pattern. A weak, but significant positive correlation (r=0.482, N=20, P=0.037) between Chlorophyll <em>a</em> and zooplankton biomass mirrors a bottom-up effect of phytoplankton biomass on zooplankton dynamics. The zooplankton of Lake Wonchi displayed some degree of segregation along the epi– and metalimnion during this study, but diel vertical migration was not observed. The results show that fish predation is not the key factor in structuring the vertical distribution of zooplankton in Lake Wonchi.</p>http://www.jlimnol.it/index.php/jlimnol/article/view/986Lake Wonchizooplanktoncompetitionvertical distributiontrophic classification. |
| spellingShingle | Fasil Degefu Michael Schagerl Zooplankton abundance, species composition and ecology of tropical high-mountain crater lake Wonchi, Ethiopia Journal of Limnology Lake Wonchi zooplankton competition vertical distribution trophic classification. |
| title | Zooplankton abundance, species composition and ecology of tropical high-mountain crater lake Wonchi, Ethiopia |
| title_full | Zooplankton abundance, species composition and ecology of tropical high-mountain crater lake Wonchi, Ethiopia |
| title_fullStr | Zooplankton abundance, species composition and ecology of tropical high-mountain crater lake Wonchi, Ethiopia |
| title_full_unstemmed | Zooplankton abundance, species composition and ecology of tropical high-mountain crater lake Wonchi, Ethiopia |
| title_short | Zooplankton abundance, species composition and ecology of tropical high-mountain crater lake Wonchi, Ethiopia |
| title_sort | zooplankton abundance species composition and ecology of tropical high mountain crater lake wonchi ethiopia |
| topic | Lake Wonchi zooplankton competition vertical distribution trophic classification. |
| url | http://www.jlimnol.it/index.php/jlimnol/article/view/986 |
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