Observations on the relations of some physico-chemical features and DVM of Paradiaptomus africanus in Lakes Bishoftu-Guda and Hora-Arsedi, Bishoftu, Ethiopia

Abstract

Bishoftu-Guda and Hora-Arsedi are two crater lakes found in close proximity with each other in a locality known as Bishoftu, 50 km south of Addis Ababa, capital city of Ethiopia. The main objective of this study was to measure some physico-chemical features and discuss their relations with the dial vertical migration (DVM) behavior of Paradiaptomus africanus, the dominant macrozooplankton in both lakes. By depth measurements of dissolved oxygen and temperature showed that there is persistent stratification in these lakes. Secchi depth was shallow and the water chemistry as shown from conductivity and chemical analysis were comparable between the two lakes. These data were compared with previous reports to bring out the overall limnological scenario of the two lakes. Then, the relations of these data to the DVM of P. africanus in both lakes were discussed. It was found out that DVM of P. africanus occurred in Lakes Bishoftu-Guda and Hora-Arsedi mostly within a range of about 3 m very likely for two reasons, namely avoidance of solar radiation and ultimately vertebrate visual predation. However, the depth of DVM of P. africanus was found to be very shallow probably due to high water turbidity that provided this calanoid sufficient refuge by daylight from both dangers, while at the same time P. africanus remained in warm and oxygen-rich waters. Temperature was not much of a factor affecting DVM as it remained above 19 1C at all depths. As this study was conducted over limited time frames, seasonal studies regarding changes in physico-chemical parameters, plankton, vertebrate predators and human interference were recommended so that the information so gathered could be used in the management of the study lakes.

Physicochemistry and zooplankton of two karstic sinkholes in the Yucatan Peninsula, Mexico

“…The limnetic richness recorded here was similar to records of other karstic lakes from different latitudes (Armengol and Miracle, 1999;Lemma, 2009). The zooplankton species in the surveyed lakes appear to occupy separate niches in the spatial and temporal scales analysed.…”

Nitzschia fenestralis: A new diatom species abundant in the Holocene sediments of an eastern African crater lake

“…Characteristic of many crater lakes, Lake Babogaya has steep slopes with a very small catchment area and no inflowing rivers or streams. Multiple researchers have conducted comprehensive investigations into the limnology of these crater lakes (Baxter et al 1965;Wood et al 1976Wood et al , 1984Wood & Talling 1988;Lamb et al 2002;Lemma 2009), and as a result the hydrochemistry and seasonal variations of the relatively fresh (ca. 750-900 µs.cm -1 ), alkaline (8.7-9.2 pH) Lake Babogaya are well understood (Table 1).…”

“…Surface water in 1998, fromLamb et al (2002).2 Surface waters to 50 m depth in 2001, fromLemma (2009).…”

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