Las invasiones bárbaras... (Una lectura irreverent)

Abstract not availabl

Production algale et consommation par le Tilapia, Oreochromis niloticus L., au Lac Muhazi (Rwanda). Résumé de thèse de doctorat

Algal production and consumption by the Tilapia Oreochromis niloticus L., in Lake Muhazi (Rwanda). The article describes shortly the objectives of a Food Early Warning System (FEWS) project, as well as its organisation. The specifie case of Somalia, where the project had to evolve in increasingly difficult situations, and the solutions used so as to preserve the output, are described

Pengembangan multimedia interaktif berbasis autoplay untuk meningkatkan hasil belajar siswa pada mata pelajaran IPS materi memelihara lingkungan kelas III MI Yaspuri Malang

INDONESIA: Pengembangan media ajar AutoPlay IPS merupakan salah satu sarana guna membantu memahamkan siswa dalam pembelajaran. Melalui media ajar, diharapkan siswa dapat termotivasi dan menumbuhkan keterampilan siswa, serta sebagai upaya membiasakan siswa bekerja keras untuk memperoleh pengetahuan. Media ajar yang dapat mendukung proses pembelajaran IPS adalah media ajar berbasis AutoPlay materi memelihara lingkungan. Materi ini menjelaskan tentang memelihara lingkungan dan cara merawatnya dalam kehidupan sehari-hari. Tujuan penelitian ini adalah mengembangkan media ajar berbasis AutoPlay materi memelihara lingkungan dengan objek penelitian siswa kelas III MI Yaspuri Malang. Kemudian dengan media ini siswa dapat belajar dan meningkatkan hasil belajar dengan maksimal. Serta dapat mencapai tujuan dalam pembelajaran. Jenis penelitian ini adalah Reserch and Development, yang mengacu pada model Borg and Gall. Hasil dari penelitian media ajar berbasis AutoPlay materi memelihara lingkungan dalam mata pelajaran IPS memenuhi kriteria sangat valid dengan hasil uji ahli materi mencapai tingkat kevalidan 88%, ahli media mencapai 94%, ahli mata pelajaran mencapai 88%, dan hasil uji coba lapangan mencapai 87,9%, Hasil belajar siswa rata-rata nilai pre-test 62,5 dan nilai post-test 86,5. Pada uji-t manual dengan tingkat kemaknaan 0,05 diperoleh hasil t hitung ≥ t tabel yaitu 3,535 ≥ 2,093 artinya Ho ditolak dan Ha diterima. Sehingga, terdapat perbedaan yang signifikan terhadap bahan ajar yang dikembangkan. Hal ini menunjukkan bahwa produk yang dikembangkan memiliki kualifikasi tingkat kevalidan yang tinggi, sehingga media ajar layak digunakan dalam pembelajaran. ENGLISH: Development of instructional media of Autoplay of IPS is one tool that is to help understand of students' learning. Through the medium of teaching, students are expected to be motivated and growth the skills of students, as well as efforts to familiarize the students work hard in acquiring knowledge. Media that can support the learning process of IPS is a teaching media based Autoplay of material of environment safe. This material describes the preservation of the environment and how to care in everyday life. The purpose of this study was to develop the instructional media based Autoplay of material of environment safe , the object of research were the students of class III MI Yaspuri Malang. With these media students can learn and improve maximum learning outcomes. It also can achieve the goal of learning. This type of research was the Research and Development, which was referred to the model of the Borg and Gall. The results research of instructional media based Autoplay of material of environment safe of IPS met the criteria of very valid test results with matter experts reached a level of validity of 88%, a media reached 94%, the expert subjects reached 88%, and the results of field trials reached 87, 9%. Student learning outcomes of the pre-test average value was 62.5 and a post-test score was 86.5. In manual t-test with significance level was 0.05 that was obtained results t count ≥ t table it was 3.535 ≥ 2.093 meant that Ho was rejected and Ha was accepted. Thus, there was a significant difference to the teaching materials developed. This indicated that the product had been developed had the high qualification level of validity , so a decent teaching media used in learning

Lake Muzahi, Rwanda:limnological features and phytoplankton production

peer reviewedLake Muhazi, a small lake of Rwanda (East Africa) was studied from 1986 to 1990. A dramatic decrease of the catch of Oreochromis niloticus (350 T y-1 in the fifties vs 30 T y-1 in 1982) suggested a loss of productivity or overfishing. In the same period, other ecological changes occurred: the submerged macrophytes regressed and there was a decrease in Secchi depth (0.65 m in 1987 vs 1.5 m in the fifties). Compared to other lakes of the same area, the plankton production seemed low. The results of the present study characterize lake Muhazi as a shallow lake with a rather unstable diurnal stratification and with slight differences in mixing regime between its eastern, deepest part and its western, shallowest part. Secchi disk depth does not vary seasonally to a large extent. The water has a rather high mineral content (conductivity of about 500 μS cm-1 at 25 °C) and low concentrations of dissolved N and P, except in the hypolimnion, where NHinf4sup+ -N can be high. Two species, Microcystis aeruginosa and Ceratium hirundinella, account for most of the phytoplankton biomass, which is about 50-80 mg chlorophyll a m-2 in the euphotic zone, usually with little seasonal variation. Daily gross production estimates amount to about 6 to 9.5 g O2 m-2 d-1 with a significant difference between the two parts of the lake. Data on C:N and C:P ratio in the phytoplankton suggest that some N deficiency might occur in the eastern part. Moreover, the Zm:Zc ratio could also lead to rather low net production rates (0.21-0.25 d-1 for a mixed layer of 4 m) In conclusion, the primary production of lake Muhazi is medium for African lakes and the hypothesis that decreased planktonic production could account for a reduced fish production should be discarded. Whereas the present yield of the fishery is only 20 kg ha-1 y-1, the yield estimated from primary production ranges between 46 and 64 kg ha-1 y-1. This could be reached through proper management. Finally, some hypotheses are given to explain the ecological changes which occurred in the lake. © 1993 Kluwer Academic Publishers

Phytoplankton of Lake Kivu

peer reviewedThis chapter reviews taxonomic composition, biomass, production and nutrient limitation of the phytoplankton of Lake Kivu. Present Lake Kivu phytoplankton is dominated by cyanobacteria – mainly Synechococcus spp. and thin filaments of Planktolyngbya limnetica – and by pennate diatoms, among which Nitzschia bacata and Fragilaria danica are dominant. Seasonal shifts occur, with cyanobacteria developing more in the rainy season, and the diatoms in the dry season. Other groups present are cryptophytes, chrysophytes, chlorophytes and dinoflagellates. According to a survey conducted in the period 2002–2008, the composition of the phytoplankton assemblage was quasi homogeneous among lake basins. The mean euphotic depth varied between 17 and 20 m, and the increase in the ratio between mixed layer depth and euphotic depth to about 2 in the dry season may have selected for diatoms and cryptophytes, which tended to present their maximal development in this season, when cyanobacteria slightly decreased. Mean chlorophyll a concentration was 2.16 mg m−3, and the mean daily primary production was 0.62 g C m−2 day−1 (range, 0.14–1.92), i.e. in the same range as in other large oligotrophic East African Rift lakes. Seston elemental ratios indicated a moderate P deficiency during the dry, mixed season and a severe P limitation during part of the rainy, stratified season; the C:N ratio indicated a moderate N limitation throughout the year. Nutrient addition assays pointed to a direct N limitation and co-limitation by P during rainy seasons and P or N limitation during dry seasons depending on the year. Thus, phytoplankton ecology in Lake Kivu does not differ from that of other Rift lakes, where seasonal variations result in a trade-off between low light with high nutrient supply and high light with low nutrient supply. Phytoplankton production in Lake Kivu is also similar to that of other Rift lakes, and nutrient limitation of phytoplankton growth may occur as a result of variable availability of N and P, as in Lakes Tanganyika and Malawi, even though the extent of P limitation seems greater in Lake Kivu