Dynamics of small-sized Cladocera and their algal diet in lake with toxic cyanobacterial water blooms

Species composition and quantitative structure of small-sized Cladocera community and their algal diet before, during and after cyanobacterial blooms were studied in highly eutrophic lake. The objective of the study was to investigate, how the mass development of toxin-producing cyanobacteria affect the abundances of small-sized Cladocera and their preferences within consumed algal cells. Cyanobacterial blooms were predominantly constituted by microcystin-producing genera Planktothrix, Dolichospermum, Microcystis. The concentration of intracellular microcystins in lake water ranged 0.0–23.61 μg dm−3. Bosmina longirostris, B. coregonii, Diaphanosoma brachyurum and Daphnia cucullata were dominant in Cladocera community. The highest abundances of B. longirostris occurred in periods without cyanobacterial blooms and B. coregonii during blooms and after them. The maximum abundances of D. cucullata were observed before and after the cyanobacterial blooms, while the abundance of D. brachyurum was the highest at the beginning of blooms. Small Bacillariophyceae, small Chlorophyceae and Cryptophyceae were the most abundant among identified algal cells detected in digestive tracts of the Cladocera dominants. Tracts of D. cucullata, B. longirostris and B. coregonii contained the highest number of Bacillariophyceae always before blooms. During cyanobacterial blooms, cells of small Chlorophyceae predominated in tracts of D. cucullata. After bloom, cells of Cryptomonas spp. were mainly consumed both by D. cucullata and by B. coregonii. Fragments of Dolichospermum spp., besides Bacillariophyceae and Cryptomonas spp. cells, were occasionally found in tracts of D. brachyurum. Our study indicated that blooms constituted by toxin-producing cyanobacteria may influence quantitative and qualitative structure of the small-sized Cladocera community.

Struktur Komunitas Zooplankton di Bendungan Telaga Tunjung, Kabupaten Tabanan-Bali

Zooplankton are the heterotroph aquatic organisms and has a week swimming. Zooplankton acts as the first consumer in the waters, which utilize phytoplankton as their food. This research located in Telaga Tunjung reservoir, Timpag Village, Kerambitan Subdistrict, Tabanan Regency. The reservoir is used for industry, irrigation and tourism development. The aim of the research was to determine the community structure of zooplankton in Telaga Tunjung reservoir. This research was conducted from January to February 2016. Water sampling was conducted twice with a sampling interval of 2 weeks in 4 stations. There was a total of 23 species of zooplankton found, consisting of 6 classes: Eurotatoria (8 genera), Ciliatea (1 genera), Branchiopoda (4 genera), Monogononta (1 genera), Tubulinea (1 genera) and Maxillopoda (3 genera). The most common species of zooplankton found in the sampling station were Polyarthra vulgaris (3.04 ind/l), Anuraeopsis coelata (1.28 ind/l), Keratella valga (0.43 ind/l), Vorticella sp. (0.49 ind/l), Diaphanosoma brachyurum (0.28 ind/l), Nauplius sp. (0.16 ind/l) and Megacyclops viridis (1.16 ind/l). The average abundance of zooplankton was 9.38 ind/l. Based on the abundance of zooplankton, the trophic status of Telaga Tunjung reservoir is mesotrophic.

LEVANTAMENTO DE ZOOPLÂNCTON EM PISCICULTURA DA ESTÂNCIA TURÍSTICA DE SANTA FÉ DO SUL - SP

A piscicultura é uma atividade que vem crescendo no Brasil. Essa prática acarreta o lançamento desenfreado de resíduos e metabólitos diretamente no ambiente, causando impactos ambientais. Os organismos zooplanctônicos tem grande sensibilidade ambiental e respondem a diversos tipos de impactos e, por isso, são usados como bioindicadores de condições boas ou ruins da qualidade da água. O trabalho objetivou inventariar os zooplânctons existentes na Piscicultura Grupo Ambar Amaral em Santa Fé do Sul - SP, e avaliar os possí­veis impactos ambientais. As coletas foram realizadas mensalmente, com o auxí­lio de uma rede de plâncton 68 õm. As amostras obtidas foram anestesiadas e reservadas em garrafas etiquetadas. A identificação dos microrganismos foi realizada sob microscópio óptico utilizando-se chaves especí­ficas. Foram identificados no presente trabalho os seguintes táxons: Tecamebas (Protista), o filo Rotí­fera foi representado pelos gêneros Philodina, Otostephano, Collotheca, a espécie Mytilina ventralis, e pela famí­lia Gastropodidae; dentre os crustáceos, as espécies Diaphanosoma brachyurum, Diaphanosoma birgei e Daphnia gessneri da subclasse Cladocera e as ordens Calanoida e Cyclopoida da subclasse Copepoda. A maior quantidade de indivíduos registrada foi de Copepoda, sendo representados pelas formas juvenis (náuplios e copepoditos) e formas adultas. A análise da comunidade zooplanctônica na piscicultura revelou uma diversidade de espécies para os diferentes grupos taxonômicos.

Predation follows competition in depth selection behaviour of Cladocera in a deep lake (E Poland)

Predation follows competition in depth selection behaviour of Cladocera in a deep lake (E Poland)Observations of the vertical distribution of Cladocera in the pelagic zone of the deep Lake Piaseczno (38.8 m) focused on 6 species:Diaphanosoma brachyurum, Daphnia longispina, D. cucullata, Bosmina coregoni, B. longirostris, andChydorus sphaericus.The animals displayed clear depth preferences, and their migration patterns were limited to small depth amplitudes. The results show that vertical habitat segregation of cladocerans in the lake consists mostly in the mechanism of competition for accessible food resources, rather than in the mechanism of predation avoidance.