Betina Kozlowsky-Suzuki

Accumulation of microcystins by a tropical zooplankton community

In the current study, the hepatotoxic peptide microcystins, were measured in the zooplankton community of Jacarepaguá Lagoon during a 6-month period. Concurrent phytoplankton and seston samples were obtained. Microcystins were measured in seston and phytoplankton by High Performance Liquid Chromatography (HPLC), and in zooplankton by an Enzyme-Linked Immunosorbant Assay (ELISA). Zooplankton community was comprised mainly by the rotifers Brachionus angularis and B. plicatilis, the cladocerans Moina micrura and Ceriodaphnia cornuta and the copepod Metacyclops mendocinus. Phytoplankton was dominated by Microcystis aeruginosa during all the studied period. Microcystins in zooplankton ranged from 0.3 to 16.4 microg g(-1) DW, while in the sestonic samples they ranged from undetectable values to 5.8 ng g(-1) DW. Microcystins in net phytoplankton ranged from 0.3 to 3.9 mg g(-1) DW. We conclude that zooplankton from Jacarepaguá Lagoon were efficient accumulators of microcystins from seston and that these animals can be potential vectors in the transferring of such toxins to higher trophic levels in the aquatic food chain.

Does cyanobacterial toxin accumulate in mysid shrimps and fish via copepods

It has been suggested that pelagic planktivores may receive cyanobacterial toxins indirectly, i.e., by preying on organisms that have ingested cyanobacteria. We tested this hypothesis in laboratory conditions by providing mysid shrimps, Mysis relicta, and three-spined sticklebacks, Gasterosteus aculeatus, with cyanobacteria-fed copepods. The aim of the study was to observe the potential transfer and accumulation of the toxin nodularin, produced by the cyanobacteria Nodularia spumigena, in planktivore tissue during the 10-day trials. The concentration of nodularin was measured by two toxin detection methods, enzyme-linked immunosorbent assay (ELISA) and protein phosphatase (PPase) inhibition assay. The ELISA results showed that the toxin concentrations in mysid tissue were significantly higher than in fish tissue, whereas no differences between species were detected by PPase inhibition assay. The concentrations measured by ELISA suggested that accumulation had taken place in mysids, since the toxin increased with time in the animals. The concentrations, measured by PPase inhibition assay, were significantly higher than the ones measured by ELISA. We conclude that cyanobacterial toxin may accumulate in higher trophic levels via copepods and that the results are more reliable if analysed with several methods.

Description of Macrochaetus kostei n.sp (Rotifera, Trichotriidae) from a coastal lagoon of Rio de Janeiro, Brazil

A new rotifer is described and figured based on females taken from Comprida lagoon, Rio de Janeiro State, in southeastern Brazil. This new animal belongs to the Genus Macrochaetus which includes several species recorded in South America. A key to species of the Genus Macrochaetus of the Neotropical Region is presented.

Rotifers from a humic coastal lagoon of Rio de Janeiro State, Brazil

Abstract A four-year study of species composition of the zooplankton community was conducted at Lagoa Comprida, a Brazilian coastal lagoon. Forty-two species of rotifers were recorded and illustrated. All rotifer species, except Lecane boettgeri Koste, 1986 and Macrochaetus kostei, José de Paggi, Branco & Kozlowsky-Suzuki, 2000, have already been found in other areas of Brazil. Some factors, which probably favored the dominant richness and density of rotifers in the zooplankton community, are discussed.

Predicting temporal variation in zooplankton beta diversity is challenging

Beta diversity, the spatial variation in species composition, has been related to different explanatory variables, including environmental heterogeneity, productivity and connectivity. Using a long-term time series of zooplankton data collected over 62 months in a tropical reservoir (Ribeirão das Lajes Reservoir, Rio de Janeiro State, Brazil), we tested whether beta diversity (as measured across six sites distributed along the main axis of the reservoir) was correlated with environmental heterogeneity (spatial environmental variation in a given month), chlorophyll-a concentration (a surrogate for productivity) and water level. We did not found evidence for the role of these predictors, suggesting the need to reevaluate predictions or at least to search for better surrogates of the processes that hypothetically control beta diversity variation. However, beta diversity declined over time, which is consistent with the process of biotic homogenization, a worldwide cause of concern.