Takako Watanabe

What can dry reservoir sediments in a semi-arid region in Brazil tell us about cladocera?

A study of dry sediments in a semi-arid reservoir in northeast Brazil was undertaken. Eleven quadrants were sampled along a transect in the reservoir. Sediments were collected and transferred to distilled water in the laboratory where they were subsequently filtered through a 50 μm mesh filter. Ecloded cladocerans were identified. Several species hatched in the laboratory, and were compared with the cladoceran community collected before the reservoir had dried out. In previous years, only Moina minuta, Diaphanosoma spinulosumand Alonella hamulata were found in the lake, each on a different sampling date. In the laboratory, however, other species like Macrothrix sp., Leydigia ipojucae, Latonopsis australis and Ceriodaphnia cornuta f. rigaudi hatched. We observed that those quadrants, which were located in higher parts of the reservoir, and had been dry for 13 years, contained species that appeared only in these quadrants. Thus, the sediments show that independently of the species actively present in the water column, sediments store species in diapause stages: an observation that should not be overlooked, especially in biodiversity studies.

Developing the gastropod Pomacea lineata (Spix, 1827) as a toxicity test organism

The authors describe a screening method to semi-quantitatively determine time independent LC 50s and ILC 50s. The protocol is based on the response of starved 4-day-old snails (Pomacea lineata). The neonates were exposed to paraquat and a textile mill effluent for 4–15 days without food. The ILC 50 and time-independent LC 50 for paraquat were, respectively, approximately 0.15 and 0.35 mg.l-1. The respective lowest observed mortality concentration (LOMC) and no observed mortality concentration (NOMC) were 0.12 and 0.07 mg.l-1. Snails are not generally used in toxicity testing, however this test organism appears to be worthy of further development. It should prove particularly useful in northeast Brazil where lack of chemical analytical equipment and taxonomic keys for faunal surveys places the emphasis for pollution monitoring on toxicity testing.

Ocorrência de Lymnaea columella (Gastropoda: Lymnaeidae), hospedeiro intermediário da Fasciola hepatica, para o Estado da Paraíba, Brasil

Foi registrada a ocorrencia de Lymnaea columella (Gastropoda: Lymnaeidae), primeiro hospedeiro intermediario da Fasciola hepatica, para o Estado da Paraiba, Brasil, associado a macrofitas aquaticas.

A preliminary report on the application of Macrobrachium amazonicum Heller, 1862 (Decapoda: Palaemonidae) as a biomarker

A method is described for the rapid evaluation of water quality through monitoring the respiratory response of Macrobrachium amazonicum a dominant benthic macroinvertebrate of Northeast Brazil constituting a source of nutrients for fish and humans. By maintaining the organism in a respiratory chamber supplied with test water (gravity-feed) at a rate of 10 ml min-1, it is possible to identify when the organism is in stress. Respiration rates were determined before (control) and after test concentrations were introduced. The herbicide paraquat was used because of its popularity with sugar cane cultivators and reported low toxicity. There was a discrete increase in respiration associated with acute toxicity at all concentrations tested above 0.035 μg l-1. At 0.01 μg l-1 no increase in respiration was observed and prawn survival continued until the experiment was terminated (25 days).

The implementation of a regional biomonitoring program in northeast Brazil

Abstract A methodology to inventory water quality in northeast Brazil through biomonitoring is described. Essentially the methodology is based on the United States Environmental Protection Agency protocol supplemented by benthic macroinvertebrate diversity data. To date six test species have been selected to represent the overall aquatic biota response to different pollutants: the snail (Pomacea linetata), fish (Molienesia sp.), prawn (Macrobrachium amazonicum), zooplankton (Daphnia similis), macrophytes (Lemna sp.) and periphytic algae (Selenastrum capricornutum). These organisms will be exposed to test waters and evaluated with regard to acute toxicity (survival) and chronic toxicity (photosynthesis, respiration, excretion, growth and reproduction). An extensive training program has been set-up. Regional governmental laboratories and staff will be equipped with the capacity to conduct bioassays routinely. Training and research activities are housed in the Environmental Management laboratories at the Fed...

Development of methods to assess the impact of herbicide use on the benthos of littoral impoundments in northeast Brazil

We assess the impact on water quality of thelittoral watersheds in the Northeast Region ofBrazil caused by unregulated sugar-cane farmingpractices. Virtually all water sources areimpounded because near-drought conditionspertain throughout the region. Withoutexception, these water bodies are exploitedprimarily for domestic/municipal andagricultural purposes, and secondarily as afood source. Most of the land under cultivationis used for sugar cane production. Preliminaryacute and chronic toxicity data for theherbicide paraquat, applied in sugar canefarming, are included for prawn (Macrobrachium amazonicum), snails (Pomacea lineata) and for the cladoceran Daphnia similis. They indicate a sensitivityto paraquat, orders of magnitude higher thanpredicted from literature on the biota oftemperate species, when, coupled with theprevailing limnological cycles (annual run-off,scouring, erosion, eutrophication and drought),the toxicity data suggest a hithertounsuspected level of ecological vulnerability.This underscores the need for theimplementation of an inexpensive toxicitytesting program, based on endemic speciesreflecting local conditions in NortheastBrazil.

Chironomus gr. decorus (Diptera: Chironomidae) e outros insetos aquáticos de um açude temporário do semi-árido paraibano, Brasil

The aim purpose was to study the composition of Chironomidae fauna and the anothers aquatic insects in a temporary dam. Qualitative samples were realized in two periods: August/1995, higher level of water and March/1999, after the completely drying dam for 3 years. Only one species of Chironomidae was registered, Chironomus gr. decorus, in both periods, which contributed with 28.09% for the total aquatic insects fauna in August/95 and it was the only species to colonize the sediment of dam after 3 years of drying period. In August/95 observed the occurrence of Odonata, Coleoptera, Hemiptera, Ephemeroptera and Trichoptera. In this period was evidenced lower values of dissolvid nitrogen (ammonium, nitrite and nitrate), sulfate and electric conductivity compared with March/99. Thus, the aquatic insects fauna were strongly ifluenced by physical and chemycal conditions. Two considerations its may be registred, in spite of appearing of Chironomus gr. decorus, immediately after the dry period: 1. The oviposition by flying females, originating from permanent waters, is the most important means of recolonizing habitat refilled; 2. Or the species it may be survive the desiccation, as larvae in dry sediment or in cocoon during the dry period.