A B S T R A C TFor the future use of the marine benthic copepod Tisbe biminiensis in solid-phase sediment toxicological bioassays, the present study investigated the effect of muddy sediment from the Maracaípe estuary (northeastern Brazil), sediment particle size and the reference toxicant potassium dichromate on the species. Muddy sediment from Maracaípe can be used as control sediment, since it does not interfere in the copepod life-cycle and has metal contamination levels that are unlikely to produce any detrimental biological effects on benthic invertebrates. Neither survival nor fecundity was affected by grain size, suggesting that this species can be used with any kind of sediment from muddy to sandy. The sensitivity of T. biminiensis to K 2 Cr 2 O 7 in acute tests was similar to that of other organisms. The LC 50 (lethal concentration to 50% of the test organisms) medium values for T. biminiensis were 7.51, 4.68 and 3.19 mg L -1 for Cr in 48, 72 and 96 h, respectively. These results suggest that T. biminiensis is a promising organism for use in solid-phase sediment toxicity assessments.
R E S U M OVisando o uso futuro do copépodo marinho bentônico Tisbe biminiensis em bioensaios toxicológicos de sedimentos na fase sólida, o presente estudo investigou o efeito do sedimento lamoso do estuário de Maracaípe (Nordeste do Brasil). Foram considerados a granolometria e o tóxico de referência dicromato de potássio sobre a espécie. O sedimento lamoso de Maracaípe pode ser usado como controle, uma vez que não interfere no ciclo de vida do copépodo e possui níveis de contaminação de metais que não causariam efeitos biológicos em invertebrados bentônicos. Nem a sobrevivência ou fecundidade foi afetada pelo tamanho do grão, sugerindo que esta espécie pode ser usada com qualquer tipo de sedimento, de lama a areia. A sensibilidade de T. biminiensis ao K 2 Cr 2 O 7 em testes agudos foi similar a de outros organismos. Os valores de CL 50 (concentração letal a 50% dos organismos) para T. biminiensis foram em média 7,51, 4,68 e 3,19 mg L -1 para o Cr em 48, 72 e 96h, respectivamente. Estes resultados sugerem que T. biminiensis é um organismo promissor para uso em avaliações de toxicidade com a fase sólida do sedimento.
Copepods have a number of advantages for use as live food in cultures of fish and crustacean larvae. This study aimed to develop culture techniques of Tisbe biminiensis Volkmann‐Rocco 1973 in volumes of 500 mL. The first experiment tested the effect of salinity on survival and fecundity. The other experiments studied the population growth comparing two levels of daily ration and the effect of sand sediment in cultures. The cultures were carried out on plastic boxes at 29°C, salinity of 34 g L−1 and 12 h light/12 h dark photoperiod with aerated filtered seawater, total renewal every other day. Adult females tolerated the decrease of salinity from 34 to 27 g L−1 but the offspring production decreased significantly. The salinity of 20 g L−1 was not tolerated at all. Tisbe biminiensis attained one of the highest rates of increase in cultures among harpacticoids (0.33 day−1) and a high density of 205 individual ind. mL−1. The carrying capacity of the population was estimated as 67 200 ind. in 500 mL recipients. In conclusion, T. biminiensis grow fast and attain high densities in cultures of 500 mL volume without sediment, feeding a daily ration of 50–100% of copepodite biomass.
Worldwide cyanobacterial blooms have been registered, where harmful species dominance is associated to producing of toxic compounds (cyanotoxins) with adverse effects on several organisms. Acute toxicity of crude extracts from Microcystis bloom occurring in Mundaú reservoir was evaluated by bioassays with the neotropical Cladocera Moina minuta. Samples were taken in the reservoir during the rainy (April/2012) and dry season (September/2012). Cyanobacterial analyses were performed by identification on optical microscopy and direct counting using an inverted microscope. Bloom samples were frozen, lyophilized and re-suspended in deionized water for preparation of extracts. Tests with the cladoceran were carried out in test tubes with different concentrations of the crude extract, diluted in 10 mL reconstituted water. In both rainy and dry periods, densities of Microcystis spp. were above 15x10 3 ind mL-1. Microcystin concentrations in the extracts were 0.70 (+ 0,009) (rainy season) and 0.69 (+ 0,005) (dry season) μg g-1. The LC 50 (48h) of crude extract for both rainy and dry periods was 160 (100-255) and 72 (4-1113) mg L-1 , respectively. These results indicated that extracts of Microcystis spp. were acutely toxic to M. minuta population with suggesting that such events represent potential toxicity to zooplankton.
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