Autor(es):
Correia, Vânia 
; Ribeiro, R. ; Moreira-Santos, Matilde
Data: 2013
Identificador Persistente: http://hdl.handle.net/10316/25768
Origem: Estudo Geral - Universidade de Coimbra
Assunto(s): Sublethal assay; Freshwater toxicity; Theodoxus fluviatilis; Acid mine drainage; Cadmium
Descrição
Contaminant-driven feeding inhibition has direct and immediate consequences at higher levels of biological organization, by
depressing the population consumption and thus hampering ecosystem functioning (e.g., grazing, organic matter decomposition). The
present study aimed at developing a short-term laboratory and in situ assay based on the postexposure feeding of the freshwater snail
Theodoxus fluviatilis. A method to precisely quantify feeding rates was first developed, consisting of a 3-h feeding period, in darkness, on
150 defrosted nauplii of the brine shrimp Artemia franciscana. Postexposure feeding after a 48-h exposure to cadmium was approximately
as sensitive as survival, with the median effective concentration (EC50) and median lethal concentration (LC50) being 85 mg/L and
102 mg/L, respectively, and the 20% effective concentration (EC20) and 20% lethal concentration (LC20) being 41 mg/L and 77 mg/L,
respectively. Together, both effects at the LC20 reduced population consumption by 56%. In situ experiments at reference sites covering
broad ranges of current velocity, hardness, conductivity, sediment organic matter content, and sediment particle size distribution revealed
the influence of these abiotic conditions on postexposure feeding, in the absence of contamination, to be negligible. The effectiveness of
the in situ assay was evaluated at 5 sites contaminated with acid mine drainage. Surviving organisms at the single partially lethal site (37%
mortality) presented a 54% feeding inhibition relative to the reference, whereas the population consumption would be inhibited by 71%,
confirming the integration of survival and feeding to be pertinent for estimating contaminant effects at higher levels of biological
organization. The present study was funded by the Fundação para a
Ciência e a Tecnologia (Portugal) through the FRAMEFFECTIVE and
ECOTOXTOOLS projects (contracts PTDC/AAC-AMB/105411/2008 and
PTDC/AAC-AMB/103547/2008, respectively) and through Ciência 2007—
Human Potential Operational Program and Quadro de Referência Estrat egico
Nacional through European Social Fund and Ministry of Education and
Science funds.
