Nowadays it is of common knowledge that environmental compartments are in danger due to high amounts of xenobiotics and that aquatic systems are usually considered their final sink. The presence of a chemical compound and its metabolites in an aquatic ecosystem does not, by itself, indicate deleterious effects. Studies must be carried out to determine and establish relationships between levels of exposure, internal levels measured on organisms' tissues and the early adverse effects that can occur. Chemical compounds (especially persistent hydrophobic ones) may be accumulated by aquatic organisms through different ways: via the direct uptake from water (e.g. fish can uptake by gills or skin), via uptake of suspended particles (e.g. daphnia while filtrating water) and via the consumption of contaminated food. Even without detectable acute or chronic effects, bioaccumulation should be regarded as a hazard criterion in Environmental Risk Assessment (ERA), because some effects may only be recognized in a later phase of life, in future generations, on higher food web levels where biomagnification can be observed.
Nowadays, studies on the toxicity, bioaccumulation and chemical persistency are very important also due to the new policies included in REACH, where special attention is devoted to substances that are (very) persistent, bioaccumulative, and/or toxic (PBT). Here we aim to study the chemical flow within a model aquatic trophic chain, and to understand how chemicals go from a base line (the primer producers), to a secondary consumer (fish). The tested hypotheses are: (1) plankton food quality (phyto and zooplankton) plays a critical role in controlling the strength of trophic pairing in aquatic ecosystems; (2) single exposure results can not be easily transposed to real scenarios. These will be addressed by organising the project into three main experimental phases, as described below. To study a small aquatic trophic chain, primary producers should be included as a baseline. Algae play an important role on the maintenance of system balances. They have also been reported as organism with the ability to accumulate and concentrate chemical compounds (e.g. metals, pesticides), being considered the entrance of pollutants to aquatic trophic chains. As a secondary set within the trophic chain, Daphnia is a suitable choice as a primary consumer. These organisms fed on cellular algae and can make a bridge for an upper step on the chain, towards fish. As a final consumer, fishes can provide crucial information within fish bioconcentration studies to assess the potential of substances to bioaccumulate in the aquatic environment and pose, in a near future, indirect exposure concern to humans via the food chain pathway.
In the 1st phase of this project, bioaccumulation studies will be carried out with algae, daphnia and fish, where the stressor(s) source will be the exposure medium, i.e. water. After knowing the maximum concentration that can be accumulated and within a steady state, not inducing organisms' death, new experiments will be defined to proceed with an exposure via food. This approach will be carried out with natural food (prey) previously contaminated,. The 2nd project phase will follow the same procedures will include binary mixtures of chemicals. In a 3rd and final phase, all trophic levels already described for this model trophic chain will be run simultaneously in one single step/experiment to overview the link and interactions among parts and have a full picture of the exposure scenario.

CESAM members on this project

Ana Catarina Bastos
Pos-Doc

Paula Inês Borralho Domingues
researcher

PhD student

Maria Pavlaki
PhD student

Marta Sofia Soares Craveiro Alves Monteiro Santos
researcher

Sandra Filipe Gonçalves
grant holder

Susana Patrícia Mendes Loureiro
PI