Outline of the project

Human activities are threatening biodiversity in freshwaters leading to irreversible alterations in ecosystem processes. One of the most important processes for the functioning of small-forested streams is the decomposition of allochthonous plant-litter, which constitutes the major source of nutrients and energy in freshwater food-webs.

Microbial decomposers, specially a group of fungi called aquatic hyphomycetes, play a critical role in this process degrading plant material and increasing its palatability for invertebrate shredders. Previous studies indicated that the communities of aquatic fungi in streams are sensitive to human induced changes, with consequences to ecosystem processes. Although these fungi were already suggested as potential indicators of water quality in freshwater ecosystems, few studies were conducted in order to analyse this issue. Its use as bioindicators of stream condition was probably limited by the restricted available techniques to assess their diversity.

Traditionally, diversity of aquatic hyphomycetes has been assessed by the microscopic identification of their reproductive structures by aerating colonized plant-material in microcosms containing sterilized stream water. Although the limitations of traditional based approaches, much of the current knowledge of the diversity and distribution of aquatic fungal communities in freshwaters rely on them. However, the utility of conidia analysis at sites suffering from anthropogenic stress might be limited by the fact of its production being inhibited by high concentrations of pollutants in the stream water.

More recently, molecular approaches, such as DGGE, T-RFLP and the construction of clone libraries, applied to rRNA genes, proved as good techniques to detect temporal and spatial patterns and the impact of anthropogenic stress on aquatic fungal communities in freshwater ecosystems. Even though that the sequencing of bands of interest on DGGE and environmental clones from the constructed libraries could provide the identity at species level, the lack of reference sequences on gene databases might limit its further use. Additionally by using rRNA genes, since they detect both active and inactive populations, this definitely limits the usefulness of the approach when investigating the response of communities to environmental perturbations.

The FunDiver project aims to develop molecular tools for assessing the diversity and activity of fungi on plant-litter decomposing in freshwater ecosystems. Specific aims are:

1. to isolate and identify, by classical taxonomy, fungi from different freshwater habitats and geographic regions;

2. to evaluate the potential of different regions of ribosomal RNA gene to create reference libraries of fungal DNA sequences;

3. to investigate inter- and intra-specific relationships between fungi;

4. to use molecular markers to establish phylogeographic patterns;

5. to assess total and active aquatic fungal diversity in environmental samples.

Overall this project aim to contribute to a better knowledge about the identity, diversity and activity of fungal species on plant-litter decomposing in streams. The optimization of these techniques will allow an accurate identification of fungal species from communities decomposing plant-litter, which will increase its potential use as a tool to assess the integrity of freshwater ecosystems.