Final Remarks
F UTURE RESEARCH LINES
A scientific study is never the final answer for a question, but solely the “tip of the iceberg” that generates working hypotheses. This study provided some evidence on the problems and possible solutions for the application of benthic indices in Portuguese estuaries, but also raised new challenges for future work, such as:
- Identification of reference conditions – The development of a method based on existing reference conditions, as B-IBI, require the selection of habitat specific reference sites. Since all Portuguese estuaries are, at least, minimally impacted, a selection of a representative number of reference sites does not seem feasible in a short-term period. Selecting a pilot estuary with lower human pressure, such as the Mira estuary, and applying mitigation measures that reduce significantly the current impacts could serve as a case study to understand the natural evolution of benthic communities that are under natural stress and use it as a reference for estuaries with similar characteristics (e.g. Mondego estuary);
- Selection of metrics – the selection of metrics to be included in benthic indices to be used in Portuguese estuaries might imply that different metrics and thresholds are used in different habitats, within and among estuaries. A comprehensive examination of the responses of different metrics of communities exposed to diverse natural and anthropogenic levels of stress is needed;
- Long term studies – the definition of monitoring programs in the aim of the WFD require a better understanding of inter-annual changes on the benthic communities, to determine their resilience and the length of the recovery period before they reach equilibrium, after being disturbed by natural events (e.g. floods and droughts). A temporal stratification of the monitoring programs might not be compatible with the
- Biogeographical differences and climate changes - Portugal is a transition area, with a recognized boundary between assemblages northern to Cape Carvoeiro southern to the Tejo estuary. With increased effects of the climate change on the latitudinal distribution of species, a gradual change of the composition of benthic communities is also expected. A possible effect of these changes on the use benthic assessment tools might require particular concern, since strong differences in the taxonomic composition across different regions might influence the performance of indices.
The first two questions are currently being addressed by several studies developed by different Portuguese research teams in different estuaries and also by the Portuguese working group. These challenges might also be partially carried out through the ongoing intercalibration process, in which different countries are adjusting class boundaries by comparing classifications obtained for the same water types using different methods. The third question requires a national monitoring/research policy that favours long term monitoring/research studies, promoting the compilation of a thorough and systematic database on the benthic communities of all Portuguese estuaries. The last question requires that taxonomic skills are recognized as an important scientific competency and some funds are allocated for training taxonomists publishing taxonomic compendiums on the Portuguese fauna.
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