General Introduction
T HESIS OUTLINE
This thesis was divided in six different chapters, including a General Introduction, four papers published or in press in scientific journals included in the science citation index and some Final Remaks, as it follows:
- Chapter 1 is a general introduction that summarises and organizes the major characteristics of estuaries and the constraints that these particular environments present to benthic invertebrate communities. This introduction also gives an overview of policies and regulations that require the implementation of benthic assessment tools, with particular emphasis for the European Water Framework Directive. Some advantages of using benthic invertebrates as indicators of environmental quality are indicated and a summary revision of the major attributes and indices used is also presented. This chapter also includes an update on the current knowledge on the benthic communities of Portuguese estuaries and some of the major findings on the use of benthic assessment tools in these estuaries, in the context of the implementation of the WFD. The objectives of the thesis and the questions behind the definition of these objectives conclude this chapter.
- Chapter 2 consists of a paper that identifies seasonal and spatial patterns of distribution of subtidal benthic invertebrate communities in the Mondego River estuary. This paper examines the adaptations associated with benthic communities in estuaries with highly variable environmental conditions, including the occurrence of floods, addressing questions 1, 2 and 5. It was published in the journal Hydrobiologia, referenced as Chainho, P., Costa, J.L., Chaves, M.L., Lane, M.F., Dauer, D.M. & Costa, M.J. 2006.
Seasonal and spatial patterns of distribution of subtidal benthic invertebrate communities in the Mondego River estuary, Portugal. Hydrobiologia 555: 59–74.
- Chapter 3 consists of a paper on the use of taxonomic sufficiency in Mondego River estuary for typology purposes. Different water body types are identified using the Venice salinity system and ecological consistency of that identification is evaluated by analysing the spatial patterns of distribution of benthic invertebrate communities among different seasons. Different taxonomic levels and taxocenes are used to test for their ability to discriminate between water body types previously defined, addressing questions 2 and 7.
This paper was published in Hydrobiologia, referenced as Chainho, P., Lane, M.F.,
Chaves, M.L., Costa, J.L., Costa, M.J. & Dauer, D.M. 2006. Taxonomic sufficiency as a useful tool for typology in a poikilohaline estuary. Hydrobiologia 587: 63-78.
- Chapter 4 consists of a paper that examines the influence of seasonal variability in the benthic invertebrate communities of the Mondego estuary and how those changes might influence the use of biotic indices. The methods proposed by the WFD Portuguese working group for transitional waters are tested to see how robust the results are when no temporal stratification is applied, addressing questions 3, 4 and 6. This paper was published in Marine Pollution Bulletin, referenced as Chainho, P., Costa, J.L., Chaves, M.L., Dauer, D.M. & Costa, M.J. 2007. Influence of seasonal variability in benthic invertebrate community structure on the use of biotic indices to assess the ecological status of a Portuguese estuary. Marine Pollution Bulletin 54: 1586–1597.
- Chapter 5 consists of a paper that compares the results obtained by two different multimetric indices, TICOR approach and B-IBI, when applied to three Portuguese estuaries with different hydromorphological characteristics and different levels of human pressure. The results of these indices are tested for consistency with a priori status categories based physical-chemical criteria, addressing questions 8, 9 and 10. This paper is in press in Marine Pollution Bulletin, referenced as Chainho, P., Costa, J.L., Chaves, M.L., Costa, M.J. & Dauer, D.M. In press. Use of multimetric indices to classify estuaries with different hydromorphological characteristics and different levels of human pressure. Marine Pollution Bulletin.
- Some final remarks are presented in Chapter 6, integrating the results obtained in each chapter and presenting the major conclusions of the study. Relevant questions that arose from this thesis are also formulated, as guidance for the development of possible future studies.
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