Combining sampling, profiling, remote sensing and modelling to efficiently monitoring estuarine and coastal water quality

Monitoring of coastal and estuarine water quality has been traditionally performed by sampling with subsequent laboratory analysis. This has the disadvantages of low spatial and temporal resolution and high cost. In the last decades two alternative techniques have emerged to overcome this drawback: profiling and remote sensing. Profiling using multi-parameter sensors is now in a commercial stage. It can be used, tied to a boat, to obtain a quick “picture” of the system. The spatial resolution thus increases from single points to a line coincident with the boat track. The temporal resolution however remains unchanged since campaigns and resources involved are basically the same. The need for laboratory analysis was reduced but not eliminated because parameters like nutrients, microbiology or metals are still difficult to obtain with sensors and validation measurements are still needed. In the last years the improvement in satellite resolution has enabled its use for coastal and estuarine water monitoring. Although spatial coverage and resolution of satellite images in the present is already suitable to coastal and estuarine monitoring, temporal resolution is naturally limited to satellite passages and cloud cover. With this panorama the best approach to water monitoring is to integrate and combine data from all these sources. The natural tools to perform this integration are numerical models. Models benefit from the different sources of data to obtain a better calibration. After calibration they can be used to extend spatially and temporally the methods resolution. In Algarve (South of Portugal) a monitoring effort using this approach is being undertaken. The monitoring effort comprises five different locations including coastal waters, estuaries and coastal lagoons. The objective is to establish the base line situation to evaluate the impact of Waste Water Treatment Plants design and retrofitting. The field campaigns include monthly synoptic profiling, using an YSI 6600 multi-parameter system, laboratory analysis and fixed stations. The remote sensing uses ENVISAT\MERIS Level 2 Full Resolution data. This data is combined and used with the MOHID modelling system to obtain an integrate description of the systems. The results show the limitations of each method and the ability of the modelling system to integrate the results and to produce a comprehensive picture of the system.

Coupling anchovy eggs and hydrodynamic model as an assessement tool for estuarine ecohydrological management

Nitrate and urban waste water directives have raised the need for a better understanding of coastal systems in European Union. The incorrect application of these directives can lead to important ecological or social penalties. In the paper this problem is addressed to Ria Formosa Coastal Lagoon. Ria Formosa hosts a Natural Park, important ports of the southern Portuguese coast and significant bivalve aquaculture activity. Four major urban waste water treatment plants discharging in the lagoon are considered in this study. Its treatment level must be selected, based on detailed information from a monitoring program and on a good knowledge of the processes determining the fate of the material discharged in the lagoon. In this paper the results of a monitoring program and simulations using a coupled hydrodynamic and water quality / ecological model, MOHID, are used to characterise the system and to understand the processes in Ria Formosa. It is shown that the water residence time in most of the lagoon is quite low, of the order of days, but it can be larger in the upper parts of the channels where land generated water is discharged. The main supply of nutrients to the lagoon comes from the open sea rather than from the urban discharges. For this reason the characteristics and behaviour of the general lagoon contrasts with the behaviour of the upper reaches of the channels where the influence of the waste water treatment plants are high. In this system the bottom mineralization was found to be an important mechanism, and the inclusion of that process in the model was essential to obtain good results.

Benthic biotope index for classifying estuarine habitats

An integration of sediment physical, chemical, biological, and toxicity data is necessary for a meaningful interpretation of the complex sediment conditions in the marine environment. Assessment of benthic community is a vital component for that interpretation, yet their evaluation is complex and requires a large expenditure of time and funds. Thus, there is a need for new tools that are less expensive and more understandable for managers. This paper presents a benthic biotope index to predict from physical and chemical variables the occurrence of macrobenthic habitats, applied to Sado Estuary, as a case of study.

Ecological quality assessment of transitional waters based on fish assemblages in Portuguese estuaries: The Estuarine Fish Assessment Index (EFAI)

The assessment of water quality has changed markedly worldwide over the last years, especially in Europe due to the implementation of the Water Framework Directive. Fish was considered a key-element in this context and several fish-based multi-metric indices have been proposed. In this study, we propose a multi-metric index, the Estuarine Fish Assessment Index (EFAI), developed for Portuguese estuaries, designed for the overall assessment of transitional waters, which could also be applied at the water body level within an estuary. The EFAI integrates seven metrics: species richness, percentage of marine migrants, number of species and abundance of estuarine resident species, number of species and abundance of piscivorous species, status of diadromous species, status of introduced species and status of disturbance sensitive species. Fish sampling surveys were conducted in 2006, 2009 and 2010, using beam trawl, in 13 estuarine systems along the Portuguese coast. Most of the metrics presented a high variability among the transitional systems surveyed. According to the EFAI values, Portuguese estuaries presented a "Good" water quality status (except the Douro in a particular year). The assessments in different years were generally concordant, with a few exceptions. The relationship between the EFAI and the Anthropogenic Pressure Index (API) was not significant, but a negative and significant correlation was registered between the EFAI and the expert judgement pressure index, at both estuary and water body level. The ordination analysis performed to evaluate similarities among North-East Atlantic Geographical Intercalibration Group (NEAGIG) fish-based indices put in evidence four main groups: the French index, since it is substantially different from all the other indices (uses only four metrics based on densities); indices from Ireland, United Kingdom and Spain (Asturias and Cantabria); the Dutch and German indices; and the indices of Belgium. Portugal and Spain (Basque country). The need for detailed studies, including comparative approaches, on several aspects of these assessment tools, especially in what regards their response to anthropogenic pressures was stressed. (C) 2011 Elsevier Ltd. All rights reserved.

Robustness of the Estuarine Fish Assessment Index (EFAI) regarding water body definition criteria

According to the Water Framework Directive (WFD) transitional waters should be differentiated according to type and, in some cases, divided into different water bodies. This raises a dilemma in trying to define parts of a continuum. In the sequence of WFD several indices have been proposed including the Estuarine Fish Assessment Index, which can be applied taking an estuary as a whole (EFAI - without water bodies division) or divided in water bodies (EFAI(WB)). The purpose of this work is to analyze the robustness of the Estuarine Fish Assessment Index, based on three different ways of dividing Portuguese estuaries into water bodies according to different criteria (criterion 1 - distance to the estuary mouth, criterion 2 - salinity and criterion 3 - morphology, salinity and human dimension as pressure and state). In this study we evaluated at which degree these three criteria could influence the ecological quality ratio (EQR) results, when the index was applied to water body level (EFAI(WB)). Also, for each estuary, the EQR(WB) results for each criterion of EFAI(WB) were combined and weighted according to the water bodies areas (EFAI overall weighted - EFAI(Ow)). Finally, it was compared if the results obtained for each criterion with the EFAI(OW) were similar to the results of the index application taking the estuary as a whole (EFAI without water bodies division). No significant differences were found in both cases, which indicated that this index is a robust method regarding the division of the estuaries in different water bodies, which is an important element of a fish-based multimetric tool for assessing estuarine ecological quality. However, in some cases, different ecological quality statuses were achieved when applying the EFAI(Ow) or the EFAI. This work addressed several aspects regarding the possible division of water bodies at the WFD context. (C) 2012 Elsevier Ltd. All rights reserved.