Monitoring and modeling for investigating driver/pressure–state/impact relationships in coastal ecosystems: Examples from the Lagoon of Venice

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Abstract

In this paper, we show how the integration of monitoring data and mathematical model can generate valuable information by using a few examples taken from a well studied but complex ecosystem, namely the Lagoon of Venice. We will focus on three key issues, which are of concern also for many other coastal ecosystems, namely: (1) Nitrogen and Phosphorus annual budgets; (2) estimation of Net Ecosystem Metabolism and early warnings for anoxic events; (3) assessment of ecosystem status. The results highlight the importance of framing monitoring activities within the “DPSIR” conceptual model, thus going far beyond the monitoring of major biogeochemical variables and including: (1) the estimation of the fluxes of the main constituents at the boundaries; (2) the use of appropriate mathematical models. These tools can provide quantitative links among Pressures and State/Impacts, thus enabling decision makers and stakeholders to evaluate the effects of alternative management scenarios.

Highlights

► Evidences for supporting a DPSIR approach to the monitoring of coastal areas are provided. ► The role of modeling as a building block of a monitoring system is exemplified. ► Integrated monitoring systems include monitoring of fluxes at the waterbody boundaries. ► Integrated monitoring systems require a non fragmented governance structure. ► Models provide indicators and suggest how an ecosystem react to policy scenarios.

Introduction

Coastal ecosystems are subjected to a variety of pressures, which include nutrient enrichment, which may lead to eutrophication (Boesch, 2002), industrial pollution (Islam and Tanaka, 2004) urban growth and tourism (Burak et al., 2004), intensification of maritime activities, fishery (Garcia and Grainger, 2005) and aquaculture (Islam, 2005). The impacts of such pressures have already caused the degradation of natural and semi-natural areas, and loss of terrestrial and marine biodiversity. In order to reverse this negative trend, which could be exacerbated by the foreseeable consequences of climate changes (Lloret et al., 2008, Philippart et al., 2011, Brander, 2010) it is necessary to coordinate the environmental legislations at a regional level. For example, Mediterranean countries which are parties to the “Barcelona Convention”, in 2009 have contracted the Protocol for Integrated Coastal Zone Management in the Mediterranean, in which monitoring is regarded as a fundamental instrument for updating national inventories of coastal zones. In the European Union (EU), two important Directives, the Water Framework Directive (WFD) and the Marine Strategy Framework Directive (MSFD), engage Member States in taking the necessary measures for achieving or maintaining a good environmental status in their groundwaters, inland surface waters, transitional waters, coastal and marine waters.

Monitoring and ongoing assessment are at the core of both EU Directives (Borja et al., 2010), which ask for an initial assessment and classification of coastal and marine waters according to their environmental status and the subsequent implementation of monitoring programs for ongoing assessment, in order to enable Member States to repeat the status evaluation on a periodical basis and verify the achievement of environmental targets. The MSFD, in particular, requires the definition of assessment methodologies which are consistent across marine regions and sub-regions, in order to carry out the initial assessment, to determine the good environmental status and to establish the environmental targets in a consistent way. Therefore, the design of cost-effective, long-term monitoring programmes, consistent across marine regions or sub-regions, is recognized as a fundamental building block of a comprehensive strategy, which has as ultimate goal the undertaking of informed policy actions, aimed at achieving the sustainable development of coastal areas. To this regard, monitoring can be regarded as one of the mandatory “responses” in the Drivers-Pressures-State-Impact and Response (DPSIR) causal framework, which has been adopted by the European Environmental Agency to describe interactions between society and the environment (EEA, 2001).

The adoption of the DPSIR conceptual model naturally leads to: (1) enlarge the scope of monitoring, including the evaluation of the most relevant land-based and marine pressures; (2) to develop mathematical models, to be calibrated and validated on the basis of monitoring data, for improving the understanding of ecosystem functioning and forecasting their evolution under different scenarios of drivers/pressures. Coastal ecosystems are, in fact, characterized by a complex dynamic and may show quick and non-linear responses to changes in pressure. This feature represents an additional difficulty for both the design of effective monitoring strategies and the prediction of coastal ecosystem evolution under different scenarios of socio-economical development and climate change. To this regard, mathematical models play a key role in a DPSIR-based monitoring strategy, since they provide a causal and quantitative link between drivers/pressures and state/impacts.

A proper combination of data concerning status and pressure elements and mathematical model would assist policy makers in evaluating the effects of management policies, since they could provide science-based answers to three types of questions: (1) were environmental targets achieved?; (2) if not, which pressures led to failure to comply with the targets; (3) were targets not achieved because the main cause of ecosystem degradation was global and non-manageable at local level, as it could be in the case of climate changes? In order to answer these questions, it is necessary to integrate several elements concerning both biotic and abiotic components, such as biological, chemical, hydrological, and morphological ones, and to identify accurate methods for determining ecosystem integrity. The implementation of such an “ecosystem approach” to assessment, therefore requires a multidisciplinary team, which should work together since the very early stage of definition of monitoring objectives. This step is, in fact, widely recognized as crucial (Harmancioglu et al., 1999) as, in many instances, monitoring efforts did not deliver the expected information precisely because of unfocused definition of monitoring objectives, sometimes due to conflicts among different monitoring agencies.

The aim of this paper is to show how the integration of monitoring data and mathematical model can generate valuable information by means of a few examples taken from a well studied but extremely complex ecosystem, namely the Lagoon of Venice. We will focus on three key issues, which are of concern also for many other coastal ecosystem, namely: (1) Nitrogen and Phosphorus annual budget and related issues; (2) estimation of Net Ecosystem Metabolism (NEM) and early warning of anoxic crisis; (3) assessment of ecosystem status. The paper is organized as follows. In the next section, we will outline how monitoring networks in the Lagoon have evolved in the last decades, as a response to environmental problems and to comply with changes in the environmental legislation. In the following three ones, we illustrate how the above key issues can be dealt with by integrating field data and, to some extent, Earth Observation (EO) data with models of different complexity. The potential benefits of a further integration among these data and modeling tools with predictive models of the main pressures will be discussed.

Section snippets

Monitoring the Lagoon of Venice: a long history

Monitoring activities in the Lagoon of Venice started in the 1970ies, after the first comprehensive national law for environmental protection was issued and a special legislation for the safeguarding of the historical city and of its surroundings was put into place. At the beginning, monitoring efforts were focused on the central part of the lagoon, which was the most heavily polluted, due to the presence of the industrial area of Porto Marghera, at the left hand side of the city of Venice in

Biogeochemical models: from monitoring data to N and P budgets and other management applications

The budgeting of Nitrogen and Phosphorus represents a fundamental steps toward a quantitative understanding of the dynamics of a coastal ecosystem and is a prerequisite for undertaking science-based and cost-effective management actions. To this regards, it is worthwhile to point out that the estimation of their annual budgets does require a “Driver-Pressure-State-Impact” approach to monitoring, as well as the use of biogeochemical models. In fact, it demands the collection of synoptic data on:

Integrating earth observation, field data and models for NEM estimation and early warnings of anoxic crisis

The integration of date collected by Earth Observation System, such as satellite data and aerial photographs, field measurements and models represents a cost-effective way of obtaining real-time information about the state of coastal and marine ecosystems and reliable short term predictions, thus allowing one to detect in advance possible threats. Automatic probes, in particular, are being increasingly used for measuring basic water quality variables, such as Salinity, Temperature, pH,

Food web, habitat suitability, and End-to-End models: towards an integrated ecosystem approach

As clearly stated by the WFD and the more recent MSFD, the EU policy for the protection of freshwater, transition and coastal marine ecosystems, is based on the classification of their Status, which should be obtained by integrating data concerning a set of “quality elements”. To this regard, priority is given to Biological Quality Elements, BQE, which should be selected for assessing the state of the different communities, (such as the nekton, plankton, etc…) and integrated with data

Concluding remarks

The examples presented in this paper, as well as many other ones which could be found in the literature, strongly support the recommendation, nicely presented in (Harmancioglu et al., 1999), that mathematical models should be regarded as a building block of an integrated and systemic approach to monitoring coastal areas. In particular, dynamic models: (1) can contribute to enhancing our understanding of the ecosystem dynamics, thus providing a quantitative basis to the DPSIR causal framework;

Acknowledgement

Authors thank S. Ciavatta, G. Cossarini, D. Melaku Canu, S. Libralato and T. Lovato for discussion and help in the long term cooperation on research on the Lagoon of Venice, and A.Newton for patience and support. Thaks to L.Montobbio and A.G.Bernstein for their effort in starting Mela moniotirng program and keep it going for so long.

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