Marcos Mateus

From eutrophic to mesotrophic: modelling watershed management scenarios to change the trophic status of a reservoir.

Management decisions related with water quality in lakes and reservoirs require a combined land-water processes study approach. This study reports on an integrated watershed-reservoir modeling methodology: the Soil and Water Assessment Tool (SWAT) model to estimate the nutrient input loads from the watershed, used afterwards as boundary conditions to the reservoir model, CE-QUAL-W2. The integrated modeling system was applied to the Torrão reservoir and drainage basin. The objective of the study was to quantify the total maximum input load that allows the reservoir to be classified as mesotrophic. Torrão reservoir is located in the Tâmega River, one of the most important tributaries of the Douro River in Portugal. The watershed is characterized by a variety of land uses and urban areas, accounting for a total Waste Water Treatment Plants (WWTP) discharge of ~100,000 p.e. According to the criteria defined by the National Water Institute (based on the WWTP Directive), the Torrão reservoir is classified as eutrophic. Model estimates show that a 10% reduction in nutrient loads will suffice to change the state to mesotrophic, and should target primarily WWTP effluents, but also act on diffuse sources. The method applied in this study should provide a basis for water environmental management decision-making.

Advances in Modeling of Water Quality in Estuaries

Water quality models are in great demand to complement studies about the status of estuarine waters. However, local models do not perform well when boundary conditions are not properly defined and when biogeochemical processes are not described with adequate detail. This chapter presents advanced modeling applications to perform water quality studies in Portuguese estuaries. Boundary conditions for hydrodynamics and biogeochemistry are provided by the Portuguese Coast Operational Model, downscaled by using nested domains with increasing resolution from the regional to the local scale. The nested models of the estuaries are described, and case studies are presented for specific estuaries to compute sediment transport (Tagus estuary), to calculate residence time of water (Mondego estuary), to forecast quality of bathing waters (Estoril Coast), and to quantify nutrient fluxes between estuaries and the open ocean (Ria de Aveiro). The level of detail used to represent biological processes in water quality models is also addressed, including the description of a case study about modeling of species vulnerable to water quality, such as Zostera noltii in Ria de Aveiro. The need for high level of detail to represent microbial loop and carbon cycle in estuaries is discussed with the application of a complex biological model to the Tagus estuary.

An investigation on body displacement after two drowning accidents

The finding of human remains in aquatic environments is usually attributed to causes such as work-related or recreational accidents, suicides, discarded homicide victims, and natural disasters. When the point and date of entry in the water is unknown, these findings pose serious challenges to forensic analysis given the difficulty to estimate the drift of the body. In this context, the information retrieved from cases where the point of entry and body recovery sites are known, as well as the timing, is significant. Two drowning accidents in marine coastal waters were analyzed. In both cases the post-mortem submersion interval (PMSI) is known, as well as the accident (point of entry) and body recovery sites. Accumulated degree days (ADD) was estimated in both cases using satellite sea surface temperature data. In both cases the bodies were recovered in the vicinity of the accident site (~2 km in case 1 and less than 1 km in case 2). Results were interpreted in terms of oceanographic conditions, physical settings and ADD. The results provide some relevant clues on the fate of human cadavers in coastal marine environments that can be used by officials and agencies involved in the recovery of bodies, as well as by forensic investigators when dealing with these findings.

Evaluating light and nutrient limitation in the Tagus estuary using a process-oriented ecological model

Over the past decades, the Tagus estuary (Lisbon, Portugal) has been the focus of several experimental and numerical studies. Field observations suggest that light plays the major role in the control of phytoplankton production in the system, with nutrient limitation only in some confined areas. Light limitation has also been inferred by some modelling studies, but it has been an assumption in most model applications to the estuary. In this study, a process-oriented ecological model for the water column, coupled with a 2-D hydrodynamic model, has been applied to the Tagus estuary to assess the influence of light and nutrients on phytoplankton production. The preliminary results obtained using the model suggests that the system is mostly controlled by light. Nevertheless, nutrients may also control production to some extent but only in lower estuarine areas and in summer. This numerical study seems to agree with the general information on the system, supporting the idea that light control has a major role in the Tagus estuary

A HAB warning system for shellfish harvesting in Portugal

The development of sustainable shellfish aquaculture is highly dependent on the provision of reliable monitoring and predictive information on the occurrence of harmful algal blooms (HABs). The Portuguese HAB early warning system and shellfish closures presented here is a prototype, developed in the ASIMUTH project. It relies on weekly monitoring data composed of observations of HAB species and toxin concentrations within shellfish, and ocean circulation forecasts generated by an operational oceanographic model. The shellfish harvesting areas comprise coastal areas, estuaries+rías and coastal lagoons. The weekly bulletin characterizes the current shellfish closure situation and next weeks forecasts for potentially impacted areas. The period analyzed ranged from 27 July 2013 to 17 March 2014, and describes the first skill assessment of the warning system. The forecast accuracy was evaluated, considering the number of forecasts that were verified to be correct the following week (85%) as well as the number of events not forecasted (false negatives, 12%) and those expected but did not occur (false positives, 3%). Variations were most visible in the first weeks of bulletin implementation and during autumn-winter months. The complementary use of field data, remote sensing and operational models led to more accurate predictions of blooms and range of the event.

Study on the postmortem submersion interval and accumulated degree days for a multiple drowning accident

Recreational accidents in aquatic environments leading to death by drowning are quite frequent. Even if they do not usually require forensic investigation, they may provide useful information on the post mortem submersion interval (PMSI) and its relation with accumulated degree days (ADD). This is particularly useful to forensic science since most studies dealing with these matters rely mostly on animal carcasses as human analogues. In this work we report on a multiple drowning accident resulting in 6 victims. ADD was calculated based on the PMSI and water temperature during this period. PMSI varied between ∼7.4 days and ∼11.4 days, and estimated body drift from the accident site ranged from 0.5km to 8.0km. Surface water temperature in the accident area showed little variation during the PMSI (14.5-16.0°C). Estimated ADD varied between 115°C and 174°C, and between 104°C and 191°C when considering the cumulative lower (ADDmin) and upper (ADDmax) limits for ADD. We compare the results with recently published data on two similar cases, and suggest a range for ADD that can be assumed as necessary before body floatability is regain after a drowning accident.

Modeling the transport pathways of harmful algal blooms in the Iberian coast

The prediction of the path of harmful algal blooms (HABs) along the coast can be achieved using numerical models of ocean circulation in order to reproduce the hydrodynamics of the study area. With this setting, our work aimed at the (1) study of key past events to evaluate the model ability to reproduce the transport pathways of blooms along the Iberian coast, and (2) to assess the relevance of such strictly physical approach. The simulations described here rely on the advection of lagrangian elements after a point release in a hypothetical location for bloom initiation, and the subsequent assessment of the influence of the surface currents transport on the extent of the bloom. Five events were simulated, accounting for blooms of Gymnodinium catenatum, Dinophysis acuminata and Pseudo-nitzschia spp. Model results were compared with field data from the National HAB monitoring program, and were used to evaluate some hypothesis in their interpretation. The effort compiled in this paper, though focused on the transport and dispersion of HAB (after bloom detection), was a critical step toward an integrative forecasting system to determine potential HAB impacted areas, also addressed in this Special Issue.

Evaluating the predictive skills of ocean circulation models in tracking the drift of a human body: a case study

Ocean circulation models are frequently used in maritime Search and Rescue operations due to their skill in simulating the effects of local currents on the transport of people or objects. They are also occasionally used in forensic contexts. Frequently, positively or neutrally buoyant passive particles are used in these simulations, as a proxy for the ‘objects’ in the study. In this paper, the adequacy of passive particle model simulations is tested in an attempt to reproduce the drift of a real case situation. The case study consists of a drowning accident in which the drift was ~2 km for a post-mortem submersion interval (PMSI) of 8.6 days. The simulation results highlighted the limitation of the methodology to predict the correct drift. However, we discuss the shortcomings of the modelling approach, and suggest ways to improve the skill of such numerical tools in predicting body drift after drowning accidents.

Bridging the Gap between Knowing and Modeling Viruses in Marine Systems—An Upcoming Frontier

Viruses are the most abundant biological entities in the worlds oceans. Their potential control on phytoplankton and bacterioplankton dynamics and diversity, and consequent effect on the flow of energy and matter in food webs, is now beyond dispute. Paradoxically, their importance seems to be persistently underestimated by marine modelers, frequently by exclusion, despite the uninterrupted volume of knowledge advanced during the past decades. Bridging the gap between knowing and modelling the role of viruses is, undoubtedly, one of the upcoming frontiers to be crossed in modelling the plankton. This paper has a two-fold objective: (1) review the knowledge on the roles of viruses in marine systems that has been put forward over the past decades, and (2) see how viruses have been incorporated into marine ecosystem models.

On the Choice of Linear Regression Algorithms for Biological and Ecological Applications

MARETEC, Instituto Superior Técnico, Universidade Técnica de Lisboa, Av. Rovisco Pais, 1049-001, Lisboa, Portugal. Departamento de Ecologia, Instituto de Biologia Roberto Alcântara Gomes, Universidade do Estado do Rio de Janeiro, Rua São Francisco Xavier 524, 20.559-900, Rio de Janeiro, Brazil. Department of Biology, Saint Francis Xavier University, Antigonish, Nova Scotia B2G 2W5, Canada. Universidade Autónoma de Lisboa, Rua de Santa Marta, no 56 1169-023, Lisboa, Portugal. CCMAR, Center of Marine Science, University of Algarve, Campus Gambelas, 8005-139 Faro, Portugal. Instituto de Ciencias Ambientales y Evolutivas, Facultad de Ciencias, Universidad Austral de Chile, Casilla 567, Valdivia, Chile. CNRS, Sorbonne Universités, UPMC University Paris VI, UMI 3614, Evolutionary Biology and Ecology of Algae, Station Biologique de Roscoff, CS 90074, Place G. Tessier, 296888 Roscoff, France.