Browsing by Author "Wolanski, Eric"
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- An ecohydrology model of the Guadiana Estuary (South Portugal)Publication . Wolanski, Eric; Chícharo, Luís; Teodosio, Maria; Morais, P.A 1-D ecohydrology model is proposed that integrates physical, chemical and biological processes in the Guadiana Estuary during low flow conditions and that predicts the ecosystem health as determined by the following variables: river discharge, nutrients, suspended particulate matter, phytoplankton, zooplankton, bivalves, zooplanktivorous fish and carnivorous/omnivorous fish. Low flow conditions prevail now that the Alqueva dam has been constructed. The ecological sub-model is based on the non-linear Lotka-Volterra equation. The model is successful in capturing the observations of along-river changes in these variables. It suggests that both bottom-up and top-down ecological processes control the Guadiana Estuary ecosystem health. A number of sensitivity tests show that the model is robust and can be used to predict e within likely error bounds provided by the sensitivity tests e the consequences on the estuary ecosystem health of human activities throughout the river catchment, such as the irrigation farming downstream of the Alqueva dam, reclamation of the salt marshes by urban developments, and flow regulation by the Alqueva dam. The model suggests that the estuarine ecosystem health requires transient river floods and is compromised by flow regulation by the Alqueva dam. Remedial measures are thus necessary.
- Applying ecohydrology to promote a nature-based solutionPublication . Teodosio, Maria; Faria, Silvana; Baptista, Vânia; Wolanski, EricThis chapter aims to develop an ecohydrological modelling approach to propose an environmental engineering solution based on historical nature-based information to alleviate the severe water degradation problem within Luanda Bay, Angola. This solution would improve local communities' ecosystem health and quality of life. The model suggests a simple and practical solution to solving the pollution problem by opening a cut from the bay's shallows to the sea. This will essentially reproduce an old bay opening to the sea, which was filled early in the last century. The residence time of water in the shallows of Luanda Bay would be reduced to about one week by excavating the channel over the land is straightforward. This should return the system to a more natural state and improve the water quality for recreational activities, increase the quality of marine food resources, reduce toxic algae blooms, and improve the quality of life of people in the area. Nevertheless, preventing pollutants from reaching Luanda Bay is the only long-term solution to restore a healthy environment in Luanda Bay
- Biophysical processes leading to the ingress of temperate fish larvae into estuarine nursery areas: A reviewPublication . Teodosio, Maria; Paris, Claire B.; Wolanski, Eric; Morais, PedroA series of complementary hypotheses have been proposed to explain the recruitment of marine and temperate pelagic fish larvae originated from pelagic eggs in coastal environments. In this review, we propose a new and complementary hypothesis describing the biophysical processes intervening in the recruitment of temperate fish larvae into estuaries. This new hypothesis, the Sense Acuity And Behavioral (SAAB) hypothesis, recognizes that recruitment is unlikely if the larvae drift passively with the water currents, and that successful recruitment requires the sense acuity of temperate fish larvae and their behavioral response to the estuarine cues present in coastal areas. We propose that temperate fish larvae use a hierarchy of sensory cues (odor, sound, visual and geomagnetic cues) to detect estuarine nursery areas and to aid during navigation towards these areas. The sensorial acuity increases along ontogeny, which coincides with increased swimming capabilities. The swimming strategies of post-flexion larvae differ from offshore areas to the tidal zone. In offshore areas, innate behavior might lead larvae towards the coast guided by a sun compass or by the earth's geomagnetic field. In areas under limited influence of estuarine plumes (either in energetic nearshore areas or offshore), post-flexion larvae display a searching swimming behavior for estuarine disconnected patches (infotaxis strategy). After finding an estuarine plume, larvae may swim along the increasing cue concentration to ingress into the estuary. Here, larvae exhibit a rheotaxis behavior and avoid displacement by longshore currents by keeping bearing during navigation. When larvae reach the vicinity of an estuary, merging diel rhythms with feeding and predator avoidance strategies with tidally induced movements is essential to increase their chances of estuarine ingress. A fish larva recruitment model developed for the Ria Formosa lagoon supports the general framework of the SAAB hypothesis. In this model, the ingress of virtual Sparidae temperate larvae into this nursery area. increases from 1.5% to 32.1% when directional swimming guided by estuarine cues is included as a forcing parameter. (C) 2016 Elsevier Ltd. All rights reserved.
- Ecohydrology as a new tool for sustainable management of estuaries and coastal watersPublication . Wolanski, Eric; Boorman, L. A.; Chícharo, Luís; Langlois-Saliou, E.; Lara, R.; Plater, A. J.; Uncles, R. J.; Zalewski, M.Throughout the world, estuaries and coastal waters have experienced degradation. Present proposed remedial measures based on engineering and technological fix are not likely to restore the ecological processes of a healthy, robust estuary and, as such, will not reinstate the full beneficial functions of the estuary ecosystem. The successful management of estuaries and coastal waters requires an ecohydrologybased, basin-wide approach. This necessitates changing present practices by official institutions based on municipalities or counties as an administrative unit, or the narrowly focused approaches of managers of specific activities (e.g., farming and fisheries, water resources, urban and economic developments, wetlands management and nature conservationists). Without this change in thinking and management concept, estuaries and coastal waters will continue to degrade, whatever integrated coastal management plans are implemented. To help in this process of change there is a need to (1) develop a profound understanding of the effects of biota and biotic processes on mediating estuary response to changing hydrology, sediment and nutrient flux and of the biota on hydrology at the river basin scale, and (2) to develop science-based remediation measures at the river basin scale, with elements of ecohydrology and phytotechnology at their core, to strengthen the ability of the biota to sustain and adapt to human-induced stresses.
- Estuarine ecohydrologyPublication . Chicharo, Maria Alexandra Teodosio; Chícharo, Luís; Wolanski, EricThroughout the world, estuaries and coastal waters have experienced environmental degradation. Present proposed remedial measures based on engineering and technological fix have been unable to restore the ecological processes of a healthy, robust estuary and, as such, will not reinstate the full beneficial functions of the estuary ecosystem.
- Modelling the ingress of a temperate fish larva into a nursery coastal lagoonPublication . Baptista, Vânia; Leitão, Francisco; Morais, Pedro; Teodosio, Maria; Wolanski, EricThe development of sensorial acuity and swimming capabilities of coastal fish larvae and their responses to coastal nursery cues are essential for recruitment success. Most studies of the response of fish larvae to environmental cues and their recruitment into nursery areas have focused on coral reef fish and only a few studies focused on fish species from temperate regions. The Sense Acuity and Behavioural (SAAB) Hypothesis proposes that fish larvae in temperate regions can sense nursery cues and ingress into estuarine ecosystems by using several active swimming strategies. We tested the SAAB hypothesis by studying the ingress of a temperate fish larvae - white seabream Diplodus sargus (Linnaeus, 1758) - into a coastal nursery area, the Ria Formosa Lagoon, Portugal. We combined the results from studies of sensory acuity, swimming capabilities and personality traits of post-flexion larvae with a fine-scale biophysical model to quantify the ingress of the white seabream into the lagoon. Data showed that the location of spawning sites and the directional swimming capabilities are both important for the successful ingress of white seabream larvae into the lagoon. Recruitment was higher when spawning grounds were located in areas with depths between 15.1 and 16.9 m and when post-flexion larvae used their directional swimming capabilities. The larvae ingressed passively into the lagoon with the tidal currents at pre-flexion stage and actively by using their directional swimming capabilities at post-flexion stage. Directional swimming also prevented larval export into the coastal area. When spawning occurred away from the seagrass smell plume emanating from the lagoon, the fish larvae were advected away and lost at sea. This work demonstrated the relevance of combining fish larvae behaviour and oceanography processes in modelling the dispersion of fish larvae to estimate recruitment.
- Sensitivity analysis of the physical dynamics of the Fly River plume in Torres StraitPublication . Li, Yanfang; Martins, Flávio; Wolanski, EricThe intrusion in the Torres Strait of the Fly River plume polluted by mine tailings is an international water issue. To investigate the physical mechanisms involved in the intrusion process, numerical simulations were conducted to assess the relative influence of the bathymetry and the external forcing, namely the tides, the mean sea level slope across the strait, river runoff and wind forcing. The wind data from Horn Island, the only long-term wind station in the Torres Strait, is shown to be unreliable due to orographic effects. Mean sea level data from altimetry compare well with those from tide gauges in these shallow, reef-studded waters. The wind has a dominant effect on the mean sea level at seasonal and inter-annual periods. The resulting mean sea level difference across the strait fluctuated seasonally and strongly influenced the intrusion of the Fly River plume in the Torres Strait. The 3D finite-volume MOHID model reproduced the observation that the river plume starts by being stratified in the Gulf of Papua where it originates, and it mixes vertically when it enters the Torres Strait. The MOHID and the SLIM models were applied with different resolution to the Torres Strait and responded similarly to the external forcings. The predicted and observed Fly River plume intrusion in the eastern Torres Strait agreed well with each other, including the formation of patches due to flow reversals. However, the two models predicted a widely different Fly River plume in its far field in the western Torres Strait, the differences were attributed to the different bathymetry in the Australian and British-US bathymetry data for these poorly charted waters, which demonstrated the importance of the details of the bathymetry in controlling the extent of plume intrusion. (C) 2017 Elsevier Ltd. All rights reserved.
- Sustainability of future coasts and estuaries: a synthesisPublication . Newton, Alice; Harff, Jan; You, Zai-Jin; Zhang, Hua; Wolanski, EricCoasts are at the nexus of the Anthropocene, where land, marginal seas and atmosphere meet along a thin strip that is inhabited by nearly half the human population (Wolanski and Elliott, 2015). Coasts are often fringed by rich habitats such as mangroves, saltmarshes, inter-tidal mud and sand flats, seagrass meadows, kelp forests and coral reefs that provide a valuable range of ecosystem services to humans and to the adjacent marginal seas (Van den Belt and Costanza, 2011). It is the highly dynamic system that is constantly being reshaped by changing natural forces and anthropogenic activities. Coastal systems and human societies form coastal social-ecological systems that increasingly face multiple pressures, which threaten their ecological and economical sustainability. Common pressures include changes to land use and hydrology, land reclamation, coastal sand mining, harbour dredging, pollution and eutrophication, overexploitation such as overfishing, all in the context of climate change. During the 20th Century, coastal scientists studied the problems and issues arising along the coasts (Ramesh et al., 2015). Now, in the 21st Century, their focus must increasingly be about how to solve these problems and issues through better management and innovative approaches. To study these matters, two workshops were held in Yantai, P.R. China, in September 2015, hosted by the Yantai Institute of Coastal Zone Research, CAS. The outcome of these workshops is this special issue of Estuarine, Coastal and Shelf Science.