Minho Estuary Research Articles

Records from Marsh Foraminifera and Grapevine Growing Season Temperatures Reveal the Hydro-climatic Evolution of the Minho Region (nw Portugal) from 1856–2009

Abstract A hydro-climatic reconstruction is proposed for the Minho region (NW Portugal), integrating two different proxies: grape harvest dates (GHD) as a proxy of temperature variations, and benthic marsh foraminifera as a proxy of salinity of sediment interstitial waters. The reconstructed and measured mean maximum temperatures (GSTmax) of grapevine-growing season (March to August) were combined with data on benthic foraminiferal assemblages from the Caminha tidal marsh (Minho River estuary) to characterize the main hydro-climatic episodes in the region during the last 154 years. Results emphasize that, in the brackish setting of the Minho estuary, where foraminiferal species usually associated with low salinity occur, higher GSTmax had an impact on the hydrological balance of the marsh by enhancing evapotranspiration and increasing interstitial salinity. These conditions favored the occurrence of marsh species such as Jadammina macrescens and Trochammina inflata. The influence of the North Atlantic European meteorological teleconnection patterns on recent climatic variability of the Minho region was also examined from 1950–2009. Data support the hypothesis that persistent positive modes of spring-summer Scandinavian Oscillation Mode (SCA) and summer Eastern Atlantic/ Western Russia Oscillation Mode (EA/ WR) patterns triggered lower GSTmax, especially in the 1960s–1980s. Those conditions, in-phase with a positive precipitation anomaly (1958–1983), reduced the Caminha tidal marsh salinity, leading to the increase of low salinity species: Trochamminita salsa/irregularis, Haplophragmoides manilaensis, Miliammina fusca and Miliammina spp. Both proxies provide valuable tools for understanding the interactions between large-scale circulation modes and hydro-climatic conditions at regional and local scales.

Bromine soil/sediment enrichment in tidal salt marshes as a potential indicator of climate changes driven by solar activity: New insights from W coast Portuguese estuaries.

This paper aims at providing insight about bromine (Br) cycle in four Portuguese estuaries: Minho, Lima (in the NW coast) and Sado, Mira (in the SW coast). The focus is on their tidal marsh environments, quite distinct with regard to key biophysicochemical attributes. Regardless of the primary bromide (Br-) common natural source, i.e., seawater, the NW marshes present relatively higher surface soil/sediment Br concentrations than the ones from SW coast. This happens in close connection with organic matter (OM) content, and is controlled by their main climatic contexts. Yet, the anthropogenic impact on Br concentrations cannot be discarded. Regarding [Br] spatial patterns across the marshes, the results show a general increase from tidal flat toward high marsh. Maxima [Br] occur in the upper driftline zone, at transition from highest low marsh to high marsh, recognized as a privileged setting for OM accumulation. Based on the discovery of OM ubiquitous bromination in marine and transitional environments, it is assumed that this Br occurs mainly as organobromine. Analysis of two dated sediment cores indicates that, despite having the same age (AD ~1300), the Caminha salt marsh (Minho estuary) evidences higher Br enrichment than the Casa Branca salt marsh (Mira estuary). This is related to a greater Br storage ability, which is linked to OM build-up and rate dynamics under different climate scenarios. Both cores evidence a fairly similar temporal Br enrichment pattern, and may be interpreted in light of the sun-climate coupling. Thereby, most of the well-known Grand Solar Minima during the Little Ice Age appear to have left an imprint on these marshes, supported by higher [Br] in soils/sediments. Besides climate changes driven by solar activity and impacting marsh Br biogeodynamics, those Br enrichment peaks might also reflect inputs of enhanced volcanic activity covarying with Grand Solar Minima.

Effects of the invasive clam Corbicula fluminea (Müller, 1774) on an estuarine microbial community

The Asian clam Corbicula fluminea (Müller, 1774) is well recognized for its invasive behavior and high ecological and economic impacts, being classified as one of the 100 worst invasive alien species (IAS) in Europe. In this study, we performed a manipulative experiment under natural conditions to assess the effects of C. fluminea on sediments biochemistry and on the structure of an estuarine microbial (fungi and bacteria) community. We placed 5 treatments (control, rock, closed, live and open) for 2months in the Minho estuary (NW Iberian Peninsula). No differences were detected between treatments regarding the values of carbon (C), nitrite (NO2−), ammonium (NH4+), phosphate (PO43−) and calcium (Ca) in the sediments; however, potassium (K) had higher values in the open treatment. Furthermore, we found that the presence of live C. fluminea stimulated fungal biomass (but not diversity) and bacterial diversity. Bioturbation activities by C. fluminea are possibly the main mechanism explaining these results; however, other factors such as the presence of other macroinvertebrate species and/or production of feces and pseudofeces by C. fluminea cannot be excluded. To our knowledge, this is the first manipulative experiment under natural conditions that clearly shows the effects of C. fluminea on an estuarine microbial community. Given the widespread distribution of this IAS and the paucity of quantitative assessments of invasive bivalves' effects on microbial communities, it will be important that future studies further investigate these processes.

Assessing Ecological Status of Transitional and Coastal Waters; Current Difficulties and Alternative Approaches

The environmental monitoring strategy termed ecosystem-based approach (EBA) underlines the obvious benefits of managing natural resources on a holistic level, and it is particularly invoked for the rational and sustainable management of aquatic resources. However, when coming to implement EBA into monitoring schemes, such as those derived from the implementation of the European legislation concerning water quality, difficulties inherent to the complex and dynamic nature of ecosystems arise, including (i) identify appropriate, relevant and easily measurable indicators of ecosystem integrity, and (ii) combine the heterogeneous information gathered at the different levels of organization included in an ecosystem into a simple and practical decision-making scheme. The first kind of difficulties maybe partially overcome by implementing monitoring schemes which take into account the hierarchical nature of ecosystem processes and did not neglect the use of indicators at low levels of biological organization, including ecotoxicological biomarkers and bioassays. Secondly, the integration of the monitoring results into a practical decision-making scheme can best be achieved by using non metric multivariate analysis, which is especially suitable for data bases including different metrics, and allows the processing of variables showing non-monotonic response to human stress, from molecular biomarkers to community indices. The difficulties inherent to the current rigid scheme of water quality assessment heavily based on ratio-to-reference univariate indicators and arbitrary reference values and class boundaries for each single indicator are illustrated with a case study in the Minho estuary (NW Iberian Peninsula). The classification of aquatic ecosystems into discrete categories of ecological status can best be achieved by combining observations at different levels of biological organization, from molecular biomarkers to community traits, with explicative physicochemical and hydromorphological elements, and by using non-metric multivariate analysis techniques.

Principal component analysis and kinetic model adjustment to describe the community-level physiological profiles (CLPP) in the sediments of the river Minho estuary (Northern Portugal)

Principal component analysis and kinetic model adjustment to describe the community-level physiological profiles (CLPP) in the sediments of the river Minho estuary (Northern Portugal)

Zooplankton structure and dynamics in two estuaries from the Atlantic coast in relation to multi-stressors exposure

The aim of this research was to investigate the response of pelagic zooplankton to different levels of abiotic multi-stressors in the North Atlantic coast, taking advantage of the comparison of the communities of two adjacent estuaries with different levels of historical pollution (estuaries of Minho and Lima Rivers). The zooplankton community structure, composition and temporal variation were comparatively investigated for 15 months, using different net meshes. Several abiotic factors were measured in situ and water samples were simultaneously collected for determination of nutrients and chlorophyll a. The overall results revealed a diverse community represented by species that have been found in subtropical and temperate zones. Although the highest diversity was observed in the Lima estuary, supported by higher contributions of marine taxa, the total zooplankton biomass was found to be significantly higher in the Minho estuary. The salinity gradient differences between estuaries, associated to significant differences in water nutrients levels, were found to be the main forcing factors affecting micro and mesozooplankton. Considering the importance of the impacts resulting from abiotic variation on the basis of aquatic food webs, the present investigation represented a case-study, based in two contrasting estuaries, one strongly influenced by freshwater discharges (Minho estuary) and the other with higher salinity levels (Lima estuary), contributing to a better understanding of the effects of multi-stressors on pelagic zooplankton communities, providing useful information for studies related with climate change impacts, biogeography, conservation and providing data contributing to the improvement of pelagic fisheries management models.

A framework to assess the vulnerability of estuarine systems for use in ecological risk assessment

Estuaries are among the most pressured ecosystems, including by environmental contaminants resulting from anthropogenic activities, alterations due to global changes, and invasions by exotic species. The ecological risk assessment (ERA) of these pressures in complex ecosystems such as estuaries is often challenging and methods for the improvement of the process are need. Thus, the goal of the present study was to develop a general framework to assess the system vulnerability for use in the Problem Formulation phase of ERA in estuaries and other coastal ecosystems. This framework, is based on the multi-metric index approach and incorporates both inter- and intra-system analysis. It delivers information on the system's vulnerability, identifies especially vulnerable/affected zones of the system (spatial discretization) and the most critical period(s) for contamination events (temporal discretization). The framework was tested using the Minho River estuary as a case study, for both continental and offshore contamination events potentially affecting the system. The intra-system analysis revealed that the Minho estuary is the third most vulnerable system among those included in the study (nine systems of the north-west Iberian coast). The inter-system analysis was able to discriminate water-bodies with different vulnerability scores regarding existing contamination from continental origin, and offshore potential contamination events. The temporal analysis indicated July to September as the most vulnerable period in relation to both continental and offshore contamination. Thus, the application of this novel framework to the problem formulation of ERA may considerably improve the process in complex systems, such as estuaries and other coastal areas.

Comparing the Response of the Brown ShrimpCrangon crangon(Linnaeus, 1758) to Prolonged Deprivation of Food in Two Seasons

ABSTRACT Crustaceans often undergo periods of starvation, due to natural food shortage or physiological constraints. During these periods, several metabolic and behavioral changes can occur. This study evaluates how the brown shrimp Crangon crangon (Linnaeus, 1758) responds to prolonged deprivation of food in two seasons of the year, and how this species mobilizes its energetic reserves. Shrimps caught in June (summer) and October (autumn) 2010 in the Minho estuary (north of Portugal) were placed in individual cages in experimental aquaria and kept in starvation until the last shrimp died or was sacrificed (six shrimp per aquarium every week). The energetic content, total lipids and total protein, and the oxygen consumption rate were compared between seasons, sacrificed and naturally dead shrimp, and considering the weeks of starvation. Summer shrimp proved to be better prepared to endure starvation than those caught in autumn: they survived 2.5 times longer, had a higher Fulton condition factor, higher e...

Does the presence of microplastics influence the acute toxicity of chromium(VI) to early juveniles of the common goby (Pomatoschistus microps)? A study with juveniles from two wild estuarine populations

Toxicological interactions between microplastics (MP) and other environmental contaminants are of grave concern. Here, the potential influence of MP in the short-term toxicity of chromium to early juveniles of Pomatoschistus microps was investigated. Three null hypotheses were tested: (1) exposure to Cr(VI) concentrations in the low ppm range does not induce toxic effects on juveniles; (2) the presence of microplastics in the water does not influence the acute toxicity of Cr(VI) to juveniles; (3) the environmental conditions of the natural habitat where fish developed do not influence their sensitivity to Cr(VI)-induced acute stress. Fish were collected in the estuaries of Minho (M-est) and Lima (L-est) Rivers (NW Iberian Peninsula) that have several abiotic differences, including in the water and sediment concentrations of various environmental contaminants. After acclimatization to laboratory conditions, two 96h acute bioassays were carried out with juveniles from both estuaries to: (i) investigate the effects of Cr(VI) alone; (ii) investigate the effects of Cr(VI) in the presence of MP (polyethylene spheres 1–5μm ∅). Cr(VI) alone induced mortality (96h-LC50s: 14.4–30.5mg/l) and significantly decreased fish predatory performance (≤74%). Thus, in the range of concentrations tested (5.6–28.4mg/l) Cr(VI) was found to be toxic to P. microps early juveniles, therefore, we rejected hypothesis 1. Under simultaneous exposure to Cr(VI) and MP, a significant decrease of the predatory performance (≤67%) and a significant inhibition of AChE activity (≤31%) were found. AChE inhibition was not observed in the test with Cr(VI) alone and MP alone caused an AChE inhibition ≤21%. Mixture treatments containing Cr(VI) concentration ≥3.9mg/l significantly increased LPO levels in L-est fish, an effect that was not observed under Cr(VI) or MP single exposures. Thus, toxicological interactions between Cr(VI) and MP occurred, therefore, we rejected hypothesis 2. In the presence of MP, the negative effect caused by high concentrations of Cr(VI) on the predatory performance was significantly reduced in L-est fish but not in M-est fish, and Cr(VI) concentrations higher than 3.9mg/l caused oxidative damage in L-est fish but not in M-est fish. The acclimatization and test conditions were similar for fish from the two estuaries and these ecosystems have environmental differences. Thus, long-term exposure to distinct environmental conditions in the natural habitat during previous developmental phases influenced the sensitivity and responses of juveniles to Cr(VI), therefore, we rejected hypothesis 3. Overall, the results of this study indicate toxicological interactions between MP and Cr(VI) highlighting the importance of further investigating the combined effects of MP and other common contaminants.

Facilitation in the low intertidal: effects of an invasive species on the structure of an estuarine macrozoobenthic assemblage

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 522:157-167 (2015) - DOI: https://doi.org/10.3354/meps11168 Facilitation in the low intertidal: effects of an invasive species on the structure of an estuarine macrozoobenthic assemblage Adriana Novais1,*, Allan T. Souza2, Martina Ilarri3, Cláudia Pascoal1, Ronaldo Sousa1,2 1CBMA - Centre of Molecular and Environmental Biology, Department of Biology, University of Minho, Campos de Gualtar, 4710-057 Braga, Portugal 2Interdisciplinary Centre of Marine and Environmental Research (CIIMAR/CIMAR), University of Porto, Rua dos Bragas 289, 4050-123 Porto, Portugal 3ICBAS-UP – Abel Salazar Biomedical Sciences Institute, University of Porto, Rua de Jorge Viterbo Ferreira, 228, 4050-313, Porto, Portugal *Corresponding author: adriana.novais1990@gmail.com ABSTRACT: The Asian clam Corbicula fluminea (Müller, 1774) has been recognized as one of the most important invasive alien species in aquatic ecosystems and may have significant ecological and economic impacts. Recently, the presence of C. fluminea was associated with changes in benthic and epibenthic fauna. In this study, we aimed to understand the mechanisms underlying the effects of C. fluminea on an estuarine macrozoobenthic assemblage using a manipulative experiment. We used 5 different treatments (control, rock, closed, live, open), which were placed in a low sandy intertidal soft bottom area in the Minho estuary (NW Iberian Peninsula) for 2 months. We found that the presence of live and open empty shells of C. fluminea had positive effects on the density, biomass and species richness of macrozoobenthos, specifically on species belonging to Annelida, Mollusca and Crustacea. Our results may be explained by 2 main mechanisms: (1) the production of feces and pseudofeces by C. fluminea, which increases organic matter content and food resources for some macrozoobenthic species; and (2) ecosystem engineering activities by C. fluminea, which can create conditions for the establishment of other species via shell production and bioturbation in the sediments. KEY WORDS: Corbicula fluminea · Alien species · Ecosystem engineering · Invertebrates · Minho estuary Full text in pdf format PreviousNextCite this article as: Novais A, Souza AT, Ilarri M, Pascoal C, Sousa R (2015) Facilitation in the low intertidal: effects of an invasive species on the structure of an estuarine macrozoobenthic assemblage. Mar Ecol Prog Ser 522:157-167. https://doi.org/10.3354/meps11168 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 522. Online publication date: March 02, 2015 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2015 Inter-Research.

Growth and seasonal behavior of Anguilla anguilla in the River Minho tidal freshwater wetlands

Event Abstract Back to Event Growth and seasonal behavior of Anguilla anguilla in the River Minho tidal freshwater wetlands Helena Correia1, Catarina Braga2, Mário Jorge Araújo3, Allan T. Souza4 and Carlos Antunes5* 1 Universidade de Aveiro, Biologia, Portugal 2 Instituto Português do Mar e da Atmosfera, Portugal 3 CESAM, Portugal 4 CIIMAR - University of Porto, Portugal 5 CIIMAR, Portugal The River Minho estuary, located on the northwest coast of the Iberian Peninsula, is a mesotidal estuary, partially mixed that during the period of high floods it tends to evolve towards a salt wedge estuary. The influence of spring tides extends approximately 40 km upstream and the tidal freshwater wetlands (TFWs) are located in the upper 30 km. The Minho estuary is part of a Natura 2000 site, which includes the entire international section of the river being considered a very important river concerning migratory fish species. In the River Minho TFWs several fish species have ecological and economic value (Salmo trutta, Alosa fallax, Platichthys flesus, Anguilla anguilla, Salmo salar, Alosa alosa and Petromyzon marinus). European eel, A. anguilla, is in Appendix II of CITES list, that includes species not necessarily threatened with extinction, but in which trade must be controlled in order to avoid utilization incompatible with their survival. Between January 2007 and December 2014, in a selected semi-enclosed area of TFW and using 5 fyke-nets, were captured 1303 eels. All eels were measured and weighted, ocular index was determined and also marked with pit-tags and released in the same area. During these 8 years of work, around 15% of the total captured eels were recaptured once, less than 3% were recapture twice, less than 1% three times and 3 eels were recaptured 4 times. Eels marked in 2009 are until now the ones that were recaptured more times. Biological data as eel growth, seaward migration state, seasonal differences of by-catch will be crossed with abiotic data namely river flow, precipitation and water temperature. Keywords: European eel, Minho River, otoliths, mark-recapture, eel maturity Conference: XV European Congress of Ichthyology, Porto, Portugal, 7 Sep - 11 Sep, 2015. Presentation Type: Oral Presentation Topic: Life Cycles, Migration and Connectivity Citation: Correia H, Braga C, Araújo M, Souza AT and Antunes C (2015). Growth and seasonal behavior of Anguilla anguilla in the River Minho tidal freshwater wetlands. Front. Mar. Sci. Conference Abstract: XV European Congress of Ichthyology. doi: 10.3389/conf.fmars.2015.03.00119 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 22 Nov 2015; Published Online: 22 Nov 2015. * Correspondence: Dr. Carlos Antunes, CIIMAR, Porto, Please Select, 4005-123, Portugal, cantunes@ciimar.up.pt Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract Supplemental Data The Authors in Frontiers Helena Correia Catarina Braga Mário Jorge Araújo Allan T Souza Carlos Antunes Google Helena Correia Catarina Braga Mário Jorge Araújo Allan T Souza Carlos Antunes Google Scholar Helena Correia Catarina Braga Mário Jorge Araújo Allan T Souza Carlos Antunes PubMed Helena Correia Catarina Braga Mário Jorge Araújo Allan T Souza Carlos Antunes Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Integrated biomarker responses of the invasive species Corbicula fluminea in relation to environmental abiotic conditions: A potential indicator of the likelihood of clam's summer mortality syndrome

The aim of this study was to investigate the variation of several biomarkers in wild populations of Corbicula fluminea in relation to abiotic condition changes to identify environmental factors associated with increased stress in this species potentially leading to massive mortality events. The study was carried out from July to October in the freshwater tidal areas of the estuaries of Minho and Lima Rivers (NW Iberian Peninsula). Monthly, 7 biomarkers (biotransformation, energy production, anti-oxidant defenses and lipid peroxidation damages) were determined in C. fluminea and 17 abiotic parameters were determined in water or sediments in 4 sampling sites: M1, M2 and M3 in Minho (up=> downstream); and L in Lima estuaries. The results of biomarkers were integrated using the Integrated Biomarker Response (IBR), Index and also analysed in relation to environmental parameters by Redundancy Analysis (RDA). Overall, the findings of the present study indicate that July and August are particularly stressful months for the studied C. fluminea populations, especially at downstream sites; the increase of nutrients and ammonium water concentrations, water temperature and conductivity are major contributors for this increased stress; the biomarkers indicated that in July/August C. fluminea is exposed to oxidative stress inducers, environmental chemical contaminants biotransformed by esterases and glutathione S-transferase enzymes, and that organisms need additional energy to cope with the chemical and/or thermally-induced stress. The findings of the present study stress the importance of biomonitoring the health condition of C. fluminea because it may allow determining the likelihood of summer/post summer mortality syndrome in this species.

Marsh benthic Foraminifera response to estuarine hydrological balance driven by climate variability over the last 2000 yr (Minho estuary, NW Portugal)

A high-resolution study of a marsh sedimentary sequence from the Minho estuary provides a new palaeoenvironmental reconstruction from NW Iberian based on geological proxies supported by historical and instrumental climatic records. A low-salinity tidal flat, dominated by Trochamminita salsa, Haplophragmoides spp. and Cribrostomoides spp., prevailed from AD 140–1360 (Roman Warm Period, Dark Ages, Medieval Climatic Anomaly). This sheltered environment was affected by high hydrodynamic episodes, marked by the increase in silt/clay ratio, decrease of organic matter, and poor and weakly preserved foraminiferal assemblages, suggesting enhanced river runoff. The establishment of low marsh began at AD 1380. This low-salinity environment, marked by colder and wet conditions, persisted from AD 1410–1770 (Little Ice Age), when foraminiferal density increased significantly. Haplophragmoides manilaensis and Trochamminita salsa mark the transition from low to high marsh at AD 1730. Since AD 1780 the abundances of salt marsh species (Jadammina macrescens, Trochammina inflata) increased, accompanied by a decrease in foraminiferal density, reflecting climate instability, when droughts alternate with severe floods. SW Europe marsh foraminifera respond to the hydrological balance, controlled by climatic variability modes (e.g., NAO) and solar activity, thus contributing to the understanding of NE Atlantic climate dynamics.

Modeling the Minho River plume intrusion into the Rias Baixas (NW Iberian Peninsula)

The Minho River discharge is recognized as particularly important in driving the circulation and hydrography of Rias Baixas, which are highly productive fishery and aquaculture regions extremely sensitive to environmental characteristics. The intrusion of the Minho River plume inside these Rias can reverse the normal circulation pattern and affect the macronutrient concentrations, imposing a control on new production within the estuarine environment. Consequently, detailed knowledge of the propagation of the plume in this zone facilitates largely the management of many exploited and protected local species. Thus, the main purpose of this work is to study the propagation and influence of Minho estuarine plume in Rias Baixas circulation and hydrography through the development and validation of an application of MOHID numerical model including a local coastal nesting configuration fed by Minho River discharge predicted by an estuary model. The nesting configuration and the Minho estuary model were validated and then applied to research the role of the wind and Minho River discharge effects on the circulation reversal. The spring of 1998 was chosen as the validation period for Minho estuarine plume propagation, considering there were field data available for this period confirming the intrusion of the Minho River plume in Rias Baixas and reversing the normal circulation pattern. Predictions replicate accurately the hydrodynamics and thermohaline patterns in Minho estuary and Rias Baixas under these conditions showing that the developed model application reproduces the dynamics of the coupled estuarine-near coastal systems under research. Results showed that a buoyancy intrusion caused by the Minho River reverses the normal estuarine salinity longitudinal gradient and estuarine circulation of the Rias de Vigo and Pontevedra. Moreover, it was found that a continuous moderate Minho River discharge combined with southerly winds is enough to reverse the Rias Baixas circulation pattern, reducing the importance of the occurrence of specific events of high runoff values.

Assessment of the ecological quality of the Minho estuary (Northwest Iberian Peninsula) based on metal concentrations in sediments and in Corbicula fluminea

Assessment of the ecological quality of theMinho estuary (Northwest Iberian Peninsula) based on metal concentrations in sediments and in Corbicula fluminea The concentrations of metals (Cd, Cr, Cu, Fe, Ni, Pb and Zn) in sediments and the soft tissues of Corbicula fluminea from the Minho estuary (Northwest Iberian Peninsula) were determined to assess the spatial variation of metal bioavailability and to classify the ecological quality of the estuary. Metal concentrations in sediments showed significant spatial variation ( p < 0.0003) and ranged in concentration (dry weight basis) from 0.025-0.36 mg Cd/kg, 7-16 mg Cr/kg, 2.7-24.6 mg Cu/kg, 7.3-45 mg Ni/kg, 4.1-15 mg Pb/kg and 37.3-110 mg Zn/kg. According to the Norwegian Pollution Control Authority metal concentration guidelines for sediments, this first ecological quality classification of the Minho estuary is “Class I/II-Background/Good.” Metal concentrations in the soft tissues of C. fluminea also showed significant spatial variation ( p < 0.0001) and ranged in concentration (dry weight basis) from 1.1-2.5 mg Cd/kg, 1.0-1.8 mg Cr/kg, 34-71 mg Cu/kg, 5.8-11 mg Ni/kg, 0.45-1.3 mg Pb/kg and 136-161 mg Zn/kg. The high Cu concentrations bioaccumulated by C. fluminea in the Minho estuary suggest that the estuary should be classified as “Class II/III-Moderately/Remarkably Polluted.” Thus, the primary contributions of this work are that C. fluminea proved to be a good and adequate biomonitor of metal contamination in the Minho estuary and that it could be used to assess the ecological quality of estuarine ecosystems worldwide.

Population structure, production and feeding habit of the sand goby Pomatoschistus minutus (Actinopterygii: Gobiidae) in the Minho estuary (NW Iberian Peninsula)

Estuaries are highly productive and heterogeneous ecosystems, and hence they provide an excellent opportunity to study the population structure and feeding patterns of euryhaline species like the sand goby Pomatoschistus minutus. In this context the population dynamics of the sand goby was investigated during 18 months in the Minho estuary (NW Iberian Peninsula). The fish density varied significantly among estuarine areas and seasons, with most of the individuals being caught near the river mouth during the autumn (38 % of the total). Males, females and juveniles were not spatially segregated, as well as fishes belonging to different size classes. The sand goby fed mostly on crustaceans (Frequency of Occurrence - FO) = 35 %; Relative Abundance - RA = 40 %), detritus (FO = 27 %; RA = 23 %) and annelids (FO = 15 %; RA = 14 %), with no obvious difference between the diet of males and females. The density (up to 20 times) and the secondary production (up to 16 times) of the sand goby were substantially higher than in other southern European estuaries. Our results highlighted that the population dynamics of the sand goby can vary considerably among nearby systems and that the Minho estuary, probably due to the lower temperature and salinity values and also the different water circulation regime found in this system when compared to other Iberian estuaries, promotes noticeable differences on the P. minutus population dynamics.

Influence of the invasive Asian clam Corbicula fluminea (Bivalvia: Corbiculidae) on estuarine epibenthic assemblages

One of the most widespread invasive alien species (IAS) in aquatic ecosystems is the Asian clam Corbicula fluminea. Several studies have shown that C. fluminea can cause large-scale changes in macrozoobenthic assemblages; however, very few attempted to investigate the effects of this IAS on mobile epibenthic species, such as fishes and crustaceans. In this context, the influence of C. fluminea on epibenthic species was investigated during one year by comparing the associated epibenthic fauna in three nearby sites of the Minho estuary (NW of the Iberian Peninsula), wherein the abiotic conditions are similar but the density of the Asian clam is highly different. From a total of 13 species, six were significantly influenced by C. fluminea; five responded positively, namely the brown shrimp Crangon crangon, the European eel Anguilla anguilla, the common goby Pomatoschistus microps, the brown trout Salmo trutta fario and the great pipefish Syngnathus acus, whereas the shore crab Carcinus maenas was negatively influenced. However, stomach contents analysis revealed that fish and crustacean species do not feed on C. fluminea, suggesting that this IAS is still not a large component of the diet of higher trophic levels in this estuarine ecosystem. Our results suggest that the structure provided by C. fluminea shells is likely to be one of the main factors responsible for the differences observed. C. fluminea physical structure seems to influence the epibenthic associated fauna, when found in densities higher than 1000 ind./m2, with sedentary small-bodied crustaceans and fishes being mainly attracted by the increasing in habitat complexity and consequent enhancement of heterogeneity and shelter availability.

Age estimation of brown shrimp Crangon crangon: comparison of two approaches applied to populations at the biogeographic edges

In this study, 2 methods for age estimation of Crangon crangon were compared: one based on total length, the other based on the number of segments in the antennules, as suggested by Tiews' findings (1954: Ber Deut Wiss Kommiss 13:235�269). Shrimps from populations near the species' geographic edges, from Valosen Estuary (Norway) in the north and the Minho Estuary (Portugal) in the south, were used. These showed great individual variability in shrimp size growth and in antennule segment number increment, due to the presence of fast- and slow-growing shrimps in the 2 populations, implying that shrimps of different ages may have similar sizes, as well as similar segment numbers. Additionally, the origin of shrimp population, sex, length and segment number, and water temperature were found to influence growth, both in the length- and the segment-increment models, often being interacting parameters. Both methods resulted in growth curves similar to a typical von Bertalanffy growth curve. The growth rate was higher for females than for males and positively related to temperature; the maximum size was also larger for females. In contrast, maximum segment number was larger for males than for females, as has also been found by Tiews (1954). The 2 models resulted in considerably different age estimates, par- ticularly for older shrimps (i.e. shrimps of larger size or with more antennule segments). The models also suggest site-specific growth rates. Any age estimation approach will therefore need to be validated for each population.

Structure, growth and production of a remarkably abundant population of the common goby, Pomatoschistus microps (Actinopterygii: Gobiidae)

The common goby, Pomatoschistus microps, is a relevant species from estuarine food webs, playing important roles as predator of polychaetes and crustaceans and as prey for larger fishes and crustaceans. The Minho estuary (NW Portugal) is a relatively well-preserved and productive system. To assess the population structure and production of P. microps in this estuary, monthly samples were undertaken in three different areas along an estuarine gradient in the lower estuary. The density of P. microps varied considerably among seasons and sampling stations, with higher densities occurring in summer and autumn. The lowest densities were found closer to the sea. In general, the density of females was higher than the density of males in all sampling stations, while juveniles were more abundant within a salt marsh area. Compared with other European estuaries, our data showed a remarkable higher density and production values of P. microps. This may be related to the high freshwater input and the low salinities found in this estuary. In addition, we hypothesize that the lower density of the sympatric species P. minutus and the high availability of bivalve shells observed in the Minho estuary may have also contributed to the present results, once P. minutus and P. microps often display a diet overlap and the bivalve shells are crucial for the common goby reproduction.

Place branding and endogenous rural development. Departure points for developing an inner brand of the River Minho estuary

Place branding holds a promising contribution to sustainable territorial development and requires changes in the social organisation of places, which implies complex transitional processes towards new management regimes. This article explores place branding of the River Minho estuary in the borderland of Portugal and Spain. It deals with the tension between creating a brand, enhancing market development and sustainable (endogenous) development. The central question is: ‘How to develop a successful inner brand in the context of a geographically peripheral area facing severe ecological, social and economic vulnerabilities?’. In the case study, area rural dwellers, entrepreneurs and representatives of institutions represent contrasting viewpoints on innovation, ecosystem coordination and economic progress, viewpoints that point to power issues on control over the natural environment, but also provide input for the development of a common strategic vision or connective storyline. This article provides a ‘tool’ for sustainable development in this vulnerable estuary and contributes to our understanding of how place branding – as a means to create place distinctiveness and attractiveness – can be combined with an endogenous approach in vulnerable peripheral areas. Such an approach fits with the EU objectives of sustainable, inclusive and smart growth and an increasing focus on place-based development.