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Abstract Background Three-axis acceleration sensor acoustic transmitters (AccelTag) programmed to identify specific acceleration patterns associated with particular behaviours (e.g., burrowing, attack) were used to study some aspects of the ecology of the Lusitanian toadfish Halobatrachus didactylus (Bloch & Schneider 1801). The AccelTag combines the features of archival tags (records acceleration in all three directions measuring also roll-independent pitch/tilt angle and roll around the fish’s axis) and acoustic transmitters. Therefore, this tag can autonomously identify and record specific signatures (i.e., behaviour patterns) of different movements transmitting autonomously and periodically the data to an acoustic biotelemetry receiver. Lusitanian toadfish is a subtropical marine teleost confined to estuaries in its northern limit of distribution due to thermal constraints. During 2010 (August and October), 24 toadfish were captured, tagged with the AccelTag and released in the Mira estuary, SW coast of Portugal, where an array of underwater automatic acoustic biotelemetry receivers was deployed. Results Around 40% of AccelTag transmissions from tagged fish that stayed in the study area were logged by the acoustic receiver array. The Lusitanian toadfish exhibited low activity during late summer and early autumn (

Background: Three-axis acceleration sensor acoustic transmitters (AccelTag) programmed to identify specific acceleration patterns associated with particular behaviours (e.g., burrowing, attack) were used to study some aspects of the ecology of the Lusitanian toadfish Halobatrachus didactylus (Bloch & Schneider 1801). The AccelTag combines the features of archival tags (records acceleration in all three directions measuring also roll-independent pitch/tilt angle and roll around the fish's axis) and acoustic transmitters. Therefore, this tag can autonomously identify and record specific signatures (i.e., behaviour patterns) of different movements transmitting autonomously and periodically the data to an acoustic biotelemetry receiver. Lusitanian toadfish is a subtropical marine teleost confined to estuaries in its northern limit of distribution due to thermal constraints. During 2010 (August and October), 24 toadfish were captured, tagged with the AccelTag and released in the Mira estuary, SW coast of Portugal, where an array of underwater automatic acoustic biotelemetry receivers was deployed. Results: Around 40% of AccelTag transmissions from tagged fish that stayed in the study area were logged by the acoustic receiver array. The Lusitanian toadfish exhibited low activity during late summer and early autumn (< 3% of time active). The tidal stage and time of day were important factors that influenced the species behaviour and activity. Increased burrowing and re-burrowing movements were registered during spring tides, while attacks prevailed on neap tides and during the night. The tidal cycle only influenced toadfish behaviour and activity in interaction with time of day, with more attacks and higher levels of activity during nocturnal high tides. Conclusions: Higher activity levels and attacks displayed by the Lusitanian toadfish during the night, at high tide periods and during Spring tides are considered to be associated with increased activity and vulnerability of its prey during these periods. The AccelTag proved to be a powerful tool to assess and monitor the activity and fine-scale behaviour of fish in situ. This technology is particularly suited for fish species with biological and ecological features similar to Lusitanian toadfish, i.e., resident species with low activity levels and behaviours with a distinct 3D acceleration signature. [ABSTRACT FROM AUTHOR]

The present study aims to research the physico-chemical processes in two under-researched coastal systems located on the west and south Portuguese coast—Mira Estuary and Ria de Alvor—through the development and exploitation of dedicated coupled physical and water quality models. Both systems are highly dynamic, supporting a wide range of biological diversity; however, they are characterized by distinct environmental and oceanographic conditions, enhancing the importance of a comparative approach. In this context, the Delft3D modeling suite was implemented and successfully calibrated and validated for both systems, accurately reproducing their hydrodynamic, hydrographic, and chemical features. A broad characterization of Mira Estuary and Ria de Alvor was carried out. Results show that the tidal wave interacts differently with the different geomorphology of each estuary. The tidal wave amplitude decreases as it propagates upstream for both estuaries; however, the magnitude for Ria de Alvor is higher. A flood tidal dominance was found for Mira Estuary, allowing the transport of well-oxygenated water into the estuary, contributing to high residence times in the middle estuary and therefore to poor dissolved oxygen (DO) replenishment. Ria de Alvor shifts from ebb dominance at the central area to flood dominance upstream with low residence times, allowing an effective exchange of water properties. Results also reveal that the water temperature is the dominant driver of seasonal dissolved oxygen variations in both estuaries, with the lowest levels occurring during the late summer months when the water temperature is highest. In addition, pH is influenced by biological activity and freshwater inflow.

Blackfordia virginica , a non-indigenous hydrozoan introduced in many systems around the world, has been observed in the Mira estuary, southwest of Portugal, since 1984. Monthly sampling (January 2013–January 2014) at a fixed location with high abundance of the medusae confirmed the occurrence of a seasonal cycle associated with temperature and photoperiod. The beginning of the medusa cycle occurred in May immediately after the spring zooplankton bloom during April. Examination of the gut contents of B . virginica medusae revealed that copepods, the most abundant group in the zooplankton community, were highly predated. Barnacle nauplii, decapod crustacean larvae and anchovy eggs were also identified in the guts. The medusae showed positive selection for copepods, and negative selection for barnacle nauplii, decapod crustacean larvae and anchovy eggs. The mortality rate of copepods (used as a model prey group) induced by medusae predation was estimated and showed the potential impact of this species in the ecosystem, ranging between 2.34 d −1 and 0.02 d −1 , with a minimum copepod half-life of 0.30 days. [ABSTRACT FROM AUTHOR]

Complex toxicant mixtures present in estuarine sediments often render contaminant screening unfeasible and compromise determining causation. HepG2 cells were subjected to bioassays with sediment extracts obtained with a series of progressively polar solvents plus a crude extract. The sediments were collected from an impacted area of an estuary otherwise regarded as pristine, whose stressors result mostly from aquaculture effluents and hydrodynamic shifts that enhance particle deposition. Compared to a reference scenario, the most polar extracts yielded highest cytotoxicity while higher genotoxicity (including oxidative damage) was elicited by non-polar solvents. While the former caused effects similar to those expected from biocides, the latter triggered effects compatible with known pro-mutagens like PAHs, even though the overall levels of toxicants were considered of low risk. The results indicate that the approach may constitute an effective line-of-evidence to infer on the predominant set of hazardous contaminants present in complex environmental mixtures. [Copyright &y& Elsevier]

The brackish water amphipod Corophium orientale is the dominant macroinvertebrate species in the upper Mira estuary, a small mesotidal system located in the southwest coast of Portugal. As climate changes will increase the frequency and intensity of extreme events such as floods and droughts, these will have a negative effect on benthic estuarine invertebrates, namely C. orientale. In order to understand the effects of these events on C. orientale, a dynamic model, based on published information and calibrated with field data, was developed and different scenarios were tested. For model construction, the annual development of three cohorts of C. orientale, their growth rates, and the establishment of the timing of each cohort rise and extinction are introduced. This structure can be repeated indefinitely, for years, and few parameters are required. The model simulations highlight the need for refuge areas that enable a fast recovery of the amphipod population after an extreme event and the recolozination of the affected areas. [Copyright &y& Elsevier]

Abstract: Settlement patterns of decapod crustaceans are influenced by size, shape and nature of substrates, as well as by species-specific behaviour patterns. Hog''s hair filter material is one of the most commonly used artificial substrates in the study of settlement rates. However, the use of hog''s hair collectors in settlement studies poses several problems: movement restriction of settled animals, relatively long and complicated laboratory processing time, and cost and decreasing availability. Despite widely used, no consistent investigation has focused on the influence of size and shape of hog''s hair collectors on rates of benthic settlement. A first experiment was set to investigate the effects of collector patchiness on settlement abundances of Carcinus maenas megalopae. Benthic hog''s hair collectors of different sizes were deployed intertidally in the lower Mira Estuary. Settlement was addressed as ind collector−1 and ind m−2 in relation to collector'' surface area and perimeter:area ratio. Results showed that collector patchiness significantly influenced settlement response of C. maenas megalopae, which differed according to settlement intensity and measure. Megalopae settlement responded to lower scales of habitat patchiness at high than at low intensity. Settlement as ind collector−1 generally increased, while as ind m−2 generally decreased, with increasing collector'' surface area (decreasing perimeter:area ratio). A second experiment investigated the efficiency of plastic grass, as a new type of artificial surface, in estimating settlement patterns of C. maenas megalopae, and compared it with that of hog''s hair. Collectors of both types were deployed daily and intertidally in the lower Mira Estuary. Settlement showed the same pattern and intensity on both collector types. Plastic grass collectors constitute a good alternative to those of hog''s hair, possessing several advantages over them. [Copyright &y& Elsevier]

Abstract: Settlement is a critical process in the life history of crabs, and thus affecting the abundance, distribution and structure of estuarine communities. The spatial pattern of settlement of megalopae of the shore crab Carcinus maenas along a longitudinal estuarine gradient (Mira River Estuary, Portugal) was examined, as well as its effects on the juvenile population. To measure megalopal settlement, four replicate collectors were deployed in six equally spaced stations along the estuarine axis. Juveniles were collected on the same locations with a quadrat randomly deployed on the substrate. To assess fine-scale megalopal settlement within a curved region of the estuary, replicate collectors were deployed on both margins along Moinho da Asneira curve. Megalopae settled differently along the six longitudinal points, with a tendency to attenuate their settlement upstream. Within the curved region, megalopae preferentially settled on the left margin collectors, probably due to the weaker velocity speeds felt on this margin. Concerning the overall juvenile density, there were significant differences among the stations distributed along the estuary, but they did no reflect a longitudinal dispersion attenuation pattern. Size-frequency distribution of the juvenile population showed that the average size is higher on the left margin. Recruits (carapace length between 1.0mm and 3.4mm) were more abundant on the upstream stations. Density of early juveniles (3.4mm–6.5mm) and juveniles (6.5mm–10mm) was more stable throughout the estuary axis than that of recruits. This distribution pattern may result from tidal excursion processes or mechanisms to avoid biotic interactions, such as predation and competition. [Copyright &y& Elsevier]

The feeding activity of the Liza ramada population inhabiting the Mira estuary (Portugal) is reduced during the winter and summer months. At the beginning of the spawning migration (i.e. November) an increase in the amount of food ingested was noticed. In the upper estuary, the feeding behaviour is independent of the tidal cycle, although there is some evidence of a daily rhythm in the food consumption rate, with a reduction during the night. No significant correlation was found between the quantity of particulate organic matter and the concentration of microalgae present in the stomach contents, and it seems that the bulk of the organic matter ingested by the thin-lipped grey mullets comes from a different origin than planktonic or benthic microalgae. The L. ramada population showed a positive selection for sediment particles between 55 and 250 μm in diameter. In general, the diet composition of this species showed a low diversity of food items. A total of 52 food items were identified in the stomach contents, the Bacillariophyceae being the dominant group. The genera Melosira and Ciclotella were the most common and abundant food items, although the genera Navicula, Nitzschia and Surirella were also classified as preferential food items. It was found that the volume of ploughed sediment that resulted from the feeding activity of the thin-lipped grey mullets, and the correspondent disturbed area increased exponentially with the length of the fish. [Copyright &y& Elsevier]

The present study aims to research the physico-chemical processes in two under-researched coastal systems located on the west and south Portuguese coast—Mira Estuary and Ria de Alvor—through the development and exploitation of dedicated coupled physical and water quality models. Both systems are highly dynamic, supporting a wide range of biological diversity; however, they are characterized by distinct environmental and oceanographic conditions, enhancing the importance of a comparative approach. In this context, the Delft3D modeling suite was implemented and successfully calibrated and validated for both systems, accurately reproducing their hydrodynamic, hydrographic, and chemical features. A broad characterization of Mira Estuary and Ria de Alvor was carried out. Results show that the tidal wave interacts differently with the different geomorphology of each estuary. The tidal wave amplitude decreases as it propagates upstream for both estuaries; however, the magnitude for Ria de Alvor is higher. A flood tidal dominance was found for Mira Estuary, allowing the transport of well-oxygenated water into the estuary, contributing to high residence times in the middle estuary and therefore to poor dissolved oxygen (DO) replenishment. Ria de Alvor shifts from ebb dominance at the central area to flood dominance upstream with low residence times, allowing an effective exchange of water properties. Results also reveal that the water temperature is the dominant driver of seasonal dissolved oxygen variations in both estuaries, with the lowest levels occurring during the late summer months when the water temperature is highest. In addition, pH is influenced by biological activity and freshwater inflow. [ABSTRACT FROM AUTHOR]

Organotin compounds, including tributyltin (TBT), are a class of themost toxic xenobiotics occurring in aquatic systems. High concentration levels in waters and sediments are mainly due to their extensive use as biocides and high persistence when present in sediments under anaerobic conditions. Toxicity studies have revealed the acute effects of TBT for aquatic organisms at concentrations as low as 1 mug/L, and the induction of imposex at levels below 0.5 ng/L TBT (as Sn). At 20 ng/L TBT (as Sn) causes sterility and is followed with the disappearance of the most sensitive neogastropods on a given shore. Imposex is the most sensitive response of all known pathological conditions for nontarget organisms following an exposure to tributyltin. In this study results are discussed that were obtained from two monitoring sites with different anthropogenic background using imposex monitoring as an indicator of TBT concentrations, as well as chemical analysis of tissue of Hinia (=Nassarius) reticulata (L.) (Gastropoda). [ABSTRACT FROM AUTHOR]