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1.
E. Marcelo Acha Hermes Mianzan Raúl Guerrero José Carreto Diego Giberto Norma Montoya Mario Carignan 《Continental Shelf Research》2008
The Rio de la Plata is a large-scale estuary located at 35°S on the Atlantic coast of South America. This system is one of the most important estuarine environments in the continent, being a highly productive area that sustains valuable artisanal and coastal fisheries in Uruguay and Argentina. The main goals of this paper are to summarize recent knowledge on this estuary, integrating physical, chemical and biological studies, and to explore the sources and ecological meaning of estuarine variability associated to the stratification/mixing alternateness in the estuary. We summarized unpublished data and information from several bibliographic sources. From study cases representing different stratification conditions, we draw a holistic view of physical patterns and ecological processes of the stratification/mixing alternateness. This estuary is characterized by strong vertical salinity stratification most of the time (the salt-wedge condition). The head of the estuary is characterized by a well-developed turbidity front. High turbidity constrains their photosynthesis. Immediately offshore the turbidity front, water becomes less turbid and phytoplankton peaks. As a consequence, trophic web in the estuary could be based on two sources of organic matter: phytoplankton and plant detritus. Dense plankton aggregations occur below the halocline and at the tip of the salt wedge. The mysid Neomysis americana, a key prey for juvenile fishes, occurs all along the turbidity front. A similar spatial pattern is shown by one of the most abundant benthic species, the clam Mactra isabelleana. These species could be taken advantage of the particulate organic matter and/or phytoplankton concentrated near the front. Nekton is represented by a rich fish community, with several fishes breeding inside the estuary. The most important species in terms of biomass is Micropogonias furnieri, the main target for the coastal fisheries of Argentina and Uruguay. Two processes have been identified as producing partially stratified conditions: persistent moderate winds (synoptic scale), or low freshwater runoff (interannual scale). Less frequently, total mixing of the salt wedge occurs after several hours of strong winds. The co-dominance of diatoms (which proliferate in highly turbulent environments) and red tides dinoflagellates and other bloom taxa (better adapted to stratified conditions), would indicate great variability in the turbulence strength, probably manifested as pulses. Microplankton and ichthyoplankton assemblages defined for the stratified condition are still recognized during the partially mixed condition, but in this case they occupy the entire water column: vertical structure of the plankton featuring the stratified condition become lost. Bottom fish assemblages, on the contrary, shows persistence under the different stratification conditions, though the dominant species of the groups show some variations. Summarizing, the Río de la Plata Estuary is a highly variable environment, strongly stratified most of the time but that can be mixed in some few hours by strong wind events that occur in an unpredictable manner, generating stratification/partially mixed (less frequently totally mixed) pulses all along the year. At larger temporal scales, the system is under the effects of river discharge variations associated to the ENSO cycle, but their ecological consequences are not fully studied. 相似文献
2.
Surface waters collected along the salinity gradient of the Hudson River estuary in four cruises between 1995 and 1997 were size-fractionated into particulate (>0.45 μm), ‘dissolved' (<0.45 μm), colloidal (10 kDa, 0.45 μm) and low molecular weight (<10 kDa) phases. Dissolved Cd concentrations (range: 0.11–1.19 nM) in surface waters of the estuary appear to have decreased fourfold (from an average of 2.36 to 0.61 nM) over a 23-year period, since the initial analysis of samples collected in the 1970s by Klinkhammer and Bender [Estuar. Coastal Shelf Sci. 12 (1981) 629–643]. This interannual decline reflects improvement in sewage treatment and the elimination of industrial Cd sources to the Hudson River estuary. In contrast, dissolved Mn levels (range: 0.033–1.46 μM) have remained relatively constant over the same period of time, suggesting that anthropogenic sources have very limited impact on Mn concentrations in the estuary. The concentrations of both Cd and Mn appeared to strongly depend on the season and/or river discharge. The highest concentrations were detected under low freshwater discharge, implying that limited hydraulic flushing allows a build-up of metals in the water column. Although the decline in Cd levels within the estuary reflects a reduction in the magnitude of anthropogenic inputs, mass balance estimates indicated that current sources of Cd to the estuary include sewage discharges (in the lower estuary around Manhattan) and diagenetic remobilization from industrial Cd deposited in sediments nearly 2 decades ago (in the upper estuary near Foundry Cove). Moreover, under low river discharge, the sources considered in our model (sewage, riverine input, atmospheric deposition, and benthic fluxes) could account for no more than 60% of the Cd exported from the lower estuary to the ocean. This suggests that undefined sources such as ground water and inputs from other watersheds (e.g., Long Island Sound and Newark Bay) may potentially influence the water quality of the New York Harbor. The size-fractionated metal concentrations indicated that most of the traditionally defined ‘dissolved' Cd and Mn consisted of <10 kDa molecular weight species. High molecular weight colloidal species of Mn accounted for about 50% of the dissolved fraction at the riverine end-member and <5% at intermediate and high salinities. Colloidal Cd accounted for <6% of the dissolved phase throughout the estuary. Unlike the non-conservative excess (relative to ideal dilution of river water and seawater) of dissolved Mn observed along the estuary, high molecular weight colloidal Mn appeared to be removed at the head of the estuary. The small contribution of colloidal Cd and Mn to the ‘dissolved' phase suggests that remobilization from suspended particulate phases and/or from sediments occurs through the formation of small molecular weight species. 相似文献
3.
The concentrations of PCBs in water, sediments, fish (6 species), crustacea (3 species), molluscs (1 species), polychaetes (mixed species) and birds (1 species) from the Brisbane River estuary were determined. Levels were comparable to other similar situations elsewhere. No relationship was found between trophic class and PCB concentration although pelicans at the highest trophic level examined exhibited the highest muscle tissue concentration (i.e., 15.7 mg kg−1 on a wet weight basis). The pattern of distribution of PCBs within body tissues of fish was closely related to lipid content. 相似文献
4.
Parker MacCready Neil S. Banas Barbara M. Hickey Edward P. Dever Yonggang Liu 《Continental Shelf Research》2009
A numerical simulation of circulation in the Columbia River estuary and plume during the summer of 2004 is used to explore the mixing involved as river water is transformed into shelf water. The model is forced with realistic river flow, tides, wind stress, surface heat flux, and ocean boundary conditions. Simulated currents and water properties on the shelf near the mouth are compared with records from three moorings (all in 72 m of water) and five CTD sections. The model is found to have reasonable skill; statistically significant correlations between observed and modeled surface currents, temperature, and salinity are all 0.42–0.72 for the mooring records. Equations for the tidally averaged, volume-integrated mechanical energy budget (kinetic and potential) are derived, with attention to the effects of: (i) Reynolds averaging, (ii) a time varying volume due to the free surface, and (iii) dissipation very close to the bottom. It is found that convergence of tidal pressure work is the most important forcing term in the estuary. In the far field plume (which has a volume 15 times greater than that of the estuary), the net forcing is weaker than that in the estuary, and may be due to either tidal currents or wind stress depending on the time period considered. These forcings lead to irreversible mixing of the stratification (buoyancy flux) that turns river water into shelf water. This occurs in both the plume and estuary, but appears to be more efficient (17% vs. 5%), and somewhat greater (4.2 MW vs. 3.3 MW), in plume vs. estuary. This demonstrates the importance of both wind and tidal forcing to watermass transformation, and the need to consider the estuary and plume as part of a single system. 相似文献
5.
Conceptual models of circulation theorise that the dominant forces controlling estuarine circulation are freshwater discharge from the riverine section (landward), tidal forcing from the ocean boundary, and gravitational circulation resulting from along-estuary gradients in density. In micro-tidal estuaries, sub-tidal water level changes (classified as those with periods between 3 and 10 days) with amplitudes comparable to the spring tidal range can significantly influence the circulation and distribution of water properties. Field measurements obtained from the Swan River Estuary, a diurnal, micro-tidal estuary in south-western Australia, indicated that sub-tidal water level changes at the ocean boundary were predominantly from remotely forced continental shelf waves (CSWs). The sub-tidal water levels had maximum amplitudes of 0.8 m, were comparable to the maximum tidal range of 0.6 m, propagated into the estuary to its tidal limit, and modified water levels in the whole estuary over several days. These oscillations dominated the circulation and distribution of water properties in the estuary through changing the salt wedge location and increasing the bottom water salinity by 7 units over 3 days. The observed salt wedge excursion forced by CSW was up to 5 km, whereas the maximum tidal excursion was 1.2 km. The response of the residual currents and the salinity distribution lagged behind the water level changes by ∼24 h. It was proposed that the sub-tidal forcing at the ocean boundary, which changed the circulation, salinity, and dissolved oxygen in the upper estuary, was due to a combination of two processes: (1) a gravity current generated by a process similar to a lock exchange mechanism and (2) amplified along-estuary density gradients in the upper estuary, which enhanced the gravitational circulation in the estuary. The salt intrusions under the sub-tidal forcing caused the rapid movement of anoxic water upstream, with significant implications for water quality and estuarine health. 相似文献
6.
Tweedley JR Warwick RM Valesini FJ Platell ME Potter IC 《Marine pollution bulletin》2012,64(6):1210-1221
Establishment of a benchmark against which deleterious changes to an estuary can be evaluated requires validating that it has not been subjected to detrimental anthropogenic perturbations and then identifying the biological features which are indicative of a pristine condition and can thus be employed as indicators for detecting and monitoring departures from the natural state. The characteristics of the benthic macroinvertebrate fauna of an essentially pristine, seasonally-open estuary in Western Australia (Broke Inlet) have been determined and compared with those previously recorded for a nearby eutrophic, seasonally-open estuary (Wilson Inlet). Density was far lower in Broke than Wilson. Compositions differed radically at all taxonomic levels, with polychaetes contributing less, and crustaceans more, to the abundance in Broke. Average taxonomic distinctness was greater for Broke than both Wilson and 16 other temperate southern hemisphere estuaries, whereas the reverse was true for variation in taxonomic distinctness, emphasizing that Broke Inlet is pristine. 相似文献
7.
Evidence for Systemic Changes in the Benthic Fauna of Tropical Estuaries as a Result of Urbanization
The effects of urban development cause substantial physical changes in coastal waterways through hardening and reclamation of river banks, alteration of water flow, and diffuse and point-source discharges of pollutants. The cumulative effects of urbanization on the fauna of estuaries are not well understood. This study examined the benthic infauna of two urban and three rural estuaries near Townsville, North Queensland. A range of univariate and multivariate statistics was used to relate variation in the benthic assemblages to concentrations of contaminants (heavy metals and hydrocarbons) within the sediments of each estuary. Sediments in the most developed estuary contained concentrations of heavy metals and petroleum hydrocarbons that were several orders of magnitude greater than those from non-urban waterways. The fauna at these sites was dominated by cirratulid and sternaspid polychaetes and lacked filter-feeding bivalves and other molluscs that were common in less developed estuaries. These differences were generally consistent throughout each estuary, indicating estuary-wide patterns of change, that were most strongly associated with spatial patterns in the distribution of Pb, Cu and hydrocarbons. 相似文献
8.
A preliminary survey of seven trace metals in three species of oyster from the Knysna estuary, South Africa, has been carried out. The results which were obtained indicate that this area is as yet unpolluted and provide base-line levels against which future trace-metal pollution can be measured. Two species of oyster are being grown at a number of sites as part of a long-term programme to monitor trace-metal levels in the estuary. 相似文献
9.
Abstract Researchers have used various physical, chemical, or topographic features to define estuaries, based on the needs of their particular subject. The principal features of estuaries are the tides that influence their water stages; thus, the boundaries of an estuary can be determined based on whether the water stage is subject to tidal influence. However, the water stage is also influenced by the upstream river discharge. A hydrograph of water stage will therefore include both non-stationary and nonlinear features. Here, we use the Hilbert-Huang Transform (HHT), which allows us to process such non-stationary and nonlinear signals, to decompose the water-stage hydrographs recorded at different gauging stations in an estuary into their intrinsic mode function (IMF) components and residuals. We then analyse the relationships between the frequencies of IMFs and known tidal components. A frequency correlation indicates that the water stage of the station is subject to tidal influences and is located within the estuary. The spatial distribution of the stations that are subject to tidal influences can then be used to define the estuary boundaries. We used data from gauging stations in the estuary region of Taiwan's Tanshui River to assess the feasibility of using the HHT to define an estuary. The results show that the HHT is a dependable and easy method for determining the boundaries of an estuary. Citation Chen, Y.-C., Kao, S.-P., and Chiang, H.-W., 2013. Defining an estuary using the Hilbert-Huang transform. Hydrological Sciences Journal, 58 (4), 841–853. 相似文献
10.
Long-term biological data supported by physicochemical parameters were evaluated to investigate the biodiversity of the Golden Horn Estuary from the past to the present. Limited observations dating back to 60 years ago indicated the existence of a diverse community in this small estuary. Unfortunately, in parallel with the increase in unplanned settlements and industry around the Golden Horn, pollution stress increased since the 1960s. Preliminary studies in the 1990s indicated survival of only a couple of pollution-resistant species, in the relatively cleaner lower estuary. Following the intensification of rehabilitation studies in 1998 and particularly after the opening of the floating bridge at the mid estuary; a remarkable day-by-day recovery in marine life has begun with the improving water quality. Nutrient concentrations decreased markedly; while water clarity significantly increased. Fecal coliform values decreased 10(3) fold. Phytoplankton composition changed and dense blooms of eukaryotic phytoplankters frequently occurred. Hydrogen sulfide almost completely disappeared even during the warmest periods of the year and dissolved oxygen concentrations increased. All results clearly depicted that the Golden Horn ecosystem shifted to eutrophic conditions from an anoxic environment. SCUBA dives in 2002, documented the level of diversification of life in the Golden Horn. All appropriate substratums were intensely covered by macrobenthic forms until the Halic Bridge and filter feeders dominated the plankton-rich ecosystem. Achieving the diversity of 1940s is not possible since the Black and Marmara seas, influencing water quality of the Golden Horn, are also suffering from anthropogenic impacts and are far less diverse than their rich diversity in 1940s. However, the Golden Horn is a good example that even the most polluted ecosystems can recover when appropriate measures are taken. 相似文献
11.
– Five aquatic ecosystems, Yamuna river, Krishna river Eastern Kalinadi, Kadrabad drain and Peacock lake have been studied with reference to diversity and physico-chemical characteristics and biological indices. – A list of species have been selected with reference to polluted, mildly polluted or unpolluted water conditions. Though it is difficult to call any species strictly indicator species, certain species of Bacillariophyceae, bottom biota and Entomostraca can be regarded as indicative species. – The quantitative distributions of the species of different groups have been analysed statistically. Margalef's Community Diversity Index (d), Shannon Weaver Function, coefficient of rank correlation and partial and multiple correlation coefficient were calculated as to find out the order of precedence in different taxonomical groups. – The linear regression against BOD and the whole biocenosis were calculated, which indicate the relation as diversity d=6.7854 –0.0080 BOD±0.9695 where r2= B=0.7365. Similarly, multiple linear regressions were also calculated using diversity against BOD, pH and temperature for each aquatic ecosystem. – All these observations indicate that diversity of organisms can be used to measure the water pollution intensity. 相似文献
12.
The use of living plants for mechanical-technical purposes (stabilization by plants) in the field of design and construction in the sense of biological engineering – a field of application of ecological engineering – concerns a complex system in which factors of soil mechanics and hydraulics are combined with the ecosystem. In comparison with solid-technical construction methods, considerable advantages result due to a lower expenditure for maintenance and a high stability, especially during floods. Findings having been gained so far concerning the stabilization of the bank toe by underwater plants and flooding forms of species of reeds communities, the stabilization in the range of the mean water level and above it by bushes and shrubs – in cases of long-time submerging by species of the reeds and swamps of large sedge (Phragmites) and of the wet meadows (Molinietalia) are critically evaluated, with the inclusion of new own findings from plantings in a newly developed section of the Branitz inland ditch (initial plantings in water and at the lower part of the bank) which have been observed for some years and from reed plantings covering large areas in the pond region of Peitz (Cottbus county, south-eastern part of the GDR). 相似文献
13.
Water and sediment dynamics at Saint Lawrence River mouth 总被引：1，自引：0，他引：1
The main features of the hydrological regime and morphological structure of the estuarine-type mouth area of the Saint Lawrence River are considered. Data on the structure of water masses, thermal and ice regimes in the Gulf of Saint Lawrence, which has a significant effect on the estuary, are given. The major attention is paid to water mixing processes, water and sediment dynamics in the estuary under the joint effect of river runoff and tides, and as a function of bed topography. The parameter determining the type of water stratification and circulation is discussed. The effect of the Coriolis force on the stratified flow in the estuary and formation of the geostrophic current is discussed. 相似文献
14.
Wavelet-based characterization of water level behaviors in the Pearl River estuary, China 总被引：1，自引：0，他引：1
Qiang Zhang Chong-Yu Xu Yongqin David Chen 《Stochastic Environmental Research and Risk Assessment (SERRA)》2010,24(1):81-92
In this paper, we analyzed the high/low water levels of eight stations along the Pearl River estuary and the high/low tidal
levels of Sanzao station, and streamflow series of Sanshui and Makou stations using wavelet transform technique and correlation
analysis method. The behaviors of high/low water levels of the Pearl River estuary, possible impacts of hydrological processes
of the upper Pearl River Delta and astronomical tidal fluctuations were investigated. The results indicate that: (1) the streamflow
variability of Sanshui and Makou stations is characterized by 1-year period; 1-, 0.5- and 0.25-year periods can be detected
in the high tidal level series of Sanzao station, which reflect the fluctuations of astronomical tidal levels. The low tidal
level series of Sanzao station has two periodicity elements, i.e. 0.5- and 0.25-year periods; (2) different periodicity properties
have been revealed: the periods of high water levels of the Pearl River estuary are characterized by 1-, 0.5- and 0.25-year
periods; and 1-year period is the major period in the low water levels of the Pearl River estuary; (3) periodicity properties
indicate that behaviors of low water levels are mainly influenced by hydrological processes of the upper Pearl River Delta.
High water levels of the Pearl River estuary seem to be affected by both hydrological processes and fluctuations of astronomical
tidal levels represented by tidal level changes of Sanzao station. Correlation analysis results further corroborate this conclusion;
(4) slight differences can be observed in wavelet transform patterns and properties of relationships between high/low water
levels and streamflow changes. This can be formulated by altered hydrodynamic and morphodynamic processes due to intensifying
human activities such as construction of engineering infrastructures and land reclamation. 相似文献
15.
Larval fish assemblages in a tropical mangrove estuary and adjacent coastal waters: Offshore-inshore flux of marine and estuarine species 总被引：1，自引：0，他引：1
A total of 92,934 fish larvae representing 19 families were sampled monthly from the Sangga Kecil estuary (Matang Mangrove Forest Reserve) and adjacent coastal waters from May 2002 to October 2003. Larval fish assemblages were numerically dominated by Gobiidae (50.1%) and Engraulidae (38.4%). Canonical Correspondence Analysis (CCA) revealed that the larval fish assemblages, including their ontogenetic stages, differed between the mangrove estuary and adjacent offshore waters, and that salinity, turbidity and zooplankton food are the major environmental factors structuring the larval fish assemblages. Estuarine preflexion gobiid larvae were ubiquitous in the coastal and estuarine waters. Larval stages of euryhaline species that were spawned in offshore waters, such as Engraulidae and Clupeidae, were largely advected into mangrove areas at the postflexion stages. Larvae of other euryhaline fishes (Sciaenidae, Blenniidae and Cynoglossidae) that may have been spawned inside the estuary were, however, exported to offshore waters. Given that the collective number of juvenile and adult fish families in the Matang estuary was 53, while the number of larval families was only 17, the former is quite disconnected from the existing larval fish population in the estuary. 相似文献
16.
The EC Water Framework Directive requires that ecological quality be assessed in transitional waters using the abundance and species composition of macroalgae. In estuaries, which form the majority of transitional waters, species composition is not a suitable measure. This arises from two features: (i) there is a continuous, natural change in species composition along the gradient of estuarine conditions which makes it difficult to know where within an estuary the species composition should be assessed, (ii) the inner estuarine macroalgal community of mat-forming species is very tolerant to both natural and anthropogenic stress and species poor which makes it insensitive to environmental variations in terms of species composition. An alternative feature is proposed based on the extent of upstream penetration of perennial fucoid algae. This proposal is founded on a series of case studies of the changes in fucoid limits, within a number of estuaries in the British Isles, consequent upon changes in pollution status over the last three decades. This also has to take into account variations of fucoid penetration owing to natural factors such as range of salinity variation and turbidity. The abundance criterion is taken to mean the absence of macroalgal blooms or "green tides", because general abundance of species is hard to quantify meaningfully in the upper estuarine mat-forming species and in the lower estuary is subject to great variation owing to the physical variability of estuary types. 相似文献
17.
《国际泥沙研究》2020,35(4):417-429
The aim of the current study was to determine the nature of the seasonal variability of the Suspended Particulate Matter (SPM) fluxes from the drainage basin to the estuary in a macrotidal region (Northeastern Brazil), and the estuarine response to a seawater intrusion regarding sediment deposition, which will support the understanding of the global transport of materials at the continent-ocean interface. Thermohaline structure data was acquired using a Conductivity, Temperature, and Depth (CTD) probe with a sampling frequency of 4 Hz. Suspended particulate material was measured by gravimetric measurements applied to exact filtered volume samples. The outflows were measured through the use of an Acoustic Doppler Current Profiler (ADCP) with frequency of 1.5 MHz. The horizontal thermal and saline gradients varied from warmer and less saline waters (2014) to cooler and saline waters (2015). The gradient behavior when linked to volume transport and SPM flows, suggests a minimization of the fluvial flows in 2015, easing the advance of coastal water (CW) towards the inner estuary, leading to an inversion of the baroclinic pressure gradient. The bottom saline front, generated by the entrance of coastal water masses, caused an increase in SPM concentrations due to increased fluid density, resuspension of previously deposited sediment, and erosion of banks. High concentrations of SPM indicate higher volume transport suggesting a hydraulic barrier due to the change/inversion of the baroclinic pressure gradient, resulting in water and material retention. Material deposition was observed during neap tide, while during spring tide the material is resuspended, increasing the concentration, generating cycles of deposition and erosion during the neap-spring tides. The sediment in suspension that reach the estuary, even with low fluvial volume, stay in this environment forming new islands because of deposition. High deposition rates or sediment cycling, if generated by the hydraulic barrier, may indicate that the flows of SPM from the continental drainage to the estuary and adjacent continental shelf are interrupted and the residence time is increased. 相似文献
18.
Hexachlorocylcohexanes (HCHs) are pesticides that persist in air and water of the Northern hemisphere. To understand the spatial and temporal variability in HCH levels in estuarine surface waters we measured concentrations of two HCH isomers (-HCH and γ-HCH) at six sites in the York River estuary at bimonthly intervals for a year. Bacterial abundance and activity were also monitored using acridine orange direct counts and uptake of tritiated substrates, respectively. -HCH was consistently observed to be significantly higher in marine water compared to river water entering the estuary, suggesting that the Chesapeake Bay or Atlantic Ocean is a larger source of this compound to the York River estuary compared to riverine input. Moreover, following periods of high freshwater flow into the estuary during spring and early summer, both - and γ-HCH mixing curves indicated an additional source of these pollutants to the estuary such as land-derived runoff or groundwater discharge. In contrast, during low freshwater flow (late summer and fall) the estuary was a sink for HCHs, with γ-HCH more rapidly removed from the estuary than -HCH. During the period of low freshwater flow, concentrations of both - and γ-HCH were negatively correlated with bacterial activity. Bacterial activity as opposed to abundance appears to control HCH degradation in estuarine surface waters. 相似文献
19.
Ecological status assessment in the lower Eo estuary (Spain). The challenge of habitat heterogeneity integration: a benthic perspective 总被引：2，自引：1，他引：1
The implementation of the European Water Framework Directive (WFD) requires evaluation of the ecological status (ES) of benthic communities in coastal and transitional water systems, and the intercalibration of assessment methodologies therefore becomes a research challenge. Our aim was to test the suitability of applying the M-AMBI index to assess the status of the Eo estuary (northern coast of Spain). Our results showed that M-AMBI was influenced by the natural variability of benthic communities, and presented an apparent dependence on habitat characteristics. Consequently, the definition of homogeneous areas in transitional water systems should be based on the salinity gradient combined with other factors. To achieve an accurate ES assessment, habitat-specific reference conditions should then be defined prior to the application of M-AMBI; this necessitates dividing an estuary into several sections, which may be classified as different ESs. From this perspective, a novel approach to integrate habitat heterogeneity in a global ES assessment was tested. 相似文献
20.
Guillermo Aravena Fernando Villate Arantza Iriarte Ibon Uriarte Berta Ibáñez 《Continental Shelf Research》2009
The effect of the North Atlantic Oscillation (NAO) indices on climatic conditions and their subsequent influence on water temperature of two Basque estuaries (estuary of Bilbao and estuary of Urdaibai) were assessed by transfer function (TF) models for the period 1997–2006. Results showed that air temperature had an immediate (lag=0) and significant negative response to the NAO, whereas rainfall was not correlated with this climate index. The negative correlation between NAO and air temperature was found to be stronger with the seasonal indices derived from the differences in surface pressure between Iceland and Azores than with that derived from the principal component time-series of the leading eigenvector of the sea-level pressure in an Atlantic sector. The correlations between rainfall and river discharge, and between air temperature and water temperature were positive and highly significant in both estuaries. The response of water temperature to air temperature was immediate in both estuaries, whereas one-quarter lagged responses were also observed in the estuary of Bilbao, which is deeper and more stratified than the estuary of Urdaibai. Our study provides evidence that on the Basque coast the NAO plays an important role in climate variations, which in turn affect estuarine water temperature. 相似文献