Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Estuaries”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed2001

Hepatic 7-ethoxyresorufin O-deethylase activity in eel (Anguilla anguilla) from the Thames Estuary and comparisons with other United Kingdom Estuaries.

Hepatic microsomal 7-ethoxyresorufin O-deethylase (EROD) activities (indicative of exposure to polycyclic aromatic hydrocarbons (PAHs) and polychlorobiphenyls (PCBs)) were measured in eel Anguilla anguilla from the Thames Estuary. Fish were collected from up to 13 sites during November 1997, May and August 1998 and October 1999. Throughout this period no clear seasonal variation could be identified at every site along the Thames. However, during the summer months, fish sampled from sites in the middle to the upper estuary (Woolwich, Greenhithe and West Thurrock) reported up to 3-fold higher EROD activities compared to sites either at the upper reaches (Richmond and Brentford) at the same time of the year, or fish sampled in winter, along the entire length of the estuary. A laboratory exposure experiment demonstrated a 3-fold elevation of EROD activity 2 days after injection with beta-naphthoflavone (beta-NF). However, higher levels of activity could be determined in fish sampled from the Weston canal near the Merseyside. The lowest levels of A. anguilla EROD activity were observed in fish sampled from the upper reaches of the River Tamar, Devon, and were comparable to activities determined in fish from the Wear and Humber estuaries. A. anguilla sampled along the Thames, Tyne and Tees estuaries reported between 2.5- and 7-fold higher EROD activities compared to fish collected from the Tamar. These results indicate that a low to moderate induction of A. anguilla CYP1A had occurred (indicative of low to moderate exposure to PAHs and planar PCBs) in fish collected from the Thames, Tyne, Wear, Tees, Humber and Tamar estuaries. However, the highest level of EROD activity was observed in fish from the Weston Canal (Merseyside).

Anguilla↗
PubMed2004

Dissolved and particulate fluxes of copper through the Morlaix river estuary (Brittany, France): mass balance in a small estuary with strong agricultural catchment.

Dissolved and particulate copper were measured over an annual cycle (12 surveys between February 1998 and January 1999) in the Morlaix Estuary (Brittany, France). These variations were investigated in both the water column and the benthic compartment in order to calculate fluxes of copper within estuary. In the water column, dissolved and particulate copper concentrations ranged from 0.6 to 19.0 nM and from 0.03 to 2.3 micromol g(-1), respectively. In the benthic compartment, copper concentrations in superficial sediment varied from 0.04 to 0.32 micromol g(-1) and from 7.6 to 80.5 nM in the pore waters. The results show that copper contents in the water column reached levels commonly observed in estuaries affected by heavy industrial activities. Agricultural activities, extensively developed on the drainage basin, may be responsible for the copper excess. Mass balance of copper indicates that the metal accumulated within the estuary with a rate ranging from 97 to 119 kg yr(-1).

Agriculture↗
PubMed2001

Seasonal variation and estradiol-dependent elevation of Thames estuary eel Anguilla anguilla plasma vitellogenin levels and comparisons with other United Kingdom estuaries.

Eel Anguilla anguilla plasma vitellogenin was investigated as a biomarker of exposure to environmental compounds with estrogenic activity, along the tidal course of the Thames Estuary, UK. A. anguilla was chosen as a sentinel species because of their wide distribution, robustness in field and laboratory studies and also because they have a characterised normal intersex' condition where the gonad contains both developing male and female gonadal cells termed a Syrski organ. Following laboratory exposure to 17beta-estradiol (intraperitoneal injection), a plasma protein (approx. 211 kDa apparent molecular weight) was detected by monoclonal antibodies to vitellogenin of striped bass (Morone saxatilis). Western and dot blot analyses were developed and vitellogenin was isolated from 17beta-estradiol-treated fish to calibrate the quantification of the blots by image analysis. The limits of sensitivity for the Western and dot blots were 100 and 10 ng vitellogenin/ml, respectively. Levels of vitellogenin in Thames estuary samples were below the detection limits of the Western but not the dot blot, and showed no statistically significant site-specific (10 sites) and seasonal-specific (May, August, November) differences. Values were observed to be low, between 11 and 165 ng/ml, compared with 17-50 mg/ml for 17beta-estradiol-treated eels. Similar low levels of plasma vitellogenin were determined in fish sampled along the Tyne, Wear, Tees or Humber estuaries, or the Weston canal Liverpool, with mean plasma vitellogenin levels varying between 44 and 82 ng/ml. These levels of vitellogenin in A. anguilla plasma were observed to be consistent with the known biology of the eel. Immature females, or fish with syrski organs, reported both lower levels and smaller variation of plasma vitellogenin concentrations whereas the highest plasma vitellogenin concentrations were determined in fish above 45 cm consistent with female fish. These results indicate inter-species variation between the plasma vitellogenin concentrations of A. anguilla and other published fish studies undertaken along the same estuaries.

Anguilla↗
PubMed2006

Assessing the effects of nutrient management in an estuary experiencing climatic change: the Neuse River Estuary, North Carolina.

Eutrophication is a serious water quality problem in estuaries receiving increasing anthropogenic nutrient loads. Managers undertaking nutrient-reduction strategies aimed at controlling estuarine eutrophication are faced with the challenge that upstream freshwater segments often are phosphorus (P)-limited, whereas more saline downstream segments are nitrogen (N)-limited. Management also must consider climatic (hydrologic) variability, which affects nutrient delivery and processing. The interactive effects of selective nutrient input reductions and climatic perturbations were examined in the Neuse River Estuary (NRE), North Carolina, a shallow estuary with more than a 30-year history of accelerated nutrient loading and water quality decline. The NRE also has experienced a recent increase in Atlantic hurricanes and record flooding, which has affected hydrology and nutrient loadings. The authors examined the water quality consequences of selective nutrient (P but not N) reductions in the 1980s, followed by N reductions in the 1990s and an increase in hurricane frequency since the mid-1990s. Selective P reductions decreased upstream phytoplankton blooms, but increased downstream phytoplankton biomass. Storms modified these trends. In particular, upstream annual N and P concentrations have decreased during the elevated hurricane period. Increased flushing and scouring from storms and flooding appear to have enhanced nutrient retention capabilities of the NRE watershed. From a management perspective, one cannot rely on largely unpredictable changes in storm frequency and intensity to negate anthropogenic nutrient enrichment and eutrophication. To control eutrophication along the hydrologically variable freshwater-marine continuum, N and P reductions should be applied adaptively to reflect point-source-dominated drought and non-point-source-dominated flood conditions.

Biomass↗
PubMed1995

Trace metals in sediments of a Mediterranean estuary affected by human activities (Acheloos river estuary, Greece).

Trace metals were studied in the sediments of the ecologically, economically and scientifically important estuary of the Acheloos river, in western Greece. Human activities (dams, agriculture, traffic, etc.) influence the estuarine system of Acheloos and in combination with the hydrological, mineralogical and morphological characteristics of the estuary affect the chemical behaviour and the distribution patterns of trace metals in its sediments. The large scale disturbance of the system is imminent in the near future as it is planned to divert approximately 50% of the river water. A study of the distribution patterns of trace metals revealed that in the estuary there are zones with different metal levels. The concentrations of most metals (Al, Fe, Cu, Ni, Zn) are elevated in three of these zones (upstream, sill, seawards). A different behaviour was observed for Mn due to its association with carbonates that were observed in significant concentrations throughout the estuarine zone. A sequential extraction procedure, applied to the sediments, indicated low percentages of easily exchangeable metals, increased mobility of Cu and Zn and increased association of Ni, Cr and Fe with the aluminosilicate lattice. Although the river is not considered to be heavily polluted, some metals have shown an enrichment in the surface sediments as a result of general anthropogenic activities not derived from point sources.

Aluminum↗
PubMed1987

Trimethylarsine oxide in estuary catfish (Cnidoglanis macrocephalus) and school whiting (Sillago bassensis) after oral administration of sodium arsenate; and as a natural component of estuary catfish.

Oral administration of sodium arsenate to estuary catfish (Cnidoglanis macrocephalus) and school whiting (Sillago bassensis) resulted in an accumulation of trimethylarsine oxide in their tissues. The levels of arsenobetaine, which occurs naturally in these fish, did not appear to be affected by the oral dosing with sodium arsenate. Trimethylarsine oxide also occurred as a natural component of estuary catfish and its presence may be related to the mode of feeding of this fish.

Administration, Oral↗
PubMed2005

The use of environmental integrative indicators to assess seabed disturbance in estuaries and coasts: Application to the Humber Estuary, UK.

The coastal zone is subject to many and varied changes resulting from human activities and natural processes. Existing or emerging agreements and legislation acknowledge the relevance of indicators for monitoring these. In the UK, following a series of recent workshops, potential indicators of nearshore disturbance have been identified and grouped into three broad indices: 'Coastline Morphological Change', 'Resource Use Change' and 'Environmental Quality and its Perception'. The present study developed these indicators further and tested their use by applying them to 18 sections in the Humber Estuary, Eastern England. The results obtained reflect the current knowledge of the state of the Humber environment and show the potential of integrative indicators but indicate that further studies are required to assess the relative importance of the indicators and their value in reflecting the ability of the ecosystems to sustain natural habitats and populations at a good conservation status.

Animals↗
PubMed2004

[Analysis of nitrogen, phosphorus nutrients and COD in waters of Yangtze River Estuary].

The characters of the morphological, vertical and spatial distribution of nitrogen and phosphate in the water of Changjiang Estuary were discussed, according to the survey conducted in November 2003. Among the dissolved inorganic nitrogen species, nitrate accounted for 90% in the water of Changjiang Estuary. The concentration of nitrogen nutrients in the Changjiang Estuary show higher level, and 67% of sampling stations attained or exceeded the forth standard level of seawater, according to the national standard of seawater quality. Most of total phosphate in the water of Changjiang Estuary is total dissolved phosphate (TDP), which primary composition is dissolved organic phosphate (DOP). The dramatic changes of salinity in the water of Changjiang Estuary lead to the different distribution characteristics of nutrients. The concentrations of nitrate are higher inside the estuary and lower outside the estuary due to its conservatism. On the contrast, ammonium and phosphate are influenced by the change of particle concentrations and salinity, which are higher outside the estuary and lower inside the estuary. Besides, the contents of COD in the water of Changjiang estuary are very high, and the spatial distribution characteristics are higher inside the estuary and lower outside the estuary.

Fresh Water↗
PubMed2005

Fish track wastewater pollution to estuaries.

Excess nitrogen is a forceful agent of ecological change in coastal waters, and wastewater is a prominent source of nitrogen. In catchments where multiple sources of nitrogen pollution co-exist, biological indicators are needed to gauge the degree to which wastewater-N can propagate through the receiving food webs. The purpose of this study was to test whether estuarine fish are suitable as indicators of sewage-N pollution. Fish were analysed from three estuaries within a 100-km strip on the Australian East Coast. The estuaries differ substantially in wastewater loading: (1) the Maroochy Estuary receives a large fraction of the local shire's treated sewage, (2) the Mooloolah Estuary has no licensed treated wastewater outfalls but marinas/harbours and storm-water may contribute nitrogen, and (3) the Noosa Estuary which neither receives licensed discharges nor has suspected wastewater loads. Sampling for fish included both high rainfall ('wet' season) and low rainfall ('dry' season) periods. Muscle-delta15N was the variable predicted to respond to treated wastewater loading, reflecting the relative enrichment in 15N resulting from the treatment process and distinguishing it from alternative N sources such as fertiliser and natural nitrogen inputs (both 15N-depleted). Of the 19 fish species occurring in all three estuaries, those from the Maroochy Estuary had significantly elevated delta15N values (up to 9.9 per thousand), and inter-estuarine differences in fish-delta15N were consistent across seasons. Furthermore, not only did all fish from the estuary receiving treated wastewater carry a very distinctive sewage-N tissue signal, but enriched muscle-delta15N was also evident in all species sampled from the one estuary in which sewage contamination was previously only suspected (i.e. the Mooloolah Estuary: 0.2-4.8 per thousand enrichment over fish from reference system). Thus, fish-delta15N is a suitable indicator of wastewater-N not only in systems that receive large loads, but also for the detection of more subtle nitrogen inputs. Arguably, fish may be preferred indicators of sewage-N contamination because they: (1) integrate nitrogen inputs over long time periods, (2) have an element of 'ecological relevance' because fish muscle-delta15N reflect movement of sewage-N through the food chain, and (3) pollution assessments can usually be based on evidence from multiple species.

Animals↗
PubMed2001

Assessment of changes to saltwater/freshwater habitat from reductions in flow to the Richmond River estuary, Australia.

The Australian climate is highly variable and many Australian estuaries lack a seasonal pattern of freshwater flow. During periods of low freshwater inflow, saline waters enter from the ocean through the estuary mouth. These saline waters enter as density currents or as a result of tidal mixing. During periods of high freshwater inflow from the estuary catchment, salt water is flushed towards the estuary mouth. As a consequence, the saline structure of Australian estuaries can be highly variable, depending on the antecedent rainfall. The Richmond River in northern New South Wales in such an estuary. The biota inhabiting estuaries have varying levels of freshwater and saltwater tolerance and reducing the freshwater flow into and along an estuary will favour saltwater species. However, if extractions of freshwater from an estuary are sufficiently high, freshwater habitat could be eliminated entirely for short periods (-one month) but with consequent, and perhaps long-standing, damage to the environment. This contribution describes a new approach to quantify the impact of changes to freshwater flows to the Richmond River estuary. This approach includes a review of hydrological data gathered over the past century and includes a detailed assessment of: changes to the highly variable freshwater inflows and freshwater extraction below the tidal limit; consequent changes to the highly variable saline structure; and the risk to aquatic biota. The crucial factors of magnitude, frequency and duration of short-term intrusions of saline water into freshwater habitat and their impact are quantified by the methods developed.

Climate↗
PubMedDate not supplied

Measured concentrations of herbicides and model predictions of atrazine fate in the Patuxent River estuary.

The environmental fate of herbicides in estuaries is poorly understood. Estuarine physical transport processes and the episodic nature of herbicide release into surface waters complicate interpretation of water concentration measurements and allocation of sources. Water concentrations of herbicides and two triazine degradation products (CIAT [6-amino-2-chloro-4-isopropylamino-s-triazine] and CEAT [6-amino-2-chloro-4-ethylamino-s-triazine]) were measured in surface water from four sites on 40 d from 4 Apr. through 29 July 19% in the Patuxent River estuary, part of the Chesapeake Bay system. Atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) was most persistent and present in the highest concentrations (maximum = 1.29 microg/L). Metolachlor [2-chloro-6'-ethyl-N-(2-methoxy-1-methylethyl)-o-acetoluidide], CIAT, CEAT, and simazine (1-chloro-3,5-bisethylamino-2,4,6-triazine) were frequently detected with maximum concentration values of 0.61, 1.1, 0.76, and 0.49 microg/L, respectively. A physical transport model was used to interpret atrazine concentrations in the context of estuarine water transport, giving estimates of in situ degradation rates and total transport. The estimated half-life of atrazine in the turbid, shallow upper estuary was t(1/2) = 20 d, but was much longer (t(1/2) = 100 d) in the deeper lower estuary. Although most (93%) atrazine entered the estuary upstream via the river, simulations suggested additional inputs directly to the lower estuary. The total atrazine load to the estuary from 5 April to 15 July was 71 kg with 48% loss by degradation and 31% exported to the Chesapeake Bay. Atrazine persistence in the estuary is directly related to river flows into the estuary. Low flows will increase atrazine residence time in the upper estuary and increase degradation losses.

Atrazine↗
PubMed2003

Factors affecting the distribution of benthic macrofauna in estuaries contaminated by urban runoff.

Contaminants derived from urban runoff have been shown to accumulate in estuarine sediments, reaching concentrations potentially capable of causing biological effects. Demonstration of effects, however, is difficult due to strong natural environmental gradients and the effects of past or present point-sources of contamination. We used multivariate methods to test two hypotheses relating to the effects of urban-derived contaminants on estuarine benthic communities. First, that patterns of distribution and abundance of benthic invertebrates in two urbanised estuaries would be different from those in two non-urbanised estuaries. Second, that the distributions of benthic invertebrates within and among the four estuaries would be related to those of urban-derived contaminants. Concentrations of contaminants were larger in estuaries with urbanised catchments and concentrations of Cu, Pb, Zn and DDT in some samples exceeded those at which biological effects may be expected to appear. Tests of differences in composition of benthic communities among estuaries showed that the two urban estuaries were not significantly different, but that they differed from both rural estuaries, which also differed from each other. Distributions of benthic invertebrates were significantly related to those of environmental variables, and were ordinated along axes that correlated with both natural environmental variables (nature of the sediment, position in estuary) and contaminants. Differences in faunas between the urban and non-urban estuaries were not, however, clear-cut and nor were relationships between faunal assemblages and environmental variables (including contaminants) consistent between two times of sampling.

Animals↗
PubMed2001

Status of persistent organic pollutants in the sediment from several estuaries in China.

Sediment samples from three estuaries on the east coast of China were analyzed for persistent organic pollutants. Total PCB, PAH, and DDT concentrations in the sediments from Minjiang, Jiulongjiang, and Zhujiang estuaries ranged from 2 to 14 ng/g, 400 to 1500 ng/g, and 6 to 73 ng/g, respectively, in the sediments from these estuaries. The sources of PAH contamination were inferred from PAH compositions, with pyrogenic PAHs being the dominant source for Minjiang Estuary and petroleum related PAHs being the primary contributors to Jiulongjiang and Zhujiang estuaries. The high concentrations of DDT in the sediments from these estuaries were likely the result of widespread use of DDT in China in the 1960s and 1970s. Butyltin compounds were detected in the sediment from Jiulongjiang Estuary and Victoria Harbor, Hong Kong. Presence of butyltin compounds probably result from the shipping activities in these estuaries. Butyltin compounds were not detected in the sediments from Minjiang and Zhujiang estuaries. Contaminant concentrations were generally below levels expected to affect benthic organisms with the exception of DDTs.

Animals↗
PubMed2002

Survey of four marine antifoulant constituents (copper, zinc, diuron and Irgarol 1051) in two UK estuaries.

A field survey of antifoulant concentrations was undertaken in two UK estuaries (Hamble and Orwell) in 1998 and 1999. The two locations offered variations in physical aspects (Orwell estuary being significantly larger than the Hamble) as well as differences in boat densities (Hamble having almost twice as many vessels moored in the estuary and marinas). Samples were analysed for copper, zinc, diuron and Irgarol 1051, and were collected in summer and winter in order to identify potential seasonal variations in concentrations. The effect that different marina types (e.g. locked marina, one located in a natural inlet and pontooned ones in the open estuary) had on antifoulant concentrations were also investigated. Concentrations of the organic booster biocides, diuron and Irgarol 1051 in the marinas and estuaries were mainly influenced by leaching from antifoulant paints applied to the hulls of leisure craft, and so levels reflected the number of vessels present in the water. As a consequence significantly higher concentrations were found in marinas (up to ca. 900 ng l(-1) for diuron and 240 ng l(-1) for Irgarol 1051) compared with estuaries (up to ca. 400 ng l(-1) for diuron and 100 ng l(-1) for Irgarol 1051) and in summer compared with winter. Sediment concentrations of Irgarol 1051 and diuron were rarely detectable other than in the marinas where high concentrations were detected near slipways assumed to be derived from washed off paint chips. Dissolved concentration profiles for copper and zinc in the estuaries and marinas were different from those for the organic booster biocides partly because other sources of these metals contributed to estuarine and marina loads. In particular, riverine loads and inputs from sacrificial anodes attached to leisure craft, exhibited a major influence of estuarine levels of zinc. Consequently, only in the Hamble estuary for copper was there a clear distinction between summer (typically 3-4 microg l(-1)) and winter dissolved values (typically 1-2 microg l(-1)) that could be largely attributable to the leaching of antifoulant paints. Sediment concentrations for both metals were similar for both estuaries, with little variation between winter and summer values (Zn ranging from 28 to 614 mg kg(-1) and Cu from 6 to 1016 mg kg(-1)) as with the organic booster biocides highest levels were measured at the base of slipways in marinas.

Copper↗
PubMed2005

Tolerance to metals and assessment of energy reserves in the polychaete Nereis diversicolor in clean and contaminated estuaries.

Estuaries are subject to anthropogenic activities. Because the intrasedimentary worm Nereis diversicolor has ecological characteristics and bioindicator abilities, its use was pertinent in investigating the concepts and cost of tolerance to heavy metals (Cd, Cu, Zn). In this context, two approaches were carried out, performing toxicity tests and estimating energy reserves (glycogen and lipids), in populations originating from a contaminated site (Seine estuary) compared with those from a clean site (Authie estuary). Mean lethal times (LT(50)s) of organisms exposed to zinc from the Seine estuary were higher than those from the Authie estuary, but not of organisms exposed to Cd or Cu. The influence of animal weight and salinity on the sensitivity of worms also was studied. The biggest worms were more tolerant to zinc than the smallest ones, and worms survived longer at a reduced salinity (15 per thousand). Concentrations of glycogen and lipids in each sampling season were higher in specimens from the Authie estuary than in worms from the Seine estuary. No influence of salinity on glycogen and lipid levels was observed. Glycogen concentrations were not influenced by the weight of specimens, whereas lipid concentrations were significantly and positively correlated with weight. In conclusion, worms from the Seine estuary exhibited tolerance to Zn, and the depletion of energy reserves observed in this population could be interpreted as a cost of tolerance.

Adaptation, Physiological↗
PubMed2006

Biological effects of anthropogenic contaminants in the San Francisco Estuary.

Concentrations of many anthropogenic contaminants in the San Francisco Estuary exist at levels that have been associated with biological effects elsewhere, so there is a potential for them to cause biological effects in the Estuary. The purpose of this paper is to summarize information about biological effects on the Estuary's plankton, benthos, fish, birds, and mammals, gathered since the early 1990s, focusing on key accomplishments. These studies have been conducted at all levels of biological organization (sub-cellular through communities), but have included only a small fraction of the organisms and contaminants of concern in the region. The studies summarized provide a body of evidence that some contaminants are causing biological impacts in some biological resources in the Estuary. However, no general patterns of effects were apparent in space and time, and no single contaminant was consistently related to effects among the biota considered. These conclusions reflect the difficulty in demonstrating biological effects due specifically to contamination because there is a wide range of sensitivity to contaminants among the Estuary's many organisms. Additionally, the spatial and temporal distribution of contamination in the Estuary is highly variable, and levels of contamination covary with other environmental factors, such as freshwater inflow or sediment-type. Federal and State regulatory agencies desire to develop biological criteria to protect the Estuary's biological resources. Future studies of biological effects in San Francisco Estuary should focus on the development of meaningful indicators of biological effects, and on key organism and contaminants of concern in long-term, multifaceted studies that include laboratory and field experiments to determine cause and effect to adequately inform management and regulatory decisions.

Animals↗
PubMed2006

Urogenital papilla feminization in male Pomatoschistus minutus from two estuaries in northwestern Iberian Peninsula.

Recently, male urogenital papilla feminization (UGPF) in the sand goby Pomatoschistus minutus was reported in several UK estuaries with high levels of estrogenic compounds. The fact that this species is also common in southern European estuaries, together with its life-cycle characteristics, prompted us to investigate P. minutus UGPF in the northwestern of Iberian Peninsula. Specimens of P. minutus were periodically sampled during 2004 at several locations in two estuaries (Minho and Lima). Evidence for UGPF was recorded in both estuaries, the highest incidence being observed in the Lima estuary (50%). Estrogen levels (17beta-estradiol and estrone) above 100 pg/l were observed in both estuaries, the higher concentrations being found in the Lima estuary. Overall, the results suggest a relationship between the feminization of male P. minutus urogenital papilla and the presence of estrogenic compounds. In the future, more in-depth studies are required in order to use P. minutus as a sentinel species for estrogenic compound monitoring in estuaries.

Animals↗