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1.
Isaac Wirgin Blake Konkle Mark Pedersen Cheryl Grunwald Jim Williams Simon C. Courtenay 《Estuaries and Coasts》1996,19(4):913-922
Quantification of levels of cytochrome P4501A (CYP1A) gene expression in sentinel species of fishes has been proposed as a management tool to evaluate contamination of aquatic systems. Based on preliminary studies, we hypothesized that differences in CYP1A mRNA inducibility among individuals, populations, or species might lead to spurious conclusions when using this approach in environmental monitoring programs. To address this possibility, we quantitated and compared CYP1A mRNA induction levels in four species of common Atlantic Coast estuarine fish: smooth flounder, hogchoker, striped bass, and Atlantic tomcod, which were treated with model chemicals (beta naphthoflavone (β-NF), or benzo[a]pyrene at 10 ppm) known to induce CYP1A mRNA, or were exposed to contaminated environments. Species-specific CYP1A DNA probes were generated from PCR (polymerase chain reaction) amplification of genomic DNA using conserved oligonucleotide primers, and, along with cloned rainbow trout and Atlantic tomcod CYP1A cDNA probes were used to quantify CYP1A mRNA levels in northern blot analyses. Successful PCR amplification of CYP1A hybridizable DNA fragments was observed for all four species. Results from northern blot analyses showed large differences in CYP1A mRNA induction among species; only Atlantic tomcod exhibited significant induction of CYP1A mRNA for both chemically treated (97-fold) and environmentally exposed fish (34-fold). Significant, although lower, levels of induction were observed in β-NF treated (14-fold) smooth flounder, but not in environmentally exposed smooth flounder. Only low levels (not significant) of CYP1A gene induction were detected in hogchokers and striped bass. We conclude that CYP1A mRNA inducibility differed significantly among fish taxa perhaps due to differences in regulation of gene expression, suggesting that careful selection of sentinel species should be exercised prior to the use of CYP1A mRNA induction in environmental monitoring programs. However, the significance of differences in CYP1A mRNA inducibility in relation to higher level biological endpoints has yet to be determined. 相似文献
2.
Water renewal estimates for aquaculture developments in the Richibucto estuary,Canada 总被引：1，自引：0，他引：1
V.?G.?KoutitonskyEmail author T.?Guyondet A.?St-Hilaire S.?C.?Courtenay A.?Bohgen 《Estuaries and Coasts》2004,27(5):839-850
Water renewal in semi-enclosed coastal areas is crucial for the supply of oxygen and seston and for the removal of organic
loadings from finfish or shellfish aquaculture sites. Water renewal depends on hydrodynamic processes and can have a complex
spatial distribution due to irregular topographic features. This study describes some physical oceanography observations gathered
in the Richibucto estuary, New Brunswick, Canada, and provides an estimate of the spatial distribution of water renewal in
the North Arm, a location in the estuary where the largest American oyster (Crassostrea virginica) aquaculture operation in eastern Canada is located. The estuary changes from a well mixed estuary to a partially stratified
estuary depending on runoff conditions. Tides are mixed but mainly diurnal due to the nearby presence of the second M2 amphidromic point in the Gulf of St. Lawrence. Tidal amplitudes vary from 0.3 to 0.6 m and show a slight increase some 35
km upstream. Currents in the main channel can reach over 0.60 m s−1 during ebb and 0.3 m s−1 during flood, with a slack water period of approximately 8 h. Low frequency sea level fluctuations have a range of 0.5 m
at the mouth and are coherent within the estuary. Hydrodynamic and advection-dispersion models are used to calculate the spatial
distribution of the local renewal time (LRT) in the North Arm for high and low freshwater discharge conditions, using the
dissolved tracer method. Results show that the LRT varies from less than 5 d at the downstream end of the North Arm to over
100 d further upstream. When averaged over the entire North Arm, the integral renewal time (IRT) is estimated to vary only
from 8 to 21 d depending on the season. The LRT and IRT estimates are major improvements over conventional renewal estimates
using tidal prism methods. 相似文献
3.
ABSTRACTSedimentation in navigable waterways and harbours is of concern for many water and port managers. One potential source of variability in sedimentation is the annual sediment load of the river that empties in the harbour. The main objective of this study was to use some of the regularly monitored hydro-meteorological variables to compare estimates of hourly suspended sediment concentration in the Saint John River using a sediment rating curve and a model tree (M5?) with different combinations of predictors. Estimated suspended sediment concentrations were multiplied by measured flows to estimate suspended sediment loads. Best results were obtained using M5? with four predictors, returning an R2 of 0.72 on calibration data and an R2 of 0.46 on validation data. Total load was underestimated by 1.41% for the calibration period and overestimated by 2.38% for the validation period. Overall, the model tree approach is suggested for its relative ease of implementation and constant performance.
EDITOR M.C. Acreman; ASSOCIATE EDITOR B. Touaibia 相似文献
4.
5.
Ramachandran SD Sweezey MJ Hodson PV Boudreau M Courtenay SC Lee K King T Dixon JA 《Marine pollution bulletin》2006,52(10):1182-1189
The use of chemical oil dispersants to minimize spill impacts causes a transient increase in hydrocarbon concentrations in water, which increases the risk to aquatic species if toxic components become more bioavailable. The risk of effects depends on the extent to which dispersants enhance the exposure to toxic components, such as polycyclic aromatic hydrocarbons (PAH). Increased salinities can reduce the solubility of PAH and the efficiency of oil dispersants. This study measured changes in the induction of CYP1A enzymes of fish to demonstrate the effect of salinity on PAH availability. Freshwater rainbow trout and euryhaline mummichog were exposed to water accommodated fractions (WAF), and chemically-enhanced water accommodated fractions (CEWAF) at 0 per thousand, 15 per thousand, and 30 per thousand salinity. For both species, PAH exposure decreased as salinity increased whereas dispersant effectiveness decreased only at the highest salinity. Hence, risks to fish of PAH from dispersed oil will be greatest in coastal waters where salinities are low. 相似文献
6.
The relationship between winter sea ice variability and the North Atlantic Oscillation (NAO) is examined for the time period
1860–2300. This study uses model output to extend recently reported observational results to multi-century time scales. Nine
ensemble members are used in two Global Climate Models with forcing evolving from pre-industrial conditions through the so-called
A1B scenario in which carbon dioxide stabilizes at 720 ppm by 2100. Throughout, the NAO generates an east-west dipole pattern
of sea ice concentration (SIC) anomalies with oppositely signed centers of action over the Labrador and Barents Seas. During
the positive polarity of the NAO, SIC increases over the Labrador Sea due to wind-driven equatorward advection of ice, and
SIC decreases over the Barents Sea due to wind-driven poleward transport of heat within the mixed layer of the ocean. Although
this NAO-driven SIC variability pattern can always be detected, it accounts for a markedly varying fraction of the total sea
ice variability depending on the strength of the forced sea ice extent trend. For the first half of the 20th century or 1990
control conditions, the NAO-driven SIC pattern accounts for almost a third of the total SIC variance. In the context of the
long term winter sea ice retreat from 1860 to 2300, the NAO-driven SIC pattern is robustly observable, but accounts for only
2% of the total SIC variance. The NAO-driven SIC dipole retreats poleward with the retreating marginal ice zone, and its Barents
Sea center of action weakens. Results presented here underscore the idea that the NAO’s influence on Arctic climate is robustly
observable, but time dependent in its form and statistical importance. 相似文献
7.
Sorrentino C Roy NK Chambers RC Courtenay SC Wirgin I 《Marine environmental research》2004,58(2-5):383-388
Atlantic tomcod (Microgadus tomcod) from the Hudson River (HR) are resistant at the molecular and organismic levels to the effects of exposure to dioxin-like aromatic hydrocarbon (AH) compounds, but much less so to benzo[a]pyrene (B[a]P). The aims of this study were to determine in early life-stages of tomcod exposed to B[a]P: (1) if DNA binding levels differed between fish from the HR and Miramichi River (MR), and (2) if co-exposure to chromium could modulate this genotoxic effect. After exposure to [(3)H]B[a]P alone, DNA-bound radioactivity was 5-10-fold higher in embryos and larvae of MR than HR descent. Co-exposure to chromium modulated DNA binding levels in offspring of both populations. In MR embryos, co-exposure to chromium inhibited B[a]P uptake. These results demonstrated resistance to the genotoxic effects of B[a]P in early life stages of HR tomcod at an ecologically important endpoint and suggest the ability of chromium to modulate AH-induced genotoxicity. 相似文献
8.
Courtenay Strong 《Climate Dynamics》2012,39(12):3091-3102
Arctic marginal ice zone (MIZ) widths in the Atlantic sector were measured during the months of maximum sea ice extent (February–April) for years 1979–2010 using a novel method based on objective curves through idealized sea ice concentration fields that satisfied Laplace’s equation. Over the record, the Labrador Sea MIZ (MIZL) had an average width of 122 km and narrowed by 28 % while moving 254 km poleward, the Greenland Sea MIZ (MIZG) had an average width of 98 km and narrowed by 43 % while moving 158 km west toward the Greenland coast, and the Barents Sea MIZ (MIZB) had an average width of 136 km and moved 259 km east toward the Eurasian coast without a trend in width. Trends in MIZ position and width were consistent with a warming Arctic and decreasing sea ice concentrations over the record. Beyond the trends, NAO-like atmospheric patterns influenced interannual variability in MIZ position and width: MIZL widened and moved southeast under anomalously strong northerly flow conducive to advection of sea ice into the Labrador Sea, MIZG widened and moved northeast under anomalously weak northerly flow conducive to diminishing the westward component of sea ice drift, and MIZB widened and moved poleward at the expense of pack ice under anomalously strong southwesterly flow conducive to enhancing oceanic heat flux into the Barents Sea. In addition, meridional flow anomalies associated with the NAO per se moved MIZB east and west by modulating sea ice concentration over the Barents Sea. 相似文献
9.
The variance of the North Atlantic Oscillation index (denoted N) is shown to depend on its coupling with area-averaged sea ice concentration anomalies in and around the Barents Sea (index denoted B). The observed form of this coupling is a negative feedback whereby positive N tends to produce negative B, which in turn forces negative N. The effects of this feedback in the system are examined by modifying the feedback in two modeling frameworks: a statistical vector autoregressive model (F VAR) and an atmospheric global climate model (F CAM) customized so that sea ice anomalies on the lower boundary are stochastic with adjustable sensitivity to the model??s evolving N. Experiments show that the variance of N decreases nearly linearly with the sensitivity of B to N, where the sensitivity is a measure of the negative feedback strength. Given that the sea ice concentration field has anomalies, the variance of N goes down as these anomalies become more sensitive to N. If the sea ice concentration anomalies are entirely absent, the variance of N is even smaller than the experiment with the most sensitive anomalies. Quantifying how the variance of N depends on the presence and sensitivity of sea ice anomalies to N has implications for the simulation of N in global climate models. In the physical system, projected changes in sea ice thickness or extent could alter the sensitivity of B to N, impacting the within-season variability and hence predictability of N. 相似文献
10.
Analyses of six years of bottom trawl data collected from Northumberland Strait, southern Gulf of St. Lawrence revealed four major fish assemblages, two of which occurred in the same two geographic areas each year. One of the two persistent assemblages occurred in deeper water off northwestern Prince Edward Island and consisted mostly of demersal fishes. The other persistent assemblage contained a mixture of demersal and pelagic fishes and occurred primarily in shallow water of central Northumberland Strait. Analyses of abiotic (depth, bottom temperature, substratum type) and biotic (presence of American lobster Homarus americanus, northern lady crab Ovalipes ocellatus) factors revealed bottom temperature and catches of lady crab correlate best with the fish assemblage structure each year, but correlation values were low (ρw ≤ 0.48). Combinations of all abiotic and biotic variables only marginally improved the strength of the correlations in four of six years (2002, 2003, 2005, 2006). Changes observed in the Northumberland Strait ecosystem over the six years included an increase in the ratio of pelagic to demersal fishes, disappearance of one of the four assemblages, and increased spatial overlap between the two persistent assemblages, which coincided with an increase in bottom temperature. The increasing importance of pelagic fishes, relative to demersal fishes, suggests a shift in food web structure may be occurring in Northumberland Strait. 相似文献