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1.
Lisa E. Osterman Richard Z. Poore Peter W. Swarzenski David B. Senn Steven F. DiMarco 《Geo-Marine Letters》2009,29(6):405-414
Since systematic measurements of Louisiana continental-shelf waters were initiated in 1985, hypoxia (oxygen content <2 mg
L−1) has increased considerably in an area termed the dead zone. Monitoring and modeling studies have concluded that the expansion
of the Louisiana shelf dead zone is related to increased anthropogenically derived nutrient delivery from the Mississippi
River drainage basin, physical and hydrographical changes of the Louisiana Shelf, and possibly coastal erosion of wetlands
in southern Louisiana. In order to track the development and expansion of seasonal low-oxygen conditions on the Louisiana
shelf prior to 1985, we used a specific low-oxygen foraminiferal faunal proxy, the PEB index, which has been shown statistically
to represent the modern Louisiana hypoxia zone. We constructed a network of 13 PEB records with excess 210Pb-derived chronologies to establish the development of low-oxygen and hypoxic conditions over a large portion of the modern
dead zone for the last 100 years. The PEB index record indicates that areas of low-oxygen bottom water began to appear in
the early 1910s in isolated hotspots near the Mississippi Delta and rapidly expanded across the entire Louisiana shelf beginning
in the 1950s. Since ~1950, the percentage of PEB species has steadily increased over a large portion of the modern dead zone.
By 1960, subsurface low-oxygen conditions were occurring seasonally over a large part of the geographic area now known as
the dead zone. The long-term trends in the PEB index are consistent with the 20th-century observational and proxy data for
low oxygen and hypoxia. 相似文献
2.
The reproductive effects of chronic exposure to water-soluble fractions (WSF) of diesel fuel oil and naphthalene in female Atlantic croaker during critical periods of their reproductive life history were investigated. Fish were repeatedly exposed to WSF of oil (2.5 or 5%) or naphthalene (0.5 or 1.0 ppm) for 5 or 8 weeks. Both pollutants blocked sexual maturation in some fish and impaired ovarian recrudescence in others. The majority of the oocytes in exposed fish were undeveloped and widespread oocyte atresia was evident at higher concentrations of these polycyclic aromatic hydrocarbons (PAH). The disruption of ovarian growth and oocyte development in croaker after PAH exposure was associated with alterations in reproductive endocrine function at multiple sites on the hypothalamus-pituitarygonadal axis. A third period of increased sensitivity to xenobiotics was observed during final oocyte maturation. 相似文献
3.
P Thomas 《Marine environmental research》2000,50(1-5):127-134
The characteristics of steroid nuclear and membrane receptors and their interactions with xenobiotic chemicals in two marine perciform species, Atlantic croaker (Micropogonias undulatus) and spotted seatrout (Cynoscion nebulosus) are briefly reviewed. Several organochlorines that bind to the nuclear progesterone receptor in mammals show negligible binding to the nuclear progestogen receptor in seatrout ovaries. Two distinct nuclear androgen receptors with different tissue distributions have been identified in croaker, but only one of them binds xenobiotic anti-androgens previously identified in mammals. Multiple forms of the nuclear estrogen receptor (ER) have been identified in fishes. The ER in croaker testis has a higher affinity than the croaker liver ER for estrogens and xenoestrogens and may be more susceptible to chemical interference. In addition, differences in the feedback effects of estrogens and xenoestrogens on gonadotropin secretion in croaker are observed, depending on the stage of the reproductive cycle. Finally, the first clear evidence in any vertebrate for xenobiotic chemical interference with the nongenomic actions of steroids by binding to steroid membrane receptors was obtained with the seatrout ovarian progestogen membrane receptor and since has been confirmed with progestogen and estrogen membrane receptors in croaker sperm and testes. These various factors that influence chemical/steroid receptor interactions are likely to significantly modify steroid hormone actions at target tissues and consequently the toxicological effects of chemical exposure. 相似文献
4.
5.
A carbon,nitrogen, and sulfur elemental and isotopic study in dated sediment cores from the Louisiana Shelf 总被引：2，自引：0，他引：2
Robert J. Rosenbauer Peter W. Swarzenski Carol Kendall William H. Orem Frances D. Hostettler Mark E. Rollog 《Geo-Marine Letters》2009,29(6):415-429
Three sediment cores were collected off the Mississippi River delta on the Louisiana Shelf at sites that are variably influenced
by recurring, summer-time water-column hypoxia and fluvial loadings. The cores, with established chronology, were analyzed
for their respective carbon, nitrogen, and sulfur elemental and isotopic composition to examine variable organic matter inputs,
and to assess the sediment record for possible evidence of hypoxic events. Sediment from site MRJ03-3, which is located close
to the Mississippi Canyon and generally not influenced by summer-time hypoxia, is typical of marine sediment in that it contains
mostly marine algae and fine-grained material from the erosion of terrestrial C4 plants. Sediment from site MRJ03-2, located
closer to the mouth of the Mississippi River and at the periphery of the hypoxic zone (annual recurrence of summer-time hypoxia
>50%), is similar in composition to core MRJ03-3, but exhibits more isotopic and elemental variability down-core, suggesting
that this site is more directly influenced by river discharge. Site MRJ03-5 is located in an area of recurring hypoxia (annual
recurrence >75%), and is isotopically and elementally distinct from the other two cores. The carbon and nitrogen isotopic
composition of this core prior to 1960 is similar to average particulate organic matter from the lower Mississippi River,
and approaches the composition of C3 plants. This site likely receives a greater input of local terrestrial organic matter
to the sediment. After 1960 and to the present, a gradual shift to higher values of δ13C and δ15N and lower C:N ratios suggests that algal input to these shelf sediments increased as a result of increased productivity
and hypoxia. The values of C:S and δ34S reflect site-specific processes that may be influenced by the higher likelihood of recurring seasonal hypoxia. In particular,
the temporal variations in the C:S and δ34S down-core are likely caused by changes in the rate of sulfate reduction, and hence the degree of hypoxia in the overlying
water column. Based principally on the down-core C:N and C:S ratios and δ13C and δ34S profiles, sites MRJ03-3 and MRJ03-2 generally reflect more marine organic matter inputs, while site MRJ03-5 appears to be
more influenced by terrestrial deposition. 相似文献
6.
Our goal was to study the involvement of cytochrome P450 genes in estrogen metabolism and the extent to which the potentially carcinogenic 4-hydroxyestradiol metabolite is formed by channel catfish (Ictalurus punctatus; CC). Estradiol metabolism and ethoxyresorufin-O-deethylase (EROD) activity were assessed in several tissues from fish collected from three variably contaminated sites in the Mississippi River Delta, from laboratory control fish, and from fish exposed to 20 mg/kg benzo(a)pyrene (BaP) i.p. for 4 days. Liver EROD activity was induced by BaP, but Delta fish EROD activities were not statistically higher than activities in control fish. Gill microsomal EROD activity was also induced by BaP, but activities were 8- to 77-fold lower than those from liver. The predominant estrogen metabolites formed by CC liver, gill and gonad microsomes were 2-hydroxyestradiol and estrone as detected by GC/MS. Liver and gill 2-hydroxyestradiol formation was induced in BaP-dosed fish. The trends in hydroxyestradiol formation in field collected fish were more variable. In all fish liver microsomes there was more 2- compared to 4-hydroxyestradiol formed. However, BaP-treatment increased the 4:2 hydroxyestradiol ratio from 0.04 in control fish to 0.2 in BaP-exposed fish, suggesting that BaP induces the formation of the potentially genotoxic estrogen metabolite. No detectable 4-hydroxyestradiol was produced by gill and gonad microsomes. These results will ultimately help in determining which fish P450 genes are susceptible to environmental contamination and may be involved in estrogen genotoxicity. 相似文献
7.
Turner RE Rabalais NN Swenson EM Kasprzak M Romaire T 《Marine environmental research》2005,59(1):65-77
An 18-year monitoring record (1978-1995) of dissolved oxygen within a region having hypoxia (dissolved oxygen less than 2 mgl(-1)) in the bottom layer was examined to describe seasonal and annual trends. The monitoring location was near or within a well-described summer hypoxic zone whose size has been up to 20,000 km(2). The monitoring data were used to hindcast the size of the hypoxic zone for before consistent shelfwide surveys started, and to predict it for 1989, when a complete shelfwide survey was not made. The concentration of total Kjeldahl nitrogen (TKN) in surface waters and concentration of bottom water oxygen were directly related, as anticipated if organic loading from surface to bottom was from in situ processes. The TKN data were used to develop a predictive relationship that suggested there was no substantial hypoxia before the 1970s, which was before nitrate flux from the Mississippi River to the Gulf of Mexico began to rise. The peak frequency in monthly hypoxic events is two to three months after both the spring maximum in discharge and nitrate loading of the Mississippi River. These results support the conclusion that persistent, large-sized summer hypoxia is a recently-developed phenomenon that began in the 1970s or early 1980s. 相似文献
8.
The role of vitellogenin in the transport of organochlorines was investigated in Atlantic croaker (Micropogonias undulatus) by exposing them through the diet to o,p′-DDT at a concentration of 10.8 μg/100 g fish/day for 14 days or Aroclor 1254 (PCB) at a concentration of 0.5 mg/100 g fish/day for 30 days during gonadal recrudescence. Tissue samples were taken from the fish at various times after initial exposure, and o,p′-DDT and PCBs were extracted in acetonitrile and analyzed by gas chromatography. Analysis of the ovarian tissue collected 2 and 3 weeks from the start of exposure revealed that the o,p′-DDT concentration increases as the gonadosomatic index (GSI) increases (r2 = 0.63), with accumulation ranging from less than 1% to as much as 8% of the total dosage. Interestingly, o,p′-DDT did not accumulate in the testes during the same exposure period. Accumulation of PCBs was found to be 40 times higher in the ovaries than in the testes. Gel filtration of plasma from exposed females showed that o,p′-DDT elutes in the low density lipoprotein and vitellogenin fractions. Control plasma incubated with o,p′-DDT at 4 °C for 16 h followed by chromatography on Sepharose 6B gave similar results with an o,p′-DDT concentration of 0.6μg/mg protein in the vitellogenin fraction. Furthermore, both o,p′-DDT and PCBs were found to bind to purified croaker vitellogenin. These results suggest that lipoproteins, including vitellogenin, are involved in the transport and accumulation of organochlorines in the ovaries of exposed fish. 相似文献
9.
Diel feeding pattern and food consumption of whitemouth croaker (Micropogonias furnieri) were examined and related to seasonal variations in an estuarine environment. To determine diel feeding pattern whitemouth croaker were collected from the Patos Lagoon Estuary over 24 h (～3‐h intervals) and their stomach contents were examined. Food consumption of whitemouth croaker was determined from evacuation rates estimated experimentally and in the field. The results suggested that whitemouth croaker in the Patos Lagoon estuary feed all day long. However, whitemouth croaker showed higher feeding intensity and food consumption during daylight hours when the water transparency increased than in others when water transparency was low. Thus, whitemouth croaker seemed to intensify their feeding when they could see their prey. Daily food consumption was between 0.9 and 5.3% of body wet weight (these being the lowest and highest consumption rates during the winter and summer, respectively). The maximum predation impact of whitemouth croaker on their preferential prey, the tanaid Kalliapseudes schubartii, was 27indiv·m?2·day?1. The results suggested that the changes in water transparency seem to affect the diel feeding pattern and food consumption of whitemouth croaker. This could have important consequences for fish growth. 相似文献
10.
The fitness of parasitic organisms is strongly driven by their ability to infect potential hosts. Although transmission to a host organism is a key component to the parasitic lifestyle, surviving and reproducing within a host poses additional challenges. Cymothoa excisa is a parasitic isopod that infects Atlantic croaker, Micropogonias undulatus, along the Texas coast and has evolved mechanisms to successfully survive and reproduce within its host. Cymothoa excisa is known to exhibit sex‐change strategies but limited information exists on morphological changes, reproductive output and the timing at which sex change becomes optimal. This study collected Atlantic croaker during a 22‐month survey period and identified parasite prevalence and intensity in the host fish population. Infection rates were constant throughout the year at 19.88% and intensity increased through the season up to a maximum of four parasites. Following collection, isopod morphological parameters were quantified for each life stage (including female, transitional, male and juvenile), identifying shape and size transitions through ontogeny and sex change. Transitional C. excisa isopods only occurred when only one isopod was present in a fish, suggesting that isopods change sex from male to female if they are the first to recruit to an uninfected host. As isopods transition to females they have a large increase in size, legs, and pleotelson (which influence fecundity and anchoring ability), whereas the gonopod, eyes and uropod show a reduction (which are no longer needed for swimming and finding hosts). Data suggest that C. excisa sex change is related to the timing of infection and brood size increases with female size and host size. Therefore, it would be advantageous to be the first isopod to infect a host, as it could change into a female and increase reproductive potential. We discuss hypotheses that could explain the mating behavior of parasitic isopods. 相似文献
11.
Peter Thomas 《Marine environmental research》1988,24(1-4)
To examine whether xenobiotics impair teleost reproduction by altering reproductive endocrine function, steroid hormone secretion and ovarian growth were investigated in female Atlantic croaker (Micropogonias undulatus) after chronic oral administration with sublethal doses of three classes of reproductive toxins (lead, benzo[a]pyrene and Aroclor 1254). All the sublethal treatments significantly impaired ovarian growth as assessed by the gonadosomatic index. Reduced ovarian growth was accompanied by a significant decline in circulating 17β-estradiol levels in fish exposed to lead and benzo[a]pyrene. All three toxicants significantly decreased plasma testosterone levels. However, the steroidogenic capacity of ovarian tissue in vitro was not altered by xenobiotic exposure. The data suggest that the decreased ovarian growth in croaker after pollutant exposure may be a consequence of the decline in plasma 17β-estradiol levels. Further, this decrease in circulating levels of gonadal steroids does not appear to be caused by a direct effect of the chemicals on ovarian steroid synthesis. 相似文献
12.
Bifenthrin(BF) is a pyrethroid insecticide that is widely used in agriculture, horticulture, and for residential purposes. However, few studies addressing the reproductive toxicity of BF on fishes are available. The present study was conducted to investigate the effects of BF on testicular development in Sebastiscus marmoratus and to gain insight into its mechanism. After exposure to 1, 10 and 100 ng/L BF for 50 days, there was a reduced number of mature sperm and an abundance of the late stages of spermatocysts in the testes. The levels of 17β-estradiol and testosterone were decreased significantly after BF exposure. The activity of caspase-3 was increased in a dosedependent manner after BF exposure, TUNEL assay indicated that BF exposure resulted in the occurrence of apoptosis in the testes, which might be main reason for the inhibition of spermatogenesis. 相似文献
13.
Intersexes in Mississippi River shovelnose sturgeon sampled below Saint Louis, Missouri, USA. 总被引：6，自引：0，他引：6
The Missouri Department of Conservation detected high organochlorine levels in tissues of fish from the Mississippi River south of Saint Louis. Chlordane, which is both a carcinogen and an endocrine disrupter, reached 2960 micrograms/kg in fillets of shovelnose sturgeon, Scaphirhynchus platyorynchus, and 1926 micrograms/kg in their roe, wet weight basis. Polychlorinated biphenyls (PCBs) and p,p'-dichlorodiphenyldichloroethylene (DDE) in roe have reached 5810 and 780 micrograms/kg, respectively. The purpose of this study was to determine if endocrine disrupters and carcinogens are a potential cause of the significantly diminished reproduction capacity and population declines in the endangered pallid sturgeon, Scaphirhynchus albus. Twenty-four surrogate shovelnose sturgeons were sampled north of Saint Louis where contaminant levels were lower compared with 17 sampled south of Saint Louis where contaminant levels were high. Liver and gonad tissues were formalin-fixed, histologically processed and examined. Neoplasms were not found. The principal finding was that the testes of two of the seven downstream male fish contained ovigerous lamellae, in addition to mature sperm. Since sturgeons are gonochoristic and intersexes are rare and unusual, the occurrence of intersex in 29% of the male Mississippi River shovelnose sturgeon examined from a population contaminated with chlordane and other chemicals raise concern for human health, species biodiversity and preservation of waterway quality. These findings, however, need to be corroborated by expanded studies with a higher sample size. 相似文献
14.
为研究患病大黄鱼(Larimichthys crocea)消化道中可能的病原微生物,采用高通量测序技术详细分析了健康和患病大黄鱼的胃、幽门盲囊和肠道中微生物群的组成信息和分布特征。研究显示,变形菌门、拟杆菌门和厚壁菌门为健康和患病大黄鱼消化道的优势菌门,且其丰度在两类鱼消化道中差异显著。拟杆菌属和乳杆菌属为健康大黄鱼消化道的主要优势菌属;Aliivibrio和弧菌属则为病鱼消化道的主要优势菌属。患病鱼消化道各部位中Aliivibrio的丰度是健康大黄鱼的1702.83~10957.55倍,且差异显著。健康鱼消化道微生物参与的部分代谢通路的基因数目与病鱼样本存在显著差异。大黄鱼消化道菌群和环境菌群相似性分析及主要菌群分布特征显示,饲料中微生物群对消化道菌群的影响相对较大,说明包括饲料在内的环境微生物的卫生质量在健康养殖中的作用非常关键。通过研究推断Aliivibrio和弧菌属为主要病原菌,养殖过程中维持鱼体消化道微生物群的动态平衡对机体健康至关重要,本研究为大黄鱼健康养殖中疾病的定向防控提供了参考。 相似文献
15.
T Christiansen K Kinnberg P Bjerregaard B Korsgaard 《Marine environmental research》2000,50(1-5):213-216
Estrogenic chemicals are known to have marked effects on the reproductive system of male fish. Finding useful markers of reproductive effects are therefore of great importance and interest. gamma-Glutamyl transpeptidase (gamma-GTP) is a possible marker of Sertoli cells in testes of fish. In the present study we have examined the relationship between the activity of gamma-GTP and the histological structure of the Sertoli cells in testes of five fish species (guppy, Poecilia reticulata; platyfish, Xiphophorus maculatus; eelpout, Zoarces viviparus; rainbow trout, Oncorhynchus mykiss; flounder, Platichthys flesus). In general we found that the more distinct the Sertoli cells the higher the activity of gamma-GTP. 相似文献
16.
《Marine Chemistry》2007,103(1-2):172-184
Here we report on temporal changes in the concentration and composition of lignin phenols in high molecular weight (< 0.2 μm, > 1 kDa) dissolved organic matter (HMW DOM) collected from the lower Mississippi and Pearl Rivers (MR and PR) (USA). Monthly water samples were collected at a station in the lower reach in each river from August 2001 to August 2003. Significantly higher concentrations of lignin and Λ8 values (mg lignin phenols in 100 mg organic carbon) in the Pearl River than in the Mississippi River, reflected sporadic inputs of terrestrial DOM during rainstorm events from wetlands and forest soils. Larger seasonal variations in lignin concentration and composition in the Pearl River, compared to the Mississippi River, were attributed to shifts in organic matter sources from topsoil inputs during rainstorm events to groundwater inputs and in situ production during base flow in this small river. Conversely, lower Λ8 and vanillic acid to vanillin ratios [(Ad/Al)v] in the HMW DOM of the lower Mississippi River may be a result of a lower export rate of lignin from agricultural soils due to lower carbon storage in the expansive agricultural systems of the Mississippi River watershed, as well as dilution of phytoplankton DOM inputs. Large seasonal changes in lignin concentration and Λ8 (linked at times with river discharge), and minimal variability in the composition of lignin phenols, likely represented an integrated signal of soil-derived vascular inputs from the upstream drainage basin. If we are to better understand the controls of organic matter delivery to the coastal zone from both small and large rivers, sampling strategies need to be adjusted to account for the different scales of hydrologic response time and in situ processing associated with different residence times. 相似文献
17.
Microbial community respiration and structure of dead zone sediments of Omura Bay, Japan 总被引：1，自引：0，他引：1
Minoru Wada Shotaro Suzuki Tadashi Nara Yu Umezawa Motohiro Shimanaga Kazumi Matsuoka Hideaki Nakata 《Journal of Oceanography》2012,68(6):857-867
Monitoring sediment microbial community metabolism and structure is instrumental to understanding biogeochemical processes in and ecological impacts on bottom environments. The aim of this study was to determine potential community respiration and to reveal community dynamics of the microorganisms in the dead zone sediments of Omura Bay, Japan. The bay is highly enclosed and develops severe hypoxia in the central regions every summer. We collected sediment core samples from the center of the bay during hypoxia, estimated sediment oxygen consumption by using an adapted in vivo electron transport system activity (in vivo ETSA) assay, enumerated abundance of bacteria, and analyzed bacterial community structure by automated ribosomal intergenic spacer analysis. Higher ETSA and bacterial diversity were found in upper sediments (within 3?cm depth) from the center than the fringe of the bay. Sediment bacterial community structure of the bay center was distinct from that of the fringe. From these results, upper sediment in the dead zone of Omura Bay was characterized by (1) greater community respiration and (2) greater diversity of bacterial components compared with the non-hypoxic sediment of the bay fringe. These characteristics have important implications for understanding the interaction between microbial communities and the development of hypoxia in Omura Bay. 相似文献
18.
S. G. Boguslavskii S. I. Kazakov E. V. Berestovaya M. V. Boguslavskaya 《Physical Oceanography》2007,17(6)
On the basis of generalization of the data of many-year hydrological observations and the data of meteorological satellites
accumulated in recent years, we characterize some specific features of the surface temperature in the Tropical Atlantic. The
influence of solar radiation, local heat balance, and the advective and diffusion heat transfer on the temperature of the
water surface is analyzed. The mechanism of formation of the thermohalocline and local sites of elevated temperature near
the estuaries of large rivers (such as the Amazon, Orinoco, Mississippi, Congo, and Niger) is described. We also characterize
the formation of the seasonal variability of the near-equatorial temperature maximum, equatorial temperature minimum, and
equatorial divergence rate.
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Translated from Morskoi Gidrofizicheskii Zhurnal, No. 6, pp. 28–38, November–December, 2007. 相似文献
19.
20.
David L. Ruple 《Estuarine, Coastal and Shelf Science》1984,18(2):191-208
Larval fishes were collected from the surf zone of Horn Island, Mississippi between March 1978 and April 1979. A standardized total of 39 435 larvae were taken from 222 collections in the inner and outer surf zone regions, representing fish in 69 taxa. Overall, considerably more larvae were collected in the outer surf zone (78·3%) than in the inner surf zone (21·7%). Engraulids, Chloroscombrus chrysurus and Symphurus spp. were the most abundant larvae taken from the outer surf zone while engraulids, Leiostomus xanthurus, Brevoortia patronus and Trinectes maculatus were the numerically dominant larvae in the inner surf zone. Seasonal peaks in abundance occurred at the outer surf zone stations during May and June and at the inner surf zone stations during December. Larval densities were significantly greater in night collections than in day collections.The occurrence of early larvae, late larvae and juveniles suggests that the surf zone habitat is important to several species of coastal marine fishes. Menticirrhus littoralis, Harengula jaguana and Trachinotus carolinus appear to most readily utilize the surf zone as a nursery area. 相似文献