共查询到20条相似文献,搜索用时 31 毫秒
1.
Previous soil lead studies in New Orleans focused on the geochemical footprint and its health impacts. This study examines
the human geography of race, income, and age in pre-Katrina metropolitan New Orleans within the context of lead accumulation
in soils. Sample points of soil lead data (n = 5,467) collected in 1998–2000 were mapped in a geographic information system (GIS), binned into 9 ranges, and queried by
(1) 2000 Census racial demographic data, (2) 1999 median household income, and (3) 2000 age data. The absolute population
generally declines as lead levels increase except at lead levels from 200–400 to 400–1,000 mg/kg when population increases;
the African–American population comprises a disproportionate share of this cohort. The high-lead areas occur in the inner
city, home to the largest populations of African-Americans in New Orleans. The mean household income curve indicates that
lower economic groups are at risk to higher levels of lead. A total of 44,701 children under the age of 5 years, plus 123,579
children aged 5–17, lived in census block groups containing at least one sample point with over 100 mg/kg lead, and these
include 23,124 and 64,064 young people, respectively, who live near at least one point over 400 mg/kg. Lead exposure affects
a panoply of outcomes that influence the health and welfare of the community. Unless corrected, children are likely to return
to the same or, because of lack of lead-safe practices during renovation, even higher exposure risks than before the flooding
of New Orleans. 相似文献
2.
This study in selected Pakistani populations was conducted to determine the blood lead levels (BLL) in mothers and their developing fetuses. Associated factors were correlated with the maternal BLL. Blood samples from 113 pregnant women and their umbilical cords were examined for BLL and cord blood lead levels through a graphite furnace-attached atomic absorption spectrophotometer. A structured questionnaire was also used to obtain sociodemographic and obstetric data based on basic demographic data, reproductive history, hemoglobin levels, gestational age, parity, mode of delivery, maternal and baby weight, drinking water, menarche age, blood pressure, lead (Pb)-containing eye liner use, smoking, and nutritional status. In order to assess the strength of the relationship between different parameters, Pearson's coefficient correlation was utilized and their significance was determined by applying the t-test. Data demonstrated that the maternal BLL were always higher than the recommended concentrations of 10 µg/dl and many factors contributed towards such results. Drinking water seemed to affect the Pb concentration as women using spring water had relatively higher BLL. The calcium concentration in pregnant women and their fetuses ranged from 9 to 13 mg/dl. Majority of the pregnant women were undergraduates with 12 years of education (equivalent to high school in the United States). Evidence indicates that the avoidance of Pb intake and its associated factors in the study area will diminish risk to newborns. 相似文献
3.
Roongnapa Apinan Soisunwan Satarug Ronnatrai Ruengweerayut Wiratchanee Mahavorasirikul Kesara Na-Bangchang 《Environmental geochemistry and health》2010,32(3):237-242
Cadmium is a toxin of increasing public health concern due to its presence in most human foodstuffs and in cigarette smoke.
Exposure to cadmium leads to tissue bioaccumulation and, in particular, has nephrotoxic effects. The aim of the present study
was to investigate the association between cadmium body burden and iron stores in a Thai population. A total of 182 healthy
adult Thai subjects of both genders (89 males, 93 females) aged between 18 and 57 years and weighing 40–95 kg were included
in this study. The total amounts of cadmium excreted in urine over 2 h (μg/g creatinine) were used as an index of long-term
cadmium exposure. Quantitation of cadmium was performed using electrothermal (graphite furnace) atomic absorption spectrometry.
The urinary cadmium excreted displayed a normal frequency distribution. The average urinary cadmium level did not exceed the
WHO maximum tolerable internal dose for the non-exposed population (2 μg/g creatinine). Body iron stores reflected by serum
ferritin levels did not show any correlation with cadmium burden in both males and females, although a relatively stronger
influence of body iron store status on cadmium burden was shown in females. When the levels of serum ferritin were stratified
into five levels (<20, 20–100, 101–200, 201–300, and >300 μg/l), a significant difference in total cadmium body burden was
observed between females and males only in the group with a low level of serum ferritin of <20 μg/l. The cadmium body burden
in females was about twice that in males in this group. 相似文献
4.
The potential impact of exposure to heavy metals and health problems was evaluated at the Tar Creek Superfund site, Ottawa
County, Oklahoma, USA. Observed versus expected mortality was calculated for selected conditions in the County and exposed
cities. Excess mortality was found for stroke and heart disease when comparing the exposed County to the state but not when
comparing the exposed cities to the nonexposed rest of the County. However, sample sizes in the exposed area were small, population
emigration has been ongoing, and geographic coding of mortality data was incomplete. In an exposed community, 62.5% of children
under the age of 6 years had blood lead levels exceeding 10 μg/dl. The relationships between heavy-metal exposure and children’s
health and chronic disease in adults are suggestive that a more thorough investigation might be warranted. A number of possible
environmental and health studies are suggested, including those focusing on possible central nervous system impacts. Unfortunately,
the exposed population is dispersing. One lesson learned at this site is that health studies need to be conducted as soon
as possible after an environmental problem is identified to both study the impact of the most acute exposures and to maximize
study sample size—including those exposed to higher doses—and minimize the loss of individuals to follow-up. 相似文献
5.
Alecos Demetriades Xiangdong Li Michael H. Ramsey Iain Thornton 《Environmental geochemistry and health》2010,32(6):529-552
In the Lavrion urban area study, Hellas, a five-step sequential extraction method was applied on samples of ‘soil’ (n = 224), affected by long-term mining and metallurgical activities, and house dust (n = 127), for the purpose of studying the potential bioaccessibility of lead and other metals to humans. In this paper, the
Pb concentrations in soil and house dust samples are discussed, together with those in rocks and children’s blood. Lead is
mainly associated with the carbonate, Fe–Mn oxides and residual fractions in soil and house dust. Considering the very low
pH of gastric fluids (1–3), a high amount of metals, present in soil (810–152,000 mg/kg Pb) and house dust (418–18,600 mg/kg Pb),
could be potentially bioaccessible. Consequently, children in the neighbourhoods with a large amount of metallurgical processing
wastes have high blood-Pb concentrations (5.98–60.49 μg/100 ml; median 17.83 μg/100 ml; n = 235). It is concluded that the Lavrion urban and sub-urban environment is extremely hazardous to human health, and the
Hellenic State authorities should urgently tackle this health-related hazard in order to improve the living conditions of
local residents. 相似文献
6.
The objective of this study was to determine the blood lead level (BLL) of children aged under 5 living in western Uttar Pradesh, India. A total of 100 blood samples, 100 drinking water samples, and 21 vegetable samples were assessed for lead (Pb) contamination. BLL was observed in the range of 3–11.58?µg?dL?1 with a maximal level of 11.58?±?0.05?µg?dL?1 in Kazipur village. Lead in water samples was detected in the range of 0.006–0.095?ppm and identified at upto 9.5-fold higher than the stated permissible limit. A significant positive correlation (+0.679) was obtained between BLL and water Pb levels. All vegetable samples were also contaminated with Pb upto 12-fold higher than the permissible limit of 2.5?µg?g?1 of Prevention of Food Adulteration Act (PFA) 1954. Untreated industrial effluents were identified as the responsible factors for Pb occurrence in the study area. The presence of lead may be associated with the increased antisocial activities of children living in western Uttar Pradesh. Children with elevated BLL had poorer nutritional status than those with background Pb levels. There is an urgent need for a national campaign to monitor the BLL of children in India. 相似文献
7.
Incidental soil ingestion is a common contaminant exposure pathway for humans, notably children. It is widely accepted that
the inclusion of total soil metal concentrations greatly overestimates the risk through soil ingestion for people due to contaminant
bioavailability constraints. The assumption also assumes that the contaminant distribution and the bioaccessible fraction
is consistent across all particle sizes. In this study, we investigated the distribution of arsenic across five particle size
fractions as well as arsenic bioaccessibility in the <250-, <100-, <10- and 2.5-μm soil particle fractions in 50 contaminated
soils. The distribution of arsenic was generally uniform across the larger particle size fractions but increased markedly
in the <2.5-μm soil particle fraction. The marked increase in arsenic concentration in the <2.5-μm fraction was associated
with a marked increase in the iron content. Arsenic bioaccessibility, in contrast, increased with decreasing particle size.
The mean arsenic bioaccessibility increased from 25 ± 16% in the <250-μm soil particle fraction to 42 ± 23% in the <10-μm
soil particle fraction. These results indicate that the assumption of static arsenic bioaccessibility values across particle
size fractions should be reconsidered if the ingested material is enriched with small particle fractions such as those found
in household dust. 相似文献
8.
Particle size distribution and pollutants in road-deposited sediments in different areas of Zhenjiang,China 总被引:2,自引:0,他引:2
An understanding of road-deposited sediment (RDS) characteristics on an impervious surface is essential to estimate pollutant
washoff characteristics and to minimise the impacts of pollutants on the water environment. A total of 62 RDS samples were
collected from four different land-use types (commercial, residential, intense traffic and riverside park) in Zhenjiang City,
China. The samples were fractionated into seven grain-size classes and analysed for particle size distribution and concentrations
of pollutants. The samples are found to consist predominantly of fine particles (60–80%, <250 μm). The maximum mean concentrations
of zinc, lead and copper were 686.93, 589.19 and 158.16 mg/kg, respectively, with the highest metal concentrations found in
samples from the intense traffic area. The maximum mean contents of organic matter (12.55%), nitrogen (6.31 mg/g) and phosphorus
(5.15 mg/g) were found in samples from the commercial area. The concentrations of heavy metals were highest in the smallest
particle size fraction analysed (63 μm). The organic matter and nitrogen content generally increased with decreasing particle
sizes in the <500-μm particle size range. The results also revealed that most of the total nitrogen (TN) is attached to the
finer sediments and that to effectively reduce TN loads in particulates, treatment facilities must be able to remove the finer
particles (down to 125 μm for TN). 相似文献
9.
Vladimír Bencko Ji?í Rame? Eleonora Fabiánová Ji?í Pe?ek Marián Jakubis 《Environmental geochemistry and health》2009,31(Z1):239-243
The subject of the study was the ecological and human health consequences of environmental pollution from emissions arising
from burning local coal with an arsenic content ranging from 900 to 1,500 g/tonne of dry substance. The first indication of
environmental pollution by arsenic-containing emissions was the mass extinction of honeybee colonies. The neurotoxic and carcinogenic
aspects of arsenic exposure were followed. On using a group diagnostics approach, significant hearing losses were detected
in exposed children in both air and bone conduction audiometry at high frequency range (4,000 and 8,000 Hz, respectively).
Exposure assessment of the local population of the Prievidza district, Central Slovakia, was based on biological monitoring.
The criterion of higher exposure was arsenic content in hair exceeding concentrations of 3 μg/g of hair. In a 7.5-km radius
of the exposed region, live about two-tenths of the district population who were considered as “exposed” and rest of the district
served as the “reference” population. The subject of our analysis was a database of 1,503 non-melanoma skin cancer (NMSC)
cases (756 in men and 747 in women) collected from 1977 to 1996 in the Prievidza district, Central Slovakia (population ~125,000).
The age standardized incidence of NMSC (each confirmed by histological examination) in non-occupational settings ranged from
45.9 to 93.9 in men and from 34.6 to 81.4 in women. Analysis of our data demonstrates a positive correlation between human
cumulative exposure to arsenic and incidence of NMSC. 相似文献
10.
The EPA lead model predicts mean blood lead levels and risk of elevated blood lead levels in children based on lead uptake from multiple sources. In the latest model versions, environmental data from individual homes within a community can be used to predict the overall blood lead distribution and percent risk of exceeding a specific blood lead level (i.e. 10 g dl–1). Recent criteria used by the EPA to evaluate this information include no more than 5% of houses with a greater than 5% lead risk, and a community weighted-average risk below 5%. Environmental (primarily soil) and blood lead data from a residential community near a smelter were used to illustrate recent uses of the model. Scheduled remediation in the community will remove soil for approximately 60% of the houses (i.e. those with lead levels > 1000 mg kg–1). After remediation, the model results indicate a relatively low community risk (0.5–1.9%), although the percentage of houses with lead risks above 5% ranged from 3 to as high as 13%, depending on the variation in blood lead and assuming the model's 7 g dl–1 increase in blood lead with each 1000 mg kg–1 increase in soil lead level. A comparison of the limited blood lead data with soil lead levels below 1000 mg kg–1, however, indicated no apparent relationship. Given these uncertainties, less invasive actions than additional soil removal (e.g. exposure intervention, monitoring conditions, and follow-up as necessary) may be appropriate under the new EPA guidance for lead in soil. 相似文献
11.
Debapriya Mondal Mayukh Banerjee Manjari Kundu Nilanjana Banerjee Udayan Bhattacharya Ashok K. Giri Bhaswati Ganguli Sugata Sen Roy David A. Polya 《Environmental geochemistry and health》2010,32(6):463-477
Remediation aimed at reducing human exposure to groundwater arsenic in West Bengal, one of the regions most impacted by this
environmental hazard, are currently largely focussed on reducing arsenic in drinking water. Rice and cooking of rice, however,
have also been identified as important or potentially important exposure routes. Quantifying the relative importance of these
exposure routes is critically required to inform the prioritisation and selection of remediation strategies. The aim of our
study, therefore, was to determine the relative contributions of drinking water, rice and cooking of rice to human exposure
in three contrasting areas of West Bengal with different overall levels of exposure to arsenic, viz. high (Bhawangola-I Block,
Murshidibad District), moderate (Chakdha Block, Nadia District) and low (Khejuri-I Block, Midnapur District). Arsenic exposure
from water was highly variable, median exposures being 0.02 μg/kg/d (Midnapur), 0.77 μg/kg/d (Nadia) and 2.03 μg/kg/d (Murshidabad).
In contrast arsenic exposure from cooked rice was relatively uniform, with median exposures being 0.30 μg/kg/d (Midnapur),
0.50 μg/kg/d (Nadia) and 0.84 μg/kg/d (Murshidabad). Cooking rice typically resulted in arsenic exposures of lower magnitude,
indeed in Midnapur, median exposure from cooking was slightly negative. Water was the dominant route of exposure in Murshidabad,
both water and rice were major exposure routes in Nadia, whereas rice was the dominant exposure route in Midnapur. Notwithstanding
the differences in balance of exposure routes, median excess lifetime cancer risk for all the blocks were found to exceed
the USEPA regulatory threshold target cancer risk level of 10−4–10−6. The difference in balance of exposure routes indicate a difference in balance of remediation approaches in the three districts. 相似文献
12.
Graham Bird Mark G. Macklin Paul A. Brewer Sorin Zaharia Dan Balteanu Basarab Driga Mihaela Serban 《Environmental geochemistry and health》2009,31(6):741-758
Groundwater, accessed using wells and municipal springs, represents the major source of potable water for the human population
outside of major urban areas in northwestern Romania, a region with a long history of metal mining and metallurgy. The magnitude
and spatial distribution of metal contamination in private-supply groundwater was investigated in four mining-affected river
catchments in Maramureş and Satu Mare Counties through the collection of 144 groundwater samples. Bedrock geology, pH and
Eh were found to be important controls on the solubility of metals in groundwater. Peak metal concentrations were found to
occur in the Lapuş catchment, where metal levels exceed Dutch target and intervention values in up to 49% and 14% of samples,
respectively. A 700 m wide corridor in the Lapuş catchment on either side of the main river channel was identified in which
peak Cd (31 μg l−1), Cu (50 μg l−1), Pb (50 μg l−1) and Zn (3,000 μg l−1) concentrations were found to occur. Given the generally similar bedrock geologies, lower metal levels in other catchments
are believed to reflect differences in the magnitude of metal loading to the local environment from both metal mining and
other industrial and municipal sources. Sampling of groundwater in northwestern Romania has indicated areas of potential concern
for human health, where heavy metal concentrations exceed accepted environmental quality guidelines. The presence of elevated
metal levels in groundwater also has implications for the implementation of the EU Water Framework Directive (WFD) and achieving
‘good’ status for groundwater in this part of the Danube River Basin District (RBD). 相似文献
13.
Despite its being highly mineralised, the Hope Mine area has become a residential district. Composite soil samples taken from 91 allotments show values for cadmium: < 2–220 mg kg–1, lead: 6–38,000 mg kg–1, and zinc: 66–40,000 mg kg–1. Water samples from adits contain 52–86 g kg–1 of lead and < 1–2 hg kg–1 of cadmium. The soil contents of cadmium and lead in at least two areas suggest that remedial actions should be considered. Blood lead levels for 33 children aged between ten months and seven years are in the range 5.7–57 g dl–1; haemoglobin levels vary between 9.7 and 12.7 mg dl–1. There is no obvious relationship between Pb and haemoglobin levels. Further geochemical work to define fully the spatial extent of the polluted region and epidemiological studies including intelligence testing to define further the effects of lead on children in this environment would be valuable.To whom correspondence should be addressed. 相似文献
14.
The Salí River Basin in north-west Argentina (7,000 km2) is composed of a sequence of Tertiary and Quaternary loess deposits, which have been substantially reworked by fluvial and
aeolian processes. As with other areas of the Chaco-Pampean Plain, groundwater in the basin suffers a range of chemical quality
problems, including arsenic (concentrations in the range of 12.2–1,660 μg L−1), fluoride (50–8,740 μg L−1), boron (34.0–9,550 μg L−1), vanadium (30.7–300 μg L−1) and uranium (0.03–125 μg L−1). Shallow groundwater (depths up to 15 m) has particularly high concentrations of these elements. Exceedances above WHO (2011) guideline values are 100% for As, 35% for B, 21% for U and 17% for F. Concentrations in deep (>200 m) and artesian groundwater
in the basin are also often high, though less extreme than at shallow depths. The waters are oxidizing, with often high bicarbonate
concentrations (50.0–1,260 mg L−1) and pH (6.28–9.24). The ultimate sources of these trace elements are the volcanic components of the loess deposits, although
sorption reactions involving secondary Al and Fe oxides also regulate the distribution and mobility of trace elements in the
aquifers. In addition, concentrations of chromium lie in range of 79.4–232 μg L−1 in shallow groundwater, 129–250 μg L−1 in deep groundwater and 110–218 μg L−1 in artesian groundwater. All exceed the WHO guideline value of 50 μg L−1. Their origin is likely to be predominantly geogenic, present as chromate in the ambient oxic and alkaline aquifer conditions. 相似文献
15.
Historical trends of trace metals in a sediment core from a contaminated tidal salt marsh in San Francisco Bay 总被引:1,自引:0,他引:1
Sedimentation of metals preserves historical records of contaminant input from local and regional sources, and measurement
of metals in sediment cores can provide information for reconstruction of historical changes in regional water and sediment
quality. Sediment core was collected from Stege Marsh located in central San Francisco Bay (California, USA) to investigate
the historical input of trace metals. Aluminum-normalized enrichment factors indicate that inputs from anthropogenic sources
were predominant over natural input for Ag, Cu, Pb, and Zn. Among these, lead was the most anthropogenically impacted metal
with enrichment factors ranging from 32 to 108. Depth profiles and coefficients of variation show that As, Cd, and Se were
also influenced by anthropogenic input. The levels of these anthropogenically impacted metals decline gradually towards the
surface due to regulation of the use of leaded gasoline, municipal and industrial wastewater discharge control, and closure
of point sources on the upland of Stege Marsh. Although trace metal contamination is expected to be continuously declining,
the rates of decline have slowed down. For lead, it is estimated to take 44, 82, and 153 years to decrease to probable effects
level (112 μg/g), the San Francisco Bay ambient surface sediment level (43.2 μg/g), and the local baseline levels (5 μg/g),
respectively. Some metals in surface sediments (0–6 cm) are still higher than sediment quality guidelines such as the probable
effects level. To further facilitate the recovery of sediment quality, more efficient management plans need to be developed
and implemented to control trace metals from non-point sources such as stormwater runoff. 相似文献
16.
Asaad Ahmed Nafees Ambreen Kazi Zafar Fatmi Muhammad Irfan Arif Ali Fujio Kayama 《Environmental geochemistry and health》2011,33(2):203-216
This study was designed to determine the association between chronic arsenic exposure through drinking groundwater and decrement
in lung function, particularly among individuals who do not have signs of arsenic lesions, among an adult population. This
was a comparative cross-sectional study conducted during the months of January to March 2009. One hundred participants ≥15 years
of age in each group, i.e. exposed (≥100 μg/l) and unexposed (≤10 μg/l) to arsenic, determined by testing drinking water samples
(using portable kits), were compared for effects on lung function using spirometry. A structured and validated questionnaire
was administered. Examination for arsenic skin lesions was also done. There was a decline in the mean adjusted FEV1 of 154.3 ml
(95% CI: −324.7, 16.0; p = 0.076), in mean adjusted FVC of 221.9 ml (95% CI: −419.5, −24.3; p = 0.028), and in FEV1/FVC ratio of 2.0 (95% CI: −25.3, 29.4; p = 0.884) among participants who were exposed to arsenic compared to those unexposed. A separate model comprising a total
of 160 participants, 60 exposed to arsenic concentrations ≥250 μg/l and 100 unexposed at arsenic concentrations of ≤10 μg/l,
showed a decrement in mean adjusted FEV1 of 226.4 ml (95% CI: −430.4, −22.4; p = 0.030), in mean adjusted FVC of 354.8 ml (95% CI: −583.6, −126.0; p = 0.003), and in FEV1/FVC ratio of 9.9 (95% CI: −21.8, 41.6; p = 0.539) among participants who were exposed to arsenic in drinking groundwater. This study demonstrated that decrement in
lung function is associated with chronic exposure to arsenic in drinking groundwater, occurring independently, and even before
any manifestation, of arsenic skin lesions or respiratory symptoms. The study also demonstrated a dose-response effect of
arsenic exposure and lung function decrement. 相似文献
17.
Residents in older homes may experience increased lead (Pb) exposures due to release of lead from interior paints manufactured
in past decades, especially pre-1960s. The objective of the study was to determine the speciation of Pb in settled dust from
an urban home built during WWII. X-ray absorption near-edge structure (XANES) and micro-X-ray diffraction (XRD) analyses were
performed on samples of paint (380–2,920 mg Pb kg−1) and dust (200–1,000 mg Pb kg−1) collected prior to renovation. All dust samples exhibited a Pb XANES signature similar to that of Pb found in paint. Bulk
XANES and micro-XRD identified Pb species commonly found as white paint pigments (Pb oxide, Pb sulfate, and Pb carbonate)
as well as rutile, a titanium-based pigment, in the <150 μm house dust samples. In the dust fraction <36 μm, half of the Pb
was associated with the Fe-oxyhydroxides, suggesting additional contribution of outdoor sources to Pb in the finer dust. These
results confirm that old paints still contribute to Pb in the settled dust for this 65-year-old home. The Pb speciation also
provided a clearer understanding of the Pb bioaccessibility: Pb carbonate > Pb oxide > Pb sulfate. This study underscores
the importance of taking precautions to minimize exposures to Pb in house dust, especially in homes where old paint is exposed
due to renovations or deterioration of painted surfaces. 相似文献
18.
A robust and rapid methodology for the determination of iodine by inductively coupled plasma mass spectrometry in environmental
samples is presented. Data were initially obtained for the validation of the analytical measurements, using 17 commercially
available soil reference materials. The methodology was then tested on soil and water samples collected in Afghanistan where
iodine deficiency and its effects are reportedly prevalent. Sample collections were conducted in Greater Kabul; the iodine
in agricultural soils was determined to be in the range of 1.6–4.2 mg/kg and that in water drawn for drinking and irrigation
was found to range from 9.9 to 22.7 μg/L. Samples were also collected in a second region, Nangarhar province, which is located
to the east of Kabul, where goitres in the local population had been reported. The iodine content in soils and water at this
location was 0.5–1.9 mg/kg and 5.4–9.4 μg/L, respectively. The organic content of soils in Kabul was found to be in the range
of 1.9–4.2%; in Nangarhar, organic content ranged from 1.7 to 4.5%. All of the Afghan soils were slightly alkaline at pH 7.6–8.2. 相似文献
19.
Benni W. Hansen Guillaume Drillet Reinhardt M. Kristensen Thomas F. Sørensen Majken T. Tøttrup 《Marine Biology》2010,157(1):59-68
Close to 50 species of marine Calanoid copepods have been reported to produce diapause eggs (Engel and Hirche in J Plankton
Res 26:1083–1093, 2004); eggs that are viable but require a refractory phase before they hatch, sometimes after months. Diapause eggs are often
described as morphologically different with respect to egg membrane ultrastructure and having a thicker egg shell with surface
ornamentation as opposed to the smooth shell found in subitaneous eggs that hatch within days (Belmonte in J Mar Syst 15:35–39,
1998; Chen and Marcus in Mar Biol 127:587–597, 1997; Castro-Longoria in Crustaceana 74:225–236, 2001). Egg production rates, egg surface ornamentation, and hatching success were monitored in large aquaculture fish enclosures
during winter with close to zero water temperatures (N57°). Surprisingly, all female copepods (Acartia spp.—presumably A. tonsa, and Centropages hamatus) produced eggs all through the winter with no obvious pattern with respect to light, temperature and food availability, and
no diapause eggs were observed. However, individual females produced several categories of eggs with or without surface spines
even within the same egg batch as evidenced by scanning electron microscopy (SEM). Four egg categories were distinguishable:
‘no spines’, smooth eggs; ‘short spines’, 5–15 μm long; ‘truncated spines’, with the spine tips cut-off <10 μm long; and ‘long
spines’, up to 30 μm long. All egg categories remained unchanged with respect to surface structures from when we took them
out of the incubation bottles until they hatched. In general, the frequency of ‘no spines’ was 10–40%, and most eggs were
ornamented with ‘short-’ or ‘long spines’. Further, a given egg can be ornamented with all types of surface spines simultaneously,
which might even be a fifth egg category. The different egg categories were all able to hatch within days when exposed to
normoxic conditions suggesting that they were subitaneous. 相似文献
20.
A. Cornils S. B. Schnack-Schiel M. Böer M. Graeve U. Struck T. Al-Najjar C. Richter 《Marine Biology》2007,151(4):1261-1274
A total of 12 feeding experiments were conducted in the northern Gulf of Aqaba during spring (March/April) and autumn (September/October)
2002 at the Marine Science Station (MSS) in Aqaba. Females of three species of clausocalanids were selected: Clausocalanus
farrani, C. furcatus and Ctenocalanus vanus. Natural occurring particle (NOP) larger than 5 μm were investigated as food source. The ambient chlorophyll a concentration at sampling depth (∼70 m) ranged between 0.15 and 1.00 μg chl a l−1 and NOP concentrations ranged between 1.78 and 14.0 × 103 cells l−1 during the sampling periods. The division of particles into five size classes (5–10, 10–20, 20–50, 50–100 and >100 μm) revealed
that most of the particles were found in the size classes below 50 μm (81–98%), while most of the natural occurring carbon
(NOC) was concentrated in the size classes larger than 20 μm (70–95%). Ingestion rates were food density dependent rather
than size dependent ranging between 0.02 and 1.65 × 103 NOP ind−1 day−1 and 0.01 and 0.41 μg NOC ind−1 day−1, respectively, equivalent to a body carbon (BC) uptake between 0.4 and 51.8% BC day−1. The share of the size classes to the total ingestion resembled in most cases the size class composition of the natural particle
community. 相似文献