Somatic and population growth responses of Ceriodaphnia dubia and Daphnia pulex (Cladocera) to changes in food (Chlorella vulgaris) level and temperature

We quantified the combined effects of three food levels (0.01 x 10(6), 0.1 x 10(6) and 1.0 x 10(6) cells ml(-1)) and three temperature levels (15, 20 and 25 degrees C) on the somatic and the clonal population growth of two cladocerans Ceriodaphnia dubia and Daphnia pulex for 24 to 42 days. The somatic growth data showed that both the cladoceran species began to increase their body size within 3 days and remained stable beyond a week. Food density had a significant effect on the body size of C. dubia while for D. pulex, food level and temperature as well as their interaction had significant effect on the body size. The population growth of both the cladoceran species was affected by temperature. At 15 degrees C, C. dubia showed little growth at the highest food density, while at low food level, there was some increase in the population abundances, especially after a long lag phase of about 2 weeks. At 15 degrees C and under the lowest tested food level, the population of D. pulex did not increase beyond the inoculation density. Optimal population growth of D. pulex was observed at intermediate temperature and at 1.0 x 10(6) cells ml(-1) of food level while for C. dubia 25 degrees C and the highest food level yielded highest growth. At low food level and low temperature, the rate of population increase (r) of C. dubia was much lower than that of D. pulex at comparable conditions. On the hand, at higher food levels and temperature regimes, the r of D. pulex was much higher than that of C.dubia. Regardless of the food levels and temperature, the r of C. dubia varied from 0.03 to 0.07 while that of D. pulex varied from 0.01 to 0.08 day(1).     

Combined effects of heavy metal (Hg) concentration and algal (Chlorella vulgaris) food density on the population growth of Brachionus calyciflorus (Rotifera: Brachionidae)

The combined effects of two food levels (0.5 x 10(6) and 1.5 x 10(6) cells ml(-1) of Chlorella vulgaris) and five concentrations (0, 0.000625, 0.00125, 0.0025, 0.005 mg l(-1) of HgCl2) of mercury on the population growth of the rotifer Brachionus calyciflorus was evaluated. The growth experiments were conducted for 18 days at 23+/-1 degrees C under continuous fluorescent illumination. For each food level - heavy metal combination, we maintained 3 replicates. Our data showed that regardless of food level, increase in the heavy metal concentration in the medium resulted in decreased population growth of B. calyciflorus. At any given heavy metal concentration, B. calyciflorus grown under higher food levels had higher population abundance. The rate of population increase was significantly influenced by both the heavy metal concentration and the algal level. The highest population growth rate (0.435+/-0.003 per day) was observed in controls at 1.5 x 10(6) cells ml(-1). The results of this study were discussed in relation to the protective role of algal density against heavy metal toxicity.     

Impact of copper on haematological profile of freshwater fish, Channa punctatus

The present study was to evaluate heavy metal toxicity stress symptoms in fish blood during long-term exposure of sublethal concentration of copper sulphate (CuSO4). The effects of copper on various heamatological parameters were evaluated exposing Indian fresh water fish, Channa punctatus to a sub-lethal concentration of copper sulphate (0.36 mg l(-1)) for different periods. Exposure of fish to copper showed a significant decrease in the haemoglobin (Hb) content from 10.73 to 6.60%, red blood cells (RBC) from 2.86 to 1.84 x 10(6)/mm3 and packed cell volume (PCV) from 31.00 to 23.33% at the end of 45th day as compared to control. Whereas the white blood cells (WBC) increased from 60.00 to 92.48 x10(3)/mm3, clotting time (CT) from 27.66 to 43.00 second, erythrocyte sedimentation rate from 5.0 to 13.66 mm/hr and mean corpuscular volume from 108.11 to 126.85 cmu, significantly, with increase in exposure periods. Although mean corpuscular haemoglobin concentration (MCHC) and mean corpuscular haemoglobin (MCH) values showed significant increase during 15 and 30 days exposures, both the values were found significantly increased at the end of the experimental period. The differential leucocytes count (DLC) showed a significant increase in the populations of lymphocytes and eosinophils, whereas neutrophils, monocytes and basophiles were found decreased after exposure to copper.     

Frequency of abnormal heavy metal blood levels in Wegener's granulomatosis

Previous studies suggested environmental exposures, including mercury (Hg) and lead (Pb), may be related to Wegener's granulomatosis. In this study, investigations were extended to include the measurement of heavy metals in blood samples from patients diagnosed with Wegener's. Diagnosis was confirmed by using the 1990 Classification Criteria for Wegener's granulomatosis established by the American College of Rheumatology (ACR). Using commercial lab testing, whole blood heavy metal screenings were obtained from patients, and results were then compared with validated subject self-report questionnaire estimates of exposure. Thirty-eight Wegener's patients were enrolled; 10 of the 38 exhibited abnormal lab values. In those 10 subjects 3 had elevated nickel (Ni), 7 with increased cobalt (Co), 3 with higher manganese, 1 with elevated copper, and 1 with increased Hg. Overall, the questionnaire results did not correlate with the blood heavy metal analysis. Approximately 26% of Wegener's subjects in this study displayed abnormal heavy metal levels. These findings are likely underestimates since blood levels are an insensitive means for assessing total body burden of heavy metals. From these preliminary studies it appears that elevated Co is a common finding in Wegener's patients but Ni and Hg were also found to be increased. The proportion of patients with abnormal heavy metal levels is more than expected by chance alone. In order to yield more definitive results, further analysis is needed with a larger data set, more controls and more sensitive measurements (hair, urine, or nail samples).     

Legacies and health risks of heavy metals,polybrominated diphenyl ethers,and polychlorinated dibenzo-dioxins/furans at e-waste recycling sites in South China

● Heavy metals and organic toxins may persist in legacy sites for a long time. ● Contaminants pose potential harms to the nearby community (HI > 1). ● PCDD/Fs had the risk of endocrine disruption and reproductive risk. ● Further intervention is needed to reduce pollution and related risks. Informal electronic-waste (e-waste) recycling sites pose substantial health risks to surrounding environments and populations, yet they are not properly regulated. In this study, the soil levels of copper, lead, cadmium, eight polybrominated diphenyl ethers (PBDEs), and 18 polychlorinated dibenzo-dioxins/furans (PCDD/Fs) were measured at two e-waste recycling sites in South China between 2014 and 2019. Both sites have been abandoned for natural restoration. Our results indicate that the mean Cd and PCDD/F levels at Site A in 2019 were higher than those recommended by current safety guidelines. Meanwhile, the highest exposure among children was 1.36 × 10⁻² mg/(kg·d) for Cu, followed by 5.05 × 10⁻³ mg/(kg·d) for Pb, 9.71 ng/(kg·d) for PBDEs, and 6.82 ng TEQ/(kg·d) for PCDD/Fs. Children were at elevated risk for health problem posed by Pb and Cu exposure at both sites (hazard quotient > 1) and by PCDD/Fs at Site A. Further risk assessment was conducted on the target organs and endpoints of heavy metals and PCDD/Fs. The hazard index (HI) for the target organ mixed-risk of heavy metals was high (HI = 1.27), as was that of PCDD/Fs (HI = 1.66), which can disrupt endocrine function and pose a risk of reproductive toxicity in children. Owing to incomplete cleaning, contaminants persist in soils over long periods and may harm nearby environments and communities. Our study demonstrates that heavy metal, PBDE, and PCDD/F contamination have not yet been remediated, and intervention is needed to reduce pollution and associated risks in areas affected by e-waste.     

Biokinetic modeling of heavy metals in earthworms

Studies concerning bioaccumulation kinetics and bioconcentration factor (BCF) of heavy metals like zinc (Zn), lead (Pb), chromium (Cr), cadmium (Cd), and copper (Cu) in earthworm Eudrilus eugeniae tissues including integument, gizzard, clitellum, and head region were undertaken. Calculated BCF, predicted K _ow, and predicted K _oc showed a significant correlation between heavy metals in different earthworm tissues, in substrate spiked with heavy metals. The regression coefficient (r ²) between heavy metal uptake concentration and exposure time varied between 0.73 and 0.99, indicating significant correlation. The K _oc was a maximum of 13.9016 in case of Cu and integument at an exposure time of 100 days and a minimum of 0.1114 in case of Cr with respect to head at the same exposure time. Earthworms accumulated heavy metals following chronic exposure to municipal solid waste containing heavy metals. BCF and uptake rate kinetics of heavy metals were calculated and showed increased values in head tissue followed by integument.     

Effect of hypoxia on the circulating levels of essential mineral elements in rats

Changes occurring in concentrations of certain trace metals and electrolytes viz. chromium, copper, zinc, sodium, potassium, calcium, magenesium and chloride in plasma of rats exposed to intermittent hypobaric hypoxia were evaluated. Batches of Sprague-Dowley rats (12 in each group) were exposed for 1, 7,14 and 21 days to a simulated altitude 7,620 m for 6 h per day and one group of unexposed animals was kept as control. There was a significant rise of 153% in plasma chromium levels of 1 day exposed group in comparison to the unexposed group which tends to normalise on subsequent exposure. There was a gradual increase in plasma copper levels of 9.0, 28.2, 62.6 and 65.6% respectively in 1,7,14 and 21 days exposed rats in comparison to unexposed rats. On the other hand plasma zinc levels were seen to be decreasing during entire exposure. Plasma sodium levels decreased initially in 1 and 7 day exposed rats and increased in later groups whereas plasma potassium levels of exposed groups remained low in comparison to unexposed group. Chloride levels were found to be elevated in 14 and 21 day exposed groups. The plasma calcium and magnesium levels were higher in all exposed groups over unexposed groups. Changes in chromium, copper and zinc observed in the present study during exposure to hypoxic stress may be responsible for the hyperglycemia and anorexia encountered during intial phase of high altitude acclimatisation.     

Eco-friendly approach for leaching out heavy metals from sewage sludge

Sewage sludge contains rich organic matter and nutrients essential for the growth of plants but the presence of toxic heavy metals restricts its land application. To overcome this, the study aims an eco-friendly approach for leaching out heavy metals. Sewage sludge from sewage treatment plant, Chennai, India was characterised. The analysis of total heavy metal concentration was done by digesting in nitric acid and different forms were extracted by community bureau of reference sequential method. Heavy metals: As, Cd, Cr, Cr, Ni, Pb and Zn were determined using inductively coupled plasma optical emission spectrometry Perkin Elmer Optima 5300 DV. The experimental set-up for heavy metal leaching was held for five consecutive days at different concentrations of humic acid (0.1%, 0.5% and 1%) at varied pH (5–9). Results revealed that at the end of fifth day at pH 8, 1% humic acid is capable of leaching out 75.5% cadmium, 66.0% nickel, 52.0% lead, 51.2% zinc, 31.2% copper and 8.5% cadmium from sewage sludge. Statistically positive correlation (0.7088) existed between the percentage of heavy metals leached out and the sum of soluble and reducible fractions. Thus, from ecological point of view, humic acid can be used to leach out heavy metals from sewage sludge serving the need in restoration of soil fertility upon land application.     

干旱区绿洲灌漠土Cu、Zn和Pb的吸附解吸特征

土壤重金属吸附解吸是影响土壤系统中重金属移动性和归宿的主要过程,影响重金属的生物有效性以及重金属在食物链中的传递等.配制一系列不同浓度的重金属,灌漠土对重金属溶液进行吸附实验24 h以达到平衡,再用硝酸铵和乙酸铵进行解吸实验24 h以达到平衡.利用热力学吸附平衡法,对西北干旱区绿洲灌漠土重金属Cu、Ni和Pb的吸附解吸行为进行序批实验研究.实验结果表明:(1)灰漠土在常温下对铜、锌和铅重金属离子的吸附等温线符合Freundlich型吸附模式,灰漠土对重金属铜、锌和铅的吸附能力由强到弱的顺序为:铅,铜,锌.(2)硝酸铵和乙酸铵解吸重金属的量与灰漠土吸附重金属量呈现出线性正相关,乙酸铵解吸重金属的量比硝酸铵解吸重金属的量大,两种解吸剂对铜、锌和铅重金属离子的解吸能力由大到小的顺序都为:铜,锌,铅,说明了一般外源的铜、锌和铅进入土壤以后,铜和锌可能比铅容易向四周转移.(3)硝酸铵和乙酸铵的解吸率呈谷形曲线,开始时硝酸铵和乙酸铵解吸重金属量的百分比随灰漠土吸附重金属量的增加而减小,在吸附量达到某一特定值时,解吸率随吸附量的增加而增加.灰漠土对铜、锌和铅的吸附作用以专性吸附为主,被灰漠土吸附的铜、锌和铅重金属离子较难解吸.     

Natural variations in tissue concentration of copper,zinc and iron in the polychaete Nereis diversicolor

This study was undertaken to investigate the natural variation of heavy metals in the polychaete Nereis diversicolor O. F. Müller and to examine this variation with respect to physiological and environmental parameters. During a 2 yr period from October 1980 to October 1982, concentrations of copper, zinc and iron in N. diversicolor from the Tees Estuary, North East England, were found to vary significantly with time. A seasonal influence on whole body copper concentration, in part related to the reproductive cycle, was observed. Zinc concentrations in N. diversicolor increased during periods of rapid growth and may represent a physiological demand for this metal. Whole body concentrations of iron appeared to be independent of size of worm, sexual maturation and sediment concentrations.     

Effects of Tourists on Behavior and Demography of Olympic Marmots

Abstract:  If changes in animal behavior resulting from direct human disturbance negatively affect the persistence of a given species or population, then these behavioral changes must necessarily lead to reduced demographic performance. We tested for the effects of human disturbance on Olympic marmots ( Marmota olympus ), a large ground-dwelling squirrel that has disappeared from several areas where recreation levels are high. We assessed the degree to which antipredator and foraging behavior and demographic rates (survival and reproduction) differed between sites with high recreation levels (high use) and those with little or no recreation (low use). Compared with the marmots at low-use sites, marmots at high-use sites displayed significantly reduced responses to human approach, which could be construed as successful accommodation of disturbance or as a decrease in predator awareness. The marmots at high-use sites also looked up more often while foraging, which suggests an increased wariness. Marmots at both types of sites had comparable reproductive and survival rates and were in similar body condition. Until now, the supposition that marmots can adjust their behavior to avoid negative demographic consequences when confronted with heavy tourism has been based on potentially ambiguous behavioral data. Our results support this hypothesis in the case of Olympic marmots and demonstrate the importance of considering demographic data when evaluating the impacts of recreation on animal populations.     

Contribution to the ecotoxicological study of cadmium,copper and zinc in the mussel Mytilus edulis

A regulation of internal levels of some essential metals has been observed in various animals, whereas the bioaccumulation of several non-essential metals parallels their overloads in water. In the mussel Mytilus edulis L., we have attempted to determine if such a phenomenon exists by comparing the patterns of accumulation of copper and zinc vs cadmium. With this aim, mussels collected in the Bay of Bourgneuf (France) in November 1983 were exposed to these metals for 16 d. At external levels of zinc as high as 100 gl^-1, mussels were able to maintain a normal concentration in all groups of organs for 4 d. The ability of mussels to limit the bioaccumulation of copper and zinc varied from organ to organ, and decreased with higher levels of contamination and longer periods of exposure. In contrast, at the lowest experimental concentration and the lowest period of exposure, a significant increase of cadmium in mussel tissues was generally observed. Even at the highest sub-lethal doses, the levels of copper and zinc in mussel tissues were not much higher than the natural levels (contaminated:background ratios= 2.3 to 6.1), whereas the bioaccumulation of cadmium was less well restricted (contaminated:background ratios=136 to 192). The use of mussels as a bioindicator of pollution seems doubtful for essential metals, particularly as regards short-term pollution, since the levels of these trace elements in the organisms are largely independent of their concentration in the ambient seawater.     

Relationship of life-history patterns to depth in deep-water caridean shrimps (Crustacea: Natantia)

Deep-water shrimps, distributed on the steep outer reef slopes of tropical Pacific Islands, were obtained by setting baited traps in depths down to 850 m in the vicinity of Laucala Bay, Fiji, over the period 1979 to 1983. Life-history variables were estimated and interspecific comparisons made between Parapandalus serratifrons, Plesionika longirostris, Heterocarpus ensifer, H. gibbosus, H. sibogae, H. laevigatus (Pandalidae) and Saron marmoratus (Hippolytidae) which have different depth distributions. Results suggested that, interspecifically, reproductive lifespan tended to increase with increasing depth of distribution and that mean egg sizes of each species increased with increasing depth. Brood sizes tended to increase inconsistently with depth, although relative brood size (number of eggs per “standar” 15 g individual) appeared unrelated to depth. Although annual reproductive effort varied inconsistently with depth, reproductive effort totalled over the lifespan of the Heterocarpus species tended to increase with increasing depth. Some of the findings are counter to competition-based ecological theory, and it is proposed that adult predation decreases with increasing depth, allowing deeper-water species to have an extended lifespan, an increased degree of iteroparity, and a corresponding increase in lifetime reproductive effort. Further, we suggest that the probabilities of larval survival, which appear to decrease with increasing depth, are offset by the production of larger eggs by deeper-water species.     

The concentration of Cu and Pb in the funnel spider Eratigena atrica (C. L. Koch 1843) (Araneae: Agelenidae) and its web

Studies on the heavy metal concentrations on spider webs in relation to the pathways of pollution penetration (external and internal) have yet to be performed. This work assesses the concentration levels of two heavy metals: essential copper (Cu) and toxic lead (Pb) in spider webs and spiders (females, males and juveniles). Spiders divided into three treatment groups were exposed to the heavy metals in their diet as prey (fruit flies and mealworms larvae) were artificially contaminated with Cu and Pb. In general, we found higher rates of Cu compared to Pb concentrations in spiders and their webs. A positive correlation between levels of Cu and Pb in webs and spiders was found. Males had higher concentrations of both metals Cu and Pb in their bodies and webs compared to females. In an additional experiment, washed webs had significantly less metals than unwashed suggesting the dominance of external pollution in the contamination pathway.     

Effects of paternal care on reproductive success in the polygynous spotless starling Sturnus unicolor

For males of socially polygynous avian species like the spotless starling, there may exist a trade-off between investing in paternal care and controlling several nests. To determine how the intensity of paternal care affects reproductive success per brood sired or expressed as the total number of young raised in all nests controlled by the same male, it is necessary to manipulate paternal care. Testosterone (T) has been shown to depress the tendency for males to care for their young, and induces them to acquire more mates. The effects of paternal care on reproductive success were studied by treating certain male starlings with exogenous T and others with the antiandrogen cyproterone acetate (CA), and comparing the parental behavior of T- and CA-males throughout the breeding season with that of controls. CA-males fed their chicks more during the first week after hatching than T-males, with controls feeding at intermediate rates, both on a per nest basis and as total effort for all nests controlled by the same male. Paternal feeding rates during the first week of chick life had a significant positive effect on the number of fledged young. The hormone treatment significantly affected the number of chicks raised per nest, CA-males having a higher breeding success per nest than T-males, and controls showing intermediate levels of success. There was no significant effect of treatment on total reproductive success attained by males throughout the season. In the polygonous spotless starling, the intensity of paternal care of young affects reproductive success per nest positively but not on a seasonal basis. Received: 6 February 1999 / Received in revised form: 30 June 1999 / Accepted: 11 July 1999     

Patterns of trace-metal distribution in tissues of Pleoticus muelleri (Crustacea: Decapoda: Solenoceridae)

Trace-metal distribution in tissues of the shrimp Pleoticus muelleri Bate from the Patagonian region, Argentina, was related to sex, size and physiological condition. Concentrations of cadmium, copper, manganese and zinc were determined in the digestive gland, male reproductive system and muscle of adult specimens. Significant (p<0.01) sex-dependent differences in mean metal concentrations (g g^-1 wet wt) were found in the following tissues of males and females, respectively: digestive gland, Cu, 82.9 and 30.8; Zn, 32.5 and 44.9; reproductive system, Zn, 12.8 and 38.6; Mn, 1.7 and 3.1; Cd, 0.29 and 0.58. Metal levels of muscle showed no significant differences between sexes. Cadmium was not detected in muscle, suggesting that its incorporation into this tissue was strictly regulated. Metal concentrations in the male reproductive system were in general weakly correlated (0.001<p<0.05) with either body size or the concentration of metals in the digestive gland. The developing ovary incorporated substantial amounts of zinc, while cadmium and copper levels decreased at proportional rates (p<0.001). The patterns of the variations in the concentrations of these metals in the ovary strongly suggested that a regulatory mechanism operated throughout oogenesis. Manganese was not involved in this presumptive mechanism. The results of this study are discussed in terms of concentrations and in absolute amounts for standardized individuals.     

Protective effects of curcumin on antioxidant status,body weight gain,and reproductive parameters in male rats exposed to subchronic 2,3,7,8-tetrachlorodibenzo-p-dioxin

The aim of this study was to investigate the effects of curcumin (CUR) on antioxidant status, body weight (BW) gains, and some reproductive parameters in male rats exposed to subchronic doses of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Thirty-two rats were divided into four groups. The first group was kept as control. The second group (TCDD group) was given TCDD at a dose of 50 ng·kg^?1 BW per day; the third group (CUR group) was treated with CUR at a dose of 80 mg·kg^?1 BW per day. The fourth group (TCDD + CUR group) was given TCDD and CUR at the same doses simultaneously. Malondialdehyde (MDA) levels were significantly increased in the TCDD group. In addition, TCDD exposure decreased liver superoxide dismutase (SOD) activity, catalase (CAT) activities of kidney and brain, glutathione peroxidase (GSH-Px) activities of liver, kidney, and brain, and glutathione levels of liver, kidney, and heart. However, CUR treatment with TCDD exposure decreased MDA levels in all tissues and increased SOD activities of liver, kidney, and brain, CAT activity of heart, and GSH-Px activities of heart and brain. TCDD caused a decrease in BW gain, and CUR partially eliminated this effect of TCDD. In addition, while reproductive organ weights, sperm concentration, and sperm motility tended to decrease with TCDD exposure, these effects tended to be close to normal levels by CUR treatment. In conclusion, CUR was seen to be effective in the treatment and prevention of toxicity induced by subchronic TCDD exposure.     

No zone is always greener: variation in the performance of<Emphasis Type="Italic"> Fucus gardneri</Emphasis> embryos,juveniles and adults across tidal zone and season

The responses of the different stages of an organisms life-cycle to different environments can have important implications for their persistence in those habitats. The marine intertidal zone is considered among the most stressful of all marine environments, because daily exposure at low tide results in daily fluctuations in a range of important environmental factors. In this study we examined the link between daytime exposure and the performance of embryos, juveniles and adults of the seaweed Fucus gardneri across zones and seasons on San Juan Island, Washington, USA. Specifically we asked: (1) whether three measures of performance for F. gardneri: growth rates, surface area of reproductive tissue and survivorship differed between high- and mid-intertidal zones, and among months throughout the year and, then, (2) whether total daytime exposure within each zone each month was a good predictor of variation in these measures of performance. At our study site, seasonal differences in the timing of low tides result in long periods each day during summer of very harsh conditions (exposure to the air, high temperatures and low humidity) compared to winter when exposure to the air during the day is virtually absent. Contrary to the expectation of lower performance in the high zone, we found no consistent differences between zones over the entire year in any measure of performance for any stage. For nearly all traits, there were significant differences among months and, importantly, significant interactions between zone and month. Thus, for each stage there were some months when thalli in the high zone performed better and some months when thalli in the mid-zone performed better. Regressions between total daytime exposure and performance each month indicated some stage-specific effects. Larger thalli appeared more strongly affected by the amount of exposure per month; there were significant negative relationships between total daytime exposure and (1) growth rates of medium and large adults in the high zone and (2) the surface area of reproductive tissue of medium adults in the high zone and small adults in the mid-zone. The lowest survivorship for all stages occurred in the 2–3 months that followed summer, suggesting a cumulative effect of long daytime exposure in summer on survivorship. Post-settlement survivorship of embryos was very low throughout the year, with only 2 out of 5395 seeded zygotes surviving to a visible size. One-month post-settlement survivorship ranged from 0% to 16.7%, and there were no differences in the survivorship curves between high- and mid-intertidal zones for each cohort. Although it is often assumed that the performance of intertidal species is lower in high-intertidal zones because of exposure to environmental extremes for longer, our results do not support this paradigm. Instead, they indicate a complex and fluctuating pattern of variation in the performance of different stages of the F. gardneri life-cycle throughout the year in different intertidal zones.Communicated by M.S. Johnson, Crawley     

Long-term changes in populations of subtidal bivalves (Abra alba and A. prismatica) from the Bay of Morlaix (Western English Channel)

Two populations of Abra alba (Wood) and one of A. prismatica (Montagu) (Mollusca: Bivalvia) were studied over a 10 yr period (1977–1987) in two muddy fine-sand subtidal communities of the Bay of Morlaix, France. The survey provided an example of long-term changes in the three Abra spp. populations, which displayed synchronized changes, with a regular annual cycle and increasing densities during 1979–1980 related to the higher concentration of organic matter resulting from the Amoco Cadiz oil spill in March 1978. A. alba rapidly adapts its demographic strategy to eutrophic conditions by increasing its reproductive potential, growth, and abundance. During times of eutrophication, A. alba has three spawning periods and three recruitments per year as opposed to two spawning periods and two recruitments per year during oligotrophic conditions. Growth of the juveniles of this species is insignificant until spring for individuals recruited in the autumn, whereas individuals which settle during spring or summer display immediate rapid growth. A. prismatica has a low capacity to adapt to eutrophic conditions. It has one annual period of sexual maturation at the end of the summer, with spawning in September–October and settlement beginning in mid-November. Growth of the juveniles after settlement is also insignificant until April. These results enable comparison of the demographic strategies of these two sympatric species.     

Reconstructing the historic demography of an endangered seabird

Reducing extinction risk for threatened species requires determining which demographic parameters are depressed and causing population declines. Museum collections may constitute a unique, underutilized resource for measuring demographic changes over long time periods using age-ratio analysis. We reconstruct the historic demography of a U.S. federally endangered seabird, the Marbled Murrelet (Brachyramphus marmoratus), from specimens collected approximately 100 years ago for comparison with predictions from comparative analyses and with results from contemporary field studies using both age-ratio analysis and conventional demographic estimators. Reproduction in the late 1800s and early 1900s matched predictions from comparative analysis, but was 8-9 times greater than contemporary estimates, whereas adult survival was unchanged. Historic reproductive rates would support stable populations, but contemporary levels should result in population declines. Contemporary demographic estimates derived from age-ratio analysis were similar to estimates from conventional estimators. Using museum specimens to reconstruct historic demography provides a unique approach to identify causes of decline and to set demographic benchmarks for recovery of endangered species that meet most assumptions of age-ratio analysis.