Differences In Calcium Content Research Articles

Suitability of a superheated steam dryer for drying sardines

The suitability of a superheated steam dryer for drying sardines was investigated. Proximate composition (moisture, crude protein, crude fat, ash, and crude fibre; minerals-calcium, zinc, iron) for fresh, oven dried (OD) at 100 °C, oven dried (OD) at 120 °C and superheated steam dried (SSD) sardines at 120 °C was evaluated and the results reported on a dry matter basis. There were significant differences (p<0.05) in moisture, crude fat, and ash content among fresh and dried samples, but not for crude protein or crude fibre. The crude protein % content of fresh, OD at 100 °C, OD at 120 °C, and SSD, was 78.17, 78.40, 75.77, and 76.05 and crude fibre % was 0.59, 0.12, 0.02, and 0.13, respectively. The SSD sardines had the highest fat content (11.8 %) and the fresh sardines had the lowest (8.1 %). There was a significant difference in calcium content (p<0.05) but not for zinc and iron content. Overall, SSD retained the nutrients of sardines well.

The expression of TRPV6 and PMCA1 in the mid-secretory endometrium of infertile patients with unexplained infertility and endometriosis

Purpose: The goal of this study was to evaluate the expression of transient receptor potential vanilloid 6 (TRPV6) and plasma membrane Ca2+ ATPase 1 (PMCA1) in the endometrium of infertile women with unexplained infertility (UI) and endometriosis (E), and to compare the findings to healthy fertile women.
 Materials and Methods: Endometrial expression of TRPV6 and PMCA1 proteins was evaluated during the mid-secretory phase using the immunohistochemical method, and mRNA levels were measured by real-time PCR. Calcium concentrations were determined using Inductively coupled plasma-mass spectrometry (ICP-MS). 
 Results: TRPV6 and PMCA1 protein expression were significantly increased in both luminal and glandular epithelium of UI or E groups compared to the control group. TRPV6 mRNA expression levels were significantly lower in the UI group (0.525 ± 0.087) compared to the control group (0.809 ± 0.073). There was no significant difference in PMCA1 mRNA expression levels between the groups. Calcium concentration was significantly higher in women with UI (median (Q1-Q3): 50.57 [40.67-51.37], compared to the control group (median (Q1-Q3): 24.29 [20.11-25.55]).
 Conclusion: The present findings demonstrate altered expressions of TRPV6 and PMCA1 mRNA and protein, along with differences in calcium concentration among patients, especially those with the UI during the window of implantation. These differences might potentially be considered as one of the underlying causes of infertility. Further studies are needed to elucidate the functional roles of these channels and to develop new strategies for pharmaceutical intervention in the treatment of infertility.

Biochemical Changes in Salivary pH and Its Correlation to Hemoglobin Levels, Calcium and Phosphate Ion Concentrations among Pregnant Women, Tanzania: A Cross-Sectional Study

Background: Surveys in Tanzania show that pregnant women have a significant burden of oral disease, although there is still little literature on the variation of their intraoral electrolytes. The present study investigated changes in salivary calcium (Ca2+), phosphate (PO43−), and hydrogen (H) ions during pregnancy and the correlation between salivary pH and hemoglobin levels. Methodology: A cross-sectional study involved sixty (60) pregnant women stratified by trimester and twenty (20) non-pregnant women attending an antenatal clinic at Mnazi Mmoja Hospital. Consecutive sampling was used, saliva was collected, and electrolyte levels were measured. Gestation age was the independent variable, whereas saliva pH and calcium and phosphate ion concentrations and hemoglobin levels were the dependent variables. Results: A difference in calcium concentration (z = −3.145, p = 0.001) and salivary pH (t = −2.49, p = 0.014) was observed between pregnant and non-pregnant women. Kruskal–Wallis tests for saliva Ca2+ and PO43− and ANOVA for saliva pH revealed differences in concentrations of saliva Ca2+, PO43−, and pH levels between trimester groups (saliva Ca2+ (H = 9.91, df = 3, p = 0.019), saliva PO43− (H = 12.36, df = 3, p = 0.006), saliva pH (F (3.76) = (16.42); p < 0.001)). Pearson’s correlation tests showed no association between salivary pH and hemoglobin levels. Conclusions: Pregnancy is associated with a reduction in saliva pH and saliva calcium levels with a progressive increase in the magnitude of reduction from the first trimester to the third trimester. Saliva phosphate reduction was noticed during the third trimester only and saliva pH levels were independent of hemoglobin levels.

Nutritional value, sensory properties, and antioxidant activity of a traditional kefir produced with Arthrospira platensis

Arthrospira platensis is a microalgae generally known as a source of bioactive compounds and protein. The aim of this study is to evaluate the nutritional value, sensory characteristics, and antioxidant activity of traditional kefir by addition of A. platensis. In the study, the traditional kefir samples were prepared by the addition of A. platensis at 0.05%, 0.1%, 0.5%, 1%, and 2% (w/v) by considering generally recommended daily intake rate and consumer's acceptability. The sensory analysis scores showed that kefir with 0.05% and 0.1% A. platensis have the highest score, in which case the protein in the kefir slightly increased from 27 to 37 mg/ml. The addition of 1% A. platensis to kefir was found to increase amino acid contents. Some slight differences in calcium content were observed; however, there was a fourfold increase in iron. Palmitic and oleic acids (28.94% and 19.04%) were the most abundant fatty acids. The result indicated that A. platensis addition increased the antioxidant activities (FRAP and DPPH) of kefir, and addition of traditional kefir by A. platensis is a suitable way to increase the nutritional value of kefir. Practical applications Kefir is well-known, nutritional and functional fermented beverage that has a unique taste and high nutritional quality. Arthrospira platensis also is known to have been consumed since ancient times and has come to the fore especially in recent years due to its essential amino acids, fatty acids, vitamins, and minerals. Although both, kefir and A. platensis, have strong and weak sides, adding different levels of A. platensis to traditional kefir increased amino acid contents, iron, fatty acid, and antioxidant activities. In this study, the nutritional effects of the addition of an acceptable level of A. platensis to traditional kefir were reported.

Comparison of calcium concentration in scales and vertebral column of a cyprinid from calcium-limited environments in the Lake Victoria Basin, Uganda

Despite dramatic differences in calcium concentrations within aquatic systems, very few studies have explored the relationships between ambient calcium concentration and the calcium concentration of resident fish under natural conditions. This study compares calcium concentration in the water to that of the scales and vertebral column of the African cyprinid, Rastrineobola argentea from lakes Nabugabo and Victoria, East Africa. The concentration of calcium in Lake Nabugabo, which averaged 1.50 mg l−1, was much lower than the average of literature-derived values for the Ugandan portion of Lake Victoria (6.96 mg l−1). Rastrineobola argentea from Lake Victoria were characterised by higher levels of calcium in the scales than that of conspecifics from Lake Nabugabo, whereas there was no difference in vertebral column calcium concentration between the two populations. Within Lake Nabugabo, calcium concentration was lower in the scales than in the vertebral column of R. argentea, whereas no difference was detected between the scalar and vertebral calcium concentrations of conspecifics from Lake Victoria. These results suggest that ambient calcium concentration may affects tissue levels and that fish in Lake Nabugabo may remobilise calcium from their scales to maintain skeletal growth and development.

Lower calcium levels in hair of Parkinson’s disease patients are associated with presence of sleeping disturbances

ABSTRACT Objectives: To investigate the correlation between sleep disorders and the concentrations of three metals analyzed from hair samples of PD patients.The hypothesis of an involvement of an imbalance of metals in the development of Parkinson’s Disease (PD) has been strengthened by several clinical chemistry studies. Interestingly, while sparse, some studies have correlated the imbalance of metals in PD patients with comorbidities present in this disease. Although not all PD sufferers present sleep disturbances, significant disorders of sleep are common in this population. Methods: Sleep evaluation was divided into three parameters: sleep quality, excessive daytime sleepiness and clinically probable REM Sleep Behavior Disorder. Flame atomic absorption spectrometry (F AAS) was used to assess the concentrations of calcium, iron and zinc in hair samples collected from a population of PD patients registered in a Brazilian city and from controls (a total of 53 subjects). All subjects lived within a restricted geographical region and were exposed to similar environmental conditions. Results: PD patients with poor sleep quality and excessive daytime sleepiness exhibited significant differences in concentrations of calcium, but not iron or zinc when compared to levels found in controls and PD patients who do not report these sleeping problems. Discussion: Our data suggest that different subgroups of PD patients exist, and clinical chemistry could be useful as a biomarker for these subgroups, which needs to be confirmed in a larger patient population. Further, our data raise the question regarding whether normalization of calcium levels could improve the sleep quality and somnolence in PD patients.

Long-Term Effects of Calcium-Based Liming Materials on Soil Fertility Sustainability and Rye Production as Soil Quality Indicators on a Typic Palexerult

Liming is a common practice used to improve acidic soil properties, as is essential for agricultural quality. A long-term field experiment with one lime rate (6000 kg/ha of carbonate calcium equivalent) and three calcium-based liming amendments (gypsum, limestone and sugar foam) was maintained on a Typic Palexerult for 10 years in order to determine changes in soil acidity and to assess the effects on crop (rye) yields. The soil acidity conditions decreased with all the amendments tested, but the sugar foam and limestone was more effective than gypsum over a long-term period. No significant changes in organic soil matter levels between the treatments tested were found. Interestingly, an increase in the leaching of organic soil matter was observed in limed soils. Lime application significantly increased the total rye biomass compared to the control soils during the whole experiment (2002–2011). Yield trends observed in spike and stem biomass were similar to those reported for total rye biomass. In this respect, at the end of the research, gypsum, limestone and sugar foam increased in relation to the total production of rye biomass by 16%, 32% and 38%, respectively, as compared to the control soils. Additionally, a significant and prolonged difference in calcium concentrations in rye stems between unlimed and limed subplots was observed. However, in spite of the results presented here, further investigations are needed to gain a better understanding of the long-term effects of liming on the chemical properties of soil.

Evaluation of anti-nutrient and mineral content in different pearl millet varieties

Pearl millet is one of the most popular crops in India. It is nutritionally comparable and even superior to major cereals with respect to protein, fat, energy, vitamins & minerals. The present investigation was carried out to evaluate the mineral content and the anti-nutrients present in pearl millet varieties i.e., white grain variety (ICMV-221), hybrids varieties (HHB-226, HHB-223 and HHB-197) and HC-20 variety. Calcium content was highest in HHB-226 and lowest in ICMV-221. No significant differences in calcium content of HHB-197 and HHB-223 was witnessed. Significant (P< 0.05) differences in iron content of different varieties of pearl millet were observed. ICMV-221 contained significantly (P< 0.05) higher zinc content than all the other varieties of pearl millet however, no significant difference in zinc content of HC-20 and HHB-223 as well as HHB-197 and HHB-226 were noticed. The phytic acid and polyphenol content of all pearl millet varieties varied from 620.00 to 875.00 and 304.17 to 438.33 mg/100g.

Seasonal variations in 25-hydroxy vitamin D3, parathormone and alkaline phosphatase in school-aged children

The main role of Vitamin D is to regulate calcium metabolism, whose main source is vitamin D3 ob tained mostly from the action of ultraviolet (UV) light on the skin. To evaluate the seaso nal differences in the concentrations of 25-hydroxy-vitamin D3 (25OHVitD3), parathyroid hormone (PTH), alkaline phosphatase (ALP), and calcium in school-age children. The concentrations of 25OHVitD3, PTH, ALP, and calcium were measured in children from Santiago, Chile (latitude -33.4372), aged 5 to 8 years, without Vitamin D supplementation, in different seasons of the year. VitD status was defined as sufficient with concentrations of 25OHVitD3 >20 ng/mL (50 nmol/L), insufficient 12-20 ng/mL (30-50 nmol/L) and deficient <12 ng/mL (30 nmol/L) based on the recommendations of the expert group of the "Global Consensus for the Prevention and Mana gement of Nutritional Rickets". 133 children participated (89 preterms under or equal to 32 weeks), 41 during summer, 28 in fall, 35 in winter, and 29 in spring. The difference of means between summer and winter was 9.6 ng/mL for 25OHVitD3 (p <0.0001), -11.1 pg/mL for PTH (p <0.0001), and -47.5 IU/mL for ALP (p= 0.01). There were no differences in calcium concentrations. In sum mer, 97.6% of the subjects were classified with sufficiency status (> 20 ng/mL), which decreased significantly in winter to 54.3% (p <0.0001). In winter, 25OHVitD3 concentrations decreased in approximately half of the children, which was associated with an increase in PTH and ALP, and normal calcium concentrations. According to our results, children may need VitD supple mentation during fall and winter.

Protective properties of Avène Thermal Spring Water on biomechanical, ultrastructural and clinical parameters of human skin.

Thermal Spring Water (TSW) has been recognized to have beneficial effects on skin; however, the mechanisms underlying these are not completely elucidated. We compared the effects of Avène TSW with mineral-rich (MR) TSW on the biomechanical properties of the skin using mechanistic exvivo assays and clinical studies. Ex vivo studies included the effect of both TSWs on the structure of the surface of human skin explants using scanning electron microscopy (SEM); mineral elemental content on the skin surface using SEM coupled to energy dispersing X-ray spectroscopy; and the stress properties of the stratum corneum (SC) when exposed to dehydration. Human clinical studies were conducted to compare the soothing effect of TSWs after a dermatological chemical peeling of face skin and to evaluate the overall sensitive scale of consumers using Avène TSW for 7days. Both TSWs preserved surface skin ultrastructure; however, crystals formed from MR-TSW were needle-like and formed small grains, present in clusters heterogeneously spread over the surface. Needle crystals were mainly composed of calcium, while small clusters were mainly composed of sulphur. By contrast, Avène TSW-formed crystals composed of sodium and chlorine only were regular in shape and homogeneously distributed across the skin surface. Peak stress of SC layers was increased by MR-TSW, whereas Avène TSW showed a comparatively reduced effect on dehydration and stress. The difference in the two TSW types was reflected in clinical findings comparing postpeeling redness after TSW application. Avène TSW significantly decreased postpeeling redness, while MR-TSW increased it. The overall sensitive scale of consumers was decreased by 47% using Avène TSW for 7days. Avène TSW decreases postpeeling redness and soothes sensitive skin in human volunteers. Mechanistic studies suggested that differences in biomechanical effects could be linked to differences in calcium content of the TSW.

Effect of Foliar Application of CaCl2 on Lettuce Growth and Calcium Concentrations with Organic and Conventional Fertilization

Calcium-rich vegetables in diet could minimize calcium deficiency and maximize good health and well-being. The aim of the present study was to determine the effect of different levels of foliar application of CaCl2 on lettuce (Lactuca sativa L.) growth and calcium concentrations with the application of organic and conventional fertilizers. Pot experiments were conducted with three calcium levels (60, 120, and 180 mg·L−1 of CaCl2) of an organic fertilizer (3N–0.8P–3.5K) and commercial conventional fertilizer (15N–15P–15K). Calcium in whole oven-ashed samples of shoots was analyzed by atomic absorption spectrometry. Nine lettuce cultivars including butterhead, romaine, and loose-leaf phenotype were tested. These results revealed that the calcium concentration in lettuce significantly increased as calcium levels increased from 60 to 180 mg·L−1. Elevated calcium concentrations in organic and conventional fertilizers increased the concentration of calcium in lettuce from 1.82% at 60 mg·L−1 to a mean of 2.15% at 120 and 180 mg·L−1. The concentration of calcium in the loose-leaf phenotype was 2.17%, 2.47%, and 3.80% higher than that in the butterhead and romaine phenotypes at 60, 120, and 180 mg Ca/L, respectively. Furthermore, the significant difference in calcium concentration among cultivars ranged from 1.27% to 3.05%. ‘Perilla Green’, ‘Breen lettuce’, and ‘Salinas’ had the highest calcium concentrations followed by ‘Jericho lettuce’, ‘Salad Bowl’ and ‘Crisp’, and ‘Kaiser’, whereas ‘Valmaine’ and ‘Rosa Green’ had the lowest calcium concentrations. The present study revealed that selecting fertilizers and cultivars with high calcium concentration can increase the total calcium content of lettuce.

The effect of essential oils on quality and mineral composition of eggshell

The effect of essential oils on quality and mineral composition of eggshell

Morphometrics and mineral composition of shell whorls in three species of giant African snails from Abeokuta, Nigeria

Archachatina marginata (Swainson), Achatina achatina (Linnaeus) and Achatina fulica Bowdich were examined for their shell whorl morphometrics (20 snails per species) and the calcium, iron and phosphorus content in the shell whorls (10 snails per species). The species differed in the degree of shell mineralization (the highest in the medium-sized A. achatina, intermediate in the smallest-sized A. fulica and the smallest in the largest-sized A. marginata) which was not ageor environment-dependent, since all the experimental snails were 12 months old adults of 6 whorls, originating from the same snail farm. In all three species the degree of shell mineralization decreased from the apical (oldest) to the body (youngest) whorl, thus depending entirely on the whorl’s age. The inter-specific differences in calcium content should be considered when using shells for medical or agricultural purposes.

Sustained presentation of BMP-2 enhances osteogenic differentiation of human adipose-derived stem cells in gelatin hydrogels.

Human adipose-derived stem cells (hASCs) show great potential for healing bone defects. Bone morphogenetic protein-2 (BMP-2) has been reported to stimulate their osteogenic differentiation both in vitro and in vivo. Here, methacrylated gelatin (GelMA) hydrogels were evaluated as a system to deliver BMP-2 to encapsulated hASCs from two different donors, and BMP-2 delivered from the hydrogels was compared to BMP-2 presented exogenously in culture media. GelMA hydrogels were shown to provide sustained, localized presentation of BMP-2 due to electrostatic interactions between the growth factor and biomaterial after an initial burst release. Both donors exhibited similar responses to the loaded and exogenous growth factor; BMP-2 from the hydrogels had a statistically significant effect on hASC osteogenic differentiation compared to exogenous BMP-2. Expression of alkaline phosphatase was accelerated, and cells in hydrogels with loaded BMP-2 deposited more calcium at one, two, and four weeks than cells without BMP-2 or with the growth factor presented in the media. There were no statistically significant differences in calcium content between groups with 25, 50, or 100 µg/mL loaded BMP-2, suggesting that using a lower growth factor dose may be as effective as a higher loading amount in this system. Taken together, these findings suggest that controlled delivery of BMP-2 from the GelMA enhances its osteogenic bioactivity compared to free growth factor presented in the media. Thus, the GelMA system is a promising biomaterial for BMP-2-mediated hASC osteogenesis. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1387-1397, 2016.

Enhancement of the rootability of a structurally fragile tropical soil using gypsum and leguminous residues to increase the yield of maize

AbstractIn humid tropical areas, a combination of factors related to soil conditions for root development contribute to decreased nutrient use efficiency. Our aim was to evaluate the combined effects of the application of gypsum and mulch from leguminous trees on rootability of root zone soil, root growth, phosphorus recovery efficiency and maize yield in a sandy loam soil prone to hardsetting. The experiment involved a randomized block design with four replications and six treatments: no residue or gypsum (control, C); leguminous residues (L); leguminous residues and 6 t/ha of gypsum (LG6); urea and 6 t/ha of gypsum (UG6); leguminous residues, urea and 6 t/ha of gypsum (LUG6); and leguminous residues, urea and 12 t/ha of gypsum (LUG12). Application of gypsum plus leguminous residues enhanced soil rootability, when applied to a tropical Arenic Hapludult, through the combined effects of increased porosity and decreased penetration resistance. These improvements facilitated root growth in deeper soil layers and greater nutrient uptake. Application of leguminous residues increased the input and retention of calcium in deeper layers. The use of large amounts of gypsum with leguminous residue, despite a significant increase in phosphorus uptake, did not result in a proportional increase in maize yield. Given the small differences in calcium content between the 6 and 12 t/ha gypsum treatments, applying a low dose of gypsum combined with leguminous residue, rather than administering a single large gypsum dose, is recommended for tropical sandy loam soils with low cation retention capacities.

Can dietary reliance on Pacific salmon eggs create otolith Sr/Ca signatures that mimic anadromy in resident salmonids?

Many aspects of the ecology, growth, life history, and population dynamics of fishes differ between anadromous populations and those residing exclusively in freshwater habitats. Analysis of the elemental composition of otoliths (ear stones) is commonly used to indicate the migration history of individuals, relying on the differences in ambient concentrations of calcium, strontium, and barium and their subsequent incorporation into calcified structures. Dietary contribution to otolith chemistry is often overlooked, but in this study we report results consistent with the possibility that reliance on food resources derived from the ocean via Pacific salmon can produce otolith Sr/Ca ratios suggesting anadromy in freshwater resident fish. Dolly Varden, Salvelinus malma, from the Iliamna River, Alaska feed very heavily on eggs and other tissues from sockeye salmon, Oncorhynchus nerka, and their otoliths had Sr/Ca ratios typical of fish making seasonal migrations to marine waters but the Ba/Ca ratios were consistent with residence in fresh water. Water samples from the river provided no indication that the elevated Sr concentrations came from the river. A simulation of otolith chemistry resulting from Sr incorporation from both water and diet across a range of published values in salmonids indicates that a diet of salmon eggs and tissues can produce marine Sr/Ca ratios while fish remain in fresh water. Without experimental evidence such as a controlled diet study these results are suggestive but not conclusive. Nevertheless, they send a cautionary note that in some cases heavy reliance on marine-derived food sources might affect otolith microchemistry, creating an appearance of anadromy in fish that did not leave fresh water.

Evaluation of vitamin D concentration in a population of young, healthy women - the effects of vitamin D supplementation.

The goal of the study was an evaluation of serum vitamin D concentrations in healthy young women. A total of 106 healthy women, aged 20-30 years, were included in the study. Monthly evaluation - for three months - of the effects of calcium (500 mg) and vitamin D (1500 IU) administration in women with baseline values of vitamin D < 20 ng/mL (Group 1) plus the effects of an 800 IU/d dose in women with the baseline value of D > 20 ng/mL (Group 2). Additionally, calcium and PTH concentrations were assessed at the study onset and after a three-month supplementation. Only 67 women adhered to the prescribed therapeutic regime during the three months of observation. The mean vitamin D concentration in the entire study group was 16.56 ng/mL, being 12.6 ng/mL in Group 1 and 25.22 ng/mL in Group 2. In the course of vitamin D administration, its concentration increased statistically significantly, both in the entire group and in the subgroups, at all time points compared with the study onset. Moreover, its concentration in the whole population and in Group 1 was significantly higher in each of the time points not only in relation to the baseline, but also in comparison with the results of the previous measurements (after 1 and 2 months of supplementation). In Group 2, vitamin D levels also increased systematically throughout the whole study period, and after 3 months its concentration was significantly higher than after 1 and 2 months. Although there were no differences in calcium concentration after those three months, a statistically significant drop of PTH (p < 0.05) was recorded in the entire population and in Group 1. A moderate deficiency of vitamin D was observed in the studied population of young women. A supplementation with calcium plus vitamin D brought about an increase of vitamin D concentration as early as in the first month of administration. The optimal concentration of > 30 ng/mL was achieved in Group 1 after three months of vitamin D administration in 1500 IU/d dose.

Organ-dependent differences in calcium content in mice exposed to cadmium: A time correlation study

Organ-dependent differences in calcium content in mice exposed to cadmium: A time correlation study

Acute toxicity of copper, lead, cadmium, and zinc to early life stages of white sturgeon (Acipenser transmontanus) in laboratory and Columbia River water.

Populations of white sturgeon (Acipenser transmontanus) are in decline in North America. This is attributed, primarily, to poor recruitment, and white sturgeon are listed as threatened or endangered in several parts of British Columbia, Canada, and the United States. In the Columbia River, effects of metals have been hypothesized as possible contributing factors. Previous work has demonstrated that early life stage white sturgeon are particularly sensitive to certain metals, and concerns over the level of protectiveness of water quality standards are justified. Here we report results from acute (96-h) toxicity tests for copper (Cu), cadmium (Cd), zinc (Zn), and lead (Pb) from parallel studies that were conducted in laboratory water and in the field with Columbia River water. Water effect ratios (WERs) and sensitivity parameters (i.e., median lethal accumulations, or LA50s) were calculated to assess relative bioavailability of these metals in Columbia River water compared to laboratory water, and to elucidate possible differences in sensitivity of early life stage white sturgeon to the same concentrations of metals when tested in the different water sources. For Cu and Pb, white sturgeon toxicity tests were initiated at two life stages, 8 and 40 days post-hatch (dph), and median lethal concentrations (LC50s) ranged between 9-25 μg Cu/L and 177-1,556 μg Pb/L. LC50s for 8 dph white sturgeon exposed to Cd in laboratory water and river water were 14.5 and 72 μg/L, respectively. Exposure of 8 dph white sturgeon to Zn in laboratory and river water resulted in LC50s of 150 and 625 μg/L, respectively. Threshold concentrations were consistently less in laboratory water compared with river water, and as a result, WERs were greater than 1 in all cases. In addition, LA50s were consistently greater in river water exposures compared with laboratory exposures in all paired tests. These results, in combination with results from the biotic ligand model, suggest that the observed differences in toxicity between river water exposures and laboratory water exposures were not entirely due to differences in water quality and metal bioavailability but rather in combination with differences in fish sensitivity. It is hypothesized that differences in concentrations of calcium in the different water sources might have resulted in differences in acquired sensitivity of sturgeon to metals. Canadian water quality guidelines, US national criteria for the protection of aquatic life, and water quality criteria for the state of Washington were less than LC50 values for all metals and life stages tested in laboratory and Columbia River water. With the exception, however, that 40 dph white sturgeon exposed to Cu in laboratory water resulted in threshold values that bordered US national criteria and criteria for the state of Washington.

Calcium concentration in leaf litter affects the abundance and survival of crustaceans in streams draining warm–temperate forests

Summary Stream ecosystems receive large quantities of nutrients from terrestrial ecosystems that influence community dynamics. However, few studies have investigated the effects of subsidiary calcium, an essential element of animals, on stream ecosystems. We focused on differences in calcium concentrations of leaf litter between tree species. In particular, litter of Japanese cedar (Cryptomeria japonica) has a higher concentration of calcium than other taxa, and the tree is planted in many parts of Japan. Therefore, we predicted that a C. japonica plantation would affect the supply of subsidiary calcium to stream ecosystems. We compared calcium concentration of leaf litters, soils, stream water and stream benthic invertebrates sampled at nine sites in catchments composed of cedar plantations, evergreen broad‐leaved forest and clear‐cut areas. In addition, we placed 10 Gammarus nipponensis in each of 10 nylon cages in the nine streams and after one month surveyed the number of surviving individuals. Calcium concentration in stream water and soil, and the density and survival of the dominant crustacean (Gammarus nipponensis) were significantly higher at sites dominated by C. japonica compared with other forest types. Furthermore, invertebrate community composition was correlated with total calcium and nitrate in stream water, indicating that terrestrial vegetation can affect stream invertebrate communities, particularly crustaceans.