Bioavailable iron concentrations regulate phytoplankton growth and bloom formation in low-nutrient lakes.

The growth of phytoplankton in lakes is thought to be primarily controlled by macronutrient concentrations, but the availability of trace metal micronutrients, such as iron (Fe), are increasingly recognised as important regulators of lake primary production. This study evaluates the role of Fe in regulating phytoplankton growth in lakes of different nutrient status in New Zealand. The results of this unique year-long study, combining highly sensitive trace metal concentration analysis of waters and particulates with advanced trace metal bioavailability and speciation modelling, constrains thresholds for bioavailable Fe and colloidal Fe of 0.8 nmol·L-1 and 30 nmol·L-1, respectively, below which phytoplankton growth-limitation occurs. These thresholds specifically control diatom bloom formation and termination in lakes, thereby exerting a strong influence on freshwater carbon sequestration, given the dominance of diatoms in lake bloom assemblages. Importantly, potentially toxic cyanobacteria thrived only after events of bottom water anoxia, when additional dissolved Fe in concentrations ≥4 nmol·L-1 was released into the water column. These new thresholds for bioavailable and colloidal Fe offer the potential to manage micronutrient levels in lakes for the purpose of regulating algal bloom formation and carbon sequestration, while at the same time, suppressing the formation of harmful cyanobacterial blooms.

Growth at the limits: comparing trace metal limitation of a freshwater cyanobacterium (Dolichospermum lemmermannii) and a freshwater diatom (Fragilaria crotonensis).

Freshwater phytoplankton blooms are increasing in prevalence and there are conflicting views on whether trace metals limit growth of key species and thus bloom formation. The Taupo Volcanic Zone (TVZ), New Zealand, was formed by multiple eruptions of a super-volcano which emitted rhyolitic tephra leaving lakes depleted in trace metals. This provides an opportunity to test the potential of trace metal limitation on freshwater phytoplankton growth under nanomolar concentrations. Growth responses of two algal species isolated from Lake Taupo, Dolichospermum lemmermannii (cyanobacteria) and Fragilaria crotonensis (diatom), to six biologically important trace metals (manganese, iron, zinc, cobalt, copper and molybdenum) were examined in culture experiments. These were conducted at three trace metal concentrations: (1) ambient, (2) two-times ambient, and (3) ten-times ambient concentrations in Lake Taupo. Elevated concentrations of iron significantly increased growth rates and maximum cell densities in D. lemmermannii, whereas no significant concentration dependence was observed for other trace metals. Fragilaria crotonensis showed no significant growth response to elevated concentrations of trace metals. These results highlight the importance of iron as a growth limiting nutrient for cyanobacteria and indicate that even small (twofold) increases in Fe concentrations could enhance cyanobacteria growth rates in Lake Taupo, potentially causing cyanobacterial blooms.

Multiple Micronutrients, Including Zinc, Selenium and Iron, Are Positively Associated with Anemia in New Zealand Aged Care Residents.

Anemia is a significant comorbidity for older adults not fully attributable to iron deficiency. Low-grade inflammation and other micronutrient deficiencies also contribute. This cross-sectional study examined the relationships between nutrient and non-nutrient factors with hemoglobin and anemia in 285 residents (>65 years) of 16 New Zealand aged-care facilities. Blood samples were analyzed for hemoglobin, ferritin, sTfR, hepcidin, zinc, selenium, and interleukin-6 (IL-6), (with ferritin, sTfR, zinc and selenium adjusted for inflammation). Linear regression models examined the relationships between micronutrient biomarkers (iron, zinc, selenium, vitamin B-12 and D), age, sex, and health factors with hemoglobin. Thirty-two percent of participants exhibited anemia, although <2% had either depleted iron stores or iron deficiency. Plasma zinc and selenium deficiencies were present in 72% and 38% of participants, respectively. Plasma zinc and total body iron (TBI) were positively associated (p < 0.05) with hemoglobin, while gastric acid suppressing medications, hepcidin, and interleukin-6 were inversely associated. These relationships were maintained after the application of anemia cut-offs. These findings emphasize the importance of considering multiple micronutrient deficiencies as risk factors for anemia.

A comparison of methods for adjusting biomarkers of iron, zinc, and selenium status for the effect of inflammation in an older population: a case for interleukin 6.

Background: Older people are at risk of micronutrient deficiencies, which can be under- or overestimated in the presence of inflammation. Several methods have been proposed to adjust for the effect of inflammation; however, to our knowledge, none have been investigated in older adults in whom chronic inflammation is common. Objective: We investigated the influence of various inflammation-adjustment methods on micronutrient biomarkers associated with anemia in older people living in aged-care facilities in New Zealand. Design: Blood samples were collected from 289 New Zealand aged-care residents aged >65 y. Serum ferritin, soluble transferrin receptor (sTfR), total body iron (TBI), plasma zinc, and selenium as well as the inflammatory markers high-sensitivity C-reactive protein (CRP), α1-acid glycoprotein (AGP), and interleukin 6 (IL-6) were measured. Four adjustment methods were applied to micronutrient concentrations: 1) internal correction factors based on stages of inflammation defined by CRP and AGP, 2) external correction factors derived from the literature, 3) a regression correction model in which reference CRP and AGP were set to the maximum of the lowest decile, and 4) a regression correction model in which reference IL-6 was set to the maximum of the lowest decile. Results: Forty percent of participants had elevated concentrations of CRP, AGP, or both, and 37% of participants had higher than normal concentrations of IL-6. Adjusted geometric mean values for serum ferritin, sTfR, and TBI were significantly lower (P < 0.001), and plasma zinc and selenium were significantly higher (P < 0.001), than the unadjusted values regardless of the method applied. The greatest inflammation adjustment was observed with the regression correction that used IL-6. Subsequently, the prevalence of zinc and selenium deficiency decreased (-13% and -14%, respectively; P < 0.001), whereas iron deficiency remained unaffected. Conclusions: Adjustment for inflammation should be considered when evaluating micronutrient status in this aging population group; however, the approaches used require further investigation, particularly the influence of adjustment for IL-6.

Implications of Wear at the Titanium-Zirconia Implant-Abutment Interface on the Health of Peri-implant Tissues.

PURPOSE: To investigate the presence of metallic particles in the peri-implant mucosa around titanium dental implants after 5 years of loading using single-implant crowns with respect to clinical signs of peri-implant inflammation. MATERIALS AND METHODS: Sixteen participants from an ongoing, prospective, single-arm clinical trial who had received titanium dental implants restored with single maxillary crowns veneered to zirconia abutments were available for the study. Exfoliative cytology samples were obtained from the peri-implant tissues and contralateral tooth sites using microbrushes and were evaluated by means of light microscopy (LM), scanning electron microscopy, and energy-dispersive spectroscopy (EDS). Trace elemental analysis was also carried out on the microbrushes using inductively coupled plasma mass spectrometry. Peri-implant and periodontal parameters (plaque, bleeding, attachment level, radiographic bone levels) were recorded. RESULTS: Titanium particles were found in both the single-implant crown and contralateral natural tooth sites. LM and EDS analyses showed significantly higher numbers of Ti particles at the implant-abutment interfaces (mean = 14.168; SD = 2.36) and in the internal aspects of peri-implant mucosa in contact with the prostheses (mean = 4.438; SD = 2.22) when compared with other test and control areas. Mean probing depths were ≤ 3 mm, and no differences were found in plaque or bleeding on probing between implant and tooth sites. Median bone levels were within the normal range for both implant (mesial: 0.5 mm; distal: 0.8 mm) and tooth (mesial: 1.5 mm; distal: 1.8 mm) sites. CONCLUSION: Loading of single-implant zirconia crowns can cause the release of Ti particles because of functional wear at the implant-abutment level. The presence of these metal particles in the peri-implant area did not appear to affect peri-implant health in this patient group.

Predictors of pesticide concentrations in freshwater trout - The role of life history.

Concentrations of halogenated pesticides in freshwater fish can be affected by age, size, trophic position, and exposure history. Exposure history may vary for individual fish caught at a single location due to different life histories, e.g. they may have hatched in different tributaries before migrating to a specific lake. We evaluated correlations of pesticide concentrations in freshwater brown trout (Salmo trutta) from the Clutha River, New Zealand, with potential predictors including capture site, age, length, trophic level, and life history. Life history was determined from otolith (fish ear bone) strontium isotope signatures, which vary among tributaries in the region of our study. Variability in pesticide concentrations between individual fish was not well explained by capture site, age, length, or trophic level. However, hexachlorobenzene (HCB) and chlorpyrifos concentrations were distinct in lake-based trout with different life histories. Additionally, one of the riverine life histories was associated with relatively high concentrations of total endosulfans. Linear models that included all potential predictor variables were evaluated and the resulting best models for HCB, chlorpyrifos, and total endosulfans included life history. These findings show that in cases where otolith isotope signatures vary geographically, they can be used to help explain contaminant concentration variations in fish caught from a single location.

Iodine Status of New Zealand Elderly Residents in Long-Term Residential Care.

In response to the re-emergence of iodine deficiency in New Zealand, in 2009 the government mandated that all commercially made breads be fortified with iodized salt. There has been no evaluation of the impact of the program on iodine status of the elderly, despite this population group being vulnerable to iodine deficiency or excess. The aim of this study was to describe the iodine status of elderly New Zealanders in residential aged-care homes following the implementation of the bread fortification program. A cross-sectional survey was conducted, involving 309 residents (median age 85 years) from 16 aged-care homes throughout NZ. Information on socio-demographic, anthropometric, dietary and health characteristics were collected. Casual spot urine samples were analysed for urinary iodine concentration (UIC). Blood samples were analysed for serum thyroglobulin, thyroglobulin antibodies, and other biochemical indices. The median UIC (MUIC) of the residents was 72 µg/L, indicating mild iodine deficiency, and 29% had a UIC < 50 µg/L. Median thyroglobulin concentration was 18 ng/mL and 26% had elevated thyroglobulin concentration (>40 ng/mL), suggesting iodine insufficiency. Diuretic use was associated with lower MUIC (p = 0.043). Synthetic thyroxine use was associated with lower odds of having a UIC < 50 µg/L (OR 0.32, p = 0.030)) and lower median thyroglobulin (-15.2 ng/mL, p = 0.001), compared with untreated participants. Frailty was associated with elevated thyroglobulin (p = 0.029), whereas anemia was associated with lower thyroglobulin (p = 0.016). Iodine insufficiency persists in New Zealanders residing in residential aged-care homes despite increasing iodine intake from fortified bread. Research is required to establish optimal iodine intake and status in the elderly.

Otolith Trace Elemental Analyses of South American Austral Hake, Merluccius australis (Hutton, 1872) Indicates Complex Salinity Structuring on their Spawning/Larval Grounds.

Trace element signatures of otolith edges and cores from 335 austral hake (Merluccius autralis) were analysed using LA-ICPMS from samples collected in Chilean and Falkland Islands' waters, in order to provide potential insights into stock discrimination and migrations. Fish were caught in two locations in Chile and four locations in the south-west of the Falkland Islands Shelf. Univariate and multivariate analyses of trace element signatures in the edges of otoliths, representing adult fish, were not able to distinguish between samples collected in Chile and the Falkland Islands. Cluster analyses based on Ward's similarity/distance metric suggested that it was possible to identify two groups from core signatures. Further analyses of this perceived clustering of the core concentrations revealed that this was largely due to the wide spread of Sr/Ca ratios in the otoliths' cores. Gaussian finite mixtures using MCMC methods confirmed that Sr/Ca ratios form two separate distributions with significantly different mean values while concentrations of other elements showed no evidence of the presence of two or more distributions. The results suggest that there is only one spawning stock of austral hake with spawning situated in and around the Chilean fjords (43°30'S- 47°S) and the variation in Sr/Ca ratios likely suggests complex salinity structuring in this area.

Comparison of digestion methods for ICP-MS determination of trace elements in fish tissues.

A comparison is presented of six methods involving nitric acid in conjunction with other reagents to digest three certified marine biological samples (DOLT-3, DORM-3, IAEA-407) and a fish bone homogenate (prepared from Merluccius australis). An inductively coupled plasma-mass spectrometer with an octopole collision cell was used to determine up to 40 elements (Li, B, Na, Mg, Al, K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Rb, Sr, Y, Ag, Cd, Cs, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu, Pb, Th, U) in the digests. These results were assessed in terms of their accuracy and precision, and a flow chart was developed to aid the selection of the optimal digestion method. Although none of the methods was found to give accurate determinations for all elements in the different reference materials, a relatively simple method involving nitric acid and hydrogen peroxide heated in a domestic microwave oven gave the most acceptable results.