The Lake Erie HABs Grab: A binational collaboration to characterize the western basin cyanobacterial harmful algal blooms at an unprecedented high-resolution spatial scale

Monitoring of cyanobacterial bloom biomass in large lakes at high resolution is made possible by remote sensing. However, monitoring cyanobacterial toxins is only feasible with grab samples, which, with only sporadic sampling, results in uncertainties in the spatial distribution of toxins. To address this issue, we conducted two intensive "HABs Grabs" of microcystin (MC)-producing Microcystis blooms in the western basin of Lake Erie. These were one-day sampling events during August of 2018 and 2019 in which 100 and 172 grab samples were collected, respectively, within a six-hour window covering up to 2,270 km² and analyzed using consistent methods to estimate the total mass of MC. The samples were analyzed for 57 parameters, including toxins, nutrients, chlorophyll, and genomics. There were an estimated 11,513 kg and 30,691 kg of MCs in the western basin during the 2018 and 2019 HABs Grabs, respectively. The bloom boundary poses substantial issues for spatial assessments because MC concentration varied by nearly two orders of magnitude over very short distances. The MC to chlorophyll ratio (MC:chl) varied by a factor up to 5.3 throughout the basin, which creates challenges for using MC:chl to predict MC concentrations. Many of the biomass metrics strongly correlated (r > 0.70) with each other except chlorophyll fluorescence and phycocyanin concentration. While MC and chlorophyll correlated well with total phosphorus and nitrogen concentrations, MC:chl correlated with dissolved inorganic nitrogen. More frequent MC data collection can overcome these issues, and models need to account for the MC:chl spatial heterogeneity when forecasting MCs.

Physical drivers facilitating a toxigenic cyanobacterial bloom in a major Great Lakes tributary

The Maumee River is the primary source for nutrients fueling seasonal Microcystis-dominated blooms in western Lake Erie's open waters though such blooms in the river are infrequent. The river also serves as source water for multiple public water systems and a large food services facility in northwest Ohio, USA. On 20 September 2017, an unprecedented bloom was reported in the Maumee River estuary within the Toledo metropolitan area, which triggered a recreational water advisory. Here we (1) explore physical drivers likely contributing to the bloom's occurrence, and (2) describe the toxin concentration and bacterioplankton taxonomic composition. A historical analysis using ten-years of seasonal river discharge, water level, and local wind data identified two instances when high-retention conditions occurred over ≥10 days in the Maumee River estuary: in 2016 and during the 2017 bloom. Observation by remote sensing imagery supported the advection of cyanobacterial cells into the estuary from the lake during 2017 and the lack of an estuary bloom in 2016 due to a weak cyanobacterial bloom in the lake. A rapid-response survey during the 2017 bloom determined levels of the cyanotoxins, specifically microcystins, in excess of recreational contact limits at sites within the lower 20 km of the river while amplicon sequencing found these sites were dominated by Microcystis. These results highlight the need to broaden our understanding of physical drivers of cyanobacterial blooms within the interface between riverine and lacustrine systems, particularly as such blooms are expected to become more prominent in response to a changing climate.

Updating the ELISA standard curve fitting process to reduce uncertainty in estimated microcystin concentrations

This study is aimed at exploring the optimal ELISA standard curve fitting process for reducing measurement uncertainty. Using an ELISA kit for measuring cyanobacterial toxin (microcystin), we show that uncertainty associated with the estimated microcystin concentrations can be reduced by defining the standard curve as a four-parameter logistic function on the natural log concentration scale, instead of the current approach of defining the curve on the concentration scale. The model comparison method is outlined in this paper, allowing it to be transferable to test different statistical models for other ELISA test kits.

Effect of magnesium hydroxide administration on iron absorption after a supratherapeutic dose of ferrous sulfate in human volunteers: a randomized controlled trial

STUDY OBJECTIVE

Animal models have demonstrated that administration of magnesium hydroxide (MgOH) decreases serum iron levels after an iron overdose. We designed this study to determine the effect of MgOH administration on iron absorption and adverse effects after a supratherapeutic dose of ferrous sulfate in healthy male volunteers.

METHODS

We conducted a prospective, unblinded, randomized trial involving 16 healthy, fasting men. All subjects ingested a 10-mg/kg dose of elemental iron in the form of ferrous sulfate. One-half hour after the iron dose, the 8 subjects in the experimental group were given 5 mg of MgOH for every 1 mg of ingested elemental iron. Serum iron levels were obtained at baseline and at each subsequent hour for 6 or 7 hours. Serum magnesium levels were obtained at baseline, after 3 hours, and after 6 hours. Side effects were recorded hourly. Serum iron levels between groups were compared by repeated-measures ANOVA and ANCOVA. The 95% confidence intervals (CIs) for the difference in serum iron levels between groups at each time point and for the difference in peak serum iron level between groups were calculated.

RESULTS

Baseline mean serum iron levels did not differ between the 2 groups (P =.28). There were no statistical differences between groups (P =.20). Mean serum iron levels at each time point and peak serum iron levels did not differ significantly between groups. The mean peak serum iron level was 300.8 micrograms/dL in the control group and 272.5 micrograms/dL in the experimental group.

CONCLUSION

Administration of MgOH does not affect iron absorption in humans after a supratherapeutic dose of iron when the ratio of MgOH to elemental iron is 5:1.

Stress and psychosocial factors: effects on primary cellular immune response

Life stress is associated with decreases in some immune functions, but little is known about the effect of stress on immune response to active immunization. We examined the relationships between stressful events, psychosocial, and biologic factors and primary immune response to a novel antigen-keyhold limpet hemocyanin (KLH). Lymphocyte proliferation (LP) was measured prior to immunization and 3 and 8 weeks following KLH immunization. At 3 weeks, LP was significantly lower in subjects reporting more "bad" stress and those experiencing more psychological distress, while "good" stress and social support tended to be associated with higher LP. There was a trend toward the more stressed subjects having lower baseline, but higher 8-week, LP responses. The model that best fits these data suggests that psychosocial processes mediate the relationship between stressful events and primary immune response, while biologic factors, such as recent weight gain, show direct independent effects on immune response.

Effect of stress and other biopsychosocial factors on primary antibody response

There is growing evidence that life stress is associated with altered cellular immune function, but only a few studies have examined the effect of stress on humoral immune response. We immunized 89 healthy women (18-24 years) with a novel antigen, keyhole limpet hemocyanin (KLH), to study the impact of stressful events and psychosocial and biologic factors on primary antibody response to immunization. Antibodies to KLH were measured preimmunization and 3 and 8 weeks after immunization. Previously validated scales were used to measure (1) recent major stress (both "good" and "bad," as defined by the subjects) and minor stressful events, and (2) psychological status and social support. Subjects were also asked about personal medical history, sociodemographics, and side effects of immunization. Subjects with more stressful events (of any type) tended to have lower baseline and 3-week postimmunization IgG levels. Those reporting more "good" events tended to have higher IgG levels at 8 weeks postimmunization. Psychological Distress scores correlated negatively and Psychological Wellbeing scores correlated positively with each IgG level. Subjects with a recent infection (preimmunization) or a local reaction to immunization had significantly higher IgG levels at all three points compared to those without these factors. These data and exploratory analysis suggest that recent stress and psychological status (perhaps representing the cumulative effects of stress and response to stress) may influence immune response to immunization. However, predisposing biological factors must also be assessed for possible confounding in the stress-immune response relationship.