8 research outputs found
Bioaccumulation Dynamics of Arsenate at the Base of Aquatic Food Webs
Periphyton
is an important food source at the base of freshwater
ecosystems that tends to bioconcentrate trace elements making them
trophically available. The potential for arsenic–a trace element
of particular concern due to its widespread occurrence, toxicity,
and carcinogenicity–to bioconcentrate in periphyton and thus
be available to benthic grazers is less well characterized. To better
understand arsenate bioaccumulation dynamics in lotic food webs, we
used a radiotracer approach to characterize accumulation in periphyton
and subsequent trophic transfer to benthic grazers. Periphyton bioconcentrated
As between 3,200–9,700-fold (dry weight) over 8 days without
reaching steady state, suggesting that periphyton is a major sink
for arsenate. However, As-enriched periphyton as a food source for
the mayfly <i>Neocloeon triangulifer</i> resulted in negligible
As accumulation in a full lifecycle exposure. Additional studies estimate
dietary assimilation efficiency in several primary consumers ranging
from 22% in the mayfly <i>N. triangulifer</i> to 75% in
the mayfly <i>Isonychia sp.</i> X-ray fluorescence mapping
revealed that As was predominantly associated with iron oxides in
periphyton. We speculate that As adsorption to Fe in periphyton may
play a role in reducing dietary bioavailability. Together, these results
suggest that trophic movement of As in lotic food webs is relatively
low, though species differences in bioaccumulation patterns are important
Bioconcentration and Biotransformation of Selenite versus Selenate Exposed Periphyton and Subsequent Toxicity to the Mayfly Centroptilum triangulifer
Little is known about
the bioaccumulation dynamics, biotransformation
processes, or subsequent toxicity to consumers of dissolved selenite
(SeO<sub>3</sub>) versus selenate (SeO<sub>4</sub>) uptake into aquatic
primary producer communities. To address these data gaps, we examined
SeO<sub>3</sub> and SeO<sub>4</sub> bioconcentration into complex
freshwater periphyton communities under static and static-renewal
conditions. Further, we explored periphyton biotransformation of Se
species using X-ray absorption near edge structure (XANES) spectroscopy
analysis and changes in the periphyton associated microbial consortium
using denaturing gradient gel electrophoresis (DGGE). Last, we fed
differentially treated periphyton to the mayfly Centroptilum
triangulifer in full life cycle exposures to assess
toxicity. Selenite exposed periphyton readily bioconcentrated Se while,
in contrast, initial periphyton uptake of SeO<sub>4</sub> was negligible,
but over time periphyton [Se] increased steadily in conjunction with
the formation of dissolved SeO<sub>3</sub>. XANES analyses revealed
that both SeO<sub>3</sub> and SeO<sub>4</sub> treated periphyton biotransformed
Se similarly with speciation dominated by organo-selenide (∼61%).
Mayfly survival, secondary production, and time to emergence were
similar in both SeO<sub>3</sub> and SeO<sub>4</sub> treated periphyton
exposures with significant adverse effects at 12.8 μg g<sup>–1</sup> ((d.w.) secondary production) and 36 μg g<sup>–1</sup> ((d.w.) survival and development time). Overall,
dissolved selenium speciation, residence time, and organisms at the
base of aquatic food webs appear to be the principal determinants
of Se bioaccumulation and toxicity
DataSheet3.CSV
<p>Temperature dictates the performance of aquatic ectotherms. However, the physiological and biochemical processes that drive thermally-mediated life history patterns (and limits) remain poorly understood because they are rarely studied simultaneously. In our previous work, we have established life history outcomes (e.g., survivorship, development time, growth rates, and fitness) in mayflies (Neocloeon triangulifer) reared at static temperatures ranging from 14 to 30°C at 2°C intervals. In this study, we conducted biochemical measurements (RT-qPCR of select genes and targeted, quantitative metabolomic profiling) on N. triangulifer mature larvae reared at temperatures associated with excellent survival and fitness (22–24°C), compromised survival and fitness (28°C), and chronic lethality (30°C—larvae survived for a few weeks but failed to emerge to adulthood). Patterns of gene expression were similar to those observed in acute ramping experiments reported previously: larvae reared at 30°C resulted in significant upregulation in the thermally responsive gene HEAT SHOCK PROTEIN 90 (HSP90) but no significant changes in hypoxia responsive genes [EGGLAYING DEFECTIVE9 (EGL-9) and LACTATE DEHYDROGENASE (LDH)]. Additionally, primers for genes associated with energy: INSULIN RECEPTOR (IR), mechanistic TARGET OF RAPAMYCIN (mTOR), and TREHALOSE 6 PHOSPHATE SYNTHASE (T6PS) were developed for this study. IR and mTOR were significantly upregulated while T6PS showed trend of downregulation in larvae reared at 30°C. Metabolomic profiles revealed general depletion of lipids and acylcarnitines in larvae exposed to chronic thermal stress, suggesting that larvae were energetically challenged despite continuous access to food. For example, concentrations of lysoPhosphatidylcholine (lysoPC) a C20:3 decreased as fitness decreased with increasing temperature (2.3- and 2.4-fold at 28 and 30°C relative to controls). Tissue concentrations of the biogenic amine histamine increased 2.1- and 3.1-fold with increasing temperature, and were strongly and negatively correlated with performance. Thus, both histamine and lysoPC a C20:3 are potential biomarkers of thermal stress. Taken together, our results primarily associate energetic challenge with thermally mediated fitness reduction in N. triangulifer.</p
DataSheet2.xlsx
<p>Temperature dictates the performance of aquatic ectotherms. However, the physiological and biochemical processes that drive thermally-mediated life history patterns (and limits) remain poorly understood because they are rarely studied simultaneously. In our previous work, we have established life history outcomes (e.g., survivorship, development time, growth rates, and fitness) in mayflies (Neocloeon triangulifer) reared at static temperatures ranging from 14 to 30°C at 2°C intervals. In this study, we conducted biochemical measurements (RT-qPCR of select genes and targeted, quantitative metabolomic profiling) on N. triangulifer mature larvae reared at temperatures associated with excellent survival and fitness (22–24°C), compromised survival and fitness (28°C), and chronic lethality (30°C—larvae survived for a few weeks but failed to emerge to adulthood). Patterns of gene expression were similar to those observed in acute ramping experiments reported previously: larvae reared at 30°C resulted in significant upregulation in the thermally responsive gene HEAT SHOCK PROTEIN 90 (HSP90) but no significant changes in hypoxia responsive genes [EGGLAYING DEFECTIVE9 (EGL-9) and LACTATE DEHYDROGENASE (LDH)]. Additionally, primers for genes associated with energy: INSULIN RECEPTOR (IR), mechanistic TARGET OF RAPAMYCIN (mTOR), and TREHALOSE 6 PHOSPHATE SYNTHASE (T6PS) were developed for this study. IR and mTOR were significantly upregulated while T6PS showed trend of downregulation in larvae reared at 30°C. Metabolomic profiles revealed general depletion of lipids and acylcarnitines in larvae exposed to chronic thermal stress, suggesting that larvae were energetically challenged despite continuous access to food. For example, concentrations of lysoPhosphatidylcholine (lysoPC) a C20:3 decreased as fitness decreased with increasing temperature (2.3- and 2.4-fold at 28 and 30°C relative to controls). Tissue concentrations of the biogenic amine histamine increased 2.1- and 3.1-fold with increasing temperature, and were strongly and negatively correlated with performance. Thus, both histamine and lysoPC a C20:3 are potential biomarkers of thermal stress. Taken together, our results primarily associate energetic challenge with thermally mediated fitness reduction in N. triangulifer.</p
DataSheet1.xlsx
<p>Temperature dictates the performance of aquatic ectotherms. However, the physiological and biochemical processes that drive thermally-mediated life history patterns (and limits) remain poorly understood because they are rarely studied simultaneously. In our previous work, we have established life history outcomes (e.g., survivorship, development time, growth rates, and fitness) in mayflies (Neocloeon triangulifer) reared at static temperatures ranging from 14 to 30°C at 2°C intervals. In this study, we conducted biochemical measurements (RT-qPCR of select genes and targeted, quantitative metabolomic profiling) on N. triangulifer mature larvae reared at temperatures associated with excellent survival and fitness (22–24°C), compromised survival and fitness (28°C), and chronic lethality (30°C—larvae survived for a few weeks but failed to emerge to adulthood). Patterns of gene expression were similar to those observed in acute ramping experiments reported previously: larvae reared at 30°C resulted in significant upregulation in the thermally responsive gene HEAT SHOCK PROTEIN 90 (HSP90) but no significant changes in hypoxia responsive genes [EGGLAYING DEFECTIVE9 (EGL-9) and LACTATE DEHYDROGENASE (LDH)]. Additionally, primers for genes associated with energy: INSULIN RECEPTOR (IR), mechanistic TARGET OF RAPAMYCIN (mTOR), and TREHALOSE 6 PHOSPHATE SYNTHASE (T6PS) were developed for this study. IR and mTOR were significantly upregulated while T6PS showed trend of downregulation in larvae reared at 30°C. Metabolomic profiles revealed general depletion of lipids and acylcarnitines in larvae exposed to chronic thermal stress, suggesting that larvae were energetically challenged despite continuous access to food. For example, concentrations of lysoPhosphatidylcholine (lysoPC) a C20:3 decreased as fitness decreased with increasing temperature (2.3- and 2.4-fold at 28 and 30°C relative to controls). Tissue concentrations of the biogenic amine histamine increased 2.1- and 3.1-fold with increasing temperature, and were strongly and negatively correlated with performance. Thus, both histamine and lysoPC a C20:3 are potential biomarkers of thermal stress. Taken together, our results primarily associate energetic challenge with thermally mediated fitness reduction in N. triangulifer.</p
Diagnostic nucleotides in <i>Siphlonurus rapidus</i>, <i>S. typicus</i>, and <i>S</i>. sp.JMW1.
<p>Diagnostic nucleotides in <i>Siphlonurus rapidus</i>, <i>S. typicus</i>, and <i>S</i>. sp.JMW1.</p
Distribution map for all barcoded specimens of Ephemeroptera with geocoordinates (n = 3902).
<p>Distribution map for all barcoded specimens of Ephemeroptera with geocoordinates (n = 3902).</p
Summary of current barcode coverage and divergence values for the 21 families of Ephemeroptera known from North America (NA).
<p>All distances are % K2P; MNID = minimum interspecific K2P distance, MXID = maximum intraspecific K2P distance.</p