The effect of dissolved organic matter (DOM) on sodium transport and nitrogenous waste excretion of the freshwater cladoceran (Daphnia magna) at circumneutral and low pH

Hassan A. Al-Reasi, Usman Yusuf, D. Scott Smith, Chris M. Wood

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

Dissolved organic matter (DOM), a heterogeneous substance found in all natural waters, has many documented abiotic roles, but recently, several possible direct influences of DOM on organism physiology have been reported. However, most studies have been carried out with a limited number of natural DOM isolates or were restricted to the use of commercial or artificial humic substances. We therefore employed three previously characterized, chemically-distinct natural DOMs, as well as a commercially available humic acid (Aldrich, AHA), at circumneutral (7-8) and acidic pH (~ 5), to examine DOM effects on whole-body Na+ concentration, unidirectional influx and efflux rates of Na+, and ammonia and urea excretion rates in Daphnia magna. Whole-body Na+ concentration, Na+ influx, and Na+ efflux rates were all unaffected regardless of pH, suggesting no influence of the various natural DOMs on active uptake and passive diffusion of Na+ in this organism. Ammonia and urea excretion rates were both increased by low pH. Ammonia excretion rates were reduced at circumneutral pH by the most highly colored, allochthonous DOM, and at low pH by all three natural DOMs, as well as by the commercial AHA. Urea excretion rates were not influenced by the presence of the various DOMs in circumneutral solutions, but were attenuated by the presence of two allochthonous DOM sources (isolated from Bannister Lake and Luther Marsh) at acidic pH. The observed reductions may be attributed partially to the higher buffering capacities of natural DOM sources, as well as their ability to interact with biological membranes as estimated by a new measure calculated from their acid-base titration characteristics, the Proton Binding Index (PBI).

Original languageEnglish
Pages (from-to)207-215
Number of pages9
JournalComparative Biochemistry and Physiology - C Toxicology and Pharmacology
Volume158
Issue number4
DOIs
Publication statusPublished - 2013

Fingerprint

Daphnia
2,5-Dimethoxy-4-Methylamphetamine
Fresh Water
Biological materials
Sodium
Ammonia
Humic Substances
Urea
Wetlands
Biological membranes
Lakes
Physiology
Protons
Titration
Acids
Membranes
Water

Keywords

  • Ammonia and urea excretion
  • Daphnia magna
  • Dissolved organic matter
  • Na metabolism

ASJC Scopus subject areas

  • Biochemistry
  • Cell Biology
  • Physiology
  • Health, Toxicology and Mutagenesis
  • Toxicology

Cite this

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title = "The effect of dissolved organic matter (DOM) on sodium transport and nitrogenous waste excretion of the freshwater cladoceran (Daphnia magna) at circumneutral and low pH",
abstract = "Dissolved organic matter (DOM), a heterogeneous substance found in all natural waters, has many documented abiotic roles, but recently, several possible direct influences of DOM on organism physiology have been reported. However, most studies have been carried out with a limited number of natural DOM isolates or were restricted to the use of commercial or artificial humic substances. We therefore employed three previously characterized, chemically-distinct natural DOMs, as well as a commercially available humic acid (Aldrich, AHA), at circumneutral (7-8) and acidic pH (~ 5), to examine DOM effects on whole-body Na+ concentration, unidirectional influx and efflux rates of Na+, and ammonia and urea excretion rates in Daphnia magna. Whole-body Na+ concentration, Na+ influx, and Na+ efflux rates were all unaffected regardless of pH, suggesting no influence of the various natural DOMs on active uptake and passive diffusion of Na+ in this organism. Ammonia and urea excretion rates were both increased by low pH. Ammonia excretion rates were reduced at circumneutral pH by the most highly colored, allochthonous DOM, and at low pH by all three natural DOMs, as well as by the commercial AHA. Urea excretion rates were not influenced by the presence of the various DOMs in circumneutral solutions, but were attenuated by the presence of two allochthonous DOM sources (isolated from Bannister Lake and Luther Marsh) at acidic pH. The observed reductions may be attributed partially to the higher buffering capacities of natural DOM sources, as well as their ability to interact with biological membranes as estimated by a new measure calculated from their acid-base titration characteristics, the Proton Binding Index (PBI).",
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T1 - The effect of dissolved organic matter (DOM) on sodium transport and nitrogenous waste excretion of the freshwater cladoceran (Daphnia magna) at circumneutral and low pH

AU - Al-Reasi, Hassan A.

AU - Yusuf, Usman

AU - Smith, D. Scott

AU - Wood, Chris M.

PY - 2013

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N2 - Dissolved organic matter (DOM), a heterogeneous substance found in all natural waters, has many documented abiotic roles, but recently, several possible direct influences of DOM on organism physiology have been reported. However, most studies have been carried out with a limited number of natural DOM isolates or were restricted to the use of commercial or artificial humic substances. We therefore employed three previously characterized, chemically-distinct natural DOMs, as well as a commercially available humic acid (Aldrich, AHA), at circumneutral (7-8) and acidic pH (~ 5), to examine DOM effects on whole-body Na+ concentration, unidirectional influx and efflux rates of Na+, and ammonia and urea excretion rates in Daphnia magna. Whole-body Na+ concentration, Na+ influx, and Na+ efflux rates were all unaffected regardless of pH, suggesting no influence of the various natural DOMs on active uptake and passive diffusion of Na+ in this organism. Ammonia and urea excretion rates were both increased by low pH. Ammonia excretion rates were reduced at circumneutral pH by the most highly colored, allochthonous DOM, and at low pH by all three natural DOMs, as well as by the commercial AHA. Urea excretion rates were not influenced by the presence of the various DOMs in circumneutral solutions, but were attenuated by the presence of two allochthonous DOM sources (isolated from Bannister Lake and Luther Marsh) at acidic pH. The observed reductions may be attributed partially to the higher buffering capacities of natural DOM sources, as well as their ability to interact with biological membranes as estimated by a new measure calculated from their acid-base titration characteristics, the Proton Binding Index (PBI).

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