Humic substances: Part 2: Interactions with organisms

• Published in: Environmental science and pollution research international 2008-03, Vol.15 (2), p.128-135
• Main Authors: Steinberg, Christian E. W., Meinelt, Thomas, Timofeyev, Maxim A., Bittner, Michal, Menzel, Ralph
• Format: Article
• Language: English
• Subjects: Aging; Algae; Amphibians; Animals; Aquatic organisms; Aquatic plants; Aquatic Pollution; Atmospheric Protection/Air Quality Control/Air Pollution; ATP Binding Cassette Transporter, Sub-Family B - metabolism; Attractants; Biotransformation; Caenorhabditis elegans; Carbon; Cell Membrane - drug effects; Chemicals; Composts; Cyanobacteria; Danio rerio; Dissolved organic carbon; Earth and Environmental Science; Ecological effects; Ecology; Ecotoxicology; Embryos; Endocrine Disruptors - chemistry; Endocrine Disruptors - toxicity; Environment; Environmental Chemistry; Environmental Health; Enzymes; Eukaryota - drug effects; Eukaryota - metabolism; Fish; Fresh Water; Freshwater; Freshwater organisms; Gene Expression Regulation - drug effects; Heat-Shock Proteins - metabolism; Humic Substances; Indicator organisms; National parks; Nematoda; Nematodes; Offspring; Organic contaminants; Oxidative stress; Oxidizing agents; Oxygen - metabolism; Paradigms; Pheromones - chemistry; Photosynthesis; Photosynthesis - drug effects; Physiological responses; Plants - drug effects; Plants - metabolism; Review Series; Sodium - metabolism; Stress response; Studies; Tropical environments; Waste Water Technology; Water Management; Water Pollutants - chemistry; Water Pollutants - toxicity; Water pollution; Water Pollution Control
• ISSN: 0944-1344; 1614-7499
• DOI: 10.1065/espr2007.07.434

Goal, Scope and Background Freshwater bodies which chemistry is dominated by dissolved humic substances (HS) seem to be the major type on Earth, due to huge non-calcareous geological formations in the Northern Hemisphere and in the tropics. Based on the paradigm of the inertness of being organic, direct interactions of dissolved HS with freshwater organisms are mostly neglected. However, dissolved organic carbon, the majority of which being HS, are natural environmental chemicals and should therefore directly interact with organisms. Major results that widened our perspective on humic substance ecology come from experiments with the compost nematode, Caenorhabditis elegans , which behaved contradictorily to textbook knowledge and provoked an in-depth re-consideration of some paradigms. Approach To overcome old paradigms on HS and their potential interactions with organisms, we reviewed recent international literature, as well as ‘grey’ literature. We also include results from own ongoing studies. Results This review focuses on direct interactions of dissolved HS with freshwater organisms and disregards indirect effects, such as under-water light quenching. Instead we show with some macrophyte and algal species that HS adversely interfere with photosynthesis and growth, whereby closely related algal species show different response patterns. In addition to this, HS suppress cyanobacteria more than eukaryotic algae. Quinones in the HS appear to be the effective structure. Furthermore, HS can modulate the offspring numbers in the nematode C. elegans and cause feminization of fish and amphibians — they possess hormone-like properties. The ecological consequences of this potential remain obscure at present. HS also have the potential to act as chemical attractants as shown with C. elegans and exert a mild chemical stress upon aquatic organisms in many ways: induction of molecular chaperons (stress proteins), induction and modulation of biotransformation and anti-oxidant enzymes. Furthermore, they produce an oxidative stress with lipidperoxidation as one clear symptom or even stress defense strategy. Stronger chemical stresses by HS may even lead to teratogenic effects as shown with fish embryos; all physiological responses to HS-mediated stress require energy, which were compensated on the expense of yolk as shown with zebra fish embryos. One Finnish field survey supports the view of a strong chemical stress, as the weight yield in fish species decreases with in