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Accumulation of free amino acids and humic substances in a freshwater modular system and their ecological significance
Author(s) -
THOMAS J.D.,
EATON P.
Publication year - 1996
Publication title -
freshwater biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.297
H-Index - 156
eISSN - 1365-2427
pISSN - 0046-5070
DOI - 10.1046/j.1365-2427.1996.d01-467.x
Subject(s) - snail , incubation , biomphalaria glabrata , amino acid , biology , freshwater snail , ceratophyllum demersum , macrophyte , botany , axenic , algae , aquatic plant , dry weight , environmental chemistry , zoology , ecology , chemistry , biochemistry , bacteria , genetics , schistosoma mansoni , helminths , schistosomiasis
1. Methods for measuring concentrations of total and individual free amino acids (TFAA, FAA), other amino compounds and humic substances (HS) in media containing the following three treatments and the control are described: (i) the non‐axenic aquatic macrophyte Ceratophyllum demersum alone; (ii) the pulmonate snail, Biomphalaria glabrata alone; (iii) the snail, plant and the epiphytic bacteria and algae together as a four‐component modular system; (iv) control without organisms. 2. TFAA accumulated to give asymptotic values of 2.5 μ m , 10 μ m and 15 μ m in treatments (i), (ii) and (iii), respectively, by the end of the 30‐day incubation period. The mass‐specific accumulation rate in the treatment with the snail alone [89.4 nmol g –1 (wet weight minus shell) day –1 ] was approximately ten times that with the plant alone [8.4 nmol g –1 (wet mass) day –1 ]. No FAA or HS could be detected at any time in (iv). 3. On the second day of incubation the concentrations of TFAA and of some individual amino acids were significantly higher in the treatment containing the snail and plant together than the sum of the concentrations in the treatments with the plant and snail alone, presumably due to an increase in the snails’ metabolic rate and ‘sloppy feeding’. 4. The differences in the relative abundance of amino compounds accumulating in media conditioned by snails alone (e.g. much larger proportions of ammonia, ethanolamine and phosphoserine than in plant‐conditioned media) and plants alone (e.g. larger proportions of asparagine and glutamine than in snail‐conditioned media) suggest that snails and plants may derive mutual benefits by exchanging amino compounds. 5. The accumulation patterns of the more recalcitrant HS differ from those of the amino acids in two respects. First, the HS concentrations continued to increase throughout the 30‐day incubation period in all three treatments. Second, most of the HS in the module originates from the plant as both the concentrations and mass‐specific accumulation rates were significantly higher in the treatment with the plant alone [2.6 mg l –1 , 9.09 μg g –1 (wet mass) day –1 , respectively] than in the treatment with the snail alone [0.75 mg l –1 and 7.7 μg g –1 (wet mass) day –1 , respectively]. 6. The possible reasons for the differences in the accumulation patterns of FAA and HS in the three treatments are discussed. Evidence is also given in support of the testable hypothesis that the four components of the module derive several mutual benefits, including those arising from the release of dissolved organic matter, such as FAA and HS, by living organisms.