Hidrológiai Közlöny 1967 (47. évfolyam)
7. szám - A „Szervesanyag meghatározási problémák édesvizekben” című 1966. szeptember 25–28. között Tihanyben rendezett Szimpózium előadásai - Allen, Harold L.: Heterotróf baktériumok acetáthasznosítása egy tóben
Hidrológiai Közlöny 1967. 7. sz. 295 Acetates utilization by heterotrophic bacteria in a pond* HAROLD L. ALLÉN** Abstraet The utilization of acetate (C I 4-labeled) due to bacterial heterotrophy has been measured in samples collecteil horizontally and vertically from within a pond (Laké Lötsjön, Sundbvberg, Sweden). Through Michaelis-Menten enzyme kineties, employing a mathematical and graphieal treatment, it was possible to determine the in situ rangeS of the following kinetic parameters associated with acetate uptake: 1) the theoretical maximum velocity of substrate removal, 2) an approximation of the natural substrate concentration, and 3) a meaSure of the natural regeneration time for acetate. NumerouS chemical and physical parameters, including the measurement of dissolved and particulate (oxidizable) organic carbon present, accompanied the determination of heterotrophic activities of purposes of evaluation and comparison. The maximum rate of acetate uptake was found to be within the rangé 6.9—17.4 fig acetate 1 hr _ I, natural substrate approximations within the rangé 5— 150 fig acetate 1 _ I, and natural turnover times within the rangé 0.4—8.8 hours. Most kinetic measurements indicate maximum velocities of acetate removal are associated with concentrations of dissolved organic carbon in different portions of the pond. No distinct correlations were evident between measured chemical and physical properties (excluding dissolved organic carbon) and heterotrophic activities utilizing acetate as a substrate. * Methods have only recently been presented that make it possible to determine the varions kinetic parameters associated with the heterotrophic ntilization of dissolved organic matter in several fresh waters (Wright and Hobbié, 1965a, 1965b, 1966; Hobbié and Wright, 1965a, 1965b). Applications of the Wright and Hobbié methods to natural fresh water systems are few. The majority of recent investigators have limited in situ and in vivo experimentation to the assessment of theoretical maximum velocities of uptake, substrate approximations and natural turnover times due to the heterotrophic uptake of simple hexoses and acetate from a verticai water column (Wright and Hobbié, 1965a, 1965b, 1966; Hobbié and Wright, 1965a, 1965b; Wetzel, 1966; Allén, in preparation). Similar applications to fresh water systems include the use of Wright and Hobbié techniques to follow annual cycles of the uptake kineties of several organic solutes (J. E. Hobbié, personal communication). Other pertinent applications include the use of kinetic parameters for the comparison of different bodies of fresh water, with respect to several dissolved organic compounds and natural rates of heterotrophic utilization (Wetzel, 1966.) The objective of the present investigation is to show the significance of measuring the heterotrophic removal of acetate, in terms of Michaelis— * Institute of Limnology, Uppsala University, TJppsala, Sweden. * Contribution No. 000, Institute of Limnology, Uppsala University, Uppsala, Sweden, and Contributio n No. 000, W. K. Kellogg Biological Station, Michigan State University, Hickory Corners, Michigan 49060. ** Present address: W. K. Kellogg Biological Station, Michigan State University, Hickory Corners, Michigan 49060. Menten enzyme kineties (treated in detail in Wright and Hobbié, 1965a, 1965b, 1966), in aliquots of fresh water collected horizontally from a depth of 0.5 m at six stations over the surface of a small pond, and vertically from a depth of 1.5 and 2.5 m at the deepest portion of the pond. Natural ranges of kinetic parameters operatíve within the whole of a given body of fresh water have not previously been investigated. Values obtained from a verticai column, even from the greatest depth in the system may or may not be representative for the entire system. Morphometric, geochemical and biological differences between different portions of a laké, pond. or other enclosed body of fresh water would probably preclude the use of generál characterizations when trying to accurateiy define the system. In most instances it would be difficult to obtain a. complete picture of the in situ heterotrophic utilization of dissolved organic matter on the basis of limited measurements made within a single water column. Because of qualitative and quantitative differences involved, when working with natural populations, it is important to ascertain horizontal and verticai differences in heterotrophic activities. The heterotrophic utilization of acetate was measured in samples collected from a small pond, Laké Lötsjön, located in Sundbyberg northwest of Stockholm, Sweden. Ali samples were collected and subsequently analyzed on August 14, 1965. Water samples were collected with a Ruttner sampler from a depth of 0.5 m at six stations (Figure 1A) represent verticai distribution (maximum depth 2.8 m at station 6). Samples were transported to the laboratory in a thermally insulated Container at approximately 10°C. In situ thermal conditions at the time of sampling are indicated in Table 1. Totál nitrogén was measured according to the modified Kjeldahl method (E. Jonsson, unpublished); nitrate-nitrogen was measured by the modified Mullin and Riley method (Strickland and Parsons, 1960). Totál phosphorus and phosphatephosphorus were measured according to the method by Proctor and Hood (1954). Bicarbonate was determined by calculation after measuring the pH and determining the alkalinity (A') according to the Berger method (mimeographed, Uppsala). Oxygen was determined according to the modified Winkler method (Arner. Publ. Health Ass., et. al., 1960). Dissolved organic carbon was determined according to the infrared carbon dioxidé method by Menzel and Vaccaro (1964); particulate (oxidizable) organic carbon was ascertained by the spectrophotometric method of Strickland amd Parsons (1960). Measurements of the heterotophic uptake of radioactively labeled acetate (C 1 4-labeled, high specific activity) followed the micro-method given in Wright and Hobbié (1965a). Essentially the Wright and Hobbié method consists of adding micro-amounts (25, 50, 100, and 200 /íl of a b/ic ml1 solution) of high specific
