Heterotrophic Utilization of Dissolved Organic Compounds in the Sea I. Size Distribution of Population and Relationship between Respiration and Incorporation of Growth Substrates
01 Nov 1970-Journal of the Marine Biological Association of the United Kingdom (Cambridge University Press)-Vol. 50, Iss: 4, pp 859-870
TL;DR: Interest in heterotrophic utilization of dissolved organic material by micro-organisms was recognized and discussed in principle by such workers as ZoBell, Waksman and Rakestraw in the thirties, but there has been very little subsequent progress in understanding the details of the process.
Abstract: Many aspects of the food web in the sea are ill understood: none more than the quantitative aspects of the heterotrophic activity of micro-organisms. Heterotrophic utilization of dissolved organic material by micro-organisms was recognized and discussed in principle by such workers as ZoBell, Waksman and Rakestraw in the thirties. There has been very little subsequent progress in understanding the details of the process, principally because of the lack of a suitable approach. Parsons and Strickland (1961) revived interest in this field when they introduced a simple radiochemical technique to follow the uptake of individual soluble organic compounds; subsequently Williams & Askew (1968) developed a method to measure the respiration of such compounds in sea-water samples.
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29 May 2006TL;DR: Reynolds as discussed by the authors provides basic information on composition, morphology and physiology of the main phyletic groups represented in marine and freshwater systems and reviews recent advances in community ecology, developing an appreciation of assembly processes, co-existence and competition, disturbance and diversity.
Abstract: Communities of microscopic plant life, or phytoplankton, dominate the Earth's aquatic ecosystems. This important new book by Colin Reynolds covers the adaptations, physiology and population dynamics of phytoplankton communities in lakes and rivers and oceans. It provides basic information on composition, morphology and physiology of the main phyletic groups represented in marine and freshwater systems and in addition reviews recent advances in community ecology, developing an appreciation of assembly processes, co-existence and competition, disturbance and diversity. Although focussed on one group of organisms, the book develops many concepts relevant to ecology in the broadest sense, and as such will appeal to graduate students and researchers in ecology, limnology and oceanography.
1,856 citations
TL;DR: To assess bacterioplankton production in the sea, a procedure for measuring growth based on incorporation of tritiated thymidine into DNA is developed; the accuracy of this procedure was tested under a variety of laboratory and field conditions.
Abstract: To assess bacterioplankton production in the sea, we have developed a procedure for measuring growth based on incorporation of tritiated thymidine into DNA; the accuracy of this procedure was tested under a variety of laboratory and field conditions. By autoradiography, we have found that for all practical purposes our technique is specific for the nonphotosynthetic bacteria and that virtually all of the “active” bacteria (one-third or more of the total countable bacteria) take up thymidine. We also measured (1) the intracellular isotope dilution of thymidine assessed by parallel experiments with labeled phosphorus, and (2) DNA content of natural marine bacteria (0.2 to 0.6 μm size fraction); a conversion factor derived from these data permitted estimation of production from thymidine incorporation results. A very similar conversion factor was independently derived from the empirical relationship between thymidine incorporation and growth of natural bacterioplankton under controlled conditions. Combined results show that this technique, which can be performed rapidly and easily at sea, provides good estimates of production. Data from Southern California Bight waters, which contain oligotrophic as well as moderately eutrophic regions, show that average bacterioplankton doubling times, like those of the phytoplankton, are on the order of a few days, with fastest growth at depths just below those of greatest phytoplankton abundance. Offshore bacterial production is roughly 5 to 25% of the primary production; thus, at a 50% assimilation efficiency, the bacterioplankton would consume 10 to 50% of the total fixed carbon.
1,495 citations
TL;DR: Although the ocean's food web has been studied for more than a century, several recent discoveries lead us to believe that the classical textbook model of a chain from diatoms through copepods and krill to fishes and whales may in fact be only a small part of the flow of energy.
Abstract: Few of us may ever live on the sea or under it, but all of us are making increasing use of it either as a source of food and other materials, or as a dump. As our demands upon the ocean in- crease, so does our need to understand the ocean as an ecosystem. Basic to the understanding of any ecosystem is knowledge of its food web, through which energy and materials flow. Flux of both energy and essential elements shapes or limits ecosystems, but only energy and organic compounds are con- sidered here. The related problems of limiting supplies of essential elements (N, P, Si, Fe) will be considered else- where (Pomeroy'). Although the ocean's food web has been studied for more than a century, several recent discoveries lead us to believe that the classical textbook de- scription of a chain from diatoms through copepods and krill to fishes and whales may in fact be only a small part of the flow of energy. Recent studies of microorganisms, dissolved organic mat- ter, and nonliving organic particles in the sea suggest the presence of other pathways through which a major part of the available energy may be flowing. Marine scientists have been approaching this view of the food web cautiously for decades, and caution is to be expected whenever an established paradigm is questioned (Kuhn 1962). Now there are many lines of evidence which suggest that a new paradigm of the ocean's food web is indeed emerging. THE ROLES OF MICROORGANISMS ocean, with 90% of the total area and the lowest mean rate of photosynthesis, accounts for 81.5% of primary produc- tion. Coastal waters over the continental shelves, with 9.9% of the total area and twice the rate of photosynthesis of the open ocean, account for 18% of primary production. The major upwellings, with 0.1% of the total area and a rate of photosynthesis nearly 10 times that of the open ocean, account for 0.5% of primary production. The real accuracy of these estimates is not as good as the three digit numbers suggest. The usual methods of estimating the photo- synthetic rate of phytoplankton do not measure all organic matter produced, and there is rarely enough replication to give us confidence limits for the values. The most obvious plants in the sea are the seaweeds, but they probably are not the most significant primary pro- ducers. Ryther (1963) estimates that seaweeds account for 10% of the pri- mary production of the ocean. Recent data on photosynthetic rates of kelp and other large seaweeds (Mann 1973) make that estimate seem high, although it is still difficult to make a good estimate on a planetary scale. Certainly, seaweeds and sea grasses are of major importance in the coastal zone. On a planetary scale phytoplankton are the major producers. Phytoplankton have been divided into two size groups, net plankton and nannoplankton. The separation is arbitrary, based on the aperture of what was once the finest bolting cloth for making plankton nets. Net plankton (>60 pm) have received considerable attention and form the basis of the established paradigm of the food web, but nannoplankton (<60 pm) have proven more difficult to study and until recently they have been neglected. Like net plankton, they are so sparsely distributed in the water that it is neces- sary to concentrate them in some fashion to see them at all. Because many of them cannot be preserved well, they must be studied at sea while alive. Only recently has high magnification, oil- immersion microscopy at sea permitted the study of living nannoplankton aboard ships. Efforts to understand the relative importance of net and nannoplankton have been made by several investigators, using the 14C technique (Steeman- Nielsen 1952), by counting separately the radioactivity retained on discs of bolting cloth and on fine membrane filters. This was a crude separation. Some organisms larger than the aperture of the bolting cloth would be forced through it in fragments, and if a suf- ficiently thick layer of plankton ac- cumulated on the bolting cloth, nanno- plankton would be retained by it. In spite of these shortcomings, at least a dozen studies produced consistent re- sults showing that the large diatoms and other net plankton, although highly visible and beautiful, account for a small fraction of total primary production. In a majority of cases nannoplankton ac- count for more than 90% of total photosynthesis (Table 1). This is true not only in the central gyres of the ocean, but in upwellings, coastal waters, and estuaries. No one seems to have made the separation in polar regions. However, Digby (1953) found that in Scoresby Sound, Greenland, nanno- plankton chlorophyll was always equal
1,286 citations
TL;DR: Natural assemblages of marine bacteria were cultured on combinations of C and N sources (amino acids, glucose, and NH,‘) to span a range of substrate C: N ratios to speculate that C : Ns of available substrates in marine waters is > 10 : 1.
Abstract: Natural assemblages of marine bacteria were cultured on combinations of C and N sources (amino acids, glucose, and NH,‘) to span a range of substrate C: N ratios from 1.5 : 1 to 10 : 1. Catabolic metabolism of the N component of amino acid substrates led to NH,+ regeneration during exponential growth. The efficiency of this regeneration (RN) and also of the carbon gross growth efficiency (GGE) generally was independent of the sources of C and N, but increased as the C : N ratio of the substrate (C : NJ decrcascd relative to the C : N ratio of the bacterial biomass (C : NJ. The clemental chemical composition (C : N: P ratio) of the bacterial biomass was relatively invariant at about 45 : 9 : 1 and the gross growth efficiency varied from a threshold value of about 40-50% at C : Ns > 6 : 1 up to 94% when C : N, was 1.5 : 1. Hence, R, varied from 00/o when C : N, was 10: 1 up to 86% when C: N, was 1.5 : 1. Inorganic sources of both N and P were taken up only in stoichiometric quantities during this phase of growth. Regeneration of NH,+ during the stationary phase as well as of POd3- occurred, most likely due to endogenous metabolism or cell death, but the magnitude of this regeneration seemed to increase greatly only when C: N, was ~6 : 1. Considering that amino acids frequently do not provide all of the N required and that carbohydrates often are the major C source for growth of marine bacteria, we speculate that C : Ns of available substrates in marine waters is > 10 : 1. Hence, actively growing bacteria may be inefficient remineralizers of N.
557 citations
01 Jan 1981
TL;DR: In this article, a strong linear correlation between the organic matter produced in the overlying water and the amount of organic matter consumed on the bottom in almost all of the coastal environments for which annual data are available.
Abstract: Our views of remineralization and nutrient cycling in coastal marine ecosystems have changed considerably over the last 30 years. The major trend has been an increasing appreciation for the complexity of processes involved, including some marked changes in our assessment of the importance of bacteria with respect to smaller animals and in our perception of the association between bacteria and particulate matter in the sea. Among the more recent developments in this area is a growing awareness of the importance of the coupling between benthic and pelagic communities in coastal waters. There appears to be a strong linear correlation between the organic matter produced in the overlying water and the amount of organic matter consumed on the bottom in almost all of the coastal environments for which annual data are available. The large amount of organic matter consumed by the benthos (perhaps 25–50 percent of that produced) is associated with a large flux of inorganic nutrients from the sediments to the overlying water. The stoichiometry of net benthic nutrient regeneration differs from that of pelagic regeneration, however, and simple Redfield type models probably cannot be applied. The amount of fixed inorganic nitrogen returned to the water across the sediment-water interface appears to be about half of that expected on the basis of the flux of phosphorus. This behavior, along with the fact that an appreciable amount of organic matter in coastal waters gets remineralized on the bottom, contributes to the low N/P ratio that is characteristic of these areas and may be responsible for the observation that nitrogen is commonly the nutrient most limiting for primary production. Recent direct measurements of the flux of dissolved N2 across the sediment-water interface indicate that denitrification is probably responsible for the loss of fixed nitrogen during decomposition in the sediments. If this is a widespread phenomenon, estuaries, bays, and other coastal waters may be major sinks in the marine nitrogen cycle and important terms in the global nitrogen budget. However, the fact that eutrophication appears to be an increasing problem in many estuaries is dramatic warning that anthropogenic nutrient inputs can overwhelm the recycling and remineralization processes in coastal waters.
545 citations
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TL;DR: In this article, a method is proposed in which the experiment is run in a closed system and the 14CO2 collected after killing and acidification is used to measure flux rates of organic compounds.
Abstract: The uptake of 14C-labeled organic compounds has been used by many workers to study heterotrophic microorganisms in natural waters. However, if flux rates of organic compounds are to be measured, the loss of 14CO2 during incubation becomes an important source of error. A method is proposed in which the experiment is run in a closed system and the 14CO2 collected after killing and acidification. Phenethylamine on chromatographic paper is the absorbing agent and the paper is counted by liquid scintillation. Studies of 19 compounds from pond water showed that 60% (aspartic acid) to 8% (arginine) of the labeled material entering the microorganisms was respired.
387 citations
TL;DR: In this article, a method is described, allied to the carbon-14 method for measuring photosynthesis, whereby the heterotrophic uptake of any chosen substrate in sea water can be measured using the substrate labelled by carbon 14.
246 citations
TL;DR: In this paper, it was shown that although a variety of marine organisms may utilize soluble organic compounds, bacteria dominate this activity and a measurement of the amount of soluble organic material oxidized will give a first approximation of bacterial activity.
Abstract: INTRODUCTIONOne of the longstanding problems in marine biology has been to determine the quantitative importance of bacteria in the regeneration of the inorganic nutrients. There probably still is no entirely satisfactory way of studying this. It is currently believed that although a variety of marine organisms may utilize soluble organic compounds, bacteria dominate this activity. Thus, a measurement of the amount of soluble organic material oxidized will give a first approximation of bacterial activity. Such an estimate may have to be revised at a later date to allow for the activity of other micro-organisms.
193 citations
TL;DR: A method is presented which provides information by means of the time-course study of the utilization of C'4 specifically labeled carbohydrates by growing microorganisms which will aid in recognizing the nature, estimating the extent of participation, and evaluating the function of the various carbohydrate catabolic pathways.
Abstract: In recent years much information has been obtained with regard to the pathways of glucose catabolism in microorganisms (Gunsalus et al. 1955). This has been due primarily to the intensive study of this problem by means of enzymatic and radioactive tracer methods. In evaluating the relative significance of the catabolic pathways in a given organism it is essential to know their nature and function as well as their extent of participation in the over-all picture of carbohydrate catabolism. Such knowledge is important in comparative studies and in understanding inter-group physiological relationships. In view of the large number of genera and species of microorganisms in existence it is obvious that a rapid but reasonably accurate method is desirable which will aid in recognizing the nature, estimating the extent of participation, and evaluating the function of the various carbohydrate catabolic pathways. In the present work, a method is presented which provides this information by means of the time-course study of the utilization of C'4 specifically labeled carbohydrates by growing microorganisms. The advantage of experiments of the time course type is apparent since they reveal the kinetic aspects as well as the over-all picture of substrate utilization (Wang et al., 1956). Interval radiochemical recoveries of substrate activity in the respiratory CO2 measure directly the rates at which the labeled carbon is converted
165 citations
89 citations