Microb Ecol (1984) 10:151-164
MICROBIAL ECOLOGY | 1984 Springer-Verlag
Observations on Microbial Percent Respiration Values in Arctic and Subarctic Marine Waters and Sediments R. P. Griffiths, B. A. Caldwell, and R. Y. Morita Department of Microbiologyand College of Oceanography, Oregon State University, Corvallis,. Oregon, USA Abstract. Percent respiration was measured in over 1,100 arctic and subarctic marine water and sediment samples using 14C-labeled glucose and glutamate. These measurements were made at different times of the year in 4 regions. Percent respiration values were typically lower in regions where the waters o f large rivers mixed with seawater. They were also lower in sediments and in waters collected near the bottom than in surface waters. They were higher in winter arctic waters than water samples collected in the summer; however, a similar seasonal trend was not observed in subarctic waters. There were a num be r of studies in which there were significant positive rank correlations between percent respiration and salinity and between percent respiration and temperature. From what is known about the range o f temperature and salinity encountered in samples collected during these studies and the results o f temperature and salinity effects experiments, it was concluded that changes in these 2 variables did not explain the variation observed in percent respiration. Correlations between percent respiration and the inorganic nutrients PO4-a, NH4 + and NO3showed that o f the 3 variables, only NO3- showed relatively high correlations with all the same sign. From this it was concluded that there may be situations in which NO3- levels may influence percent respiration in nearshore marine waters. It is also likely that qualitative characteristics of the available organic nutrients may also influence percent respiration levels. Although no organic nutrient data is available for statistical analysis, the patterns o f percent respiration near river plumes and the relatively strong negative correlation often observed between uptake rates (heterotrophic activity) and percent respiration suggests that organic nutrients may be a factor in controlling percent respiration. It is suggested that there are situations in which percent respiration measurements may be used to document stress in natural microbial populations due to nutrient deficiencies.
Introduction
There have been a large number of studies where 14C labeled simple organic compounds have been used to measure microbial heterotrophic activity in marine and aquatic systems. In recent years, most of these studies have been
152
R . P . Griffiths et al.
conducted by measuring the incorporation of the carbon in these compounds into both cell material and CO2. From these measurements, one can determine what is called either a "percent respiration" or a "'percent mineralization" which is calculated by dividing the amount of label found in the respired CO2 by the total amount of substrate metabolized (cell material plus CO2). After reviewing much of the literature, Hoppe [ 17] concluded that the percent respiration for a given substrate was relatively constant. When large differences between studies were noted, these could often be explained by differences in the methods used to fix the cells at the end of the incubation period [8]. The consistency of percent respiration in a variety of amino acids was also documented during a study of estuarine waters [4]. Howevei'; there have been a number of studies in which percent respiration values for a given substrate have significantly varied even though the same technique had been used to make the measurements. Seasonal changes have been reported by Burnison and Morita [3], Gocke [6], Griffiths et al. [10], and Hanson and Snyder [ 14]. While studying heterotrophic activity in diverse saltmarsh soils, Hanson and Gardner [ 13] reported different alanine and aspartic acid percent respiration values in different soils. Gocke [6] observed a wide range of percent respiration values for a given 14C labeled substrate in water samples collected in seawater, brackish waters, and several freshwaters. This was true for a large variety of substrates. Percent respiration values for a large number of amino acids were also measured in Antarctic waters by Gillespie et al. [5] and Morita et al. [20]. Different percent respiration values for a given substrate were observed in different water samples but the relative ranking of percent respiration values for various substrates was generally consistent. Different percent respiration values have also been noted in river plumes relative to the surrounding seawater [11]. While studying heterotrophic activity in Georgia coastal waters, Hanson and Wiebe [15] reported increasing percent respiration values with increasing distance from shore. Tison and Pope [24] have also reported increasing percent respiration values in bacterial cultures that were stressed by increasing the incubation temperature. They suggested that the percent mineralization (percent respiration) might be used as an indicator of any type of stress on microbial populations. The objective of our studies was to measure percent respiration values in a large number of marine water and sediment samples so that spatial and temporal trends could be documented. Once these trends were documented, it was our objective to analyze these trends in terms of possible natural stress factors in the environment. Materials and Methods The locations o f the study areas are shown in Fig. 1. The data from 13 individual studies are presented here (Tables 1 and 2). All studies except the Beaufort Sea 6/75 and the Kasitsna Bay studies were conducted on board research vessels. During these cruises, extensive samplings were conducted in the areas shown in Figs. 2A-D. In addition, samples througout Cook Inlet were collected and analyzed. The station locations are illustrated in detail by Griffiths and Morita [12], and Griffiths et al. [111. Study 1 was conducted in an area near Point Barrow during which the samples were collected by the use of hand sampling devices from a small boat. The methods used
Observations on Percent Respiration
BARR~/'~-1~ POINT
~
=.
153
BEAUFORT
ALASKA
cook
I
Fig. 1. Locations of regions studied relative to the state of Alaska.
Table 1. Glucose and glutamate respiration percentages in water and sediment samples from Kasitsna Bay field stations Water Substrate
Date
Sediment
Median
Range
N~
Median
Range
N=
pb
MICROBIAL ECOLOGY | 1984 Springer-Verlag
Observations on Microbial Percent Respiration Values in Arctic and Subarctic Marine Waters and Sediments R. P. Griffiths, B. A. Caldwell, and R. Y. Morita Department of Microbiologyand College of Oceanography, Oregon State University, Corvallis,. Oregon, USA Abstract. Percent respiration was measured in over 1,100 arctic and subarctic marine water and sediment samples using 14C-labeled glucose and glutamate. These measurements were made at different times of the year in 4 regions. Percent respiration values were typically lower in regions where the waters o f large rivers mixed with seawater. They were also lower in sediments and in waters collected near the bottom than in surface waters. They were higher in winter arctic waters than water samples collected in the summer; however, a similar seasonal trend was not observed in subarctic waters. There were a num be r of studies in which there were significant positive rank correlations between percent respiration and salinity and between percent respiration and temperature. From what is known about the range o f temperature and salinity encountered in samples collected during these studies and the results o f temperature and salinity effects experiments, it was concluded that changes in these 2 variables did not explain the variation observed in percent respiration. Correlations between percent respiration and the inorganic nutrients PO4-a, NH4 + and NO3showed that o f the 3 variables, only NO3- showed relatively high correlations with all the same sign. From this it was concluded that there may be situations in which NO3- levels may influence percent respiration in nearshore marine waters. It is also likely that qualitative characteristics of the available organic nutrients may also influence percent respiration levels. Although no organic nutrient data is available for statistical analysis, the patterns o f percent respiration near river plumes and the relatively strong negative correlation often observed between uptake rates (heterotrophic activity) and percent respiration suggests that organic nutrients may be a factor in controlling percent respiration. It is suggested that there are situations in which percent respiration measurements may be used to document stress in natural microbial populations due to nutrient deficiencies.
Introduction
There have been a large number of studies where 14C labeled simple organic compounds have been used to measure microbial heterotrophic activity in marine and aquatic systems. In recent years, most of these studies have been
152
R . P . Griffiths et al.
conducted by measuring the incorporation of the carbon in these compounds into both cell material and CO2. From these measurements, one can determine what is called either a "percent respiration" or a "'percent mineralization" which is calculated by dividing the amount of label found in the respired CO2 by the total amount of substrate metabolized (cell material plus CO2). After reviewing much of the literature, Hoppe [ 17] concluded that the percent respiration for a given substrate was relatively constant. When large differences between studies were noted, these could often be explained by differences in the methods used to fix the cells at the end of the incubation period [8]. The consistency of percent respiration in a variety of amino acids was also documented during a study of estuarine waters [4]. Howevei'; there have been a number of studies in which percent respiration values for a given substrate have significantly varied even though the same technique had been used to make the measurements. Seasonal changes have been reported by Burnison and Morita [3], Gocke [6], Griffiths et al. [10], and Hanson and Snyder [ 14]. While studying heterotrophic activity in diverse saltmarsh soils, Hanson and Gardner [ 13] reported different alanine and aspartic acid percent respiration values in different soils. Gocke [6] observed a wide range of percent respiration values for a given 14C labeled substrate in water samples collected in seawater, brackish waters, and several freshwaters. This was true for a large variety of substrates. Percent respiration values for a large number of amino acids were also measured in Antarctic waters by Gillespie et al. [5] and Morita et al. [20]. Different percent respiration values for a given substrate were observed in different water samples but the relative ranking of percent respiration values for various substrates was generally consistent. Different percent respiration values have also been noted in river plumes relative to the surrounding seawater [11]. While studying heterotrophic activity in Georgia coastal waters, Hanson and Wiebe [15] reported increasing percent respiration values with increasing distance from shore. Tison and Pope [24] have also reported increasing percent respiration values in bacterial cultures that were stressed by increasing the incubation temperature. They suggested that the percent mineralization (percent respiration) might be used as an indicator of any type of stress on microbial populations. The objective of our studies was to measure percent respiration values in a large number of marine water and sediment samples so that spatial and temporal trends could be documented. Once these trends were documented, it was our objective to analyze these trends in terms of possible natural stress factors in the environment. Materials and Methods The locations o f the study areas are shown in Fig. 1. The data from 13 individual studies are presented here (Tables 1 and 2). All studies except the Beaufort Sea 6/75 and the Kasitsna Bay studies were conducted on board research vessels. During these cruises, extensive samplings were conducted in the areas shown in Figs. 2A-D. In addition, samples througout Cook Inlet were collected and analyzed. The station locations are illustrated in detail by Griffiths and Morita [12], and Griffiths et al. [111. Study 1 was conducted in an area near Point Barrow during which the samples were collected by the use of hand sampling devices from a small boat. The methods used
Observations on Percent Respiration
BARR~/'~-1~ POINT
~
=.
153
BEAUFORT
ALASKA
cook
I
Fig. 1. Locations of regions studied relative to the state of Alaska.
Table 1. Glucose and glutamate respiration percentages in water and sediment samples from Kasitsna Bay field stations Water Substrate
Date
Sediment
Median
Range
N~
Median
Range
N=
pb
