Temperature Characteristics of Photosynthetic and Heterotrophic Activities: Seasonal Variations in Temperate Microbial Plankton

Abstract

The seasonal variation in temperature characteristics of photosynthetic and heterotrophic activities in the microbial plankton of Bedford Basin, Nova Scotia, was investigated. Measurements were made of the photosynthetic uptake of [14C]bicarbonate and its incorporation into cellular protein as well as the heterotrophic uptake of 3H-labeled amino acids and their incorporation into cellular protein. Activity-temperature curves were analyzed objectively by nonlinear estimation of parameters from various mathematical models. Over the seasonal cycle, the cardinal temperatures and a parameter formally equivalent to the thermodynamic enthalpy of activation for most of the four processes measured were positively correlated with the water temperature. The temperature sensitivity of metabolic activity (i.e., change in activity per unit change in temperature) was indexed by the tangent to the activity-temperature curves. When this index was expressed in dimensionless form by normalization to the scaling factor of the activity-temperature curves, the resulting relative temperature sensitivity, evaluated at the prevailing temperature, proved to be statistically invariant throughout the year. During the height of the spring bloom, the water temperature (-0.3°C) was not so low as to inhibit metabolic activity of either the phytoplankton or the bacterioplankton. The evidence suggests that 2282

Comparison of temperature effects on soil respiration and bacterial and fungal growth rates

“…1-3). This has earlier been shown to be the case for bacterial growth in soil [5] and water [25], and for fungi in soil [10]. The Ratkowsky model has also been found to adequately describe the temperature dependence of soil respiration [5,18,35] and the total activity under anaerobic conditions (denitrification, [36]), and it has been used to model the decomposition of crop residues in soil [35,37,38].…”

“…1-3(e), (f)). This has been observed several times, both for pure cultures [23,24] and communities [5,25] and is due to Q 10 not being constant but increasing at lower temperatures [2][3][4]. To adjust for the variation in Q 10 , models with more variables have been used [2][3][4]40,41].…”

“…t min will in many environmental studies fall below the freezing point of water (e.g. [5,10,25]), which of course is physiologically meaningless. That is why t min is denoted apparent minimum temperature for growth.…”

Predictions of response to temperature are contingent on model choice and data quality

“…4 4 (Li & Dickie, 1987) citing (Hinshelwood, 1947) 5 4 (Li & Dickie, 1987) citing (Johnson, Eyring, & Williams, 1942) 6 6 (Heitzer et al, 1991) 7 4 (Montagnes et al, 2008) citing (Schoolfield, Sharpe, & Magnuson, 1981) 8 3 (Li & Dickie, 1987) citing (Stoermer & Ladewski, 1976) 9 4 (Montagnes et al, 2008) 10 4 (Thomas et al, 2012) citing (Norberg, 2004) 11 3 (Montagnes et al, 2008) 12 3 (Montagnes et al, 2008) citing (Flinn, 1991) 13 4 (Ratkowsky et al, 1983) 14 5 (Kamykowski, 1986) 15 5 (Boatman et al, 2017) R = Universal gas (Boltzmann) constant.…”

Increased microbial activity in a warmer and wetter climate enhances the risk of coastal hypoxia

“…Temperature is generally found to promote community respiration in estuarine environments, but chlorophyll also contributes to explain the variance in this parameter (Hopkinson & Smith, 2005). Some field studies have shown a positive effect of temperature on both bacterial growth and bacterial respiration (Vaque et al, 2009;Kritzberg et al, 2010), while other studies have suggested that bacterial growth is less dependent on temperature (Li & Dickie, 1987;Wikner & Hagstr€ om, 1999). The importance of temperature is further supported by mesocosm experiments, which have shown a positive effect of temperature, primarily on respiration but also on the timing of peak bacterial secondary production (Hoppe et al, 2008;Wohlers et al, 2009).…”