Effects of temperature and particles on nitrification in a eutrophic coastal bay in southern China

Abstract

Despite being the only link between reduced and oxidized nitrogen, the impact of environmental factors on nitrification, temperature and particles, in particular, remains unclear for coastal zones. By using the 15NH4+‐labeling technique, we determined nitrification rates in bulk (NTRB) and free‐living (NTRF, after removing particles >3 μm) for water samples with varying particle concentrations (as sampled at different tidal stages) during autumn, winter, and summer in a eutrophic coastal bay in southern China. The highest NTRB occurred in autumn, when particle concentrations were highest. In general, particle‐associated nitrification rates (NTRP, >3 μm) were higher than NTRF and increased with particle abundance. Regardless of seasonally distinctive temperature and particle concentrations, nitrification exhibited consistent temperature dependence in all cases (including bulk, particle‐associated, and free‐living) with a Q10 value of ~2.2. Meanwhile, the optimum temperature for NTRP was ~29°C, 5°C higher than that for NTRF although the causes for such a difference remained unclear. Strong temperature dependence and particle association suggest that nitrification is sensitive to temperature change (seasonality and global warming) and to ocean dynamics (wave and tide). Our results can potentially be applied to biogeochemical models of the nitrogen cycle for future predictions.

Substrate regulation leads to differential responses of microbial ammonia-oxidizing communities to ocean warming

“…Pure cultures of three strains of ammonia-oxidizing archaea (AOA) isolated from marine habitats have shown that AOA growth rates are positively correlated with temperature until their optimum temperatures ( T opt ) are reached 18 . Paradoxically, the limited number of field studies in marine environments 19 – 22 produced inconsistent results, i.e. positive and insensitive responses to temperature increase.…”

Dark Ammonium Transformations in the Pearl River Estuary During Summer

“…Similarly, such positive correlations have been obversed in the inner plume and river mouth of the Changjiang River (Hsiao et al, 2013) and San Francisco Bay (Damashek et al, 2016). The various regression slopes may be attributable to different grain size spectrum; nevertheless, the positive correlation was common in coastal seas (Bano & Hollibaugh, 2000; Freitag & Prosser, 2004; Hollibaugh et al, 2002; O'Mullan & Ward, 2005; Phillips et al, 1999; Wuchter et al, 2006; Zheng et al, 2017) and can also be found in freshwater systems (H. Y. Wang et al, 2010; Xia et al, 2009). Such intimate correlation can be attributed to particles providing more surface area for nitrifier attachment (Füssel et al, 2012; W. Y. Wang et al, 2010; Xia et al, 2009; Zhang et al, 2014).…”

Dissolved organic nutrients at the interface of fresh and marine waters: flow regime changes, biogeochemical cascades and picocyanobacterial blooms—the example of Florida Bay, USA

“…concentration) for nitrification is clearly not a limiting factor. High summer water temperatures (* 35°C) may inhibit nitrifying bacteria (e.g., Zheng et al 2017). Also, rates of nitrification during the early phases of the time course may be low due to elevated pH (e.g., Huesemann et al 2002, Kemp et al 2005, as pH is known to be an important regulator of NH 3 oxidizer communities (e.g., Damashek and Francis 2018).…”