Diel fluctuations in bacterial activity on streambed substrata during vernal algal blooms: Effects of temperature, water chemistry, and habitat

Abstract

Diel fluctuations in stream water temperature and chemistry, microbial biomass, and bacterial activity were measured in White Clay Creek, Pennsylvania, during vernal algal blooms in three different years. DOC concentrations increased 24-37% over early morning minima and temperature increased nearly 10°C over a 7-10-h period. Total carbohydrates and monosaccharides exhibited irregular fluctuations with total carbohydrates showing concentration peaks in the morning and afternoon. Acetate concentrations were highest in midafternoon, while the concentration pattern for primary amines differed from the DOC pattern with highest values at midnight. No distinct diel patterns were found for streambed ATP, GTP : ATP, Chl a, and total or active bacteria, although significant year-to-year and between-habitat differences were observed. Bacterial activity, measured by phospholipid biosynthesis, total lipid biosynthesis, respiration, and incorporation of [3H]thymidine into DNA increased 1.4-fold to 3.0-fold from morning to afternoon. Microcosm experiments indicated that the activity of bacteria attached to sediments was more sensitive to increases in water temperature than to changes in water chemistry, whereas bacteria attached to porcelain disks responded to the influences of both temperature and water chemistry.

Altitudinal patterns of diversity and functional traits of metabolically active microorganisms in stream biofilms

“…Furthermore, the combination of elevated physical disturbance (e.g., hydrology) on microbial communities (Widder et al, 2014) upstream with the observation that postdisturbance recovery of specialists is less successful than for generalists (Clavel et al, 2011) may further contribute to the spatial patterns of functional traits we observed in this study. Finally, benthic algae which provide the bulk DOC source in streams above the treeline exude compounds, often monomeric in nature, that do not require specialised metabolic pathways and that are therefore readily available to a wide range of microbial heterotrophs (Kaplan and Bott, 1989). These combined effects may further contribute to the specialisation pattern that we observed along the study streams.…”

“…In alpine streams, autochthonous deliveries from algal production (and mosses) characterise DOC in streams above the treeline, whereas terrestrial deliveries increasingly add to the carbon pool further downstream (Battin et al, 2004;Milner et al, 2009;Zah and Uehlinger, 2001). Several studies have reported DOC source and composition as potential drivers of microbial community structure and functioning in streams (e.g., Kaplan and Bott, 1989;Sun et al, 1997;Peter et al, 2011) and in lakes (e.g., Crump et al, 2003;Judd et al, 2006). However, only few have studied the relationship between DOC characteristics and microbial functional traits in streams (McArthur et al, 1985;Koetsier et al, 1997).…”

Quantifying the production of dissolved organic nitrogen in headwater streams using 15N tracer additions

“…From these studies in relatively pristine low-nutrient streams, DO 15 N production represented no more than 10% of assimilated 15 N tracer. In addition, Kaplan and Bott (1989) found that labile constituents of DON (dissolved free amino acids) exhibited diel cycles associated with a vernal algal bloom in a stream draining an agricultural landscape (White Clay Creek, Pennsylvania). Our results from 15 streams indicate that instream DON production represented a median of 8-17% of total NO { 3 uptake and was therefore a potentially large transformation of N. By including the study of streams with varying nutrient status, our results refine our understanding of N cycling in headwater streams, where DON inputs have previously been assumed to be dominated by allochthonous sources (Aitkenhead- Peterson et al 2003).…”

“…Because production of dissolved organic carbon (DOC) by in-stream processes can be significant (Kaplan and Bott 1989), DON production may also be significant in streams. Production of autochthonous dissolved organic matter (DOM, a portion of which is DON) by aquatic biota can occur through several mechanisms, including the release of cell constituents via death, senescence, viral lysis, or herbivory (Baines and Pace 1991;Bertilsson and Jones 2003), and these processes occur in both autotrophs (e.g., algae, macrophytes) and heterotrophs (i.e., bacteria, fungi).…”

“…Kaplan and Newbold (2003) suggested that monomeric forms of DON, which are compounds likely resulting from autotrophic DON production, constitute only a small proportion of the total DON pool in streams. Yet monomeric forms of DON are rapidly taken up in stream both by benthic biofilms (Johnson et al 2009) and via uptake in hyporheic zones (Brookshire et al 2005).…”