Temperature, organic matter, and the control of bacterioplankton in the Neuse River and Pamlico Sound estuarine system

Abstract

A 4 yr, spatially extensive study of the Neuse River and Pamlico Sound estuarine system, North Carolina, was used to evaluate the temporal patterns and bottom-up controls of the resident bacterioplankton community. This meso-to eutrophic estuarine system had high concentrations of dissolved and particulate organic matter and supported an active and abundant phytoplankton community. Temporal analysis of bacterioplankton productivity (BP) revealed a strong seasonal pattern, similar to water temperature. Comparisons of BP and several environmental variables grouped by season and year showed little correspondence between the bacteria and either river discharge or organic matter at either scale. Temperature explained about half of the variation in BP data, but without any obvious threshold in the semi-log temperature-productivity relationship, implying the absence of a shift to substrate limitation at higher temperatures. The temperature effect varied in space and was lower at the freshwater station, suggesting differential substrate availability or the presence of a different resident microbial community. Proxies for bacterial substrates, including dissolved organic carbon, particulate organic nitrogen, and chlorophyll a, improved the predictive power in multiple regression models, but at least one-third of the variation in BP remained unexplained. The regression models differed by station group, further highlighting the possible difference in biota and/or resources between the freshwater and brackish sites.

Lingering Carbon Cycle Effects of Hurricane Matthew in North Carolina's Coastal Waters

“…Carbon isotope values for estuarine phytoplankton can range between −35‰ and −20‰, influenced strongly by inorganic C sources used during primary production (Bouillon et al, ); δ 13 C‐DIC values in the NRE‐PS ranged between −3‰ and −16‰ (Figure S4) and could explain the depleted δ 13 C‐POC values for samples in the estuary and sound. These samples also had C:N values between 6 and 10, close to median ranges for the NRE‐PS (Peierls & Paerl, ). While the breadth of these values overlap between strict terrigenous or marine (planktonic) sources, POC in the sound appeared to be influenced more by planktonic sources, based on C:N values generally <10, especially well after the storm (Figure S5).…”

“…Because exchange with the coastal ocean is restricted to a few narrow tidal inlets, residence time in the PS is relatively long (~1 year), enabling substantial degradation of organic matter (Lin et al, 2007). After Matthew, the relatively clear, sunny weather in late October into November occurred when water temperatures in the NRE-PS remained between 10 and 20°C, a range over which bacterial production tends to increase and was maximized following pulses of floodwater following Hurricane Isabel in 2003 (Peierls & Paerl, 2010). We suspect that the lingering effect of these EWEs is the sustained mineralization of terrestrial DOC to CO 2 following these pulses, which played a key role in sustaining the large observed CO 2 emissions.…”

Vibrio Ecology in the Neuse River Estuary, North Carolina, Characterized by Next-Generation Amplicon Sequencing of the Gene Encoding Heat Shock Protein 60 ( hsp60 )

“…2 and are typical of the highly variable conditions in the NRE, with the exception of those associated with Hurricane Matthew, which can be considered an extreme event on the basis of the observed influx of freshwater discharge and corresponding changes in salinity, chlorophyll a, and nutrient concentrations. Storm-related freshwater pulses in the NRE were previously shown to decrease residence times and salinity and contribute to elevated nutrient concentrations (34).…”

Hydrological and biogeochemical controls on watershed dissolved organic matter transport: pulse‐shunt concept

“…According to the Q 10 law, bacterial respiration and production are affected by temperature (Bott and Kaplan , Sander and Kalff , Fischer et al. , Peierls and Paerl ), with the rates of these processes generally increasing by a factor of 2–3 for every 10°C rise in temperature. In fact, a Q 10 of 2 for the bacterial uptake of riverine DOM has been demonstrated in the lab (Raymond and Bauer ).…”