Phosphatases relieve carbon limitation of microbial activity in Baltic Sea sediments along a redox‐gradient

Abstract

The relationship between phosphatase activity and the element limiting microbial activity (carbon [C], nitrogen [N], or phosphorus [P]) was studied experimentally in sediment from four stations in the Baltic Sea located along a depth transect from oxic to anoxic bottom waters. The role of extracellular phosphatases was assessed by determining the percentages of intact cells that could be labeled with an artificial substrate for phosphatases (i.e., enzyme-labeled fluorescence 97 phosphatase substrate [ELF]) using a flow cytometer. Phosphatase activity was detected in sediment slurries from all sites either with or without prior incubation under oxic or anoxic conditions. In addition, ELF-labeled cells were detected in all incubated sediments, indicating that intact cells bearing phosphatases contribute to the phosphatase activity. Phosphatase activities and percentages of ELF-labeled cells were lower for the anoxic than for the oxic slurry incubations. Phosphatases are likely used to relieve the limitation of microbial activity by utilizable C in these recently deposited, organic C-rich sediments in the Baltic Sea. In marine sediments overlain by anoxic bottom waters, the biological and chemical mechanisms of P retention are often less efficient than in oxic settings and the P released to relieve C limitation escapes to the overlying water. This explains the ongoing higher P fluxes from sediments overlain by anoxic bottom waters.

Holocene Refreshening and Reoxygenation of a Bothnian Sea Estuary Led to Enhanced Phosphorus Burial

“…3). This is in accordance with the general observation that P org is often inefficiently retained in sediments of hypoxic basins (Algeo and Ingall 2007) due to preferential release of P org from organic matter by C-limited microbes (Ingall et al 1993;Steenbergh et al 2011Steenbergh et al , 2013. Such sediments are characterized by sedimentary C org /P org ratios above the Redfield ratio for marine organic matter, just as we observe here (>400 versus 106 mol/mol; Online Resource 6).…”

Extracellular Enzyme Activity and Microbial Diversity Measured on Seafloor Exposed Basalts from Loihi Seamount Indicate the Importance of Basalts to Global Biogeochemical Cycling

“…2 and Table 2) has also been described in other studies (5,44). An experiment to quantify this loss did not indicate any measure- Top, data include LAP and AP activities from various substrates normalized to nmol g Ϫ1 h…”

“…The basalt LAP activity rates overlap the lower end of sedimentary activities (5,41), are at the higher end of rates from the water column in fjords (42), and are higher than data from the marine water column (6,43). The AP activity rates measured on Loihi basalts are within the midrange of activities measured in marine sediments (44), seawater particles (39), a cored coral reef mound (40), and subsurface hydrothermal fluids (45). The basalt AP activity is higher than water column measurements (43,46).…”

Do NH 3 and chemical oxygen demand induce continuous release of phosphorus from sediment in heavily polluted rivers?

“…The negative relationship between DO and SRP (p < 0.01, R 2 = −0.838) in surface water indicates that DO may trigger release or adsorption of SRP. P recycling in sediments is enhanced under anoxic conditions in the absence of amorphous Fe 3+ , which has a strong affinity for dissolved phosphate and promotes enhanced microbial phosphate release (Ingall et al, 1993;Steenbergh et al, 2011). Further, Fe 3+ and Mn 5+ oxides may be directly involved in the adsorption and hydrolysis of Po compounds, and may influence P release from sediment (Olsson et al, 2010;Huang and Zhang, 2012).…”