Distinct actors drive different mechanisms of biopolymer processing in polar marine coastal sediments.

Heterotrophic bacteria in the ocean initiate biopolymer degradation using extracellular enzymes that yield low molecular weight hydrolysis products in the environment, or by using a selfish uptake mechanism that retains the hydrolysate for the enzyme-producing cell. The mechanism used affects the availability of hydrolysis products to other bacteria, and thus also potentially the composition and activity of the community. In marine systems, these two mechanisms of substrate processing have been studied in the water column, but to date, have not been investigated in sediments.

Niche separation in bacterial communities and activities in porewater, loosely attached, and firmly attached fractions in permeable surface sediments.

Heterotrophic microbes are central to organic matter degradation and transformation in marine sediments. Currently, most investigations of benthic microbiomes do not differentiate between processes in the porewater and on the grains and, hence, only show a generalized picture of the community. This limits our understanding of the structure and functions of sediment microbiomes.

Reactive oxygen species affect the potential for mineralization processes in permeable intertidal flats.

Intertidal permeable sediments are crucial sites of organic matter remineralization. These sediments likely have a large capacity to produce reactive oxygen species (ROS) because of shifting oxic-anoxic interfaces and intense iron-sulfur cycling. Here, we show that high concentrations of the ROS hydrogen peroxide are present in intertidal sediments using microsensors, and chemiluminescent analysis on extracted porewater.

Microbial community composition of sediments influenced by intensive mariculture activity.

Marine aquaculture is a major industry that supports the economy in many countries, including the Philippines. However, excess feeds and fish waste generated by mariculture activities contribute an immense nutrient load to the environment that can affect the underlying sediment. To better understand these impacts, we compared the physicochemical characteristics and microbial community composition of sediments taken at a fish cage and an off cage site in Bolinao, Philippines.