Dynamics of Gut Bacteria Across Different Zooplankton Genera in the Baltic Sea.

In aquatic ecosystems, zooplankton-associated bacteria potentially have a great impact on the structure of ecosystems and trophic networks by providing various metabolic pathways and altering the ecological niche of host species. To understand the composition and drivers of zooplankton gut microbiota, we investigated the associated microbial communities of four zooplankton genera from different seasons in the Baltic Sea using the 16S rRNA gene. Among the 143 ASVs (amplified sequence variants) observed belonging to heterotrophic bacteria, 28 ASVs were shared across all zooplankton hosts over the season, and these shared core ASVs represented more than 25% and up to 60% of relative abundance in zooplankton hosts but were present at low relative abundance in the filtered water.

Sensitivity to hydrogen peroxide of the bloom-forming cyanobacterium Microcystis PCC 7806 depends on nutrient availability.

Application of low concentrations of hydrogen peroxide (HO) is a relatively new and promising method to selectively suppress harmful cyanobacterial blooms, while minimizing effects on eukaryotic organisms. However, it is still unknown how nutrient limitation affects the sensitivity of cyanobacteria to HO. In this study, we compare effects of HO on the microcystin-producing cyanobacterium Microcystis PCC 7806 under light-limited but nutrient-replete conditions, nitrogen (N) limitation and phosphorus (P) limitation.

Suppressing Cyanobacteria with Hydrogen Peroxide Is More Effective at High Light Intensities.

Hydrogen peroxide (HO) can be used as an emergency method to selectively suppress cyanobacterial blooms in lakes and drinking water reservoirs. However, it is largely unknown how environmental parameters alter the effectiveness of HO treatments. In this study, the toxic cyanobacterial strain PCC 7806 was treated with a range of HO concentrations (0 to 10 mg/L), while being exposed to different light intensities and light colors.

Changes in water color shift competition between phytoplankton species with contrasting light-harvesting strategies.

The color of many lakes and seas is changing, which is likely to affect the species composition of freshwater and marine phytoplankton communities. For example, cyanobacteria with phycobilisomes as light-harvesting antennae can effectively utilize green or orange-red light. However, recent studies show that they use blue light much less efficiently than phytoplankton species with chlorophyll-based light-harvesting complexes, even though both phytoplankton groups may absorb blue light to a similar extent.