Bacterial community shift is induced by dynamic environmental parameters in a changing coastal ecosystem (northern Adriatic, northeastern Mediterranean Sea) – a 2‐year time‐series study

Abstract

The potential link between the microbial dynamics and the environmental parameters was investigated in a semi-enclosed and highly dynamic coastal system (Gulf of Trieste, northern Adriatic Sea, NE Mediterranean Sea). Our comprehensive 2-year time-series study showed that despite the shallowness of this area, there was a significant difference between the surface and the bottom bacterial community structure. The bottom bacterial community was more diverse than the surface one and influenced by sediment re-suspension. The surface seawater temperature had a profound effect on bacterial productivity, while the bacterial community structure was more affected by freshwater-borne nutrients and phytoplankton blooms. Phytoplankton blooms caused an increase of Gammaproteobacteria (Alteromonadaceae, SAR86 and Vibrionaceae) and shift in dominance from SAR11 to Rhodobacteraceae taxon at the surface. Our results propose the importance of the water mass movements as drivers of freshwater-borne nutrients and of allochthonous microbial taxa. This study emphasizes the prediction power based on association networks analyses that are fed with long-term measurements of microbial and environmental parameters. These interaction maps offer valuable insights into the response of marine ecosystem to climate- and anthropogenic-driven stressors.

Seasonal variation in marine-snow-associated and ambient-water prokaryotic communities in the northern Adriatic Sea

“…In contrast, the high proportion of chloroplast-affiliated clones obtained from marine snow in December indicates a phytoplankton origin of the marine-snow matrix (Fig. 4), most likely derived from the diatom bloom that typically occurs in late autumn (Mozeti et al 2012) and which was also observed in December 2009 (Tinta et al 2014). However, the presence or high abundance of bacterial groups characteristic of low salinity estuarine or fresh waters, like Betaproteobacteria, Verucomicrobia and Actinobacteria (Kirch man et al 2005, Alonso et al 2010) might indicate a freshwater origin for a part of the bacterial community detected in marine snow in December.…”

Microbial Surface Colonization and Biofilm Development in Marine Environments

“…Alteromonas produces and secretes a variety of extracellular enzymes that contribute to the hydrolysis of biopolymers, including polysaccharides (253)(254)(255)(256)(257), proteins (258,259), nucleic acids (260,261), and lipids (262), the major components of marine POM. Alteromonas and related species respond rapidly to phytoplankton blooms and especially to elevated POC concentrations (109,(263)(264)(265). Algal exudates from a variety of phytoplankton can be utilized by Alteromonas, making them a major microbial group in algal phycospheres (266)(267)(268).…”

“…creasing incidence of human vibrio illnesses worldwide are linked to phytoplankton blooms, ocean warming, and the capacity of vibrios to colonize surfaces (15,265,(560)(561)(562)(563)(564). Higher temperature also significantly increases population abundance and upregulates virulence determinants such as motility, resistance to antimicrobial compounds, hemolysis, and cytotoxicity in coral pathogens (565,566).…”

“…These bacteria are generally heterotrophs, able to metabolize a variety of labile and recalcitrant organic substrates, including monocyclic and polycyclic aromatic hydrocarbons as well as various algal osmolytes and other metabolites (173,175,272,594,(762)(763)(764)(765)(766)(767). They usually react to and grow quickly after small increases in levels of labile organic substrates, such as amino acids, simple sugars, and DMSP, especially during the initial phase of algal blooms (8,13,252,265,272,(768)(769)(770)(771)(772).…”

Bacterial Diversity in the South Adriatic Sea during a Strong, Deep Winter Convection Year

“…Studies describing Adriatic picoplankton diversity mainly focused on coastal waters (11,12). In addition, temporal studies were exclusively done in the northern coastal waters (13)(14)(15)(16). Deep winter convective mixing was shown to shape the community structure via the transport of nutrients, i.e., phosphorus and nitrogen, to the euphotic zone, consequently triggering blooms of photosynthetic microorganisms in early spring (17).…”