TY - JOUR

T1 - Seasonal development of a tidal mixing front drives shifts in community structure and diversity of bacterioplankton

AU - King, Nathan

AU - Wilmes, Sophie-Berenice

AU - Browett, Samuel S

AU - Healey, Amy

AU - McDevitt, Allan D.

AU - McKeown, Niall J.

AU - Roche, Ronan

AU - Skujina, Ilze

AU - Smale, Dan

AU - Thorpe, Jamie

AU - Malham, Shelagh

N1 - European Regional Development Fund UK Research and Innovation. Grant Number: MR/S032827/1

PY - 2023/9/5

Y1 - 2023/9/5

N2 - Bacterioplankton underpin biogeochemical cycles and an improved understanding of the patterns and drivers of variability in their distribution is needed to determine their wider functioning and importance. Sharp environmental gradients and dispersal bar-riers associated with ocean fronts are emerging as key determinants of bacterioplank-ton biodiversity patterns. We examined how the development of the Celtic Sea Front (CF), a tidal mixing front on the Northwest European Shelf affects bacterioplankton communities. We performed 16S- rRNA metabarcoding on 60 seawater samples col-lected from three depths (surface, 20 m and seafloor), across two research cruises (May and September 2018), encompassing the intra-annual range of the CF intensity. Communities above the thermocline of stratified frontal waters were clearly differen-tiated and less diverse than those below the thermocline and communities in the well- mixed waters of the Irish Sea. This effect was much more pronounced in September, when the CF was at its peak intensity. The stratified zone likely represents a stressful environment for bacterioplankton due to a combination of high temperatures and low nutrients, which fewer taxa can tolerate. Much of the observed variation was driven by Synechococcus spp. (cyanobacteria), which were more abundant within the strati-fied zone and are known to thrive in warm oligotrophic waters. Synechococcus spp. are key contributors to global primary productivity and carbon cycling and, as such, variability driven by the CF is likely to influence regional biogeochemical processes. However, further studies are required to explicitly link shifts in community structure to function and quantify their wider importance to pelagic ecosystems.

AB - Bacterioplankton underpin biogeochemical cycles and an improved understanding of the patterns and drivers of variability in their distribution is needed to determine their wider functioning and importance. Sharp environmental gradients and dispersal bar-riers associated with ocean fronts are emerging as key determinants of bacterioplank-ton biodiversity patterns. We examined how the development of the Celtic Sea Front (CF), a tidal mixing front on the Northwest European Shelf affects bacterioplankton communities. We performed 16S- rRNA metabarcoding on 60 seawater samples col-lected from three depths (surface, 20 m and seafloor), across two research cruises (May and September 2018), encompassing the intra-annual range of the CF intensity. Communities above the thermocline of stratified frontal waters were clearly differen-tiated and less diverse than those below the thermocline and communities in the well- mixed waters of the Irish Sea. This effect was much more pronounced in September, when the CF was at its peak intensity. The stratified zone likely represents a stressful environment for bacterioplankton due to a combination of high temperatures and low nutrients, which fewer taxa can tolerate. Much of the observed variation was driven by Synechococcus spp. (cyanobacteria), which were more abundant within the strati-fied zone and are known to thrive in warm oligotrophic waters. Synechococcus spp. are key contributors to global primary productivity and carbon cycling and, as such, variability driven by the CF is likely to influence regional biogeochemical processes. However, further studies are required to explicitly link shifts in community structure to function and quantify their wider importance to pelagic ecosystems.

KW - 16S sequencing

KW - Celtic sea front

KW - microbial biogeography

KW - micrfobiome

KW - Shallow sea front

U2 - 10.1111/mec.17097

DO - 10.1111/mec.17097

M3 - Article

VL - 32

SP - 4953

EP - 5210

JO - Molecular Ecology

JF - Molecular Ecology

SN - 0962-1083

IS - 18

ER -