TY - JOUR

T1 - Meteorological conditions induce strong shifts in mixotrophic and heterotrophic flagellate bacterivory over small spatio-temporal scales

AU - Anderson, Ruth

AU - Hansen, Per Juel

PY - 2020

Y1 - 2020

N2 - Mixotrophic bacterivory by small phytoflagellates (SP) can equal that of heterotrophic flagellates (HF) in marine euphotic waters. Due to their differing nutritional requirements from prey, SP and HF bacterivory are thought to differentially impact nutrient and carbon cycling through microbial food webs. However, little is known on how the relative dominance of SP and HF feeding shifts along environmental gradients, especially over short spatio‐temporal scales. Here, SP and HF bacterivory rates were compared over 5 d at three depths in the upper water column of a dynamic coastal zone, through the use of surrogate prey. SP and HF bacterivory strongly fluctuated over both spatial (< 5 m) and temporal (day to day) scales despite relatively stable abundance, with a respective seven‐ and ten‐fold difference between minimum and maximum bacterivory rates. Irradiance regulated SP community bacterivory, leading to a grouping into high rates under light limitation, mid‐level rates under optimal irradiance levels for growth and low rates at very high irradiance levels. SP bacterivory only dominated over that of HF at irradiance ranges generally considered optimal for photosynthetic growth (∼ 40–300 μmol photons m−2 s−1). SP bacterivory, but not that of HF, was positively correlated to total bacterial abundance, with HF potentially selectively targeting actively growing bacteria. Overall, the present study indicates that meteorological conditions affecting irradiance levels could strongly impact microbial food web dynamics and the cycling of carbon and nutrients through coastal marine systems.

AB - Mixotrophic bacterivory by small phytoflagellates (SP) can equal that of heterotrophic flagellates (HF) in marine euphotic waters. Due to their differing nutritional requirements from prey, SP and HF bacterivory are thought to differentially impact nutrient and carbon cycling through microbial food webs. However, little is known on how the relative dominance of SP and HF feeding shifts along environmental gradients, especially over short spatio‐temporal scales. Here, SP and HF bacterivory rates were compared over 5 d at three depths in the upper water column of a dynamic coastal zone, through the use of surrogate prey. SP and HF bacterivory strongly fluctuated over both spatial (< 5 m) and temporal (day to day) scales despite relatively stable abundance, with a respective seven‐ and ten‐fold difference between minimum and maximum bacterivory rates. Irradiance regulated SP community bacterivory, leading to a grouping into high rates under light limitation, mid‐level rates under optimal irradiance levels for growth and low rates at very high irradiance levels. SP bacterivory only dominated over that of HF at irradiance ranges generally considered optimal for photosynthetic growth (∼ 40–300 μmol photons m−2 s−1). SP bacterivory, but not that of HF, was positively correlated to total bacterial abundance, with HF potentially selectively targeting actively growing bacteria. Overall, the present study indicates that meteorological conditions affecting irradiance levels could strongly impact microbial food web dynamics and the cycling of carbon and nutrients through coastal marine systems.

U2 - 10.1002/lno.11381

DO - 10.1002/lno.11381

M3 - Journal article

VL - 65

SP - 1189

EP - 1199

JO - Limnology and Oceanography

JF - Limnology and Oceanography

SN - 0024-3590

IS - 6

ER -