TY - JOUR
T1 - The role of benthic biofilm production in the mediation of silicon cycling in the Severn Estuary, UK
AU - Welsby, H. J.
AU - Hendry, K. R.
PY - 2016/7/5
Y1 - 2016/7/5
N2 - The biological mediation of benthic biogenic silica (BBSi) by the diatom-dominated biofilms on the intertidal mudflats of the Severn Estuary (UK) was assessed in situ under different environmental conditions using measurements of productive biomass (chlorophyll a), photosynthetic activity of undisturbed microalgal assemblages, benthic biogenic silica (BBSi) and benthic dissolved silica (BDSi). We show low BBSi standing stocks in the mudflats compared to other European estuaries, under both warmer summer conditions (0.6%) and colder winter conditions (0.5%). Dissolved forms of Si (BDSi) dominated the estuary, with significantly higher concentrations during the sampled winter (22.6 ± 1.0 mg L-1) compared to the sampled summer (2.9 ± 0.5 mg L-1). Benthic algal biomass was higher under cold conditions compared to warmer conditions (24.0 ± 2.3 and 13.2 ± 1.9 mg g-1 sed. dw., respectively), following reduced migratory behaviour in the winter increasing surficial biomass. Relative maximum Electron Transport Rate (rETRmax), used as a proxy for relative primary productivity, was higher under warm conditions (254.1 ± 20.1 rel. units) compared to cold conditions (116.0 ± 27.1 rel. units). The biofilms sampled in the summer biologically mediated Si by the productive, high light acclimated diatoms that were highly motile during fluorescence measurements, and exhibited migratory behaviour, which despite nutrient limitation, evidenced by low Fv/Fm, increased the accumulation of BBSi. The biofilms sampled in the winter that were subject to relatively colder temperatures, consisted of low light acclimated diatoms of reduced migratory capabilities, and induced NPQ that suppressed productivity, and mediated BBSi to a lesser extent. Environmental stresses reduced the biofilm biological mediation of Si, which controlled Si to a lesser extent compared to the high hydrodynamic energy increasing biofilm re-suspension and terrestrial/coastal inputs.
AB - The biological mediation of benthic biogenic silica (BBSi) by the diatom-dominated biofilms on the intertidal mudflats of the Severn Estuary (UK) was assessed in situ under different environmental conditions using measurements of productive biomass (chlorophyll a), photosynthetic activity of undisturbed microalgal assemblages, benthic biogenic silica (BBSi) and benthic dissolved silica (BDSi). We show low BBSi standing stocks in the mudflats compared to other European estuaries, under both warmer summer conditions (0.6%) and colder winter conditions (0.5%). Dissolved forms of Si (BDSi) dominated the estuary, with significantly higher concentrations during the sampled winter (22.6 ± 1.0 mg L-1) compared to the sampled summer (2.9 ± 0.5 mg L-1). Benthic algal biomass was higher under cold conditions compared to warmer conditions (24.0 ± 2.3 and 13.2 ± 1.9 mg g-1 sed. dw., respectively), following reduced migratory behaviour in the winter increasing surficial biomass. Relative maximum Electron Transport Rate (rETRmax), used as a proxy for relative primary productivity, was higher under warm conditions (254.1 ± 20.1 rel. units) compared to cold conditions (116.0 ± 27.1 rel. units). The biofilms sampled in the summer biologically mediated Si by the productive, high light acclimated diatoms that were highly motile during fluorescence measurements, and exhibited migratory behaviour, which despite nutrient limitation, evidenced by low Fv/Fm, increased the accumulation of BBSi. The biofilms sampled in the winter that were subject to relatively colder temperatures, consisted of low light acclimated diatoms of reduced migratory capabilities, and induced NPQ that suppressed productivity, and mediated BBSi to a lesser extent. Environmental stresses reduced the biofilm biological mediation of Si, which controlled Si to a lesser extent compared to the high hydrodynamic energy increasing biofilm re-suspension and terrestrial/coastal inputs.
KW - Biogenic silica
KW - benthic
KW - biomass
KW - primary productivity
KW - downregulation
UR - http://www.scopus.com/inward/record.url?scp=84966622089&partnerID=8YFLogxK
U2 - 10.1016/j.ecss.2016.04.008
DO - 10.1016/j.ecss.2016.04.008
M3 - Article (Academic Journal)
AN - SCOPUS:84966622089
SN - 0272-7714
VL - 176
SP - 124
EP - 134
JO - Estuarine, Coastal and Shelf Science
JF - Estuarine, Coastal and Shelf Science
ER -