Marine Biofilms: Part IMarine Biofilms: Part IIntertidal

OEST 740033108033108

Outline

IntroductionEffects/Implications of biofilms to sediment propertiesFormation of StromatolitesBiofilms as a Refuge for pathogensRole in metal contaminationBiofilms as food sourceBiofilms as food source Conclusion/Summary

IntroductionIntertidal

Highly dynamic systemPeriodic fluctuations in environmental parametersMicrobial processes critical to remineralization of nutrients and primary production

BiofilmsBiofilmsProvide a protective and stable microenvironment against fluctuating conditionsmicroenvironment against fluctuating conditions

Thus, it is important to understand small-scale influences of biofilms to fully understand larger-influences of biofilms to fully understand largerscale processes within intertidal systems

Biofilms in the intertidal

The high density of cells in sedimentsThe high density of cells in sediments increases potential quorum sensing activity

Facilitate more efficient utilization andFacilitate more efficient utilization and biotransformation of carbon and other nutrients, waste removal and more effective resiliency to environmental stressors

Localization of extracellular enzymes yImportant in efficiencies of larger-scale transformations of OM by bacteria

Conversion of DOC to POC

Biofilms in the intertidal

Biofilm EPS forms cohesive matrix surrounding particles in intertidal sedimentsImportant consequences for sediment propertiesp p

Biofilms in intertidal

Diatoms and cyanobacteria canDiatoms and cyanobacteria can be large contributors to biofilms in intertidal sedimentste t da sed e ts

EPS in sedimentsEPS in sediments

Donan Trap – sequestering andDonan Trap sequestering and concentrating ions (e.g. Ca 2+)Form hydrated gel protects againstForm hydrated gel – protects against desiccationUV i di i l l iUV irradiation can alter polymer matrix –acts as ‘pliant matrix’ responding to

i l di ienvironmental conditions

Roles in sediment stabilityy

Tolhurst et al. 2003

Biofilm effects on sediment tiproperties

“biofilm gel effect”biofilm gel effect

Decho et al. 2003

Biofilm effects on sediment tiproperties

Decho et al. 2003

Biofilm effects on sediment properties

“Biofilm gel effect”Biofilm gel effectEPS-sediment traps photons more effectivelyEnhances forward scatteringEnhances forward scatteringIncreases porosity

I li tiImplicationsDown-welling photons can penetrate deeperPhotosynthesis can occur at greater depthsReduces shading effects and increases ability of surface-associated and densely packed cells to acquire solar energy

Intertidal StromatolitesLayered sediment macrostructures formed through interactions offormed through interactions of biological organismsExample of extreme biologicalExample of extreme biological mediated sediment stabilizationEPS binds Ca2+ and inhibits S b ds C d b sgeochemical precipitation of CaCO3

Partial degradation of EPSgby SRB leads to restricted CaCO3 precipitationCaCO3 precipitation

Refuge of pathogens

Pathogenic bacteria enter intertidal systems g yfrom terrestrial and freshwater sourcesSurvival is linked to association withSurvival is linked to association with aggregated flocsWhen freshwater meets saline water:When freshwater meets saline water: increase in cations and enhanced floc formation and aggregation of suspendedformation and aggregation of suspended DOC, silts, and clays

EPS acts as protective refuge and buffers cellsEPS acts as protective refuge and buffers cells against potential stresses

Concentration of contaminationConcentration of contamination

EPS can bind and concentrate a range ofEPS can bind and concentrate a range of metal ionsMicrobial EPS range of pyruvate ketalsMicrobial EPS – range of pyruvate ketals uronic acids, phosphate groups

I i bi di itIonic binding capacityCd2+, Cu2+, Cr3+, Pb2+, etc. are efficiently chelated by EPSPotential increased by UV exposure

Biofilm as food sourceBiofilm as food source

Biofilm as food sourceBiofilm as food source

Grazing as a control of biofilm abundance

Trophic transfer

Association of metal-Association of metal-EPS may significantly enhancesignificantly enhance bioavailability of metals in marinemetals in marine systems

SummaryThe presence of a biofilm matrix alters a number of physical and biological properties of intertidal sedimentphysical and biological properties of intertidal sediment environments.Biofilms occurring within the intertidal also influence human health providing a refuge for human pathogens and providing a pathway for trophic transfer of metal contaminates.However, the overall contribution of intertidal biofilms to larger-scale ocean processes remains largely unknown. In order to fully understand larger-scale processes within intertidal systems it is important to understand the small-scale contributions of biofilms.scale contributions of biofilms.