Predicting Epipelic Diatom Exopolymer Concentrations in Intertidal Sediments from Sediment Chlorophyll a

A bstractIn many intertidal cohesive—sediment habitats, epipelic diatoms are the dominant microphytobenthic organisms. In such sediments, concentrations of colloidal carbohydrate [including the exopolymeric substances (EPS) produced by diatoms during motility] are closely correlated with the biomass (chlorophyll a) of epipelic diatoms. A model describing this relationship (log (conc. coll. carbo. + 1) = 1.40 + 1.02(log (chl. a conc. + 1)) was derived from published data. It was validated against published and unpublished data from 6 different estuaries, and accounted for 64.6% of the variation in sediment colloidal carbohydrate concentrations. The model was valid for intertidal habitats with cohesive sediments where epipelic diatoms constituted >50% of the microphytobenthic assemblage. In sites with noncohesive sediments, or where the microphytobenthic assemblage was dominated by other algal groups, the model was not applicable. The mean percentage of EPS in colloidal carbohydrate extracts varied between 11 and 37% for axenic cultures of epipelic diatoms (with higher values obtained during stationary phase), and between 22.7% and 24.3% for natural sediments dominated by epipelic diatoms. Assuming an EPS percentage of 25% in colloidal extracts yielded an EPS chl. a ratio of 2.62:1. Maximum rates of EPS production in diatom cultures occurred at the beginning of stationary phase (1.6–5.09 μg EPS μg−1 chl a d−1), with Nitzschia sigma having a significantly (P < 0.05) higher rate of production than N. frustulum, Navicula perminuta and Surirella ovata. Similar rates of EPS production were measured in the field. The dynamics of EPS production and loss on mudflats is discussed, with reference to the model and these production rates.

[1]  S. Myklestad.  Production of carbohydrates by marine planktonic diatoms. I. Comparison of nine different species in culture , 1974 .

[2]  J. Pinckney,et al.  Effects of Tidal Stage and Sun Angles on Intertidal Benthic Microalgal Productivity , 1991 .

[3]  L. Meyer-Reil.  Microbial life in sedimentary biofilms the challenge to microbial ecologists , 1994 .

[4]  K. Sundbäck,et al.  Effects of Nutrient Enrichment on Microalgal Community Composition in a Coastal Shallow-water Sediment System: An Experimental Study , 1991 .

[5]  G. Underwood.  Microalgal Colonization in a Saltmarsh Restoration Scheme , 1997 .

[6]  J. Pinckney,et al.  Photophysiological responses of intertidal benthic microalgal communities to in situ light environments: Methodological considerations , 1993 .

[7]  R. Iturriaga,et al.  Heterotrophic Uptake and Transformation of Phytoplankton Extracellular Products , 1983 .

[8]  G. Underwood.  SEASONAL AND SPATIAL VARIATION IN EPIPELIC DIATOM ASSEMBLAGES IN THE SEVERN ESTUARY , 1994 .

[9]  G. E. Fogg.  The Ecological Significance of Extracellular Products of Phytoplankton Photosynthesis , 1983 .

[10]  A. Decho,et al.  Exopolymer microenvironments of microbial flora : multiple and interactive effects on trophic relationships , 1993 .

[11]  K. Sundbäck,et al.  The influence of benthic microalgae on the stability of a subtidal sediment , 1993 .

[12]  David M. Paterson,et al.  Short‐term changes in the erodibility of intertidal cohesive sediments related to the migratory behavior of epipelic diatoms , 1989 .

[13]  J. Grant,et al.  The interaction between benthic diatom films and sediment transport , 1986 .

[14]  A. Decho,et al.  Microbial exopolymer secretions in ocean environments: their role(s) in food webs and marine processes , 1990 .

[15]  David G. Mann,et al.  Diatoms: Biology and Morphology of the Genera , 1990 .

[16]  A. R. Nowell,et al.  Effects of bacterial exopolymer adhesion on the entrainment of sand , 1990 .

[17]  P. Montagna,et al.  The relationship between abundances of meiofauna and their suspected microbial food (diatoms and bacteria) , 1983 .

[18]  J. Eaton,et al.  THE ESTIMATION OF NUMBERS AND PIGMENT CONTENT IN EPIPELIC ALGAL POPULATIONS , 1966 .

[19]  David M. Paterson,et al.  Seasonal changes in diatom biomass, sediment stability and biogenic stabilization in the Severn Estuary , 1993, Journal of the Marine Biological Association of the United Kingdom.

[20]  C. Little,et al.  Subaerial exposure and changes in the stability of intertidal estuarine sediments , 1990 .

[21]  Gerardo M. E. Perillo,et al.  An ecological cascade effect: Migratory birds affect stability of intertidal sediments , 1993 .

[22]  K. Cooksey.  Extracellular Polymers in Biofilms , 1992 .

[23]  A. Haug,et al.  Studies on the phytoplankton ecology of the Trondheimsfjord. I. The chemical composition of phytoplankton populations , 1973 .

[24]  M. Gretz,et al.  DIATOM EXTRACELLULAR POLYMERIC SUBSTANCES: FUNCTION, FINE STRUCTURE, CHEMISTRY, AND PHYSIOLOGY , 1993 .

[25]  G. Underwood,et al.  The measurement of microbial carbohydrate exopolymers from intertidal sediments , 1995 .

[26]  S. Hay,et al.  THE SPEED OF DIATOM MIGRATION THROUGH NATURAL AND ARTIFICIAL SUBSTRATA , 1993 .

[27]  M. Pace,et al.  Bacterial production in fresh and saltwater ecosystems: a cross-system overview , 1988 .

[28]  I. Sundh.  Biochemical Composition of Dissolved Organic Carbon Derived from Phytoplankton and Used by Heterotrophic Bacteria , 1992, Applied and environmental microbiology.

[29]  I. Sutherland.  Biosynthesis and composition of gram-negative bacterial extracellular and wall polysaccharides. , 1985, Annual review of microbiology.

[30]  G. Underwood,et al.  Recovery of intertidal benthic diatoms after biocide treatment and associated sediment dynamics , 1993, Journal of the Marine Biological Association of the United Kingdom.

[31]  A. Decho,et al.  Bacterial exopolymer utilization by a harpacticoid copepod: A methodology and results , 1990 .

[32]  L. Cammen.  Effect of Particle Size on Organic Content and Microbial Abundance Within Four Marine Sediments , 1982 .

[33]  L. Cammen.  Annual bacterial production in relation to benthic microalgal production and sediment oxygen uptake in an intertidal sandflat and an intertidal mudflat , 1991 .

[34]  L. Melo,et al.  Biofilms--science and technology , 1992 .

[35]  H. Peletier.  Long-term changes in intertidal estuarine diatom assemblages related to reduced input of organic waste. , 1996 .

[36]  D. Paterson,et al.  Comparative structure, primary production and biogenic stabilization of cohesive and non-cohesive marine sediments inhabited by microphytobenthos , 1994 .

[37]  Giselher Gust,et al.  Prediction of coastal sediment stability from photopigment content of mats of purple sulphur bacteria , 1987, Nature.

[38]  A. Haug,et al.  Production of carbohydrates by the marine diatom Chaetoceros affinis var. willei (Gran) Hustedt. I. Effect of the concentration of nutrients in the culture medium , 1972 .

[39]  Chróst Rj.  Plankton photosynthesis, extracellular release and bacterial utilization of released dissolved organic carbon (RDOC) in lakes of different trophy. , 1983 .

[40]  L. Stal.  Physiological ecology of cyanobacteria in microbial mats and other communities. , 1995, The New phytologist.

[41]  L. Cammen,et al.  The relationship between bacteria and micro-algae in the sediment of a Bay of Fundy mudflat , 1986 .