Hopkinson, C., I. Buffam, J. Hobbie, J. Vallino, M. Perdue, B. Eversmeyer, F. Prahl, J. Covert, R. Hodson, M. A. Moran, E. Smith, J. Baross, B. Crump, S. Findlay, and K. Foreman. 1998. Terrestrial inputs of organic matter to coastal ecosystems: an intercomparison of chemical characteristics and bioavailability. Biogeochemistry, 43:211-234.
         Dissolved and particulate organic matter (DOM and POM) collected from rivers
    or groundwater feeding five estuaries along the east and west coasts of the
    USA were characterized with a variety of biogeochemical techniques and
    related to bioavailability to estuarine microbes. Surface water was sampled
    from the Columbia, Satilla, Susquehanna and Parker Rivers and groundwater
    was sampled from the Childs River. Several geochemical descriptors (percent
    organic matter of suspended particulate matter, C/N, lignin phenol content,
    ratio of vanillic acid to vanillin) suggested an ordering of the systems
    with respect to POM lability: Satilla < Parker < Columbia < Susquehanna. 
         DOC concentrations in these systems ranged from < 100 µM for the Columbia
    River to > 2000 µM for the Satilla River. Elemental analysis of DOM
    concentrates (> 1000 D) was used to predict organic matter composition and
    to calculate degree of substrate reduction using two different modeling
    approaches. Models predicted aliphatic carbon ranging between 43 and 60% and
    aromatic carbon between 26 and 36%, with aliphatic content lowest in the
    Satilla and highest in the Columbia River. The degree of substrate reduction
    of the organic matter concentrates followed a pattern similar to that for
    aliphatic C, being lowest in the Satilla (3.5) and highest in the Columbia
    (4.0). Extracellular enzyme activity varied broadly across the systems, but
    again ordered sites in the same way as did aliphatic content and degree of
    substrate reduction. Bacterial growth rates ranged from 1.3 µg
    mg-1d-1 DOC in the Satilla to 1.7 µg mg-1d-1 DOC in the Parker River. 
    Bioassays confirmed patterns of dissolved organic matter lability predicted 
    by the chemical models. Between 67% to 75% of the variation in bacterial growth 
    could be explained by differences in organic matter composition.