1012 c. Chemical Oceanography OLR (1985)32 (12)

which greatly extends their known geological time range and increases their potential as molecular markers for algal input. Organic Chem. Unit, Univ. of Bristol, Cantock's Close, Bristol BS8 ITS, UK.

85:7038 Olson, D.L. and M.S. Shuman, 1985. C o l ~ r dis-

sociation from estuarine humic materials. Geochim. cosmochim. A cta, 49(6): 137 I- 1375.

The apparent dissociation rate constants were distributed over a wide range, with most bound CU(II) having k > l sec t (t<0.7 sec). Nearly all variation in the kinetic distribution was among size fractions; as size fraction decreased, the distribution of bound CU(II) shifted to larger rate constants. Location of sampling stations had little effect on results. Dept. of Chem., Univ. of North Carolina, Chapel Hill, NC 27514, USA.

85:7039 Pelet, R., 1984. A model for the biological degradation

of recent sedimentary organic matter. Org. Geochem., 6:317-325.

Biological degradation in a given environment is modelled as the sum of numerous elementary reactions. Comparisons of actual trends vs numerical simulations show that sulfate reduction is dominated by rapid reactions, but total organic matter decay is dominated by slow reactions, compatible with geologic times. Thus bacteria can be geologically significant. Both sulfate reduction and microbio- logical degradation of total organic matter appear as processes of moderate efficiency. The high efficiency of biological degradation in oxic sediments relies on benthic activity at the boundary layer and in the bioturbated zone. Inst. Francais du Petrole, 1-4 Ave. de Bois-Preau, 92506 Ruel-Malmaison, France.

85:7040 Requejo, A.G. and J.G. Quinn, 1985. C~s and C30

biogeaic aikenes in sediments and detritus of a New England salt marsh. Estuar. coast. Shelf Sci., 20(3):281-297.

Four acyclic C25 dienes and trienes and a C30 bicyclic dien¢ were the most abundant biogenic alkenes detected. The alkenes resembled those reported for other anoxic environments although the organic matter sources were significantly different in the various studies, suggesting a formation process common to anoxic environments. The exact source of the alkenes remains unknown but some exper- imental results suggest that anaerobic bacteria mediate alkene production. Battelle New England Mar. Res. Lab., 397 Washington St., Duxbury, MA 02332, USA. (msg)

85:7041 Risatti, J.B., S.J. Rowland, D.A. Yon and J.R.

Maxwell, 1984. Stereodmmieal studies of acyclic isoprenoids. Xll. Lipids of methanogenic bacteria and Imssible eontfllmtions to sediments. Org. Geochem., 6:93-104.

Stereochemistry suggests that the alkane and squalane in marine sediments may derive from methanogens; in contrast, the stereochemistry of pristane in Methanobacterium thermoautotrophicum indicates a fossil fuel contaminant origin, suggesting that this and certain other alkanes reported in archaebacteria might also be of contaminant origin. There is, therefore, little evidence at present that the pristane in immature marine sediments originates in methanogens. The Ct5 and C20 saturated alcohols in M. thermoautotrophicum have mainly the alt-R configuration. If this is generally true for methano- gens, the C20 alcohol in the Messel shale may originate mainly from methanogens, whereas that in the Green River shale may originate mainly from photosynthetic organisms. Sect. of Analyt. Chem., Illinois State Geol. Surv., 615 East Peabody Drive, Champaign, IL 61820, USA.

85:7042 Shaw, P.M. and R.B. Johns, 1985. Organic geo-

chemistry studies of a recent inner Great Barrier Reef sediment. I. Assessment of input sources. Org. Geochem., 8(2):147-156. Dept. of Organic Chem., Univ. of Melbourne, Parkville. Vict. 3052, Australia.

85:7043 Taylor, J., C. Young, R.J. Parkes, T. Eglinton and

A.G. Douglas, 1984. Structural relatioushil~ in protokerogens and other geopo!ymers from oxie and anoxic sediments [Cat Firth, Scotlandl. Org. Geochem., 6:279-286.

The humic acids and protokerogens taken together constituted the major fraction of the organic matter (60-65%) in both the surface (0-2 cm) oxic and deeper (16-21 cm) anoxic sediment. While the extractable bitumen comprised only 4-5% of the organic matter, in both sediment horizons, it con- tained 58-70% of the saponifiable lipids. The lipid fraction produced by saponification of the pro- tokerogen, although small, increased significantly with increasing depth. The humic acids appeared to contain a relatively higher contribution for autoch- thonous organic matter than any other fraction isolated from these sediments. Lipid components associated with the various bound fractions ap- peared more protected from microbial alteration than those of the extractable bitumens. Scottish Mar.