Recent Biocoenoses and Ichnocoenoses in Shallow-Water Marine Environments

Interrelated biocoenoses, ichnocoenoses, and ichnofacies in different shallow-marine environments are discernible, based on the relations between environmental conditions and macro-benthic organisms; these are very important ecologically and ichnologically.

The first part of this chapter (Biological Aspects) is devoted to the most important ecological parameters influencing animal life in these environments, and to the main trends in faunal distribution. Comparisons of the distribution, abundance, and zonation of macrobenthic animals between the area above the high-water line and shallow shelf of the North Sea (German Bight), Mediterranean Sea (Gulf of Gaeta), and Georgia coastal region (Sapelo Island), reveal the following general trends: (1) supralittoral: very few terrestrial and marine species, relatively few individuals; (2) eulittoral: few marine species, although some are represented by numerous individuals; (3) upper sublittoral: slightly more marine species, very few individuals; (4) middle sublittoral: numerous species and numerous individuals; and (5) lower sublittoral: fewer numbers of species and individuals. Certain “parallel” communities (iso-communities) were also observed in the three areas investigated.

The second part of this chapter (Ichnological Aspects) is concerned with the distribution, abundance, and zonation of lebensspuren. The total number of lebensspuren depends mainly on the numbers of trace-making species and individuals occurring in each environment. The greatest abundances of animals and traces are observed in the subtropical coastal region of Georgia, the lowest abundances in the temperate- boreal North Sea.

Rates of sedimentation and sediment re-working are important in determining the actual preservability of the lebensspuren. For example, traces are much less likely to be preserved in the high-energy conditions of the upper sublittoral zone than in the quieter conditions of the middle or lower sublittoral.

In most of the environments studied, characteristic lebensspuren provide a conspicuous ichnofacies. Such ichnofacies are mainly dependent on the preservability of certain traces as characteristic lebensspuren, under proper conditions. Therefore, to compare or correlate ichnofacies occurring in corresponding environmental zones of different geographical regions is difficult. A comparison of similarly constructed lebensspuren from different regions, however, leads to the distinction of types of lebensspuren that reflect ecological conditions or animal adaptations, mainly the trophic relationships of the trace-producing organisms. Such lebensspuren show a distinct zonation in a generalized beach-offshore profile.