Selected Publications

Abstract:   In the tidal flats of Mellum Island (southern North Sea), biofilms and microbial
mats, generated largely by cyanobacteria, colonize the sedimentary surfaces.
Biostabilization effects and biomass enrichment influence erosional and
depositional dynamics resulting from tidal flushing and storm surges. The
overlapping of both biological and physical forces causes the development of
characteristic sedimentary structures. To obtain a quantitative expression of
the degree of effectiveness of microbial colonization in the formation of
structures in an extended tidal area, a modification index (MOD-I) was
developed based on the hllowing values: (i) the proportion of mat-covered area
related to a defined investigation area (IA); (ii) the degree of steepness of slope
angles of raised erosional remnants (Is); and (iii) the degree of microbial
levelling of a rippled sedimentary surface (IN). The MOD-I was calculated for
several defined regions within the stucly area, and both winter and summer
situations were considered. The MOD-I values show, first, that the lower
intertidal zone is characterized by index values approaching zero. This implies
that microbially induced effects in this zone are negligible, even in summer.
Second, the upper intertidal zone is characterized by lower index values in
winter and relatively high values in summer. This implies a predominantly
seasonal control on the biofilm development in this zone. Third, in the lower
supratidal zone, the index values are almost identical during both winter and
summer. This implies non-seasonal biological effects in this zone. Concomitant
empirical studies on the composition of microbial mats and films suggest that
the dominant microbial type influences the MOD-I value.

Keywords:   Noffke, Benthic cyanobacteria, microbially induced sedimentary
structures, quantification of microbial influence, Recent, siliciclastic tidal flats

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