120
5 Spallal and Temporal Dl,lllhulI()1l Patterns
meiofauna and microorganisms, which are associated with faeces and pseudofaeces (Rhoads 1974).
In the sandtlat, the macrofauna causes modifications of the sediment structure
by its bioturbating activity and influences the concentration and mineralization of
the organic matter (Anderson & Kristensen 1988). Bioturbation causes modifications of the physico-chemical sediment characteristics and may increase the metabolic activity of microorganisms (Yingst & Rhoads 1980).
The micro-topography of the redox-potential discontinuity (RPD-Iayer) in the
sediments is changed by bioturbation- and ventilation-activities of the macrofauna.
Without bioturbation, oxic mineralization of the organic matter is restricted to the
sediment surface and the RPD-Iayer. Bioturbation causes a partial mixing of the
sediment, which leads to relatively homogeneous depth profiles of microbial activities and bacterial cell numbers as well as of density gradients of particulate
organic matter and nutrients. Thus, in sandtlats the mineralization of the organic
matter is not limited to the sediment surface, but also expanded to deeper zones of
the sediment.
This chapter summarizes the studies carried out in ELA W AT by Kroncke,
Bergfeld and colleagues. Detailed specifications of the geochemical reactions on
the transect are given in Sect. 5.2.1.
5.2.2.2
Material and Methods
The macrozoobenthos was sampled in 2-monthly intervals at 6 different sites along
a transect on the Swinnplate from May to November 1994, from March to December 1995 and March to September 1996 (Kroncke 1996 and unpublished;
Chap. 3.1, 3.6). Eight replicate samples were taken per site with a corer (5 cm
diameter, approx. 20 cm sediment depth) in an area of 0.25 m
2 • The samples were
sieved over 0.5 mm mesh size and fixed in 4 % buffered kohrsolin solution. The
individuals were counted in the laboratory and determined to species level. For the
determination of the macrofaunal biomass, the samples were dried for 24 h at
80 DC and combusted for 6 hat 480°C. The biomass was expressed as mg ash-free
dry weight (afdw) per 20 cm 2
5.2.2.3
Results
The study area in the backbarrier system of Spiekeroog Island was characterized
by extremely varying individual numbers (abundances) and a strongly tluctuating
diversity of the macrofauna over the years (Bergfeld 1996). His survey of the
whole Swinnplate yielded 70 different taxa of macrofauna, whereas only
43 different taxa were recorded at the transect sites. Polychaetes were the dominant group of organisms in terms of species. The typical sandflat community of
macrofauna changed in composition under the influence of the biodeposits produced by the mussels (Kroncke 1996).
The sandflat was characterized by a poorly structured surface sediment and a
high sediment mobility and bioturbation-activity. The macrofauna community was
dominated by the polychaete Arenicola marina. Additionally, Scolop/os armiger,
5 Spallal and Temporal Dl,lllhulI()1l Patterns
meiofauna and microorganisms, which are associated with faeces and pseudofaeces (Rhoads 1974).
In the sandtlat, the macrofauna causes modifications of the sediment structure
by its bioturbating activity and influences the concentration and mineralization of
the organic matter (Anderson & Kristensen 1988). Bioturbation causes modifications of the physico-chemical sediment characteristics and may increase the metabolic activity of microorganisms (Yingst & Rhoads 1980).
The micro-topography of the redox-potential discontinuity (RPD-Iayer) in the
sediments is changed by bioturbation- and ventilation-activities of the macrofauna.
Without bioturbation, oxic mineralization of the organic matter is restricted to the
sediment surface and the RPD-Iayer. Bioturbation causes a partial mixing of the
sediment, which leads to relatively homogeneous depth profiles of microbial activities and bacterial cell numbers as well as of density gradients of particulate
organic matter and nutrients. Thus, in sandtlats the mineralization of the organic
matter is not limited to the sediment surface, but also expanded to deeper zones of
the sediment.
This chapter summarizes the studies carried out in ELA W AT by Kroncke,
Bergfeld and colleagues. Detailed specifications of the geochemical reactions on
the transect are given in Sect. 5.2.1.
5.2.2.2
Material and Methods
The macrozoobenthos was sampled in 2-monthly intervals at 6 different sites along
a transect on the Swinnplate from May to November 1994, from March to December 1995 and March to September 1996 (Kroncke 1996 and unpublished;
Chap. 3.1, 3.6). Eight replicate samples were taken per site with a corer (5 cm
diameter, approx. 20 cm sediment depth) in an area of 0.25 m
2 • The samples were
sieved over 0.5 mm mesh size and fixed in 4 % buffered kohrsolin solution. The
individuals were counted in the laboratory and determined to species level. For the
determination of the macrofaunal biomass, the samples were dried for 24 h at
80 DC and combusted for 6 hat 480°C. The biomass was expressed as mg ash-free
dry weight (afdw) per 20 cm 2
5.2.2.3
Results
The study area in the backbarrier system of Spiekeroog Island was characterized
by extremely varying individual numbers (abundances) and a strongly tluctuating
diversity of the macrofauna over the years (Bergfeld 1996). His survey of the
whole Swinnplate yielded 70 different taxa of macrofauna, whereas only
43 different taxa were recorded at the transect sites. Polychaetes were the dominant group of organisms in terms of species. The typical sandflat community of
macrofauna changed in composition under the influence of the biodeposits produced by the mussels (Kroncke 1996).
The sandflat was characterized by a poorly structured surface sediment and a
high sediment mobility and bioturbation-activity. The macrofauna community was
dominated by the polychaete Arenicola marina. Additionally, Scolop/os armiger,