11 Energy Flow in Benthic Assemblages of Tidal
Basins: Ria Formosa (Portugal) and Sylt-R0m0 Bay
(North Sea) Compared
M. SPRUNG, H. ASMUS, and R. ASMUS
11.1 Introduction
Tidal areas are zones of steep physical and biologically determined gradients.
Gradients develop vertically in sediment profiles, horizontally along intertidal
transects, temporally with respect to temperature, oxygen, nutrients, light
with diurnal, tidal and seasonal periods. It is a special feature of tidal systems
that these gradients reveal a high small-scale variability in space and time
caused primarily by the hydrodynamics. The energy flow in intertidal areas
should be high due to the proximity of sea bottom and surface water, the
concomitant good supply of light, and the tidal flow. This leads to a close
spatial coupling not only between water column and sea bottom processes,
but also between the landward and seaward parts of the coastal system and to
a distinct distribution of primary and secondary producers (J0rgensen 1983;
Reise 1985; Kjerfve 1994b).
In temperate zones, main primary producers are salt marsh plants at the
upper fringe, seagrasses in intertidal and subtidal areas, opportunistic green
algae and some tolerant brown and red algae, unicellular or filamentous
micro algae on the sediment surface or on biogenic structures, and phytoplankton. Phytoplankton abundance and production is driven by three important processes: remineralization of nutrients, nutrient input by river runoff and the grazing activity of zooplankton and suspension feeders at the
bottom; the latter having its largest impact in shallow waters (Dame 1993).
Import of particulate organic carbon from the sea may be important as well.
It is due to this source that coastal systems tend to be overall heterotrophic,
i.e. degradative processes frequently outbalance primary production (Smith
and Hollibough 1993; Heip et al. 1995).
The abundance and composition of different primary producers should
condition to a large extent the quality and quantity of the macrofauna and
hence energy flow through the system in addition to physical factors. However, next to the food availability, the macrofauna is also subject to predation.
Ecological Studies, Vol. 151
K. Reise (ed.) Ecological Comparisons
of Sedimentary Shores
© Springer-Verlag Berlin Heidelberg 2001
Basins: Ria Formosa (Portugal) and Sylt-R0m0 Bay
(North Sea) Compared
M. SPRUNG, H. ASMUS, and R. ASMUS
11.1 Introduction
Tidal areas are zones of steep physical and biologically determined gradients.
Gradients develop vertically in sediment profiles, horizontally along intertidal
transects, temporally with respect to temperature, oxygen, nutrients, light
with diurnal, tidal and seasonal periods. It is a special feature of tidal systems
that these gradients reveal a high small-scale variability in space and time
caused primarily by the hydrodynamics. The energy flow in intertidal areas
should be high due to the proximity of sea bottom and surface water, the
concomitant good supply of light, and the tidal flow. This leads to a close
spatial coupling not only between water column and sea bottom processes,
but also between the landward and seaward parts of the coastal system and to
a distinct distribution of primary and secondary producers (J0rgensen 1983;
Reise 1985; Kjerfve 1994b).
In temperate zones, main primary producers are salt marsh plants at the
upper fringe, seagrasses in intertidal and subtidal areas, opportunistic green
algae and some tolerant brown and red algae, unicellular or filamentous
micro algae on the sediment surface or on biogenic structures, and phytoplankton. Phytoplankton abundance and production is driven by three important processes: remineralization of nutrients, nutrient input by river runoff and the grazing activity of zooplankton and suspension feeders at the
bottom; the latter having its largest impact in shallow waters (Dame 1993).
Import of particulate organic carbon from the sea may be important as well.
It is due to this source that coastal systems tend to be overall heterotrophic,
i.e. degradative processes frequently outbalance primary production (Smith
and Hollibough 1993; Heip et al. 1995).
The abundance and composition of different primary producers should
condition to a large extent the quality and quantity of the macrofauna and
hence energy flow through the system in addition to physical factors. However, next to the food availability, the macrofauna is also subject to predation.
Ecological Studies, Vol. 151
K. Reise (ed.) Ecological Comparisons
of Sedimentary Shores
© Springer-Verlag Berlin Heidelberg 2001