Ecosystem Analysis - Energy flow
Energy flow: Trophic structure and energy flow in an intertidal ecosystem, the Sylt-Rømø Bay
The energy flow in intertidal areas is expected to be high due to the proximity of sediment and water, the good supply of light and the tidal currents. This leads to a close coupling not only between pelagic and benthic processes, but also between landward and seaward areas of the coastal zone and to a distinct distribution of primary and secondary producers. The Sylt-Rømø Bay (Wadden Sea, North Sea of Germany/Denmark) is a semienclosed basin between the mainland and the two islands Sylt and Rømø which are connected with the mainland by dams. There is only one deep tidal gully to the North Sea between the two islands. Therefore this is a preferred area for studies of ecosystem processes. The internal cycling of material, the productivity and the trophic transfer between dominant links in the food web is investigated. The entire area of the Sylt-Rømø Bay is 406 km² large including 135 km² of tidal flats. The main part of the intertidal area is occupied by Arenicola sand flats (67%). Muddy sands form only 10% and different areas of sand and mud constitute ca. 11%. Mussel beds cover actually less than 1%. Comparably large seagrass beds of Zostera noltii and Z. marina extend over 12% of the intertidal area. In these different benthic communities the food web is investigated considering primary production, import of detritus, biomass, production and consumption of macrofauna. The consumption by birds has been estimated. An actual focus lies on the measurement of the consumption by mobile epibenthic predators as prawns fishes.
Primary production is dominated by microphytobenthos. The total primary food supply is about 626 gC m-2 a-1 comprising also the production of seagrasses, phytoplankton and detritus import. A large amount is utilised by microbial processes. The total consumption by intertidal macrofauna is estimated to 98 gC m-2 a-1, somatic growth and gonad production to 54 gC m-2 a-1. From this amount 5g are used by carnivorous birds and invertebrate predators each. Only 0.3 gC m-2 a-1 are utilised by fishes.
Selected Publications
Asmus H (1994) Benthic grazers and suspension feeders: which one assumes the energetic dominance in Königshafen? Helgoländer Meeresunters. 48:217-231
Asmus H, Asmus R (1985) The importance of grazing food chain for energy flow and production in three intertidal sand bottom communities of the northern Wadden Sea. Helgoländer Meeresunters. 39:273-301
Sprung M, Asmus H (1995) Does the energy equivalence rule apply to intertidal macobenthic communities? Neth. J. aquat. Ecol. 29:369-376
Sprung M, Asmus H, Asmus R (2001) Energy Flow in Benthic Assemblages of Tidal Basins: Ria Formosa (Portugal) and Sylt-Römö Bay (North Sea) Compared. In: Reise K (ed) Ecological Comparisons of Sedimentary Shores. Springer, Berlin, Heidelberg, 237- 254
Asmus H, Lackschewitz D, Asmus R, Scheiffarth G, Nehls G, Herrmann J-P (1998) Transporte im Nahrungsnetz eulitoraler Wattflächen der Sylt-Rømø Bucht. In: C. Gätje, K. Reise (eds) Ökosystem Wattenmeer, Austausch, Transport- und Stoffumwandlungsprozesse. Springer Verlag, Berlin, p 393-420
