Mass balancing the seasonal turnover of mud and sand in the vicinity of an intertidal mussel bank in the Wadden Sea (southern North Sea)
Bartholomä, A.; Flemming, B.W.; Delafontaine, M.T. (2000). Mass balancing the seasonal turnover of mud and sand in the vicinity of an intertidal mussel bank in the Wadden Sea (southern North Sea), in: Flemming, B.W. et al. (Ed.) Muddy coast dynamics and resource management. Proceedings in Marine Science, 2: pp. 85-106
In: Flemming, B.W.; Delafontaine, M.T.; Liebezeit, G. (Ed.) (2000). Muddy coast dynamics and resource management. Proceedings in Marine Science, 2. Elsevier: Amsterdam. ISBN 0-444-50464-8. 294 pp., more
In: Proceedings in Marine Science. Elsevier: New York. ISSN 1568-2692; e-ISSN 2352-2860, more
|  |
| Authors | | Top |
- Bartholomä, A.
- Flemming, B.W.
- Delafontaine, M.T.
|
|
|
| Abstract |
In a mixed Mytilus edulis/Lanice conchilega community on the Swinnplate sand flat behind Spiekeroog Island (southern North Sea), net seasonal fluxes of sand and mud were determined by combining measurements of topographic elevations, sediment bulk density, and mud contents for 7 to 8-month time intervals from March 1995 October 1996. These data were collected in a 0.7 km²-grid consisting of 90 sampling/measuring points at 100-m intervals. A concurrent census of M. edulis showed that mussel areal coverage varied between ca. 10 and 19% at the grid site at time, the lowest coverage having been recorded in the aftermath of a severe winter in 1995-1996 when an ice sheet strongly decimated the mussel banks and interspersed lawns of the cold-intolerant, tube-dwelling polychaete L. conchilega. When present, mussel beds occurred always in a SW to NE-oriented 'corridor' on the Swinnplate. Despite a general deepening (erosion) reaching 0.5 m in places over the severe winter (September 1995-April 1996; cf. negative volume budget of -170*10³ for the whole area), spatial patterns in mud enrichment showed a similar SW-NE constancy. These data suggest the preservation of mussel 'signatures' by burial. Under more benign weather conditions after the ice winter, erosion continued in large areas of the grid (cf. volume budget of -78*10³ m³ in the period April-October 1996). This can at least in part be explained by a strong impairment of the stabilising effect of the L. conchilega tube lawns at the time. Sediment mass budgets were negative for the severe winter as well as for the summer thereafter (-196*10³, and -97*10³ tonnes dry sediment, respectively). Over the preceding summer (March-September 1995), in contrast, positive volume and sediment mass budgets (86*10³ m³ and 99*10³ tonnes dry sediment, respectively) were documented, accompanied by net increases of up to 0.3 m in elevation. At all times, net fluxes in mud mass did not exceed ca. 12% of the total sediment budgets. In addition, mud contents generally did not exceed ca. 20%. Even under the calmer hydrodynamic conditions reigning in summer, the reworking of sandy sediments evidently results in much higher fluctuations in elevation, and involves much larger material fluxes than is commonly assumed, both in tidal-flat sedimentology and ecology. |
|
