Biodeposition in a juvenile mussel bed of the east Frisian Wadden Sea (Southern North Sea)

Abstract

Seasonal trends of biodeposition and animal coverage in backbarrier beds of the mussel Mytilus edulis in the East Frisian Wadden Sea were documented and quantified to assess the effects of physical disturbance by storms and to develop a conceptual model for the interpretation of biodeposits in the stratigraphic record. Accretion and erosion of biogenic muds (faeces and pseudofaeces) were quantified by repeated precision levelling of a 12 m 2 test area. Animal coverage was documented by vertical photography prior to each levelling survey. Levelling and photography were conducted from a bridge and rail system to avoid physical disturbance by trampling. Four surveys, covering a period of different weather conditions, showed variable mean accretion/erosion rates of biodeposits ranging from +0.56 mmd -1 (accretion) to -1.34 mm d -1 (erosion) and areal coverage of mussels ranging from 39.1% to 0%. A pronounced seasonal trend in the biodepositional pattern was observed. Mean accretion rates were high (>0.5 mmd -1) during the summer season, whereas in the winter season net deposition decreased to zero or showed erosional trends. Longterm sediment budgets are thus composed of highly variable mean annual rates which, in turn, comprise highly variable seasonal and even monthly rates, depending on the local weather pattern. This forms the basis for a conceptual model, in terms of which the stratigraphic record of fossil biodeposits can be meaningfully interpreted.

Population dynamics and secondary production of the cockle Cerastoderma edule (L.) in a backbarrier tidal flat in the Wadden Sea

“…Hertweck and Liebezeit (1996) commented that between 1991 and 1993 the accumulation of biodepositional fine-grained material in a mussel bed in Neuharlingersieler Nacken began in June 1992, ten months after colonisation by mussels; and a mud layer of 2 cm thickness under the live mussels was clearly recognisable in December 1992. For this region, Flemming and Delafontaine (1994) reported one of the highest biodeposition rates of Mytilus edulis. After summer 1994, an increase in the mud content at Station 4 was observed, which was quantified from March to September 1995 (Table 1).…”

“…Heavy fluctuations of the populations as a result of high variability in both success of spatfall and subsequent survival have been related to environmental factors. Physical conditions like sediment quality (Ducrotoy and Desprez, 1986) and dynamics (Bouma et al, 2001), severe winters (Beukema, 1979, Strasser, 2000, storm-generated waves (Nehls and Thiel, 1993) and high levels of silt and biodeposits (Flemming and Delafontaine, 1994) are important factors controlling the development of the bivalve populations on these tidal flat areas, although biological factors like predation Tartu, 1994, Strasser andGünter, 2001) and competition (André and Rosenberg, 1991;Kamermans, 1993) also play their part.…”

The influence of predation by herring gullsLarus argentatus and oystercatchersHaematopus ostralegus on a newly established musselMytilus edulis bed in autumn and winter

“…Crabs Carcinus maenas are important predators on young mussel beds until October. So, as large areas were depleted of mussels at the end of November, we presume that physical factors were the most important cause of mussel loss (Hilgerloh & Herlyn, 1996), as recorded two years earlier at an adjacent young mussel bed on the Neuharlingersieler Nacken (Flemming & Delafontaine, 1994).…”

Documentation of sites of intertidal blue mussel (Mytilus edulis L.) beds of the Lower Saxonian Wadden Sea, southern North Sea (as of 2003) and the role of their structure for spatfall settlement

“…Hard substrata like shells of living mussels, their byssus threads, barnacles and shell material are not obligatory preconditions for settlement; other suitable substrata for settlement are, e.g. protruding feeding tubes of Lanice conchilega, macroalgae and eelgrass (Verwey 1952;Linke 1954;Blok de and Geelen 1958;Hertweck 1993Hertweck , 1995Flemming and Delafontaine 1994;Meixner 1995;Pulfrich 1995). Presumably, the sites were selected for settlement because of suitable abiotic conditions for mussel beds such as wave action, Xow velocity and emersion time (Brinkman et al 2002).…”