Growth variations in the bivalve Mya truncata : a tool to trace changes in the Frisian Front macrofauna (southern North Sea)?

Abstract

Annual monitoring of the benthic fauna living at the Frisian Front (southern North Sea) has shown a tenfold decrease in the dominant brittlestar Amphiura filiformis in 1993-1995. In search of evidence that this decline was caused by a change in benthic food supply, we analysed variations in the shell growth of the bivalve Mya truncata from the Frisian Front during the period of interest. For this purpose, the widths of the internal growth bands in the chondrophore of M. truncata were standardised and assigned to calendar years. Averaging the yearly band width in the period 1985-2000 among 25 individuals revealed low growth rates in 1986 and 1992. Growth of M. truncata quickly recovered after 1992, while A. filiformis densities remained at low levels. Moreover, the 1986 dip in M. truncata growth had no equivalent in A. filiformis density. We conclude that there is no direct coupling between fluctuations in density of A. filiformis and variations in growth of M. truncata. The data we collected during this study on the size and spatial distribution of M. truncata are discussed in the light of plans for the protection and conservation of long-lived benthic organisms in the North Sea.

Hydrographic Changes in Nares Strait (Canadian Arctic Archipelago) in Recent Decades Based on δ18O Profiles of Bivalve Shells

“…All the H. arctica for age analysis were collected live at Bellot Island over nearly the entire depth range up to approximately 30 m, and ranged in age from 5 to 50 years (± 2 years). The ages obtained in this study for M. truncata (14 years), S. groenlandicus (8 years), and H. arctica (5 to 22 years), shown in Table 3, agree well with the typical life spans for these individuals reported by other investigators (Sejr et al, 2002;Amaro et al, 2003;Kilada et al, 2007). The estimated ages for A. borealis (20 to 150 years) are significantly higher than the maximum age of 8 years for specimens with similar shell lengths reported by Selin (2007).…”

Growth trends in three bivalve species indicate climate forcing on the benthic ecosystem in the southeastern North Sea

“…Based on the results published for the closely related species Mya arenaria (MacDonald & Thomas 1980, Brousseau & Baglivo 1987 we assumed that growth bands in Mya truncata are formed annually as well, although this periodicity has not been verified by us. On the basis of band counts, the maximum ages found for M. truncata and C. striatula are 27 and 21 yr, respectively (Witbaard et al 2001, Amaro et al 2003. The maximum age of A. islandica is estimated to surpass 200 yr (Jones 1983), although specimens with such longevity have never been found in the SE North Sea.…”

“…Chamelea striatula is regarded as a lusitanian species, while Arctica islandica and Mya truncata are regarded as boreal and boreal-arctic species, respectively. The latter 2 species reach their southern distribution limits in the North Sea at the Frisian Front (Amaro et al 2003). For C. striatula the Oyster Grounds lies in the northern part of its distribution range (Witbaard et al 2001).…”

The consequences of changes in abundance of Callianassa subterranea and Amphiura filiformis on sediment erosion at the Frisian Front (south-eastern North Sea)

“…m -2 . Causes for the species shift are unresolved (Amaro et al, 2003). Equally puzzling is the lack of recovery of the A. filiformis population since this species has annual reproduction (Duineveld & Van Noort, 1986) and recovered 5 years after a comparable crash in the German Bight (Schroeder, 2003).…”