BIOTIC Species Information for Abra alba
|Researched by||Lizzie Tyler||Data supplied by||University of Sheffield|
|Refereed by||This information is not refereed.|
||Feeding method||Passive suspension feeder
Active suspension feeder
Surface deposit feeder
Sub-surface deposit feeder
|Typical food types||Phytoplankton, detritus.||Habit||Burrow dwelling|
|Bioturbator||Flexibility||None (< 10 degrees)|
|Height||Insufficient information||Growth Rate||0.1 mm/day|
|Adult dispersal potential||100-1000m||Dependency||Independent|
|General Biology Additional Information||Abundance
Although described as solitary animals, adult densities may exceed 1,000 m² in favourable conditions. For instance, in the rich organic muddy harbour sediments in the Ria de la Coruna (NW Spain) Abra alba densities varied from 97 to 2,939 individuals/ m² (Francesch & Lopez-Jamar, 1991). In front of Dunkirk, France, densities can reach 9,000 individuals / m² (Ghertsos et al., 2000). However, abundances typically fluctuate between years owing to variation in recruitment success (juvenile bivalves experience high mortality within the first month after settlement) or adult mortality. High densities of newly settled spat have been reported. For instance, estimated densities of between 16,000 - 22,000 individuals/ m² (collected on 1 mm sieves) were recorded by Jensen (1988) at the time of settlement in the western part of the Limfjord, Denmark.
The smallest recorded benthic specimen had a shell length of 0.34 mm (Dauvin & Gentil, 1989). In autumn settled spat growth is insignificant until spring when a maximum growth rate of 0.1 mm/day was reported (Dauvin, 1986). This growth rate applies from spring to autumn (Dauvin, pers. comm.).
Some bivalves, such as Abra alba, which inhabit muddy low energy environments can switch back and forth from suspension feeding and deposit feeding, depending upon the conditions of the environment (Dame, 1996). While suspension feeding, the inhalant siphon is held a few millimetres above the sediment surface and sucks in suspended particles. For instance, Abra alba significantly reduced the concentration of the flagellate Isochrysis galbana in suspension. Consumption of Isochrysis galbana over four hours was estimated to be 2.7% of the body weight (Rosenberg, 1993). While deposit feeding, the inhalant siphon is bent over toward the sediment surface, sucking up detritus. However, as the food quality of sediments is often low, deposit feeders either have to process large volumes of sediment through the digestive tract in order to gain a small amount of nutrition, or they sort particles before ingestion and reject the majority of particles as pseudofaeces. As a result the feeding rate is lower with a longer residence time for food in the gut, enabling digestion of the more complex organic compounds common to the benthic environment (Dame, 1996).
Biomass and productivity
In Kiel Bay, mean annual biomass varied greatly between sites and between years: Biomass (B) =0.1-3 g AFDW m², with a long-term average (ratio) P:B = c 2.2 (Rainer, 1985); B = 0.1-2 g AFDW m² and P:B = 1.7-2.9 from five years of sampling at a location off the French coast (Dauvin, 1986); B = 0.3 g AFDW m² and P:B = 1.4 in the Bristol Channel, England (Warwick & George, 1980).
|Biology References||Nott, 1980, Allen, 1983, Dauvin, 1982, Dauvin & Gentil, 1989, Dame, 1996, Rosenberg, 1993, Francesch & Lopez-Jamar, 1991, Jensen, 1988, Rees & Dare, 1993, Rainer, 1985, Dauvin, 1986, Warwick & George, 1980, Ghertsos et al., 2000,|