Da. Kreeger et Rie. Newell, Seasonal utilization of different seston carbon sources by the ribbed mussel, Geukensia demissa (Dillwyn) in a mid-Atlantic salt marsh, J EXP MAR B, 260(1), 2001, pp. 71-91
Citations number
39
Categorie Soggetti
Aquatic Sciences
Journal title
JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY
Seston in salt marshes contains a temporally and spatially complex mixture
of natural microparticulate organic material, including phytoplankton, vasc
ular plant detritus, bacteria, heterotrophic nanoflagellates and benthic di
atoms. Quantitative information is available concerning how suspension-feed
ing consumers, such as the ribbed mussel, Geukensia demissa (Dillwyn), util
ize some of these components to satisfy their carbon demands. Despite this
information there is still a limited understanding of how the relative nutr
itive contribution of these different dietary items may shift during the ye
ar associated with variations in both seston composition and the mussel's p
hysiological condition. To investigate if the mussel's ability to use speci
fic constituents of natural seston varies seasonally, we ran a series of pu
lse-chase C-14 feeding experiments under ambient conditions in March, May,
August and November 1996. Phytoplankton, cellulosic detritus, bacteria, het
erotrophic nanoflagellates and benthic diatoms were radiolabeled and supple
mented in small amounts to natural marsh water for feeding to mussels. The
fate of C-14 in mussel tissues, feces, respiration and excretion was quanti
fied and contrasted among the different diet types and seasons. Microcapsul
es containing radiolabeled carbohydrate and protein were used as standards
to differentiate possible between-experiment variations in seston compositi
on from seasonal changes in the mussel's feeding and digestive physiology.
Mussel clearance rates for all diets were highest in summer and autumn and
lowest in winter and spring. In contrast, seasonal shifts in digestive phys
iology were only found for certain diets. The seasonal range of assimilatio
n efficiencies for microcapsule standards (18-29%) and field-collected micr
oheterotrophs (bacteria76-93% and heterotrophic nanoflagellates 87-94%) did
not differ significantly during the year, whereas summer and autumn assimi
lation efficiencies for cellulosic detritus (22-24%), phytoplankton (71-79%
) and benthic diatoms (89-93%) were up to twofold greater than those in win
ter and spring (13%, 40-59% and 45-81%, respectively). We conclude that the
digestive physiology (e.g., digestive enzyme production) of mussels respon
ds to shifts in dietary components during the year. (C) 2001 Elsevier Scien
ce B.V. All rights reserved.