ISSN:
1432-1793
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Efficient grazing by marine bivalve larvae has been thought to be limited to particles larger than 4 μm in diameter, thereby eliminating photosynthetic and non-photosynthetic picoplankton as contributers to larval diets. Documentation of ingestion, carbon retention and growth of laboratory-reared larvae of the bivalve Mercenaria mercenaria L. on Synechococcus sp. (WH7803), a small unicellular cyanobacterium 1 μm in diameter, was facilitated using 14C-labelled cells in pulse/chase experiments and growth of larvae on diets of cell mixtures of both Synechococcus sp. and the haptophyte Isochrysis aff. galbana (TISO). Clearance rates on Synechococcus sp. ranged between 2 and 23 μl larva-1 h-1 depending on ambient cell concentration and larval age. Retention efficiency of cell carbon after gut evacuation was about 55% for both prey species. Growth rates of larvae fed on monocultures of Synechococcus sp. at typical summer concentrations in coastal waters (1×105 cells ml-1, ∼29 μg C l-1) was two-fold lower than on monocultures of Isochrysis galbana at 1×104 cells ml-1 (∼120 μg C l-1). Larval growth was inhibited and atrophy of the digestive gland was observed when Synechococcus sp. was offered at concentrations at or exceeding 8.6×105 cells ml-1. Larval growth was enhanced, however, in the presence of Synechococcus sp. (5×104 cells ml-1) when Isochrysis galbana was limiting. During the diurnal study of Synechococcus sp. population dynamics conducted by Waterbury et al. (1986) in Vinyard Sound, Massachusetts, the abundance of bivalve larvae was sufficient to account for 12 to 24% of the calculated grazing activity on Synechococcus sp. When nanoplankton are scarce, invertebrate larvae may exert considerable grazing pressure on Synechococcus sp. and derive benefit from ingestion of these cyanobacteria.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00349564
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