The utilization of nonliving algal products by larval oysters

• Main Author: DeBoer, James Arthur
• Other Authors: Phinney, Harry K., Botany, Oregon State University. Graduate School
• Format: Doctoral or Postdoctoral Thesis
• Language: English; unknown
• Published: Oregon State University
• Subjects: Oyster culture; Crassostrea gigas
• Online Access: https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/w66345975

Although studies have shown that some marine invertebrates can obtain a portion of their nutrition from dissolved and nonliving particulate organic matter, the relative importance of such foods in their diet has not been established. The success of oyster hatcheries could be significantly improved if the diet of living algal cells can be replaced by one of soluble organics or nonliving particles. The degree to which living algal cells, dissolved organic matter (DOM) and organic aggregates are taken up by young Crassostrea gigas larvae is compared in this study. The relative uptake of the three types of potential food is established by measuring the amount of ¹⁴C-labeled food incorporated in 24 hours. DOM is prepared from the ¹⁴C -labeled algal cells by cell disruption or enzymatic hydrolysis. Organic aggregates are produced from the DOM by bubbling or by precipitation. Studies of larvae 80-90 μm in length demonstrate that at low food densities (0. 5 mgC per liter), algal cells are incorporated at the highest rate. At concentrations of food above 1.8 mgC per liter, however, the rate of incorporation of DOM-fed larvae is greater than that of larvae fed on algal cells. Rates of incorporation by larvae fed organic aggregates may be higher or lower than rates of incorporation of algal cells depending on the biochemical composition, size and concentration of the aggregates. By the time the oyster larvae attain a length of 120-140 μm their capacity to incorporate algal cells has increased greatly, suggesting a change in their feeding or digestive system has occurred. Although these larvae incorporate DOM and organic aggregates at high rates, the rate of incorporation of algal cells is even higher. During the first 24 hours, up to 37% of the assimilated DOM and up to 35% of the organic aggregates are respired by the larvae. This implies that much of this food is entering the metabolic pathways. Other evidence suggests that some of the remaining assimilated DOM and organic aggregates is utilized for growth. Therefore, ...