Meeting Abstract
Food concentration may often be so low as to limit growth of the feeding larvae of marine invertebrates, extending larval planktonic duration or reducing juvenile quality. Another challenge facing larvae is that in addition to food, the plankton contains particles that are too large to ingest but which may interfere with feeding. In simplified laboratory conditions, Lizárraga et al. (2017, Mar. Biol. 164:102) found that large inedible beads or centric diatoms at concentrations of 25-500 mL-1 reduced ingestion of edible particles by echinoderm larvae by up to 80%. Does the assemblage of large inedible particles present in natural plankton have similar effects on larval feeding? On two days in spring 2017, we offered larvae of the sand dollar Dendraster excentricus 6 µm beads in natural seawater filtered so as to contain either no particles (0.2 µm filter), natural food only (35 µm filter), or natural food and large inedible particles (200 µm filter). In the first experiment, large centric diatoms were abundant (~90 mL-1) in the 200 µm-filtered treatment, and ingestion of 6 µm beads in that treatment was reduced by >40% compared to other treatments. In the second, centric diatoms were rare but large pennate diatoms were abundant (~125 mL-1); these did not affect larval ingestion. These results suggest that some types of naturally occurring large inedible particles at natural concentrations may interfere with larval feeding, potentially exacerbating effects of food limitation. In future studies we will compare the effects of different types of large particles on larval ingestion, and the effects of large inedible particles on larval planktonic duration and juvenile quality.
