Feces Volume and Body Volume of Abarenicola pacifica at Various Distances from Shore at False Bay

Abstract

Abarenicola pacifica is a species of deposit feeding lugworm that is often dominant in its environment and alters the sediment in ways that influence the other species that settle nearby. Because of their importance in the ecosystem, we investigated the relationship between the body size, fecal production and location of A. pacifica. We performed this survey at False Bay on San Juan Island, Washington. We hypothesized that there would be an inversely proportional relationship between distance from shore and body volume as well as the ratio of feces volume to body volume because of the distribution of organic matter towards the head of the bay. We sampled 120 worms across the length of the A. pacifica zone. We measured the volume of each fecal deposit via displacement of water in a graduated cylinder, then dug up the worm in its burrow and measured the body volume. The data show a significant proportional relationship between distance from shore and body volume, which is the opposite of what was hypothesized. We found no correlation between the feces volume and body volume or between the ratio of feces to body volume and tidal height. There are several factors such as age, predation, depth, moisture level of sand, and sediment nutrient levels that might impact the volume of both the feces and body of the worm. We conclude that lower tidal heights in the A. pacifica zone at False Bay are more conducive to the growth of the worms.