Quantitative study of benthic fauna in a Humboldt Bay salt marsh

My thesis is an inventory of invertebrate species found in the low region of a Humboldt Bay salt marsh during four seasons, from July 1999 to April 2000. Invertebrates are an integral part of the salt marsh, contributing to detritus breakdown and food web support. There is insufficient documentation of salt marsh invertebrates in many parts of the world, including the Pacific North American coast. I found indigenous species that were previously known from Humboldt Bay, including Streblospio benedicti, and Assiminea californica. One introduced species of amphipod, Paracorophium sp., was found that is a new arrival to the Pacific Coast. The amphipod Hyale anceps was expected to occur in Humboldt Bay but had not previously been reported. The most abundant taxon was the polychaete family Sabellidae, at 1,968 worms from 10 samples; the least abundant was one Ovatella myosotis snail. Species diversity and evenness varied moderately from sample to sample, indicating the need for repeated sampling in future studies. The sampling method I used, with core diameter 8.5 cm and a sample depth of 2 cm, is a working technique for future salt marsh benthic studies to improve upon. The 0.5 mm mesh size was effective in retaining organisms. The "abundance" samples were randomly chosen and used a consistent sampling technique with the corer. This method collected both macrofauna and meiofauna. The "diversity" samples used a searching technique where field assistants sampled as many benthic macrofauna species as possible. This second method collected several species, such as Armadilloniscus coronocapitalis, that were not found in the abundance samples.