Identification of burrowing shrimp food sources along an estuarine gradient using fatty acid analysis and stable isotope ratios

Authors: BOSLEY, KATELYN - Oregon State University; COPEMAN, LOUISE - Oregon State University; Dumbauld, Brett; BOSLEY, KEITH - National Oceanic & Atmospheric Administration (NOAA)

Submitted to: Estuaries and Coasts - Journal of the Estuarine Research Federation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/9/2016
Publication Date: 1/19/2017
Citation: Bosley, K., Copeman, L., Dumbauld, B.R., Bosley, K. 2017. Identification of burrowing shrimp food sources along an estuarine gradient using fatty acid analysis and stable isotope ratios. Estuaries and Coasts - Journal of the Estuarine Research Federation. 40:1113-1130.

Interpretive Summary: Two species of burrowing shrimps occur in high densities in U.S. West Coast estuaries, the ghost shrimp (Neotrypaea californiensis) and the blue mud shrimp (Upogebia pugettensis). Both species of shrimp are considered to be ecosystem engineers because they create and move water and sediment through extensive galleries in the sediment which influences the sediment community and cause problems for shellfish growers in some of these estuaries. While the general ecology of the shrimp has been described and they have been shown to create a dominant habitat in Yaquina Bay and other west coast estuaries, less is known about their diet and their role in the estuarine food web. The goals of this study were to identify major components of burrowing shrimp diets and detect variation in these diets along an estuarine gradient using a combination of fatty acid (FA) and stable isotope (SI) analyses. Shrimp and potential food sources including eelgrass blades, epiphytes, nacroalgae, sediment surface, sediment core, burrow wall and particulate organic material (POM) were sampled from several locations along an estuarine gradient within the Yaquina Bay estuary in August 2012. Both SI and FA analysis indicated a significant difference in food ingested by shrimp along the estuarine gradient. Stable isotope values showed mud shrimp diets consisted of carbon sources derived from sediment and eelgrass whereas ghost shrimp diets included POM and epiphytes as primary carbon sources. Shrimp from lower estuarine sites had high levels of two FA’s that suggested their diet is enriched with marine diatoms. Shrimp from upriver showed greater amounts of an FA associated with dinoflagellates and terrestrial food sources indicated by a high percentage of polyunsaturated fatty acids.

Technical Abstract: Two species of burrowing shrimps occur in high densities in U.S. West Coast estuaries, the ghost shrimp (Neotrypaea californiensis) and the blue mud shrimp (Upogebia pugettensis). Both species of shrimp are considered ecosystem engineers as they bioturbate and irrigate extensive galleries in the sediment. While their burrows comprise a dominant habitat type in west coast estuaries, little is known about their diet and their role in the estuarine food web. The primary goals of this study were to identify major components of burrowing shrimp diets and detect variation in these diets along an estuarine gradient using a combination of fatty acid (FA) and stable isotope (SI) analyses. Shrimp and potential food sources including eelgrass blades, epiphytes, Ulva, sediment surface, sediment core, burrow wall and particulate organic material (POM) were sampled along an estuarine gradient within the Yaquina Bay estuary in August 2012. Both SI and FA analysis indicated significant differences in food ingested by shrimp along the estuarine gradient. Stable isotope values showed mud shrimp diets consisted of carbon sources derived from sediment and eelgrass whereas ghost shrimp diets indicated POM and epiphytes as primary carbon sources. Shrimp from lower estuarine sites had high levels of 16:1'7 and 20:5'3 suggesting their diet is enriched with marine diatoms. Shrimp from upriver showed greater amounts of FA associated with dinoflagellates and terrestrial sources as indicated by high percentage of C18 polyunsaturated fatty acids. This is the first study to evaluate diets of these two shrimp using complimentary FA and SI approaches.