Interannual differences in the estuarine ghost shrimp, Neotrypaea californiensis

The dispersal of invertebrate marine larvae can be expected to be wide ranging and show little population structure. Neotrypaea californiensis , the burrowing ghost shrimp, is found throughout the waters and coastal estuaries of the northwestern United States. Three hundred and four larval samples were used to study population diversity and structural difference occurring over the course of spawning periods from June to September in successive years (2005 and 2006). Data and genetic analysis from nucleotide sequencing of a section of the mitochondrial Cytochrome C oxidase subunit I (COI) gene suggest that ocean-borne larvae off the coast of Oregon and Washington show little barrier to dispersal or gene flow in the open ocean. There was evidence of significant temporal differences in the genetic composition in the oceanic larval populations. Larvae from 2005 and 2006 formed samples that were genetically distinguishable from one another. Larvae collected in 2006 inside the Yaquina Bay estuary showed significant genetic distance from larvae in the offshore pool.