Mesoscale Structure of Zooplankton in the California Current
Abstract
This collaborative project was designed to improve our quantitative understanding and predicative abilities for zooplankton population dynamics, especially at the boundaries of distributions, through the use of specifically designed field efforts utilizing bioacoustics, biochemical and molecular analyses, and process models. Nematoscelis difficilis (Crustacea, Euphausiacea) were collected in a persistent, eutrophic coastal eddy and in oligotrophic offshore waters of the California Current. The euphausiids were assayed for biochemical and molecular genetic traits. Kinetic assays of enzyme concentrations for phosphoglucose isomerase (PGI), lactate dehydrogenase (LDH), citrate synthase (CS), and exoldnase (HK) were used to infer physiological adaptation. DNA sequence variation of the genes encoding PGI and DH were used to estimate allele and genotype frequencies, and to infer selective mortality. DNA sequence variation of a 350 base-pair region of mitochondrial cytochrome oxidase I (mtCOI) revealed significant sample-to-sample eterogeneity; two groups of samples coastal and offshore - were differentiated by mtCOI haplotype frequencies, suggesting that N. difficilis collected in the two regions may have originated from distinct sources. Concentrations of GI and LDH were higher in individuals from the cool, rich near-shore waters. Genotype frequencies of the genes encoding these enzymes did not differ between samples or domains, suggesting that the patterns were not the result of direct selection on the traits assayed. This study provided evidence that N. difficilis individuals responded to mesoscale variability by physiological adaptation, not by differential mortality and selection. Bio-acoustical backscatter showed dramatic day-night differences along the offshore portion of the transect as well as clear vertical stratification. silhouette analysis of taxon-specific biomass revealed considerable variation in the taxonomic composition of samples on the transect.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 2000
- Accession Number
- ADA376759
Entities
People
- Ann Bucklin
- Donald B. Olson
- Peter Wiebe
Organizations
- Woods Hole Oceanographic Institution