Mesoscale Structure of Zooplankton in the California Current
Abstract
This collaborative project was designed to improve our quantiative understanding and predicitive abilities for zooplankton population dynamics, especially at the boundaries of distributions, through the use of specifically designed field efforts utilizing bio-acoustics, biochemical and molecular analyses, and process models. Nematoscelis difficllis (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 hexokinase (HK) were used to infer physiological adaptation. DNA sequence variation of the genes encoding PGI and LDH 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 heterogeneity; two groups of samples - coastal and offshore - were differentiated by mtCOI haplotype frequencies, suggesting that N. difficllis collected in the two regions may have originated from distinct sources. Concentrations of PGI 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.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 31, 1999
- Accession Number
- ADA375832
Entities
People
- Ann Bucklin
- Donald B. Olson
- Peter H. Wiebe
Organizations
- University of New Hampshire