Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Related Publications
• Parameters
• Instruments
• Deployments
• Project Information
• Funding

This dataset includes animal condition data for individual Pleuromamma xiphias specimens collected across ocean provinces on Atlantic Meridional Transect Cruise 24 (AMT24) in October 2014. Reported measurements include copepod prosome length (PL), wet and dry weight, carbon and nitrogen content, delta-15N and delta-13C stable isotope values, C:N ratio, and condition factor index (CFI).

Dataset release date is approximate.

Field collection. Adults of Pleuromamma xiphias were collected on the Atlantic Meridional Transect Cruise 24 (AMT24), between 4 Oct and 28 Oct 2014 (Fig. 1, Table S1). Animals from 20 stations along the cruise transect between 31°N and 43°S were included in this study. Oblique bongo tows (200 mm nets) were conducted between on average 310 m and the sea surface. Upon recovery at the surface, plankton from one net was diluted into chilled seawater, and sorted immediately.  At some stations, plankton was split quantitatively in a Folsom plankton splitter prior to sorting. Adult females of Pleuromamma xiphias were sorted live under the microscope, flash frozen and stored in liquid nitrogen at sea, followed by transfer to -80°C in the laboratory. Only adult females were included in this study, in order to ensure comparable measurements across the oceanographic transect.  Adult males have larger body size than females (Bradford-Grieve 1999), and are expected to have higher carbon and nitrogen content as well as dry weight relative to females.

Cryopreserved Pleuromamma xiphias females were stored on ice during all initial handling steps, with 5-10 animals processed at a time. Prosome length (mm) of each animal was measured in right lateral view.  Individual females were then blotted dry and transferred to pre-weighed tin capsules for wet weight and dry weight measurements. Dry weight: copepods were individually weighed using a Mettler Toledo UMX2 ultramicrobalance, dried at 60°C for 24-72 hours, and weighed again.  

Carbon and Nitrogen content: One or two individual copepods were included in elemental and isotope analyses, depending on dry weight.  The C content, N content and bulk isotope composition of P. xiphias was determined using a Costech elemental combustion system (Model 4010) coupled to a ThermoFinnigan Delta Plus XP Isotope Ratio Mass Spectrometer (IRMS) through a Conflo IV interface.  Isotope values are reported in standard δ-notation relative to the atmospheric N2 standard (AIR) as δ15N (‰) = [(15N:14Nsample / 15N:14NAIR) - 1] x 1000 or relative to Vienna Pee Dee Belemnite (VPDB) as δ13C (‰) = [(13C:12Csample / 13C:12CVPDB) - 1] x 1000.  To ensure accuracy, glycine and ground tuna reference samples with well-characterized δ15N values were analyzed every 10 samples.  The standard deviation of samples analyzed in duplicate was ≤ 0.2‰. Body size and weight measurements were made on a total of 237 animals, with 106 carbon and nitrogen content and isotopic measurements made across the transect.

Condition index (CFI) defined as CFI = 1000 x DW/(PL)3 (Ikeda et al. 2006). Stable isotope values measured on single individuals or in pools of N=2 (as noted in the SIA identifier column).

BCO-DMO Processing Notes:
- added conventional header with dataset name, PI name, version date
- modified parameter names to conform with BCO-DMO naming conventions
- converted latitude and longitude to decimal degrees
- re-formatted date from m/d/yyyy to yyyy-mm-dd

Description from NSF award abstract:
Marine zooplankton show strong ecological responses to climate change, but little is known about their capacity for evolutionary response. Many authors have assumed that the evolutionary potential of zooplankton is limited. However, recent studies provide circumstantial evidence for the idea that selection is a dominant evolutionary force acting on these species, and that genetic isolation can be achieved at regional spatial scales in pelagic habitats. This RAPID project will take advantage of a unique opportunity for basin-scale transect sampling through participation in the Atlantic Meridional Transect (AMT) cruise in 2014. The cruise will traverse more than 90 degrees of latitude in the Atlantic Ocean and include boreal-temperate, subtropical and tropical waters. Zooplankton samples will be collected along the transect, and mitochondrial and microsatellite markers will be used to identify the geographic location of strong genetic breaks within three copepod species. Bayesian and coalescent analytical techniques will test if these regions act as dispersal barriers. The physiological condition of animals collected in distinct ocean habitats will be assessed by measurements of egg production (at sea) as well as body size (condition index), dry weight, and carbon and nitrogen content. The PI will test the prediction that ocean regions that serve as dispersal barriers for marine holoplankton are areas of poor-quality habitat for the target species, and that this is a dominant mechanism driving population genetic structure in oceanic zooplankton.

Note: This project is funded by an NSF RAPID award. This RAPID grant supported the shiptime costs, and all the sampling reported in the AMT24 zooplankton ecology cruise report (PDF).

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