Mesozooplankton Dry Weight Biomass
- Title
- Dry weight biomass measurements of net-collected mesozooplankton. Samples collected in the CCE-LTER region on Process Cruises from 2006 to the present. Summaries for each Lagrangian Cycle.
- Abstract
- Mesozooplankton are collected with plankton nets (typically a 71-cm diameter, 202-um mesh Bongo net) and samples flash frozen at sea in liquid N2 for subsequent shore-based measurements of dry weight biomass. Measurements are made by weighing pre-tared Nitex mesh on an analytical balance, for mesozooplankton size-fractionated into 5 different categories (> 0.2 mm, 0.5 mm, 1.0 mm, 2.0 mm, 5.0 mm). Biomass is expressed as dry mass of zooplankton per m3 of water filtered, or when multiplied by the maximum depth of the tow, as integrated dry mass of zooplankton per m2 of sea surface. Samples for dry weight biomass have been collected on CCE-LTER Process Cruises since 2006 and these collections are ongoing.
Data
|
table
|
process_cruise_dry_weight_biomass
Dry weight biomass measurements of net-collected mesozooplankton. Samples collected in the CCE-LTER region on Process Cruises from 2006 to the present. Summaries for each Lagrangian Cycle.
|
Rows: 666
Columns: 12
|
View / Download
|
Methods
- Mesozooplankton sampling by Bongo net
- Mesozooplankton are sampled with quantitative plankton nets, usually a 0.71-m diameter Bongo net frame, using the CalCOFI sampling protocol (https://cce.lternet.edu/data/methods-manual/augmented-cruises/calbobl-net-depolyment). However, unlike CalCOFI, we use 202-um Nitex mesh nets and hard cod ends with the same size mesh. A calibrated General Oceanics flow meter is mounted in the mouth of one net. Samples are typically double oblique (from surface to 210 m to surface; depth is based on 300 mwo with a 45° wire angle) or vertical (from surface to 100 m to surface; nominal 0° wire angle). A stainless steel weight (ca. 50 kg) is mounted to the bottom of the bongo frame. Samples from one side of the bongo net are preserved in sodium borate-buffered Formalin (final concentration of 5% Formalin = 1.85% formaldehyde). Samples from the other net are used for gut fluorescence and dry mass biomass determination. The latter samples are anesthetized with soda water immediately upon retrieval to inhibit net feeding and regurgitation. Both nets are carefully washed to ensure quantitative recovery of all sampled material.
- Size fractionation and flash freezing samples
- The anaesthetized zooplankton sample is taken promptly into a shipboad laboratory and split on a Folsom splitter to obtain 3/8 of the sample for gut fluorescence, 3/8 of the sample for dry biomass, and 1/4 of the sample for molecular probes. Samples are kept cool while processing. The gut fluorescence and the biomass aliquots are passed separately through a nested 5-filter series of Nitex sieves resulting in 5 size fractions (0.2-0.5 mm, 0.5-1.0 mm, 1.0-2.0 mm, 2.0-5.0 mm, > 5.0 mm). Each of these samples is concentrated on a 202 um mesh filter, placed in a labelled plastic petri dish, and flash frozen in liquid N2 for analysis ashore. Samples for dry weight biomass are filtered onto pre-tared 202-um mesh filters. After filtration, biomass samples are rinsed with isotonic ammonium formate to remove residual salts.
- Laboratory analysis
- Frozen Nitex filters are transferred to a drying oven, dessicated at 60° C for 24 hours, then the entire filter is weighed on an analytical balance. The difference between the sample weight and the tared filter weight is the total biomass in a sample. This value is then corrected for the fraction of the sample split and the volume of seawater filtered at sea, to express dry biomass as mg dry mass per m3 of seawater.