Caught in a Net: Retention Efficiency of Microplankton = 10 and 50 Mu M Collected on Mesh Netting
Abstract
Living organisms >= 10 mu m and < 50 mu m in ballast water discharged from ships are typically collected by filtering samples through a monofilament mesh net with pore openings sized to retain organisms >= 10 mu m. This (or any) filtering method does not result in perfect size fractionation, and it can induce stress, mortality, and loss of organisms that, in turn, may underestimate the concentration of organisms within samples. To address this loss, the retention efficiency (RE) was determined for six filtration approaches using laboratory cultures of microalgae and ambient marine organisms. The approaches employed a membrane filter or mesh nettings of different compositions (nylon, stainless steel, polyester, and polycarbonate), nominal pore sizes (5, 7, and 10 mu m), and filtering sequences (e.g., pre-filtering water through a coarse filter). Additionally, in trials with polycarbonate track etched (PCTE) membrane filters, water was amended with particulate material to increase turbidity. Organisms >= 10 mu m were counted in the material retained on the filter (the filtrand), the material passing through the filter (the filtrate), and the whole water (i.e., unfiltered water). In addition, variable fluorescence fluorometry was used to gauge the relative photochemical yield of phytoplankton-a proximal measurement of the physiological status of phytoplankton-in the size fractions. Further, the mesh types and filters were examined using scanning electron microscopy, which showed irregular openings.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 09, 2017
- Accession Number
- AD1102218
Entities
People
- Lisa A. Drake
- Matthew R. First
- Scott C. Riley
- Stephanie H. Robbins-wamsley
- Vanessa Molina
Organizations
- United States Naval Research Laboratory