A comparison between glass fiber and membrane filters for the estimation of phytoplankton POC and DOC production

Abstract

We tested the performance of 2 types of glass fiber filters (GF/F: 0.7 pm; GF/C: 1.2 pm) and 2 membrane filters (PC0.2: polycarbonate 0.2 p; CE0.22: mixed cellulose esters 0.22 pm) in estimating chlorophyll a and primary production with the 14C technique. Four experiments were carried out with water samples from the NW Mediterranean, the NE Atlantic and the Antarctic Ocean. The first experiment compared measurements of particulate organic carbon (POC) production whereas the other 3 also considered total (TOC) and dissolved (DOC) carbon fixation. No significant differences among filters were found regardmg chlorophyll a retention but large discrepancies existed in the amount of labelled organic carbon retained in all the experments. Both types of glass fiber filters, especially GF/F, yielded higher values of apparent P014C recovery than the membrane filters. The GF/Fderived POC production rates were up to twice the PC0.2-derived rates and 63 % higher than CE0.22-derived ones. Accordingly, the estimated rates of phytoplanktonic DOC production were higher with the membrane filters in comparison to the GF/F ones. This discrepancy was attributed to a high D0I4C adsorption to the glass fibers of GF filters. Due to uncertainties in the magnitude of t h s process in other samples, we conclude that GF filters are not suitable when particulate primary production must be measured without interference of released dissolved products, and that membrane filters should be used instead.

Effect of solar ultraviolet radiation on bacterio- and phytoplankton activity in a large coral reef lagoon (southwest New Caledonia)

“…The filtrate was used to determine DPP following the same procedure as TPP. The problem of a possible adsorption of dissolved carbon on GF/F filter has been previously raised (Morán et al 1999), but Renaud et al (2005) recently demonstrated that such an artifact was not relevant in the present type of study. Scintillation vials were counted in a Packard Scintillation Counter (TriCarb 1600) and corrected for background and quenching, and results are given in mg C m -3 h -1 .…”

Dissolved organic matter (DOM) release by phytoplankton in the contemporary and future ocean

“…Unassimilated radioactive inorganic carbon is driven off the samples by acidification and the amount of radioactive carbon incorporated into the DPP and PPP is counted and used to calculate PER (Hellebust, 1965;Morán et al, 2006). Sources of error in this technique include the transformation of PPP to DPP through cell lysis during filtration (Sharp, 1977) and the binding of DOM to the filters (Karl et al, 1998;Morán et al, 1999).…”

A comparison of the retention capability among three different glass-fiber filters used for chlorophyll-a determinations

“…However, after the discovery of photoautotrophers smaller than 1 µm, such as cyanobacteria (Waterbury et al, 1979) and picoeukaryotes (Johnson & Sieburth, 1982), membrane filters of varied composition and smaller nominal pore size (0.22 or 0.10 µm) have been suggested in order to retain these organisms (Li et al, 1983;Platt et al, 1983). Many comparisons between glass fiber and membrane filters for several kinds of analyses, such as seston, POC, primary production by 14 C method and also pigments have been carried out (Sheldon, 1972;Holm-Hansen & Reimann, 1978;Phinney & Yentsch, 1985;Morán et al, 1999;Ashimoto & Hiomoto, 2000). Morán et al (1999) compared the filters GF/C (1.2 µm), GF/F (0.7 µm), polycarbonate (0.2 µm) and cellulose esters (0.22 µm) using natural samples and verified no significant differences among these filters in terms of Chl-a retention, since flow cytometry analyses showed that most cells were larger than 1 µm.…”

“…Many comparisons between glass fiber and membrane filters for several kinds of analyses, such as seston, POC, primary production by 14 C method and also pigments have been carried out (Sheldon, 1972;Holm-Hansen & Reimann, 1978;Phinney & Yentsch, 1985;Morán et al, 1999;Ashimoto & Hiomoto, 2000). Morán et al (1999) compared the filters GF/C (1.2 µm), GF/F (0.7 µm), polycarbonate (0.2 µm) and cellulose esters (0.22 µm) using natural samples and verified no significant differences among these filters in terms of Chl-a retention, since flow cytometry analyses showed that most cells were larger than 1 µm. But these authors discuss that this result could be different if picoplankton had contributed in a large fraction in those samples.…”

“…Chavez et al (1995) compared Chl-a measurements obtained from field samples using Whatman GF/F and Nuclepore or Poretics 0.22 µm filters and concluded that GF/F can be used to measure accurately Chl-a even in oligotrophic waters such as found in the low latitude subtropical gyres and equatorial divergence. So, in biological oceanography GF/F filters are accepted as a standard for phytoplankton Chl-a determination (Chavez et al, 1995;Morán et al, 1999). _________ Contr.…”