Heterotrophic dinoflagellate fecal pellet production: grazing of large, chain-forming diatoms during upwelling events in Monterey Bay, California

Abstract

An athecate phagotrophic dinoflagellate (Gyrodinium sp.) ingests chain-forming diatoms that are abundant during upwelling events in Monterey Bay, CA, USA, and contiguous waters. The chains are digested and egested with a peritrophic membrane covering the fecal pellet, consistent with earlier reports from high productivity environments. The maximum abundance of the dinoflagellate during more than a decade of monitoring was 4000 cells l -1 . Its primary prey comprised chains of centric diatoms such as Chaetoceros spp. or Skeletonema spp., although Pseudo-nitzschia spp. were also observed in the dinoflagellate's fecal pellets. Maximum grazing by this dinoflagellate represented 10% of the total phytoplankton biomass. Our observations suggest a lesser role of large heterotrophic dinoflagellates in the ecology of central California waters compared to other regions. KEY WORDS: Heterotrophic dinoflagellates · Microzooplankton grazing Resale or republication not permitted without written consent of the publisherAquat Microb Ecol 40: [293][294][295][296][297][298] 2005 MATERIALS AND METHODSSamples used in this study came from surface water taken as part of routine sampling in Monterey Bay in 1993(Pennington & Chavez 2000 and from Monterey Bay and contiguous waters of the California Current sampled during a multi-ship experiment in 1995 (see Brzezinski et al. 1997). Stations sampled varied in distance offshore (5 to 56 km: Table 1). Aliquots of surface water collected with a CTD and Niskin bottles were preserved with glutaraldehyde (final concentration 2%); 25 ml of the preserved seawater were filtered through 0.2 µm pore size, 25 mm diameter, polycarbonate filters and placed on a coverslip with a drop of Zeiss immersion oil between filter and coverslip. Epifluorescence enumerations and biomass estimates following standard procedures (Buck et al. 1992a). Aliquots were prepared for scanning electron microscopy (SEM) by filtration through polycarbonate filters, followed by rinsing with distilled water and air drying; 10 ml subsamples from a recent expedition (March 2000) were settled and counted on an inverted microscope to determine the abundance and content of fecal pellets. The removal of phytoplankton biomass by Gyrodinium sp. was calculated using Gyrodinium sp. clearance (2.7 × 10 4 body vol h -1 , Hansen 1992) and the concentration of phytoplankton present (Table 1). RESULTS AND DISCUSSIONThe predominant large dinoflagellate (a Gyrodinium species) was approximately 100 µm in length and 50 µm in width and was teardrop shaped (Figs. 1 to 4). We have not attempted to assign it to a species, but it was similar in size and shape to G. spirale (Hansen 1992). The size, shape and particular yellow-green fluorescence imparted by glutaraldehyde fixation (Figs. 1 to 4 (Figs. 1 to 4). In a number of instances the composition of these inclusions could be determined to the broad taxonomic level of centric/pennate diatoms (Fig. 4), and the diameter of the chain could be measured. Coincident with the high abundances of G...

Role of heterotrophic dinoflagellate Gyrodinium sp. in the fate of an iron induced diatom bloom

“…showed a surprising degree of plasticity in its ability to surround and swallow its prey (phagotrophy). The maximum prey length was 750 μm, i.e., 12 times the length of Gyrodinium sp., and was the highest value among phagotrophic HDF previously reported [ Buck et al , 2005; Hansen 1992; Strom and Strom , 1996].…”

Potential role of bacteria packaging by protozoa in the persistence and transmission of pathogenic bacteria

“…A broad range of phagotrophic protists such as dinoflagellates, ciliates, and amoebae produce and expel vesicles as a part of their normal digestive process (Gezelius, 1959 ; Hohl, 1965 ; Allen and Wolf, 1974 , 1979 ; Buck et al, 1990 , 2005 ; Buck and Newton, 1995 ; Chekabab et al, 2012 ; Paquet et al, 2013 ). These expelled vesicles, which are often called fecal pellets or fecal balls, vary in composition, size, and morphology, depending on the protist and the trophic conditions.…”

Role of heterotrophic dinoflagellates in the fate of diatoms released from fast ice in coastal water of Lützow-Holm Bay, East Antarctica

“…5B-D). On the other hand, HD can ingest such large prey due to the ability of gymnodinoid dinoflagellates to ingest prey larger than themselves (Buck et al 2005, Saito et al 2006 and of thecate dinoflagellates to feed extracellularly (Jacobson 1999). This suggests that the main prey items of ciliates are phytoflagellates and that, among the heterotrophic protists, only HD> 20 µm could utilize larger-sized P. pseudodenticulata.…”