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Observations on little studied protists (chytrids and an amoeba), affecting phytoplankton populations in the upper reaches of the Schelde estuary (Belgium)

Jeroen Van Wichelen UGent, Koenraad Muylaert, Katleen Van Der Gucht UGent and Wim Vyverman UGent (2006) BELGIAN JOURNAL OF BOTANY. 139(2). p.153-166
abstract
In the summer of 1996, a detailed survey of natural phytoplankton samples from the freshwater part of the Schelde estuary was carried out to check for the occurrence of poorly studied heterotrophic protists, the herbivorous amoeba Asterocaelum algophilum and chytrid parasites. The plankton community during the summer bloom was dominated by centric diatoms (Cyclotella scaldensis, C atomus). Fungal infestations of these bloom-forming species were not observed in fixed samples, although severe infections were frequently observed in net samples which were maintained in the laboratory for a few days. The chytrid infecting the diatom Actinocyclus normanii was identified as Podochytrium cornutum. Four morphologically distinct chytrids resembling the genus Podochytrium parasitized cells of C. scaldensis. In contrast to the populations of centric diatoms, infection of the riverine Scenedesmus population by the chytrid Rhizophydium scenedesmi occurred in situ. The infection prevalence was maximum ca. 24%, leading to a twofold reduction in the biomass of Scenedesmus. It is hypothesized that the condition of the host population is a discriminating factor since only the allochtonous phytoplankton populations get infected, when entering the estuary. On the other hand, Asterocaelum algophilum was shown to feed voraciously on centric diatom cells. Cyclotella atomus, C. scaldensis and Stephanodiscus hantzschii were its main prey; infrequently, some green algae (Crucigenia) were found ingested too. At times, the amoeba was capable of grazing away ca. 25% of the diatoms per day. On average, larger diatom cells were found relatively more frequently inside 'feeding cysts' of this unusual amoeba when compared to the undigested centric diatom populations, which suggests the occurrence of some size-selectivity in the feeding behaviour of A. algophilum. Since sometimes more than 70% of the C scaldensis cells and more than 50% of the S. hantzschii cells were found ingested, the impact of grazing by A. algophilum on the populations of the larger diatom species in the estuary can be significant. As a result, more attention should be paid to the presence and role of these organisms in aquatic food web studies.
Please use this url to cite or link to this publication:
author
organization
year
type
journalArticle (original)
publication status
published
subject
keyword
chytrids, Asterocaelum, diatoms, herbivorous amoebae, phytoplankton, Schelde estuary, COASTAL-PLAIN ESTUARIES, NAKED AMEBAS, PHLYCTIDIUM-SCENEDESMI, ASTERIONELLA-FORMOSA, DIATOM ASTERIONELLA, TEMPORAL PATTERNS, FUNGAL PARASITES, ZOOPLANKTON, NETHERLANDS, DYNAMICS
journal title
BELGIAN JOURNAL OF BOTANY
Belgian J. Bot.
volume
139
issue
2
pages
153 - 166
Web of Science type
Article
Web of Science id
000249323600002
JCR category
PLANT SCIENCES
JCR impact factor
0.208 (2006)
JCR rank
137/145 (2006)
JCR quartile
4 (2006)
ISSN
0778-4031
language
English
UGent publication?
yes
classification
A1
id
415980
handle
http://hdl.handle.net/1854/LU-415980
date created
2008-05-27 10:01:00
date last changed
2015-03-27 13:59:31
@article{415980,
  abstract     = {In the summer of 1996, a detailed survey of natural phytoplankton samples from the freshwater part of the Schelde estuary was carried out to check for the occurrence of poorly studied heterotrophic protists, the herbivorous amoeba Asterocaelum algophilum and chytrid parasites. The plankton community during the summer bloom was dominated by centric diatoms (Cyclotella scaldensis, C atomus). Fungal infestations of these bloom-forming species were not observed in fixed samples, although severe infections were frequently observed in net samples which were maintained in the laboratory for a few days. The chytrid infecting the diatom Actinocyclus normanii was identified as Podochytrium cornutum. Four morphologically distinct chytrids resembling the genus Podochytrium parasitized cells of C. scaldensis. In contrast to the populations of centric diatoms, infection of the riverine Scenedesmus population by the chytrid Rhizophydium scenedesmi occurred in situ. The infection prevalence was maximum ca. 24\%, leading to a twofold reduction in the biomass of Scenedesmus. It is hypothesized that the condition of the host population is a discriminating factor since only the allochtonous phytoplankton populations get infected, when entering the estuary. On the other hand, Asterocaelum algophilum was shown to feed voraciously on centric diatom cells. Cyclotella atomus, C. scaldensis and Stephanodiscus hantzschii were its main prey; infrequently, some green algae (Crucigenia) were found ingested too. At times, the amoeba was capable of grazing away ca. 25\% of the diatoms per day. On average, larger diatom cells were found relatively more frequently inside 'feeding cysts' of this unusual amoeba when compared to the undigested centric diatom populations, which suggests the occurrence of some size-selectivity in the feeding behaviour of A. algophilum. Since sometimes more than 70\% of the C scaldensis cells and more than 50\% of the S. hantzschii cells were found ingested, the impact of grazing by A. algophilum on the populations of the larger diatom species in the estuary can be significant. As a result, more attention should be paid to the presence and role of these organisms in aquatic food web studies.},
  author       = {Van Wichelen, Jeroen and Muylaert, Koenraad and Van Der Gucht, Katleen and Vyverman, Wim},
  issn         = {0778-4031},
  journal      = {BELGIAN JOURNAL OF BOTANY},
  keyword      = {chytrids,Asterocaelum,diatoms,herbivorous amoebae,phytoplankton,Schelde estuary,COASTAL-PLAIN ESTUARIES,NAKED AMEBAS,PHLYCTIDIUM-SCENEDESMI,ASTERIONELLA-FORMOSA,DIATOM ASTERIONELLA,TEMPORAL PATTERNS,FUNGAL PARASITES,ZOOPLANKTON,NETHERLANDS,DYNAMICS},
  language     = {eng},
  number       = {2},
  pages        = {153--166},
  title        = {Observations on little studied protists (chytrids and an amoeba), affecting phytoplankton populations in the upper reaches of the Schelde estuary (Belgium)},
  volume       = {139},
  year         = {2006},
}

Chicago
Van Wichelen, Jeroen, Koenraad Muylaert, Katleen Van Der Gucht, and Wim Vyverman. 2006. “Observations on Little Studied Protists (chytrids and an Amoeba), Affecting Phytoplankton Populations in the Upper Reaches of the Schelde Estuary (Belgium).” Belgian Journal of Botany 139 (2): 153–166.
APA
Van Wichelen, J., Muylaert, K., Van Der Gucht, K., & Vyverman, W. (2006). Observations on little studied protists (chytrids and an amoeba), affecting phytoplankton populations in the upper reaches of the Schelde estuary (Belgium). BELGIAN JOURNAL OF BOTANY, 139(2), 153–166.
Vancouver
1.
Van Wichelen J, Muylaert K, Van Der Gucht K, Vyverman W. Observations on little studied protists (chytrids and an amoeba), affecting phytoplankton populations in the upper reaches of the Schelde estuary (Belgium). BELGIAN JOURNAL OF BOTANY. 2006;139(2):153–66.
MLA
Van Wichelen, Jeroen, Koenraad Muylaert, Katleen Van Der Gucht, et al. “Observations on Little Studied Protists (chytrids and an Amoeba), Affecting Phytoplankton Populations in the Upper Reaches of the Schelde Estuary (Belgium).” BELGIAN JOURNAL OF BOTANY 139.2 (2006): 153–166. Print.