The role of ciliates within the microbial food web in the eutrophicated part of Kaštela Bay (Middle Adriatic Sea)

Abstract

SUMMARY: Interactions among phytoplankton, bacterioplankton, heterotrophic nanoflagellates (HNF), ciliated protozoa and copepod nauplii were studied in the eutrophicated part of Kaštela Bay from May 1998 to November 1999. Special emphasis was placed on relationships between size categories of nonloricate ciliates (NLC) and other microbial food web components. Biomasses of phytoplankton and bacteria were primarily influenced by abiotic parameters. Temperature indirectly controlled variation in HNF biomass through the changes in biomass of bacteria and the smaller phytoplankton fraction. Besides HNF, bacterial biomass was affected by the NLC <10 3 µm 3 (Cell Length <20 µm). A small NLC size category (<10 4 µm 3 , CL <40 µm) could limit the growth of HNF as they compete for bacteria and as a result of direct grazing. Nonloricate ciliates >10 4 µm 3 (CL >40 µm) had a strong mutual correlation and they seemed to be controlling the microphytoplankton fraction. During the colder part of the year, HNF abundance was regulated by ciliate grazing. The high impact of ciliates in summer 1998 could have been influenced by the taxonomic composition of the phytoplankton community changing, as well as the higher eutrophication level in the study area. Predation by copepod nauplii on ciliates and carbon transfer to higher trophic levels appear to be of relative importance only in the period when they are most abundant. This paper outlines the dominant relationships within the microbial food web and suggests that a significant amount of bacterial production, phytoplankton and HNF biomass could be transferred to higher trophic levels through the microbial food web.Keywords: ciliated protozoa, biotic factors, abiotic factors, microbial food web, Adriatic Sea. -Las interacciones entre fitoplancton, bacterioplancton, nanoflagelados heterótrofos (HNF), ciliados y nauplios de copepodos fueron estudiadas en una zona eutrófica de la bahía de Kaštela desde Mayo de 1998 hasta Noviembre de 1999. Se dedicó una atención especial a la relación entre distintas clases de tamaños de ciliados no loricados (NLC) y otros componentes de las redes tróficas microbianas. Las biomasas de fitoplancton y bacterioplancton estaban principalmente influenciadas por parámentros abióticos. La temperatura de forma indirecta controlaba la variación de la biomasa de HNF, a través de cambios en la biomasa bacteriana y de la fracción de menor tamaño de fitoplancton. Aparte de los nanoflagelados heterótrofos, la biomasa bacteriana estaba afectada por los NLC <10 3 µm 3 , longitud celular <20 µm). Pequeños NLC (de una clase de tamaño <10 4 µm 3 , LC< 40 µm) podrían limitar el crecimiento de los HNF compitiendo por las bacterias y también por depredación directa sobre ellos. Los NLC >10 4 µm 3 (LC>40 µm) estaban fuertemente correlacionados con los anteriores y presuntamente son los que controlan la fracción de fitoplancton. Durante el período frío del año, la abundancia de HNF estaba regulada por la depredación de ciliados. El importante impacto de los ciliados en verano...

Influence of agriculture and aquaculture activities on the response of autotrophic picoplankton in Laguna Macapule, Gulf of California (Mexico)

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“…In summer, microzooplankton exhibits a high growth rate in coastal environments (Urrutxurtu et al 2003;Bojanic et al 2006;Sakka-Hlaili et al 2007). In Laguna Macapule, microzooplankton, including ciliates, and abundance of APP followed similar trends.…”

Multigene phylogenies of clonal Spumella-like strains, a cryptic heterotrophic nanoflagellate, isolated from different geographical regions

“…These organisms account for a substantial proportion of the heterotrophic nanoflagellate (HNF) biomass, especially in freshwater systems (Domaizon et al, 2003;Felip et al, 1999;Zhao et al, 2003), and play a major role in microbial ecology as they contribute significantly to carbon transfer through freshwater food webs (Arndt et al, 2000;Boenigk & Arndt, 2002;Sherr & Sherr, 1994). Field investigations and food web models have so far been focused primarily on HNFs as a functional group (Bojanic et al, 2006;Gasol et al, 1995;Weitere & Arndt, 2002). However, merging different taxa into 'black boxes' is insufficient to describe specific interactions and pathways within microbial food webs.…”

Ecological Study of the Rabigh Lagoon, Eastern Site of the Red Sea, Saudi Arabia with Special Reference to Eutrophication Index

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“…During our study the low number of nauplii during summer was followed by an increase in the number of copepodites. According to a previous study, a response of a cohort to environmental changes can trigger synchronization of the nauplii to copepodite succession [95]. Figure 11 Summarizes the total zooplankton during the period of our investigation.…”