Seasonal Variations in Planktonic Community Structure and Production in an Atlantic Coastal Pond: The Importance of Nanoflagellates

Abstract

The structure and summertime production of planktonic communities and the role of nondiatom planktonic cells were studied in coastal ponds, which are areas traditionally used for fattening and greening table-sized oysters. The abundance and biomass of nano-microplanktonic protists were determined at weekly intervals between February 1998 and February 1999 in a coastal pond without oysters in the French Atlantic coast near La Rochelle. The production of these microbiotas was determined in the summer period. The structure of plankton communities revealed the following observations: (1) microphytoplanktonic cells were mostly diatoms and dinoflagellates, (2) microzooplanktonic cells were mainly ciliates, and (3) nanoplanktonic cells were represented by pigmented (80-90% of the nanoplankton biomass) and colorless nanoflagellates. Diatoms were dominated by Naviculiineae. Dinoflagellates were dominated by Peridiniales. Oligotrichida were predominant in the ciliate community. Protist biomass levels were nine times higher from April to August (summer period 1033 microg C L(-1)) than from September to March (winter period 114 microg C L(-1)). Whatever the season, nanoflagellates were dominant in the water column (66 and 53% of the entire protist biomass in the summer and winter periods, respectively). Nanoflagellates represented the highest production of nano-microplanktonic communities (76% of carbon protist production) in the coastal pond in summer and showed the shortest generation time (7.1 h). Dinoflagellates came after nanoflagellates in production (19.5% of carbon protist production). Diatoms represented only a supplementary carbon resource available for higher trophic levels, whereas, until now, they were considered as the principal food of oysters in coastal ponds. Ciliates were a small source of carbon, but their growth rate was high. We suggest, first, that nanoflagellates represented the primary resource available in the pond and could constitute an important food resource for higher trophic levels, such as oysters, farmed in this type of pond. Overall, the system appeared to be more autotrophic than heterotrophic. Because inorganic nutrients are quickly exhausted in a semiclosed pond, pigmented flagellates dominated the carbon biomass, production and biomass of bacteria were high (thus, the microbial food web appeared to be active in this pond), and mixotrophy seemed to be an important trophic mode there.

Microorganism dynamics during a rising tide: Disentangling effects of resuspension and mixing with offshore waters above an intertidal mudflat

“…given nanoplankton growth rate ranging from 7 h (Dupuy et al, 2007) to 20 h (Calbet et al 2008;Liu et al 2009). Thus, doubling of HNF concentration in the water column suggest that HNF concentration in eroded sediment during the survey was roughly 10 5 cell mL -1 , which is a hundred times greater than previously reported average values found in the first top cm of the BMO sediment (10 3 cell mL -1 , C. Dupuy personal communication).…”

“…However, a total community change occurred with replacement of benthic diatoms by pelagic diatoms in proportion of water depth change during the rising tide. No significant primary production of diatoms was expected given the short duration of the Eulerian survey compared to the generation time for microphytoplankton (1 division d -1 , Calbet and Landry 2004 to 2 divisions d -1 , Dupuy et al 2007) and water turbidity (Struski and Bacher 2006;Bouman et al 2010). Thus, mixing was the most likely dominant process.…”

Differentiating the role of different-sized microorganisms in peptide decomposition during incubations using size-fractioned coastal seawater

“…In June 2013, higher AVFA decomposition rate was only observed in the unfiltered seawater, indicating that the larger-sized protists (>20 μm) were involved in the peptide decomposition. Higher temperature in summer 2013 than winter 2011 (Table 1) may have caused faster growth and larger cell volume of protists (Dupuy et al, 2007;Auer and Arndt, 2001). Alternatively, specific types of protists that can utilize peptides may differ between winter and summer.…”

Effects of Eutrophication on Flagellates Associated with Eichhornia crassipes: An Experimental Approach

“…This excess of nutrients is considered to be one of the major pollution sources in aquatic ecosystems (ESTEVES, 1998). The result is a series of biological events including: an increase in the dominance of certain trophic levels, such as an increase in algal biomass; modification of microbial loop components (bacteria, flagellates and ciliates) and significant impacts to higher trophic levels (SAMUELSSON et al, 2002;AUER et al, 2004).In this sense, aquatic communities have been used as descriptors of environmental changes (HIGUTI et al, 2005); especially microorganismal assemblages because of their ability to act as bioindicators of aquatic pollution (FOISSNER, 1992).Due to their small body size, high metabolic rates and short life cycles (DUPUY et al, 2007), the organisms that constitute the microbial food chain respond rapidly to changes in environmental conditions (AUER et al, 2001). In addition, they play an essential role in fast nutrient cycling, the mineralization of organic compounds and the production and transfer of organic matter in aquatic environments (AZAM et al, 1983 Among these microorganisms, the flagellate protozoans are important components, having a significant role in aquatic system metabolism.…”