Seasonal variability in bacterial abundance, production and protistan bacteriv

ory in the lowerUrdaibai estuary, Bay of Biscay

西班牙畢斯蓋灣 Urdaibai 下游河口細菌數量 .生產力與原生生物攝食細菌的季節性變化

Arantza Iriarte*, Aitziber Sarobe, Emma Orive

AQUATIC MICROBIAL ECOLOGY

Vol. 52: 273–282, 2008

Reporter: Sheng-Hsuan Wu

Introduction

virus

Physical factorsex. temp. supply of substrate(Revilla et al. 2000, Schultz et al. 2003, Staroscik & Smith 2004)

In many estuaries, temperature has been shown to exert a strong influence on bacterial activity (Schultz et al. 2003, McManus et al. 2004, Staroscik & Smith, 2004).

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Seasonal variations in bacterial abundance and production rates were measured in thisestuarine zone in a previous work (Revilla et al. 2000).Bacterivory rates were measured in another studyconducted in May 2001 (Iriarte et al. 2003).

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Materials and Methods

May 1998 – May 1999

Inorganic nutrientsNitrate, ammonium and phosphate

Abundance of heterotrophic microbial planktonCiliates, small HNF (1-8μm) and heterotrophic bacteria

Bacterial production and bacterivoryTdRRadioactively labelled bacteria (RLB)

Chl a (<1, 1-8, 8-100 μm), PP and extracellular release of carbon (ERC)

Bacteria and protozoa counts

a. Bacteria

b. Heterotrophic flagellates

Glutaraldehyde(1%)

1-2ml

10-20ml

DAPI 染色

0.2µm

0.8µm

固定

• 利用 3H-thymidine標定細菌的方式得出細菌的成長與耗損

3H

90 min

以 NaOH 固定

過濾

磨碎閃爍計數儀計數

0.2 µm 濾膜

Results and Discussion

Seasonal variation in bacterial production

Seasonal variation in bacterial production

A similar pattern has been observed in other low productivity, high salinity estuarine zones (e.g. the lower Schelde estuary, Goosen et al. 1997)

Seasonal variation in bacterial production

Seasonal variation in bacterivory

This appears to be a general trend in the marine environment (Wikner et al. 1990, Weisse 1999, Ichinotsuka et al. 2006)

Seasonal variation in bacterivory

Grazing and subtrate control of heterotrophic nanoflagellate abundance

Gasol & Vaqué (1993)

Conclusion

Substrate supply exerts a more important control than temperature on BP and growth.

Small HNF consumed larger amounts of bacteria than ciliates did, but bacteria were not the only food supply for small HNF.

Small HNF consumed larger amounts of bacteria than ciliates did, but bacteria were not the only food supply for small HNF.

Small HNF were largely under a substrate supply (bottom-up) control.

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The End! Thank you~