Articles published in March, 2007

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Selective attraction and reproductive performance of a harpacticoid copepod in a response to biofilms

Hans-Uwe Dahms, Tilmann Harder, Pei-Yuan Qian

Abstract
The relationship between monobacterial films and the preference of harpacticoid copepods for such films was investigated using still water multiple-choice assays with natural biofilm and sterile conditions as controls. Adult Schizopera sp. were most attracted by a heterogeneous natural biofilm, followed by monospecies-biofilms of Rhodovulum sp., Vibrio proteolyticus, and Flexibacter sp. The preferred bacterial films stemmed from different phylogenetic and physiological groups. The results indicated that the harpacticoid Schizopera sp. was effectively and differentially attracted by bacterial films. Since bacteria constitute a substantial portion of the organic carbon available at the sea bottom as nutritive sources for harpacticoid copepods, we subsequently examined the influence of 9 bacterial strains and a natural biofilm as a nutrient source on the growth and reproductive performance of
ontogenetic stages (nauplii and copepodids) of Schizopera sp. The food value of bacterial strains was assayed in terms of life table data that provided growth parameters. All variables were affected by the type of food offered. A diet on Rhodovulum sp. resulted in optimal growth performance of nauplii and copepodids demonstrating that bacteria can be used as a sole diet to support postembryonic development. The present study is the first to link behavioral preferences to bacterial biofilms with life history parameters when cultivating harpacticoid copepods on the same bacterial strains as the only diet. This study revealed a discrepancy between the biofilm favored (natural biofilm) and the one leading to maximal reproductive performance (monobacterial film of Rhodovulum sp. MB253) as indicated by major life table data as net reproductive rate (Ro), mean generation time (Tm), and capacity for increase (rc).

DAHMS ET AL 2007

The faunal role in the degradation of the common intertidal salt marsh plant Scirpus maritimus

A. I. Lillebø Æ M. R. Flindt Æ M. A. Pardal Æ
P. G. Cardoso Æ S. M. Ferreira Æ J. C. Marques

Abstract
The aim of this work was to evaluate the role of different environmental conditions (oxic and anoxic), and the presence of macrofauna and/or meiofauna during the different steps of Scirpus maritimus L. decomposition/mineralization under controlled laboratory conditions. The results showed no significant differences between the anaerobic and the aerobic degradation of plant material, under the presence of bacteria or meiofauna. Nevertheless, under anoxic conditions sediment mineralization was enhanced, with an increase concentration of phosphorus and ammonium in the water phase. Concerning the presence of fauna, results show that, although bacterial activity was responsible for 70% of the S. maritimus leaves degradation, the presence of macrofauna together with meiofauna enhanced the leaves mineralization up to 90%. Moreover, the presence of macrofauna together with meiofauna significantly affected the decomposition of phosphorus and of nitrogen,as well as the leaves lesser labile structural parts, by increasing the mineralization of plant carbon, and raised the nutrient turnover within the system.The present study reinforces the functional link between fauna levels on the nutrient dynamics in salt marshes ecosystems, namely at the vegetation detritus/water column interface.

LILLEBO ET AL 2007

Sublittoral meiofauna with particular reference to nematodes in the southern Yellow Sea, China

Xiao-Shou Liu, Zhi-Nan Zhang, Yong Huang

Abstract

Densities of major meiofaunal taxa were investigated at 34 sampling stations during six cruises by R/V Beidou to the southern Yellow Sea, China from 2000 to 2004, and the community structure of free-living marine nematodes was studied during one of the cruises in 2003. Meiofauna abundance ranged from 487.4 to 1655.3 individuals per 10 cm2. Nematodes and harpacticoid copepods were the two most dominant groups, contributing 73.8e92.8% and 3.5e18.7%, respectively, to the total meiofauna abundance. One-way ANOVA showed no significant annual fluctuation of meiofauna and nematode abundances from 2000 to 2004 in the southern Yellow Sea. However, two-way ANOVA based on six stations sampled in 4 years (2001e2004) showed that there were significant differences among the six stations and the 4 sampling years for meiofauna, nematode and copepod abundance. Correlation analysis demonstrated that meiofauna abundance was mainly linked to chloroplastic pigments. Other environmental factors could not be ruled out, however. A total of 232 free-living marine nematode species, belonging to 149 genera, 35 families and 4 orders, were identified. The dominant species in the sampling area were the following: Dorylaimopsis rabalaisi, Microlaimus sp.1, Prochromadorella sp., Promonohystera sp., Cobbia sp.1, Daptonema sp.1, Leptolaimus sp.1, Halalaimus sp.2, Aegialoalaimus sp., Chromadorita sp., Parodontophora marina, Parasphaerolaimus paradoxus, Quadricoma sp.1, Campylaimus sp.1, Halalaimus gracilis, Paramesacanthion sp.1, Paramonohystera sp.1, and Metalinhomoeus longiseta. CLUSTER and SIMPROF analyses revealed three main types of nematode community (or station groups) in the sampling area, including I: coastal community, II: transitory community between coastal and YSCWM (Yellow Sea Cold Water Mass), and III: YSCWM community. Each community was indicated by a number of dominant nematode species. Bio-Env correlation analysis between the nematode community and environmental variables showed that water depth, sediment water content, organic matter, chlorophyll a (Chl-a) and phaeophorbide a (Pha-a) were the most important factors to determine the community structure.

LIU ET AL 2007