Interactions between meiofauna and mat-forming microbes at the sediment-water interface - implications for benthic-pelagic coupling in coastal systems

Updated 2003-07-11

The project investigated small-scale biotic interactions between laminated microbial communities and meiofauna at light-exposed sediment-water boundaries of estuarine lagoons. The production and biological structure of these systems is mainly determined by complex processes at the sediment-water interface which depend on finely scaled patterns, requiring appreciation of how the biota interact within these scales. We tested whether changing light conditions and active emergence of the harpacticoid species Mesochra lilljeborgi and Tachidius discipes are mediated by the activity of benthic oxygenic and anoxygenic phototrophic microbes. Two hypotheses were tested which addresses to the question of causality between changing light conditions and active emergence of the harpacticoid copepods. (1)The harpacticoid copepods T. discipes and M. lilljeborgi will enter the bottom water during daylight when oxygenic photosynthesis of cyanobacteria and eukaryotic algae is blocked and conditions at the sediment-water interface have turned anoxic. (2)Both species will not emerge during dark exposures when transferred to sterilized sediments.

Time frame

Status
Completed
Project time span
1998 - 2000
Data collection
2000 - 2000
Data processing
not specified
Data reporting
not specified

Contact information

Contact person
Kay C. Vopel
Address
Department of Marine Biology Institute of Ecology and Conservation Biology University of Vienna Althanstr. 14 A-1090 Vienna Austria
Phone
+43 1313361316
Fax
+43 131336778
Email
ed.nevahremerb-iwa@lepovk

Parameters and Media

Parameter groups measured/observed/modelled
Biological effects
Media sampled/studied/modelled
Marine benthos
Plankton (zooplankton)

Geography

Regions studied
Kristineberg Marine Research Station
Sweden

Data availability

Samples/specimens archived in specimen banks?
No

Methods & Procedures

Procedures and methodology used for, e.g., sampling and sample storage, sample pretreatment, extraction and analysis, including which laboratories are involved, references to methods employed, etc.

We successfully tested the hypotheses by means of laboratory light-dark shift experiments. The experiments were carried out using sulphide-rich sediment samples from a sheltered shallow water locality and accompanied by microsensor measurements of oxygen and hydrogen sulphide. Furthermore a novel amperometric hydrogen sulphide microsensors (AMT, Germany) was applied for continuous in situ measurements. The effects of light, oxygen and hydrogen sulphide on emergence patterns were investigated by counts of abundance of harpacticoid species swimming in the water column above constant amounts of sediment. Oxygenic photosynthesis was blocked by use of the selective inhibitor DCMU (3-(3,4-Dichlorphenyl)-1,1-dimethylharnstoff), which specifically effect eukaryotic algae and cyanobacteria. The effects of the inhibitors on light dependent CO2 fixation process was tested separately by means of microelectrode techniques. The experiments verified hypothesis (1). Hypothesis (2) was rejected. Active nocturnal emergence under zero-flow conditions is probably triggered by a combination of both factors, light and oxygen availability. Our ongoing faunistic analyses will provide information about species-, sex- and age-specific responses to the above mentioned factors.

Additional Information

Is this a bi- AND multi-lateral project (i.e. a project involving cooperation between different countries)?
No
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