Our
research projects fall into the category of Marine
Chemical Ecology
What
is Chemical Ecology?
Chemical
ecology came to be recognized as a distinct interdisciplinary
research area about three decades ago. It deals with the intriguing
chemical mechanisms which help control intra- and interspecific
interactions among living beings. All organisms use chemical signals
to transmit information; "chemical languages" are the
oldest forms of communication. Research in the field of chemical
ecology is concerned with the identification and synthesis of
the substances which carry information, with the elucidation of
receptor and transduction systems which recognize and pass on
these "semiochemicals", and with the developmental,
behavioral, and ecological consequences of chemical signals.
(from
website of The International
Society of Chemical Ecology)
Add
the prefix "marine" to this definition and subtract
2 of the 3 decades and you're pretty much on track. Marine Chemical
Ecology is a much younger discipline than its terrestrial counterpart.
The main difference is the physicochemical nature of semiochemicals
(i.e. the messenger molecules). Whilst terrestrial semiochemicals
are largely volatile, marine semiochemicals are often comprised
of nonvolatile, water-soluble or surface-associated compounds.
The
following is a list of research projects currently planned in
the Environmental Biochemistry Group.
Chemical
recruitment signals for marine infauna in the Wadden Sea
Similarly
to the recruitment of fouling organisms on hard substrata, many
soft sediment-associated organisms show clear preferences for
a particular type of substratum. In this project, we plan to investigate
the effect of bacteria and cyanobacteria on larval and juvenile
recruitment of typical bottom dwelling polychaete worms in the
Wadden Sea. In the first stage, we plan to characterize and compare
bacterial community profiles on preferred and rejected sediment
surfaces by molecular biological techniques. Subsequently, a small
bacterial culture collection will be established to test the effect
of monospecies bacterial biofilms on recruitment preferences of
selected test organisms. The project will comprise the establishment
of adult broodstocks for the continuos supply with larvae and
juveniles for bioassay purposes. If certain bacteria significantly
stimulate or inhibit larval or juvenile recruitment, it is planned
to isolate and identify the bacteria-derived signal by means of
instrumental chemical analytical techniques. TOP
The
role of cyanobacteria in larval settlement of barnacles and mussels
It
is well documented that larvae of barnacles and many mussels utilize
marine biofilms to locate suitable settlement substrata. While
there is abundant evidence, that bacteria play significant roles
in the mediation of larval settlement, the corresponding role
of cyanobacteria is largely unknown. In this project we plan to
test the effect of cyanobacteria isolated from different hard
substrata in the North Sea on the induction/inhibition of larval
settlement of barnacle and mussel larvae. TOP
Isolation
and identification of aromatic brominated compounds from marine
infauna in the Wadden Sea
A number of infauna (e.g. burrowing worms) are known to release
aromatic brominated compounds into the surrounding sediment. It
has been shown that these compounds act as negative recruitment
cues to larvae of other worm species, i.e. they are repelled to
colonize these sediments. Moreover, it has been shown that the
tube lining of haloaromatic-secreting species contains a significantly
different bacterial community compared to unaffected sediments.
An antibacterial effect of these compounds is postulated. However,
none of these haloaromatics has so far been purified from worms
and structurally elucidated. In this project we will concentrate
on local species and try to provide more specific information
on the aromatic chemistry of infauna in the Wadden Sea. TOP
The
role of biofilm architecture in larval settlement
Upon
contact with a marine substratum, the larvae of marine invertebrates
actively explore surfaces to assess their suitability for permanent
attachment. Substratum suitability is largely determined by environmental
parameters such as tidal height, flow regime and nutrient availability.
Bacteria are sensitive to changes in environmental parameters
and thus the composition and physiology of bacterial communities
in marine biofilms can reflect the local environmental conditions
adjacent to the substratum. In many marine invertebrates, larvae
are able to distinguish between biofilms of varying composition,
physiological condition and growth phase, indicating that bacteria
therein serve as important signposts for larvae seeking settlement
substratum. In this project we plan to extend these investigations
by analyzing physical and physicochemical properties of biofilmed
surfaces and their role in mediating a signal of suitability to
surface-exploring larvae. To study such solid-liquid interfaces,
we plan to describe attached bacterial assemblages by atomic force
microscopy and scanning laser confocal microscopy together with
electrochemical techniques. TOP
Epibiotic
bacteria on green macroalgae and their effect on larval settlement
of fouling organisms
Many
marine plants and sessile invertebrates employ natural antifouling
strategies to prevent bacterial colonization and overgrowth by
other macro-organisms (this process is referred to as epibiosis).
In case of a tropical green macroalga we found that certain surface-associated
bacteria exhibit a potent antifouling effect. This effect is mediated
by macromolecular bacterial secretions. In this project we plan
to test similar effects with local seaweeds abundant in the North
Sea and aim for a comparative study between antifouling effects
of tropical and temperate macroalgae. TOP
