The role of highly unsaturated fatty acids in aquatic foodweb processes

1
The role of highly unsaturated fatty acids in
aquatic foodweb processes

• published by BRETT MÜLLER-NAVARRA (1997),
  Freshwater Biology

by Björn Gröper 12.5.09
2
Content

• Aims of this study
• General information about foodweb dynamics and
  HUFA biochemistry
• Zooplankton growth
• Impact of HUFA on animal physiology and nutrition
• Sources of FA and phytoplankton food quality
• Example (food pyramids)
• Potential role of HUFA in aquatic foodwebs

3
1. Aims of the study

• This paper should summarize a body of
  information about the role of unsaturated FA in
  aquatic foodweb
• It should also underline that HUFA are compounds
  with key regulatory roles for animals (nutrition,
  physiology)
• Potential use of this information

4
2. General Information

• Basic process ?transfer of energy from one
  trophic level to another
• Energy flow from plants to herbivores and to
  predators
• Fundamental is phytoplankton, limited by
  nutrients or sometimes light
• Flow of energy across the plant-animal interface
  is variable (efficiency)
• Fatty acids
• -can be saturated (SAFA)or unsaturated (UFA),
  (depending on double bonds)
• -UFA are synthesized from SAFA introducing double
  bonds by enzymes (desaturases), some UFA are only
  produced by plants and algae (linolenic acid)
• -important for this study eicosapentaenoic acid,
  docosahexaenoic acid

5
3. Zooplankton growth
Example Schöhsee,Germany ?experiment to measure
zoopl.biomass and quality of lake seston
-strong correlation between Daphnia growth and
seston eicosapentaenoic acid -EPA determined
seston food-quality
6
4. Impact of HUFA on nutrition and physiology
-SAFA are used as a source or storage form of
energy -PUFA are not primarly used for energy
storage -PUFA have an impact on cell membrane
fluidity ?HUFA-rich diets are essential for
marine and freshwater fishes, molluscs and
crustaceans ?they impact survival,growth,feed
conservation,fecundity,osmotic stress balance
7
5. Sources of FA and phytoplankton food-quality
-the important FA linolenic acid and linoleic are
only produced by plants -EPA and DHA are
produced by plants or converted from linolenic
acid -seston HUFA content determines foodweb
efficiency and secondary production -phytoplankto
n FA content varies between taxonomic groupings
8
5. Sources of FA and phytoplankton food-quality
Diatoms ?high proportions of EPA DHA ?low
linolenic linoleic acid Cryptophytes ?high EPA
DHA, high 182 183 Chlorophytes ?lack of
EPA DHA, high 182 183 Cyanophytes ?no DHA
EPA, very little 182 183 ?general low FA
content
9
5. Sources of FA and phytoplankton food-quality
-this shows that there is a hierachy in
phytoplankton food-quality which is based on
these FA and also on the digestibility
food-quality 1.diatoms cryptophytes 2.green
algae 3.cyanobacteria
10
6. Example (food pyramids)
-hypereutrophic aquatic ecosystems are
characterized by high phytoplankton biomass and
relatively low zooplankton -marine upwelling
zones can have inverted food pyramids with more
zooplankton biomass than phytoplankton
Reasons Peruvian Upwelling is diatom-dominated ?g
ood quality(HUFA), easier to gaze,converted
efficiently ?results in higher zooplankton
biomass and fish production
11
7. Potential role of HUFA in aquatic foodwebs
?these information can be used to control the
processes between plant production and
herbivores ?increase fisheries production ?restore
lakes biologically by stimulating the growth of
HUFA-rich diatoms and cryptophytes ?seston HUFA
content is a potential index for secondary
production
12
Thank you for your attention!!!