Transparent Exopolymer Particles (TEP) are found in both
marine and freshwater systems and can have a huge impact on coagulation of
suspended matter, resulting in marine snow that sink rapidly to the benthos (Alldredge
and Silver, 1988). These sinking aggregates can act as a substrate for
bacteria, or as a potential food source for benthic and pelagic organisms (Heinonen,
Ward and Holohan, 2007).
TEP has been seen to be produced by both phytoplankton and
bacteria, however its production by macro-organisms had previously not been
studied. A variety of marine organisms secrete mucopolysaccharides in the form
of mucus sheaths, webs, nets or mucus covered appendages (Heinonen, Ward and
Holohan, 2007). Ward et al., 1993, stated that due to the widespread use of
these mono-polysaccharides, some of this material is probably released in a
dissolved form or is sheared off the organism’s appendages. These mucins are
chemically similar to TEP precursors so may contribute to the TEP pool (McKee
et al., 2005).
Heinonen, Ward and Holohan, 2007, hypothesised that
mucopolysaccharides released by benthic suspension feeders enhance the ambient
concentrations of TEP. DOC may also serve as an indicator of TEP production by
suspension feeders, as TEP forms from dissolved precursors. For this study, individuals
of the blue mussel (Mytilus edulis),
bay scallop (Argopecten irradians),
slipper snail (Crepidula fornicata)
and two species of solitary tunicates (Ciona
intestinalis and Styela clava) were
collected to determine whether these organisms could produce detectable levels
of TEP under controlled conditions.
The results from this study show that all benthic suspension
feeders used in this study enhanced TEP concentrations above background levels
after 5 hours of active feeding. They
measured low bacterial abundance and growth rates throughout the study, so can
assume the heightened TEP levels were not greatly influenced by bacteria. The
two bivalves studied (M. edulis and A. irradians) had the potential to
produce the greatest amount of TEP per unit dry mass, followed by the two
tunicate species (Ciona intestinalis and
Styela clava). They suggest that C. fornicata has the lowest potential to
produce TEP due to it’s feeding mechanisms and use of a high-velocity mucus
which would have lower solubility – so fewer mono-polysaccharides would be
released into the surrounding waters.
The results seen in this study did not support the
hypothesis of DOC concentrations being a good predictor of TEP concentrations,
as only S. clava significantly
enhanced DOC concentrations over background levels after 5 hours. However, they
have been able to show that mono-polysaccharide production by benthic
suspension feeders does contribute to the TEP pool.
This study provided us with a very interesting insight into
the production of TEP by organisms other than plankton and bacteria. In terms
of taking this study further, it seems as though very few studies have looked
into the consumption and degradation of TEP, as well as its distribution away
from the source. This could be important
for learning more about TEP’s role in marine systems, and so may be a useful
direction to take this field of research in.
Studied paper
Heinonen, K., Ward, J., and Holohan, B. (2007). Production
of Transparent Exopolymer Particles (TEP) by Benthic Suspension Feeders in
Coastal Systems. Journal of Experimental
Marine Biology and Ecology, (341), 184-195.
References
Alldredge, A., Passow, U., Haddock, S. (1998). The Characteristics
and Transparent Exopolymer Particle (TEP) Content of Marine Snow Formed from Thecate
Dinoflagellates. Journal of Plankton Research,
(20), 393–406.
McKee, M., Ward, J., MacDonald, B., Holohan, B. (2005).
Production of Transparent Exopolymer Particles (TEP) by the Oyster (Crassostrea virginica). Marine Ecology Progress Series. (248),
141–149.
Ward, J., MacDonald, B., Thompson, R., Beninger, P. (1993).
Mechanisms of Suspension Feeding in Bivalves: Resolution of Current Controversies
by Means of Endoscopy. Limnology and
Oceanography, (38), 265–272.
Hi Megan,
ReplyDeleteThank you for your post, it was very interesting as I had not previously considered the role of macro-organisms in TEP production. You stated that the mucins produced by marine macro-organisms are chemically similar to TEP precursors, did the paper mention if TEP produced by the benthic organisms in this study was the same as TEP produced by phytoplankton and bacteria? Also, were there any comparisons made between the amount of TEP produced by the benthic organisms compared to what is produced by phytoplankton and bacteria?
Thank you
Georgia
Hi Georgia,
DeleteThanks for your question!
The authors state that dissolved high molecular weight polysaccharides are released by microorganisms, such as bacteria and phytoplankton. This DOM is then transformed into POM which is subject to abiotic processes, resulting in the formation of TEP. Many marine invertebrates use mucopolysaccharides for various life processes, and some of these mucopolysaccharides are released in a dissolved form. This DOM then undergoes the same processes as before. I assume that this would result in the same TEP being formed.
The authors do not make a comparison of the amount of TEP produced by benthic macro-organisms organisms compared to micro-organisms, simply that the levels were raised above background levels. I think this would be a really interesting comparison though, and might be a good idea for future studies!
Thanks,
Megan.
Hi Megan,
ReplyDeleteAs you say the role of TEP produced by phytoplankton and bacteria has important impacts on the aggregation and settlement of marine snow, however I was wondering if the authors suggested the role of TEP produced by benthic organisms?
Many thanks,
Amelia
Hi Amelia,
DeleteAs far as I can tell the TEP produced by benthic organisms is the same as TEP produced by micro-organisms such as phytoplankton and bacteria. This would result in the ecosystem roles being the same too.
Thanks for the question!
Megan.
Hi Megan,
ReplyDeleteThank you for the interesting read! Your blog inspired me to further research our current understanding of the role of macro-organisms in TEP production. I have found that, in addition to benthic organisms, it is now known that algal detritus and seagrass leaf litter both generate the necessary precursor molecules for TEP. If you are interested, my most recent blog addresses this subject. For a more in-depth look in to the subject, I encourage you to read a recent paper by Iuculano et al (2017) (reference below) as I feel it will be of interest to you.
Regards,
Ellen
Reference:
Iuculano, F., Duarte, C.M., Marbà, N. and Agustí, S., 2017. Seagrass as major source of transparent exopolymer particles in the oligotrophic Mediterranean coast. Biogeosciences, 14(22), p.5069.
Hi Ellen,
DeleteThank you for the recommendation, I think you found a very interesting paper to review! I have added a question about that particular paper on your blog post.
All the best,
Megan.