[L&O Featured Article]L&O Vol. 45, No. 6 (September 2000): Featured Article now available

[lo-feature-admin@aslo.org]

The featured article in the September 2000 issue of L&O is:

"The fate of intertidal microphytobenthos carbon: An in situ 13C-labeling 
study" by Middelburg, Jack J., Christiane Barranguet, Henricus T. S. 
Boschker, Peter M. J. Herman, Tom Moens, and Carlo H. R. Heip. It will 
appear in Limnol. Oceanogr. 45(6): 1224-1234.

This article is freely available on the Web at

          http://aslo.org/lo/toc/vol_45/issue_6/1224.pdf

Instructions for reading PDF files are located on the ASLO web page:

          http://aslo.org/help/loonline.html

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Introductory comments by Raymond Hesslein (L&O Associate Editor)

The role of microbenthos in the cycling of carbon in shallow sediments is 
widely thought to be important, but few studies have quantitatively 
demonstrated this or shown the details of carbon dynamics. Stable isotope 
data have shown that carbon fixed in the benthic zone can be important to 
higher trophic levels in the pelagic zone, but the details of the transfers 
involved have not been thoroughly examined. Shallow sediments are also a 
potentially important location for the respiration of carbon produced in 
the pelagic zone and allochthonously; but quantifying the relative 
contributions of these different sources has proved to be difficult; this 
difficulty derives in part from the poorly defined relationship between the 
often large standing stock of benthic carbon and rates of photosynthesis 
and respiration. These and many other processes have remained unresolved 
because of the challenge of studying benthic communities experimentally.

Middelburg et al. combine the elegant technique of in situ 13C labeling 
with careful measurement of a number of carbon pools and detailed 
information about the study area from other publications. Their results 
elucidate many benthic processes, including: Photosynthetic uptake based on 
13C accumulation was 24 times lower than uptake of 14C in slurries, 
suggesting that benthic photosynthesis was limited by inorganic carbon 
availability in the overlying boundary layer. Turnover of the carbon pools 
was rapid (peak labeling of the diatoms and bacteria was reached at about 
24 hours). Organic 13C label moved rapidly below the euphotic zone in the 
sediment. Nematodes were labeled within a few hours and were found below 
the depth of labeled diatoms, indicating rapid vertical movement of benthic 
animals. These and other results confirm the central role of 
microphytobenthos in moderating carbon flow in coastal sediments.

Both reviewers were highly complementary in concluding that these findings 
were "both interesting and novel" and that "the manuscript is one of the 
most important contributions to this area that I have ever seen." I expect 
(and certainly hope) that this exciting paper will stimulate others to 
carry out similar studies on benthic communities elsewhere.