[Lo-Feature] December 1999 L&O Featured Article now available

[Everett Fee]

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

"Effects of nutrients versus herbivores on reef algae:  A new method for 
manipulating nutrients on coral reefs" by Miller, M. W., M. E. Hay, S. L. 
Miller, D. Malone, E. E. Sotka, and A. M. Szmant. It will appear in 
Limnology and Oceanography 44(8): 1847-1861.

This article is freely available at the Web address:

          http://aslo.org/lo/toc/vol_44/issue_8/1847.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 Michael P. Lesser (L&O Associate Editor)

Recently in the pages of Limnology and Oceanography, and amongst 
coral reef biologists worldwide, a vigorous discussion has been 
occurring about what controls macroalgal abundance on coral reefs. The 
two sides of this debate have been designated as "bottom-up" versus 
"top-down," well-known jargon terms that have been hotly discussed by 
ecologists working on many different ecosystems. The nub of the 
present controversy is whether algal blooms on reefs are kept in check 
by herbivory (Hughes et al.1999) or nutrients (Lapointe 1997, 1999). 
Each camp nominally recognizes the potential role of the process 
advocated by the other, but neither has gone so far as incorporating the 
process promoted by the other in their own research design. The debate 
has been further complicated by the lack of  rigorous multifactorial field 
experiments that examine both herbivory and nutrient effects in the field.

This month's featured L&O paper by Miller et al. (1999) makes an 
important contribution to this debate. The experimental design is 
multifactorial (herbivory and nutrients), well replicated (i.e., not 
psuedoreplicated), and appropriately analyzed, despite equipment 
failures that occurred during the study. An particularly interesting 
aspect of the paper is its unique method of adding nutrients to the 
various treatments: commercial fertilizer spikes (available at your 
garden store) were partially covered in paraffin and entombed in cinder 
blocks containing holes that permitted nutrients to diffuse into the 
environment.

The results of these experiments do not support the "bottom-up" model 
of Lapointe (1997), and a similar result was obtained by yet another 
paper on this subject that will appear in the next (January 2000) issue of 
L&O (Aronson and Precht, in press). While these two recent L&O 
papers clearly tip the "top-down" versus "bottom-up" debate in favor of 
the former hypothesis, it is unlikely that we have heard the last word on 
the subject. The Aronson and Precht paper (in press) suffers from being 
an uncontrolled "natural experiment" at a Jamaican reef site that has 
had repeated disturbances, both natural and anthropogenic, that 
complicate the interpretation. Moreover, some of the results and 
analyses in Miller et al. (1999) are not as "clean" as many would like. 
Most likely, "truth" lies somewhere between the "top-down" and "bottom-
up" polarities and varies temporally and geographically.

This is not just an ivory-tower debate that does not concern the "real 
world." The Miller et al. (1999) study was done in the Florida Keys, a 
highly visible site where water quality is declining and reefs are being 
degraded at alarming rates. The unfortunate tendency of the "top-down" 
and "bottom-up" camps to vigorously defend their respective positions 
may confuse the public and policy makers and thwart the widespread 
desire to correct these serious problems. By publishing the papers 
listed below, L&O has taken a leading role in resolving this important 
debate. I sincerely hope that L&O readers -- including the authors of 
these several papers -- can work together to resolve this debate and 
give positive direction to the public's concern. Please read all of these 
papers in chronological order. Then sit down to discuss this important 
issue with your students and colleagues, and share your insights with 
the world by posting them on the LO-Feature Web forum on this 
month's featured article.

References:

Aronson, R. B., and W. F. Precht. In press. Herbivory and algal 
dynamics on the coral reef at Discovery Bay, Jamaica. Limnol. 
Oceanogr.

Hughes, T., A. M. Szmant, R. Steneck, R. Carpenter, and S. Miller. 
1999. Algal blooms on coral reefs: What are the causes? Limnol. 
Oceanogr.  44: 1583-1586.

Lapointe, B. E. 1997. Nutrient thresholds for bottom-up control of 
macroalgal blooms on coral reefs in Jamaica and southeast Florida. 
Limnol. Oceanogr. 42: 1119-1131.

Lapointe, B. E. 1999. Simultaneous top-down and bottom-up forces 
control macroalgal blooms on coral reefs (Reply to the comment by 
Hughes et al.). Limnol. Oceanogr 44: 1586-1592.

Miller, M. W., M. E. Hay, S. L. Miller, D. Malone, E. E. Soka, and A. 
M. Szmant. 1999.  Effects of nutrients versus herbivores on reef algae: 
A new method for manipulating nutrients on coral reefs. Limnol. 
Oceanogr 44: 1847-1861.

~^~^~^~^~^~^~^~^~^~^~^~^~^~
Everett Fee, editor-in-chief
Limnology & Oceanography
343 Lady MacDonald Crescent
Canmore, Alberta  T1W 1H5  CANADA
voice: 403/609-2456, fax: 403/609-2400
E-mail: <lo-editor@aslo.org>
http://www.ucalgary.ca/~efee