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Oecologia

Title:		Upward cascading effects of nutrients: shifts in a benthic microalgal community and a negative herbivore response
Author(s):		Armitage AR; Fong P;
Address:		"Department of Organismic Biology, Ecology and Evolution, University of California Los Angeles, 621 Charles E. Young Dr. South, Los Angeles, CA 90095-1606, USA. armitage@fiu.edu"
Journal Title:		Oecologia
Year:		2004
Volume:		20040310
Issue:		4
Page Number:		560 - 567
DOI:		10.1007/s00442-004-1530-6
ISSN/ISBN:		0029-8549 (Print) 0029-8549 (Linking)
Abstract:		"We evaluated the effects of nutrient addition on interactions between the benthic microalgal community and a dominant herbivorous gastropod, Cerithidea californica (California horn snail), on tidal flats in Mugu Lagoon, southern California, USA. We crossed snail and nutrient (N and P) addition treatments in enclosures on two tidal flats varying from 71 to 92% sand content in a temporally replicated experiment (summer 2000, fall 2000, spring 2001). Diatom biomass increased slightly (approximately 30%) in response to nutrient treatments but was not affected by snails. Blooms of cyanobacteria (up to 200%) and purple sulfur bacteria (up to 400%) occurred in response to nutrient enrichment, particularly in the sandier site, but only cyanobacterial biomass decreased in response to snail grazing. Snail mortality was 2-5 times higher in response to nutrient addition, especially in the sandier site, corresponding to a relative increase in cyanobacterial biomass. Nutrient-related snail mortality occurred only in the spring and summer, when the snails were most actively feeding on the microalgal community. Inactive snails in the fall showed no response to nutrient-induced cyanobacterial growths. This study demonstrated strongly negative upward cascading effects of nutrient enrichment through the food chain. The strength of this upward cascade was closely linked to sediment type and microalgal community composition"
Keywords:		*Animal Nutritional Physiological Phenomena Animals *Bacterial Physiological Phenomena Biomass California Diatoms/*physiology *Ecosystem Food Chain Geologic Sediments/analysis Marine Biology Seasons Silicon Dioxide Snails/*physiology;
Notes:		"MedlineArmitage, Anna R Fong, Peggy eng Comparative Study Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, Non-P.H.S. Germany 2004/03/12 Oecologia. 2004 May; 139(4):560-7. doi: 10.1007/s00442-004-1530-6. Epub 2004 Mar 10"