Top-down and bottom-up control of infauna varies across the saltmarsh landscape

Responses of infaunal saltmarsh benthic invertebrates to whole-ecosystem fertilization and predator removal were quantified in Plum Island Estuary, Massachusetts, USA. Throughout a growing season, we enriched an experimental creek on each flooding tide to 70 μM NO 3 − and 4 μM PO 4 − 3 (a 10× increa...

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Bibliographic Details
Published in:	Journal of experimental marine biology and ecology Vol. 357; no. 1; pp. 20 - 34
Main Authors:	Fleeger, J.W., Johnson, D.S., Galván, K.A., Deegan, L.A.
Format:	Journal Article
Language:	English
Published:	Amsterdam Elsevier B.V 17-03-2008 Elsevier Science
Subjects:	Animal and plant ecology Animal, plant and microbial ecology Annelida Biological and medical sciences Brackish water ecosystems Copepoda Decapoda Fundamental and applied biological sciences. Psychology Fundulus heteroclitus Impact assessment Indirect effects Marine Ostracoda Prunus Saltmarsh gradient Sea water ecosystems Spartina alterniflora Spartina patens Synecology ANW, USA, Massachusetts Saltmarsh gradient Indirect effects Impact assessment Marine environment Bottom up control Salt marsh Landscape Fauna Top down control Infauna
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Summary:	Responses of infaunal saltmarsh benthic invertebrates to whole-ecosystem fertilization and predator removal were quantified in Plum Island Estuary, Massachusetts, USA. Throughout a growing season, we enriched an experimental creek on each flooding tide to 70 μM NO 3 − and 4 μM PO 4 − 3 (a 10× increase in loading above background), and we reduced Fundulus heteroclitus density by 60% in a branch of the fertilized and a reference creek. Macroinfauna and meiofauna were sampled in creek (mudflat and creek wall), marsh edge (tall-form Spartina alterniflora) and marsh platform ( Spartina patens and stunted S. alterniflora) habitats before and after treatments were begun; responses were tested with BACI-design statistics. Treatment effects were most common in the mid-range of the inundation gradient. Most fertilization effects were on creek wall where ostracod abundance increased, indices of copepod reproduction increased and copepod and annelid communities were altered. These taxa may use epiphytes (that respond rapidly to fertilization) of filamentous algae as a food source. Killifish reduction effects on meiobenthic copepod abundance were detected at the marsh edge and suggest predator limitation. Fish reduction effects on annelids did not suggest top-down regulation in any habitat; however, fish reduction may have stimulated an increased predation rate on annelids by grass shrimp. Interactions between fertilization and fish reduction occurred under S. patens canopy where indirect predator reduction effects on annelids were indicated. No effects were observed in mudflat or stunted S. alterniflora habitats. Although the responses of infauna to fertilization and predator removal were largely independent and of similar mild intensity, our data suggests that the effects of ecological stressors vary across the marsh landscape.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0022-0981 1879-1697
DOI:	10.1016/j.jembe.2007.12.003