Constraints on body size distributions: an experimental approach using a small-scale system.

Area of Science:

• Marine ecology
• Ecological dynamics
• Benthic ecosystems

Background:

• Ecological systems exhibit structure influenced by biotic and abiotic processes.
• Discontinuities in these processes may drive system structure, as proposed by Holling (1992).
• Benthic communities are complex and respond to environmental changes.

Purpose of the Study:

• To experimentally test Holling's (1992) proposition regarding discontinuities and ecological structure.
• To investigate the impact of size-specific perturbations on marine sediment assemblages.
• To determine if the benthic biomass or abundance size spectrum is sensitive to these perturbations.

Main Methods:

• Marine sediment assemblages were subjected to two types of size-specific perturbations: organic enrichment and predation.
• Each perturbation was applied at two distinct levels.
• Effects on invertebrate taxa densities, relative abundance, benthic biomass, and abundance size spectrum were analyzed.

Main Results:

• Perturbations significantly altered the densities and relative abundance of key invertebrate taxa.
• Observed effects were consistent with known impacts of organic enrichment and predation.
• Little evidence indicated significant treatment effects on the overall benthic biomass or abundance size spectrum.

Conclusions:

• The benthic biomass and abundance size spectrum appear conservative, likely constrained by habitat architecture.
• While specific taxa are sensitive to perturbations, the overall size spectrum may be resilient.
• Experimental evidence partially supports Holling's proposition, highlighting the role of habitat structure in ecological organization.