Small scale variability of benthic assemblages: biogenic neighborhood effects

Area of Science:

• Marine ecology
• Benthic community structure
• Habitat-forming species interactions

Background:

• Investigating community development in marine ecosystems is crucial for understanding ecological dynamics.
• Habitat-forming species play a significant role in structuring associated communities.
• Previous research has highlighted factors like spatial variability, succession, and competition in shaping benthic assemblages.

Purpose of the Study:

• To determine if the presence of specific habitat-forming species influences the development of benthic assemblages in their vicinity.
• To compare community structure within and outside monospecific habitats of algae, seagrass, and mussels.
• To identify potential mechanisms by which habitat-forming species exert control over local community development.

Main Methods:

• Paired artificial substrata were deployed within (treatment) and outside (control) of five distinct monospecific habitats (Fucus serratus, Delesseria sanguinea, Enteromorpha intestinalis, Zostera marina, Mytilus edulis).
• Colonization and post-settlement dynamics were monitored over 5 months to assess changes in species abundance and assemblage structure.
• Analysis of similarity was used to detect significant differences in assemblage structure between treatment and control sites, accounting for spatial variability.

Main Results:

• While the same colonizer species settled on both treatment and control substrata, their proportional abundance and assemblage structure differed significantly in many instances after 5 months.
• Despite large variability among replicates due to patchy spatial distribution, significantly different benthic assemblages developed on small spatial scales depending on whether substrata were within or outside a habitat.
• The presence of algae, seagrass, or mussels within a habitat appeared to control the structure of the developing benthic assemblage in its vicinity.

Conclusions:

• Habitat-forming species, such as algae, seagrass, and mussels, are significant factors controlling the structure of local benthic assemblages.
• Mechanisms of control may include reduction of larval supply, exudation of metabolites affecting settlement and survival, and predation.
• This study identifies the impact of neighboring organisms as a key assemblage structuring factor, in addition to spatial variability, stochasticity, and competition.