Foundation species patch configuration mediates salt marsh biodiversity, stability and multifunctionality

Abstract

Foundation species enhance biodiversity and multifunctionality across many systems; however, whether foundation species patch configuration mediates their ecological effects is unknown. In a 6-month field experiment, we test which attributes of foundation species patch configuration - i.e. patch size, total patch area, perimeter, area-perimeter ratio, or connectivity - control biodiversity, stability and multifunctionality by adding a standardised density of mussel foundation species in patches of 1, 5, 10, 30, 60, 90 or 180 individuals to a southeastern US salt marsh. Over 67% of response variables increased with clustering of mussels, responses that were driven by increases in area-perimeter ratio (33%), decreases in perimeter (29%), or increases in patch size (5%), suggesting sensitivity to external stressors and/or dependence on foundation species-derived niche availability and segregation. Thus, mussel configuration - by controlling the relative distribution of multidimensional patch interior and edge niche space - critically modulates this foundation species' effects on ecosystem structure, stability and function.

Sea-level rise and the emergence of a keystone grazer alter the geomorphic evolution and ecology of southeast US salt marshes

“…4 C ) could be explained by variation in predation pressure. We deployed mussels in aggregations to mimic their natural, clustered distribution ( 60 , 61 ) in the border and platform zones of grazed and ungrazed marshes, paired within three Sapelo Island, GA, sites ( n = 8 mussel aggregations each per marsh type and zone; see SI Appendix , Table S3 and Fig. S5 for site information and physical characteristics), and recorded mussel mortality due to predation.…”

“…To test whether mussel survival differed in marshes adjacent to grazed and ungrazed creeks, we transplanted mussels to mimic their natural distribution in dense aggregations (61). At each of the grazed and ungrazed creeks at the Sapelo Island sites, we transplanted mussels into aggregations of 15 individuals (three from each of five size classes: 30 to 39, 40 to 49, 50 to 59, 60 to 69, and 70 to 79 mm) in the border and platform zones.…”

Facultative mutualisms: A double‐edged sword for foundation species in the face of anthropogenic global change

“…Changes made to an already suitable habitat via self‐facilitation will yield little overall improvement in living conditions. By contrast, self‐facilitation can be essential to a foundation species’ survival, growth, and reproduction in hostile conditions, by alleviating physical or biotic stress and thereby extending the foundation species’ own realized niche (Bruno et al., 2003; Crotty et al., 2018; He & Bertness, 2014). Examples of ecosystems where foundation species benefit from positive density dependence include tropical forest and desert vegetation that mediate water availability by creating a humid microclimate to stimulate plant growth (Hirota et al., 2011; Rietkerk et al., 2004); coral and shellfish reefs that facilitate settlement of additional coral and shellfish recruits by providing hard structures (Schulte et al., 2009); and seagrasses, salt marsh plants, and mangroves that enhance their own growth by stabilizing sediments, and trapping suspended particles to locally enhance nutrient availability (Balke et al., 2011; Zemp et al., 2017) (see Table 1 for further examples).…”

Facultative mutualisms: A double-edged sword for foundation species in the face of global change

“…Changes made to an already suitable habitat via self-facilitation will yield little overall improvement in living conditions. By contrast, self-facilitation can be essential to a foundation species' survival, growth and reproduction in hostile conditions, by alleviating physical or biotic stress and thereby extending the foundation species' own realized niche (Bruno et al 2003;Crotty et al 2018). Examples of ecosystems where foundation species benefit from positive density-dependence include tropical forest and desert vegetation that mediate water availability by creating a humid microclimate to stimulate plant growth (Rietkerket al 2004;Hirota et al 2011); coral and shellfish reefs that facilitate settlement of additional coral and shellfish recruits by providing hard structures (Schulte et al 2009); and seagrasses, salt marsh plants, and mangroves that enhance their own growth by stabilizing sediments, and trapping suspended particles to locally enhance nutrient availability (Balke et al 2011;Zempet al 2017) (see Table S1 for further examples).…”