Community dominance by a canopy species controls the relationship between macroalgal production and species richness

Abstract

By field manipulations of nutrients, propagules, and canopy cover in a shallow rocky subtidal, we show that dominance by a leathery macrophyte (Fucus vesiculosus) controls net production and the propagation of nutrient effects on understory algal species richness. On substrates with propagules, canopy cover prevented a significant loss of diversity from nutrient enrichment demonstrated outside canopy cover. On sterile substrates, negative canopy effects on diversity were counteracted by nutrient enrichment. Experimental manipulations produced a significant hump-shaped relationship between species richness and log net production, with low richness at low or high biomass production and highest richness at intermediate biomass production. By strong control of net primary production, canopy cover changed the algal understory community to an alternative production state and thereby generated a switch in the relationship between net primary production and species richness from negative outside canopy cover to positive inside. This demonstrates that species contributing to biological structure and habitat diversity can determine the responses of a coastal ecosystem to resource loading.

Facilitation by ecosystem engineers enhances nutrient effects in an intertidal system

“…However, the physical structure may also limit nutrient uptake by shading associated primary producers (Eriksson et al. , ) or change consumption rates by providing refuge for prey and/or mesopredators (Crain and Bertness , Wright et al. ).…”

Functional traits of marine macrophytes predict primary production

“…Alternatively, macrophyte primary production may be viewed as a product of the combined contribution of each species in a community (Binzer, Sand‐Jensen & Middelboe ; Pärnoja et al . ) such that variation in macrophyte species biomass in a benthic floral community causes variation in total primary production (Eriksson, Rubach & Hillebrand ). Depending on the functional traits of macrophyte species (e.g.…”

“…Traditionally, the rate of benthic primary production has been predicted based on various abiotic and biotic factors such as light, temperature and nutrient availability, efficiency of nutrient uptake and assimilation, as well as by chemical and physical processes within an ecosystem (Best et al 2001;Gattuso et al 2006;Gruner et al 2008). Alternatively, macrophyte primary production may be viewed as a product of the combined contribution of each species in a community (Binzer, Sand-Jensen & Middelboe 2006;P€ arnoja et al 2014) such that variation in macrophyte species biomass in a benthic floral community causes variation in total primary production (Eriksson, Rubach & Hillebrand 2006). Depending on the functional traits of macrophyte species (e.g.…”

Taxonomy of Marine Macroalgae Used as Sources of Bioactive Compounds

“…Some fucalean seaweed (particularly species of Fucus , Ascophyllum , Cystoseira, and Hormosira ) form dense populations in the intertidal zone of many temperate rocky shores, producing almost monospecifi c belts. Due to their relatively large size (20 cm to 2 m in length) they are habitat builders, the presence of which greatly modifi es the colonized environment and promotes biological diversity (Eriksson et al 2006 ;Mangialajo et al 2008 ) ; the belts of Fucus in the northern Atlantic, Cystoseira in the Mediterranean and Black Seas and Hormosira in Australia and New Zealand are well-known examples. Several species of fucalean algae and their extracts are used for many applications (fertilizers, food products, drugs, cosmetics), and for this reason they are harvested commercially in several countries (Briand 1991 ) .…”