Changes in coastal benthic algae succession trajectories and assemblages under contrasting nutrient and grazer loads

FRICKE, A; ALVAREZ, FERNANDA; KOPPRIO, G.A.; ALEMANY, D; GASTALDI, M; NARVARTE, M; PARODI, E.R.; LARA, R; F. HIDALGO; MARTINEZ, E.A.; SAR, E; O. IRIBARNE,

ESTUARIES AND COASTS

SPRINGER

Lugar: Berlin; Año: 2016 vol. 39 p. 462 - 477

1559-2723

Eutrophication plays a crucial role in coastal systems,driving changes in the composition and abundance offlora and fauna with consequent effects for the entire ecosystem.Sensitive to nutrient levels, micro- and macroalgalblooms serve as valuable indicators of eutrophication. TheSan Antonio Bay (Northern Argentinean Patagonia, 40° 43′S, 64° 56′ W) provides an appropriate system to study in situeutrophication processes on coastal communities. In a multiscaleapproach, using two different kind of settlement substrates(micro: polyethylene terephthalate, and macro: ceramic),the present study followed benthic algal dynamics overone year, distinguishing changes in natural succession andseasonality. Strong differences were found in the biofilm assemblagesafter three days, marked by tube dwelling diatomsand Cocconeis spp. under high nutrient-grazer conditions andneedle like diatoms (e.g. Nitzschia spp., Tabularia spp.) underlower nutrient-grazer loads. The succession continued by thecolonization of macroalgae, with a higher recruitment rate inthe nutrient and grazer rich environment with a concomitanthigher diversity. Our results show that under higher nutrientgrazerconditions natural benthic succession not only differsin trajectory but in its final taxa composition promotinghigher biodiversity and biomass accumulation. In addition,taxa specific substrate preferences interfere with the observedeutrophication pattern, suggesting substrate dependantinterrelations between the bloom forming taxa. Thesefindings provide evidence that nutrient enrichment can notonly affect an established assemblage but also affect theearly succession stages, changing the succession trajectoryand thus the final assemblage.