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<p>Human activities and their products, such as ammonium, influence fundamental ecological processes like seaweed competition, shaping the community’s structure and function. Perennial fucalean species, exposed to increasing nutrient levels, are often replaced by semi-perennial, congeneric species, jeopardizing the sustainability of vital ecosystem services. In the Mediterranean Sea, perennial <i>Ericaria barbatula</i> forests are being replaced by semi-perennial <i>Cystoseira compressa</i> forests. In this study we compared the effects of ammonium concentration and exposure time on the physiology of both species. Upper thallus segments were treated under laboratory conditions to evaluate the effects of ammonium on biological levels: biochemical (pigments, C:N:P ratio), biophysical (JIP-test), and organismal (relative growth rate - RGR, dry/wet biomass). The results were analyzed using factorial and multifactorial statistics. <i>Ericaria barbatula</i> and <i>C.</i> <i>compressa</i> showed distinct resource allocation patterns in response to ammonium concentrations, consistent with their classification into Ecological Status Groups (ESG). The faster initial growth rate, lower dry-to-wet biomass ratio, and higher ammonium affinity observed in <i>C.</i> <i>compressa,</i> compared to <i>E.</i> <i>barbatula,</i> may explain differences in fitness and competitive ability under low to moderate ammonium concentrations along the Mediterranean coasts. <i>Ericaria barbatula</i> tolerated ammonium stress by reallocating metabolic resources from growth toward <i>β</i>-carotene synthesis, thereby prioritizing defense mechanisms rather than biomass accumulation. In contrast, <i>C.</i> <i>compressa</i> experienced chronic photoinhibition (low F<sub>v</sub>/F<sub>m</sub>) and death (ca. 53 % EC<sub>50</sub> RGR decrease day<sup>-1</sup>), mainly caused by donor-side limitation (K-band) and irreversible damage to thylakoid membranes (L-band). These findings have important implications for macroalgal monitoring, restoration, and aquaculture.</p>

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The effects of ammonium chloride on photosynthesis and growth of Ericaria barbatula and Cystoseira compressa (Fucales): Ecological and aquaculture implications

  • 期刊论文

  • 发表日期：

    2026年6月15日

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  • K. Nakou,
  • L. Malea,
  • A. Papadimitriou,
  • S. Orfanidis

摘要

Human activities and their products, such as ammonium, influence fundamental ecological processes like seaweed competition, shaping the community’s structure and function. Perennial fucalean species, exposed to increasing nutrient levels, are often replaced by semi-perennial, congeneric species, jeopardizing the sustainability of vital ecosystem services. In the Mediterranean Sea, perennial Ericaria barbatula forests are being replaced by semi-perennial Cystoseira compressa forests. In this study we compared the effects of ammonium concentration and exposure time on the physiology of both species. Upper thallus segments were treated under laboratory conditions to evaluate the effects of ammonium on biological levels: biochemical (pigments, C:N:P ratio), biophysical (JIP-test), and organismal (relative growth rate - RGR, dry/wet biomass). The results were analyzed using factorial and multifactorial statistics. Ericaria barbatula and C. compressa showed distinct resource allocation patterns in response to ammonium concentrations, consistent with their classification into Ecological Status Groups (ESG). The faster initial growth rate, lower dry-to-wet biomass ratio, and higher ammonium affinity observed in C. compressa, compared to E. barbatula, may explain differences in fitness and competitive ability under low to moderate ammonium concentrations along the Mediterranean coasts. Ericaria barbatula tolerated ammonium stress by reallocating metabolic resources from growth toward β-carotene synthesis, thereby prioritizing defense mechanisms rather than biomass accumulation. In contrast, C. compressa experienced chronic photoinhibition (low Fv/Fm) and death (ca. 53 % EC50 RGR decrease day-1), mainly caused by donor-side limitation (K-band) and irreversible damage to thylakoid membranes (L-band). These findings have important implications for macroalgal monitoring, restoration, and aquaculture.