Differential effects of pollution on adult and recruits of a canopy-forming alga: implications for population viability under low pollutant levels

Sònia De Caralt,Emma Cebrian,Jana Verdura,Enric Ballesteros,Enric Ballesteros,Emma Cebrian,Alba Vergés

doi:10.1038/s41598-020-73990-5

Sònia De Caralt, Emma Cebrian + Show 5 more

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https://doi.org/10.1038/s41598-020-73990-5

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Abstract

Marine macroalgal forests are highly productive and iconic ecosystems, which are seriously threatened by number of factors such as habitat destruction, overgrazing, ocean warming, and pollution. The effect of chronic, but low levels of pollutants on the long-term survival of the canopy-forming algae is not well understood. Here we test the effects of low concentrations (found in good quality water-bodies) of nitrates, heavy metals copper (Cu) and lead (Pb), and herbicides (glyphosate) on both adults and recruits of Carpodesmia crinita, a Mediterranean canopy forming macroalga. We show that although adult biomass, height and photosynthetic yield remain almost unaffected in all the assays, low Cu levels of 30 µg/L completely suppress adult fertility.In addition, all the assays have a strong and negative impact on the survival and growth of recruits; in particular, glyphosate concentrations above 1 µg/L almost totally inhibit their survival. These results suggest that the long-term viability of C. crinita may be severely compromised by low pollutant levels that are not affecting adult specimens. Our results provide important data for a better understanding of the present-day threats to marine canopy-forming macroalgae and for the design of future management actions aimed at preserving macroalgal forests.

Highlights

Marine macroalgal forests are highly productive and iconic ecosystems, which are seriously threatened by number of factors such as habitat destruction, overgrazing, ocean warming, and pollution
These highly productive and iconic ecosystems are declining in some areas due to the accumulation of anthropogenic impacts, such as those related to intensive land use, pollution, warming or invasive species[12,13,14,15,16,17,18,19,20,21,22]
There is a current lack of knowledge on the subtle anthropogenic stressors affecting the permanence of macroalgal forests, which might be behind the local declines of these ecosystems

Summary

Introduction

Marine macroalgal forests are highly productive and iconic ecosystems, which are seriously threatened by number of factors such as habitat destruction, overgrazing, ocean warming, and pollution. All the assays have a strong and negative impact on the survival and growth of recruits; in particular, glyphosate concentrations above 1 μg/L almost totally inhibit their survival These results suggest that the long-term viability of C. crinita may be severely compromised by low pollutant levels that are not affecting adult specimens. The loss of macroalgal forests implies a loss or impoverishment of ecosystem services such as nutrient cycling, food production, nursery habitat provision, erosion reduction, and control of water q uality[13] Deterioration of these complex habitats is often associated with a replacement of canopy-forming algae by ephemeral and structurally simpler macroalgae, affecting the status and functioning of these e cosystems[13,23]. Directive (2008/56/EC) that the amount of pollution steadily decreased in EU Mediterranean countries due to the construction of water treatment p lants[35,41]

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