Comparative metagenomics of phytoplankton blooms after nutrient enrichment of oligotrophic marine waters

By

Pearman, John K.
Casas, Laura
Michell, Craig
Aldanondo, Naroa
Mojib, Nazia
Holtermann, Karie
Georgakakis, Ioannis
Curdia, Joao
Carvalho, Susana
Gusti, Amr
Irigoien, Xabier

Type

Article

Date of Publication

2022-4-12

Original Publication

Metabarcoding and metagenomics

Volume

6

Pages

1--15

Subjects

Algal blooms , Eutrophication , Metagenomics , nutrient enrichment

Contributed by

Pensoft Publishers

Language

English

Published by

Bulgaria Pensoft Publishers 2017-

Identifiers

DOI: https://doi.org/10.3897/mbmg.6.79208

 

Abstract

Increasing anthropogenic pressures on the coastal marine environments impact these ecosystems via a variety of mechanisms including nutrient loading, leading to eutrophication and increases in algal blooms. Here, we use a metagenomics approach to assess the taxonomic and functional changes of the microbial community throughout a nutrient enriched mesocosm phytoplankton bloom. We tested four different nutrient treatments consisting of either nitrate and phosphate or nitrate, phosphate and silicate, administered on the first day or continuously for the first two weeks of the experiment. Our results show a shift in the taxonomic composition of the community over time that is dependent on the nutrient addition regime. Significant differences in the functional potential of the communities were detected, with an interaction between bloom period (pre-bloom, bloom and post-bloom) and nutrient treatment (p = 0.004). A sharp drop in functional similarity was observed in the first week in all treatments and after 20 days had not returned to pre-bloom levels. Changes within energy metabolism pathways showed a remarkable enrichment of the dissimilatory nitrate reduction pathway in the post-bloom period. Eukaryotic oxidative phosphorylation and photosynthetic antenna proteins were more abundant during the bloom, especially in the continuous treatment with silicate. Our results suggest that continuous (i.e. chronic) nutrient enrichment has a larger effect on the functioning of marine systems compared to a single (i.e acute) addition. A deep understanding of the functional and taxonomic shifts in the community during blooms is essential to reverse or mitigate human impacts on coastal environments.