Nutrient stoichiometry of phytoplankton changes frequently with aquatic ambient nutrient concentrations, which is mainly influenced by environmental factors and the dynamics of ecosystems. Consequently, the stoichiometry of phytoplankton can markedly alter the metabolism and growth of zooplankton. However, the effects of nutrient-imbalanced prey on the interplay between zooplankton and their gut microbiota remain unknown. Using metatranscriptome sequencing, neutral community model (NCM), and experimental validation, we investigated the interactions between Daphnia magna and its gut microbiota on nutrient-imbalanced algal diet. Our results showed that in nutrient depleted water, nutrient-enriched zooplankton gut stimulated the accumulation of microbial polyphosphate and the assimilation of ammonia under phosphorus and nitrogen limited diet, respectively. Comparing with nutrient replete group, both N and P limitation had markedly promoted the gene expression of gut microbial for organic matter degradation but repressed that for anaerobic metabolisms. Besides, with N and P limited diet, the gut microbial community exhibited a higher fitting to NCM, suggesting increased ambient-gut exchange process favored by compensatory feeding of D. magna. This process also elevated oxygen level in the gut and explained the repressed anaerobic metabolism of gut microbes. Further axenic grazing experiment revealed that bacteria can still benefit D. magna to achieve a better growth under nutrient-imbalanced diet by enhancing their digestion capability. Together, these results demonstrated that under nutrient-imbalanced diet, the microbes not only benefit themself by absorbing excess nutrients inside zooplankton gut but also benefit zooplankton to achieve a better adaptation.

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On 05 Nov, 2020
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On 02 Nov, 2020
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On 16 Aug, 2020
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Invitations sent on 30 Jul, 2020
On 15 Jul, 2020
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Nutrient stoichiometry of phytoplankton changes frequently with aquatic ambient nutrient concentrations, which is mainly influenced by environmental factors and the dynamics of ecosystems. Consequently, the stoichiometry of phytoplankton can markedly alter the metabolism and growth of zooplankton. However, the effects of nutrient-imbalanced prey on the interplay between zooplankton and their gut microbiota remain unknown. Using metatranscriptome sequencing, neutral community model (NCM), and experimental validation, we investigated the interactions between Daphnia magna and its gut microbiota on nutrient-imbalanced algal diet. Our results showed that in nutrient depleted water, nutrient-enriched zooplankton gut stimulated the accumulation of microbial polyphosphate and the assimilation of ammonia under phosphorus and nitrogen limited diet, respectively. Comparing with nutrient replete group, both N and P limitation had markedly promoted the gene expression of gut microbial for organic matter degradation but repressed that for anaerobic metabolisms. Besides, with N and P limited diet, the gut microbial community exhibited a higher fitting to NCM, suggesting increased ambient-gut exchange process favored by compensatory feeding of D. magna. This process also elevated oxygen level in the gut and explained the repressed anaerobic metabolism of gut microbes. Further axenic grazing experiment revealed that bacteria can still benefit D. magna to achieve a better growth under nutrient-imbalanced diet by enhancing their digestion capability. Together, these results demonstrated that under nutrient-imbalanced diet, the microbes not only benefit themself by absorbing excess nutrients inside zooplankton gut but also benefit zooplankton to achieve a better adaptation.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8
This is a list of supplementary files associated with this preprint. Click to download.
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