Light fluctuations are key in modulating plankton trophic dynamics and their impact on primary production

[摘要] Surface-ocean mixing creates dynamic light environments with predictable effects on phytoplankton growth but unknown consequences for predation. We investigated how variations in average mixed-layer (ML) irradiance shaped plankton trophic dynamics by incubating a Northwest-Atlantic plankton community for 4 days at high (H) and low (L) light, followed by exposure to either sustained or reversed light intensities. In deep-ML (sustained L), phytoplankton biomass declined (μ = −0.2 ± 0.08 d−1 ) and grazing was absent. In shallow-ML (sustained H), growth exceeded grazing (μ = 0.46 ± 0.07 d−1 ; g = 0.32 ± 0.04 d−1 ). In rapidly changing ML-conditions simulated by switching light-availability, growth and grazing responded on different timescales. During rapid ML-shoaling (L to H), μ immediately increased (0.23 ± 0.01 d−1 ) with no change in grazing. During rapid ML-deepening (H to L), μ immediately decreased (0.02 ± 0.09 d−1 ), whereas grazing remained high (g = 0.38 ± 0.05 d−1 ). Predictable rate responses of phytoplankton growth (rapid) vs. grazing (delayed) to measurable light variability can provide insights into predator-prey processes and their effects on spatio-temporal dynamics of phytoplankton biomass.

[学科分类] 口腔科学