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Responses of chlorophyll a to added nutrients, Asian dust, and rainwater in an oligotrophic zone of the Yellow Sea: Implications for promotion and inhibition effects in an incubation experiment
Author(s) -
Liu Y.,
Zhang T. R.,
Shi J. H.,
Gao H. W.,
Yao X. H.
Publication year - 2013
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
eISSN - 2169-8961
pISSN - 2169-8953
DOI - 10.1002/2013jg002329
Subject(s) - phytoplankton , nutrient , environmental chemistry , chlorophyll a , bloom , environmental science , incubation , chlorophyll , chemistry , zoology , botany , biology , ecology , biochemistry , organic chemistry
Increasing anthropogenic atmospheric deposition of nutrients, trace metals, and toxic substances to oceans may synergistically enhance or inhibit some specific phytoplankton growth, subsequently modulating primary productivity. In this study, onboard incubation experiments were performed in the southern Yellow Sea in the spring of 2011 to explore the responses of microphytoplankton, nanophytoplankton, and picophytoplankton to various combinations of added substances. The water samples used were collected at a lower nutrient concentration zone with an N/P ratio of 10, where satellite data showed a bloom on the eleventh day after collection. The bloom also occurred in the control experiment on the ninth to eleventh days. We simulated atmospheric input by artificially adding Asian dust, rainwater, nitrogen (dissolved inorganic N), phosphorus (P), and iron (Fe). The addition of a large amount of Asian dust increased both the maximum concentration of chlorophyll a (Chl a) and the conversion efficiency index of N into Chl a (CEI) by ~40% and ~30%, respectively, compared to the control, indicative of promoting growth of the phytoplankton. However, no promotion effect on phytoplankton growth was observed when the addition of Asian dust was reduced to10% of the original amount. The addition of rainwater increased the maximum concentration of Chl a by ~40% but decreased the CEI by ~40%, indicating inhibition coexisting with promotion of some phytoplankton species. Moreover, the size‐fractioned Chl a data showed that the inhibition effect pertained to nanophytoplankton and occurred following the bloom (after the eighth day).