Abstract
The harmful algal bloom (HAB)-forming dinoflagellate Karenia mikimotoi was exposed to different nitrogen (N) conditions, in order to study the population growth, temporary cyst production and cellular biochemical compositions in laboratory. The results indicated the population growth of K. mikimotoi was inhibited by different levels of N starvation but showed similar fast recovery after the resupplement of N, and temporary cysts were induced in the period of N starvation. K. mikimotoi grew well in inorganic (NO3-, NO2- and NH4+) and organic (urea) nitrogen sources, but the growth parameters (K, Tp, r) showed differences when simulated by Logistic model regressions. When the cellular organic compounds were measured simultaneously, K. mikimotoi cultured in urea produced more short-chained fatty acids while K. mikimotoi cultured in NH4+ produced more non-fatty acids compounds, indicating the potential change of toxins production cultured by various N sources. We concluded that K. mikimotoi could adapt to fluctuating N environments typical of coastal environments including total N concentration (deficiency or recovery) and relative compositions (different N sources).
Highlights
In the past several decades, the increased frequency and distribution of harmful algal blooms (HABs) in marine ecosystems has attracted worldwide research attention [1, 2, 3]
Population growth when exposed to N starvation and recovery conditions
We examined the response of K. mikimotoi to the variable ambient N conditions, and found: 1) the population growth of K. mikimotoi was limited by N starvation and recovered quickly after the replenishment of N; 2) temporary cysts were induced by N starvation; 3) K. mikimotoi grew well in four kinds of N source, but the population growth of K. mikimotoi varied in different forms of N, as well as the relative compositions of cellular organic compounds
Summary
In the past several decades, the increased frequency and distribution of harmful algal blooms (HABs) in marine ecosystems has attracted worldwide research attention [1, 2, 3]. As the most essential and frequent limiting nutrients, the concentration of N, P and N/P ratios will influence the population dynamics and the physiology of harmful algae at the species level [3, 6]. It is commonly accepted that N limitation (NO3-, NO2-, NH4+ and organic N (e.g., urea and amino acids)) occurs more frequently in marine ecosystems compared to freshwater ecosystems [7, 8, 9]. In coastal waters the increased concentration of the urea and reduced N forms is PLOS ONE | DOI:10.1371/journal.pone.0171996. In coastal waters the increased concentration of the urea and reduced N forms is PLOS ONE | DOI:10.1371/journal.pone.0171996 February 22, 2017
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