Iron Availability Modulates the Response of Endosymbiotic Dinoflagellates to Heat Stress.

Warming and nutrient limitation are stressors known to weaken the health of microalgae. In situations of stress, access to energy reserves can minimize physiological damage. Because of its widespread requirements in biochemical processes, iron is an important trace metal, especially for photosynthetic organisms.

RNA-seq profiling of Fugacium kawagutii reveals strong responses in metabolic processes and symbiosis potential to deficiencies of iron and other trace metals.

A healthy symbiotic relationship between corals and Symbiodiniaceae relies on suitable temperature and adequate nutrients including trace metals. Besides global warming, trace metal deficiency has been shown to cause coral bleaching, a phenomenon responsible for extensive coral reef degradation around the world. How trace metal deficiency impacts Symbiodiniaceae and coral symbiosis is poorly understood, however.

Trace Metal Requirements and Interactions in .

Photosynthetic organisms need trace metals for various biological processes and different groups of microalgae have distinctive obligate necessities due to their respective biochemical requirements and ecological niches. We have previously shown that the dinoflagellate requires high concentrations of bioavailable Fe to achieve optimum growth. Here, we further explored the trace metal requirements of with intensive focus on the effect of individual metal and its interaction with other divalent metals.

Interactive effects of spectral quality and trace metal availability on the growth of Trichodesmium and Symbiodinium.

Light and trace metals are critical growth factors for algae but how the interdependence of light quality and metal availability affects algal growth remains largely unknown. Our previous studies have demonstrated the importance of Ni and Fe on the growth of Trichodesmium and Symbiodinium, respectively, two important marine primary producers inhabiting environments with high light intensities. Here, we investigated the effects of light quality and intensity with availability of either Ni or Fe on their growth.

Effects of Trace Metal Concentrations on the Growth of the Coral Endosymbiont Symbiodinium kawagutii.

Symbiodinium is an indispensable endosymbiont in corals and the most important primary producer in coral reef ecosystems. During the past decades, coral bleaching attributed to the disruption of the symbiosis has frequently occurred resulting in reduction of coral reef coverage globally. Growth and proliferation of corals require some specific trace metals that are essential components of pertinent biochemical processes, such as in photosynthetic systems and electron transport chains.

Influence of Co and B 12 on the growth and nitrogen fixation of Trichodesmium.

We investigated the influence of varying cobalt (Co) and B12 concentrations to growth and nitrogen fixation of Trichodesmium, a major diazotroph in the tropical and subtropical oligotrophic ocean. Here we show that sufficient inorganic Co, 20 pmol L(-1), sustains the growth of Trichodesmium either with or without an additional B12 supply. We also found that in these culture conditions, nitrogen levels fixed by Trichodesmium were higher in treatments with insufficient B12 than in treatments with higher B12 availability.

Diel nitrogen fixation pattern of Trichodesmium: the interactive control of light and Ni.

Trichodesmium, a nonheterocystous cyanobacterium widely abundant in the surface water of the tropical and subtropical ocean, fixes dinitrogen under high light conditions while concurrently undergoing photosynthesis. The new production considerably influences the cycling of nitrogen and carbon in the ocean. Here, we investigated how light intensity and nickel (Ni) availability interplay to control daily rates and diel patterns of N2 fixation in Trichodesmium.