RESPONSES OF GYMNODINIUM BREVE DAVIS TO NATURAL WATERS OF DIVERSE ORIGIN(1)

Area of Science:

• Marine biology
• Algology
• Environmental science

Background:

• *Gymnosdinium breve* is a dinoflagellate responsible for harmful algal blooms.
• Understanding factors influencing its growth is crucial for bloom prediction and management.
• Nutrient availability in aquatic environments is a key determinant of phytoplankton dynamics.

Purpose of the Study:

• To investigate the impact of river and seawater samples on *Gymnosdinium breve* growth.
• To determine the effects of seasonal variations and geographical locations on growth-promoting properties.
• To identify specific nutrient enrichments that enhance *Gymnosdinium breve* proliferation.

Main Methods:

• Collection of river water and seawater samples across different seasons and locations.
• Culturing of *Gymnosdinium breve* with and without various nutrient enrichments.
• Monitoring and quantification of *Gymnosdinium breve* growth rates under different conditions.

Main Results:

• *Gymnosdinium breve* growth in natural seawater was significantly enhanced by the addition of EDTA-Fe, sulfide, nitrogen (N), and phosphorus (P).
• Seasonal variations in the growth-promoting properties of both seawater and river water were more pronounced than variations due to location.
• Specific nutrient additions, particularly EDTA-Fe, sulfide, N, and P, demonstrated a clear positive effect on algal growth.

Conclusions:

• Nutrient enrichment, specifically EDTA-Fe, sulfide, N, and P, plays a critical role in promoting *Gymnosdinium breve* growth.
• The temporal factor (season) is a dominant driver of water's growth-promoting capacity for *Gymnosdinium breve*, overriding spatial differences.
• These findings highlight the importance of nutrient dynamics and seasonal changes in the context of harmful algal bloom formation and management.