Microphytoplankton variations during coral spawning at Los Roques, Southern Caribbean

Area of Science:

• Marine ecology
• Oceanography
• Microbiology

Background:

• Phytoplankton are crucial for primary productivity in marine ecosystems, including oligotrophic coral reefs.
• Nutrient inputs from natural and anthropogenic sources can disrupt coral reef trophic webs.
• Understanding phytoplankton dynamics is key to assessing coral reef health and function.

Purpose of the Study:

• To characterize microphytoplankton assemblages in relation to coral spawning events in the Caribbean.
• To investigate temporal and spatial variations in phytoplankton communities at different scales.
• To determine the influence of coral spawning on phytoplankton abundance and composition.

Main Methods:

• A hierarchical experimental design was employed in Los Roques archipelago, Venezuela.
• Superficial water samples were collected daily for 9 days around full moon in August 2007 and 2008.
• Microalgae taxa, chlorophyll a concentrations, and higher taxonomic groups (diatoms, cyanophytes, dinoflagellates) were analyzed.

Main Results:

• Microphytoplankton assemblages showed temporal and spatial variations linked to coral spawning in 2007.
• Chlorophyll a concentrations increased during and after spawning events in both years.
• Dinoflagellates and diatoms exhibited variations related to spawning times, with some reefs showing asynchronous patterns.

Conclusions:

• Coral spawning influences microphytoplankton composition and chlorophyll a concentrations in coral reef waters.
• Microheterotrophic grazers likely play a significant role in nutrient re-mineralization.
• Assessing changes in larger phytoplankton fractions is important for understanding primary productivity and nutrient fluxes in coral reefs.