Eukaryotic plankton community stability across reef environments in Bocas del Toro Archipelago (Panama)

Variation in light and temperature can influence the genetic diversity and structure of marine plankton communities. While open ocean plankton communities receive much scientific attention, little is known about how environmental variation affects tropical coral reef plankton communities. Here, we characterize eukaryotic plankton communities on coral reefs across the Bocas del Toro Archipelago in Panama. Temperature loggers were deployed for one year and mid-day light levels were measured to quantify environmental differences across reef zones at four inner and four outer reef sites: Inner: Punta Donato, Smithsonian Tropical Research Institute (STRI) Point, Cristobal, Punta Laurel and Outer: Drago Mar, Bastimentos North, Bastimentos South, and Popa Island. Triplicate vertical plankton tows were collected mid-day and high-throughput 18S ribosomal DNA metabarcoding was leveraged to investigate the relationship between eukaryotic plankton community structure and reef zones. Plankton communities from STRI Point were additionally characterized in the morning ([~]08:00), mid-day ([~]12:00), and evening ([~]16:00) to quantify diel variation within a single site. We found that inshore reefs experienced higher average seawater temperatures, while offshore sites offered higher light levels, presumably associated with reduced water turbidity on reefs further from shore. However, these significant reef zone-specific environmental differences did not correlate with overall plankton community differences or changes in plankton genetic diversity. Instead, we found that time of day within a site and diel vertical migration played structuring roles within these plankton communities, and therefore conclude that the time of community sampling is an important consideration for future studies. Overall, plankton communities in the Bocas del Toro Archipelago appear relatively well mixed across space; however, follow-up studies focusing on more intensive sampling efforts across space and time coupled with techniques that can detect more subtle genetic differences between and within communities will more fully capture plankton dynamics in this region.