Effects of the harmful algae bloom Microcystis aeruginosa on reproduction in copepods

The harmful cyanobacteria Microcystis aeruginosa has formed summer blooms in the San Francisco Estuary (SFE) for more than a decade, and blooms may disrupt the aquatic foodweb via toxicity and reduced food quality to zooplankton. The objective of this study was to examine if dietary M. aeruginosa affects one important zooplankton species, the copepod Pseudodiaptomus forbesi, through its reproductive success. Using laboratory feeding experiments with toxic and non-toxic M. aeruginosa, as well as observations of field collected samples, we evaluated egg ratios, egg hatching success (EHS), and egg production rates (EPR) of P. forbesi. We also used feeding experiments to examine how differences in media, in conjunction with M. aeruginosa in the diet, affected reproduction. We found P. forbesi to be more tolerant to dietary M. aeruginosa than previously recorded in the literature; however, M. aeruginosa (both toxic and nontoxic) above 10% of the available food reduced EHS and survival. It is unlikely that current M. aeruginosa blooms affect reproductive rates in P. forbesi in the upper SFE, and thus unlikely to affect fish through trophic interactions