Photo Credit: Kevin Johnson

Potential Grazers on Harmful Algal Blooms in the IRL

This project will identify common and abundant mesoplanktonic grazers (≥ 200 μm) in the northern Indian River Lagoon (IRL) and estimate clearance rates for those grazers, with a focus on the potential to control Harmful Algal Blooms occurring recently in the northern Indian River Lagoon. These objectives will be accomplished through a combination of field surveys and grazing experiments conducted in the laboratory. Surveys will employ a towed plankton net at strategically selected sites that complement those being sampled for water quality, algal blooms and microzooplankton (≤ 200 μm). Standard water quality data is also being collected. The resulting plankton samples will be processed in the laboratory to identify and quantify key grazers on algal blooms. We will determine the settled plankton volume for all samples, enabling an analysis of overall productivity and biomass, comparing across space and temporally. In addition, 4 grazing experiments will be performed during the course of the study. Ideally, the algal blooms will be dominated by species that comprised the Superbloom of 2011, with grazers selected from among the common and abundant zooplankton encountered during surveys. For example, it is likely that we will examine the diet and feeding rates of copepod species from the northern Indian River Lagoon, including the common copepod Acartia tonsa. If cultures of the species from algal blooms cannot be obtained, then experiments will use species of similar size or samples of phytoplankton assemblages encountered during surveys. 

Dr. Kevin B. Johnson from the Florida Institute of Technology (FIT) is the project’s principal investigator (P.I.).

This investigation of algal blooms and their grazers is building upon long-term, multi-agency sampling efforts and the Superbloom investigations. Through this study, we hope to employ additional diagnostic resources and expertise to better understand the troubling shift in the Lagoon’s primary production and to develop suitable measures to reverse it. We aim to improve scientific understanding of the primary producer and consumer assemblages, especially causal links between variation in drivers and forcing factors and the initiation and maintenance of algal blooms. This improved understanding will be translated into sound recommendations for managing controllable drivers to prevent or ameliorate major blooms that are harmful to seagrasses. Thus, completion of this project work will (1) improve knowledge of mesozooplanktonic grazers and (2) improve an understanding of grazing pressure and its potential to act as a “top-down” control on phytoplankton blooms. This project is funded by the St. John’s River Water Management District.