Grazing on Synechococcus spp. by the Red-Tide Dinoflagellate Karenia brevis: Implications for Bloom Dynamics in the Gulf of Mexico
type: CreativeWork
description: Karenia brevis, the toxic dinoflagellate responsible for massive red tides in the Gulf of Mexico (GOM), causes fish kills, shellfish poisoning, and acute respiratory irritation in humans. Bloom initiation and maintenance have been linked to the physical environment as well as various nutrient input mechanisms. To date, efforts to quantify nitrogen (N) sources fueling K. brevis blooms in the GOM have not included mixotrophic grazing although many dinoflagellates, including K. brevis, are known to be capable of mixotrophy. This dissertation reports field and laboratory results demonstrating that natural bloom populations and K. brevisisolates from the West Florida Shelf (WFS) can ingest a WFS Synechococcus isolate. Maximum K. brevis ingestion rates were measured within the first 2 to 6 hours in laboratory incubations augmented with Synechococcus prey and rates ranged from 7.2 to 48.0 Synechococcus K. brevis -1 hr-1. I calculated a lower feeding threshold of 1.86 × 104 Synechococcus ml-1 , which is the prey concentration necessary for K. brevis to ingest this prey organism. To determine whether dissolved N or light affected ingestion rates for Karenia brevis on Synechococcus, grazing was measured in N-replete and -deplete cultures and during the day and night when incubation lights were on or off, respectively. Ingestion rates ranged from 2.7 to 7.2 Synechococcus K. brevis-1 hr-1 and there were no significant differences in ingestion rates between treatments. I calculate that the N-specific uptake rates from Synechococcus prey were on the order of 10-2 to 101 μmol N l-1 hr-1. I also demonstrate for the first time that K. brevis is able to ingest Prochlorococcus (27.3 ± 8.3 Prochlorococcus K. brevis -1 hr-1) and heterotrophic bacteria (0.1 - 3.1 bacteria K. brevis-1 hr-1), although the latter are likely underestimates as I tried to minimize contamination by heterotrophic bacteria in K. brevis cultures. Karenia brevis ingestion rates on live and heat-killed Synechococcus…
abstract: Karenia brevis, the toxic dinoflagellate responsible for massive red tides in the Gulf of Mexico (GOM), causes fish kills, shellfish poisoning, and acute respiratory irritation in humans. Bloom initiation and maintenance have been linked to the physical environment as well as various nutrient input mechanisms. To date, efforts to quantify nitrogen (N) sources fueling K. brevis blooms in the GOM have not included mixotrophic grazing although many dinoflagellates, including K. brevis, are known to be capable of mixotrophy. This dissertation reports field and laboratory results demonstrating that natural bloom populations and K. brevisisolates from the West Florida Shelf (WFS) can ingest a WFS Synechococcus isolate. Maximum K. brevis ingestion rates were measured within the first 2 to 6 hours in laboratory incubations augmented with Synechococcus prey and rates ranged from 7.2 to 48.0 Synechococcus K. brevis -1 hr-1. I calculated a lower feeding threshold of 1.86 × 104 Synechococcus ml-1 , which is the prey concentration necessary for K. brevis to ingest this prey organism. To determine whether dissolved N or light affected ingestion rates for Karenia brevis on Synechococcus, grazing was measured in N-replete and -deplete cultures and during the day and night when incubation lights were on or off, respectively. Ingestion rates ranged from 2.7 to 7.2 Synechococcus K. brevis-1 hr-1 and there were no significant differences in ingestion rates between treatments. I calculate that the N-specific uptake rates from Synechococcus prey were on the order of 10-2 to 101 μmol N l-1 hr-1. I also demonstrate for the first time that K. brevis is able to ingest Prochlorococcus (27.3 ± 8.3 Prochlorococcus K. brevis -1 hr-1) and heterotrophic bacteria (0.1 - 3.1 bacteria K. brevis-1 hr-1), although the latter are likely underestimates as I tried to minimize contamination by heterotrophic bacteria in K. brevis cultures. Karenia brevis ingestion rates on live and heat-killed Synechococcus…
author: Procise, Leo A.
keywords: Bloom dynamics, Grazing, Gulf of Mexico, Karenia brevis, Mixofrophy, Red-tide dinoflagellate, Synechococcus, Ecology and Evolutionary Biology, Microbiology, Oceanography
date published: 2012-01-01T08:00:00Z
date modified: 2026-07-24T03:34:39Z
provider: Old Dominion University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Old Dominion University