Project description:Climate warming is one factor increasing the severity of harmful algal blooms (HABs). Innovative exposure models are needed to understand how HABs affect brain health. Here, we examined HAB exposure on the brain transcriptome of dolphins found stranded in Florida’s Indian River Lagoon. We report the neurotoxin 2,4-diaminobutyric acid (2,4-DAB) is 2,900 times more concentrated in dolphin brains during bloom seasons compared to non-bloom seasons. The same dolphins show 536 differentially expressed genes whose enrichment reveal impairment in GABAergic synapses, basement membrane alteration, and Alzheimer’s disease (AD) risk factors that increase with each subsequent season. Dolphins also display concurrent AD-like neuropathological changes and elevated AD gene expression with 2,4-DAB exposure. Our study demonstrates disproportionate seasonal exposure to 2,4-DAB increases AD signatures in the brain transcriptome. As our climate warms, HABs will continue to intensify. Understanding the impact of HAB exposures will help to identify populations at risk for neurological illnesses.
Project description:Phytoplankton blooms provoke bacterioplankton blooms, from which bacterial biomass (necromass) is released via increased zooplankton grazing and viral lysis. While bacterial consumption of algal biomass during blooms is wellstudied, little is known about the concurrent recycling of these substantial amounts of bacterial necromass. We demonstrate that bacterial biomass, such as bacterial alpha-glucan storage polysaccharides, generated from the consumption of algal organic matter, is reused and thus itself a major bacterial carbon source in vitro and during a diatom-dominated bloom. We highlight conserved enzymes and binding proteins of dominant bloom-responder clades that are presumably involved in the recycling of bacterial alpha-glucan by members of the bacterial community. We furthermore demonstrate that the corresponding protein machineries can be specifically induced by extracted alpha-glucan-rich bacterial polysaccharide extracts. This recycling of bacterial necromass likely constitutes a large-scale intra-population energy conservation mechanism that keeps substantial amounts of carbon in a dedicated part of the microbial loop.
Project description:<p>Algal blooms are hotspots of primary production in the ocean, forming the basis of the marine food web and fueling the dissolved organic matter (DOM) pool. Marine viruses are key players in controlling algal bloom demise, thereby diverting algal biomass from higher trophic levels to the DOM pool, a process termed the ‘viral shunt’. To decode the metabolic footprint of the ‘viral shunt’ in the marine environment, we induced a bloom of <em>Emiliania huxleyi</em> and followed its succession using an untargeted exometabolomics approach. Here, we show that algal bloom succession induces dynamic changes in the exometabolic landscape. We discovered a set of novel chlorine-iodine-containing metabolites that were induced by viral infection and released during bloom demise. These metabolites were further detected in virus-infected oceanic <em>E. huxleyi</em> blooms. Therefore, we propose that halogenation with both chlorine and iodine is a distinct hallmark of the virus-induced DOM of <em>E. huxleyi</em>, providing insights into the metabolic consequences of the ‘viral shunt’ for marine DOM.</p>