Project description:In January 2003, the US Environmental Protection Agency sponsored a "roundtable discussion" to develop a consensus on the relationship between eutrophication and harmful algal blooms (HABs), specifically targeting those relationships for which management actions may be appropriate. Academic, federal, and state agency representatives were in attendance. The following seven statements were unanimously adopted by attendees based on review and analysis of current as well as pertinent previous data: 1) Degraded water quality from increased nutrient pollution promotes the development and persistence of many HABs and is one of the reasons for their expansion in the U.S. and the world; 2) The composition - not just the total quantity - of the nutrient pool impacts HABs; 3) High biomass blooms must have exogenous nutrients to be sustained; 4) Both chronic and episodic nutrient delivery promote HAB development; 5) Recently developed tools and techniques are already improving the detection of some HABs, and emerging technologies are rapidly advancing toward operational status for the prediction of HABs and their toxins; 6) Experimental studies are critical to further the understanding of the role of nutrients in HAB expression, and will strengthen prediction and mitigation of HABs; and 7) Management of nutrient inputs to the watershed can lead to significant reduction in HABs. Supporting evidence and pertinent examples for each consensus statement is provided herein.
Project description:Monitoring ecological changes in marine ecosystems is expensive and time-consuming. Passive acoustic methods provide continuous monitoring of soniferous species, are relatively inexpensive, and can be integrated into a larger network to provide enhanced spatial and temporal coverage of ecological events. We demonstrate how these methods can be used to detect changes in fish populations in response to a Karenia brevis red tide harmful algal bloom by examining sound spectrum levels recorded by two land-based passive acoustic listening stations (PALS) deployed in Sarasota Bay, Florida, before and during a red tide event. Significant and temporally persistent decreases in sound spectrum levels were recorded in real time at both PALS in four frequency bands spanning 0.172-20 kHz after K. brevis cells were opportunistically sampled near the stations. The decrease in sound spectrum levels and increase in K. brevis cell concentrations also coincided with decreased catch per unit effort (CPUE) and species density per unit effort (SDPUE) data for non-clupeid fish and soniferous fish species, as well as increased reports of marine mammal mortalities in the region. These findings demonstrate how PALS can detect and report in real time ecological changes from episodic disturbances, such as harmful algal blooms.
Project description:ImportanceThis study represents the first that investigates in situ virus infection in dinoflagellate blooms. Our findings reveal highly similar viral assemblages that infected the bloom species Prorocentrum shikokuense and a co-adapted metabolic relationship between the host and the viruses in the blooms, which varied between the prolonged and the short-lived blooms of the same dinoflagellate species. These findings fill the gap in knowledge regarding the identity and behavior of viruses in a dinoflagellate bloom and shed light on what appears to be the complex mode of infection. The novel insight will be potentially valuable for fully understanding and modeling the role of viruses in regulating blooms of dinoflagellates and other algae.
Project description:The genome encodes the metabolic and functional capabilities of an organism and should be a major determinant of its ecological niche. Yet, it is unknown if the niche can be predicted directly from the genome. Here, we conduct metagenomic binning on 123 water samples spanning major environmental gradients of the Baltic Sea. The resulting 1961 metagenome-assembled genomes represent 352 species-level clusters that correspond to 1/3 of the metagenome sequences of the prokaryotic size-fraction. By using machine-learning, the placement of a genome cluster along various niche gradients (salinity level, depth, size-fraction) could be predicted based solely on its functional genes. The same approach predicted the genomes' placement in a virtual niche-space that captures the highest variation in distribution patterns. The predictions generally outperformed those inferred from phylogenetic information. Our study demonstrates a strong link between genome and ecological niche and provides a conceptual framework for predictive ecology based on genomic data.
Project description:We measured the concentrations of dissolved inorganic and organic nutrients, dissolved organic carbon (DOC), total hydrolyzable amino acids (THAA), fluorescent dissolved organic matter (FDOM), phytoplankton pigments, and δ13C-DOC during the summer of 2019 in the harmful dinoflagellate bloom regions of the southern coast of Korea. In the harmful dinoflagellate bloom region, the concentrations of inorganic nitrogen were depleted, inhibiting the growth of diatoms, while the concentrations of dissolved organic components (nutrients, DOC, FDOM, and amino acids) which fuel dinoflagellates were unusually high. Thus, we attempted to investigate the origins and characteristics of DOM which fuels the harmful dinoflagellate blooms. The δ13C-DOC values (- 22.2‰ to - 18.2‰) indicate that the elevated DOC concentrations result from in-situ biological production rather than terrestrial inputs. The enantiomeric (D/L) ratios of THAA indicate that dissolved organic nitrogen was more labile in the early stage of harmful dinoflagellate bloom and became more refractory in the final stage. Our results suggest that the marine production of bioavailable DOM plays an important role in initiating and sustaining harmful dinoflagellate blooms.
Project description:The development and demise of a harmful algal bloom (HAB) are generally regulated by multiple processes; identifying specific critical drivers for a specific bloom is important yet challenging. Here, we conducted a whole-assemblage molecular ecological study on a dinoflagellate bloom to address the hypothesis that energy and nutrient acquisition, defense against grazing and microbial attacks, and sexual reproduction are critical to the rise and demise of the bloom. Microscopic and molecular analyses identified the bloom-causing species as Karenia longicanalis and showed that the ciliate Strombidinopsis sp. was dominant in a nonbloom plankton community, whereas the diatom Chaetoceros sp. dominated the after-bloom community, along with remarkable shifts in the community structure for both eukaryotes and prokaryotes. Metatranscriptomic analysis indicated that heightened energy and nutrient acquisition in K. longicanalis significantly contributed to bloom development. In contrast, active grazing by the ciliate Strombidinopsis sp. and attacks by algicidal bacteria (Rhodobacteracea, Cryomorphaceae, and Rhodobacteracea) and viruses prevented (at nonbloom stage) or collapsed the bloom (in after-bloom stage). Additionally, nutrition competition by the Chaetoceros diatoms plausibly contributed to bloom demise. The findings suggest the importance of energy and nutrients in promoting this K. longicanalis bloom and the failure of antimicrobial defense and competition of diatoms as the major bloom suppressor and terminator. This study provides novel insights into bloom-regulating mechanisms and the first transcriptomic data set of K. longicanalis, which will be a valuable resource and essential foundation for further elucidation of bloom regulators of this and related species of Kareniaceae in the future. IMPORTANCE HABs have increasingly occurred and impacted human health, aquatic ecosystems, and coastal economies. Despite great efforts, the factors that drive the development and termination of a bloom are poorly understood, largely due to inadequate in situ data about the physiology and metabolism of the causal species and the community. Using an integrative molecular ecological approach, we determined that heightened energy and nutrient acquisition promoted the bloom, while resource allocation in defense and failure to defend against grazing and microbial attacks likely prevented or terminated the bloom. Our findings reveal the differential roles of multiple abiotic and biotic environmental factors in driving the formation or demise of a toxic dinoflagellate bloom, suggesting the importance of a balanced biodiverse ecosystem in preventing a dinoflagellate bloom. The study also demonstrates the power of whole-assemblage metatranscriptomics coupled to DNA barcoding in illuminating plankton ecological processes and the underlying species and functional diversities.
Project description:Marine phytoplankton comprise the foundation of oceanic food webs and generate most of the Earth's oxygen. Of the many phytoplankton species in the ocean, a few dozen produce potent toxins, and at high concentrations can form what are called Harmful Algal Blooms (HABs) or "red tides" that can discolor marine waters. Managers and scientists have been monitoring coastal waters and shellfish resources for HABs and their toxins to ensure seafood safety and understand why blooms occur. This educational activity focuses on a prominent HAB species that causes paralytic shellfish poisoning (PSP). Students will learn about the importance of HABs and PSP, as well as how scientists collect and use data to understand and predict blooms. Students will plot data on HAB species collected by scientists over multiple years of sampling. Students will also plot results over time and across regions, report on observed patterns, and complete grade-appropriate calculations. Lastly, group discussion will focus on determining whether geographic patterns exist that might influence where shellfish beds are closed. This activity is timely given the widespread wildlife mortalities and beach closures due to Florida red tide, as well as recent dog deaths attributed to exposure to freshwater cyanobacteria (blue-green algae) blooms.
Project description:Harmful Algal Blooms (HABs) are of global concern, as their presence is often associated with socio-economic and environmental issues including impacts on public health, aquaculture and fisheries. Therefore, monitoring the occurrence and succession of HABs is fundamental for managing coastal regions around the world. Yet, due to the lack of adequate in situ measurements, the detection of HABs in coastal marine ecosystems remains challenging. Sensors on-board satellite platforms have sampled the Earth synoptically for decades, offering an alternative, cost-effective approach to routinely detect and monitor phytoplankton. The Red Sea, a large marine ecosystem characterised by extensive coral reefs, high levels of biodiversity and endemism, and a growing aquaculture industry, is one such region where knowledge of HABs is limited. Here, using high-resolution satellite remote sensing observations (1km, MODIS-Aqua) and a second-order derivative approach, in conjunction with available in situ datasets, we investigate for the first time the capability of a remote sensing model to detect and monitor HABs in the Red Sea. The model is able to successfully detect and generate maps of HABs associated with different phytoplankton functional types, matching concurrent in situ data remarkably well. We also acknowledge the limitations of using a remote-sensing based approach and show that regardless of a HAB's spatial coverage, the model is only capable of detecting the presence of a HAB when the Chl-a concentrations exceed a minimum value of ~ 1 mg m-3. Despite the difficulties in detecting HABs at lower concentrations, and identifying species toxicity levels (only possible through in situ measurements), the proposed method has the potential to map the reported spatial distribution of several HAB species over the last two decades. Such information is essential for the regional economy (i.e., aquaculture, fisheries & tourism), and will support the management and sustainability of the Red Sea's coastal economic zone.
Project description:Harmful algal blooms are caused by specific members of microbial communities. Understanding the dynamics of these events requires comparing the strategies developed by the problematic species to cope with environmental fluctuations to the ones developed by the other members of the community. During three consecutive years, the meta-transcriptome of micro-eukaryote communities was sequenced during blooms of the toxic dinoflagellate Alexandrium minutum. The dataset was analyzed to investigate species specific gene expression dynamics. Major shifts in gene expression were explained by the succession of different species within the community. Although expression patterns were strongly correlated with fluctuation of the abiotic environment, and more specifically with nutrient concentration, transcripts specifically involved in nutrient uptake and metabolism did not display extensive changes in gene expression. Compared to the other members of the community, A. minutum displayed a very specific expression pattern, with lower expression of photosynthesis transcripts and central metabolism genes (TCA cycle, glucose metabolism, glycolysis…) and contrasting expression pattern of ion transporters across environmental conditions. These results suggest the importance of mixotrophy, cell motility and cell-to-cell interactions during A. minutum blooms.