Harmful Algal Blooms Problem Research Articles

Characterization of cell death in harmful Karenia mikimotoi under algicidal activity of Marinobacter sp. O-7

Use of algicidal bacteria, which has the advantage of both safety and efficiency, has gradually become a significant strategy to handle the environmental problem of Harmful Algal Blooms (HABs). A strain of bacterium with excellent algicidal activity of 95.6% and identified as Marinobacter sp. (O-7) was isolated from seawater. The results demonstrated that strain O-7 can secrete active substances, which can pose a fatal threat to harmful Karenia mikimotoi. The morphology of K. mikimotoi cells changed over time. The physiological responses of algal cells after exposure to strain O-7 algicidal compounds were as follows: photosynthetic pigments (chlorophyll a and carotenoid) levels of the algal cells decreased significantly as did the photosynthetic efficiency and performance index, while reactive oxygen species levels substantially increased under the stress of 3% dose of O-7 for 4 h of treatment. Concurrently, the intracellular antioxidant enzymes system (superoxide dismutase, catalase, glutathione peroxidase) and non-enzymes system (glutathione, oxidized glutathione, ascorbic acid and dehydroascorbic acid) showed up-regulation. The content of malondialdehyde amplified with increase in concentration, indicating lipid peroxidation of algal cells. Collectively, our results demonstrated that the secretion of O-7 could act as an effective algicide for the control of harmful algae and offered clues to understanding the death mechanism of indirect processing of bacterial secretion against microalgae.

Visible-light-drivenself-floating Ag2MoO4/TACN@LF photocatalyst inactivation of Microcystis aeruginosa: Performance and mechanisms

The poor light transmittance, low recycling rate and potential secondary pollution problems of powder photocatalysts limit the practical application of photocatalytic technology. Therefore, there is an urgent need to develop stable floating photocatalysts to alleviate the problem of harmful algal blooms (HABs). In this work, a floating Ag2MoO4/TACN@LF composite was synthesized for the inactivation of Microcystis aeruginosa (M. aeruginosa) by employing a simple oscillatory impregnation method. The Ag2MoO4/TACN@LF floating photocatalyst exhibited stable algae removal performance under various conditions, and 100% chlorophyll a removal rate could be achieved within 4 h of visible light irradiation under the optimal photocatalyst loading of 6 g/L. The effects of Ag2MoO4/TACN@LF floating catalyst on algal cell membrane permeability, phycobiliprotein, intracellular antioxidant enzyme activities and algal organic matter were further studied. Moreover, the scavenging experiments demonstrated that •OH was the predominant reactive oxygen species (ROSs). Ag0 and 3g-C3N4 * also made a non-negligible contribution to the inactivation of algal cells. What's more, the Ag2MoO4/TACN@LF still exhibited 92% inactivation efficiency for M. aeruginosa after 5 cycles reused experiments, indicating its promising potential for practical application of alleviating HABs.

Marine harmful algal blooms (HABs) in the United States: History, current status and future trends

Harmful algal blooms (HABs) are diverse phenomena involving multiple. species and classes of algae that occupy a broad range of habitats from lakes to oceans and produce a multiplicity of toxins or bioactive compounds that impact many different resources. Here, a review of the status of this complex array of marine HAB problems in the U.S. is presented, providing historical information and trends as well as future perspectives. The study relies on thirty years (1990-2019) of data in HAEDAT - the IOC-ICES-PICES Harmful Algal Event database, but also includes many other reports. At a qualitative level, the U.S. national HAB problem is far more extensive than was the case decades ago, with more toxic species and toxins to monitor, as well as a larger range of impacted resources and areas affected. Quantitatively, no significant trend is seen for paralytic shellfish toxin (PST) events over the study interval, though there is clear evidence of the expansion of the problem into new regions and the emergence of a species that produces PSTs in Florida - Pyrodinium bahamense. Amnesic shellfish toxin (AST) events have significantly increased in the U.S., with an overall pattern of frequent outbreaks on the West Coast, emerging, recurring outbreaks on the East Coast, and sporadic incidents in the Gulf of Mexico. Despite the long historical record of neurotoxic shellfish toxin (NST) events, no significant trend is observed over the past 30 years. The recent emergence of diarrhetic shellfish toxins (DSTs) in the U.S. began along the Gulf Coast in 2008 and expanded to the West and East Coasts, though no significant trend through time is seen since then. Ciguatoxin (CTX) events caused by Gambierdiscus dinoflagellates have long impacted tropical and subtropical locations in the U.S., but due to a lack of monitoring programs as well as under-reporting of illnesses, data on these events are not available for time series analysis. Geographic expansion of Gambierdiscus into temperate and non-endemic areas (e.g., northern Gulf of Mexico) is apparent, and fostered by ocean warming. HAB-related marine wildlife morbidity and mortality events appear to be increasing, with statistically significant increasing trends observed in marine mammal poisonings caused by ASTs along the coast of California and NSTs in Florida. Since their first occurrence in 1985 in New York, brown tides resulting from high-density blooms of Aureococcus have spread south to Delaware, Maryland, and Virginia, while those caused by Aureoumbra have spread from the Gulf Coast to the east coast of Florida. Blooms of Margalefidinium polykrikoides occurred in four locations in the U.S. from 1921-2001 but have appeared in more than 15 U.S. estuaries since then, with ocean warming implicated as a causative factor. Numerous blooms of toxic cyanobacteria have been documented in all 50 U.S. states and the transport of cyanotoxins from freshwater systems into marine coastal waters is a recently identified and potentially significant threat to public and ecosystem health. Taken together, there is a significant increasing trend in all HAB events in HAEDAT over the 30-year study interval. Part of this observed HAB expansion simply reflects a better realization of the true or historic scale of the problem, long obscured by inadequate monitoring. Other contributing factors include the dispersion of species to new areas, the discovery of new HAB poisoning syndromes or impacts, and the stimulatory effects of human activities like nutrient pollution, aquaculture expansion, and ocean warming, among others. One result of this multifaceted expansion is that many regions of the U.S. now face a daunting diversity of species and toxins, representing a significant and growing challenge to resource managers and public health officials in terms of toxins, regions, and time intervals to monitor, and necessitating new approaches to monitoring and management. Mobilization of funding and resources for research, monitoring and management of HABs requires accurate information on the scale and nature of the national problem. HAEDAT and other databases can be of great value in this regard but efforts are needed to expand and sustain the collection of data regionally and nationally.

Long-Term Study of Soluble Reactive Phosphorus Concentration in Fall Creek and Comparison to Northeastern Tributaries of Cayuga Lake, NY: Implications for Watershed Monitoring and Management

This study focuses on soluble reactive phosphorus (SRP), a key driver of eutrophication worldwide and a potential contributor to the emerging global environmental problem of harmful algal blooms (HABs). Two studies of tributary SRP concentrations were undertaken in sub-watersheds of Cayuga Lake, NY, the subject of a total maximum daily load (TMDL) development process, due to phosphorus impairment of its southern shelf. The long-term study compared SRP concentration in Fall Creek in the 1970s with that in the first decade of the 2000s, thus spanning a period of change in phosphorus sources, as well as in regional climate. The spatial study used data collected between 2009 and 2018 and compared SRP concentrations in Fall Creek to levels in northeastern tributaries that flow into the lake close to areas where HABs have been problematic. SRP was measured using standard procedures. Flow-weighted mean SRP concentration ranged between 15.0 µg/L and 30.0 µg/L in all years studied in both the 1970s and 2000s, with the exception of 2010. Annual discharge in Fall Creek showed no trend between 1970 and 2018, but a higher proportion of high streamflow samples was captured in the 2000s compared to the 1970s, which resulted in proportionally increased SRP concentration in the latter time period. There was no significant difference in the SRP concentration—flow rate relationship between the two time periods. Adjusted for flow rate, SRP concentrations in Fall Creek have not changed over many decades. Increasing phosphorus contributions from growing population and urbanization since the 1970s may have been counterbalanced by improvements in wastewater treatment and agricultural practices. Mean SRP concentration in northeastern tributaries was significantly (p < 0.001) higher than in Fall Creek, likely reflecting more intense agricultural use and higher septic system density in the watersheds of the former. This finding justifies continued monitoring of minor northern tributaries. Future monitoring must emphasize the capture of high flow conditions. Historical stability and highly variable hydrology will slow the watershed response to management and confound the ability to detect changes attributable to decreased phosphorus inputs. Large scale monitoring on decadal timescales will be necessary to facilitate watershed management.

Addressing the Problem of Harmful Algal Blooms in Latin America and the Caribbean- A Regional Network for Early Warning and Response

La proliferacion de algas nocivas (HAB) constituye un problema mundial que afecta a los organismos acuaticos. Ecosistemas, salud publica y economias locales. Con el apoyo de la Agencia Internacional de Energia Atomica desde 2009, paises de America Latina y el Caribe (ALC), incluidos Brasil, Chile, Colombia, Costa Rica, Cuba, Republica Dominicana, El Salvador, Guatemala, Haiti, Mexico, Nicaragua, Panama, Uruguay y Venezuela, han integrado un plan regional Red para la alerta temprana de HABs y biotoxinas en mariscos. Las capacidades tecnicas tienen desarrollado a nivel regional para identificar especies toxicas, evaluar la toxicidad de la biota y realizar analisis retrospectivo de ocurrencia de HAB. Esta red involucra el 58% de los paises costeros de ALC, dos centros de referencia regionales (en El Salvador y Cuba), 14 instituciones bien equipadas y 177 profesionales capacitados para contribuir a la operacion de programas de monitorizacion de HAB y biotoxinas. Todos los paises de la red han reportado especies toxicas planctonicas y bentonicas, y en casos seleccionados, asociadas con toxinas en biota. El analisis de la abundancia de dinocistos en nucleos de sedimentos fechados en 210Pb ha demostrado que algunas especies daninas han estado presentes en la region por al menos 100 anos, y que tanto la contaminacion del agua costera como el cambio climatico son factores importantes para HAB ocurrencia. Se deben hacer esfuerzos para enriquecer los registros de la base de datos en eventos HAB ocurridos en ALC, se comprenden mejor las variables ambientales clave que controlan los HAB y ampliar la cobertura del monitoreo de HAB a todos los paises costeros de ALC para promover el desarrollo sostenible de la region.

Harmful Algal Blooms Get “Hotter” in 2018

Harmful Algal Blooms Get “Hotter” in 2018

Moving Forward: Legal Solutions to Lake Erie's Harmful Algal Blooms

Harmful algal blooms (HABs) have been plaguing Lake Erie with increasing frequency and intensity in recent years. The problem reached crisis proportions in August 2014 when nearly half a million persons in the Toledo, Ohio area were left without safe drinking water when a toxin produced by HABs in Lake Erie was detected at elevated levels in the city’s public water supply system. Excess nutrients entering the lake, especially phosphorus from nonpoint sources, are the primary contributors to the HABs problem in Lake Erie.This report, commissioned by the Commissioners of Lucas County, Ohio, offers legal solutions to Lake Erie’s HABs problem. After providing some scientific background, the report describes the complex web of federal and Ohio laws applicable to key sources of phosphorus pollution, explores legal tools that other regions such as the Chesapeake Bay are using to combat nutrient pollution, and makes recommendations for using and improving the law in Ohio and the region to reduce HABs in Lake Erie. Grant funding opportunities at the federal and state level also are identified.

The catastrophic 2008–2009 red tide in the Arabian gulf region, with observations on the identification and phylogeny of the fish-killing dinoflagellate Cochlodinium polykrikoides

Harmful algal blooms (HABs) caused by the marine ichthyotoxic dinoflagellate Cochlodinium polykrikoides Margalef are responsible for mass mortalities of wild and farmed fish worldwide, with catastrophic impacts to aquaculture and local economies. Here we report on the Cochlodinium species responsible for a severe and widespread HAB in the Arabian Gulf and Gulf of Oman that has lasted for more than eight months at this writing, killing thousands of tons of fish and limiting traditional fishery operations, damaging coral reefs, impacting coastal tourism, and forcing the closure of desalination plants in the region. To identify the causative organism, cultures were established from cells isolated along the Arabian Gulf shore of the United Arab Emirates. Taxonomic analyses using scanning and light microscopy, and partial analysis of the large subunit (LSU) ribosomal RNA (rRNA) gene confirmed the C. polykrikoides classification. rRNA gene sequences of C. polykrikoides isolates from the Arabian Gulf were identical to isolates from the northeastern USA, Puerto Rico, Mexico, and Malaysia, known as the “American/Malaysian” ribotype. To our knowledge, this is the first HAB event associated with C. polykrikoides in the Arabian Gulf or the Gulf of Oman. The sudden emergence of C. polykrikoides in these Gulfs coincides with an apparent global expansion of this taxon, as well as a recent increase in HAB impacts observed in this region. The mechanisms underlying this expansion require further investigation, and may include increased nutrient enrichment of coastal waters in the Arabian Gulf and Gulf of Oman from domestic and industrial inputs, natural meteorological and oceanographic forcings, and the recent introduction of this species through ballast water discharge. A pattern of subsequent recurrence of C. polykrikoides blooms following an initial outbreak has been observed in other parts of the world, suggesting that this species may become a persistent HAB problem in this region. As Arabian Gulf countries rely on desalination plants as the primary source of freshwater, the disruption of plant operations by recurring Cochlodinium blooms poses a serious threat to the drinking water supply in the region, and represents an unprecedented HAB impact.

Approaches to monitoring, control and management of harmful algal blooms (HABs)

Virtually every coastal country in the world is affected by harmful algal blooms (HABs, commonly called “red tides”). These phenomena are caused by blooms of microscopic algae. Some of these algae are toxic, and can lead to illness and death in humans, fish, seabirds, marine mammals, and other oceanic life, typically as a result of the transfer of toxins through the food web. Sometimes the direct release of toxic compounds can be lethal to marine animals. Non-toxic HABs cause damage to ecosystems, fisheries resources, and recreational facilities, often due to the sheer biomass of the accumulated algae. The term “HAB” also applies to non-toxic blooms of macroalgae (seaweeds), which can cause major ecological impacts such as the displacement of indigenous species, habitat alteration and oxygen depletion in bottom waters. Globally, the nature of the HAB problem has changed considerably over the last several decades. The number of toxic blooms, the resulting economic losses, the types of resources affected, and the number of toxins and toxic species have all increased dramatically. Some of this expansion has been attributed to storms, currents and other natural phenomena, but human activities are also frequently implicated. Humans have contributed by transporting toxic species in ballast water, and by adding massive and increasing quantities of industrial, agricultural and sewage effluents to coastal waters. In many urbanized coastal regions, these inputs have altered the size and composition of the nutrient pool which has, in turn, created a more favorable nutrient environment for certain HAB species. The steady expansion in the use of fertilizers for agricultural production represents a large and worrisome source of nutrients in coastal waters that promote some HABs. The diversity in HAB species and their impacts presents a significant challenge to those responsible for the management of coastal resources. Furthermore, HABs are complex oceanographic phenomena that require multidisciplinary study ranging from molecular and cell biology to large-scale field surveys, numerical modelling, and remote sensing from space. Our understanding of these phenomena is increasing dramatically, and with this understanding comes technologies and management tools that can reduce HAB incidence and impact. Here I summarize the global HAB problem, its trends and causes, and new technologies and approaches to monitoring, control and management, highlighting molecular probes for cell detection, rapid and sensitive toxin assays, remote sensing detection and tracking of blooms, bloom control and mitigation strategies, and the use of large-scale physical/biological models to analyze past blooms and forecast future ones.

A bacterium that inhibits the growth of Pfiesteria piscicida and other dinoflagellates

Toxic dinoflagellate blooms have increased in estuaries of the east coast of the United States in recent years, and the discovery of Pfiesteria piscicida has brought renewed attention to the problem of harmful algal blooms (HAB) in general. Many bacteria and viruses have been isolated that have algicidal or algistatic effects on phytoplankton, including HAB species. Twenty-two bacterial isolates from the Delaware Inland Bays were screened for algicidal activity. One isolate ( Shewanella IRI-160) had a growth-inhibiting effect on all three dinoflagellate species tested, including P. piscicida (potentially toxic zoospores), Prorocentrum minimum, and Gyrodinium uncatenum. This bacterium did not have a negative effect on the growth of any of the other four common estuarine non-dinoflagellate species tested, and in fact had a slight stimulatory effect on a diatom, a prasinophyte, a cryptophyte, and a raphidophyte. Shewanella IRI-160 is the first non-microzooplankton example of a microbe with the ability to control and inhibit the growth of P. piscicida, suggesting that bacteria in the natural environment could play a role in controlling the growth and abundance of P. piscicida and other dinoflagellates. Such bacteria could also potentially be used as management tools to prevent the proliferation of potentially harmful dinoflagellates in estuaries and coastal waters.

Harmful algal blooms and eutrophication: Nutrient sources, composition, and consequences

Although algal blooms, including those considered toxic or harmful, can be natural phenomena, the nature of the global problem of harmful algal blooms (HABs) has expanded both in extent and its public perception over the last several decades. Of concern, especially for resource managers, is the potential relationship between HABs and the accelerated eutrophication of coastal waters from human activities. We address current insights into the relationships between HABs and eutrophication, focusing on sources of nutrients, known effects of nutrient loading and reduction, new understanding of pathways of nutrient acquisition among HAB species, and relationships between nutrients and toxic algae. Through specific, regional, and global examples of these various relationships, we offer both an assessment of the state of understanding, and the uncertainties that require future research efforts. The sources of nutrients poten- tially stimulating algal blooms include sewage, atmospheric deposition, groundwater flow, as well as agricultural and aquaculture runoff and discharge. On a global basis, strong correlations have been demonstrated between total phos- phorus inputs and phytoplankton production in freshwaters, and between total nitrogen input and phytoplankton pro- duction in estuarine and marine waters. There are also numerous examples in geographic regions ranging from the largest and second largest U.S. mainland estuaries (Chesapeake Bay and the Albemarle-Pamlico Estuarine System), to the Inland Sea of Japan, the Black Sea, and Chinese coastal waters, where increases in nutrient loading have been linked with the development of large biomass blooms, leading to anoxia and even toxic or harmful impacts on fisheries re- sources, ecosystems, and human health or recreation. Many of these regions have witnessed reductions in phytoplankton biomass (as chlorophyll a) or HAB incidence when nutrient controls were put in place. Shifts in species composition have often been attributed to changes in nutrient supply ratios, primarily N:P or N:Si. Recently this concept has been extended to include organic forms of nutrients, and an elevation in the ratio of dissolved organic carbon to dissolved organic nitrogen (DOC:DON) has been observed during several recent blooms. The physiological strategies by which different groups of species acquire their nutrients have become better understood, and alternate modes of nutrition such as heterotrophy and mixotrophy are now recognized as common among HAB species. Despite our increased un- derstanding of the pathways by which nutrients are delivered to ecosystems and the pathways by which they are assimilated differentially by different groups of species, the relationships between nutrient delivery and the development of blooms and their potential toxicity or harmfulness remain poorly understood. Many factors such as algal species presence/ abundance, degree of flushing or water exchange, weather conditions, and presence and abundance of grazers contribute to the success of a given species at a given point in time. Similar nutrient loads do not have the same impact in different environments or in the same environment at different points in time. Eutrophication is one of several mechanisms by which harmful algae appear to be increasing in extent and duration in many locations. Although important, it is not the only explanation for blooms or toxic outbreaks. Nutrient enrichment has been strongly linked to stimulation of some harmful species, but for others it has not been an apparent contributing factor. The overall effect of nutrient over- enrichment on harmful algal species is clearly species specific.