Molecular approaches to diagnosing nutritional physiology in harmful algae: Implications for studying the effects of eutrophication

Every year harmful algal blooms (HABs) cause serious impacts to local economies, coastal ecosystems, and human health on a global scale. It is well known that nutrient availability can influence important aspects of harmful algae biology and ecology, such as growth, toxin production, and life cycle stage, as well as bloom initiation, persistence and decline. Increases in the rate of supply of organic matter to ecosystems (eutrophication) carries many possible ramifications to coastal systems, including the potential for nutrient enrichment and the potential for stimulation of harmful algal blooms. Traditional studies on algal nutrition typically use either cultured isolates or community level assays, to examine nutrient uptake, nutrient preference, elemental composition, and other metrics of a species’ response to nutrients. In the last decade, technological advances have led to a great increase in the number of sequences available for critical harmful species. This, in turn, has led to new insights with regards to algal nutrition, and these advances highlight the promise of molecular technologies, and genomic approaches, to improving our understanding of algal nutrient acquisition and nutritional physiological ecology, in both cultures and field populations. With these developments increased monitoring of nutritional physiology in field populations of harmful algae will allow us to better discriminate how eutrophication impacts these groups.     

Harmful algal blooms and eutrophication: Examining linkages from selected coastal regions of the United States

Coastal waters of the United States (U.S.) are subject to many of the major harmful algal bloom (HAB) poisoning syndromes and impacts. These include paralytic shellfish poisoning (PSP), neurotoxic shellfish poisoning (NSP), amnesic shellfish poisoning (ASP), ciguatera fish poisoning (CFP) and various other HAB phenomena such as fish kills, loss of submerged vegetation, shellfish mortalities, and widespread marine mammal mortalities. Here, the occurrences of selected HABs in a selected set of regions are described in terms of their relationship to eutrophication, illustrating a range of responses. Evidence suggestive of changes in the frequency, extent or magnitude of HABs in these areas is explored in the context of the nutrient sources underlying those blooms, both natural and anthropogenic. In some regions of the U.S., the linkages between HABs and eutrophication are clear and well documented, whereas in others, information is limited, thereby highlighting important areas for further research.     

Improved monitoring of HABs using autonomous underwater vehicles (AUV)

Blooms of toxic algae are increasing in magnitude and frequency around the globe, causing extensive economic and environmental impacts. On the west coast of Florida, blooms of the toxic dinoflagellate Karenia brevis (Davis) have been documented annually for the last 30 years causing respiratory irritation in humans, fish kills, and toxin bioaccumulation in shellfish beds. As a result, methods need to be established to monitor and predict bloom formation and transport to mitigate their harmful effects on the surrounding ecosystems and local communities. In the past, monitoring and mitigation efforts have relied on visual confirmation of water discoloration, fish kills, and laborious cell counts, but recently satellite remote sensing has been used to track harmful algal blooms (HABs) along the Florida coast. Unfortunately satellite ocean color is limited by cloud cover, lack of detection below one optical depth, and revisit frequency, all of which can lead to extended periods without data. To address these shortcomings, an optical phytoplankton discriminator (OPD) was developed to detect K. brevis cells in mixed phytoplankton assemblages. The OPD was integrated into autonomous underwater vehicle (AUV) platforms to gather spatially and temporally relevant data that can be used in collaboration with satellite imagery to provide a 3D picture of bloom dynamics over time. In January 2005, a Remote Environmental Monitoring UnitS (REMUS) AUV with an OPD payload was deployed on the west coast of Florida to retrieve a similarity index (SI), which indicates when K. brevis dominates the phytoplankton community. SI was used to monitor a K. brevis bloom in relation to temperature, salinity, chlorophyll, and ocean currents. Current speed, SI, temperature, salinity, and chlorophyll a from the AUV were used to quantify a 1 km displacement of the K. brevis bloom front that was observed over the deployment period. The ability to monitor short term bloom movement will improve monitoring and predictive efforts that are used to provide warnings for local tourism and fishing industries. In addition, understanding the fine scale environmental conditions associated with bloom formation will increase our ability to predict the location and timing of K. brevis bloom formation. This study demonstrates the use of one autonomous platform and provides evidence that a nested array of AUVs and moorings equipped with new sensors, combined with remote sensing, can provide an early warning and monitoring system to reduce the impact of HABs.     

沿岸海域富营养化与赤潮发生的关系

综述了赤潮的发生与沿岸海域富营养化的关系。近几十年来,人类活动使得天然水体的富营养化进程大大加速。营养负荷的增加与高生物量水华的增多相联系。控制营养输入后,浮游植物生物量或有害藻类水华事件也相应减少。营养的组成与浮游植物的种类组成及水华的形成有密切联系。有机营养对有害藻类水华的促进作用受到关注。营养输入时机影响浮游植物种间竞争的结果,因而对浮游植物的群落演替具有深远影响。由于浮游植物存在生理差异,因而对营养加富的反应因种而异。营养在调控某些有毒藻类的毒素产量方面也发挥着重要作用。此外,营养输入与藻类水华之间存在复杂的间接联系。当然,营养状况并非浮游植物群落演替的唯一决定因素。研究结果提示,控制营养输入、减缓水域富营养化是减少有害藻类水华发生的有效途径,而深入研究典型有害藻类的营养生理对策则为防治并最终消除有害藻类水华提供了理论基础。     

POSITIVE FEEDBACK AND THE DEVELOPMENT AND PERSISTENCE OF ECOSYSTEM DISRUPTIVE ALGAL BLOOMS1

Harmful algal blooms (HABs) have occurred with increasing frequency in recent years with eutrophication and other anthropogenic alterations of coastal ecosystems. Many of these blooms severely alter or degrade ecosystem function, and are referred to here as ecosystem disruptive algal blooms (EDABs). These blooms are often caused by toxic or unpalatable species that decrease grazing rates by planktonic and benthic herbivores, and thereby disrupt the transfer of nutrients and energy to higher trophic levels, and decrease nutrient recycling. Many factors, such as nutrient availability and herbivore grazing have been proposed to separately influence EDAB dynamics, but interactions among these factors have rarely been considered. Here we discuss positive feedback interactions among nutrient availability, herbivore grazing, and nutrient regeneration, which have the potential to substantially influence the dynamics of EDAB events. The positive feedbacks result from a reduction of grazing rates on EDAB species caused by toxicity or unpalatability of these algae, which promotes the proliferation of the EDAB species. The decreased rates also lower grazer‐mediated recycling of nutrients and thereby decrease nutrient availability. Since many EDAB species are well‐adapted to nutrient‐stressed environments and many exhibit increased toxin production and toxicity under nutrient limitation, positive feedbacks are established which can greatly increase the rate of bloom development and the adverse effects on the ecosystem. An understanding of how these feedbacks interact with other regulating factors, such as benthic/pelagic nutrient coupling, physical forcing, and life cycles of EDAB species provides a substantial future challenge.     

Applications of Satellite Ocean Color Sensors for Monitoring and Predicting Harmful Algal Blooms

The new satellite ocean color sensors offer a means of detecting and monitoring algal blooms in the ocean and coastal zone. Beginning with SeaWiFS (Sea Wide Field-of-view Sensor) in September 1997, these sensors provide coverage every 1 to 2 days with 1-km pixel view at nadir. Atmospheric correction algorithms designed for the coastal zone combined with regional chlorophyll algorithms can provide good and reproducible estimates of chlorophyll, providing the means of monitoring various algal blooms. Harmful algal blooms (HABs) caused by Karenia brevis in the Gulf of Mexico are particularly amenable to remote observation. The Gulf of Mexico has relatively clear water and K. brevis, in bloom conditions, tends to produce a major portion of the phytoplankton biomass. A monitoring program has begun in the Gulf of Mexico that integrates field data from state monitoring programs with satellite imagery, providing an improved capability for the monitoring of K. brevis blooms.     

Assessing and managing nutrient-enhanced eutrophication in estuarine and coastal waters: Interactive effects of human and climatic perturbations

Estuaries are among the most productive, resourceful, and dynamic aquatic ecosystems on Earth. Their productive nature is linked to the fact that they process much of the world's riverine and coastal watershed discharge. These watersheds support more than 75% of the human population and are sites of large increases in nutrient loading associated with urban and agricultural expansion. Increased nutrient loading has led to accelerated primary production, or eutrophication; symptoms include increased algal bloom activity (including harmful taxa), accumulation of organic matter, and excessive oxygen consumption (hypoxia and anoxia). While nutrient-enhanced eutrophication is a “driver” of hypoxia and anoxia, physical–chemical alterations due to climatic events, such as stormwater discharge, flooding, droughts, stagnancy, and elevated temperatures are also involved. The complex interactions of anthropogenic and climatic factors determine the magnitude, duration, and aerial extent of productivity, algal booms, hypoxia, and anoxia. Using the eutrophic Neuse River Estuary (NRE), North Carolina, USA, as a case study, the physical–chemical mechanisms controlling algal bloom and hypoxia dynamics were examined. Because primary production in the NRE and many other estuaries is largely nitrogen (N) limited, emphasis has been placed on reducing N inputs. Both the amounts and chemical forms of N play roles in determining the composition and extent of phytoplankton blooms that supply the bulk of the organic carbon fueling hypoxia. Biomass from bloom organisms that are readily grazed will be readily transferred up the planktonic and benthic food chain, while toxic or inedible blooms frequently promote sedimentary C flux, microbial mineralization, and hence may exacerbate hypoxia potential. From a watershed perspective, nutrient input reductions are the main options for reducing eutrophication. Being able to distinguish the individual and cumulative effects of physical, chemical and biotic controls of phytoplankton productivity and composition is key to understanding, predicting, and ultimately managing eutrophication. Long-term collaborative (University, State, Federal) monitoring, experimental assessments, and modeling of eutrophication dynamics over appropriate spatial and temporal scales is essential for developing realistic, ecologically sound, and cost-effective nutrient management strategies for estuarine and coastal ecosystems impacted by both anthropogenic and climatic perturbations.     

A comparison of N and C uptake during brown tide (Aureococcus anophagefferens) blooms from two coastal bays on the east coast of the USA

Blooms of the brown tide pelagophyte, Aureococcus anophagefferens, have been reported in coastal bays along the east coast of the USA for nearly two decades. Blooms appear to be constrained to shallow bays that have low flushing rates, little riverine input and high salinities (e.g., >28). Nutrient enrichment and coastal eutrophication has been most frequently implicated as the cause of A. anophagefferens and other blooms in coastal bays. We compare N and C dynamics during two brown tide blooms, one in Quantuck Bay, on Long Island, NY in 2000, and the other in Chincoteague Bay, at Public Landing, MD in 2002, with a physically similar site in Chincoteague Bay that did not experience a bloom. We found that the primary forms of nitrogen (N) taken up during the bloom in Quantuck Bay were ammonium and dissolved free amino acids (DFAA) while the primary form of N fueling production at both sites in Chincoteague Bay was urea. At both Chincoteague sites, amino acid carbon (C) was taken up while urea C was not. Even though A. anophagefferens has the ability to take up organic C, during the bloom at Chincoteague Bay, photosynthetic uptake of bicarbonate was the dominant pathway of C acquisition by the >1.2 μm size fraction during the day. C uptake by cells <5.0 μm was insufficient to meet cellular C demand based on the measured N uptake rates and the C:N ratio of particulate material. While cells >1.2 μm did not take up much organic C during the day, smaller cells (>0.2 μm) did. Peptide hydrolysis appeared to play an important role in mobilizing organic matter in Quantuck Bay, where amino acids contributed substantially to N and C uptake, but not in Chincoteague Bay. Dissolved organic N (DON), dissolved organic C (DOC) concentrations and the DOC/DON ratio were higher and total dissolved inorganic N (DIN) concentrations were lower at the bloom site in Chincoteague Bay than at the nonbloom site in the same bay. We conclude that A. anophagefferens is capable of using a wide variety of N and C compounds, and that nutrient inputs, biotic interactions and the dominant recycling pathways determine which compounds are available and which metabolic pathways are active at a particular site.     

Severe Karenia brevis red tides influence juvenile bottlenose dolphin (Tursiops truncatus) behavior in Sarasota Bay,Florida

Harmful algal blooms (HABs) are natural stressors in the coastal environment that may be increasing in frequency and severity. This study investigates whether severe red tide blooms, caused by Karenia brevis, affect the behavior of resident coastal bottlenose dolphins in Sarasota Bay, Florida through changes to juvenile dolphin activity budgets, ranging patterns, and social associations. Behavioral observations were conducted on free‐ranging juvenile dolphins during the summer months of 2005–2007, and behavior during red tide blooms was compared to periods of background K. brevis abundance. We also utilized dolphin group sighting data from 2004 to 2007 to obtain comparison information from before the most severe recent red tide of 2005 and incorporate social association information from adults in the study area. We found that coastal dolphins displayed a suite of behavioral changes associated with red tide blooms, including significantly altered activity budgets, increased sociality, and expanded ranging behavior. At present, we do not fully understand the mechanism behind these red tide‐associated behavioral effects, but they are most likely linked to underlying changes in resource availability and distribution. These behavioral changes have implications for more widespread population impacts, including increased susceptibility to disease outbreaks, which may contribute to unusual mortality events during HABs.     

Spatial-temporal dynamics of red tide precursor organisms at the Pacific coast of North and Central America

The Pacific coast of Central and North America has long been and still is impacted by the flourishing of microalgal populations known as Harmful Algal Blooms (HABs). The organisms that have caused recent HABs episodes in the region are among others, Gymnodinium catenatum, Pyrodinium bahamense var. compressum, and recently Cochlodinium cf. catenatum. In spite of the accumulated effects on the human health, the economic activities and the environment, scarce information is available on the subject. The augmented use of coastal zones for human activities is also paralleled by increased awareness of global climate changes. Thus, it is not an easy task to discriminate anthropogenic or natural phenomena, or both, as the major driving forces. The long-term data sets available for limited regions, as well as some sporadic observations during notorious blooms, allowed us to discriminate major changes in the biodiversity and biogeography of HAB organisms. Main changes refer to number of events, covered area, duration and frequency, number of blooming species and appearance of not previously reported harmful taxa. The variables more clearly related to these dynamic phenomena, seems to be sea surface temperature and wind force, but it is not yet possible to weight their contributions. The participation of rain is not fully evaluated to date. The collaborative communication among small-budget monitoring operations in the region allowed to "pass the voice" about peaking concentrations of HAB organisms, diminishing the risk of poisoning.     

The Diversity of Harmful Algal Bloom-Triggering Mechanisms and the Complexity of Bloom Initiation

Mechanisms influencing initiation of harmful algal blooms (HABs) are diverse, and are not likely to be mutually exclusive. Rather, initiation of HABs is a result of interactions between processes, which result in biological, physical, and chemical conditions optimal for a bloom. Due to the complexity of some bloom initiation processes, bloom-preventative management may be possible. Results from a modeling exercise and a laboratory experiment indicated that a phytoplankton bloom could be circumvented through manipulation of the nutrient-loading mode, i.e., pulsed vs. continuous loading. These findings, should they prove consistent in more robust field experiments, may provide insights for the development of new management approaches for some HABs. Optimal bloom conditions, however, vary between HAB species. Consequently, it is unlikely that a single management solution will exist. Preventative management efforts will require early warning of HAB initiation, perhaps even before the appearance of an HAB species. An indicator based on the dynamic nature of phytoplankton succession events and phytoplankton species diversity may prove useful for this purpose. Applying this index to an existing plankton data set showed that Microcystis blooms might have been predicted months before the start of the bloom.     

Prorocentrum minimum (Pavillard) Schiller: A review of a harmful algal bloom species of growing worldwide importance

Prorocentrum minimum (Pavillard) Schiller, a common, neritic, bloom-forming dinoflagellate, is the cause of harmful blooms in many estuarine and coastal environments. Among harmful algal bloom species, P. minimum is important for the following reasons: it is widely distributed geographically in temperate and subtropical waters; it is potentially harmful to humans via shellfish poisoning; it has detrimental effects at both the organismal and environmental levels; blooms appear to be undergoing a geographical expansion over the past several decades; and, a relationship appears to exist between blooms of this species and increasing coastal eutrophication. Although shellfish toxicity with associated human impacts has been attributed to P. minimum blooms from a variety of coastal environments (Japan; France; Norway; Netherlands; New York, USA), only clones isolated from the Mediterranean coast of France, and shellfish exposed to P. minimum blooms in this area, have been shown to contain a water soluble neurotoxic component which killed mice. Detrimental ecosystem effects associated with blooms range from fish and zoobenthic mortalities to shellfish aquaculture mortalities, attributable to both indirect biomass effects (e.g., low dissolved oxygen) and toxic effects. P. minimum blooms generally occur under conditions of high temperatures and incident irradiances and low to moderate salinities in coastal and estuarine environments often characterized as eutrophic, although they have been found under widely varying salinities and temperatures if other factors are conducive for growth. The physiological flexibility of P. minimum in response to changing environmental parameters (e.g., light, temperature, salinity) as well as its ability to utilize both inorganic and organic nitrogen, phosphorus, and carbon nutrient sources, suggest that increasing blooms of this species are a response to increasing coastal eutrophication.     

大型海藻龙须菜与东海原甲藻间的营养竞争

生物方法作为一种新兴的赤潮防治方法,因为其作用的专一性及较少的负效应,越来越受到人们的重视。研究了龙须菜(G racilaria lem aneif orm is)与东海原甲藻(P rorocentrum d ongha iense)之间营养盐NO3-、PO43-竞争的情况。结果显示,两者共培养时,龙须菜对营养盐的快速吸收利用,使得共培养体系中营养盐迅速降低,最终导致东海原甲藻消亡,而东海原甲藻对于龙须菜的生长不构成明显的影响。在营养盐充分的条件下,1g鲜重的龙须菜对NO3-的吸收能力相当于6.0×107个东海原甲藻细胞,对PO43-的吸收相当于2.4×107个东海原甲藻细胞。相对于东海原甲藻,龙须菜对营养盐的吸收利用更具有优势。龙须菜可作为有效吸收营养盐的大型海藻,用以降低近海水域富营养化程度及有害赤潮发生的几率。     

Monitoring Karenia brevis blooms in the Gulf of Mexico using satellite ocean color imagery and other data

Harmful algal blooms (HABs) of Karenia brevis are a recurrent problem in the Gulf of Mexico, with nearly annual occurrences on the Florida southwest coast, and fewer occurrences on the northwest Florida and Texas coasts. Beginning in 1999, the National Oceanic and Atmospheric Administration has issued the Gulf of Mexico HAB Bulletins to support state monitoring and management efforts. These bulletins involve analysis of satellite imagery with field and meteorological station data. The effort involves several components or models: (a) monitoring the movement of an algal bloom that has previously been identified as a HAB (type 1 forecast); (b) detecting new blooms as HAB or non-HAB (type 2); (c) predicting the movement of an identified HAB (type 3); (d) predicting conditions favorable for a HAB to occur where blooms have not yet been observed (type 4). The types 1 and 2 involve methods of bloom detection requiring routine remote sensing, especially satellite ocean color imagery and in situ data. Prediction (types 3 and 4) builds on the monitoring capability by using interpretative and numerical modeling. Successful forecasts cover more than 1000 km of coast and require routine input of remotely sensed and in situ data.The data sources used in this effort include ocean color imagery from the Sea-Viewing Wide Field-of-View Sensor/OrbView-2 satellite and processed using coastal-specific algorithms, wind data from coastal and offshore buoys, field observations of bloom location and intensity provided by state agencies, and forecasts from the National Weather Service. The HAB Bulletins began in coordination with the state of Florida in autumn of 1999 and included K. brevis bloom monitoring (type 1), with limited advisories on transport (type 3) and the detection of blooms in new areas (type 2). In autumn 2000, we improved both the transport forecasts and detection capabilities and began prediction of conditions favorable for bloom development (type 4). The HAB Bulletins have had several successes. The state of Florida was advised of the potential for a bloom to occur at the end of September 2000 (type 4), and the state was alerted to the position of blooms in January 2000 and October 2001 in areas that had not been previously sampled (type 3). These successful communications of HAB activity allowed Florida agencies responsible for shellfish management and public health to respond to a rapidly developing event in a timely, efficient manner.     

The potential role of anthropogenically derived nitrogen in the growth of harmful algae in California,USA

Cultural eutrophication is frequently invoked as one factor in the global increase in harmful algal blooms, but is difficult to definitively prove due to the myriad of factors influencing coastal phytoplankton bloom development. To assess whether eutrophication could be a factor in the development of harmful algal blooms in California (USA), we review the ecophysiological potential for urea uptake by Pseudo-nitzschia australis (Bacillariophyceae), Heterosigma akashiwo (Raphidophyceae), and Lingulodinium polyedrum (Dinophyceae), all of which have been found at bloom concentrations and/or exhibited noxious effects in recent years in California coastal waters. We include new measurements from a large (Chlorophyll a > 500 mg m⁻³) red tide event dominated by Akashiwo sanguinea (Dinophyceae) in Monterey Bay, CA during September 2006. All of these phytoplankton are capable of using nitrate, ammonium, and urea, although their preference for these nitrogenous substrates varies. Using published data and recent coastal time series measurements conducted in Monterey Bay and San Francisco Bay, CA, we show that urea, presumably from coastal eutrophication, was present in California waters at measurable concentrations during past harmful algal bloom events. Based on these observations, we suggest that urea uptake could potentially sustain these harmful algae, and that urea, which is seldom measured as part of coastal monitoring programs, may be associated with these harmful algal events in California.     

Examination of Ulva bloom species richness and relative abundance reveals two cryptically co-occurring bloom species in Narragansett Bay,Rhode Island

Blooms caused by the green macroalga Ulva pose a serious threat to coastal ecosystems around the world. Despite numerous studies of the causes and consequences of these blooms, we still have a limited understanding of Ulva bloom species richness and abundance due to difficulties in identifying Ulva species using morphological features. Along the northeastern U.S. coastline, all blooms of distromatic Ulva blades were previously identified as Ulva lactuca. Recent molecular sequencing, however, discovered the presence of additional distromatic Ulva species. Therefore, in order to determine the relative abundance of Ulva species within blooms, we conducted monthly surveys at four Narragansett Bay, RI, sites representing a gradient of bloom severity. We found that the biomass of Ulva within blooms was a mix of Ulva compressa and Ulva rigida, not U. lactuca as previously reported. In contrast, sites not impacted by blooms that were located near the mouth of Narragansett Bay were dominated by U. lactuca. We also observed spatial and temporal differences in Ulva and total macroalgal diversity between bloom-impacted sites, indicating that Ulva bloom composition can be radically different between similar sites within close proximity. We discuss our results in the context of Ulva blooms worldwide, highlighting the need to definitively determine bloom species composition in order to fully understand bloom dynamics.     

Vulnerability of coastal ecosystems to changes in harmful algal bloom distribution in response to climate change: projections based on model analysis

Harmful algal blooms (HABs), those proliferations of algae that can cause fish kills, contaminate seafood with toxins, form unsightly scums, or detrimentally alter ecosystem function have been increasing in frequency, magnitude, and duration worldwide. Here, using a global modeling approach, we show, for three regions of the globe, the potential effects of nutrient loading and climate change for two HAB genera, pelagic Prorocentrum and Karenia, each with differing physiological characteristics for growth. The projections (end of century, 2090–2100) are based on climate change resulting from the A1B scenario of the Intergovernmental Panel on Climate Change Institut Pierre Simon Laplace Climate Model (IPCC, IPSL‐CM4), applied in a coupled oceanographic‐biogeochemical model, combined with a suite of assumed physiological ‘rules’ for genera‐specific bloom development. Based on these models, an expansion in area and/or number of months annually conducive to development of these HABs along the NW European Shelf‐Baltic Sea system and NE Asia was projected for both HAB genera, but no expansion (Prorocentrum spp.), or actual contraction in area and months conducive for blooms (Karenia spp.), was projected in the SE Asian domain. The implications of these projections, especially for Northern Europe, are shifts in vulnerability of coastal systems to HAB events, increased regional HAB impacts to aquaculture, increased risks to human health and ecosystems, and economic consequences of these events due to losses to fisheries and ecosystem services.     

Eutrophication and harmful algal blooms: A scientific consensus

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 other nations;
• (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 about the role of nutrients in HABs 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 are provided herein.     

Molecular cloning reveals co-occurring species behind red tide blooms of the harmful dinoflagellate Cochlodinium polykrikoides

Red tides caused by the marine dinoflagellate Cochlodinium polykrikoides Margalef pose significant environmental problems worldwide. Recently, the existence of severe blooms attributable to a single Cochlodinium Schütt species has been questioned by many researchers. Herein we investigated the dinoflagellate composition of harmful algal blooms (HABs) attributed to C. polykrikoides in Korean coastal waters at nine different stations (St.). The component species of Cochlodinium blooms were examined by using microscopic and gene-cloning methods. In the nine study areas, C. polykrikoides was the predominant species of HABs in St. 2, 4, 7, and St. 9. Based on the morphological identification, the bloom was initially thought to be caused only by C. polykrikoides; however, we detected additional bloom-forming dinoflagellates (Polykrikos schwartzii Bütschli and Polykrikos kofoidii Chatton), and diatoms (Pseudo-nitzschia americana (Hasle) Fryxell) along with C. polykrikoides. The parasitic dinoflagellates Amoebophrya Koeppen and Euduboscquella Coats, Bachvaroff & Delwiche were found to be co-located with Cochlodinium in our study, and for the first time, Cochlodinium fulvescens Iwataki, Kawami & Matsuoka was detected in Korea (west coast). These results suggest co-existence of multiple dinoflagellates in bloom populations of Cochlodinium and describe the composition of other dinoflagellate blooms (e.g., Polykrikos spp.) in Korean coastal regions. This co-occurrence may be considered during efforts to monitor and control HABs.     

Combined physical,chemical and biological factors shape Alexandrium ostenfeldii blooms in The Netherlands

Harmful algal blooms (HABs) are globally expanding, compromising water quality worldwide. HAB dynamics are determined by a complex interplay of abiotic and biotic factors, and their emergence has often been linked to eutrophication, and more recently to climate change. The dinoflagellate Alexandrium is one of the most widespread HAB genera and its success is based on key functional traits like allelopathy, mixotrophy, cyst formation and nutrient retrieval migrations. Since 2012, dense Alexandrium ostenfeldii blooms (up to 4500 cells mL⁻¹) have recurred annually in a creek located in the southwest of the Netherlands, an area characterized by intense agriculture and aquaculture. We investigated how physical, chemical and biological factors influenced A. ostenfeldii bloom dynamics over three consecutive years (2013–2015). Overall, we found a decrease in the magnitude of the bloom over the years that could largely be linked to changing weather conditions during summer. More specifically, low salinities due to excessive rainfall and increased wind speed corresponded to a delayed A. ostenfeldii bloom with reduced population densities in 2015. Within each year, highest population densities generally corresponded to high temperatures, low DIN:DIP ratios and low grazer densities. Together, our results demonstrate an important role of nutrient availability, absence of grazing, and particularly of the physical environment on the magnitude and duration of A. ostenfeldii blooms. Our results suggest that predicted changes in the physical environment may enhance bloom development in future coastal waters and embayments.