Biological and Environmental Hazards, Risks, and Disasters

Biological and Environmental Hazards, Risks, and Disasters, Second Edition provides an integrated look at major impacts to the Earth’s biosphere caused by diseases, algal blooms, insects, animals, species extinction, deforestation, land degradation, and comet and asteroid strikes, with important implications for humans.

This second edition from Elsevier’s Hazards and Disasters Series incorporates perspectives from the natural and social sciences to offer in-depth coverage of threats from microscopic organisms to celestial objects and their potential impacts. Contributions from expert biological, health, ecological, environmental, wildlife, physical, and health scientists, readers will gain valuable insights on damages, causality, economic impacts, preparedness, and mitigation.

• Provides inter- and multi-disciplinary research accessible to both specialists and non-specialists
• Includes newly added chapters on emerging hazards and risks to earth’s ecosystems (land conversion and habitat loss) and human health (spread of diseases)
• Contains full-color tables, maps, diagrams, illustrations, and photographs of hazardous processes

• Language: English
• Publisher: Elsevier Science
• Release date: Jun 22, 2023
• ISBN: 9780128205808

Book preview

Chapter 1: Introduction

Ramesh Sivanpillai     Wyoming GIS Center, School of Computing, University of Wyoming, Laramie, WY, United States

Abstract

Humanity faces numerous biological and environmental hazards and risks from microbes to meteoroids. It is a daunting task to describe every risk and hazard in a single volume of this series. New and revised chapters are included in the second edition that addresses several important biological and environmental hazards and risks facing us today. Chapters are organized into two parts in this volume and deal with both natural and anthropogenic causes of threats at multiple scales.

Keywords

Asteroids; Biodiversity; Diseases; Ecosystems; Insects; Ionizing radiation; Land conversion; Microbes

The biotic components of Earth are connected by hierarchical, complex, and interconnected networks through which material and energy flow. Live cells are part of an organism, organisms are part of a population, populations are part of a community, communities are part of an ecosystem, ecosystems are part of a landscape, landscapes are part of a biome, and biomes are part of the entire biosphere. Ecologists study the components and processes at scales ranging from the physiology of small organisms to the carbon flow in the entire biosphere (Allen and Hoekstra, 1992). The structures and processes that are part of Earth's biosphere have evolved over several millions of years. When organisms are removed or go extinct from their habitat or ecosystem, or introduced to a different ecosystem, alterations in the structure and processes occur, resulting in the disruption of the stability of those ecosystems (Coztanza et al., 1992). Similarly, changes in abiotic components in ecosystems can alter the energy and material flow that occur within them. Any changes, minor or major, to the species composition or processes such as energy flow pose risks and hazards to Earth's environment and its biotic components. Anthropogenic activities have altered the balance between the biotic and abiotic components at every scale and have caused or resulted in changes to ecosystems.

It is a daunting task to capture all hazards and risks associated with the myriad processes and components in their entirety, in a single volume. Topics covered in the second edition of this volume represent several important risks and hazards. Other volumes published in this book series have captured the hazards, risks, and disasters associated with water, volcanoes, landslides, earthquakes, seas and oceans, snow and ice, and wildfires. This volume addresses several hazards, risks, and disasters that can be linked to other natural phenomena or anthropogenic activities.

Chapters included in this volume address several important hazards and risks that pose threats to the ecosystems throughout the world. The second edition contains both new and revised chapters from the first edition. They are organized into 2 parts: Biological and Environmental. The first part focuses on different organisms, and the threats posed by increases or decreases in their population or changes in their behavior. The second part addresses threats of natural and human origin faced by aquatic and terrestrial environments.

1.1. Part 1: Biological hazards, risks, and disasters

The first chapter on algal blooms (McGowan) overviews the organisms found in algal blooms and the risks it poses to humans and the environment. Algal bloom incidents have increased manyfold since 1970s resulting in health issues for humans and animals. This chapter includes an overview of recent advances in the monitoring and detection of algal blooms in addition to forecasting and treating them along with the challenges associated with nutrient fluxes.

The next five chapters deal with risks, hazards, and disasters associated with insects. Hazards posted to crops and other vegetation by grasshoppers present in the regions of North America and Sahel are illustrated by Schell and Le Gall et al., respectively. Locusts, when they form swarms consisting of millions of individuals, can wipe out crops and vegetation across large geographic areas. Desert locust (Schistocerca gregaria) outbreak that started in 2019 has decimated crops and other vegetation in 23 countries in Africa and Asia (GLI, 2022). Following an overview of Locusts (Lockwood), Adriaansen et al., and Poot-Pech discuss the impact of locusts for agriculture and environment in Australia and Central America, respectively.

Human-animal interactions are either beneficial or hazardous, leading to destruction and loss of lives on both sides. Using examples from different parts of the world, Tsikalas et al. provide an overview of animal hazards including zoonotic diseases. As habitats of many wildlife species continue to decline due to deforestation and expansion of agricultural activities, adverse interactions with humans and animals have continued to increase.

For example, human–elephant conflicts have escalated in southern India as elephant habitats, and their migration corridors are converted to settlements, manufacturing facilities, crop fields, tea plantations (Fig. 1.1, left), and other land uses.

Farmers have built electric (intended for nighttime use only) fences to protect their crops (Fig. 1.1, right). Government agencies have dug trenches along the forest border to prevent elephants from raiding crops in villages. However, elephants have found ways to break the fences or destroy the trenches. These interactions are often hostile and result in the death or injury to either elephants or humans.

Species extinction and their impact on biodiversity are described in the next essay (May). Jones et al. highlight the role of Sacred Groves present throughout Kerala (India) in preserving biodiversity and the current threats they are facing in the form of removal of trees and plants, increase in tourism and related activities such as converting areas in these fragile ecosystems to parking lots or restaurants to accomodate the growing number of visitors.

Figure 1.1  Examples of land conversion leading to increased incidents of human–elephant conflicts in southern India. Presence of tea estates (left) prevent elephant movement and electric fences (right) built to protect crops are leading to bodily injuries and even death for elephants.

The final chapter in the first part by Fatima et al. discusses the emerging challenges to antibiotic and antimicrobial treatment as microbes develop resistance to the drugs developed for treating or eliminating them. They examine the causes and current threats to public health.

1.2. Part 2: Environmental hazards, risks, and disasters

The second part of this book focuses on the threats to humanity from various environmental systems. The first chapter in the second part examines the causes of environmental chronic diseases along with responses to major disease outbreaks from different parts of the world (Beyer and Namin). Insights are provided for intervening and preparing to reduce future burdens.

Coral ecosystems are important for supporting ocean's biodiversity and van Woesik and Shlesinger describe how these fragile systems are threatened by thermal stress, which has caused extensive bleaching.

Several drivers of deforestation are witnessed in the different parts of the world. While some of them are natural causes such as drought or wildfires, human actions have been largely responsible for accelerating deforestation rates around the world. US Geological Survey (USGS) and NASA monitor deforestation and other earth surface changes. In a recent report, NASA scientists highlighted the primary forest loss in Bolivia (Fig. 1.2) approximately doubled from 2000 to 2022s (NASA Earth Observatory, 2022).

Following an overview chapter on deforestation by Houghton, two chapters highlight the causes and impact on deforestation in Nepal (Chaudhary et al.) and Southeast Asia (Turner and Snaddon). Naskar et al. describe how destruction of mangroves, another fragile ecosystem, adversely impacts millions of coastal communities that directly and indirectly rely on them. They also discuss the probable consequences of a mangrove free tropics due to a combination of climate change and human actions.

Land degradation and subsequent reduction in soil fertility pose a major risk to the entire human population. D'Odorico and Ravi introduce land degradation followed by two chapters that provide an in-depth analysis of the environmental risks and disasters associated with desertification (Harris and Oswald), and rangeland (Jay Angerer et al.) ecosystems.

Figure 1.2  Earth observation images acquired by landsat 5 in 1986 (left) and landsat 8 in 2022 (right) show how a series of deforestation in pinwheel and rectangular patterns have altered the chiqultano dry forest in Bolivia. Image courtesy of NASA Earth Observatory.

Diversion of water from the Amu-Darya and Syr-Darya rivers for growing cotton and crops collapsed the Aral Sea ecosystem (Fig. 1.3) and once thriving fishing industry (NASA Earth Observatory, 2019). The saline waters are unable to support most of the native aquatic lifeforms. Lioubimtseva describes how human actions combined with natural climate variability have altered what was once the fourth largest inland waterbody.

Figure 1.3  Earth observation images acquired in 2000 (left) and 2018 (right) by moderate resolution imaging spectrometer (MODIS) show impact of major water diversion project on Aral Sea located in Uzbekistan (south) and Kazakhstan (north). Image courtesy of NASA Earth Observatory.

Malanson and Alftine reviews the effects of past and ongoing climate changes on species and ecosystems and the services they provide. Examples from marine and terrestrial systems are used for illustrating the effects of rising sea levels, temperature variations, fire frequency, drought, insect outbreaks, and pathogens.

Nair describes the relationship between radiation toxicity and its dose and how regulation and science can get out of sync with each other. In the final chapter, risks and threats posed by potential meteoroids and asteroids impacting the Earth are described (de Hon).

While the topics covered in the second edition of this book address many important hazards, risks, and disasters, they are not exhaustive. Humanity faces more risks and hazards of various forms and magnitudes and must remain vigilant and adequately respond to them as needed. The COVID19 pandemic of 2019 killed several millions around the world and impacted every sphere of our day-to-day lives. It required a coordinated response from international, national, and local agencies to contain the outbreak and help those impacted by this virus and its mutants. Continued research in and assessment of threats to humans and outreach to public are vital for keeping these risks and hazards in the forefront of policy and decision-making process.

References

1. Allen, Hoekstra. Towards a Unified Ecology. New York. NY: Columbia University Press; 1992.

2. Coztanza, et al., ed. Ecosystem Health: New Goals for Environmental Management. Washington, DC: Island Press; 1992.

3. GLI (Global Locust Initiative). Desert Locust Outbreak. 2022. https://sustainability-innovation.asu.edu/global-locust-initiative/gli-desert-locust-outbreak/.

5. NASA Earth Observatory, 2019. World of Change: Shrinking Aral Sea. https://earthobservatory.nasa.gov/world-of-change/AralSea. (Accessed 9 October 2022).

4. NASA Earth Observatory. Patterns of Forest Change in Bolivia. 2022. https://earthobservatory.nasa.gov/images/150257/patterns-of-forest-change-in-bolivia.

Part I

Biological hazards, risks, and disasters

Outline

Chapter 2. Harmful algal blooms

Chapter 3. Grasshopper infestations and the risks they pose to western North America range and crop lands, North of Mexico

Chapter 4. Senegalese grasshopper—a major pest of the Sahel

Chapter 5. Locusts: An introduction

Chapter 6. The Australian plague locust—risk and response

Chapter 7. The Central American locust: risk and prevention

Chapter 8. Animal hazards—their nature and distribution

Chapter 9. Loss of biodiversity: concerns and threats

Chapter 10. Threats to the sacred groves of Kerala

Chapter 11. Multidrug resistance: a threat to antibiotic era

Chapter 2: Harmful algal blooms

Suzanne McGowan     Department of Aquatic Ecology, Netherlands Institute of Ecology, 6708PB Wageningen, The Netherlands

Abstract

Harmful algal blooms (HABs) in marine, brackish, and fresh-water environments are caused by a variety of microscopic algae and cyanobacteria. HABs are hazardous and sometimes fatal to human and animal populations, either through toxicity, or by creating ecological conditions, such as oxygen depletion, which can kill fish and other economically or ecologically important organisms. HAB hazards have increased globally since the 1970s because of eutrophication, climate change, species translocations, and the interactions of these influences. Human vulnerability to HABs is greatest in communities that are nutritionally and economically reliant on fishery resources, but locally HABs also cause damage to tourist industries and have health-associated costs. There have been major research advances in the monitoring, detection, modeling, forecasting, prevention, communication, and treatment of HAB events, which have helped mitigate health and economic risks. However, reducing HAB incidents in the future will be challenging, due to heavily entrenched socio-ecological systems of food production and land management where nutrient fluxes are likely to increase.

Keywords

Biotoxin; Climate change; Cyanobacteria; Dinoflagellates; Eutrophication; Harmful algal blooms (HABs); Hazard mitigation; PSP

2.1. Introduction

Blooms are dense accumulations of microscopic algal or cyanobacterial cells within marine, brackish, and fresh-water bodies, often resulting in visible discoloration of the water (Heisler et al., 2008; Watson et al., 2015) (Fig. 2.1). Most blooms are caused by planktonic algae that float in the water, but occasionally the term may describe accumulations of microscopic benthic algae or macro algae, which grow attached to surfaces (Berdalet et al., 2017). Phytoplankton blooms in coastal areas may colloquially be referred to as red tides or brown tides. Many algal species bloom as a part of their seasonal periodicity, and some algae produce toxins, which are harmful to humans and other animals. The impacts of algal toxins on humans can be acute in the case of toxic exposure, resulting in death to relatively mild illness, or may potentially arise from long-term chronic exposure (Carmichael et al., 2001; Factor-Litvak et al., 2013). Some algal blooms are linked to the death and illness of livestock, pets, birds, and marine animals through direct toxicity or by causing hostile ecological conditions. Measures to avoid harm from HABs can cause mass disruption to fisheries, water supply, and recreation (Box 2.1). Together, blooms that cause harm to humans or other organisms are termed harmful algal blooms (HABs).

Figure 2.1  Harmful algal blooms (HABs) in freshwater (A, C) and marine (B, D) environments: (A) Cyanobacteria bloom on Esthwaite Water (Cumbria, UK) in September 7, 2007; (B) A bloom of Alexandrium monilatum in Chesapeake Bay near New Point Comfort (USA), September 12, 2016; and (C) Warning sign of cyanobacteria (blue-green algae) blooms close to Malham Tarn, a lake in North Yorkshire, UK; and (D) Shellfish warning sign on Manitou Beach, Washington, USA. (A) Source author's own; (B) Source: W. Vogelbein/VIMS; (C) Source author's own; (D) Source: Razvan Orendovici.

Marine HABs: Of the many thousands of microalgal species, about 300 are involved in harmful events and around 100 produce toxins (Berdalet et al., 2016). In marine environments, most toxic algae are from the phylum of dinoflagellates, while some species of diatoms, prymnesiophytes, and raphidophytes also produce potent toxins (Van Dolah, 2000). The most direct route of marine poisoning to humans is through the ingestion of shellfish or fish, which accumulate HAB toxins, but toxin exposure via aerosols is also common (a). Because many toxins are temperature stable, they are unaffected by cooking. Human symptoms may be classified into the following poisoning syndromes (Table 2.1) (Hinder et al., 2011):

(a) Aerosolized toxin events arise when brevetoxins (g) or palytoxins (e) are released into water and become airborne through wind and sea spray action, leading to irritation and burning of the throat and upper respiratory tract in humans, posing particular risks for people with asthma (Berdalet et al., 2016).

Table 2.1

Box 2.1

The Toledo water crisis.

In August 2014 almost half a million people in Toledo, Ohio were advised not to use water for drinking, cooking or bathing. The source of the problem was a major Microcystis bloom on Lake Erie which tested positive for microcystin toxins. Strong winds may have been responsible for mixing surface blooms into the deeper parts of the lake where water intake pipes for the conurbation were located. This bloom was successfully predicted by the NOAA HAB forecast model. HABs were common on western Lake Erie between the 1960 and 1990s, but have been increasing over the past decade after a lapse of 20 years.

(b) Amnesic shellfish poisoning (ASP) is the only shellfish poisoning caused by diatoms. The genera Pseudo-nitzschia and Nitzschia produce toxic domoic acid which, when ingested via shellfish, can cause gastrointestinal and neurological disturbance, disorientation, lethargy, seizures, permanent loss of short-term memory, and, rarely, death.

(c) Azaspiracid shellfish poisoning (AZP) has similar symptoms to DSP (nausea, vomiting, diarrhea, and stomach cramps), and consequently was misdiagnosed until the toxin azaspiracid (AZA) was identified in 1997 (Twiner et al., 2008). Recovery usually occurs within 2–3 days, and no long-term symptoms have been noted. AZA is produced by the dinoflagellates Azadinium and Amphidoma, and around 20 analogs of the toxin have recently been identified around Europe (Berdalet et al., 2016; Tillmann et al., 2017).

(d) Ciguatera fish poisoning (CFP) is caused by ciguatoxins (CTX), produced by benthic dinoflagellates from the Gambierdiscus genus, which grow attached to coral reefs, and are ingested by fish and invertebrates (Berdalet et al., 2017; Soliño and Costa, 2018). Humans are usually poisoned by eating piscivorous (fish-eating) fish as toxins bioaccumulate up the food chain. CFP symptoms can be persistent and include gastro-intestinal upset followed by neurological problems, muscle aches, headaches, itching, tachycardia, hypertension, blurred vision, paralysis, and, rarely, death. CFP is endemic to sub/tropical areas and is commonly overlooked due to misdiagnosis.

(e) Clupeotoxism is associated with the benthic dinoflagellate Ostreopsis, which produces a strong neurotoxin palytoxin (PTX). The link between PTX and clupeotoxism is not definite, but the syndrome describes seafood poisoning in tropical areas (Berdalet et al., 2017). Severe PTX poisoning causes breakdown of skeletal tissues and can be fatal. Ostreopsis cf. ovata blooms and PTX analogs have recently been associated with respiratory irritation (a) in the Mediterranean (Berdalet et al., 2017).

(f) Diarrhetic shellfish poisoning (DSP) is caused by a group of acidic polyether toxins including okadaic acid (OA) and dinophysistoxin (DTX) analogs produced by dinoflagellates including ten Dinophysis species, two Phalacroma species, and the benthic Prorocentrum lima (Berdalet et al., 2016). Intoxication causes mild gastrointestinal symptoms, which usually subside within 2–3 days.

(g) Neurotoxic shellfish poisoning (NSP) is caused by a suite of brevetoxins deriving most commonly from the dinoflagellate Karenia brevis (Watkins et al., 2008). When consumed in shellfish, human symptoms are nausea, tingling, and numbness around the mouth, loss of motor control, and severe muscular ache. No human fatalities have been recorded, but, because Karenia cells rupture easily, they release toxins into waters, which often cause fish kills and become aerosolized (a).

(h) Paralytic shellfish poisoning (PSP) is caused by saxitoxins (STXs), which are produced predominantly by the dinoflagellates Alexandrium and Pyrodinium. When ingested by humans, the peripheral nervous system is attacked leading to rapid (<1 hour) onset of symptoms including tingling and numbness around the mouth and extremities, loss of motor control, drowsiness, incoherence, and, at high doses, death by respiratory paralysis.

(i) Venerupin shellfish poisoning (VSP) causes gastrointestinal and nervous symptoms, delirium, and liver failure. The liver damage is distinctive in VSP, and the fatality rate is quite high. The dinoflagellate Prorocentrum is thought to carry the toxin venerupin, which is transferred to humans via shellfish (Ferrara, 2020). Uncertainty about the provenance of some VSP incidents exists (Rodríguez et al., 2017).

New toxins, producer organisms, and toxic syndromes continue to be identified (Parsaeimehr et al., 2019). Yessotoxins (YTXs) are produced by the dinoflagellates Lingulodinium polyedrum, Gonyaulax spinifera, and Protoceratium reticulatum (Pitcher et al., 2019), and pectenotoxins (Díaz et al., 2020) were previously classified with DSP toxins because they induce similar symptoms but have now been reclassified (Tubaro et al., 2010). The VSP-associated Prorocentrum minimum also carries the neurotoxin tetrodotoxin (TTX), produced in a symbiotic association with bacteria and widely detected in marine vertebrates and mussels and most notoriously in the Puffer fish (Lagocephalus scleratus) (Rodríguez et al., 2017). Fish and human poisoning incidents previously termed Estuary-associated syndrome are now thought to be caused by a toxic dinoflagellate Karlodinium veneficum, which produces karlotoxins (Peng et al., 2010). Other toxic algae such as the prymnesiophytes (Chrysochromulina and Prymnesium species), which produce the toxin prymnesin (Taylor et al., 2020) and the dinoflagellate Margalefidinium (previously Cochlodinium) polykrikoides are commonly associated with fish kills (Wang et al., 2020).

Freshwater HABs: In freshwater environments including lakes, ponds, reservoirs, and rivers, the prevalent HAB organisms are cyanobacteria, which form cyanoHABs. Sometimes termed blue-green algae, cyanobacteria are old in evolutionary terms and distinct from algae because they have no cell organelles (they are prokaryotes), but they occupy a similar ecological niche. Although more common in freshwater environments, cyanobacteria are also found in marine and brackish waters (Funkey et al., 2014). CyanoHABs can cause deaths and illness in humans and animals when ingested, respiratory issues when inhaled, and are increasingly being implicated as agents of chronic tumor promotion (Gorham et al., 2020). Not all cyanoHABs are toxic, but those that are can threaten drinking water quality, fisheries, and recreational activity. In contrast to marine HAB incidents, most freshwater cyanobacterial blooms occur on a localized scale, associated with individual water bodies. However, airborne transport of cyanoHAB toxins has recently been identified as a transmission pathway beyond the water body (May et al., 2018; Plaas and Paerl, 2020). River transport of cyanoHAB toxins from inland waters to marine areas is another recently discovered toxin exposure threat in marine environments (Anderson et al., 2021). Cyanobacterial toxins are widely produced by cyanobacteria from the orders of Nostocales (Dolichospermum, Anabaena, Nodularia, Aphanizomenon, Cylindrospermopsis, Planktothrix) and Chroococcales (Microcystis and Synechococcus). Toxins may be separated into four classes based on their mode of action:

(a) Hepatotoxins are cyclic peptides, which cause liver hemorrhage (Watson et al., 2015). Characteristic hepatotoxins include microcystins (MCYs) of which there are around 279 chemically similar analogues (present in Microcystis aeruginosa and some Anabaena, Synechococcus, and Planktothrix species) (Bouaïcha et al., 2019) and nodularin (NOD) (present in the brackish water species Nodularia spumigena) (Mashile et al., 2020). Chronic MCY exposure may cause progressive liver injury and cancers (Gorham et al., 2020). Hepatotoxins are easily released from cells and are chemically resilient, facilitating their dispersal and persistence in the environment (Watson et al., 2015).

(b) Cytotoxins affect cellular function but are usually broken down by digestion. However, cylindrospermopsin (CYL; produced by Cylindrospermopsis raciborskii, Aphanizomenon ovalisporum and Umezakia natans) (Shaw et al., 2000) is more stable and can withstand boiling. Exposure results in liver and kidney damage (Watson et al., 2015).

(c) Neurotoxins may cause convulsions, muscle tremors, progressive paralysis, and eventual death from respiratory failure (Mello et al., 2018; Christensen and Khan, 2020). β-N-methylamino-L-alanine (BMAA), anatoxins, saxitoxins, microcystins, and nodularin may all be produced by cyanobacteria and have neurotoxic effects (Mello et al., 2018), with BMAA being particularly widespread among all known cyanobacterial groups (Cox et al., 2018). BMAA has been implicated as the cause of progressive neurodegenerative disease (the Guamanian amyotrophic lateral sclerosis/parkinsonism dementia complex; ALS/PDC) (Cox et al., 2018; Dunlop et al., 2021). PSP-causing STXs have also been found in freshwater cyanobacteria such as Dolichospermum, Cylindrospermopsis, Planktothrix, Lyngbya, and Aphanizomenon (Mello et al., 2018). Anatoxins are found in Oscillatoria, Planktothrix, Microcystis, Aphanizomenon, Cylindrospermum, and Phormidium (Mello et al., 2018). Within the anatoxins, there are three main types: anatoxin-a, its structural analog homoanatoxin-a (low-molecular-weight alkaloids), and anatoxin-a(s) (which is chemically unrelated) (Mello et al., 2018). A new neurotoxin, aetokthonotoxin (AETX) has recently been identified from the cyanobacteria Aetokthonos hydrillicola, which grows on plant surfaces, and is linked to bird deaths (Breinlinger et al., 2021).

(d) Irritants include toxins such as Lyngbyatoxin-a (LTA) and debromoaplysiatoxin (DTA) which are produced by Moorea (previously called Lyngbya). These toxins cause asthma-like symptoms and severe dermatitis, also known as swimmer's itch or seaweed dermatitis in humans (Fristachi et al., 2008; Hill, 2019). Exposure to Trichodesmium species has also been anecdotally linked to dermatitis (called pica in Belize) and asthma-like symptoms in Brazil (called Tamarende fever), but the identity of the toxin remains unclear (O'Neil et al., 2012). Lipopolysaccharides (LPS) are dermatoxic and produced by all cyanobacteria, thus can potentially cause issues at high cell densities (Watson et al., 2015).

New cyanobacterial toxins discoveries are likely. For example, cyanopeptides such as cyanopeptolins and anabaenopeptins are often produced in greater quantities than microcystins, but little is yet known of their toxicological effect (Janssen, 2019). New work on benthic cyanobacterial biofilms suggests that complex suites of toxins are present including CTX-like compounds, PTX, paralyzing toxins, anatoxin-a, and homoanatoxin-a (Berdalet et al., 2016).

2.2. Historic examples of HAB incidents

HABs and toxic incidents have been recorded for hundreds of years and may be an important part of the cultural heritage of waterside communities (Berdalet et al., 2016). Red tides were recorded in Japan during the 8th and 9th century associated with a period of economic growth (Wyatt, 1995). Travel notes published in 1772 observed that blood-colored waters in the sea were more rare in Iceland than in other countries, but noted sporadic bloom occurrences along the Icelandic coasts between 1638 and 1712 (Olaffson and Pálsson, 1805). The deaths of many people were described in Tierra del Fuego, Argentina, in 1886 following ingestion of mussels (Segers, 1908), and cases of suspected PSP were recorded in 1812 in Leith, Scotland (Combe, 1828). Records of freshwater cyanoHABs also extend back over centuries, including 12th century monastery records from Scotland, previously called Monastery of the Green Loch on account of the frequent algal blooms which still occur in its lake (Codd, 1996). Cyanobacterial blooms in Australia have been linked to a previously common outback disease Barcoo Sprue with similar symptoms to cyanobacterial poisoning. European explorers in 1844 described green slime with red below on a pond they were using as a water source, and the sickness that followed its use (Hayman, 1995). The first reference to nuisance algae in New Zealand was a ‘slime event in the 1860s (Hallegraeff et al., 2021). In the United Kingdom, the West Midland Meres are well known for regular cyanobacteria blooms, locally termed the breaking of the meres," as described in Mary Webb's novel Precious Bane in 1924, and confirmed by sedimentary analyses as being present for thousands of years (McGowan et al., 1999). Dinocysts in marine sediment cores around Mexico show that HAB species have been present for at least 100 years (Cuellar-Martinez et al., 2018).

2.3. HAB incidents in recent decades

In recent decades, HABs have expanded geographically and become increasingly common (Gobler et al., 2017; Griffith and Gobler, 2020). While some of this increase may be attributed to better detection capabilities and awareness, sediment cores document an increasing and widespread marine and freshwater HAB prevalence (Edwards et al., 2005; Taranu et al., 2015), including rises in toxin production at some sites (Zastepa et al., 2017). There are at least 60,000 marine intoxication incidents per year with mortality rates estimated at 1.5% towards the end of the last century (Van Dolah, 2000). 20% of all foodborne disease outbreaks in the United States result from the consumption of seafoods, with half of those resulting from naturally occurring algal toxins (Van Dolah, 2000). An estimated 15% of the asthma responses in the world (45 million humans) during 2004 were triggered by brevetoxin and PTX exposure in aerosols from the western boundary current (Walsh et al., 2017). The database HAE-DAT (http://haedat.iode.org/) is attempting to systematize the collection of global data on HAB events but is currently geographically limited to the North Atlantic, North Pacific, and South American oceanic regions with sparse reporting from elsewhere (Table 2.1). In those regions, reports were most common for DSP-, PSP-, and ASP-related toxins and events. NSP events are reported only in the Northwest Atlantic region, involving mostly Karenia events around Florida and North Carolina, with associated aerosolized events. Many HAB poisoning incidents, go unreported or are misdiagnosed, especially mild cases, with CFP underreporting being a known issue (Berdalet et al., 2017). HAE-DAT is focused on marine events, and most likely under-reports cyanoHAB incidents, which are reported elsewhere in the US (Roberts et al., 2020).

HAB incidents vary in their impacts on humans, with potential for major damage to health and socio-economic conditions. PSP is considered the most hazardous marine poisoning syndrome, resulting from a combination of high mortality rate (estimated at a 15% mortality rate across 2000 cases per year) and broad geographic distribution, occurring worldwide in boreal to tropical and coastal to offshore waters (Table 2.2) (Sakamoto et al., 2020; Van Dolah, 2000). TTX poisoning is, however, the most lethal (Nicolas et al., 2017). PSP cases have regularly occurred along the Chinese coast, over the last 3 decades, with a notable incident involving 136 people and one death in Fujian province in 1986 (Sakamoto et al., 2020). The Philippines has probably suffered the most recurrent and sustained losses from PSP, with an individual incident causing 21 deaths in 1983, and the cumulative death toll by 1989 being 100 people with >2000 illnesses (Hallegraeff and Maclean, 1989). Mortality rates in the Philippines have apparently lowered recently with 12 PSP fatalities between 2005 and 18, despite stable bloom frequency and an expansion in the affected bloom areas (Azanza et al., 2019; Yñiguez et al., 2020). In terms of mortality rate, one VSP poisoning event in Japan claims to be the highest with 114 deaths (Grzebyk et al., 1997; Rodríguez et al., 2017). Fatalities are generally more common when toxins and organisms are newly discovered in a region and monitoring procedures are not in place (Trainer et al., 2020). The other poisoning syndromes are rarely fatal, although notable exceptions include three deaths in Eastern Canada in 1987 from ASP, linked to the emergence of a newly discovered poison (domoic acid), and, sometimes, CFP may result in death if there is limited access to medical care. CFP is the most common algal toxin seafood-borne illness affecting around 25,000–50,000 people per year but only an estimated 2%–10% of cases are reported, and only 0.1% of people with CFP consulting a medic in the Caribbean islands (Friedman et al., 2008; Berdalet et al., 2017). DSP was first reported in Japan in the 1970s involving the organism Dinophysis fortii, and DSP-producing organisms are responsible for the most days of aquaculture harvesting closures in northern Japan, Chile, and Europe (Reguera et al., 2014). Aerosolized brevetoxin incidents are frequent in Florida (Gulf of Mexico) and associated with respiratory problems and headaches (Diaz et al., 2019). Respiratory illness from Karenia blooms in New Zealand was first detected in 1992–93, with subsequent incidents in 1998 and 2007 initiating a new public health concern (Chang et al., 2001).

Table 2.2

In freshwaters, lethal intoxication incidents have been mostly related to contaminated drinking water supplies, including the use of water in dialysis equipment in Brazil in 1996 containing microcystins and cylindrospermopsin, which poisoned 166 and killed 60 people (Carmichael et al., 2001) (Table 2.3). An earlier incident in Brazil in 1988 implicated cyanobacterial toxins in the poisoning of 2000 people and 88 deaths through drinking water from a reservoir created by the construction of the Itaparica Dam in Brazil (Teixeira et al., 1993). Although toxin testing was not conducted, high concentrations of Anabaena and Microcystis cells were detected in the untreated water. The Palm Island incident in northern Queensland, Australia, in 1979 was caused by the toxic cyanobacterium Cylindrospermopsis raciborskii leading to the hospitalization of 149 people who had drunk water from a contaminated reservoir (Griffiths and Saker, 2003). Cylindrospermopsin toxins from benthic taxa are also a concern in Australia (Gaget et al., 2017). The OHHABS (One Health Harmful Algal Bloom System) collected reports of 389 people and 413 animals who had been sickened by cyanoHABs between 2016 and 2018 across 18 US states (Roberts et al., 2020). Long-term impacts of cyanobacteria toxin exposure are contentious (Baugh, 2017), but BMAA has been linked to ALS/PDC (Cox et al., 2018), and living near water bodies increase the risk of ALS (Fiore et al., 2020). Epidemiological studies have also made tentative links to cancer (Svirčev et al., 2014). An emerging health threat is from airborne cyanobacterial cells and toxins, which are inhaled providing an alternative exposure route (Walsh et al., 2017).

HABS can cause mass mortality to animals that live in or associated with aquatic environments. Brevetoxins pose a particular risk to marine life because they are released through cell lysis into the water (Brand et al., 2012). Notably, 149 endangered Florida manatees (Trichechus manatus latirostris) were killed in 1996 by Karenia brevis toxins with increases in manatee mortality since that time (Anderson et al., 2021). In central New Zealand, mass mortality of marine life including sea lions occurred during a Karenia brevisulcata bloom in 1988. Brevetoxin poisoning was implicated in fish kills during a raphidophyte (Chattonella cf. verruculosa) bloom in Delaware (Watkins et al., 2008) and in incidents from India, Japan, and Australia (Van Dolah, 2000). In some cases, however, marine mortality occurs through toxin bioaccumulation up the food chain as in the multiple incidents of lethal domoic acid poisonings (ASP) of brown pelicans, cormorants, and sea lions on the Californian coast in the 1990s (Homer and Postel, 1993). Ongoing fish kills from sustained HABs can lead to short-term declines in local fisheries (Landsberg et al., 2009). In the spring of 2015, a Pseudo-nitzschia bloom spanning the length of the central California to British Columbia coasts and nick-named The Blob caused shellfish closures and animal mortalities with 200 rescued seals and sea lions being cared for each day over a 3-month period (Trainer et al., 2020). Recently, Margalefidinium polykrikoides blooms have become more frequent in the Mexican Pacific region, causing massive fish and invertebrate mortalities with impacts on tourism (Sunesen et al., 2021). Prymnesiophytes are regularly associated with fish poisoning episodes, including extensive kills of farmed fish along the Scandinavian coasts in 1988 linked to a 60,000 km²  Chrysochromulina polylepis bloom (Dundas et al., 1989). Prymnesium parvum has been linked with fish kills in inland brackish ecosystems in Finland, Italy, Morocco, Greece, and Israel. In inland waters, cyanoHAB incidents are common when livestock ingest toxic water. They are frequent in Australia (accounting for deaths of 300 sheep, five cattle, and one horse in 1959 at Lake Bonney and for 1600 livestock deaths along the Barwon-Darling River in 1991) and South Africa (between 1993 and 96 dozens of sheep, hundreds of cattle, and several domestic animals died associated with Nodularia and Microcystis bloom incidents). More recently, deaths of 300 elephants in Botswana in 2020 have been tentatively linked with cyanobacterial poisoning from watering holes (Azeem et al., 2020). Similar fatal poisonings of zebra (Equus quagga), wildebeest (Connochaetes taurinus), white rhinoceros (Ceratotherium simum) and impala (Aepyceros melampus) have been reported in Kruger National Park, South Africa, in 2005, 2007, 2008, and 2009 (Bengis et al., 2016). A new ecological cyanoHAB threat was recently uncovered linking cyanobacterially derived neurotoxins to a fatal disease (vacuolar myelinopathy), which has been killing bald eagles in the United States since 1994 (Breinlinger et al., 2021). The benthic cyanobacteria Aetokthonos hydrillicola lives on the leaves of an invasive plant which has colonized the water bodies and the toxin it produces (aetokthonotoxin) is enhanced by bromide, a possible pollutant, indicating how the complex interplay of invasive species and pollutants contributes to eagle deaths.

Table 2.3

HABs, harmful algal blooms

Deoxygenated conditions associated with mass decomposition of algal material are frequently hazardous to marine life, causing so-called dead zones in marine areas, especially semi-enclosed fjords and inland seas. Dead zones have been recorded in >400 systems covering a total area of >245,000 km² including the Baltic, Kattegat, Black Sea, Gulf of Mexico, and East China Sea, which are all major fishery areas (Diaz and Rosenberg, 2008), and coral reefs of the tropics (Altieri et al., 2017). Nontoxic blooms can pose a significant environmental threat when decomposing. Deadly concentrations of hydrogen sulfide gas emitted from thick decomposing strandlines of the seaweed Ulva spp., a nontoxic filamentous chlorophyte macro-alga, on a beach in northern France in 2009, were linked to the death of a horse and serious illness of the rider when stuck in the algal sludge. Previously unexplained deaths of one man and two dogs in this region were each associated with similar blankets of rotting Ulva. A major clean-up operation was launched to remove Ulva spp. bloom from the Yellow Sea in China prior to the Beijing Olympics sailing events in 2008.

2.4. Economic impacts of HABs

Global economic losses due to HABs were estimated to be around $10 billion USD annually in 2014 across marine and freshwater ecosystems (Bernard et al., 2014). Assessments are difficult because records are incomplete and full economic costings should account for associated activities (Stauffer et al., 2019). Marine HABs within the United States cost an estimated $49 million USD per annum in 1987–92 in terms of public health (45%), commercial fishery impacts from fishery closure or damage (37%), recreation and tourism (13%), and monitoring and management costs (4%) (Anderson et al., 2000; Hoagland et al., 2002). This estimate excludes economic multipliers and was influenced by under-reporting of HAB incidents. Since then, US estimates of HABs and hypoxia costs on the restaurant, tourism, and seafood industries were conservatively estimated as $82 million USD annually (Hoagland and Scatasta, 2006). K. brevis blooms in Florida were recently estimated to cost $22 million USD per year in medical expenses and lost work days, and $18 million USD per year in losses to commercial fishing (Stauffer et al., 2019; Anderson et al., 2021). Due its dense population and important role in drinking water provision (11.6 million people), and tourism and fisheries ($7 billion USD) cyanoHABs on western Lake Erie are estimated to have cost $65–71 million USD per year (Stauffer et al., 2019), excluding the costs of the Toledo water crisis (Box 2.1). HAB monitoring and management costs in European countries range from €30,000 to €7 billion per year, $1–8.7 million per year AUD in Australia and $50,000 per quarter NZD in New Zealand (Stauffer et al., 2019). In Canada, health costs arising from HABs are estimated to be $670,000 CAD annually, while impacts to commercial fisheries are $118,000 CAD per year (Stauffer et al., 2019), and in the US respiratory health costs and impacts on quality of life exceeded those of digestive illness (Kouakou and Poder, 2019). More broadly, the impacts of eutrophication in the US (including HABs), cost approximately 2.2 billion USD per year with the greatest losses from the decline in lakeside property values ($0.3–2.8 billion USD per year) and recreational use ($0.37–1.16 billion USD per year), with recovery of threatened and endangered species ($44 million USD) and drinking water costs ($813 million USD) also being significant (Dodds et al., 2008). This study emphasizes the cultural (and therefore economic) importance of inland waters in the US for recreation.

Economic impacts of HABs can be acute where aquaculture is prevalent. China produces more than half of the world's marine and freshwater farmed fish and K. mikimotoi blooms have affected >15,000 km² coastal waters in China for decades, costing >290 M USD in losses in 2012 (Yin et al., 1999; Sakamoto et al., 2020). A notorious Chattonella antiqua bloom in the Seto Sea of Japan cost approx. $71 M USD in 1972 with the loss of 14 million farmed fish and a Margalefidinium polykrikoides or rust tide event in South Korea cost approx. $69.5 M USD in lost aquaculture products in 1995 (Imai et al., 2006; Sakamoto et al., 2020; Griffith and Gobler, 2020). Scandinavian coastal fjords are extensively used for aquaculture (annual value approx. 750 million USD). The 1988 Chrysochromulina blooms killed 500 tonnes of caged fish with a commercial value of $5 million USD along the coast of Norway, and a further 200 sea farms ($200 million USD value) were evacuated during the bloom (Dundas et al., 1989). There has been a long history of HAB damage to the aquaculture industry in Chile, with the recent Godzilla Red Tide resulting in the loss of caged fish worth nearly $800 M (Box 2.2; Trainer et al., 2020). An unexpected and massive PST exceedance (10 mg/kg) of Australian cultured blue mussels discovered in a shipment by Japanese import authorities in 2012 led to a global product recall and loss to the local economy of $23 M AUD (Trainer et al., 2020). The blob event in 2015 is estimated to have cost $48 million to the Dungeness crab industry along the US West Coast (Stauffer et al., 2019; Trainer et al.,