HAB Methodology Documents
https://repository.oceanbestpractices.org/handle/11329/255
2024-03-28T08:47:56ZSolutions for managing cyanobacterial blooms: A scientific summary for policy makers.
https://repository.oceanbestpractices.org/handle/11329/1867
Solutions for managing cyanobacterial blooms: A scientific summary for policy makers.
Burford, M.A.; Gobler, C.J.; Hamilton, D.P.; Visser, P.M.; Lurling, M.; Codd, G.A.
Algae grow wherever there is water; in
oceans, freshwater lakes, rivers, streams and
pools. They underpin aquatic food webs,
providing nutrition for animals in the system,
and along with microbes, are responsible
for cycling energy and nutrients throughout
the environment. Problems arise when algae
bloom, which is often the result of excess
nutrients. These nutrients may come from
a range of sources, including rainfall and
associated runoff from fertilizer application
and land erosion, as well as discharge from
sewage and other high-nutrient sources.
One of the key groups of algae that can bloom
in freshwaters, marine and brackish waters is
cyanobacteria (also known as blue-green algae).
Cyanobacteria are technically not algae, as
they are a more ancient lifeform, but they share
characteristics in common with algae, including
needing sunlight for photosynthesis. They are
particularly prolific in calm waterbodies, such as
lakes, ponds, weirs and reservoirs, or slow flowing
rivers. Cyanobacteria can proliferate in these
environments because longer water residence
times allow many of them to grow and form
blooms. They can also float on the water surface
more readily than other algal groups.
One of the major problems with cyanobacterial
blooms, or cyanoHABs, is that some species
can be toxic. Their toxins (cyanotoxins) can
have diverse health effects on people and
animals, ranging from mild to serious, and
impacts on whole ecosystems. Water intended
for human and animal consumption generally
needs to be treated to remove toxins before
drinking, significantly adding to the cost of
supply. In many countries, testing methods for
cyanotoxins are not available and people may
inadvertently be exposed to these health hazards.
Even when blooms are not toxic, their use of
oxygen at night (= respiration), and bloom
decay can result in low-oxygen conditions
which kill fish and other animals. They can
cause earthy/musty or bad odours via excretory
products and decomposing blooms, e.g.
rotten egg smells, and can wash up on shores
and affect recreational use. They can also
cause severe skin irritation for swimmers.
There is a wide range of within pond/lake system
management and mitigation products, methods
and tools available for controlling cyanoHABs
blooms. However, it is often difficult to determine
which products and approaches may be most
effective for a particular waterbody. This provides
an overview of the products and and physical,
chemical and biological solutions available for
control of cyanoHABs, and some detail on their
benefits and relative costs. It also points to other
publications with more detailed information.
2019-01-01T00:00:00ZGlobalHAB: Evaluating, Reducing and Mitigating the Cost of Harmful Algal Blooms: A Compendium of Case Studies.
https://repository.oceanbestpractices.org/handle/11329/1850
GlobalHAB: Evaluating, Reducing and Mitigating the Cost of Harmful Algal Blooms: A Compendium of Case Studies.
Trainer, Vera L.
Over the last two decades, several efforts have been addressed to compile what is known about the economic impacts of harmful algal blooms (HABs; e.g., Anderson et al., 2000; Hoagland and Scatasta 2006; Huppert and Trainer, 2014; Trainer and Yoshida, 2014; Sanseverino et al., 2016). One study estimated the annual cost of HABs in the European Union at 800 million USD (Hoagland and Scatasta, 2006) but most of that cost was extrapolated from very few HAB organisms. In China, a single Karenia mikimotoi event in 2012 caused up to 330 million USD loss to the mariculture industry, mostly cultivated abalone (Guo et al., 2014). Although past reports have attempted to gather comprehensive economic impact data (e.g., Trainer and Yoshida, 2014), both the type and amount of information were limited, highlighting the need for collaboration between HAB scientists and economists. Furthermore, most countries have neither conducted economic analyses of HABs nor collected data that can be used to generate reliable quantitative estimates of net economic losses and impacts. The lack of data, appropriate and standardized protocols, and the dearth of peer-reviewed studies hamper efforts to quantify the societal costs of regionally frequent, intense, and long-lasting HAB events and to help evaluate the cost of various strategies being developed for HAB prevention, control, and mitigation.
To strategize how specific economic studies can be used to assess the economic impacts of HABs and mitigate their associated risks, a Marine Environmental Quality (MEQ) sponsored Workshop on GlobalHAB: Evaluating, Reducing and Mitigating the Cost of Harmful Algal Blooms: A Compendium of Case Studies was held on October 17–19, 2019, at the Annual Meeting of the North Pacific Marine Science Organization (PICES; Appendices 1 and 2). During this 2.5-day workshop, over 48 international experts on economics, insurance of aquaculture companies, and the science of HABs from Australia, Canada, China, Chile, France, Japan, Korea, Norway, Scotland, Spain, the United Arab Emirates, the UK, and the USA (see list of participants, Appendix 1) discussed a compendium of case
studies that highlighted the economic ramifications of HABs on farmed salmon and shellfish, and on wild-caught, reef-based fisheries.
The workshop included plenary lectures summarizing the state-of-the-art knowledge, ideas and concepts about the economic consequences of HABs worldwide on wild and recreational fisheries and aquaculture, concentrating on five areas of focus:
1. An overview of methods used to evaluate the economic impacts of HABs;
2. Cochlodinium polykrikoides bloom impacts on wild and aquaculture fish kills in Korea;
3. Ciguatera fish poisoning with direct effects on human health and wellbeing;
4. HAB impacts on fish and shellfish aquaculture in the European Union, Canada, and Chile.
5. Impacts of HABs on salmon cage aquaculture.
The HAB-related losses faced by insurers are huge. At the workshop, a representative from a reinsurance company specified that 45% of insurance claims are now related to HABs. In fact, it was stated that the losses due to HABs are larger than any storm that insurers have ever faced. In the Republic of Korea, an insurer recently collapsed due to the frequent and enormous losses of aquacultured fish attributed to HABs.
During the workshop, breakout groups were formed to discuss strategies for mitigation, including the value of information from better or more refined forecasts. Questions addressed included: Can contingency planning reduce loss? How can areas be opened more quickly, how can closures be shorter, and what is the value of information from better forecasts? What is the cost benefit analysis of monitoring programs? How much should be spent on monitoring? For insurance purposes, how can the cost of HABs be reduced?
Several examples of HAB-related losses and mitigation costs were discussed in detail. A HAB incident in northern Norway alone resulted in the loss of 14 thousand tons of Atlantic salmon in May 2019, resulting in a total loss of at least 330 million USD, including insured losses of 45 million USD, underinsured values and deductibles of 40 million USD, losses of future salmon sales of 160 million USD, cleanup costs of 30 to 40 million USD, and loss of taxes and unemployment benefits of 50 million USD. In Brittany, France, the Laboratoire d’Economie et de Management de Nantes-Atlantique (LEMNA), University of Nantes, is conducting a detailed estimation of the impacts of shellfish trade bans caused by HABs. Researchers at LEMNA are creating a database documenting these trade bans from 2004 through 2018 at shellfish harvesting areas in four French departments (Finistère, Morbihan, Loire-Atlantique and Vendée). These four areas encompass about 700 shellfish farms representing 37,600 metric tons of products having an estimated value of €141 million (>156 million USD), i.e., 20% of the national shellfish harvest.
Ciguatera fish poisoning (CFP) deserved special attention at the workshop. This non-bacterial food poisoning, endemic in the South Pacific Islands and the Caribbean Sea, seems to be spreading due to climate change, globalization, and dwindling marine fishes. Poisoning results from the consumption of fish contaminated with Gambierdiscus-produced ciguatoxin. The main challenges to effective CFP detection are the rapid and accurate detection of the causative species and toxins in seafood. CFP has major impacts on human health which are anticipated to increase with climate change (Kidwell, 2015), with acute and chronic diseases and subsequent loss of work hours, and with changes from traditional protein sources to imported products. Appropriate strategies for intervention are urgent but difficult to
Introduction Trainer et al.
PICES Scientific Report No. 59 3
implement. The workshop participants discussed recent studies that are opening new possibilities to address CFP risks in island nations (Trick et al., this report).
The huge HAB-related losses to industry, consumers, and governments illustrate the need for insurers, the aquaculture industry, public health professionals, economists, and HAB scientists to work together to estimate the cost of HAB events relative to the costs of mitigation and management.
There are a number of factors that directly impact the economic stability of both finfish and shellfish aquaculture, of which HABs are only one. Better economic assessment is therefore required to evaluate and prioritize responses to HAB events as appropriate to business need. It is also necessary to determine whether pre-emptive measures currently taken are the most appropriate course of action or whether investment in alternative warning or mitigation approaches is more cost effective. The “halo effects” of HAB impacts are also poorly quantified, including consumer confidence in seafood during and after HAB events. Finally, HAB impacts on aquaculture can be intermittent. While fish and shellfish kills can be massive, they may be years apart, so multi-year economic assessments are needed to better quantify changes in losses and impacts. The future changes on HAB frequency and intensity (Wells et al., 2020, including extreme HAB events (Trainer et al., 2020) cannot be ignored.
Studies of economic and social losses and their impacts need to be planned and teams need to be formed prior to HAB events to ensure that they are comprehensively studied. Toward this goal, the workshop further helped to establish greater connections between economists, industry scientists, and HAB researchers. In this report we provide a series of case studies to help guide future research and management priorities.
2020-01-01T00:00:00ZGuidelines for the study of climate change effects on HABs.
https://repository.oceanbestpractices.org/handle/11329/1823
Guidelines for the study of climate change effects on HABs.
Wells, Mark; Burford, Michele; Kremp, Anke; Montresor, Marina; Pitcher, Grant; Richardson, Anthony; Eriksen, Ruth; Hallegraeff, Gustaaf; Rochester, Wayne; Pitcher, Grant; Burford, Michele; Van de Waal, Dedmer; Bach, Lennart; Berdalet, Elisa; Brandenburg, Karen; Suikkanen, Sanna; Wohlrab, Sylke; Hansen, Per; Hennon, Gwenn; Sefbom, Josefin; Schaum, Elisa; Dyhrman, Sonya; Godhe, Anna; Zingone, Adriana; Escalera, Laura; Bresnan, Elieen; Enevoldsen, Henrik; Provoost, Pieter; Richardson, Anthony; Hamilton, David; Anderson, Clarissa; Hense, Inga; Chapra, Steven
Our planet Earth is changing. Marine and freshwater ecosystems are experiencing intense natural and anthropogenic pressures that will generate unforeseen changes in their structure and functioning. The drivers of climate change have already altered the dynamics and interactions of the biotic and abiotic components in these ecosystems, and these changes are anticipated to accelerate in the future. Embedded within natural aquatic ecosystems are Harmful Algal Blooms (HABs) that are noxious to aquatic organisms as well as human health and wellbeing.The major aim of these guidelines is to communicate standardized strategies, tools, and protocols to assist researchers studying how climate change drivers may increase or decrease future HAB prevalence in aquatic ecosystems.
2021-01-01T00:00:00ZAppendix 4. Preservatives and methods for algal cell enumeration.
https://repository.oceanbestpractices.org/handle/11329/809
Appendix 4. Preservatives and methods for algal cell enumeration.
Anderson, Donald M.; Karlson, Bengt
There are multiple ways to preserve phytoplankton samples and determine the algal species
composition and abundance. This Appendix provides details on some of the most common
methods. Additional relevant publications are included in Section 5, References. One of the
most useful is Karlson et al. (2010), which can be downloaded at http://hab.iocunesco.
org/index.php?option=com_oe&task=viewDocumentRecord&docID=5440.
2017-01-01T00:00:00ZAppendix 3. Methods for measuring transparent exopolymer particles and their precursors in seawater.
https://repository.oceanbestpractices.org/handle/11329/808
Appendix 3. Methods for measuring transparent exopolymer particles and their precursors in seawater.
Villacorte, Loreen O.; Schippers, Jan C.; Kennedy, Maria D.
Transparent exopolymer particles (TEP) and their precursors produced by phyto-/bacterioplankton
in fresh and marine aquatic environments are increasingly considered as a major
cause of organic/particulate fouling in MF/UF membranes and organic/particulate and
biological fouling in SWRO membranes. The following sections comprise detailed
descriptions of two methods for measuring transparent exopolymer particles in seawater,
namely TEP0.4μm and TEP10kDa. The TEP0.4μm method measures transparent exopolymer
particles retained by membrane filters having pores of 0.4 μm and conventionally known as
TEP (Passow and Alldredge, 1995). The TEP10kDa method covers transparent exopolymer
particles retained by membrane filters with molecular weight cut-off of 10 kDa.
Consequently, this method covers both TEP and most (if not all) of their colloidal precursors.
TEP0.4μm is a more rapid method than TEP10kDa and is recommended for routine TEP
monitoring in untreated seawater. The TEP10kDa method is more time consuming, however, it
gives much more information because it covers both TEP and their colloidal precursors.
2017-01-01T00:00:00ZAppendix 2. Rapid screening methods for Harmful Algal Blooms toxins.
https://repository.oceanbestpractices.org/handle/11329/807
Appendix 2. Rapid screening methods for Harmful Algal Blooms toxins.
Anderson, Donald M.; Laycock, Maurice; Rubio, Fernando
At the core of all national harmful algal bloom (HAB) programs are the monitoring
programs needed to detect HAB toxins in shellfish, fish, water, or other resources
sufficiently early to take management actions (Anderson et al. 2001). These programs
measure toxins produced by multiple species of algae, with the methods used varying
dramatically in scope and complexity due to the types of toxins that need to be detected, the
nature of the affected resource, and regulatory requirements.
Some of the methods developed for analysis of shellfish tissues and algal blooms can be of
direct use in desalination plants for analysis of toxins in water – both the raw, untreated
water before desalination, and the treated, fresh water. A major concern, however, are the
detection limits of the assays. All analytical methods have limits of detection (LODs) and
the choice of a method should be consistent with potential bloom concentrations and possible toxin levels. With desalination plants, toxins need to be measured at exceedingly
low levels in water, whereas shellfish concentrate toxins to much higher levels. A recent
study summarized the epidemiological data for four common algal toxins (Laycock et al.
2010) and estimated the potential contamination of water that might enter a desalination
plant during major blooms. The assessment was based on a hypothetical (and dense) bloom
of toxic algae consisting of 10 7 cells/L with a toxin cell quota of 40 pg toxin/cell. If all of
that toxin were released from the cells into the water, that would give a concentration in seawater of 400 μg/L. An alternative approach to estimating the total amount of toxin
present in a bloom is given in Chapter 1 (Table 1.4), where the amounts of toxin contained
in hypothetical blooms of various common HAB species are presented. The values range
from a few hundred to 1,000 μg/L. Given that 99% or more of a toxin is likely to be
removed by thermal or reverse osmosis desalination (Chapter 10), the sensitivity of an
analytical method must therefore be at least 0.1 – 1.0 μg/L or 0.1 – 1.0 ng/mL. Therefore,
analysis of water samples for dissolved or particulate toxins (i.e., inside algal cells) will
require high sensitivity methods, such as enzyme-linked immunosorbent assays (ELISAs).
For example, the LOD for saxitoxin (STX) using the Abraxis STX ELISA kit is 0.02 ng/mL
and there is similar sensitivity for domoic acid.
This appendix presents details on simple screening methods for HAB toxins. More complex
analytical methods are described or cited in Chapter 2. The screening methods are presented
here as a guide to desalination plant staff who wish to conduct on-site analyses. These
analyses could be of raw intake water, treated water, or algal cell extracts from monitoring
programs (Chapter 3).
The example assays are restricted to four HAB toxins i.e., saxitoxins, domoic acid,
microcystins/nodularins, and anatoxin-a. Although sample preparation procedures may
differ for the other HAB toxins not include here, the commercial ELISA kit protocols are
similar to each other. Sample preparation procedures, however, vary depending on solubility
of the toxins, source (e.g., phytoplankton, shellfish, or cyanobacteria) and method of
analysis. Sample preparation methods will be described in detail, as will procedures used to
obtain samples. Methods of analysis other than ELISA are also presented.
Lateral flow tests (such as the Scotia tests) are described as simpler alternatives to the
ELISA kits. The advantages and disadvantages of both tests will be discussed.
2017-01-01T00:00:00ZAppendix 1. Algal species potentially harmful to desalinitation operations.
https://repository.oceanbestpractices.org/handle/11329/806
Appendix 1. Algal species potentially harmful to desalinitation operations.
Borkman, David G.; Anderson, Donald M.
It is now well established that harmful algal blooms (HABs) represent a serious and growing
threat to seawater reverse osmosis (SWRO) desalination plants worldwide. In many plants,
these threats are indirectly monitored using parameters such as the Silt Density Index (SDI)
or chlorophyll-a (see Chapter 5), but these only provide a general indication of the particulate
fouling propensity of the water or the abundance of phytoplankton, respectively. Although it
is often a challenge to obtain data on the phytoplankton species composition and abundance
in the raw seawater, such information can be of great value in the long-term operation of
desalination plants. Individual algal species vary dramatically in their properties and
therefore in the extent to which they can disrupt plant operations (e. g., through the
production of toxins that represent a potential threat to the safety of the drinking water
produced, or organic matter that can clog filters and foul membranes). As a result, it is
important for a desalination plant to make (and record) species identifications, and the
concentrations of those species that are in the source seawater, particularly those that have
disrupted normal plant operations. As described in Chapter 3, monitoring programs for
seawater outside a plant and process monitoring at the plant can provide this type of
information.
Identification of the algal species in seawater samples can be a challenge however. In Chapter
3, methods for sample collection, fixation, and identification are presented. Section 3.6.1.1
lists books that provide useful taxonomic information on marine HAB species, while section
3.6.1.2 lists websites where taxonomic information on algal species can be found. To
augment this information and to provide a quick resource for operators or managers who
need identification assistance, this appendix presents brief descriptions and a photograph of
some algal species that either have caused problems at desalination plants, that produce
potent toxins, or that are known to produce sufficient organic matter or biomass to be
problematic. The list of species covered here is not comprehensive, as this is not intended to
be an operator’s sole source of taxonomic information. Instead, it is offered as a quick
reference guide. For example, there are more than 30 species in the Alexandrium genus, and
about half of those are toxic, but only three are described here. Readers are urged to refer to
the many other resources that provide more detailed descriptions and photographs.
In this manual, we define toxic algae as those that produce potent toxins (i.e., poisonous
substances produced within living cells or organisms), e.g., saxitoxin. These can cause
illness or mortality in humans as well as marine life through either direct exposure to the toxin or ingestion of bioaccumulated toxin in higher trophic levels e.g. shellfish. Confusion
arises, however, because non-toxic HABs can also result in mass mortalities of fish and other
marine life. In this instance, the mortality results from the indirect effect of compounds
produced by the algae - compounds that do not have specific targets or receptors, but instead
are more general in their mechanism of damage, sometimes requiring chemical modifications
by other compounds to become lethal. Examples of “harmful” but not “toxic” substances are
reactive oxygen species that, when combined with polyunsaturated fatty acids, can rapidly kill fish and other animals. Another example is a proteinaceous compound produced by
Akashiwo sanguinea that accumulates on bird feathers, causing a loss in natural water
repellency and widespread mortality of affected animals.
In this appendix, species that do not produce toxins but that do cause marine mortalities are
termed “harmful”.
2017-01-01T00:00:00ZCase histories for Harmful Algal Blooms in desalination.
https://repository.oceanbestpractices.org/handle/11329/759
Case histories for Harmful Algal Blooms in desalination.
Boerlage, Siobhan F.E.; Dixon, Mike B.; Anderson, Donald M.
Algae have long been an issue impacting desalination plant operation in areas prone to algal
blooms or where macroalgae (seaweeds) and detritus became dislodged from the seabed.
Previously and still today, operators and designers may elect to turn down production or shut
down SWRO plants, if contract obligations allow, when blooms are infrequent or of short
duration. Alternatively, in areas subject to frequent and prolonged blooms, additional
pretreatment such as conventional dissolved air flotation (DAF), hitherto designed for
brackish water applications, began to be employed as early as 1995.
The unprecedented 2008/2009 bloom of Cochlodinium polykrikoides in the Gulf of Oman
and the Gulf1, brought algal blooms to the fore in the desalination industry. SWRO plant
shutdowns were up to four months long as pretreatment processes struggled to remove the
increased biomass and produce the required RO feedwater quality. Apart from a few
exceptions, thermal desalination plants continued to operate without major issue throughout
the bloom, as phytoplankton blooms generally pass through intake screens and thermal
processes are very forgiving of source water quality. This was demonstrated at the Fujairah 1
hybrid desalination plant where the multi-stage flash (MSF) plant operated throughout the
bloom while the adjacent SWRO plant was shut down. Globally, harmful algal blooms (HABs) similar to the 2008 bloom of Cochlodinium
polykrikoides are increasing in frequency and severity (Anderson et al. 2012). Coupled with
the increasing use of RO as the desalination technology of choice, HABs have become one of
the major challenges facing the industry as RO membranes are extremely vulnerable to
feedwater quality, making pre-treatment exceptionally important. Smooth operation is
contingent on the selection of appropriate pretreatment processes upstream to remove
organics, solids, colloids and other foulants from the RO feedwater. The 2008 Gulf HAB
highlighted the limitations of conventional pretreatment based on ferric chloride coagulation
and single stage dual media filtration (DMF) in removing algal biomass and organics.
Ongoing research efforts to identify the algal organic matter (AOM) constituents responsible
for membrane fouling and measurement of their removal in pretreatment intensified. To this
end, the spike in AOM occurring during a bloom was found to comprise mainly of high
molecular weight biopolymers (polysaccharides and proteins), which include sticky
transparent exopolymer particles (TEP) (Myklestad 1995; Villacorte 2014). TEP have been
shown to form microgels with a high hydraulic resistance and are increasingly recognized to
promote biofouling of RO membranes (Villacorte 2014; Berman and Holenberg 2005; Li et
al. 2015). With the increasing adoption of low pressure microfiltration (MF) and
ultrafiltration (UF) membrane pretreatment, questions were raised as to their performance
during algal bloom events and how they compared to conventional pretreatment in removal of AOM.
In preparing the Manual and to address some of the above questions, operators, researchers,
and plant owners in the desalination industry were contacted as part of an informal survey
and invited to contribute
case studies related to their
experience with algal
blooms. As expected, it
became clear that algal
bloom issues were
predominantly encountered
in SWRO plants rather than
those using thermal
desalination. Twelve SWRO
plants (Figure 11.1.1) at
eleven different sites were in
a position to share their
experiences from a shortlist
of 30 sites that may have
experienced HAB issues.
Algal blooms, primarily phytoplankton, were reported in almost all geographic locations, in
cold and warm seas over a range of salinities affecting municipal and industrial desalination
plants. Notable areas affected include the warmer waters of the Gulf of Oman and the Gulf in
the Middle East. Case studies include Sohar and Barka 1 in Oman, Fujairah 2 in UAE and the
Shuwaikh plant located close to Kuwait’s most important commercial port in the upper
reaches of the Gulf where seawater quality is at its poorest. HABs are also commonly found
in the cooler waters off the coast of Antofagasta in Northern Chile supplying industry and drinking water for towns in one of the driest areas of the world.
Key insights from the 12 case studies are summarized below in terms of impacts experienced,
if any, in both conventional and advanced MF/UF membrane pretreatment plants during algal
blooms. Commonly recommended measures implemented in the industry to combat algal blooms are discussed in relation to the case studies mitigation strategies, and lessons learned.
This encompasses measures adopted during design and/or during plant operation, e.g. deepwater
intakes (Gold Coast), and DAF (Fujairah 2, Shuwaikh) and/or direct MF/UF filtration
(Jacobahaven, Sohar), or subsequently enacted in response to HAB events (La Chimba).
2017-01-01T00:00:00ZRemoval of algal toxins and taste and odor compounds during desalination.
https://repository.oceanbestpractices.org/handle/11329/758
Removal of algal toxins and taste and odor compounds during desalination.
Dixon, Mike B.; Boerlage, Siobhan F.E.; Churman, Holly; Henthorne, Lisa; Anderson, Donald M.
A major challenge in desalination is the removal of harmful algal bloom (HAB) toxins and
taste and odor compounds (hereafter referred to as algal metabolites) using common
treatment techniques. Removal of other compounds such as polysaccharides, proteins or
transparent exopolymer particles (TEP) are discussed in Chapter 2. Taste and odor
compounds are materials produced during a HAB that are not detrimental to human health,
but cause customer dissatisfaction and often a misconception that the drinking water is not
suitable for consumption. Toxins are detrimental to human health and are discussed in
Chapter 2. Here the objective is to assess each process unit in a common desalination
treatment train, both for SWRO and thermal desalination, and address how each is best
optimized to act as a barrier to these specific algal metabolites. Where treatment techniques
in seawater applications exist, these have been referenced and used as examples. As little
documentation exists on removal of algal metabolites from seawater blooms, fresh water
algal species are referred to whenever needed. This information is relevant in understanding
the removal mechanisms that are possible. For clarity, these are denoted for each example.
Algal metabolites can be either intracellular or extracellular. Many algal species have high
percentages of intracellular metabolites, such as Microcystis (freshwater) in which the toxin
microcystin can be up to 98% intracellular (Chow et al. 1997). Lefebvre et al. (2008) showed
an approximate 81% intracellular saxitoxin (STX)-equivalent concentration for an
Alexandrium (seawater) bloom, although further data are needed to confirm this observation.
STX-eq (or STX-equivalents) is a measure of total toxicity due to all saxitoxin analogues in a
particular solution. In contrast, Smith et al. (2012) report that 60% of the okadaic acid
produced by Dinophysis cultures was extracellular, while Kudela (pers. comm.) reported total
and extracellular concentrations of 100 and 50 μg/L domoic acid respectively during a massive bloom of Pseudo-nitzschia along the US west coast in 2014. Extracellular metabolites are inefficiently removed by pretreatment processes, and this is discussed below
in more detail.
The nutritional status of HAB cells will affect the percentage of extracellular metabolites in a
bloom. At the outset of a bloom, HAB cells will be more robust than toward the end of the
bloom period when stresses from nutrient limitation, grazing, or other factors can lead to the
leakage of metabolites into the seawater. Smith et al. (2012) noted that, in general, the
concentration of extracellular toxin in a lab culture of Dinophysis acuminata (seawater)
significantly increased upon culture aging and decline; cells did not appear to be actively or
passively releasing toxin during the stationary phase (see Chapter 1, Figure 1.3), but rather
extracellular release was likely a result of cell death.
2017-01-01T00:00:00ZAlgal biomass pretreatment in Seawater Reverse Osmosis.
https://repository.oceanbestpractices.org/handle/11329/757
Algal biomass pretreatment in Seawater Reverse Osmosis.
Dixon, Mike B.; Boerlage, Siobhan F.E.; Voutchkov, Nikolay; Henderson, Rita; Wilf, Mark; Zhu, Ivan; Assiyeh Alizadeh Tabatabai, S.; Amato, Tony; Resosudarmo, Adhikara; Pearce, Graeme K.; Kennedy, Maria; Schippers, Jan C.; Winters, Harvey
Harmful algal blooms (HABs) can result in a substantial increase in the organic and solids
load in the seawater feed to be treated at a desalination plant. In this chapter, the removal of
this material is addressed in the context of the multi-barrier treatment process for seawater
reverse osmosis (SWRO) as presented in Chapter 8 on risk management for HAB events.
While this chapter covers removal of non-toxic material, Chapter 10 builds upon these
principles and discusses the mechanisms and effectiveness for each barrier with respect to
toxin removal. This chapter covers only the main barriers used in the SWRO desalination
plants for HAB bloom risk mitigation, though the authors acknowledge that other niche
treatment barriers exist in SWRO systems. The treatment processes discussed here are
chlorination and dechlorination, dissolved air flotation (DAF), granular media filtration
(GMF), microscreens for microfiltration/ultrafiltration (MF/UF), MF/UF itself, cartridge
filtration and SWRO. Coagulation is discussed in general terms and then more specifically
for DAF, GMF, and MF/UF pretreatments. Each treatment process is broken down into a
discussion of how the process works and then how HAB cells affect the process operation.
Importantly, the chapter deals with how upstream actions can detrimentally affect
downstream treatment processes with respect to algal blooms.
In particular, this chapter discusses removal mechanisms for algal organic matter (AOM) and
how operational actions can prevent detrimental effects of AOM. As discussed in Chapter 2,
the chemical composition of AOM usually includes proteins, polysaccharides, nucleic acids,
lipids, and other dissolved organic substances. AOM compounds typically cover a wide size spectrum, ranging from less than 1 nm to more than 1 mm. Based on their size cut-off, GMF
and MF/UF are expected to remove only part of high molecular weight AOM (as shown in
Chapter 2, Figure 2.2). SWRO is expected to achieve complete removal of AOM, but will
suffer from fouling issues if AOM is not removed upstream
2017-01-01T00:00:00Z