NEW: Scientific Summary for Policy Makers on Harmful Algal Blooms

New publication on Harmful Algal Blooms for policy makers

© ESA Satellite photo of a phytoplankton bloom near Ireland.

Harmful Algal Blooms (HABs) occur in nearly all aquatic environments and can cause harm to aquatic ecosystems, including plants and animals, and to humans via direct exposure to water-borne toxins or by toxic seafood consumption. The severity and frequency of some types of HABs is increasing. In order to address this worldwide phenomenon, research, monitoring, and management must be closely integrated with policy decisions that affect our global ocean. With this in mind, a new Scientific Summary for Policymakers on Harmful Algal Blooms was launched during the 28th session of the Intergovernmental Oceanographic Commission’s Assembly at UNESCO headquarters on 17 June 2015.


Many natural and anthropogenic factors regulate the occurrence, frequency and impact of algal events, ranging from local eutrophication, changes in climate and increased exploitation of coastal areas. The Summary considers the causes, impacts and mitigation options, including management issues associated with harmful algal events and their impacts on ecosystems and society. This overview of the current scientific understanding of harmful algal blooms and mitigation options will assist non-specialist and decisions makers in planning monitoring and management of harmful algal events to address environmental, socio-economic and health impacts.

It was prepared by the Global Ecology and Oceanography of Harmful Algal Blooms research programme (GEOHAB), a joint project of the Scientific Committee on Oceanic Research (SCOR) and the Intergovernmental Oceanographic Commission (IOC) of UNESCO, and benefited from the contributions of experts all over the world.

the Scientific Summary is freely availableonline(pdf). For printed copies, please contact:

Related links:

Conference: Harmful Algal Blooms and Desalination


Harmful Algal Blooms
and Desalination


April 16-17, 2014

Muscat, Oman

       Download PDF-flyer                                                

In many arid regions, countries are increasingly reliant on seawater desalination to supply drinking water for rapidly growing coastal populations. There are currently more than 14, 000 desalination plants in more than 150 countries worldwide.

An   emerging threat to the desalination industry is from harmful algal   blooms (HABs, commonly called red tides). High biomass HABs can restrict    fl ow in desalination plants by clogging fi lters, but other impacts   include fouling of surfaces due to dissolved organic materials that can  also compromise  the integrity of reverse osmosis (RO) membranes. A   recent HAB of the  dinofl agellate Cochlodinium is a clear  example of the risk posed by  these phenomena. That outbreak, which  lasted nearly eight months in the  Gulf-Arabian Sea region in 2008/2009,   closed or restricted the operation  of multiple desalination plants,  one for as long as 55 days. With  little reserve water storage or  alternative sources, this was a major threat to the region.

Recognition   of potential problems that HABs may pose to desalination is  new and  has, so far, largely been speculative. Toxic blooms in the  vicinity of desalination plants are often unrecognized events, and plant  operators   are generally unaware of the threat that algal toxins pose. As a result,   no measurements of marine algal toxins before and after desalination   have been made at any large-scale desalination plant.

This   two-day conference will bring together scientists, engineers,  managers,  and government offi cials. The date for this meeting will be April  16-17, immediately following the Sultan Qaboos University  International  Conference on Desalination, Environment, and Outfall Systems, to be  held in Muscat  April 13-15. At the HAB conference, presentations by  scientists and  engineers will cover topics that include the following;

  1. A general overview of HABs, their impacts, and trends
  3. Case studies and descriptions of impacts of HABs on desalination facilities
  5. Results of experimental and pilot studies on HAB toxin removal during desalination
  7. Results of experimental studies on the removal of HAB biomass using Dissolved Air Flotation (DAF), ultrafiltration, and other methods
  9. Design considerations for desalination plants in areas subject to recurrent HABs
  11. Approaches to direct bloom control or suppression
  13. Action plans or management strategies to follow during HAB outbreaks
  15. Regulatory issues
  17. Research priorities and future plans.

Contributed papers: Abstracts will be solicited in the next announcement. We anticipate a closing date of mid-January 2014. Oral presentations and posters will be welcome.


Under the Patronage of HE Mohammed Al Mahrouqi Chairman of the PAEW, Oman







IPHAB recommended proceedures for automated and semi-automated HAB-monitoring and forecasting

A Task Team under the IOC Intergovernmental Panel on Harmful Algal Blooms (IPHAB) has published its recommendations for HAB-monitoring. Download the Recommendations here.  

From the scientic literature:

Harmful algal blooms and climate change: Learning from the past and present to forecast the future. Mark L. Wells a,*, Vera L. Trainer b, Theodore J. Smayda c, Bengt S.O. Karlson d,Charles G. Trick e, Raphael M. Kudela f, Akira Ishikawa g, Stewart Bernard h, Angela Wulff i,
Donald M. Anderson j, William P. Cochlan k. Harmful Algae 49 (2015) 68–93.

Climate change pressures will influence marine planktonic systems globally, and it is conceivable that
harmful algal blooms may increase in frequency and severity. These pressures will be manifest as
alterations in temperature, stratification, light, ocean acidification, precipitation-induced nutrient
inputs, and grazing, but absence of fundamental knowledge of the mechanisms driving harmful algal
blooms frustrates most hope of forecasting their future prevalence. Summarized here is the consensus of
a recent workshop held to address what currently is known and not known about the environmental
conditions that favor initiation and maintenance of harmful algal blooms. There is expectation that
harmful algal bloom (HAB) geographical domains should expand in some cases, as will seasonal
windows of opportunity for harmful algal blooms at higher latitudes. Nonetheless there is only basic
information to speculate upon which regions or habitats HAB species may be the most resilient or
susceptible. Moreover, current research strategies are not well suited to inform these fundamental
linkages. There is a critical absence of tenable hypotheses for how climate pressures mechanistically
affect HAB species, and the lack of uniform experimental protocols limits the quantitative crossinvestigation
comparisons essential to advancement. A HAB ‘‘best practices’’ manual would help foster
more uniform research strategies and protocols, and selection of a small target list of model HAB species
or isolates for study would greatly promote the accumulation of knowledge. Despite the need to focus on
keystone species, more studies need to address strain variability within species, their responses under
multifactorial conditions, and the retrospective analyses of long-term plankton and cyst core data;
research topics that are departures from the norm. Examples of some fundamental unknowns include
how larger and more frequent extreme weather events may break down natural biogeographic barriers,
how stratification may enhance or diminish HAB events, how trace nutrients (metals, vitamins)
influence cell toxicity, and how grazing pressures may leverage, or mitigate HAB development. There is
an absence of high quality time-series data in most regions currently experiencing HAB outbreaks, and
little if any data from regions expected to develop HAB events in the future. A subset of observer sites is
recommended to help develop stronger linkages among global, national, and regional climate change
* Corresponding author. Tel.: +1 207 581 4322. E-mail addresses: This email address is being protected from spambots. You need JavaScript enabled to view it. (M.L. Wells), This email address is being protected from spambots. You need JavaScript enabled to view it. (V.L. Trainer), This email address is being protected from spambots. You need JavaScript enabled to view it. (T.J. Smayda), This email address is being protected from spambots. You need JavaScript enabled to view it. (Bengt S.O. Karlson), This email address is being protected from spambots. You need JavaScript enabled to view it. (C.G. Trick), This email address is being protected from spambots. You need JavaScript enabled to view it. (R.M. Kudela), This email address is being protected from spambots. You need JavaScript enabled to view it. (A. Ishikawa), This email address is being protected from spambots. You need JavaScript enabled to view it. (S. Bernard), This email address is being protected from spambots. You need JavaScript enabled to view it. (A. Wulff), This email address is being protected from spambots. You need JavaScript enabled to view it. (D.M. Anderson), This email address is being protected from spambots. You need JavaScript enabled to view it. (W.P. Cochlan).

REVIEW: OCEAN CLIMATE CHANGE, PHYTOPLANKTON COMMUNITY RESPONSES, AND HARMFUL ALGAL BLOOMS: A FORMIDABLE PREDICTIVE CHALLENGE, by Gustaaf M. Hallegraeff, Institute of Marine and Antarctic Studies, and School of Plant Science, University of Tasmania, Private Bag 55, Hobart,Tasmania 7001, Australia.  J. Phycol. 46, 220–235 (2010), 2010 Phycological Society of America, DOI: 10.1111/j.1529-8817.2010.00815.x

Prediction of the impact of global climate change on marine HABs is fraught with difficulties. However, we can learn important lessons from the fossil record of dinoflagellate cysts; long-term monitoring programs, such as the Continuous Plankton Recorder surveys; and short-term phytoplankton community responses to El Nino Southern Oscillation (ENSO) and North Atlantic Oscillation (NAO) episodes.Increasing temperature, enhanced surface stratification, alteration of ocean currents, intensification or weakening of local nutrient upwelling, stimulation of photosynthesis by elevated CO2, reduced calcification through ocean acidification (‘‘the other CO2 problem’’), and heavy precipitation and storm events causing changes in land runoff and micronutrient availability may all produce contradictory species- or even strain-specific responses. Complex factor interactions exist, and simulated ecophysiological laboratory experiments rarely allow for sufficient acclimation and rarely take into account physiological plasticity and genetic strain diversity. We can expect: (i) range expansion of warm-water species at the expense of cold-water species, which are driven poleward; (ii) speciesspecific changes in the abundance and seasonal window of growth of HAB taxa; (iii) earlier timing of peak production of some phytoplankton; and (iv) secondary effects for marine food webs, notably when individual zooplankton and fish grazers are differentially impacted (‘‘match-mismatch’’) by climate change. Some species of harmful algae (e.g., toxic dinoflagellates benefitting from land runoff and ⁄ or water column stratification, tropical benthic dinoflagellates responding to increased water temperatures and coral reef disturbance) may become more successful,while others may diminish in areas currently impacted. Our limited understanding of marine ecosystem responses to multifactorial physicochemical climate drivers as well as our poor knowledge of the potential of marine microalgae to adapt genetically and phenotypically to the unprecedented pace of current climate change are emphasized. The greatest problems for human society will be caused by being unprepared for significant range expansions or the increase of algal biotoxin problems in currently

poorly monitored areas, thus calling for increased vigilance in seafood-biotoxin and HAB monitoring programs. Changes in phytoplankton communities provide a sensitive early warning for climate-driven perturbations to marine ecosystems.



The GEOHAB Scientific Steering Committee has developed an Advisory Bulletin to provide sound scientific and technical advice to decision-makers in relation to proposals to add urea to the sea in order to stimulate algal blooms and sequester carbon for commercial purposes.

Download at IOC and SCOR communicated the Advisory Bulletin to the IMO London Convention Scientific Group on Ocean Fertilization. See also a 57-author view point paper in the Marine Pollution Bulletin: Gilbert et al., 2008. Ocean urea fertilization for carbon credits poses high ecological risks. Marine Pollution Bulletin, doi·:10.1016/j.marpolbul.2008.03.010).


1. A new manual on microscopic and molecular methods for quantitative phytoplankton analysis is available from the IOC in cooperation with ICES. The manual includes illustrated step by step instructions on how to carry out the methods. The manual can be downloaded as a pdf-file here.

Intergovernmental Oceanographic Commission of ©UNESCO. 2010. Karlson, B., Cusack, C. and Bresnan, E. (editors). Microscopic and molecular methods for quantitative phytoplankton analysis. Paris, UNESCO. (IOC Manuals and Guides, no. 55.) (IOC/2010/MG/55), 110 pages. (English only)

2. Real-time Coastal Observing Systems for Marine Ecosystem Dynamics and Harmful Algal Blooms: Theory, Instrumentation and Modeling. Edited by Marcel Babin, Collin Roesler and John Cullen. Download order form here

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