Blooms of autotrophic algae and some heterotrophic protists are increasingly frequent in coastal waters around the world and are collectively grouped as harmful algal blooms (HABs). Blooms of these organisms are attributed to two primary factors: natural processes such as circulation, upwelling relaxation, and river flow; and, anthropogenic loadings leading to eutrophication. Unfortunately, the latter is commonly assumed to be the primary cause of all blooms, which is not the case in many instances. Moreover, although it is generally acknowledged that occurrences of these phenomena are increasing throughout the world's oceans, the reasons for this apparent increase remain debated and include not only eutrophication but increased observation efforts in coastal zones of the world. There is a rapidly advancing monitoring effort resulting from the perception of increased impacts from these HABs, manifested as expanding routine coastal monitoring programs, rapid development and deployment of new detection methods for individual species, toxins, and toxicities, and expansion of coastal modeling activities towards observational forecasts of bloom landfall and eventually bloom prediction. Together, these many efforts will provide resource managers with the tools needed to develop effective strategies for the management and mitigation of HABs and their frequently devastating impacts on the coastal environment.

Harmful algal blooms: causes, impacts and detection

After the successful Coastal Zone Color Scanner (CZCS, 1978-1986), demonstration that quantitative estimations of geophysical variables such as chlorophyll a and diffuse attenuation coefficient could be derived from top of the atmosphere radiances, a number of international missions with ocean color capabilities were launched beginning in the late 1990s. Most notable were those with global data acquisition capabilities, i.e., the Ocean Color and Temperature Sensor (OCTS 1996-1997), the Sea-viewing Wide Field-of-view Sensor (SeaWiFS, United States, 1997-present), two Moderate Resolution Imaging Spectroradiometers, (MODIS, United States, Terra/2000-present and Aqua/2002-present), the Global Imager (GLI, Japan, 2002-2003), and the Medium Resolution Imaging Spectrometer (MERIS, European Space Agency, 2002-present). These missions have provided data of exceptional quality and continuity, allowing for scientific inquiries into a wide variety of marine research topics not possible with the CZCS. This review focuses on the scientific advances made over the past decade using these data sets.

https://ebme.marine.rutgers.edu/papers/Papers/Annual%20Review_McClain_2009.pdf

A Decade of Satellite Ocean Color Observations

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

The algal blooming in the inland lakes has become a critically important issue for its impacts not only on local natural and social environments, but also on global human community. However, the occurrences of blooming on larger spatial scale and longer time scale have rarely been studied. As the third largest freshwater lake in China, Lake Taihu has drawn increasing attention from both public and scientific communities concerning its degradation. Using available satellite images, we reconstructed the spatial and temporal patterns of algal blooms in Lake Taihu through the pasttwo decades. The blooming characteristics over the past two decades were examined with the dynamic of initial blooming date being highlighted. The initial blooming dates were gradually becoming later and later from 1987 to 1997. Since 1998, however, the initial blooming date came earlier and earlier year by year, with approximately 11.42 days advancement per year. From 1987 to 2007, the annual duration of algal blooms lengthened year by year, in line with the substantial increases in the occurrences of algal blooms in spring and summer months. The algal blooms usually occur in northern bays and spread to center and south parts of Lake Taihu. The increases in previous winter's mean daily minimum temperature partially contributed to the earlier blooming onset. However, human activities, expressed as total gross domestic product (GDP) and population, outweighed the climatic contribution on the initial blooming date and blooming duration. This study may provide insights for the policy makers who try to curb the algal blooming and improve the water quality of inland freshwater lakes.

Two-decade reconstruction of algal blooms in China's Lake Taihu.

https://espace.library.uq.edu.au/view/UQ:330506/UQ330506_OA.pdf

A review of ocean color remote sensing methods and statistical techniques for the detection, mapping and analysis of phytoplankton blooms in coastal and open oceans

Monitoring karenia brevis blooms in the gulf of mexico using satellite ocean color imagery and other data

Harmful algal blooms (HABs) pose a threat to public health, economies, and wildlife around the Nation's coasts. Monitoring for HABs has involved a reactive system, which is a logistically expensive system. Improved forecasting and monitoring could reducing the impact of the blooms. An example of an operational system has been developed for the blooms of the toxic dinoflagellate, Karenia brevis in the Gulf of Mexico

Moving to an operational system for forecasting harmful algal blooms

NOAA CoastWatch hosts nearly 2 petabytes of satellite oceanographic data on disk. These freely available data products cover two decades and are primarily stored as standalone NetCDF datasets. Global mapped datasets are processed daily and added to a long chain of previously processed data resulting in a valuable time series of oceanographic data such as sea surface temperature, chlorophyll, sea level anomaly, and sea surface winds. Three decades of experience have taught us that users access data in a myriad of ways. Some download entire collections of global datasets. Others prefer programmatic access using software tools to pull data matching their ‘on premise’ data while others prefer to locate higher level data to integrate into their own processing pipelines. The “NOAA CoastWatch Data Portal” was developed to address the challenges of accommodating our users’ requests. The portal facilitates access to data by providing multiple data-centric services: anonymous FTP/HTTPS service, THREDDS Data Server, and ERDDAP all accessible from a single online map viewer.The NOAA CoastWatch Data Portal map viewer (https://coastwatch.noaa.gov/cw_html/cwViewer.html) serves as the front door to our global data stores by providing visualization, links to product information, and access to datasets in part (i.e., subsets) or whole.In a typical map service, a single dataset is rendered to an image format such as PNG/JPEG for various zoom levels where the number of tiles rendered is 2^(2*zoom level) or a cumulative ~\87,000 images for 8 levels of zoom. The result is a snappy display of data, where the scale and color scheme is determined by the provider allowing little to no user customization. Generating tiles for a multi-decadal dataset results in hundreds of millions of tiles that may or may not be viewed. By contrast, in CoastWatch map tiles are dynamically generated directly from the source NetCDF datafiles using a Web Mapping Service. The result is a slightly slower display but allows user customization and access to pixel-level data. Users can select palettes, data scaling ranges and download the actual data viewed through the map viewer. The map viewer provides simplified access to our backend services.Data selection is performed through a user-controlled calendar and product checkboxes. A change to the date of interest results in a parallel change of that date across multiple products of interest, allowing a user to visualize multiple datasets on a selected date. Products can be promoted to an ‘active layer’ where the data for a selected date is then made persistent so it can be compared to another date. This is useful to identify changes over time. The map viewer has many additional features for data exploration and inter/intra comparison of data products.Data delivery (e.g., the downloading of files to a user) is handled by file services hosted through FTP/HTTPS, THREDDS, and ERDDAP services. FTP and HTTPS allow direct bulk download of entire datafiles or collections. THREDDS and ERDDAP host value-added data services such as OpenDAP allowing users to access partial or reformatted data. Many users access data programmatically using the OpenDAP protocol which facilitates machine-to-machine interoperability. Similarly, services such as ERDDAP’s GRIDDAP allows data subset and reformatting into a variety of formats including JSON, GeoTIFF, CSV, MatLab, etc. Both THREDDS and ERDDAP virtually aggregate data allowing queries to return values for a single pixel over time or download of a NetCDF dataset containing multiple time-levels of spatial data.The CoastWatch Data Portal map viewer will undergo an update over the next year incorporating changes in the underlying JavaScript mapping API. As systems and data move into cloud environments, CoastWatch users may have new expectations from our services. CoastWatch will be called upon to solve new challenges in data distribution. Cloud solutions provide us the opportunity to explore new data and information distribution models.

M. Soracco

Papers

Monitoring karenia brevis blooms in the gulf of mexico using satellite ocean color imagery and other data

Moving to an operational system for forecasting harmful algal blooms

Visualizing and Distributing Decades of Satellite Ocean Remote Sensing Data Products