Harmful Algal Blooms. A scientific summary for policy makers

What is a Harmful Algal Bloom (HAB)? Photosynthetic algae support healthy aquatic ecosystems by forming the base of the food web, fixing carbon and producing oxygen. Under certain circumstances, some species can form high-biomass and/or toxic proliferations of cells (or “blooms”), thereby causing harm to aquatic ecosystems, including plants and animals, and to humans via direct exposure to water-borne toxins or by toxic seafood consumption. Ecosystem damage by high-biomass blooms may include, for instance, disruption of food webs, fish-killing by gill damage, or contribution to low oxygen “dead-zones” after bloom degradation. Some species also produce potent natural chemicals (toxins) that can persist in the water or enter the food web, leading to illness or death of aquatic animals and/or human seafood consumers

Core research project: harmful algal blooms in upwelling systems

Global Ecology and Oceanography of Hatmful algal Blooms (GEOHAB): synthesis open science meeting, Paris, France, 24-26 April 2013The Core Research Project: HABs in upwelling systems was initiated by means of an Open Science Meeting in Portugal in November 2003. Eight key questions were formulated to address our understanding of the ecology and oceanography of HABs in upwelling systems. These questions related to the identification of adaptive strategies that characterize HAB species in upwelling systems, including seeding strategies, the influence of small-scale physical processes and nutrient supply in affecting HAB population dynamics, the role of genetic predisposition versus environmental conditions in toxin production, the influence of coastal morphology and bathymetry in determining the distribution of HABs, the relative importance of cross-shelf and along-shore advection for HABs, and the linkages of HAB events and climate. Following a comparative review of the ecology and oceanography of HABs in upwelling systems through publication of a special issue of Progress in Oceanography in 2010 we highlight further advances in addressing the above questions. We specifically examine achievements in terms of the overall goal of GEOHAB of prediction supported by observation and modelling systems. The comparative approach, as endorsed by GEOHAB, is considered to have added value to regional or national science programmes. Furthermore the CRP is deemed to have provided effective direction to HAB research in upwelling systems over the past decade which has improved the availability of comparable data. Prediction of HABs nevertheless remains limited by ecological complexity. However increasingly realistic hydrodynamic models with high spatial resolution now lay the groundwork for better prediction through incorporation of better resolved ecological properties and processesN

Unexpected presence of the nitrogen-fixing symbiotic cyanobacterium UCYN-A in Monterey Bay, California

In the last decade, the known biogeography of nitrogen fixation in the ocean has been expanded to colder and nitrogen-rich coastal environments. The symbiotic nitrogen-fixing cyanobacteria group A (UCYN-A) has been revealed as one of the most abundant and widespread nitrogen-fixers, and includes several sublineages that live associated with genetically distinct but closely related prymnesiophyte hosts. The UCYN-A1 sublineage is associated with an open ocean picoplanktonic prymnesiophyte, whereas UCYN-A2 is associated with the coastal nanoplanktonic coccolithophore Braarudosphaera bigelowii, suggesting that different sublineages may be adapted to different environments. Here, we study the diversity of nifH genes present at the Santa Cruz Municipal Wharf in the Monterey Bay (MB), California, and report for the first time the presence of multiple UCYN-A sublineages, unexpectedly dominated by the UCYNA2 sublineage. Sequence and quantitative PCR data over an 8-year time-series (2011–2018) showed a shift toward increasing UCYN-A2 abundances after 2013, and a marked seasonality for this sublineage which was present during summer-fall months, coinciding with the upwelling-relaxation period in the MB. Increased abundances corresponded to positive temperature anomalies in MB, and we discuss the possibility of a benthic life stage of the associated coccolithophore host to explain the seasonal pattern. The dominance of UCYN-A2 in coastal waters of the MB underscores the need to further explore the habitat preference of the different sublineages in order to provide additional support for the hypothesis that UCYN-A1 and UCYN-A2 sublineages are different ecotypes

Global solutions to regional problems: Collecting global expertise to address the problem of harmful cyanobacterial blooms. A Lake Erie case study

In early August 2014, the municipality of Toledo, OH (USA) issued a ‘do not drink’ advisory on their water supply directly affecting over 400,000 residential customers and hundreds of businesses (Wilson, 2014). This order was attributable to levels of microcystin, a potent liver toxin, which rose to 2.5 μg L−1 in finished drinking water. The Toledo crisis afforded an opportunity to bring together scientists from around the world to share ideas regarding factors that contribute to bloom formation and toxigenicity, bloom and toxin detection as well as prevention and remediation of bloom events. These discussions took place at an NSF- and NOAA-sponsored workshop at Bowling Green State University on April 13 and 14, 2015. In all, more than 100 attendees from six countries and 15 US states gathered together to share their perspectives. The purpose of this review is to present the consensus summary of these issues that emerged from discussions at the Workshop. As additional reports in this special issue provide detailed reviews on many major CHAB species, this paper focuses on the general themes common to all blooms, such as bloom detection, modeling, nutrient loading, and strategies to reduce nutrients