We also make several recommendations for how the field can move forward 1) use process-based models to explicitly represent key physical and biological factors in HAB development, including evaluating HAB response to climate change in the context of the broader ecosystem; 2) quantify and convey model uncertainty using ensemble approaches and scenario planning; 3) use robust approaches to downscale global climate model results to the coastal regions that are most impacted by HABs; and 4) evaluate HAB models with long-term observations, which are critical for assessing long-term trends associated with climate change and far too limited in extent. Many phytoplankton species, including many harmful algal bloom (HAB) species, survive long periods between blooms through formation of benthic resting stages. Because they are crucial to the persistence of these species and the initiation of new blooms, the physiology of benthic stages must be considered to accurately predict responses to climate warming and associated environmental changes. The benthic stages of dinoflagellates, called resting cysts, germinate in response to the combination of favorable temperature, oxygen-availability, and release from dormancy. The latter is a mechanism that prevents germination even when oxygen and temperature conditions are favorable. Here, evidence of temperature-mediated control of dormancy duration from the dinoflagellates Alexandrium catenella and Pyrodinium bahamense-two HAB species that cause paralytic shellfish poisoning (PSP)-is reviewed and presented alongside new evidence of complementary, temperature-based control of cyst quiescence (the state in which cysts gnation through mass sexual induction. In areas where temperature seasonality restricts the flux of new swimming cells (germlings) to narrow temporal windows, warming is unlikely to promote longer and more intense HAB impacts-even when water column conditions would otherwise promote prolonged bloom development. Many species likely have a strong drive to sexually differentiate and produce new cysts once concentrations reach levels that are conducive to new cyst formation. This phenomenon can impose a limit to bloom intensification and suggests an important role for cyst bed quiescence in determining the duration of HAB risk periods. Almost every summer, dense blooms of filamentous cyanobacteria are formed in the Baltic Sea. These blooms may cause problems for tourism and ecosystem services, where surface accumulations and beach fouling are commonly occurring. Future changes in environmental drivers, including climate change and other anthropogenic disturbances, may further enhance these problems. By compiling monitoring data from countries adjacent to the Baltic Sea, we present spatial and temporal genus-specific distribution of diazotrophic filamentous cyanobacteria (Nostocales) during four decades (1979-2017). While the summer surface salinity decreased with a half up to one unit, the surface temperature in July-August increased with 2-3 °C in most sub-basins of the Baltic Sea, during the time period. The biovolumes of the toxic Nodularia spumigena did not change in any of the sub-basins during the period. On the other hand, the biovolume of the non-toxic Aphanizomenon sp. and the potentially toxic Dolichospermum spp. increased in the northern parts of the Baltic Sea, along with the decreased salinity and elevated temperatures, but Aphanizomenon sp. decreased in the southern parts despite decreased salinity and increased temperatures. These contradictory changes in biovolume of Aphanizomenon sp. between the northern and southern parts of the Baltic Sea may be due to basin-specific effects of the changed environmental conditions, or can be related to local adaptation by sub-populations of the genera. Overall, this comprehensive dataset presents insights to genus-specific bloom dynamics by potentially harmful diazotrophic filamentous cyanobacteria in the Baltic Sea. Sea surface temperatures in the world’s oceans are projected to warm by 0.4-1.4 °C by mid twenty-first century causing many tropical and sub-tropical harmful dinoflagellate genera like Gambierdiscus, Fukuyoa and Ostreopsis (benthic harmful algal bloom species, BHABs) to exhibit higher growth rates over much of their current geographic range, resulting in higher population densities. The primary exception to this trend will be in the tropics where temperatures exceed species-specific upper thermal tolerances (30-31 °C) beyond which growth slows significantly. Nazartinib As surface waters warm, migration to deeper habitats is expected to provide refuge. Range extensions of several degrees of latitude also are anticipated, but only where species-specific habitat requirements can be met (e.g., temperature, suitable substrate, low turbulence, light, salinity, pH). The current understanding of habitat requirements that determine species distributions are reviewed to provide fuller understanding of how individual species will respond to climate change from the present to 2055 while addressing the paucity of information on environmental factors controlling small-scale distribution in localized habitats. Based on the available information, we hypothesized how complex environmental interactions can influence abundance and potential range extensions of BHAB species in different biogeographic regions and identify sentinel sites appropriate for long-term monitoring programs to detect range extensions and reduce human health risks. There is increasing concern that accelerating environmental change attributed to human-induced warming of the planet may substantially alter the patterns, distribution and intensity of Harmful Algal Blooms (HABs). Changes in temperature, ocean acidification, precipitation, nutrient stress or availability, and the physical structure of the water column all influence the productivity, composition, and global range of phytoplankton assemblages, but large uncertainty remains about how integration of these climate drivers might shape future HABs. Presented here are the collective deliberations from a symposium on HABs and climate change where the research challenges to understanding potential linkages between HABs and climate were considered, along with new research directions to better define these linkages. In addition to the likely effects of physical (temperature, salinity, stratification, light, changing storm intensity), chemical (nutrients, ocean acidification), and biological (grazer) drivers on microalgae (senso lato), symposium participants explored more broadly the subjects of cyanobacterial HABs, benthic HABs, HAB effects on fisheries, HAB modelling challenges, and the contributions that molecular approaches can bring to HAB studies.