Recent insights about relationships between nutrient availability, forms, and stoichiometry, and the distribution, ecophysiology, and food web effects of pelagic and benthic Prorocentrum species Patricia M. Glibert a, *, JoAnn M. Burkholder b , Todd M. Kana a a University of Maryland Center for Environmental Science, Horn Point Laboratory, P.O. Box 775, Cambridge, MD 21613, USA b Center for Applied Aquatic Ecology, North Carolina State University, Raleigh, NC 27606, USA 1. Introduction Planktonic Prorocentrum species are among the most commonly recognized harmful algae that are increasing in frequency, duration, and magnitude globally (Heil et al., 2005; Glibert et al., 2008). Because of the increasing importance of this genus in blooms worldwide, a special issue of the journal Harmful Algae in 2005 was devoted to arguably the most well known species, Prorocentrum minimum, including its taxonomy, its ecology throughout the world, its effects on food webs, and various aspects of its physiological regulation (Glibert and Sellner, 2005). Our knowledge base about this and other planktonic Prorocentrum species continues to expand at a remarkable pace. In contrast, ecological information about toxigenic benthic Prorocentrum species is much more limited. Here, we summarize recent findings about both planktonic and benthic Prorocentrum species, particularly in the subject areas of biogeography, physiology, bloom ecology, and food web effects, emphasizing their relation- ships with nutrients and nutrient stoichiometry and major research needs. We also assess the range of mechanisms or ‘‘strategies’’ that these species use to acquire nutrients, and how their populations can be maintained under conditions of nutrient or energy imbalance. Given the current trajectory of expansion of certain planktonic Prorocentrum species, and the threat to both ecosystem and human health from toxigenic benthic Prorocentrum species, this genus will continue to be of central importance in the study of harmful algae. While our understanding of the global distribution, ecology and toxicology of planktonic Prorocentrum species has increased in recent years, so too has our understanding of nutrient loads to the coastal zone which can contribute to the growth and expansion of their high-biomass blooms. The relationship between increasing total nutrient loads and increased abundance of harmful algae is now well recognized as an expression of eutrophication (Anderson, 1989; Anderson et al., 2002, 2008; Glibert et al., 2005a,b, 2010; Glibert and Burkholder, 2006; Heisler et al., 2008), but the overall Harmful Algae 14 (2012) 231–259 A R T I C L E I N F O Article history: Available online 3 November 2011 Keywords: Allelopathy Global distribution High-biomass blooms Mixotrophy N:P ratios Toxins A B S T R A C T The genus Prorocentrum includes six planktonic species that form high-biomass blooms, and at least nine predominantly benthic toxigenic species. Four of the plankters, including P. minimum, the only plankter reported to be toxigenic, are among the most commonly recognized harmful algae that are increasing in frequency, duration, and magnitude globally. Culture studies suggest a species group that generally grows maximally at inorganic nutrient N:P ratios just below Redfield proportions. However, field studies indicate that planktonic Prorocentrum species bloom when nutrients are at high N:P ratios relative to Redfield proportions. In the benthic species P. lima complex, toxin production has been shown to be inversely related to nutrient limitation, increasing when nutrient ratios are above Redfield proportions. Mixotrophy and allelopathy can play an important role in the interactions among planktonic Prorocentrum species, diatoms and other dinoflagellates, but little information is available for benthic taxa. The available information suggests that there are allelopathic interactions among benthic species and other algae, and that benthic species also can adversely affect finfish and shellfish health. While high growth rates may allow these plankters to initiate blooms, adaptive physiology is hypothesized to allow blooms to be maintained at less than maximal growth rates and at non-optimal N:P ratios. Given the projection for land-based nutrient export to continue to increase, it is expected that there will be further expansion of planktonic harmful Prorocentrum spp. globally and more intensive or more toxic benthic occurrences in the future. ß 2011 Elsevier B.V. All rights reserved. * Corresponding author. Tel.: +1 410 221 8422. E-mail address: glibert@umces.edu (P.M. Glibert). Contents lists available at SciVerse ScienceDirect Harmful Algae jo u rn al h om epag e: ww w.els evier.c o m/lo cat e/hal 1568-9883/$ – see front matter ß 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.hal.2011.10.023