Morphology, phylogeny, dynamics, and ichthyotoxicity of Pheopolykrikos hartmannii (Dinophyceae) isolates and blooms from New York, USA

Abstract

We report on morphological observations, phylogenetic analyses, bloom dynamics, and ichthyotoxicity of the common but poorly characterized dinoflagellate Pheopolykrikos hartmannii (Zimmermann) Matsuoka et Fukuyo. From 2008 to 2010 in the Forge River Estuary, NY, USA, P. hartmannii bloomed during summer and early fall, achieving densities exceeding 8,000 cells · mL(-1) and often dominating microphytoplankton communities. Large subunit (LSU) and small subunit (SSU) rDNA sequences demonstrated that NY isolates of P. hartmannii sequences were 99%-100% identical to P. hartmannii isolates from eastern US and Korea. In both the LSU and SSU rDNA phylogenies, the clades containing P. hartmannii sequences were distinct sister clades to those composed of Polykrikos schwartzii and P. kofoidii. In the LSU rDNA phylogeny, however, the clade composed of P. hartmannii and a sequence of the photosynthetic Polykrikos lebourae was well separated from the clade composed of 10 entries of Polykrikos schwartzii and P. kofoidii. In addition, a gap of ~180 bases was observed when the LSU rDNA sequences of P. hartmannii were aligned with P. schwartzii and P. kofoidii but was not observed in the alignment between P. hartmannii and P. lebourae. Using scanning electron microscopy, several morphological features previously not reported for P. hartmannii were observed: a ventral groove located in the sulcus, a deep arc-like apical concavity within the area of apical groove, scale-like vesicles, and a shallow, completely enclosed, loop-like apical groove. Resting cysts with arrow-like surface spines were produced heterothallically by crossing clonal isolates and germinated single gymnoid cells. Finally, filtered and unfiltered bloom water from the Forge River and clonal cultures of P. hartmannii exhibited acute ichthyotoxicity to juvenile sheepshead minnows (Cyprinodon variegates) and aeration did not mitigate this effect, suggesting P. hartmannii is an ichthyotoxic, harmful alga.

Sexual resting cyst production by the dinoflagellate Akashiwo sanguinea: a potential mechanism contributing to the ubiquitous distribution of a harmful alga

“…) and Pheopolykrikos hartmannii (Tang et al. ), more abundantly than C. polykrikoides (< one cyst per 1,000 cells; Tang and Gobler ), and less abundantly than Scrippsiella trochoidea (Y. Z. Tang & C. J. Gobler, personal observation).…”

“…), and Pheopolykrikos hartmannii (Matsuoka and Fukuyo , Tang et al. ) which produce cysts with a thick cyst wall and spine‐like surface processes. In addition, cysts of A. sanguinea were morphologically similar to cysts recently observed from another unarmored, HAB‐forming dinoflagellate, Cochlodinium polykrikoides (Tang and Gobler ) which also had thin cyst walls, a smooth surface (lack of surface projections), and a round shape (for typical mature cysts).…”

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“…hartmannii and its toxicity from the Atlantic ocean in the warm seasons (when water temperatures generally exceeded 25°C) (Gárate-Lizárraga, 2013;Badylak & Phlips, 2004;Tang, Harke & Gobler, 2013). As for the present study, sampling area has been characterized by high freshwater inputs by the river after severe rainfall in winter period.…”

“…P. hartmanii has been referred as a harmful and ichthyotoxic species in the literature, but limited toxicity studies are available although it is widely distributed all over the world seas. Acute ichthyotoxicity of P. hartmannii to juvenile sheepshead minnows (Cyprinodon variegates Lacepède, 1803) was given from the Atlantic Ocean by Tang et al (2013). Considering the natural and anthropogenic pressures on the region, the presence of this species represent a potential risk due to the ichthyotoxicity and potential harmful effect of massive blooms, ecosystem and human health as well as local economy (i.e.…”

“…Low water temperature cannot provide a suitable environment for the growth of this species. Low water temperature (10 (According to Chatton, 1933;Hulburt, 1957;Matsuoka & Fukuyo, 1986;Nehring, 1997;Lee, Kim, & Lee, 1998;Morquecho et al, 2003;Badylak & Phlips, 2004;Wang et al, 2004;Pena-Manjarrez et al, 2005;Fujii and Matsuoka 2006;Mizushima et al, 2007;D'Costa et al, 2008;Shin et al, 2010;Hoppenrarth et al, 2010;Shin et al, 2011;Srivilai, Lirdawitayaprasit & Fukuyo, 2012;Tang et al, 2013;Garate -Lizargara, 2014;Moncheva, 2015;EscobarMorales & Hernández-Becerril, 2015;Balkıs et al,2016). °C) may be limited growth of the species.…”