Parasitism of photosynthetic dinoflagellates in a shallow subestuary of Chesapeake Bay, USA

Abstract

ABSTRACT-Rhode Rlver (USA) populatlons of the red-tlde d~noflagellates Gyrnnodinium sanguineum Hlrasaka, 1922, Cyi-odinium uncatenum Hulburt, 1957, and Scnppsiella trochoidea (Steln) Loeblich 111, 1976, were commonly infected by thelr parasltlc relative Amoebophrya cei-atil Cachon, 1964, d u n n g the summer of 1992. Mean ~nfection levels were relatively low, wlth data for vertically Integrated samples averaging 1.0, 1.9, and 6 5 % for G. sangujneum, G. uncatenum, and S , trocho~dea, respectively However, epldemlc outbreaks of A. ceratii (20 to 8 0 % hosts parasitized) occurred in G. uncatenum a n d S. trochoidea on several occasions, wlth peak levels of parasitism associated wlth decreases ~n host abundance. Estimates for paraslte Induced mortality indlcate that A, ceratil 1s capable of removlng a significant fraction of dinoflagellate blomass, with epldemics In the upper estuary cropplng u p to 5 4 % of the dominant bloom-forming species, G uncatenum, dally. However, epldemics were usually geographically restncted and of short duration, with dally losses for the 3 host species d u e to parasitism averaging 1 to 3 % over the summer. Thus, A ceratli appears capable of exerting a controlling Influence on bloonl-form~ng dinoflagellates of the Rhode River only when conditions a r e suitable for production of epidemlc infections. Interestingly, epidemics falled to occur in multlple d~noflagellate taxa sunultaneously, even when alternate host specles were present at hlgh densities. This observation, along with laboratory experiments demonstrating that parasites Isolated from G sanguineum wcre unable to infect G. uncatenum, S. trocholdea, and Ceratium furca, suggests that the dinoflagellate taxon A cerati] may represent a cluster of relatively host-speclfic specles.

132 Parasites and Phytoplankton, with a Special Emphasis on Dinoflagellate Infections

“…These parasites are broadly distributed in the northern hemisphere (Fig. 8), with numerous accounts from the North Atlantic, the North Pacific, and the Mediterranean Sea (Cachon 1964;Coats et al 1996;Elbrächter 1973;Fritz and Nass 1992;Gisselson et al 2002;Jacobson, 1987;Kofoid and Swezy 1921;Lebour 1917Lebour , 1925Maranda 2001;Nishitani, Erickson, and Chew 1985;Salomon, Janson, and Granéli 2003;Taylor 1968). Ongoing work has also shown Amoebophrya spp.…”

“…A large body of information on the taxonomy, morphology, development, and life history of parasitic dinoflagellates has been generated over the years and addressed in several review articles (Cachon 1964;Cachon and Cachon 1987;Coats 1999;Elbrächter and Schnepf 1998). The importance of parasitic dinoflagellates in the ecology of host organisms has received far less attention, with much of what we know on that topic limited to a few commercially important host species (Shields 1994) and some planktonic protists (Coats and Heisler 1989;Coats et al , 1996.…”

“…Cachon 1964, Nishitani, Erickson, andChew 1985), most Amoebophrya strains established in culture have shown a high degree of host specificity. For example, Coats et al (1996) were unsuccessful in transmitting Amoebophrya from Akashiwo sanguinea to Ceratium furca, Gyrodinium uncatenum, and Scrippsiella trochoidea when incubated in single or mixed host assemblages. More recently, Coats and Park (2002) showed that Amoebophrya strains from Akashiwo sanguinea, Gymnodinium instriatum, and Karlodinium micrum exhibited marked differences in parasite generation time, dinospore survival, and infectivity, with none of the strains able to successfully crossinfect the alternate host species.…”

“…Recent work, however, has questioned that view, as discussed below. Cachon (1964) Coats et al 1996; MGP., pers. observ.).…”

Relative grazing impact of microzooplankton and mesozooplankton on a bloom of the toxic dinoflagellate Alexandrium minutum

“…Interactions with other organisms are also important in determining the fate of algal populations. In this context, allelopathy, viruses, parasites and grazers are potential agents controlling red tides (Nagasaki et al 1994, Zingone 1995, Coats et al 1996, Turner & Tester 1997, Guisande et al 2002, Johansson & Coats 2002. Amongst the biological factors influencing HABs, grazing pressure stands out as the most direct and widespread.…”