In this article, we will discuss Ecology of Dinoflagellates. So, let’s get started.
Ecology of Dinoflagellates
Dinoflagellates live in all aquatic environments and have been observed both in snow and sea ice (Taylor et al., 2008). They are most abundant in shallow marine settings but also occur in fully oceanic environments. The biogeographic distribution is primarily determined by temperature, and the same
species occur within similar climatic zones in both hemispheres. True endemism is rare, and some species have a bipolar distribution. More than 2,300 species have been described (Gómez, 2012) of which more than 180 are marine benthic (Hoppenrath et al., 2014) and 350 freshwater species (Mertens et al., 2012).
Dinoflagellates have diverse feeding mechanisms and utilize various modes of nutrition: they may be phototrophic, heterotrophic, and mixotrophic and may be free living, endosymbionts, or parasites (Jeong et al., 2010). Most species are probably mixotrophic or heterotrophic feeding on diverse preys such as bacteria, picoeukaryotes, nanoflagellates, diatoms, other dinoflagellates, heterotrophic protists, and metazoans or ingest particulate matter or dissolved substances. They are important in planktonic marine food webs since they may have both a considerable grazing impact on natural populations and are excellent prey for mixotrophic protists and metazoans. Together with diatoms and coccolithophores, dinoflagellates are among the most prominent marine primary producers today, thus playing an important role in the global carbon cycle.
Dinoflagellate Cysts (Dinocysts)
Dinoflagellates may form different types of cysts during various stages of their complex life cycle that involve asexual and sexual and motile and nonmotile stages (Taylor, 1987). Resting cysts represent a dormant stage in which normal life processes are greatly reduced. They are part of the sexual reproduction cycle (hypnozygotes) but may also be formed asexually (Kremp, 2013). Vegetative cysts are metabolically and/or reproductively active nonmotile cells. Temporary cysts are formed asexually as a result of adverse conditions. Digestion cysts that form after feeding are rare. Dale (1983) suggests that resting cysts may have three possible functions: protection, propagation, and dispersion. The latter may be extremely
effective in introducing viable dinocysts into new geographic areas via transport in ships’ ballast water (Taylor et al., 2008). Resting cysts may remain viable in sediments for centuries (Ribeiro et al., 2011). Formation of resting cysts is a complex process and may be induced by various biotic and abiotic factors but is often related to peak abundances of the vegetative cells occurring at various times of the year (e.g., Matthiessen et al., 2005). After a mandatory dormancy period of variable length, excystment is triggered by different environmental factors. The cytoplast excysts through an opening in the cell wall, the
archeopyle, which is an important feature for taxonomic definition of cyst genera. Only a minority of living dinoflagellates produce resting cysts (less than 20 %, Head, 1996). Establishing cyst-theca relations are complicated by the fact that a single dinoflagellate species may produce cyst morphotypes attributable to different cyst species (Rochon et al., 2009).