Red coloration of oysters along the French Atlantic coast during the 1998 winter season: implication of nanoplanktonic cryptophytes

Abstract

During a 4-week experiment on oyster grazing in coastal ponds (claires) near La Rochelle (France), a red coloration was observed in the digestive gland of oysters. This pigmentation was attributed to an intensive grazing on cryptophyte nanoflagellates. Three different techniques led to this conclusion, mentioning for the first time free-living cryptophytes as responsible for such a phenomenon. Spectrofluorometry was used to demonstrate that the red coloration was due to the presence of a phycoerythrin, characteristic of cryptophytes. Microscopic observations and accessory pigments analyses in water ponds confirmed that the source of this pigment was of cryptomonadal origin. Oyster grazing on these algae is evidenced by large differences in alloxanthin concentrations and flagellate abundances between the two experimental ponds. The winter occurrence of this phenomenon is of importance for oyster commercialization and a short-term depuration is suggested to remove the undesirable pigmentation.

Trophic environments influence size at metamorphosis and recruitment performance of Pacific oysters

“…Cryptophytes are mixotrophic nano-flagellates that play a role in the remineralization of organic matter and in predation on picoplankton such as the Synechococcus sp. picocyanobacteria (Yoo et al 2017) and bacteria (Klaveness 1989, Pastoureaud et al 2003. The appearance of picocyanobacteria (mostly Synechococcus sp.)…”

“…These mixotrophic features (Cloern & Dufford 2005) make cryptophytes revealers of a transitional state during oligotrophication. What is more, thanks to their high nutritional values, digestibility and nanophytoplankton size, cryptophytes are considered as good prey for filter feeders like adults oysters (Klaveness 1989, Pastoureaud et al 2003). However, cryptophytes have ejectile organelles named trichocysts/ejectosoms (Klaveness 1989) that may play a defensive role against predation by protozoa (Yamagishi et al 2012).…”

Cryptophyte bloom in a Mediterranean estuary: High abundance of <em>Plagioselmis</em> cf. <em>prolonga</em> in the Krka River estuary (eastern Adriatic Sea)

“…Although cryptophytes are considered a "high-quality" food, lacking hard exoskeleton structures or toxic metabolic products (Brett andMüller-Navarra 1997, Sterner andSchulz 1998), their higher content in bivalve food causes the red colouration of the tissue, making the mariculture products unfavourable for commercial needs (Pastoureaud et al 2003). Furthermore, cryptophytes are essential for the development of toxic or harmful blooms of some dinoflagellates (Adolf et al 2008) and ciliates (Peterson et al 2013).…”

“…Furthermore, red tides caused by cryptophyte blooms were observed in natural environments (Laza-Martínez 2012 and the references therein) and enclosed oyster ponds (Pastoureaud et al 2003). However, cryptophyte blooms in the Mediterranean Sea are very rare and exceptional events.…”

Phytoplankton diversity during the spring bloom in the northwestern Mediterranean Sea

“…Largely distributed worldwide, Plagioselmis prolonga has been recorded in British waters (Butcher 1967), Irish and Baltic seas (Hill 1992a), Skagerrak, North Sea (Kuylenstierna and Karlson 1994), La Rochelle, France (Pastoureaud et al 2003, Charles et al 2005, Novarino 2005, and San Francisco Bay (Cloern and Dufford 2005) and Salton Sea in California (Barlow and Kugrens 2002). In the Mediterranean Sea, the species has been recorded along Spanish coasts and the Alboran Sea (Margalef 1969, Novarino 2005, Gulf of Naples (Cerino and Zingone 2006), and Adriatic Sea near the Po River delta lagoon (Andreoli et al 1986).…”