Abstract
SUMMARY: The presence of resting stages in neritic areas is well known, while their occurrence in the deep sea realm has seldom been considered. Recent investigations showed strict interactions between neritic and deep sea domains, due to upand down-welling phenomena driven by submarine canyons. To estimate the presence of resting stages in deep bottom sediments, seven sediment cores, collected along a trans-Mediterranean transect by means a multi-corer during the TRANSMED survey (1999), were studied. Most biogenic sediment was composed of Foraminifera tests (tens of thousand tests cm -3 ), Calciodinellum albatrosianum and Leonella granifera (Dinophyta) cysts (up to thousands cysts cm -3 ). Eleven dinocyst morphotypes were recorded mainly as empty shells (seven calcareous-walled: C. albatrosianum, Calciperidinium asymmetricum, Leonella granifera, Scrippsiella trochoidea, S. precaria type 1, S. precaria type 2, S. regalis; four organicwalled: Impagidinium aculeatum, unid. dinocyst 1, unid. dinocyst 2 and unid. dinocyst 3), while no metazoan resting eggs were observed. The presence of viable resting stages in deep bottom surface sediments was much lower than in neritic areas, suggesting that oceanic species do not produce cysts for a “benthic resting” strategy. Further taxonomic and biogeographic studies are needed to better understand the ecological dynamics of oceanic plankton in the Mediterranean Sea.
Highlights
Dormancy is a common life cycle trait in marine plankton
Most ecological investigations on plankton organisms producing resting stages focused on neritic areas and dealt with taxonomy (Matsuoka, 1988; Lewis, 1991; Dale et al, 1993; Matsuoka and Cho, 2000), biogeography (Lindley, 1990; Nehring, 1997; Persson et al, 2000), toxic aspects related to harmful algal blooms (Han and Terazaki, 1993; Matsuoka and Fukuyo, 1994; Mackenzie et al, 1996; Ellegaard and Oshima, 1998; Dale et al, 1999), alien species invasions (Hallegraeff and Bolch, 1992; Carlton and Geller, 1993; Hallegraeff, 1998; Hamer et al, 2000), and population dynamics (Uye, 1985; Ishikawa and Taniguchi, 1996) of single taxa
(1983) for dinoflagellates and Uye (1985) for copepods, was recently considered as one of the most important keys to understand the dynamics of the whole plankton community (Boero, 1994; Boero et al, 1996)
Summary
Dormancy is a common life cycle trait in marine plankton. Resting stages were recorded in crustaceans (Onbé, 1991; Mauchline, 1998), diatoms (Mc Quoid and Hobson, 1995, 1996), dinoflagellates (Wall and Dale, 1968; Bolch and Hallegraeff, 1990; Sonneman and Hill, 1997; Nehring, 1997) and tintinnids (Reid and John, 1978; Kamiyama, 1996).Most ecological investigations on plankton organisms producing resting stages focused on neritic areas and dealt with taxonomy (Matsuoka, 1988; Lewis, 1991; Dale et al, 1993; Matsuoka and Cho, 2000), biogeography (Lindley, 1990; Nehring, 1997; Persson et al, 2000), toxic aspects related to harmful algal blooms (Han and Terazaki, 1993; Matsuoka and Fukuyo, 1994; Mackenzie et al, 1996; Ellegaard and Oshima, 1998; Dale et al, 1999), alien species invasions (Hallegraeff and Bolch, 1992; Carlton and Geller, 1993; Hallegraeff, 1998; Hamer et al, 2000), and population dynamics (Uye, 1985; Ishikawa and Taniguchi, 1996) of single taxa. Recent micro-palaeontological studies focused on dinoflagellate resting stages on the surface sediments of deep waters for taxonomic as well as palaeo-climatic investigations (Zonneveld, 1995; Zonneveld and Brummer, 2000; Vink et al, 2000a; b; Meier, 2002). Due both to sampling difficulties and scant attention to the role of resting stages in the meiobenthic domain (Pati et al, 1999), the presence of cysts in deep sea bottoms has been seldom considered. Della Tommasa et al (2000) recorded a high concentration of resting stages (both Protoctista and Metazoa) in the
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