Corrigendum to “A Holocene dinocyst record of a two-step transformation of the Neoeuxinian brackish water lake into the Black Sea” [Quaternary International, 197 (2009) 72–86

Corrigendum to “A Holocene dinocyst record of a two-step transformation of the Neoeuxinian brackish water lake into the Black Sea” [Quaternary International, 197 (2009) 72–86

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  A Holocene dinocyst record of a two-step transformation of the Neoeuxinian brackish water lake into the Black Sea Fabienne Marret 1* , Peta Mudie 2 , Ali Aksu 3 , Richard N. Hiscott 3   1 Department of Geography, University of Liverpool, Liverpool, L69 7ZT, UK; 2 Geological Survey Canada Atlantic, Dartmouth, Nova Scotia B2Y 4A2, Canada; 3 Department Earth Sciences, Memorial University of Newfoundland, St. John's, Newfoundland, A1B 3X5, Canada;; *corresponding author; Tel. +44 (0)151 794 28 48; Fax +44 (0)151 794 2866  Abstract  An exceptionally high-resolution and species-rich dinoflagellate cyst record from core M02-45 collected from the southwestern Black Sea shelf provides strong evidence of a gradual reconnection between the Black (BS) and Mediterranean (MS) seas at the beginning of the Holocene. Two main assemblages, one dominated by brackish species, Spiniferites    cruciformis   and Pyxidinopsis    psilata  , and freshwater algae, and a subsequent one, characterised by euryhaline species ( Lingulodinium    machaerophorum  , Brigantedinium   spp., Protoperidinium    ponticum  ), document a progressive change in sea-surface conditions from low saline (~7–12 psu) to present-day conditions. A first major pulse of marine waters is recorded at around 8.46 ka BP, with a maximum of L. machaerophorum  . The occurrence of this species from the bottom of the core, dated at 9.3 ka BP, supports the hypothesis that water levels were already high on the southwestern shelf by that time. Fully present-day conditions are recorded at around 5.6 ka BP, when brackish species and morphotypes of Spiniferites    belerius  , Spiniferites    bentorii   and L . machaerophorum   disappeared. Arrivals of Mediterranean species ( Operculodinium    centrocarpum   and Spiniferites    mirabilis  ) are observed simultaneously in the southwest and southeast region of the BS at around 7 ka BP. Despite a different protocol for palynomorph preparation and presentation of data, previous studies from the northern shelf also document the arrival of euryhaline species at 7 ka BP, and marine influence prior to that time. The history of harmful algal blooms (HABS) shows a correlation with warmer mid-Holocene temperatures, followed by a succession of introductions possibly associated with early Greek exploration, then merchant shipping. Keywords : Dinocysts, Black Sea shelf, paleosalinity, brackish, morphotypes; harmful algae  1. Introduction Over the last few years, the timing of, and the conditions in effect during the Holocene transition of the Black Sea from freshwater-brackish to marine have been the subject of wide debate, leading to the recent publication of the book “The Black Sea Flood Question” (Yanko-Hombach et al. , 2007). The proposed hypothesis of Ryan et al.  (2003) that a catastrophic flood took place at around 8.4 ka BP when the Black Sea Level (BSL) was at -95m has been challenged by Aksu  et al.  (2002a, b) and Hiscott  et al.  (2002) (see Hiscott et al. , 2007 and in press, for more detail) with their Outflow Hypothesis  . Multiproxy studies based on sedimentology, geochemistry and micropalaeontology document major changes at the beginning of the Holocene, but the timing and extent of these events are not in agreement with the Ryan et al.  (2003) hypothesis, reinforced in Ryan (2007), with the exception of the recognition by both research groups of a significant marine incursion at around 8.4 ka BP (~9.4 cal ka BP; Major   et al. , 2006). Amongst these micropaleontological studies, organic-walled dinoflagellate cyst records have provided some significant evidence regarding the Black Sea surface water salinity prior to and after its connection to the Marmara Sea (Mudie  et al. , 2001, 2002). Indeed, after the pioneering work of Wall et al.  (1973) on Holocene dinocyst records in the Black Sea, a number of studies have been completed, in particular, in the southwestern and northwestern region of the Black Sea (Table 1, Fig. 1). These studies all document the occurrence of two to three successive dinoflagellate cyst (=dinocyst) assemblages, showing, for the early part of the Holocene, the dominance of the quasi-endemic Spiniferites cruciformis  - Pyxidinopsis psilata   association, followed by the dominance of cosmopolitan euryhaline species such as Lingulodinium    machaerophorum   accompanied by Mediterranean-related Spiniferites   and Operculodinium   species, and near the top of the Holocene, an increase in heterotrophic protoperidinioid cysts.  The succession of these dinocyst associations is very significant for establishing the timing of the Mediterranean water incursions into the Black Sea at the beginning of the Holocene. Indeed, Mudie  et al. (2004) demonstrate water exchange between the Marmara and the Black Seas around 9.5 ka BP, based on eight cores collected in the Marmara Sea, the southeastern Black Sea basins and the southwestern Black Sea shelf. More recently, the compilation of dinocyst records from the deep western part of the Black Sea (Atanassova, 2005) suggests that the inflow of Mediterranean waters occurred only later, around 7.1–7.5 ka BP, although there is some indication from these data that a marine influence was present at the beginning of the Holocene. Indeed, Filipova-Marinova (2007) points out the occurrence of single cysts of L. machaerophorum   at around 9.6 ka BP in deep-sea sediments off the Bulgarian shelf. In addition to the importance of organic-walled dinocysts as markers of surface water salinity (top ~50–100m), recent studies have begun to establish the importance of certain cyst species as markers of excess eutrophication in polluted marine waters (e.g. Dale  et al. , 1999; Matsuoka, 1999; Matsuoka  et al. , 2003; Mudie et al. , 2004) and as proxies for tracing the history of red tides and harmful algal blooms (HABs). The eutrophication in the Black Sea over the past 30 years has been accompanied by an increase in massive outbreaks of the calcareous-forming dinocyst Scrippsiella trochoidea,  in addition to the white tides caused by the coccolith Emiliania huxleyi (Eker-Develi and Kideys, 2003; O ğ uz and Merico, 2006). Some previous studies have attempted to outline this history of dinocyst HABS for the Black Sea (Mudie et al. , 2004, in press). However, with the exception of a few samples from an 11 m-long piston core 1474P studied by Wall et al.  (1973), and dated from 8.6–22.83 ka BP, most of the past records shown in Figure 1 are based on short cores (i.e., 60–250 cm long). These cores provide only very low resolution records, on the order of millennia in the Black Sea to centuries in Marmara Sea. Furthermore, a different protocol for sample  preparation for dinocyst analysis may explain the low dinocyst species diversity documented by Atanassova (2005) and by Filipova-Marinova (2006), as their pollen preparation followed the acetolysis method (Faegri and Iversen, 1989) that has been recognised as responsible for degrading or destroying protoperidinoid cysts sensitive to oxidation (Dale, 1976; Marret, 1993; Head, 1996; Hopkins and McCarthy, 2002). Acetolysis treatment also darkens cysts and makes them more difficult to distinguish from reworked Pleistocene dinocysts (see discussion by Ravazzi, 2006). We use only acid digestion and sieving for cyst preparation, and we do not use the oxidant KOH that also damages delicate cysts. We present here a new record of organic-walled dinocyst assemblages with decadal to centennial resolution, from a 950 cm-long core M02-45 collected at a water depth of 69 m from the southwestern shelf of the Black Sea (Fig. 2). Several radiocarbon dates (discussed below) indicate that the core covers the last 9.3 ka, with only one hiatus at 270 cm, spanning ~4.5–2.5 ka (Hiscott  et al. , in press). The sampling resolution for this core is multi-decadal, thereby reducing the possibility that a major catastrophic event could be missed. This high resolution dinocyst record is discussed here in detail in order to further evaluate the validity of the catastrophic flood hypothesis proposed by Ryan  et al.  (1997, 2003) and Ryan (2007) versus   the gradual drowning or outflow hypothesis of Aksu et al.  (2002b) and Hiscott  et al.  (2007). We further compare the Black Sea shelf dinocyst assemblages with the recent record of dinocysts from Central Asian seas (Marret et al. , 2004) in order to refine the salinity ranges of 3–12 psu (practical salinity unit) previously assigned to the early Holocene cyst assemblages by various workers (Wall et al. , 1973; Mudie et al. , 2001, 2004, Filipova-Marinova, 2007). 2. Regional setting 2.1. Oceanography
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