Papers by Patrizia Ziveri
Palaeogeography, Palaeoclimatology, Palaeoecology, 2006
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Coccolithophorids are an important phytoplankton group and play a major role in the biogeochemist... more Coccolithophorids are an important phytoplankton group and play a major role in the biogeochemistry of the ocean system. The calcite platelets forming their skeleton - the coccoliths - make a significant contribution to the oceanic sedimentation, particularly in those regions where oligotrophic conditions prevail for most of the year, as is the case for the pelagic eastern Mediterranean Sea. Here we discuss the results related to present-day coccolith fluxes in the Ionian Sea (eastern Mediterranean) obtained from sediment trap moorings and surface sediment samples. Coccolith fluxes through the last 10 ky are also investigated from a selected sediment core. Past coccolith fluxes show high variability in both magnitude and species composition. In particular, strong differences are observed between normal pelagic sediments and the sapropel interval comprised in the record (S1). The relative importance of coccoliths in sediment accumulation is also calculated. Coccolith fluxes from sediment traps show wide seasonal and interannual variations and are quite diverse from site to site; species composition varies on a seasonal scale and specific patterns in the assemblages are observed. In particular, some differences in the relative abundance of some species appear when comparing the present data with previous records from the same location, and with surface sediment assemblage composition. Such variations can possibly be related to the recent modifications in the circulation pattern of the area.
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Frontiers in Marine Science, 2014
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Nature Communications
Planktonic calcifying organisms play a key role in regulating ocean carbonate chemistry and atmos... more Planktonic calcifying organisms play a key role in regulating ocean carbonate chemistry and atmospheric CO2. Surprisingly, references to the absolute and relative contribution of these organisms to calcium carbonate production are lacking. Here we report quantification of pelagic calcium carbonate production in the North Pacific, providing new insights on the contribution of the three main planktonic calcifying groups. Our results show that coccolithophores dominate the living calcium carbonate (CaCO3) standing stock, with coccolithophore calcite comprising ~90% of total CaCO3 production, and pteropods and foraminifera playing a secondary role. We show that pelagic CaCO3 production is higher than the sinking flux of CaCO3 at 150 and 200 m at ocean stations ALOHA and PAPA, implying that a large portion of pelagic calcium carbonate is remineralised within the photic zone; this extensive shallow dissolution explains the apparent discrepancy between previous estimates of CaCO3 productio...
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Regional Environmental Change
Direct human pressure on Marine Protected Areas (MPAs) adds to climate change impacts on marine h... more Direct human pressure on Marine Protected Areas (MPAs) adds to climate change impacts on marine habitats, especially in coastal biodiversity hot spots. Understanding MPA user perception towards the Coastal marine Habitats (CMHs) could improve awareness of the challenges that such areas have to face, eventually providing insights for the design of conservation and tourism management plans. We studied perception of ecosystem services, impacts and threats of CMHs by locals and tourists (n = 624) of Cap de Creus MPA (NW Mediterranean Sea). Overall, we found that perceptions of tourists and locals are similar. Respondents perceived that CMHs provide valuable regulating services, and they assigned less value to cultural services. Locals valued the food provision ecosystem service of CMHs significantly more than tourists, probably because of the historical importance of fisheries for subsistence. Respondents ranked marine pollution of inland origin, climate change and people’s behaviour to...
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Ocean acidification is considered a major threat to marine ecosystems and may particularly affect... more Ocean acidification is considered a major threat to marine ecosystems and may particularly affect calcifying organisms such as corals, foraminifera and coccolithophores. Here we investigate the impact of elevated pCO2 and lowered pH on growth and calcification in the common calcareous dinoflagellate Thoracosphaera heimii. We observe a substantial reduction in growth rate, calcification and cyst stability of T. heimii under elevated pCO2. Furthermore, transcriptomic analyses reveal CO2 sensitive regulation of many genes, particularly those being associated to inorganic carbon acquisition and calcification. Stable carbon isotope fractionation for organic carbon production increased with increasing pCO2 whereas it decreased for calcification, which suggests interdependence between both processes. We also found a strong effect of pCO2 on the stable oxygen isotopic composition of calcite, in line with earlier observations concerning another T. heimii strain. The observed changes in stable oxygen and carbon isotope composition of T. heimii cysts may provide an ideal tool for reconstructing past seawater carbonate chemistry, and ultimately past pCO2. Although the function of calcification in T. heimii remains unresolved, this trait likely plays an important role in the ecological and evolutionary success of this species. Acting on calcification as well as growth, ocean acidification may therefore impose a great threat for T. heimii.
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Palaeogeography, Palaeoclimatology, Palaeoecology, 2020
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Bulletin of the Geological Society of Greece, 2018
A quantitative analysis of coccolithophores, planktonic foraminifera and pollen assemblages was c... more A quantitative analysis of coccolithophores, planktonic foraminifera and pollen assemblages was carried out on core NS-14 (SE Aegean Sea), recovered in the Western Kos Basin. Eleven coccolithophore (ACE 1-11) and ten planktonic foraminifera (APFE1-10) ecozones have been recognized during the last 14 000 yrs using calcareous nannofossil and planktonic foraminifera abundances. Additionally eight pollen assemblage zones (PAZ 1-8) have been recognised. The established high resolution ecozonal scheme allows a detailed paleoecological reconstruction for the Holocene archive in the SE Aegean Sea, defining two warm and humid phases (9300-8600 yr caiBP and 7600-6400 yr caiBP) associated with the deposition of SI and a third one between 5200-4200 yr ca[BP.
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Earth-Science Reviews, 2017
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Biogeosciences Discussions, 2016
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Scientific reports, Jul 14, 2016
The Eastern Mediterranean Transient (EMT) occurred in the Aegean Sea from 1988 to 1995 and is the... more The Eastern Mediterranean Transient (EMT) occurred in the Aegean Sea from 1988 to 1995 and is the most significant intermediate-to-deep Mediterranean overturning perturbation reported by instrumental records. The EMT was likely caused by accumulation of high salinity waters in the Levantine and enhanced heat loss in the Aegean Sea, coupled with surface water freshening in the Sicily Channel. It is still unknown whether similar transients occurred in the past and, if so, what their forcing processes were. In this study, sediments from the Sicily Channel document surface water freshening (SCFR) at 1910 ± 12, 1812 ± 18, 1725 ± 25 and 1580 ± 30 CE. A regional ocean hindcast links SCFR to enhanced deep-water production and in turn to strengthened Mediterranean thermohaline circulation. Independent evidence collected in the Aegean Sea supports this reconstruction, showing that enhanced bottom water ventilation in the Eastern Mediterranean was associated with each SCFR event. Comparison be...
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Marine Chemistry, 2015
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Geochimica et Cosmochimica Acta, 2015
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Journal of Experimental Marine Biology and Ecology, 2014
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Coccolithophores, 2004
... NAD) which is the northward extension of the Gulf Stream system (Dietrich et al ... Bollmann ... more ... NAD) which is the northward extension of the Gulf Stream system (Dietrich et al ... Bollmann (1997) showed that Gephyrocapsa could be further subdivided and that the morphotypes ... indi-cate the dominant morphotype in Gephyrocapsa assemblages analyzed by Boll-mann (1997 ...
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Progress in Oceanography, 1999
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Papers by Patrizia Ziveri