Increased Chlorophyll Levels in the Southern Caspian Sea Following an Invasion of Jellyfish

A significant correlation was observed between satellite derived chlorophyll a (Chl a) concentrations and the biomass of the invasive comb jellyfish Mnemiopsis leidyi in the southern Caspian Sea. By consuming the herbivorous zooplankton, the predatory ctenophore M. leidyi may have caused levels of Chl a to rise to very high values (∼9 mg m−3) in the southern Caspian Sea. There might also be several other factors concurrent with predation effects of M. leidyi influencing Chl a levels in this region, such as eutrophication and climatic changes which play major roles in nutrient, phytoplankton, and zooplankton variations. The decrease in pelagic fishes due to overfishing, natural, and anthropogenic impacts might have provided a suitable environment for M. leidyi to spread throughout this enclosed basin

Editorial: Phytoplankton dynamics under climate change

Phytoplankton plays an important role in ocean processes, and is well-known to have an enormous positive impact on climate change or more specifically on global warming, by reducing atmospheric CO2 levels through the sinking of produced organic and inorganic matter to the deep ocean (Falkowski, 2012; Beardall and Raven, 2013). However, climate change, with consequences of elevated seawater temperatures and decreased pH levels (Beardall and Raven, 2013), influences phytoplankton dynamics, changing phytoplankton composition, geography and biomass in the oceans (Falkowski and Oliver, 2007; Boyd et al., 2015; Jonkers et al., 2019). Temperature increases could also drive temporal shifts in the onset of the regular annual blooms, their composition, duration and amplitude as well as mismatches in timing between trophic levels (Hinder et al., 2012; Mikaelyan et al., 2015). The overall impact of increased temperature on phytoplankton is not easy to assess due to variable and complex repercussions. For example, increasing temperatures can lead to more stratified waters, especially in summer months, and prevent nutrient replenishment at the ocean surface.info:eu-repo/semantics/publishedVersio

Regional Bio-optical Relationships and Algorithms for the Adriatic Sea, the Baltic Sea and the English Channel/North Sea Suitable for Ocean Colour Sensors

Regional bio-optical relationships and empirical algorithms were developed on the basis of measurements collected during the CoASTS 1995-2005 bio-optical time-series in the northern coastal Adriatic Sea as well as during ship campaigns performed in coastal regions of the Adriatic Sea, the Baltic Sea and the English Channel/North Sea between 2000 and 2005. The empirical algorithms aim at the retrieval from ocean colour data of the Chlorophyll a and Total Suspended Matter concentrations, of the absorption coefficient of the Coloured Dissolved Organic Matter, of the diffuse attenuation coefficient of downwelling irradiance and of the Secchi depth. Bio-optical relationships relating the marine optically significant components to their absorption or scattering properties are also presented for the investigated coastal areas.JRC.H.3-Global environement monitorin

Ancient DNA derived from alkenone-biosynthesizing haptophytes and other algae in Holocene sediments from the Black Sea

Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 21 (2006): PA1005, doi:10.1029/2005PA001188.Holocene sea surface temperatures (SST) of the Black Sea have been reconstructed using sedimentary C37 unsaturated alkenones assumed to be derived from the coccolithophorid haptophyte Emiliania huxleyi, whose fossil coccoliths are an important constituent of the unit I sediments. However, alkenones can also be biosynthesized by haptophyte species that do not produce microscopic recognizable coccoliths. A species-specific identification of haptophytes is important in such U 37 K′-based past SST reconstructions since different species have different alkenone-SST calibrations. We showed that 18S rDNA of E. huxleyi made up only a very small percentage (less than 0.8%) of the total eukaryotic 18S rDNA within the up to 3600-year-old fossil record obtained from the depocenter (>2000 m) of the Black Sea. The predominant fossil 18S rDNA was derived from dinoflagellates (Gymnodinium spp.), which are predominant members of the summer phytoplankton bloom in the modern Black Sea. Using a polymerase chain reaction/denaturing gradient gel electrophoresis method selective for haptophytes, we recovered substantial numbers of a preserved 458-base-pair (bp)-long 18S rDNA fragment of E. huxleyi from the Holocene Black Sea sediments. Additional fossil haptophyte sequences were not detected, indicating that the E. huxleyi alkenone-SST calibration can be applied for at least the last ∼3600 years. The ancient E. huxleyi DNA was well protected against degradation since the DNA/alkenone ratio did not significantly decrease throughout the whole sediment core and 20% of ∼2700-year-old fossil E. huxleyi DNA was still up to 23,000 base pairs long. We showed that fossil DNA offers great potential to study the Holocene paleoecology and paleoenvironment of anoxic deep-sea settings in unprecedented detail.This work was supported by a grant from the Netherlands Organization for Scientific Research (NWO) (Open Competition Program 813.13.001 to M.J.L.C.) and NSF grant OCE0117824 to S.G.W., which we greatly appreciate

Haslea silbo, a novel cosmopolitan species of blue diatoms

Specimens of a new species of blue diatoms from the genus Haslea Simonsen were discovered in geographically distant sampling sites, first in the Canary Archipelago, then North Carolina, Gulf of Naples, the Croatian South Adriatic Sea, and Turkish coast of the Eastern Mediterranean Sea. An exhaustive characterization of these specimens, using a combined morphological and genomic approach led to the conclusion that they belong to a single new to science cosmopolitan species, Haslea silbo sp. nov. A preliminary characterization of its blue pigment shows similarities to marennine produced by Haslea ostrearia, as evidenced by UV–visible spectrophotometry and Raman spectrome-try. Life cycle stages including auxosporulation were also observed, providing data on the cardinal points of this species. For the two most geographically distant populations (North Carolina and East Mediterranean), complete mitochondrial and plastid genomes were sequenced. The mitogenomes of both strains share a rare atp6 pseudogene, but the number, nature, and positions of the group II introns inside its cox1 gene differ between the two populations. There are also two pairs of genes fused in single ORFs. The plastid genomes are characterized by large regions of recombination with plasmid DNA, which are in both cases located between the ycf35 and psbA genes, but whose content differs between the strains. The two sequenced strains hosts three plasmids coding for putative serine recombinase protein whose sequences are compared, and four out of six of these plasmids were highly conserved

Denizel Fitoplanktonun Ekolojik Önemi ve Küresel İklim Değişikliğindeki Rolü

Bu derlemenin amacı bitkisel planktonun ekolojik önemini ve iklim değişikliğindeki rolünü incelemektir. Denizlerde besin zincirinin en alt halkasını oluşturan fitoplanktonun karbon üretimi dünya birincil üretiminin yarısını karşılamaktadır. Fitoplankton yeryüzündeki oksijenin de yarısını üretmektedir. Bu tek hücreli organizmalar küresel iklim değişikliğinde de rol oynamaktadır. İki farklı mekanizma ile fitoplanktonun küresel ısınmayı azaltabileceği önerilmiştir. Birincisinde bu fitoplankton atmosferden karbondioksiti alıp organik karbona çevirir ve ölen organizmalarla deniz tabanına gönderilir. Dolayısıyla atmosferdeki karbondioksit miktarı azalarak sera etkisi azaltılmış olur. İkinci mekanizma okyanuslarda yaygın olarak görülen bazı fitoplankton gruplarından çıkan dimetilsülfat gazı ile gerçekleşir. Bu gaz atmosferde sülfat aerosollerine yükseltgenerek bulut yoğunlaşma çekirdeği olarak görev yapar. Bulut oluşumu güneş ışınlarının yeryüzüne ulaşmasını engelleyeceği için bu gazın küresel bir soğumaya yol açabileceği belirtilmiştir. Biyosferdeki bitki kütlesinin sadece %0,2’sine karşılık gelen fakat tüm deniz canlılarının direk veya dolaylı olarak besin kaynağı olan fitoplanktonun çağın en büyük sorunlarından biri olan küresel ısınmayı etkileyebildiği düşünüldüğünde bu organizmaların ekosistemdeki yeri ve önemi daha iyi anlaşılmaktadır

Kuzeydoğu Akdenizde bilhassa atmosfer ile gelen besin elementlerinin fitoplankton (özellikle emiliania huxleyi dinamikleri üzerine etkisi.

Ph.D. - Doctoral Progra

New Record of a Dinoflagellate Species, Lessardia Elongata Saldarriaga et Taylor in the Black Sea

Lessardia elongata Saldarriaga et Taylor is identified for the first time in the northwestern Black Sea in the present study. This species has probably been recorded with different names in the Black Sea due to lack of detailed investigations with scanning electron microscopy (SEM) or fluorescence microscope. Our identification is based on observations with an electron microscope in September 2004 and with an epifluorescence and light microscope in June 2006. Cells were 5-10 µm wide, 22-30 µm long in formaldehyde fixed samples, fusiform, transparent, and had a faint broad girdle as described by Saldarriaga et al. (2003). Epitheca was slightly larger than the hypotheca and recently ingested prey could often be seen in the antapical half of the cell within very conspicuous vacuoles. Thin and faint thecal plates were hardly visible under epifluorescence microscope after staining the cells with fluorescence brightener 28 in the fixed samples. Cell abundances up to 18,400 cells L-1 and 87,000 cells L-1 were observed in September 2004 and June 2006, respectively.JRC.H.3-Global environement monitorin

Weekly Variations in Phytoplankton Structure of a Harbour in Mersin Bay north eastern Mediterranean

Weekly variations in the phytoplankton composition of a harbour in Mersin Bay were studied with two methods: filtration for the assessment of >55 μm phytoplankton from July 1995 to June 1997; and sedimentation for the assessment of all phytoplankton (both>55 μm and <55 μm) between 15 February and 25 May in 1996. With both sampling methods, a total of 175 phytoplankton species were identified. In the filtered samples, the total diatom abundance was much higher than that of dinoflagellates. The highest diatom abundance was detected on 8 February 1996 (11.7x103 cells 1-1) and 19 June 1997 (11.1x103 cells 1-1), represent mainly by the species Asterionella japonica Cleve and Rhizosolenia alata Brightwell respectively. The highest dinoflagellate abundance (737 cell 1-1) in the filtered samples occurred on 4 April 1996. However, on the following day a dinoflagellate (Prorocentrum micans Ehrenberg) bloom was found in great numbers (90.9x106 cells 1-1) in the sedimented samples. When this number was compared with the P. micans abundance of the previous day (3.1x106 cell 1-1) in the sedimented samples, the growth rate of this species was calculated as ~3.37 day-1. In this study, two techniques of phytoplanton analysis (sedimentation and filtration through a 55 μm mesh) were compared, the advantages and disadvantages of both methods were assessed, and it was concluded that both techniques should be applied during the process of phytoplankton enumeration. The contribution of small forms, mostly coccolithophorids and small flagellates (<20 μm), to the total phytoplankton abundance was found to be 37±21%

Distribution of phytoplankton in the southern Black Sea in summer 1996, spring and autumn 1998

The species composition, abundance, and biomass of micro- (>15 mum) and nano- (<15 mu m) phytoplankton were studied along the southern Black Sea during June-July 1996 and March-April and September 1998. A total of 150 species were identified, similar to 50% of them being dinoflagellates. The average total phytoplankton abundance changed from 77 x 10(3) Cells l(-1) in spring to 110 x 10(3) cells l(-1) in autumn and biomass from 250 mu g l(-1) in summer to 1370 mu g l(-1) in spring. Based on the extensive sampling grid from June-July 1996, phytoplankton seemed to have a rather homogeneous biomass distribution in the southern Black Sea. In all periods, the coccolithophorid Emiliania huxleyi was the most abundant species, its contribution to the total abundance ranging from 73% in autumn to 43% in spring. However, in terms of biomass, diatoms made up the bulk of phytoplankton in spring (97%, majority being Proboscia alata) and autumn (73%, majority being Pseudosolenia calcar-avis), and dinoflagellates in summer (74%, Gymnodinium sp.). There was a remarkable similarity in the dominant species between the western and eastern regions of the southern Black Sea, indicating transport of phytoplankton within the basin