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

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%

Role of Saharan Dust on Phytoplankton Dynamics in the Northeastern Mediterranean

Effects of atmospheric deposition and other environmental factors on phytoplankton dynamics were evaluated from an open (having offshore characteristics) and a coastal station in the northeastern Mediterranean between December 2000 and December 2001. Data on phytoplankton, chlorophyll a, nutrients, temperature and salinity were obtained at bi-weekly or more intense intervals during 1 yr, whilst transport of Saharan dust towards the sampling region was monitored daily by SeaWiFS (sea-viewing wide field-of-view sensor) images. Diatoms were the group of highest average biomass during the entire investigation period. Although coccolithophores (mainly Emiliania huxleyi) numerically dominated at the open station during the study period, their maximum abundance was as low as 50 × 103 cells. The intensity of dust transport was observed to be highest in spring. Less intense transports were observed in summer and autumn. Several intense episodic dry and wet dust deposition events during the spring season observed by SeaWiFS images caused little or no increase in phytoplankton abundance and biomass in the following days and weeks. Nevertheless, it appears that less intense dust transport events increased phytoplankton abundance and biomass in August, September and October 2001, when water column stratification was at its peak. However, these increases were much weaker than the major winter-early spring bloom (in February and March), which was caused by upwelling, mixing the water column. We suggest that the impact of atmospheric nutrient input on phytoplankton in the Mediterranean is rather low on a yearly basis.JRC.G.3-Agricultur

On the Performance of RIS-Assisted OFDM-IM: Impact of Hardware Impairments

Orthogonal frequency division multiplexing (OFDM) is frequently utilized as a modernist technique, while constructing new wireless applications. It has been adopted in many wireless communications standards. Moreover, index modulation (IM) techniques brought a new breath to OFDM thanks to their advantages of providing spectral/energy efficiency and hardware convenience. However, high carrier frequencies are used for the fifth generation and beyond (5GB) wireless systems, and thus, it can be difficult to completely suppress the unfavorable interference effects stemming from the hardware impairments (HWIs). Since the HWIs can significantly reduce the performance of the wireless systems, mitigating their destructive impacts should be one of the important issues to consider, while designing wireless communication systems. At this point, reconfigurable intelligent surfaces (RISs), which control the propagation environment by modifying radio waves, can be exploited to improve the signal quality. Considering that, this paper investigates the performance of an RIS-assisted OFDM-IM system under the effect of the HWIs by using a maximum likelihood (ML) detector as well as a log-likelihood ratio (LLR) detector. Computer simulation results are provided to illustrate the adverse effects of the HWIs on RIS-Assisted OFDM-IM system. It is observed that including an RIS into OFDM-IM systems provides considerable performance improvement

Reconfigurable Intelligent Surface-Assisted OFDM-IM for beyond 5G Mobile Networks: ML and LLR Detector Designs

The several countries of the world is intensified their investigative on the fifth generation and beyond (5GB) communications in order to reach the new requirements for new wireless applications. In this context, orthogonal frequency division multiplexing with index modulation (OFDM-IM) concept is suggested as one of the ideal solutions in the literature. Additionally, reconfigurable intelligent surfaces (RISs) can be occupied to enahance the quality of service (QoS). Considering that, the performance of RIS-assisted OFDM-IM system is examined by applying maximum likelihood (ML) and log-likelihood ratio (LLR) detectors in this paper. It is observed from the provided computer simulation results that integrating an RIS consisting of many low-cost and passive elements, into OFDM-IM systems considerably increase the overall system performance