Effect of Grazing-Mediated Dimethyl Sulfide (DMS) Production on the Swimming Behavior of the Copepod Calanus helgolandicus

Chemical interactions play a fundamental role in the ecology of marine foodwebs. Dimethyl sulfide (DMS) is a ubiquitous marine trace gas that acts as a bioactive compound by eliciting foraging behavior in a range of marine taxa including the copepod Temora longicornis. Production of DMS can rapidly increase following microzooplankton grazing on phytoplankton. Here, we investigated whether grazing-induced DMS elicits an increase in foraging behavior in the copepod Calanus helgolandicus. We developed a semi-Automated method to quantify the effect of grazing-mediated DMS on the proportion of the time budget tethered females allocate towards slow swimming, typically associated with feeding. The pooled data showed no differences in the proportion of the 25 min time budget allocated towards slow swimming between high (23.6 ± 9.74%) and low (29.1 ± 18.33%) DMS treatments. However, there was a high degree of variability between behavioral responses of individual copepods. We discuss the need for more detailed species-specific studies of individual level responses of copepods to chemical signals at different spatial scales to improve our understanding of chemical interactions between copepods and their prey. © 1996-2013 MDPI AG

Targeted-metabolomics Of Phytoplankton Blooms In The Gulf of Naples And Effects Of Algal Oxylipins On The Reproduction And Gene Expression Of The Copepod <i>Temora stylifera</i>

Diatoms, dominant phytoplankton in the world’s ocean, synthesize a large number of oxylipins, fatty-acid-derived bioactive metabolites that impair cell proliferation. Oxylipins were originally proposed as defensive molecules hindering the reproductive success of grazer copepods through a maternal effect. In the present thesis, a targeted-metabolomics approach was applied to quantify six non-volatile oxylipins and the fatty acids from surface phytoplankton collected in the Gulf of Naples (Italy) along the year 2017. Potential effects of biotic and abiotic factors on the population dynamics of Temora stylifera (a dominating copepod species in the sampling area) were analysed in terms of reproductive potential and molecular responses of wild copepods captured in the sampling year. A de novo transcriptomic approach allowed comparing the transcriptional profiling of adult females at high and low naupliar survival rates. Expression of 13 sequences selected after the RNA-Seq analysis was quantified through RT-qPCR in wild copepod females along 2017. In the laboratory, physiological and molecular responses of T. stylifera females were analysed after feeding on four diatom mono-algal diets isolated from the Gulf of Naples and characterized in terms of oxylipin synthesis potential and nutritional value. Overall, the results shed more light on plankton ecology and in particular on diatom-copepod interactions. A potential role of oxylipins as signalling molecules in natural diatom communities is proposed and discussed, opening new scenarios in diatom chemical ecology studies. No clear effects of NVOs on the reproductive potential and the molecular responses of wild T. stylifera females were detected. A delayed negative effect of Chaetoceros (one of the most abundant diatom genera in the Gulf of Napels) on naupliar survival rates was observed, partially explaining the maximum population density of T. stylifera occurring in autumn. Transcriptional profiling suggested a gene regulation possibly aimed at maximizing the reproductive success of the copepod. The genes ATP-Dependent RNA Helicase (me31b), Very Low-Density Lipoprotein Receptor (VLDLR) and cAMP-Responsive Element-Binding Protein (CREBL) were significantly related to egg production and could constitute sentinel sequences to estimate the reproductive potential of wild copepods in subsequent field surveys. Laboratory experiments suggested different physiological and molecular responses of T. stylifera females to the four diatoms, possibly indicating gene expression modulation in response to different chemical signatures of the diets

Trophic Relationships and Food Supply of Heterotrophic Animals in the Pelagic Ecosystem of the Black Sea

During recent decades, the Black Sea has been affected by many negative factors that strongly changed the condition of its ecosystem. Especially trophic relationships in the Black Sea pelagic system became very vulnerable influencing the food supply, productivity and abundance of many species and populations of this marine basin. Food is one of most important link between biota and its environment. In this monograph, the role and variability of trophodynamic processes that effect the well-being (health) of main heterotrophic components of ecosystem were analysed in detail for a few key species as indicators for estimation of ecosystem condition in whole. These are most significant mass species of the Black Sea pelagic ecosystem. Among copepods this is Calanus euxinus that dominates the mesozooplankton which makes up the fodder base of planktivorous fishes. Among gelatinous these are medusa Aurelia aurita and the alien ctenophores Mnemiopsis leidyi and Beroe ovata which affected strongly mesozooplankton composition. Lastly among fishes the anchovy Engraulis encrasicolus ponticus and sprat Sprattus sprattus phalericus that dominate small pelagic fishery. We considered in this monograph: • Diel feeding behaviour, in situ feeding rate of Calanus euxinus and impact of mesozooplankton on primary production and phytoplankton biomass. • The effect of vertical migrations on energy budget and its components in C. euxinus; metabolic substrates used in catabolic processes under both aerobic and hypoxic conditions, the role of reserve lipids and effect of abiotic factors on individual growth and population structure of this species. • The intensity and efficiency of ingestion and energy transformation in three gelatinous species ( jellyfish Aurelia aurita, ctenophores Mnemiopsis leidyi and Beroe ovata) and their predatory impact on zooplankton community. • Nutritional condition and food supply of anchovy and sprat in the close interaction with natural biotic and abiotic and anthropogenic factors. • Tendencies in this interaction during long time space: since 1960 s till present years. • Estimation of population condition of these species and its long-term change. This monograph is the collective work of Ukrainian and Turkish scientists studying complex hydrobiological problems of the Black Sea. Its aim is to reveal the significance of nutritional factors on the ecology of Black Sea biota, including changes which have already occurred, as well as offering some insight into changes that may happen in the future. Our joint investigations started in the first half of the 1990s, when conditions for the close cooperation of researchers from the two countries were suitable after the collapse of the Soviet era. This spirit continues to the present day. Professor Ümit Unluata, Director of Erdemli Institute of Marine Sciences (Middle East Technical University, Ankara) was of paramount importance in organising and fostering the work undertaken. We would like to devote this monograph to the memory of him, who died so prematurely. We are also grateful to Academician Professor V. N. Eremeev, Director of the Sevastopol Institute of Biology of the Southern Sea (National Academy of Sciences of Ukraine), and to the directors of Erdemli Institute of Marine Sciences (Professor Ilkay Salihoglu, Professor Sukru Besiktepe and Professor Ferit Bingel) who also made significant contributions to the Ukrainian–Turkish collaboration. We are grateful to Dr Bill Parr from the Black Sea Ecosystem Recovery Project for his valuable efforts in improving earlier drafts. All these investigations were carried out within the framework of the following five NATO linkage-grants: • Pelagic animal food supply in the unstable Black Sea environment, • Will the new alien ctenophore Beroe ovata control the plankton community in the Black Sea? • Grazing, growth and production of Calanus euxinus in the Black Sea, • Bioindicators for assessment of Black Sea ecosystem recovery, • Adaptability and vulnerability of marine species in changing environments. And four TUBITAK - NASU joint projects: • Quantification of the recent ctenophore invader Beroe ovata impact in the Black Sea • Monitoring of the Black Sea anchovy and sprat, • Salinity tolerance as a key factor of invasion success of the copepods of Calanus genus into the Sea of Marmara, • Salinity tolerance as a key factor of invasion success of the mesozooplankton species into the Sea of Marmara. We hope that this publication will make a substantial contribution to future studies of the Black Sea ecosystem and offers further understanding of those features regulating biological processes in this unique marine basin

Why do coccolithophores calcify? Does the calcium carbonate shell serve as protection against viral infection and predation?

Coccolithophores are an important group of marine phytoplankton that are characterized by their ability to precipitate calcium carbonate. The single cells form small calcite plates (coccoliths), which are arranged on the cell surface in form of a spherical coating, called coccosphere. Coccolithophores account for a significant proportion of the marine primary production and are among the most important calcifying organisms in the ocean, thus having a significant impact on the marine carbon cycle. However, it is not known in what way their ability to calcify contributes to their ecological success, as the question of why coccolithophores calcify remains unanswered. Probably the most obvious theory is that the coccosphere provides protection against natural predators, the most relevant of which are viruses, microzooplankton (unicellular protists), and mesozooplankton (metazoan predators). By means of laboratory experiments, this work investigated whether the coccosphere of certain species provides protection against infection with a virus, a phagotrophic protozoan, and a copepod. The results show that the coccosphere does not prevent infection with the specific virus and reveal complex infection dynamics in the investigated host-virus system. It is further shown that the coccosphere does not protect against grazing by a certain copepod species. Experiments with a phagotrophic protozoan showed that the coccosphere affects food uptake and growth of the predator, but does not cause the grazer to avoid ingesting coccolithophores and to select non-calcified cells that were offered at the same time. The results raise the questions whether other microzooplankton predators that naturally co-occur with coccolithophores are able to select against calcifying cells, and whether the effect of calcification on the growth of nonselective protozoa provides a benefit for coccolithophores

Why do coccolithophores calcify? Does the calcium carbonate shell serve as protection against viral infection and predation?

Coccolithophores are an important group of marine phytoplankton that are characterized by their ability to precipitate calcium carbonate. The single cells form small calcite plates (coccoliths), which are arranged on the cell surface in form of a spherical coating, called coccosphere. Coccolithophores account for a significant proportion of the marine primary production and are among the most important calcifying organisms in the ocean, thus having a significant impact on the marine carbon cycle. However, it is not known in what way their ability to calcify contributes to their ecological success, as the question of why coccolithophores calcify remains unanswered. Probably the most obvious theory is that the coccosphere provides protection against natural predators, the most relevant of which are viruses, microzooplankton (unicellular protists), and mesozooplankton (metazoan predators). By means of laboratory experiments, this work investigated whether the coccosphere of certain species provides protection against infection with a virus, a phagotrophic protozoan, and a copepod. The results show that the coccosphere does not prevent infection with the specific virus and reveal complex infection dynamics in the investigated host-virus system. It is further shown that the coccosphere does not protect against grazing by a certain copepod species. Experiments with a phagotrophic protozoan showed that the coccosphere affects food uptake and growth of the predator, but does not cause the grazer to avoid ingesting coccolithophores and to select non-calcified cells that were offered at the same time. The results raise the questions whether other microzooplankton predators that naturally co-occur with coccolithophores are able to select against calcifying cells, and whether the effect of calcification on the growth of nonselective protozoa provides a benefit for coccolithophores

The Effects of Food Quality and Temperature on Mesozooplankton Physiology

This study assesses the physiological responses of copepods to variations in the quality of their diet and temperature and explores the variability of food quality in the field. Laboratory experiments were used to constrain the effects of food quality in terms of phytoplankton organic ratios N:P, C:N and C:P and fatty acid content, on Temora longicornis feeding, respiration, and egg production rates (EPR). Maximum metabolic rates, assimilation efficiency and gross growth efficiency coincided with an optimum diet of ~16N:1P defining it as the copepod threshold nutrient ratio. In the field, a response of zooplankton biomass to temporal variations in seston N:P ratio was found in the North Sea and in the North Pacific Subtropical Gyre. Field measurements revealed latitudinal and temporal changes in food quality at the chlorophyll maximum along an Atlantic Meridional Transect (AMT). Better quality food was found in the Temperate and Upwelling domains and included seston with lower C:N ratios, N:P ratios closer to Redfield values and a higher proportion of polyunsaturated fatty acids (PUFA), essential fatty acids such as 20:5(n-3) and 22:6(n-3), high (n-3):(n-6) ratios and lower proportion of saturated fatty acids (SAFA). Time-series data showed that food quantity and quality declined over time in the temperate North region of the Atlantic Ocean. Ship-board experiments were undertaken to determine the effects of temperature on respiration and EPR of some mesopelagic copepod species along an AMT. 75-85% of the variation in routine metabolic rates was explained by allometric and thermodynamic relationships. Within the range of temperatures measured, estimates of Ea (activation energy) and Q10 suggested high sensitivity to temperature variation. Our results highlight the importance of quantifying the effects of a variety of ecological parameters on the physiological responses of copepods to understand the processes that regulate zooplankton dynamics and their effects on biogeochemical cycles and trophic transfer of energy

Mophological defence of planktonic protists against predation.

Department of BotanyKatedra botanikyPřírodovědecká fakultaFaculty of Scienc

YOUMARES 8 – Oceans Across Boundaries: Learning from each other

This open access book presents the proceedings volume of the YOUMARES 8 conference, which took place in Kiel, Germany, in September 2017, supported by the German Association for Marine Sciences (DGM). The YOUMARES conference series is entirely bottom-up organized by and for YOUng MARine RESearchers. Qualified early career scientists moderated the scientific sessions during the conference and provided literature reviews on aspects of their research field. These reviews and the presenters’ conference abstracts are compiled here. Thus, this book discusses highly topical fields of marine research and aims to act as a source of knowledge and inspiration for further reading and research