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The effectiveness of an ultrasound transmitter (100 Watt) in preventing attachment and growth offouling organisms on submerged surfaces was tested in 2017 under realistic field conditions in thewestern Wadden Sea (Royal NIOZ harbor). Additionally, the possible synergetic effect of ultrasonicsound and an antifouling coating (Intersleek 1100SR, International, USA) was investigated.Three steel test plates were deployed. One control plate was attached to a steel seawall whicheffectively shielded the plate from ultrasonic sound (0% sound pressure). Two test plates wereattached to a floating dock with the ultrasound transmitter in between creating 25% sound pressureat the back and 100% sound pressure at the front of the plates. Proper operation of the ultrasoundtransmitter was confirmed by underwater sound level measurements at the test plate surfaces. Allplates were coated on each side in a 2x2 checkerboard pattern with antifouling coating and a regular(control) non‐ antifouling coating. During the two month deployment the plates were photographedregularly. At the end of the experiment the abundance and taxonomic composition of foulingcommunities in each quadrant was determined.It is concluded that Intersleek 1100SR had a distinct anti‐fouling effect. In addition, it is concludedthat the ultrasound exposure was not an effective anti‐fouling treatment, either alone or incombination with Intersleek anti‐fouling paint.

The oceans play a pivotal role in the global carbon cycle. It is not practical to measure the global daily production of organic carbon, the product of phytoplankton standing stock and its growth rate using discrete oceanographic methods. Instead, optical proxies from Earth-orbiting satellites must be used. To test the accuracy of optically derived proxies of phytoplankton physiology and growth rate, hyperspectral reflectance data from the wax and wane of a Phaeocystis bloom in laboratory mesocosms were compared with standard ex situ data. Chlorophyll biomass could be estimated accurately from reflectance using specific chlorophyll absorption algorithms. However, the conversion of chlorophyll (Chl) to carbon (C) was obscured by the non-linear increase in C : Chl under nutrient-limited growth. Although C : Chl was inversely correlated (r2 = 0.88) with the in situ fluorometric growth rate indicator Fv / Fm (Photosystem II quantum efficiency), none of them was linearly correlated to growth rate, constraining the accurate calculation of Phaeocystis growth or production rates. Unfortunately, the optical proxy ϕph (quantum efficiency of fluorescence: the ratio of the number of fluoresced photons to the number of photons absorbed by the phytoplankton) did not show any correlation with Phaeocystis growth rate, and therefore it is concluded that ϕph cannot be applied in the remotely sensed measurement of this species' carbon production rate.

International audience; Coastal and estuarine ecosystems are highly susceptible to crude oil pollution. Therefore, in order to examine the resilience of benthic phototrophs that are pivotal to coastal ecosystem functioning, we simulated an oil spill in tidal mesocosms consisting of intact sediment cores from a mudflat at the mouth of the Colne Estuary, UK. At day 21, fluorescence imaging revealed a bloom of cyanobacteria on the surface of oiled sediment cores, and the upper 1.5cm thick sediment had 7.2 times more cyanobacterial and 1.7 times more diatom rRNA sequences when treated with oil. Photosystem II operating efficiency (Fq′/Fm′) was significantly reduced in oiled sediments at day 7, implying that the initial diatom-dominated community was negatively affected by oil, but this was no longer apparent by day 21. Oil addition significantly reduced numbers of the key deposit feeders, and the decreased grazing pressure is likely to be a major factor in the increased abundance of both diatoms and cyanobacteria. By day 5 concentrations of dissolved inorganic nitrogen were significantly lower in oiled mesocosms, likely resulting in the observed increase in nifH-containing, and therefore potentially dinitrogen-fixing, cyanobacteria. Thus, indirect effects of oil, rather than direct inhibition, are primarily responsible for altering the microphytobenthos. © 2012 Society for Applied Microbiology and Blackwell Publishing Ltd.

Vogt, M. ... et. al.-- 14 pages, 9 figures, 4 tables, 1 appendix, The original and gridded data can be downloaded from PANGAEA: https://doi.org/10.1594/PANGAEA.779101, The planktonic haptophyte Phaeocystis has been suggested to play a fundamental role in the global biogeochemical cycling of carbon and sulphur, but little is known about its global biomass distribution. We have collected global microscopy data of the genus Phaeocystis and converted abundance data to carbon biomass using species-specific carbon conversion factors. Microscopic counts of single-celled and colonial Phaeocystis were obtained both through the mining of online databases and by accepting direct submissions (both published and unpublished) from Phaeocystis specialists. We recorded abundance data from a total of 1595 depth-resolved stations sampled between 1955–2009. The quality-controlled dataset includes 5057 counts of individual Phaeocystis cells resolved to species level and information regarding life-stages from 3526 samples. 83% of stations were located in the Northern Hemisphere while 17% were located in the Southern Hemisphere. Most data were located in the latitude range of 50–70º N. While the seasonal distribution of Northern Hemisphere data was well-balanced, Southern Hemisphere data was biased towards summer months. Mean species- and form-specific cell diameters were determined from previously published studies. Cell diameters were used to calculate the cellular biovolume of Phaeocystis cells, assuming spherical geometry. Cell biomass was calculated using a carbon conversion factor for prymnesiophytes. For colonies, the number of cells per colony was derived from the colony volume. Cell numbers were then converted to carbon concentrations. An estimation of colonial mucus carbon was included a posteriori, assuming a mean colony size for each species. Carbon content per cell ranged from 9 pg C cell−1 (single-celled Phaeocystis antarctica) to 29 pgC cell−1 (colonial Phaeocystis globosa). Non-zero Phaeocystis cell biomasses (without mucus carbon) range from 2.9 × 10−5 to 5.4 × 103 μg Cl−1, with a mean of 45.7 μg Cl−1 and a median of 3.0 μg Cl−1. The highest biomasses occur in the Southern Ocean below 70º S (up to 783.9 μg Cl−1) and in the North Atlantic around 50º N (up to 5.4 × 103 μg Cl−1). The original and gridded data can be downloaded from PANGAEA, doi:10.1594/PANGAEA.779101

Despite continuous efforts since the 1950s and more recent advances in culturing flagellates and nonflagellate cells of the prymnesiophyte Phaeocystis, a number of different life-cycle models exist today that appear to apply for P. globosa Scherff. and P. antarctica G. Karst., both spherical colony formers. In one such model, this life cycle consists of three different flagellates and one nonmotile cell stage that is embedded in carbohydrate matrix-forming colonies of different sizes and forms. Recently, noncolonial aggregates of diploid nonmotile cells attached to surfaces of diatoms were put forward as a new stage in the sexual life cycle of P. antarctica. However, it can be discussed that these attached aggregates (AAs) are an intermediate between motile diploid flagellates, with their well-known tendency to adhere to surfaces, and the young spherical colony with its diploid nonmotile cells, which in nature is commonly found attached to diatoms. A life-cycle model pertaining to both P. globosa and P. antarctica is presented.

International audience; The planktonic haptophyte Phaeocystis has been suggested to play a fundamental role in the global biogeochemical cycling of carbon and sulphur, but little is known about its global biomass distribution. We have collected global microscopy data of the genus Phaeocystis and converted abundance data to carbon biomass using species-specific carbon conversion factors. Microscopic counts of single-celled and colonial Phaeocystis were obtained both through the mining of online databases and by accepting direct submissions (both published and unpublished) from Phaeocystis specialists. We recorded abundance data from a total of 1595 depth-resolved stations sampled between 1955-2009. The quality-controlled dataset includes 5057 counts of individual Phaeocystis cells resolved to species level and information regarding life-stages from 3526 samples. 83% of stations were located in the Northern Hemisphere while 17% were located in the Southern Hemisphere. Most data were located in the latitude range of 50-70° N. While the seasonal distribution of Northern Hemisphere data was well-balanced, Southern Hemisphere data was biased towards summer months. Mean species- and form-specific cell diameters were determined from previously published studies. Cell diameters were used to calculate the cellular biovolume of Phaeocystis cells, assuming spherical geometry. Cell biomass was calculated using a carbon conversion factor for Prymnesiophytes (Menden-Deuer and Lessard, 2000). For colonies, the number of cells per colony was derived from the colony volume. Cell numbers were then converted to carbon concentrations. An estimation of colonial mucus carbon was included a posteriori, assuming a mean colony size for each species. Carbon content per cell ranged from 9 pg (single-celled Phaeocystis antarctica) to 29 pg (colonial Phaeocystis globosa). Non-zero Phaeocystis cell biomasses (without mucus carbon) range from 2.9 × 10-5 μg l-1 to 5.4 × 103 μg l-1, with a mean of 45.7 μg l-1 and a median of 3.0 μg l-1. Highest biomasses occur in the Southern Ocean below 70° S (up to 783.9 μg l-1), and in the North Atlantic around 50° N (up to 5.4 × 103 μg l-1). The original and gridded data can be downloaded from PANGAEA

The accuracy of remote sensing algorithms for phytoplankton biomass and physiology is difficult to test under natural conditions due to rapid changes in physical and biological forcings and the practical inability to manipulate nutrient conditions and phytoplankton composition in the sea. Therefore, an indoor mesocosm was designed to examine the optical properties of phytoplankton under controlled and manipulated conditions of irradiance, temperature, turbulence, and nutrient availability. Equipped with hyperspectral radiometers and bottom irradiance meters, it is shown that under semi-natural environmental conditions biogeochemically relevant species as Emiliania huxleyi and Phaeocystis globosa can be grown with good precision (± 20%) between duplicate mesocosms and between duplicate sensors (

The applicability of six fluorescent probes (four esterase probes: acetoxymethyl ester of Calcein [Calcein-AM], 5-chloromethylfluorescein diacetate [CMFDA], fluorescein diacetate [FDA], and 2',7'-dichlorofluorescein diacetate [H(2)DCFDA]; and two membrane probes: bis-(1,3-dibutylbarbituric acid) trimethine oxonol [DiBAC(4)(3)] and SYTOX-Green) as vitality stains was tested on live and killed cells of 40 phytoplankton strains in exponential and stationary growth phases, belonging to 12 classes and consisting of four cold-water, 26 temperate, and four warm-water species. The combined live/dead ratios of all six probes indicated significant differences between the 12 plankton classes (P < 0.01) and between individual species (P < 0.05). No specific differences were observed among strains of one species, among species or strains from different origin, nor between cells in exponential and stationary growth phase except for FDA. FDA showed a significant (P < 0.05) drop of

Een uitgebreide meetinspanning op de Noordzee, in combinatie met wiskundige en statistische modellering, laat zien dat de klimaatveranderingen in de vorm van een verandering in de overheersende windrichting, een toename van de windsnelheid, een toename van de zeewatertemperatuur, als wel als een toenemende CO2 concentratie van de atmosfeer, niet alleen leidt tot een verandering van de samenstelling van het zeewater in de vorm van bijvoorbeeld opgelost anorganisch koolstof en zuurgraad, maar ook tot een, zei het beperkte, verlaging van de productiviteit van op en in de zeebodem levende filterende organismen, die op hun beurt het voedsel zijn van bodembewonende vissen.

We are in a constant state of war, threatened by both exogenous enemies in the form of killing pathogens, or enemies from within in the form of tumor cells. The key for survival of our species amongst an overwhelming amount and diversity of microorganisms, such as viruses, bacteria and parasites is a well functioning immune system. Essential for the immune system to function properly is the ability to distinguish between foreign agents, malignant cells and the organism’s own healthy cells. The earliest written mention of immunity goes back to 430 BC during the plague of Athens when it was discovered that people who had recovered from the disease could nurse the sick without contracting the illness a second time (1). However, it was not until the 19th and 20th centuries before the concept developed into scientifi c theory. Two different types of immune responses can be distinguished that are referred to as the innate and the adaptive immune system. Usually, physical barriers prevent pathogens like bacteria and viruses from entering an organism, but if a pathogen breaches these barriers, the innate immune system provides an immediate albeit non-specifi c response. The innate immune system is thought to constitute an evolutionarily old defense strategy and is found in all plants and animals. Major functions of the vertebrate innate immune system include the identifi cation and removal of foreign substances, the activation of the complement cascade, recruitment of immune cells to sites of infection and activation of the adaptive immune system through antigen presentation (2,3).

International audience; The bacterial diversity of a chronically oil-polluted retention basin sediment located in the Berre lagoon (Etang-de-Berre, France) was investigated. This study combines chemical and molecular approaches in order to define how the in situ petroleum hydrocarbon contamination level affects the bacterial community structure of a subsurface sediment. Hydrocarbon content analysis clearly revealed a gradient of hydrocarbon contamination in both the water and the sediment following the basin periphery from the pollution input to the lagoon water. The nC17 and pristane concentrations suggested alkane biodegradation in the sediments. These results, combined with those of terminal-restriction fragment length polymorphism analysis of the 16S rRNA genes, indicated that bacterial community structure was obviously associated with the gradient of oil contamination. The analysis of bacterial community composition revealed dominance of bacteria related to the Proteobacteria phylum (Gamma-, Delta-, Alpha-, Epsilon- and Betaproteobacteria), Bacteroidetes and Verrucomicrobium groups and Spirochaetes, Actinobacteria and Cyanobacteria phyla. The adaptation of the bacterial community to oil contamination was not characterized by dominance of known oil-degrading bacteria, because a predominance of populations associated to the sulphur cycle was observed. The input station presented particular bacterial community composition associated with a low oil concentration in the sediment, indicating the adaptation of this community to the oil contamination. © 2008 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

To prevent flooding of the Dutch delta, former estuaries have been impounded by the building of dams and sluices. Some of these water bodies, however, experience major ecological problems. One of the problem areas is the former Volkerak estuary that was turned into a freshwater lake in 1987. From the early 1990s onward, toxic Microcystis blooms dominate the phytoplankton of the lake every summer. Two management strategies have been suggested to suppress these harmful algal blooms: flushing the lake with fresh water or reintroducing saline water into the lake. This study aims at an advance assessment of these strategies through the development of a mechanistic model of the population dynamics of Microcystis. To calibrate the model, we monitored the benthic and pelagic Microcystis populations in the lake during two years. Field samples of Microcystis were incubated in the laboratory to estimate growth and mortality rates as functions of light, temperature, and salinity. Recruitment and sedimentation rates were measured in the lake, using traps, to quantify benthic–pelagic coupling of the Microcystis populations. The model predicts that flushing with fresh water will suppress Microcystis blooms when the current flushing rate is sufficiently increased. Furthermore, the inlet of saline water will suppress Microcystis blooms for salinities exceeding 14 g/L. Both management options are technically feasible. Our study illustrates that quantitative ecological knowledge can be a helpful tool guiding large-scale water management.

Clonal cultures of Pseudo-nitzschia pungens were isolated at various times from seven sites in the North Sea. During the mitotic cell cycle, the two plate-shaped chloroplasts were girdle-appressed during interphase and mitosis. After cytokinesis, the chloroplasts moved onto the parental valve and remained there during the formation of the new hypovalve and until separation and re-arrangement of the sibling cells within the cell chain had been completed. Clones were almost always heterothallic and cultures of opposite mating type isolated from different localities were compatible. Meiosis I was cytokinetic and accompanied by chloroplast division. Meiosis II involved karyokinesis but not cytokinesis and preceded the rearrangement and contraction of the two gametes. Sexual reproduction involved physiological anisogamy. With one exception, gamete behaviour was clone-specific, gametes being active in clones of one mating type but passive in clones of the other mating type. Auxospore development was accompanied by deposition of a transverse and then a longitudinal perizonium. Infrequently, triploid auxospores and presumably haploid auxospores were produced. The four chloroplasts of diploid auxospores did not divide, and behaved synchronously during the two acytokinetic mitotic cycles accompanying the deposition of the initial thecae. Just before the first division of the initial cell, the chloroplasts shifted onto the valves ( two per valve). The division of the initial cell was not accompanied by chloroplast division and so the two daughter cells received two chloroplasts each. Two modes of abrupt cell size reduction were detected. One occurred during initial cell formation when part of the expanded auxospore aborted. The other pattern was more gradual and was observed in growing cultures; during successive cell divisions a frustule constriction appeared and intensified, one chloroplast split into two, and part of the protoplast aborted. A simple naming system is proposed for mating types in pennate diatoms.

Two cell types of the same clone of Phaeocystis globosa, solitary non-flagellate cells and flagellates, were grown in batch cultures under identical conditions. The non-flagellate cells had a shorter lag phase (1.4 versus 2.8 days) and a higher growth rate (0.72 versus 0.65 day(-1)) than flagellate cells. The flagellates had a longer stationary phase (15.6 versus 9.5 days) and a lower death rate (0.07 versus 0.52 day(-1)) than non-flagellate cells. All differences were statistically significant. Biomass yield did not differ between the two cell types. The short lag phase and high growth rate of non-flagellate cells corresponds to field observations of rapidly developing non-flagellate Phaeocystis blooms that are typically observed in nutrient-rich environments such as temperate seas in spring. The flagellate cell type, with its longer stationary phase and lower death rate than non-flagellate cells, is better equipped for survival in oligotrophic environments. This explains why the flagellates of Phaeocystis are abundant after the spring phytoplankton bloom in temperate seas and in other nutrient-poor environments such as the open ocean.