Invasive species in the Northeastern and Southwestern Atlantic Ocean: A review

The spread of non-native species has been a subject of increasing concern since the 1980s when human-mediated transportation, mainly related to ships' ballast water, was recognized as a major vector for species transportation and spread, although records of non-native species go back as far as 16th Century. Ever increasing world trade and the resulting rise in shipping have highlighted the issue, demanding a response from the international community to the threat of non-native marine species. In the present study, we searched for available literature and databases on shipping and invasive species in the North-eastern (NE) and South-western (SW) Atlantic Ocean and assess the risk represented by the shipping trade between these two regions. There are reports of 44 species associated with high impacts for the NE Atlantic and 15 for the SW Atlantic, although this may be an underestimate. Vectors most cited are ballast water and biofouling for both regions while aquaculture has also been a very significant pathway of introduction and spread of invasive species in the NE Atlantic. Although the two regions have significant shipping traffic, no exchange of invasive species could be directly associated to the shipping between the two regions. However, it seems prudent to bring the exchange of ballast water between the two regions under control as soon as possible

Diplomado de profundización cisco prueba de habilidades prácticas CCNP

Como parte fundamental del diplomado CISCO CCNP, tenemos como objetivo para este estudio es determinar la configuración de plataformas de Conmutación basadas en Switch, mediante el uso de protocolos como STP y la configuración de Vlan en escenarios de red corporativos, para comprender el modo de operación de las subredes y los beneficios de administrar dominios de broadcast independientes, esto para múltiples escenarios al interior de una red jerárquica convergente, que se aplica para la Electrónica de Red, la cual es la parte de la infraestructura que nos permite interconectar ordenadores y periféricos utilizando principalmente dos tipos de equipos: Routers y Switches. Para alcanzar el aprendizaje de enrutamiento usaremos los comandos IOS de configuración avanzada en routers (con direccionamiento IPv4 e IPv6) para protocolos de Enrutamiento como: OSPF, EIGRP y BGP, en entornos de direccionamiento sin clase, con el fin diseñar e implementar soluciones de red escalables, mediante el uso de los principios de enrutamiento y conmutación de paquetes en ambientes para Redes LAN y WAN.As a fundamental part of the CISCO CCNP diplomat, our objective for this study is to determine the configuration of Switch-based Switching platforms, through the use of protocols such as STP and the configuration of VLANs in corporate Networking scenarios, to understand the mode of operation of the subnets and the benefits of managing independent broadcast domains, this for multiple scenarios within a convergent hierarchical network, which is applied to network Electronics, which is the part of the infrastructure that allows us to interconnect computers and peripherals using mainly two types of equipment: Routers and Switch. To achieve the routing learning, we will use the advanced configuration IOS commands in routers (with IPv4 and IPv6 addressing) for routing protocols such as: OSPF, EIGRP and BGP, in classless addressing environments, to design and implement network solutions scalable, using the principles of Routing and packet switching in LAN and WAN environments

Collaborative Deep Learning Models to Handle Class Imbalance in FlowCam Plankton Imagery

Usingautomatedimagingtechnologies,itisnowpossibletogeneratepreviouslyunprecedented volumes of plankton image data which can be used to study the composition of plankton assemblages. However, the current need to manually classify individual images introduces a bottleneck into processing chains.AlthoughMachineLearningtechniqueshavebeenusedtotryandaddressthisissue,pasteffortshave suffered from accuracy limitations, especially in minority classes. Here we use state-of-the-art methods in Deep Learning to investigate suitable architectures for training an automated plankton classification system which achieves high efficacy for both abundant and rare taxa. We collected live plankton from Station L4 in the Western English Channel and imaged 11,371 particles covering 104 taxonomic groups using the automatedplanktonimagingsystemFlowCam.Theimagesetcontainedasevereclassimbalance,withsome taxa represented by > 600 images while other, rarer taxa were represented by just 14. We demonstrate that by allowing multiple Deep Learning models to collaborate in a single classification system, classification accuracyimprovesforminorityclasseswhencomparedwiththebestindividualmodel.Thetopcollaborative model achieved a 6 % improvement in F1 accuracy over the best individual model, while overall accuracy improved by 3.2 %. This resulted in a 97.4 % overall accuracy score and a 96.2 % F1 macro score on a separate holdout test set containing 104 taxonomic groups. Based on a survey of similar studies in the literature, we believe collaborative deep learning models can significantly improve the accuracy of existing automated plankton classification systems

Microbial plankton communities in the coastal southeastern Black Sea: Biomass, composition and trophic interactions

We investigated biomass and composition of the pico-, nano- and microplankton communities in a coastal station of the southeastern Black Sea during 2011. We also examined trophic interactions within these communities from size-fractionated dilution experiments in February, June and December. Autotrophic and heterotrophic biomasses showed similar seasonal trends, with a peak in June, but heterotrophs dominated throughout the year. Autotrophic biomass was mainly comprised by nanoflagellates and diatoms in the first half of the year, and by dinoflagellates and Synechococcus spp. in the second half. Heterotrophic biomass was mostly dominated by heterotrophic bacteria, followed by nanoflagellates and microzooplankton. Dilution experiments suggest that nano- and microzooplankton were significant consumers of autotrophs and heterotrophic bacteria. More than 100% of bacterial production was consumed by grazers in all experiments, while 46%, 21% and 30% of daily primary production were consumed in February, June and December, respectively. In February, autotrophs were the main carbon source, but in December, it was heterotrophic bacteria. An intermediate situation was observed in June, with similar carbon flows from autotrophs and heterotrophic bacteria. Size-fraction dilution experiments suggested that heterotrophic nanoflagellates are an important link between the high heterotrophic bacterial biomass and microzooplankton. In summary, these results indicate that nano- and microzooplankton were responsible for comprising a significant fraction of total microbial plankton biomass, standing stocks, growth and grazing processes. This suggests that in 2011, the microbial food web was an important compartment of the planktonic food web in the coastal southeastern Black Sea

Microplastics alter feeding selectivity and faecal density in the copepod, Calanus helgolandicus

Microplastics (1 μm–5 mm) are a ubiquitous marine contaminant of global concern, ingested by a wide range of marine taxa. Copepods are a key component of marine food webs, providing a source of food for higher trophic levels, and playing an important role in marine nutrient cycling. Microplastic ingestion has been documented in copepods, but knowledge gaps remain over how this affects feeding preference and faecal density. Here, we use exposure studies incorporating algal prey and microplastics of varying sizes and shapes at a concentration of 100 microplastics mL−1 to show: (1) prey selection by the copepod Calanus helgolandicus was affected by the size and shape of microplastics and algae they were exposed to; Exposure to nylon fibres resulted in a 6% decrease in ingestion of similar shaped chain-forming algae, whilst exposure to nylon fragments led to an 8% decrease in ingestion of a unicellular algae that were similar in shape and size. (2) Ingestion of microplastics with different densities altered the sinking rates of faecal pellets. Faeces containing low-density polyethylene sank significantly more slowly than controls, whilst sinking rates increased when faeces contained high-density polyethylene terephthalate. These results suggest that C. helgolandicus avoid ingesting algae that are similar in size and/or shape to the microplastic particles they are exposed to, potentially in a bid to avoid consuming the plastic

Microplastic Ingestion by Zooplankton

Small plastic detritus, termed “microplastics”, are a widespread and ubiquitous contaminant of marine ecosystems across the globe. Ingestion of microplastics by marine biota, including mussels, worms, fish, and seabirds, has been widely reported, but despite their vital ecological role in marine food-webs, the impact of microplastics on zooplankton remains under-researched. Here, we show that microplastics are ingested by, and may impact upon, zooplankton. We used bioimaging techniques to document ingestion, egestion, and adherence of microplastics in a range of zooplankton common to the northeast Atlantic, and employed feeding rate studies to determine the impact of plastic detritus on algal ingestion rates in copepods. Using fluorescence and coherent anti-Stokes Raman scattering (CARS) microscopy we identified that thirteen zooplankton taxa had the capacity to ingest 1.7–30.6 μm polystyrene beads, with uptake varying by taxa, life-stage and bead-size. Post-ingestion, copepods egested faecal pellets laden with microplastics. We further observed microplastics adhered to the external carapace and appendages of exposed zooplankton. Exposure of the copepod Centropages typicus to natural assemblages of algae with and without microplastics showed that 7.3 μm microplastics (>4000 mL–1) significantly decreased algal feeding. Our findings imply that marine microplastic debris can negatively impact upon zooplankton function and health

Distribution, sedimentation and fate of pigment biomarkers following thermal stratification in the western Alboran Sea

A spring investigation of the phytoplankton in the western Alboran Sea (Mediterranean) was undertaken using chlorophyll and carotenoid biomarkers to characterize the community in the water column and in drifting sediment traps set at 100 and 200 m. During 2 drifter experiments, calm and sunny conditions induced a progressive thermal stratification that reduced pigment sedimentation into deeper water and confined the phytoplankton to the surface layer, resulting in an increase in chlorophyll biomass. 19'-Hexanoyloxyfucoxanthin (prymnesiophytes) and chlorophyll b (chlorophytes, prasinophytes, prochlorophytes) were the major accessory pigments, while fucoxanthin, alloxanthin and peridinin indicated the presence of diatoms, cryptophytes and dinoflagellates, respectively. The proportional contribution of each algal group to the chlorophyll a (chl a) biomass, as derived from multiple regression analysis, revealed that prymnesiophytes, cryptophytes and the green algal group collectively accounted for at least 75% in the upper 100 m, emphasizing the importance of the nanophytoplankton. Phaeopigments, dominated by phaeophorbide a2, were the main pigments observed in sediment traps, although chl a, fucoxanthin and 19'-hexanoyloxyfucoxanthin were detected in smaller concentrations as well as traces of chlorophyll b (chl b). In deep water, fucoxanthin and 19'-hexanoyloxyfucoxanthin were the only accessory pigments present while total phaeopigment/chl a molar ratios >1 reflected the active transformation of fine phytogenic material at depth. High particulate organic carbon (POC)/chl a ratios (>100 in surface water; >1000 in deep water) suggested that phytoplankton was a relatively small component of the total carbon biomass down the water column. Using simple budget calculations, we determined that 58 to 65% of the chl a produced in the upper 100 m accumulated in the water column over both experiments. During Expt 1, 29% of the chl a sedimented out, mostly as phaeopigment, at 100 m (24%), and 6% was degraded to colourless residues in the water column. In contrast, only 12% of the chl a sedimented in Expt 2, while 20% was degraded to colourless residues

Smells good enough to eat: Dimethyl sulfide (DMS) enhances copepod ingestion of microplastics

Marine copepods have been shown to readily ingest microplastics - a crucial first step in the transfer of plastics into the marine food chain. Copepods have also been shown to elicit a foraging behavioural response to the presence of olfactory stimuli, such as dimethyl sulfide (DMS) – a volatile compound produced by their algal prey. Here, we show that the temperate Calanoid copepod Calanus helgolandicus displays enhanced grazing rates of between 0.7 and 3-fold (72%–292%) on microplastics that have been infused in a DMS solution, compared to DMS-free controls. Environmental exposure of microplastics may result in the development of an olfactory signature that includes algal-derived compounds such as DMS. Our study provides evidence that copepods, which are known to use chemosensory mechanisms to identify and locate dense sources of palatable prey, may be at an increased risk of plastic ingestion if it mimics the scent of their prey

High prey-predator size ratios and unselective feeding in copepods: A seasonal comparison of five species with contrasting feeding modes

There has been an upsurge of interest in trait-based approaches to zooplankton, modelling the seasonal changes in the feeding modes of zooplankton in relation to phytoplankton traits such as size or motility. We examined this link at two English Channel plankton monitoring sites south of Plymouth (L4 and E1). At L4 there was a general transition from diatoms in spring to motile microplankton in summer and autumn, but this was not mirrored in the succession of copepod feeding traits; for example the ambushing Oithona similis dominated during the spring diatom bloom. At nearby E1 we measured seasonality of food and grazers, finding strong variation between 2014 and 2015 but overall low mesozooplankton biomass (median 4.5 mg C m−3). We also made a seasonal grazing study of five copepods with contrasting feeding modes (Calanus helgolandicus, Centropages typicus, Acartia clausi, Pseudocalanus elongatus and Oithona similis), counting the larger prey items from the natural seston. All species of copepod fed on all food types and differences between their diets were only subtle; the overriding driver of diet was the composition of the prey field. Even the smaller copepods fed on copepod nauplii at significant rates, supporting previous suggestions of the importance of intra-guild predation. All copepods, including O. similis, were capable of tackling extremely long (> 500 μm) diatom chains at clearance rates comparable to those on ciliates. Maximum observed prey:predator length ratios ranged from 0.12 (C. helgolandicus) up to 0.52 (O. similis). Unselective feeding behaviour and the ability to remove highly elongated cells have implications for how copepod feeding is represented in ecological and biogeochemical models

Seasonal variation of zooplankton community structure and trophic position in the Celtic Sea: A stable isotope and biovolume spectrum approach

Zooplankton on continental shelves represent an important intermediary in the transfer of energy and matter from phytoplankton to the wider ecosystem. Their taxonomic composition and trophic interactions with phytoplanktonvaryinspaceandtime, andinterpreting theimplicationsofthis constantlyevolvinglandscaperemainsamajorchallenge.Herewecombineplanktontaxonomicdatawiththeanalysisofbiovolumespectraand stableisotopestoprovideinsightsintothetrophicinteractionsthatoccurinashelfseaecosystem(CelticSea) across the spring-summer-autumn transition. Biovolume spectra captured the seasonal development of the zooplankton community well, both in terms of total biomass and trophic positioning, and matched trophic positionsestimatedbystableisotopeanalysis.InearlyApril,largemicroplankton(63–200µm)occupiedhigher trophic positions than mesozooplankton (>200µm), likely reflecting the predominance of nanoplankton (2–20µm) that were not readily available to mesozooplanktongrazers. Biomass and number of trophic levels increasedduringthespringbloomaselevatedprimaryproductionallowedforahigherabundanceofpredatory species.DuringJuly,theplanktonassemblageoccupiedrelativelyhightrophicpositions,indicatingimportant links to the microbial loop and the recycling of organic matter. The strong correlation between biomass and communitytrophiclevelacrossthestudysuggeststhattheCelticSeaisarelativelyenclosedandpredominantly energy-limited ecosystem. The progression of the zooplankton biomass and community structure within the centralshelfregionwasdifferenttothatattheshelf-break,potentiallyreflectingincreasedpredatorycontrolof copepodsby macrozooplanktonandpelagicfishesattheshelfbreak.Wesuggestthatthecombinationofsize spectra and stable isotope techniques are highly complementary and useful for interpreting the seasonal progressionoftrophicinteractionsintheplankton