Distinctive diffusive properties of swimming planktonic copepods in different environmental conditions

Suspensions of small planktonic copepods represent a special category in the realm of active matter, as their size falls within the range of colloids, while their motion is so complex that it cannot be rationalized according to basic models of self-propelled particles. Indeed, the wide range of individual variability and swimming patterns resemble the behaviour of much larger animals. By analysing hundreds of three-dimensional trajectories of the planktonic copepod Clausocalanus furcatus, we investigate the possibility of detecting how the motion of this species is affected by different external conditions, such as the presence of food and the effect of gravity. While this goal is hardly achievable by direct inspection of single organism trajectories, we show that this is possible by focussing on simple average metrics commonly used to characterize colloidal suspensions, such as the mean square displacement and the dynamic correlation functions. We find that the presence of food leads to the onset of a clear localization that separates a short-time ballistic from a long-time diffusive regime. Such a benchmark reflects the tendency of C. furcatus to remain temporally feeding in a limited space and disappears when food is absent. Localization is clearly evident in the horizontal plane, but is negligible in the vertical direction, due to the effect of gravity. Our results suggest that simple average descriptors may provide concise and useful information on the swimming properties of planktonic copepods, even though single organism behaviour is strongly heterogeneous

Plankton food-webs: to what extent can they be simplified?

Plankton is a hugely diverse community including both unicellular and multicellular organisms, whose individual dimensions span over seven orders of magnitude. Plankton is a fundamental part of biogeochemical cycles and food-webs in aquatic systems. While knowledge has progressively accumulated at the level of single species and single trophic processes, the overwhelming biological diversity of plankton interactions is insufficiently known and a coherent and unifying trophic framework is virtually lacking. We performed an extensive review of the plankton literature to provide a compilation of data suitable for implementing food-web models including plankton trophic processes at high taxonomic resolution. We identified the components of the plankton community at the Long Term Ecological Research Station MareChiara in the Gulf of Naples. These components represented the sixty-three nodes of a plankton food-web. To each node we attributed biomass and vital rates, i.e. production, consumption, assimilation rates and ratio between autotrophy and heterotrophy in mixotrophic protists. Biomasses and rates values were defined for two opposite system's conditions; relatively eutrophic and oligotrophic states. We finally identified 817 possible trophic links within the web and provided each of them with a relative weight, in order to define a diet-matrix, valid for both trophic states, which included all consumers, fromn anoflagellates to carnivorous plankton. Vital rates for plankton resulted, as expected, very wide; this strongly contrasts with the narrow ranges considered in plankton system models implemented so far. Moreover, the amount and variety of trophic links highlighted by our review is largely excluded by state-of-the-art biogeochemical and food-web models for aquatic systems. Plankton models could potentially benefit from the integration of the trophic diversity outlined in this paper: first, by using more realistic rates; second, by better defining trophic roles of consumers in the planktonic web. We suggest that most trophic habits present in planktonic organisms must be contemplated in new generation plankton models.</p

Time series and beyond: multifaceted plankton research at a marine Mediterranean LTER site

Plankton are a pivotal component of the diversity and functioning of coastal marine ecosystems. A long time-series of observations is the best tool to trace their patterns and variability over multiple scales, ultimately providing a sound foundation for assessing, modelling and predicting the effects of anthropogenic and natural environmental changes on pelagic communities. At the same time, a long time-series constitutes a formidable asset for different kinds of research on specific questions that emerge from the observations, whereby the results of these complementary studies provide precious interpretative tools that augment the informative value of the data collected. In this paper, we review more than 140 studies that have been developed around a Mediterranean plankton time series gathered in the Gulf of Naples at the station LTER-MC since 1984. These studies have addressed different topics concerning marine plankton, which have included: i) seasonal patterns and trends; ii) taxonomic diversity, with a focus on key or harmful algal species and the discovery of many new taxa; iii) molecular diversity of selected species, groups of species or the whole planktonic community; iv) life cycles of several phyto- and zooplankton species; and v) interactions among species through trophic relationships, parasites and viruses. Overall, the products of this research demonstrate the great value of time series besides the record of fluctuations and trends, and highlight their primary role in the development of the scientific knowledge of plankton much beyond the local scale

Campagna oceanografica Anomcity_2016

Le attività scientifiche realizzate nell’ambito di questa campagna si inseriscono all’interno di programmi internazionali e nazionali condotti per il monitoraggio dei mari europei. Nello specifico si fa riferimento ai progetti Marine Strategy Framework Directive (MSFD; Direttiva 2008/56 EC), Water Framework Directive (WFD; Direttiva 2000/60 EC) e al progetto bandiera RITMARE (SP4 - Pianificazione dello spazio marittimo: Ambiente di mare profondo). Parte delle direttive e il progetto succitati sono finalizzati allo studio di fenomeni di impatto antropico in ambiente marino superficiale e profondo e all'individuazione di azioni specifiche in grado di limitare e ridurre l’impatto antropogenico a livelli sostenibili per l’ecosistema marino. Oltre allo studio dei contaminanti prioritari, tra cui metalli pesanti e composti organici (IPA, PCB, pesticidi, etc.), le direttive MSFD e WFD prevedono lo studio di una nuova classe di contaminanti definiti “emergenti” perché risultanti principalmente dall'impiego di tecnologie e materiali innovativi, e dall'ampia diffusione di alcune sostanze nel campo della chimica, della farmacologia e della cosmoceutica. Il progetto RITMARE dedica parte delle attività di ricerca allo studio degli effetti del marine litter, ovvero all’impatto di macro- e micro-plastiche di origine antropica in ambiente marino superficiale e profondo. Nello specifico, il progetto prevede: i) lo studio della distribuzione geografica delle micro-plastiche e le possibili zone di concentrazione in aree marine specifiche per effetto della circolazione oceanica; ii) l’impatto di tali detriti sull’ecosistema, in termini di interazione con le funzioni vitali degli organismi (soffocamenti per ingestione, riduzione di capacità funzionali specifiche, ecc.) e di rilascio di contaminanti con fenomeni di bioaccumulo/biomagnificazione nelle reti trofiche marine. Negli ultimi anni, il gruppo di biogeochimica dell’IAMC-CNR ha realizzato una serie di campagne oceanografiche (Anomcity_2012, 2013, 2014, 2015) finalizzate allo studio dei processi di contaminazione da metalli pesanti e contaminanti organici a scala di bacino e sottobacino nel Mediterraneo occidentale. I risultati hanno permesso di individuare sorgenti di impatto, pathways di distribuzione e sorte dei diversi contaminanti nelle varie aree investigate (Bonsignore et al., 2013, 2015; Sprovieri et al., 2011, 2013; Salvagio Manta et al., 2016; Oliveri et al., 2016) nonché i cosiddetti “inventari” delle diverse tipologie di inquinati sulla base dello studio di carote di sedimento per cui è stata eseguita una datazione sulla base dei radionuclidi di Cs e Pb (dati non pubblicati). La Campagna Anomcity_2016 è stata incentrata su due obiettivi: 1. ampliamento dello stato di conoscenze sulla distribuzione in acqua di mare (fase disciolta) di un numero selezionato di contaminanti emergenti in aree marino-costiere del Mediterraneo impattate dall’attività antropica; 2. stima di abbondanza e distribuzione delle microplastiche in aree geografiche selezionate dal progetto RITMARE, considerando i processi di trasporto nell’ambiente, e di specie target come potenziali bioindicatori di accumulo di marine litter e analisi dei potenziali effetti di trasferimento sulla rete trofica. Per quanto concerne lo studio dei contaminanti emergenti, questa campagna ha rappresentato una delle primissime esperienze a scala internazionale dedicata a tale tipologia di indagine nel Mar Mediterraneo

Trying to resolve the taxonomic confusion of Paracalanus parvus species complex (Copepoda, Calanoida) in the Mediterranean and Black Seas through a combined analysis of morphology, molecular taxonomy and DNA metabarcoding

Paracalanus parvus is reported as the most abundant representative of the genus and one of the main components of the coastal zooplankton in the Mediterranean and Black Seas. However, the subtle taxonomic differences between P. parvus and the congeneric species P. indicus and P. quasimodo, in combination with the ample morphological variation found in Mediterranean specimens, render problematic the correct identification. A recent molecular study by Cornils and Held (2014) provided evidence of cryptic speciation in the P. parvus complex and indicated that P. parvus s.s. does not have global distribution, but may be restricted to the northeastern Atlantic. In order to clarify the taxonomic status and distribution of this species complex in the Mediterranean and Black Seas, a study was conducted on Paracalanus specimens collected from different locations across the aforementioned marine basins and sequenced for portion of the COI mitochondrial gene. An accurate taxonomic analysis was also carried out to correlate morphological characteristics with the molecular species' assignation. The phylogenetic analysis of the specimens together with the publicly available sequences of P. parvus complex revealed the presence of four molecular operational taxonomic units (MOTUs) in the Mediterranean, which differed in abundance and geographic distribution. The combination of morphological and molecular data revealed great inconsistencies between morphospecies and MOTUs. Moreover, several bulk zooplankton samples were analyzed through DNA metabarcoding in the frame of the “MetaCopepod” project to provide more extensive information on the spatiotemporal distribution and abundance of the target specie

The “MetaCopepod” project: Designing an integrated DNA metabarcoding and image analysis approach to study and monitor the diversity of zooplanktonic copepods and cladocerans in the Mediterranean Sea

The timely and accurate analysis of marine zooplankton diversity is a challenge in ecological and monitoring studies. Morphology-based identification of taxa, which requires taxonomy experts, is time consuming and cannot provide accurate resolution at species level in several cases (e.g. immature stages, cryptic species, broken specimens). The “MetaCopepod” project is aimed at overcoming these limitations by developing a high-throughput and cost effective methodology that integrates DNA metabarcoding and image analysis. Utilizing the accuracy of DNA metabarcoding in species recognition and the quantitative results of image analysis, zooplankton diversity (mainly of copepods and cladocerans) is assessed both qualitatively (species' composition) and quantitatively (abundance, biomass and size-distribution). To achieve this goal, bulk zooplankton samples are first scanned and analyzed with ZooImage and then massively sequenced for a selected fragment of the mitochondrial 16S rRNA gene. Through a bioinformatic pipeline, sequences are compared to a reference genetic database, constructed within the project, and identified at species- level. The methodology was calibrated by using both mock and taxonomically identified samples and demonstrated on samples collected monthly from monitoring stations across the Mediterranean Sea. It is currently optimized for higher integration and accuracy and is expected to become a powerful tool for monitoring zooplankton in the long term and for early warning of bioinvasions and other ecosystem change

Physical forcing and physical/biochemical variability of the Mediterranean Sea: a review of unresolved issues and directions for future research

This paper is the outcome of a workshop held in Rome in November 2011 on the occasion of the 25th anniversary of the POEM (Physical Oceanography of the Eastern Mediterranean) program. In the workshop discussions, a number of unresolved issues were identified for the physical and biogeochemical properties of the Mediterranean Sea as a whole, i.e., comprising the Western and Eastern sub-basins. Over the successive two years, the related ideas were discussed among the group of scientists who participated in the workshop and who have contributed to the writing of this paper. Three major topics were identified, each of them being the object of a section divided into a number of different sub-sections, each addressing a specific physical, chemical or biological issue: 1. Assessment of basin-wide physical/biochemical properties, of their variability and interactions. 2. Relative importance of external forcing functions (wind stress, heat/moisture fluxes, forcing through straits) vs. internal variability. 3. Shelf/deep sea interactions and exchanges of physical/biogeochemical properties and how they affect the sub-basin circulation and property distribution. Furthermore, a number of unresolved scientific/methodological issues were also identified and are reported in each sub-section after a short discussion of the present knowledge. They represent the collegial consensus of the scientists contributing to the paper. Naturally, the unresolved issues presented here constitute the choice of the authors and therefore they may not be exhaustive and/or complete. The overall goal is to stimulate a broader interdisciplinary discussion among the scientists of the Mediterranean oceanographic community, leading to enhanced collaborative efforts and exciting future discoveries

Community-Level Responses to Iron Availability in Open Ocean Plankton Ecosystems

Predicting responses of plankton to variations in essential nutrients is hampered by limited in situ measurements, a poor understanding of community composition, and the lack of reference gene catalogs for key taxa. Iron is a key driver of plankton dynamics and, therefore, of global biogeochemical cycles and climate. To assess the impact of iron availability on plankton communities, we explored the comprehensive bio-oceanographic and bio-omics data sets from Tara Oceans in the context of the iron products from two state-of-the-art global scale biogeochemical models. We obtained novel information about adaptation and acclimation toward iron in a range of phytoplankton, including picocyanobacteria and diatoms, and identified whole subcommunities covarying with iron. Many of the observed global patterns were recapitulated in the Marquesas archipelago, where frequent plankton blooms are believed to be caused by natural iron fertilization, although they are not captured in large-scale biogeochemical models. This work provides a proof of concept that integrative analyses, spanning from genes to ecosystems and viruses to zooplankton, can disentangle the complexity of plankton communities and can lead to more accurate formulations of resource bioavailability in biogeochemical models, thus improving our understanding of plankton resilience in a changing environment