Response of the Calanoid Copepod Clausocalanus furcatus, to Atmospheric Deposition Events: Outcomes from a Mesocosm Study

Atmospheric deposition is assumed to stimulate heterotrophic processes in highly oligotrophic marine systems, controlling the dynamics and trophic efficiency of planktonic food webs, and is expected to be influenced by climate change. In the course of an 8-day mesocosm experiment, we examined the channeling, of the Saharan dust (SD) and mixed aerosols (A) effects on microplankton up to the copepod trophic level, in the highly oligotrophic Eastern Mediterranean Sea. Based on mesocosms with SD and A treatments, we evaluated the feeding response of the dominant copepod Clausocalanus furcatus every other day. We hypothesized that increased food availability under atmospheric deposition would result in increased copepod ingestion rates, selectivity and production. Overall, no robust pattern of food selection was documented, and daily rations on the prey assemblage of all mesocosms were very low indicating severe food limitation of C. furcatus. Although increased food availability was not true, after few days ingestion of ciliates was maximized, followed by egg production, in both the SD and A treatments, indicating their importance in the diet of this copepod as well as a response of C. furcatus feeding performance. Our results help in understanding the trophic efficiency of marine food webs in ultra-oligotrophic environments under atmospheric deposition. We suggest that future mesocosm research in oligotrophic waters should consider more than one copepod speciesVersión del edito

Large-scale testing of phytoplankton diversity indices for environmental assessment in Mediterranean sub-regions (Adriatic, Ionian and Aegean Seas)

Abstract According to the methodological standards established by Marine Strategy Framework Directive, the assessment for the pelagic habitat under the Biodiversity Descriptor should be carried out at the regional or sub-regional level. In the case of Mediterranean Sea, the sub-regional assessment seems optimal to take into account biogeographic differences in species composition and functional characteristics. Previous research has shown that phytoplankton diversity indicators are efficient for reliable environmental assessments, although more effort has been recommended to test these indicators on a wide spatial scale to cover wider gradients of natural and anthropogenic pressures. In this work, a set of eight diversity indices was tested against the pressure levels within a common data set of the structure and abundance of phytoplankton communities from the Adriatic, Ionian and Aegean Seas. Expert knowledge was used to define four categories of impacts that take into account partial pressures, such as point and non-point pollution, industry, ports and fisheries. At the level of the common data set, most of the diversity, evenness and dominance indices could only distinguish between the highest level of impact and the rest of impact categories. These indices maintained the distinction between two levels of subsequently dichotomised impacts (no to low impact vs. high impact) across latitudinal and longitudinal gradients. On average, the indices were less sensitive to impacts in the northernmost and westernmost areas than in the southernmost and easternmost areas, although they still showed a significant response. The results also suggest that phytoplankton communities become more uniform and less dominated by a single taxon as sampling depth increases at sites with low impact, while evenness and dominance at impacted sites remain similar at all depths. In order to establish meaningful definitions of good environmental status and targets for pelagic habitats in the Mediterranean Sea, it is necessary to establish spatially specific thresholds by additional examination of indices of good performance

Status of pelagic habitats within the EU-Marine Strategy Framework Directive: Proposals for improving consistency and representativeness of the assessment

Anthropogenic activities have transformed the pelagic habitat in the last decades with profound implications for its essential functions. While the EU-Marine Strategy Framework Directive 2008/56/EC and the Commission Decision (EU) 2017/848 have set criteria and methodological standards for the assessment and determination of Good Environmental Status (GES) for pelagic habitats in EU waters, there is strong evidence that Member States have not yet harmonized the pelagic GES assessment across EU marine waters. Today, pelagic habitats are assessed by evaluating whether good status is achieved by each of the pelagic indicators, but this approach fails to observe the high variability of the pelagic environment. To this end, GES is not estimated at pelagic habitats scale but only for each individual indicator. This paper synthesises the latest developments on pelagic habitats assessment and identifies the main factors limiting the consistency of the assessment across Member States: i) coarse spatial and temporal scales of sampling effort as regards to the pelagic habitat dynamics, ii) little consideration of the whole range of plankton (and, to some extent, of zooplankton) size and trophic spectra, iii) lack of integrated hydro-biogeochemical and biological studies and collaboration among experts from different scientific fields, iv) limited availability of pressure-based indicators, and v) lack of integration methods of the pelagic indicators’ status for the GES determination. This analysis demonstrates the importance of maintaining a consistent sampling frequency and a spatially extensive network of stations across the gradient of anthropogenic pressures, where spatial environmental data can help objectively extrapolating field data.The authors would like to thank the Pelagic Habitats Experts, part of the MSFD Biodiversity Expert Network for the fruitful discussions on the harmonisation of the MSFD assessment and monitoring for pelagic habitats. CM, MP, JND, and AP were funded by the Joint Research Centre of Ispra (Italy). IV wishes to acknowledge support from the program “Monitoring and recording the situation of the marine sub-regions of Greece / Upgrading and functional updating of the MSFD monitoring network”, funded by national and EU funds under National Strategic Reference Framework 2014–2020 (MIS 5010880), and the European project ABIOMMED: Support coherent and coordinated assessment of biodiversity and measures across Mediterranean for the next 6-year cycle of MSFD implementation, funded by DG Environment (11.0661/2020/839620/SUB/ENV.C2), coordinator Dr. Kalliopi Pagou, HCMR.Peer reviewe

Phytoplankton dynamics in relation to seasonal variability and upwelling and relaxation patterns at the mouth of Ria de Aveiro (West Iberian Margin) over a four-year period

From June 2004 to December 2007, samples were weekly collected at a fixed station located at the mouth of Ria de Aveiro (West Iberian Margin). We examined the seasonal and inter-annual fluctuations in composition and community structure of the phytoplankton in relation to the main environmental drivers and assessed the influence of the oceano-graphic regime, namely changes in frequency and intensity of upwelling events, over the dynamics of the phytoplankton assemblage. The samples were consistently handled and a final subset of 136 OTUs (taxa with relative abundance > 0.01%) was subsequently submitted to various multivariate analyses. The phytoplankton assemblage showed significant changes at all temporal scales but with an overriding importance of seasonality over longer-(inter-annual) or shorter-term fluctuations (upwelling-related). Sea-surface temperature, salinity and maximum upwelling index were retrieved as the main driver of seasonal change. Seasonal signal was most evident in the fluctuations of chlorophyll a concentration and in the high turnover from the winter to spring phytoplankton assemblage. The seasonal cycle of production and succession was disturbed by upwelling events known to disrupt thermal stratification and induce changes in the phytoplankton assemblage. Our results indicate that both the frequency and intensity of physical forcing were important drivers of such variability, but the outcome in terms of species composition was highly dependent on the available local pool of species and the timing of those events in relation to the seasonal cycle. We conclude that duration, frequency and intensity of upwelling events, which vary seasonally and inter-annually, are paramount for maintaining long-term phytoplankton diversity likely by allowing unstable coexistence and incorporating species turnover at different scales. Our results contribute to the understanding of the complex mechanisms of coastal phytoplankton dynamics in relation to changing physical forcing which is fundamental to improve predictability of future prospects under climate change.Portuguese Foundation for Science and Technology (FCT, Portugal) [SFRH/BPD/ 94562/2013]; FEDER funds; national funds; CESAM [UID/AMB/50017]; FCT/MEC through national funds; FEDERinfo:eu-repo/semantics/publishedVersio

Case Study: LifeWatch Italy Phytoplankton VRE

LifeWatch Italy, the Italian node of LifeWatch ERIC, has promoted and stimulated the debate on the use of semantics in biodiversity data management. Actually, biodiversity and ecosystems data are very heterogeneous and need to be better managed to improve the actual scientific knowledge extracted, as well as to address the urgent societal challenges concerning environmental issues. LifeWatch Italy has realized the Phytoplankton Virtual Research Environment (hereafter Phytoplankton VRE), a collaborative working environment supporting researchers to address basic and applied studies on phytoplankton ecology. The Phytoplankton VRE provides the IT infrastructure to enable researchers to obtain, share and analyse phytoplankton data at a level of resolution from individual cells to whole assemblages. A semantic approach has been used to address data harmonisation, integration and discovery: an interdisciplinary team has developed a thesaurus on phytoplankton functional traits and linked its concepts to other existing conceptual schemas related to the specific domain

Abundance of microplankton in the eastern Mediterranean Sea in April 2008 during SES_GR2

The dataset is based on samples taken from 12 stations in Northern Aegean Sea, Southern Aegean Sea, Ionian Sea and Libyan Sea during August-September 2008. 12 Niskin bottles (8lt) made by PVC with rubber coated o rings and stainless steel ss springs. Seawater samples (150 mL) were collected from selected depths of the water column (2, 20, 50, 75, 100 m) for the identification and enumeration of phytoplankton cells (>= 5 µm). The samples were fixed with Lugol solution and concentrated to 25 mL by sedimentation. Phytoplankton species abundance was determined with an inverted light microscope (OLYMPUS IX70) according to the Utermohl method (Utermohl, 1958)

Abundance of microplankton in the eastern Mediterranean Sea in March and April 2008 during SES_GR1

The dataset is based on samples taken from 12 stations in Southern Aegean Sea, Northern Aegean Sea, Ionian Sea and Libyan Sea during March-April 2008. 12 Niskin bottles (8lt) made by PVC with rubber coated o rings and stainless steel ss springs. Seawater samples (150 ml) were collected from selected depths of the water column (2, 20, 50, 75, 100 m) for the identification and enumeration of phytoplankton cells (>=5 µm). The samples were fixed with Lugol solution and concentrated to 25 ml by sedimentation. Phytoplankton species abundance was determined with an inverted light microscope (OLYMPUS IX70) according to the Utermohl method (Utermohl, 1958)

Ecology of harmful microalgae and impact on the marine benthic ecosystem

Harmful algae attract interest due to the increase of duration and intenseness of Harmful Algal Blooms (HABs), with serious impacts on coastal ecosystems, public health and economy. Many harmful algae are toxic microalgae that are consumed by pelagic and benthic organisms. The subject of this Doctoral Thesis was the study of ecology and toxicity of the dinoflagellates Dinophysis acuminata and Prorocentrum lima and the diatom Pseudo-nitzschia multiseries, as well as the transfer of their toxins to the bivalves Callista chione and Ruditapes decussatus. The studied microalgae species cause HABs in many coastal areas, including South Europe, e.g. Greece and Spain, while the studied bivalve species present wide distribution in these two counties and commercial interest. The aims of the Thesis were the study of: a) the natural populations and HABs of D. acuminata in relation to the availability of organic matter and other biotic/abiotic parameters in the Gulf of Thermaikos, b) the impact of nitrogen or phosphorus deficiency conditions on the growth and toxicity of P. lima, and c) the accumulation and impact of D. acuminata, P. lima και P. multiseries toxins on the bivalves C. chione from Thermaikos Gulf and R. decussatus from Ría de Vigo, Spain.Τα επιβλαβή φύκη παρουσιάζουν ενδιαφέρον καθώς η ένταση και η διάρκεια των εξάρσεών τους αυξάνονται με σοβαρές επιπτώσεις στα παράκτια οικοσυστήματα, τη δημόσια υγεία και οικονομία. Πολλά επιβλαβή φύκη είναι τοξικά μικροφύκη και καταναλώνονται από πελαγικούς και βενθικούς οργανισμούς. Αντικείμενο της Διδακτορικής Διατριβής αποτέλεσε η μελέτη της οικολογίας και τοξικότητας των δινομαστιγωτών Dinophysis acuminata και Prorocentrum lima και του διατόμου Pseudo-nitzschia multiseries, καθώς και η μεταφορά των τοξινών τους στα δίθυρα μαλάκια Callista chione και Ruditapes decussatus. Αυτά τα είδη μικροφυκών προκαλούν επιβλαβείς εξάρσεις σε πολλές παράκτιες περιοχές συμπεριλαμβανομένης της Ν Ευρώπης, όπως η Ελλάδα και η Ισπανία, τα δε είδη διθύρων παρουσιάζουν εκεί ευρεία εξάπλωση και εμπορικό ενδιαφέρον. Στόχοι της Διατριβής ήταν: α) η μελέτη των φυσικών πληθυσμών και των εξάρσεων του είδους D. acuminata σε σχέση με τη διαθεσιμότητα της οργανικής ύλης και άλλων βιοτικών/αβιοτικών παραμέτρων στον Θερμαϊκό Κόλπο, β) η μελέτη της επίδρασης των συνθηκών έλλειψης αζώτου/φωσφόρου στην αύξηση του είδους P. lima και την παραγωγή τοξίνης στα κύτταρά του, γ) η μελέτη της συσσώρευσης και της επίδρασης των τοξινών που παράγουν τα μικροφύκη D. acuminata, P. lima, P. multiseries στα δίθυρα C. chione από τον Θερμαϊκό και R. decussatus από τον Κόλπο του Vigo της Ισπανίας

Impact of a Dinophysis acuminata Bloom on the Copepod Acartia clausi: first indications

Faecal pellet production and content along with egg production of the dominant copepod species Acartia clausi were studied in the Thermaikos Gulf (NW Aegean Sea) during a pre-bloom and a bloom of the toxic dinoflagellate Dinophysis acuminata. Both faecal pellet production (6.8–8.6 ind−1 d−1) and egg production (15.8–47.6 ind−1 d−1) appeared unrelated to the D. acuminata bloom. Less than 11% of the copepod faecal pellets contained one or two D. acuminata cells, almost intact, whereas the other material in the pellets was broken into small pieces or amorphous shapes. The toxin outflux seemed to be insignificant when compared to the mean toxin concentration from the whole D. acuminata population. Finally, the potential grazing impact of A. clausi on D. acuminata during the study period was low.European Commission | Ref. EVK3-2001-00055European Commission | Ref. H2020, n. 87115