Coccolithus pelagicus subsp. pelagicus versus Coccolithus pelagicus subsp. braarudii (Coccolithophore, Haptophyta): A proxy for surface subarctic Atlantic waters off Iberia during the last 200 kyr

A Multivariate Morphon Analysis (MMA) of Coccolithus pelagicus (s. l.) coccoliths was performed on 178 samples from an oceanic core recovered off the Portuguese margin (MD95-2040), in order to define the morphometric boundaries of its morphotypes and their behaviour during the last two glacial cycles. The recurrent occurrence of the smaller morphotype of this taxon, C. pelagicus subsp. pelagicus, was recognized for the first time off the Portuguese coast. Three sections, around Heinrich Layers 1 and 6 and Termination II-Eemian, were selected to establish high resolution comparisons between C. pelagicus subsp. pelagicus and C. pelagicus subsp. braarudii and two independent proxies for cold water masses: the records of the planktonic foraminifera Neogloboquadrina pachyderma (sinistral) and ice-rafted detritus (IRD). There is an overall negative correlation between C. pelagicus subsp. pelagicus and C. pelagicus subsp. braarudii as expressed by MMA Factor 1, the scores of which respond similarly to those of two non-cocolithophore proxies and consequently, is proposed as a calcareous nannoplankton proxy for the influence of subpolar waters in the region. Detailed analysis, however, showed occasional decoupling amongst these three proxies, which are used to highlight significant changes between the cooling–warming sequences of distinct events off Iberia.info:eu-repo/semantics/publishedVersio

Characterization of the coccolithophore community off Cabo Verde archipelago, including the Senghor Seamount (Eastern North Atlantic)

A systematic investigation of the extant coccolithophore community around Cabo Verde archipelago was per formed during the cruise MSM49 of RV Maria S. Merian, which took place in the late fall of 2015. The description of the spatial and vertical distributions of coccolithophores was based on a survey performed to the north, east and south of Cabo Verde archipelago, between the surface and 150 m water depth. The total cell densities ob tained for the studied region were relatively low, reaching to a maximum of 30 × 103 cell L− 1 in the upper 50 m over the southeastern slope of the Senghor seamount. Emiliania huxleyi and Gephyrocapsa oceanica were the dominant species, followed by Florisphaera profunda. The coccolithophore distribution off Cabo Verde was essentially explained by relatively warm and nutrient-depleted waters in the region during the surveyed interval, in result of the weaker NE trade winds and the northward migration of the Intertropical Convergence Zone. In these conditions, a notable zonation of coccolithophores along depth was depicted, in consequence of the inferred general well-stratified water column. Four typical depth-related groups were identified: (i) a Shallow oligotrophic (10–30 m), represented by Discosphaera tubifera and Umbellosphaera spp.; (ii) an Intermediate (40–50 m), formed by the three placolith-bearing species E. huxleyi, G. ericsonii and G. oceanica, and by Algir osphaera robusta, Helicosphaera spp., Michaelsarsia spp., Syracosphaera spp. and Umbilicosphaera spp.; (iii) a Deep (60–75 m) with F. profunda, Ophiaster spp., Oolithotus spp. and Reticulofenestra sessilis as typical members; (iv) and The Deepest (>80 m), composed by Gladiolithus flabellatus and Syracosphaera lamina. In addition, high abun dances of G. oceanica related with the Eddy station were attributed to the transport and thriving of the coastal coccolithophore community, dominated by this species, from the African coast towards Cabo Verde.info:eu-repo/semantics/publishedVersio

The effect of a transient frontal zone on the spatial distribution of extant coccolithophores around the Madeira archipelago (Northeast Atlantic)

In order to characterize the coccolithophore community around the Madeira archipelago and to understand the effect of a transient frontal zone on its distribution, 149 seawater samples from the first 150 m were collected in 37 stations, during the research cruise POS466 of RV Poseidon. The present study revealed the occurrence of two biogeographic domains, NE and SW, during the late winter of 2014, with distinct physical-chemical and cal careous nannoplankton characteristics. The NE sector was characterized by higher coccolithophore cell densities (mean of 56 × 103 cell L−1) and a slightly lower diversity (Margalef diversity index of 1.80) when compared with the SW sector (mean of 47 × 103 cell L−1; Md index of 1.86). The more productive sector, NE, was asso ciated with colder, less saline and higher nutrient content water masses, linked to the injection of a westerly flow with origin in the Azores frontal system. Total cell densities ranged between 12 × 103 and 112 × 103 cell L−1, being Emiliana huxleyi the dominant species followed by small Gephyrocapsa. The most common and subordinate taxa, in order of decreasing abundance, were: Gephyrocapsa oceanica, Michaelsarsia spp., Syracosphaera spp., Umbilicosphaera spp. and Algirosphaera robusta. Relationships between environmental conditions and spatial and vertical variability in coccosphere abundance, associated E. huxleyi and small Gephyrocapsa with the more productive water mass conditions, linked to the thermohaline transient front. G. oceanica distribution indicated its preference for warmer and less turbulent coastal waters, when compared to E. huxleyi and small Gephyrocapsa. Michaelsarsia spp. and A. robusta revealed preference for the northwest coast of Madeira, associated with mesotrophic con ditions of the water column. Syracosphaera spp. and Umbilicosphaera spp. were well distributed throughout the archipelago and along the sampled depths, from the coast to open ocean conditions, as well as from lower to higher productive zones, displaying affinities for the meso to oligotrophic conditions, typical of these subtropical waters. The broad depth range of several taxa and the nonexistence of the coccolithophore vertical succession were the result of homogeneous and generalized well-mixed surface layer during the present survey.info:eu-repo/semantics/publishedVersio

A guide to extant coccolithophores (Calcihaptophycidae, Haptophyta) using light microscopy

We present here a collection of light microscope, and comparative scanning electron microscope, images of extant coccolithophores, sampled from various oceanic locations, and also from cultured strains. This series of im ages is intended to provide students and researchers interested in extant coccolithophore biology with an accessible means of identifying the common coccolithophore species found in modern assemblages.info:eu-repo/semantics/publishedVersio

Sea surface dynamics and coccolithophore behaviour during sapropel deposition of Marine Isotope Stages 7, 6 and 5 in Western Adriatic sea

Se presenta un análisis detallado de los nanofósiles calcáreos registrados en el testigo PRD1-2, recuperado durante la campaña PRO MESS 1 con el objetivo de estudiar las variaciones en las asociaciones durante los MIS (Estadios Isotópicos Marinos) 7, 6 y 5, que in tegran capas equivalentes a los sapropeles S8eq.–S3eq.. Los datos reflejan un descenso en la productividad de cocolitóforos, marcada por Gephyrocapsa spp., durante los MIS 7 y 6 en la capa equivalente al sapropel S5eq. Por el contrario, Florispharea profunda mues tra picos en su abundancia en esos intervalos, reflejando una posición relativamente profunda de la nutriclina. En las dos capas equi valentes a sapropeles del MIS 5 (S4eq. y S3eq.) se observa lo opuesto. La sedimentación de esos sapropeles atípicos son concomitantes con la producción de agua profunda del Adriático y una subsecuente mezcla, como consecuencia de la actividad del viento Bora (nor este), favoreciendo la eclosión de especies de zona fótica superior en relación a las de zona fótica inferior. Por otra parte, se ponen de manifiesto modelos de distribución similar entre especímenes retrabajados (Cretácico-Terciario), Coccolithus pelagicus y Helicos phaera carteri, con incremento importante en las capas equivalentes a sapropeles de los MIS 7 y 6 y durante la parte final del MIS 6, el más frío y seco. Debido al amplio rango de distribución de C. pelagicus (Paleoceno temprano-Reciente) y H. carteri (Mioceno-Re ciente) los ejemplares procedentes del continente y vertidos a la cuenca Adriática, o redistribuidos por Corrientes de fondo, son de particular importancia en cientos intervalos (210-200, 145, 135, 110 y 85 ka). Syracosphaera spp., Rhabdosphaera clavigeraaa y Cal ciosolenia spp., normalmente relacionadas con aguas cálidas y oligotróficas, no muestran relación con el registro isotópico. Sin em bargo, su importante incremento hacia la parte superior o sobre la terminación de algunas capas equivalentes a sapropeles es coherente con el final de las condiciones secas y con el subsecuente de una situación oligotrófica y una redistribución de los nutrientes. Al mismo tiempo, el incremento de Braarudosphaera bigelowii coincidiría con una reducción en la salinidad durante S8eq. y S6eq., aun que su presencia puede corresponder también a aportes continentales, dado su amplio rango estratigráfico (Cretácico-Reciente).A detailed calcareous nannofossil analysis was performed in the core PRAD1-2, recovered in the Mid-Adriatic Deep during the PROMESS 1 Cruise, in order to show fluctuations of several species during the Marine Isotope Stages 7, 6 and 5, crossing the S8eq.–S3eq. sapropel-equivalent layers. This study reports a decrease in the coccolithophore productivity, given by Gephyrocapsa spp. abundance decreases, during the deposition of MIS 7 and MIS 6 sapropel-equivalent layers and also during S5eq. Florisphaera pro funda, on the contrary, shows abundance peaks within these intervals, reflecting a deeper position of the nutricline. Within the two last sapropel-equivalent layers of MIS 5 (S4eq. and S3eq.) the opposite can be observed. The deposition of these atypical sapropels may have been concomitant with some Adriatic Deep Water production and subsequent some water column mixing, in result of the activ ity of the north-easterly Bora wind, favouring the development of the upper photic zone species in relation to the lower photic zone inhabitant F. profunda. Similar general abundance patterns are evidenced by reworked specimens (Cretaceous-Tertiary), Coccolithus pelagicus and Helicosphaera carteri, with important increases during the sapropel-equivalent layers of MIS 7 and MIS 6 and during the latest part of the glacial stage 6, the coldest and the driest one. Due to the extended fossil record of C. pelagicus (Early Paleocene Recent) and H. carteri (Miocene-Recent), reworked placoliths and helicoliths from a continental source, by precipitation and runoff into the Adriatic basin, or from redistribution by bottom currents, are of particular importance at certain moments (210-200, 145, 135, 110 and 85 kyr). Syracosphaera spp., Rhabdosphaera clavigeraa and Calciosolenia spp., usually related to warm and oligotrophic water masses, do not show a clear correlation with the isotope record. However, their important increases at the top or above the ter mination of some sapropel-equivalent layers is consistent with the end of dryer conditions that feature the sapropel deposition, and with the subsequent reestablishment of the general oligotrophic state of the surface water with a nutrient redistribution. At the same time a salinity reduction should occur due to the simultaneous presence of Braarudosphaera bigelowii. During S8eq. and S6eq. the pres ence of B. bigelowii coupled with its stratigraphic range (Cretaceous-Recent), may also indicate a continental source for some pental iths.info:eu-repo/semantics/publishedVersio

Nutrient-specific responses of a phytoplankton community: a case study of the North Atlantic Gyre, Azores

Nutrient concentrations are unevenly distributed in the oceans, influencing the abundance and composition of phytoplankton communities. Even so, the dominant driving factors responsible for variability between phytoplankton communities are still unclear. In the North Atlantic Gyre, the Azores present a good opportunity to study phytoplankton communities of oligotrophic areas that experience nutrient pulses. We followed the development of an enclosed natural phytoplankton community occurring off the coast of Terceira (Azores) and tested the effects of single (nitrate, phosphate, silicate and a mix of the trace metals Fe, Co, Cu, Mo, Zn and Mn) and combined nutrient enrichments on phytoplankton abundance, particulate organic matter (POM) build-up, nutrient drawdown and community composition. Towards the end of the microcosm-based incubation, biomass developed dramatically (430-fold) when all the nutrients considered were added simultaneously. Importantly, the community composition at the end of the incubation was dependent on the combination of nutrients supplied, with diatoms dominating most of the treatments; coccolithophores under Phosphate + Trace Metals; and organisms with characteristics of a nitrogen fixer such as low δ15N under full nutrient enrichment. These results indicate group-specific nutrient requirements and limitations occurring near the Azores with a few taxa dominating the groups’ response to nutrient pulses

Seasonal and interannual variations in coccolithophore abundance off Terceira Island, Azores (Central North Atlantic)

In order to characterize the natural coccolithophore community occurring offshore Azores and to de-termine their annual and interannual patterns, monthly samples were collected, from September 2010 toDecember 2014, in the photic zone off Terceira Island.The present study revealed a clear seasonal distribution and a considerable interannual variability of theliving coccolithophore community. The highest coccolithophore abundances were observed during spring andwinter months, especially due to the smaller speciesEmiliania huxleyiandGephyrocapsa ericsonii. In fact, thehighest biomass period was registered during April 2011, associated with enhanced abundance of the over-calcified morphotype ofE. huxleyi,whichwaspossiblyinfluenced by subpolar waters and subsequent up-welling conditions. The highest abundances ofGephyrocapsa muelleraewere recorded during June 2011 and2014, indicating that this species characterizes the transition between the period of maximum productivity andthe subsequent smoother environmental conditions, thefirst and the later stages of the phytoplankton suc-cession described by Margalef, respectively. During summer to early fall, a gradual decrease of the overallcoccolithophore abundance was observed, while the species richness (Margalef diversity index) increased. Asubtropical coccolithophoreassemblage mainly composed byUmbellosphaera tenuis,Syracosphaeraspp.,Dis-cosphaera tubifera,Rhabdosphaera clavigeraandCoronosphaera mediterraneaindicated the presence of surfacewarmer waters accompanied by reduced mixing and low nutrients concentration. During late fall to winter, thecoccolithophore abundance increased again with a concomitant reduction in species diversity. This is poten-tially linked to low sea surface temperatures, moderate nutrients concentration and surface mixed layerdeepening. During 2011, colder and productive waters led to an increase in the total coccolithophore abun-dances. On contrary, during 2012, characterized by milder environmental conditions, an increase in the di-versity of the community was prevalent. The noticeably coccolithophore response to variations in the mainphysical variables and on main traditional nutrients corroborates the importance of this group as proxy ofmarine environmental conditions in the past.&2016 Elsevier Ltd. All rights reserved.1. IntroductionCoccolithophores are pelagic unicellular algae, members of thehaptophyte class Prymnesiophyceae Hibberd, distinguished by theability to produce calcite platelets called coccoliths, which surroundthe living cell and form an exoskeleton called coccosphere (e.g. Winterand Siesser, 1994; Young, 1994). Coccolithophores, known since thelate Jurassic (Hay, 2004), have an ocean wide distribution and re-present the most productive calcifying organisms on Earth (Honjo,1996). They also affect the ocean-atmosphere carbon dioxide exchangeand produce dimethyl sulfide (DMS), which stimulates cloud forma-tion, thus actively participating in the climate system (Berger et al.,1989;Westbroek et al., 1993;Rost and Riebesell, 2004). Since thiscalcifying group has potential to fossilize as calcareous nannoplankton,it becomes a (paleo)environmental proxy directly dependent ontemperature, salinity, and nutrients and light availability (e.g.,McIntyreand Bé, 1967;Giraudeau et al., 1993; Winter and Siesser, 1994).Coccolithophores usually dominate the phytoplankton biodiversity inthe oligotrophic central gyres of the oceans (e.g. McIntyre and Bé, 1967;Winter et al., 1994;Ziveri et al., 2004), being also markedly present attemperate (e.g.Giraudeau and Bailey, 1995;Cachão et al., 2000) and highlatitude eutrophic regimes (e.g.Andruleit, 1997;Baumann et al., 2000).Although the geographic distribution of coccolithophores hasbeen well studied over the last four decades, its seasonal dynamicsContents lists available atScienceDirectjournal homepage:www.elsevier.com/locate/csrContinental Shelf Researchhttp://dx.doi.org/10.1016/j.csr.2016.01.0190278-4343/&2016 Elsevier Ltd. All rights reserved.nCorresponding author. Present address: CIIMAR-Madeira, Caminho da Penteada105, Funchal, Portugal.E-mail address:[email protected](Á. Narciso).Continental Shelf Research 117 (2016) 43–56info:eu-repo/semantics/publishedVersio