Environmental controls of diatom species in northeast Pacific sediments

Non-linear, unimodal techniques are suitable for estimation of environmental properties in the northeast (NE) Pacific based on fossil diatom taxa (species and/or species groups) found in modern (core-top) sediments. Canonical Correspondence Analysis (CCA), a constrained ordination technique, discerned best-fit relationships among two multivariate datasets (the floral and the environmental) and thus yielded insight into the environmental variables that best explain the species variance within diatom populations. Based on these insights, we developed predictive functions for annual Primary Productivity (PP) and seasonal range of sea Sea-Surface Temperature using unimodal models and cross validation techniques. Estimates of annual PP (r²_jack = 0.92; RMSEP = 91.94 gC/m²/y) explained the highest percentage of variance in the core-top diatom record (22.1%).     

Summer diatom blooms in the North Pacific subtropical gyre: 2008-2009

The summertime North Pacific subtropical gyre has widespread phytoplankton blooms between Hawaii and the subtropical front (～30°N) that appear as chlorophyll (chl) increases in satellite ocean color data. Nitrogen-fixing diatom symbioses (diatom-diazotroph associations: DDAs) often increase 10(2)-10(3) fold in these blooms and contribute to elevated export flux. In 2008 and 2009, two cruises targeted satellite chlorophyll blooms to examine DDA species abundance, chlorophyll concentration, biogenic silica concentration, and hydrography. Generalized observations that DDA blooms occur when the mixed layer depth is < 70 m are supported, but there is no consistent relationship between mixed layer depth, bloom intensity, or composition; regional blooms between 22-34°N occur within a broader temperature range (21-26°C) than previously reported. In both years, the Hemiaulus-Richelia and Rhizosolenia-Richelia DDAs increased 10(2)-10(3) over background concentrations within satellite-defined bloom features. The two years share a common trend of Hemiaulus dominance of the DDAs and substantial increases in the >10 μm chl a fraction (～40-90+% of total chl a). Integrated diatom abundance varied 10-fold over <10 km. Biogenic silica concentration tracked diatom abundance, was dominated by the >10 μm size fraction, and increased up to 5-fold in the blooms. The two years differed in the magnitude of the surface chl a increase (2009>2008), the abundance of pennate diatoms within the bloom (2009>2008), and the substantially greater mixed layer depth in 2009. Only the 2009 bloom had sufficient chl a in the >10 μm fraction to produce the observed ocean color chl increase. Blooms had high spatial variability; ocean color images likely average over numerous small events over time and space scales that exceed the individual event scale. Summertime DDA export flux noted at the Hawaii time-series Sta. ALOHA is probably a generalized feature of the eastern N. Pacific north to the subtropical front.     

The Cenozoic diatom zonation and its significance for stratigraphic correlations in the North Pacific

The current state of the North Pacific Cenozoic diatom zonation is reviewed. The high resolution of diatom zonation is shown, which is comparable to that of groups of calcareous planktonic microfossils. The significance of diatom assemblages for the dating and correlation of various Tertiary marine sediments in the North Pacific is discussed. Recent examples of subdivision of the Oligocene-Neogene sequences of this region and dating of geological events on the zonal basis are given.     

Epipelagic siphonophore assemblages associated with water masses along a transect between Chile and Easter Island (eastern South Pacific Ocean)

We analyze for the first time the spatial distribution of siphonophoresin relation to water masses along a 3750-km oceanic transectbetween the Chilean coast and the Easter Island (27° S),a sector scarcely known of eastern South Pacific Ocean. Thirty-onesiphonophore species were identified; Sulculeolaria turgidaand Vogtia glabra were recorded for the first time in this sector.The most abundant species were Muggiaea atlantica (29.2%), Eudoxoidesspiralis (24.5%) and Lensia subtilis (13.1%). Two differentsiphonophore assemblages east and west of 76 W, associated respectivelywith Subantarctic Water and Subtropical Water masses, can beused as water mass indicators. The former included the threemost abundant species, whereas the latter showed greater speciesrichness. This study provides basic knowledge on spatial distributionof siphonophores, which is important to develop future researchfocused on understanding the ecological role and biologicalprocesses driven by planktonic organisms in the southeasternPacific Ocean.     

Paleoceanographic evolution of North Pacific surface water off Japan during the past 150,000 years

Hydrographic variability in the Mixed Water Region of the Northwest Pacific Ocean at latitudes 35°–40°N, between the Kuroshio Extension and Oyashio Front, causes complex upwelling, leading to large primary productivity and thus great fishery resources. We reconstructed the periodicity of the variability in North Pacific Intermediate Water upwelling and surface ocean hydrography based on the high-resolution analysis of diatom assemblages in seven cores, representing the last 150,000 years. We derived annual sea surface temperatures (SSTs) through a diatom-based proxy (Td′). The Td′-derived annual SSTs (°C) are controlled by orbital forcing, and show a reversed saw-tooth in southern cores, in contrast to a normal saw-tooth pattern in the northern cores. Oceanic diatom abundances along the northern margin of the Mixed Water Region are twice times as high as beneath the axis of the Kuroshio Extension, and fluctuated in a revised saw-tooth pattern with higher overall abundances interglacials. After the last deglaciation, annual SSTs declined markedly during Heinrich and Bond events in the northern North Atlantic, when ice-rafted detritus transported by icebergs was abundant. Wavelet analyses of the record of oceanic diatom abundances show significant variability at 2.0-kyr, 2 to 5.6-kyr and 3.2 to 9.6-kyr periods. Wavelet analyses of the annual SST records show significant periodicity at 1.4 to 2.6-kyr, 3.3 to 4.0-kyr, 7.2 to 12.8-kyr cycles.     

Phytoplankton decline in the eastern North Pacific transition zone associated with atmospheric blocking

Global climate change can significantly influence oceanic phytoplankton dynamics, and thus biogeochemical cycles and marine food webs. However, associative explanations based on the correlation between chlorophyll‐a concentration (Chl‐a) and climatic indices is inadequate to describe the mechanism of the connection between climate change, large‐scale atmospheric dynamics, and phytoplankton variability. Here, by analyzing multiple satellite observations of Chl‐a and atmospheric conditions from National Center for Environmental Prediction/National Center for Atmospheric Research reanalysis datasets, we show that high‐latitude atmospheric blocking events over Alaska are the primary drivers of the recent decline of Chl‐a in the eastern North Pacific transition zone. These blocking events were associated with the persistence of large‐scale atmosphere pressure fields that decreased westerly winds and southward Ekman transport over the subarctic ocean gyre. Reduced southward Ekman transport leads to reductions in nutrient availability to phytoplankton in the transition zone. The findings describe a previously unidentified climatic factor that contributed to the recent decline of phytoplankton in this region and propose a mechanism of the top‐down teleconnection between the high‐latitude atmospheric circulation anomalies and the subtropical oceanic primary productivity. The results also highlight the importance of understanding teleconnection among atmosphere–ocean interactions as a means to anticipate future climate change impacts on oceanic primary production.     

A rapidly deposited pennate diatom ooze in Upper Miocene-Lower Pliocene sediment beneath the North Pacific polar front

Rapidly deposited Thalassionema-Thalassiothrix pennate diatom oozes previously have been described in Upper Miocene-Lower Pliocene sediment beneath the frontal boundary of the eastern equatorial Pacific. Here we document a new occurrence of Thalassionema-Thalassiothrix ooze in Upper Miocene-Lower Pliocene sediment beneath the frontal boundary of the subarctic North Pacific. The ooze is a 6 m interval of siliceous sediment at Ocean Drilling Program (ODP) sites 885/886 that was rapidly deposited between approximately 5.0 and 5.9 Ma. Bulk sediment in this interval may contain greater than 85% pennate diatom tests. There are also abundant laminae and pockets that are composed entirely of Thalassionema and Thalassiothrix diatoms. The presence of a rapidly deposited ooze dominated by pennate diatoms indicates unusual past conditions in the overlying surface waters. Time coincident deposition of such oozes at two distinct frontal boundary locations of the Pacific suggests that the unusual surface water conditions were causally linked to large-scale oceanographic change. This same oceanographic change most likely involved (1) addition of nutrients to the ocean, or (2) redistribution of nutrients within the ocean. The occurrence and origin of pennate diatom oozes may be a key component to an integrative understanding of late Neogene paleoceanography and biogeochemical cycling.     

Genetic structure of the beaked whale genus Berardius in the North Pacific,with genetic evidence for a new species

There are two recognized species in the genus Berardius, Baird's and Arnoux's beaked whales. In Japan, whalers have traditionally recognized two forms of Baird's beaked whales, the common “slate‐gray” form and a smaller, rare “black” form. Previous comparison of mtDNA control region sequences from three black specimens to gray specimens around Japan indicated that the two forms comprise different stocks and potentially different species. We have expanded sampling to include control region haplotypes of 178 Baird's beaked whales from across their range in the North Pacific. We identified five additional specimens of the black form from the Aleutian Islands and Bering Sea, for a total of eight “black” specimens. The divergence between mtDNA haplotypes of the black and gray forms of Baird's beaked whale was greater than their divergence from the congeneric Arnoux's beaked whale found in the Southern Ocean, and similar to that observed among other congeneric beaked whale species. Taken together, genetic evidence from specimens in Japan and across the North Pacific, combined with evidence of smaller adult body size, indicate presence of an unnamed species of Berardius in the North Pacific.     

Long‐term panmixia in a cosmopolitan Indo‐Pacific coral reef fish and a nebulous genetic boundary with its broadly sympatric sister species

Phylogeographical studies have shown that some shallow‐water marine organisms, such as certain coral reef fishes, lack spatial population structure at oceanic scales, despite vast distances of pelagic habitat between reefs and other dispersal barriers. However, whether these dispersive widespread taxa constitute long‐term panmictic populations across their species ranges remains unknown. Conventional phylogeographical inferences frequently fail to distinguish between long‐term panmixia and metapopulations connected by gene flow. Moreover, marine organisms have notoriously large effective population sizes that confound population structure detection. Therefore, at what spatial scale marine populations experience independent evolutionary trajectories and ultimately species divergence is still unclear. Here, we present a phylogeographical study of a cosmopolitan Indo‐Pacific coral reef fish Naso hexacanthus and its sister species Naso caesius, using two mtDNA and two nDNA markers. The purpose of this study was two‐fold: first, to test for broad‐scale panmixia in N. hexacanthus by fitting the data to various phylogeographical models within a Bayesian statistical framework, and second, to explore patterns of genetic divergence between the two broadly sympatric species. We report that N. hexacanthus shows little population structure across the Indo‐Pacific and a range‐wide, long‐term panmictic population model best fit the data. Hence, this species presently comprises a single evolutionary unit across much of the tropical Indian and Pacific Oceans. Naso hexacanthus and N. caesius were not reciprocally monophyletic in the mtDNA markers but showed varying degrees of population level divergence in the two nuclear introns. Overall, patterns are consistent with secondary introgression following a period of isolation, which may be attributed to oceanographic conditions of the mid to late Pleistocene, when these two species appear to have diverged.     

Growth of three plankton diatom species in Oslofjord water in the absence of artificial chelators

Cultures of the plankton diatoms Skeletonema costatum (Greville) Cleve, Thalassiosira nordenskioeldii Cleve, and Lauderia annulata Cleve were grown in sea-water samples collected in the inner Oslofjord on 11 occasions between February, 1976 and January, 1977. The growth experiments were carried out in silicone-coated culture flasks, with nitrate, phosphate, and silicate added in excess, and under standardized conditions of a temperature of 10 °C and a saturating light intensity. Growth rates, as measured during exponential growth over a period of 5–6 days, were, with very few exceptions, close to the maximum rates obtained in a complete medium. The addition of ethylenediaminetetra-acetic acid (EDTA) to the water samples did not lead to improved growth, nor did EDTA have an effect on the initial lag phase. The lack of a seasonal variation in the observed growth responses was in marked contrast to the large fluctuations in the phytoplankton populations in the fjord. These findings give no support to the hypothesis that species successions among marine plankton diatoms are influenced by organic chelators or other extracellular substances produced by planktonic algae.     

Distribution and modification of diatom assemblages in and around a warm core ring in the western North Pacific Frontal Zone east of Hokkaido

Spatial distribution relationships between diatom assemblagesand water types were investigated in and around a 2-year-oldwarm core ring in the western North Pacific Polar Frontal Zoneoff Hokkaido, Japan. From the oceanographic and diatom data,principal component analysis and a clustering technique identifiedfour water types and four diatom assemblages. The BackgroundAssemblage had a low standing stock and was distributed overthe entire study area, including the core water of the ring.This assemblage was associated with water conditions that werenot highly suitable for diatom growth. A Cold Assemblage, probablylinked to submerging Oyashio Water, was found in sub-surfacewaters. Its standing crop was rather high. The two other assemblagesalso had relatively high standing stocks: one, the StratifiedAssemblage, was found around the nutricline in the sub-surfacelayer and the other, the Warm Streamer Assemblage, in a warmstreamer flowing along the outer edge of the warm core ring.We argue here that the Stratified Assemblage emerged from theBackground Assemblage because of favorable local conditions(nutrient level), and, conversely, that in the downstream ofthe warm streamer, the Warm Streamer Assemblage reversed tothe Background Assemblage because the nutrient supply was depleted.     

Planktonic and periphytic bdelloid rotifers from Thailand reveal a species assemblage with a combination of cosmopolitan and tropical species

The dispersal pattern of microorganisms has been a debated topic in the last decade, because for microscopic organisms with dispersing stages, biogeographic barriers may not exist and geographic distances may have little effect on the probability of their occurrence. In this study we tested whether a group of microscopic animals, the bdelloid rotifers, sampled in a tropical country, could indeed be cosmopolitan, strictly tropical, and/or have endemic species. We sampled freshwater habitats throughout Thailand in dry and rainy seasons between 2014 and 2016, focusing on permanent water bodies, where the prevalence of species producing resting stages acting as propagules for dispersal should be minimal and thus dispersal limitation should exist, with several species being narrowly distributed. We used traditional morphological identification, geometric morphometric analyses on the shape and size of the jaws, and DNA taxonomy to identify species and to quantify the morphological and genetic distances of Thai samples in comparison with data on bdelloids from other areas in the world. We found a total of 12 species of planktonic and periphytic bdelloid rotifers, and all approaches we used, qualitative and quantitative, confirmed a group of nine potentially cosmopolitan species already known from other continents, one tropical oriental species, and two new species with a potentially narrow geographic distribution, one of which we here formally describe. We thus support the idea that for microscopic animals the moderate endemicity hypothesis suggested for protists may also hold true: most of the species we found indeed have a wide geographic distribution, but other species with narrower distributions do exist.

http://zoobank.org/urn:lsid:zoobank.org:pub:3DF5A913-BE6A-4EA4-88FD-C38C0F7AE00A     

Pliocene and Pleistocene diatom datum levels related with paleoceanography in the northwest Pacific

Thick sections of Pliocene and Pleistocene biosiliceous clay and ooze were recovered by the Hydraulic Piston Corer (HPC) at three northwest Pacific sites (DSDP Sites 578, 579, and 580). They contain a well-preserved paleomagnetic record which made it possible to evaluate diatom events used in low and high latitudes in the transitional region of the northwest Pacific. Equatorial Pacific events are usually isochronous between the equatorial and subarctic regions. However, species which have short ranges in low latitudes tend to have diachronous first and last appearances in higher latitudes. All subarctic North Pacific datum species are present in the sediments at three sites which lie north and south across the subarctic front, but their ranges become shorter in southern regions. They do not penetrate into the equatorial region. Spatial distributions of these events are influenced by the paleo-position of the subarctic front. The migration of species from their home-area outwards, in the form of the first appearance, is related to the fluctuations of the subarctic front. The last appearance of species is a response to the change of the surface water temperature that is beyond the limit of tolerance of the species, or an unstable oceanic environment due to major change of climate.     

The vertical distributions of chlorophyll and phytoplankton species in the North Pacific central environment

The phytoplankton species in the North Pacific central environmentare known to be distributed into two vertically distinct assemblagesduring most of the year. Key species are defined for each assemblage.The vertical distributions of these key species indicate thatthe increase in abundance of deep species closely parallelsthe increase in chlorophyll a at the top of the chlorophyllmaximum layer. The chlorophyll maximum is comprised of speciescharacteristic of the deep assemblage, with only insignificantnumbers of shallow species.     

A generic revision of the Dorvilleidae (Polychaeta), with six new species from the deep North Pacific

PETER A. JUMARS
The Dorvilleidae are divided into eight genera: Dorvillea, Schistomeringos (new name), Protodorvillea, Meiodorvillea (new genus), Exallopus (new genus), Ophryotrocha, Parophryotrocha , and Apophryotrocha (new genus). Periodic maxillary replacement is found to occur in a manner which makes many often cited maxillary characters taxonomically unreliable. Therefore, the pharyngeal characters of all the type-species are redescribed or newly described. The discovery of new forms and the present interpretation of hard jaw parts permit construction of a phylogenetic scheme with Dorvillea as the most primitive genus containing living species. Suggestions are given for the advantageous use of the phenomenon of maxillary replacement in autecoiogical investigation.
Evidence is presented against the cosmopolitan distribution of Schistomeringos rudolphi , a species often noted in nearshore pollution studies. Newly described species are Dorvillea batia, Schistomeringos mediofurca, Meiodorvillea apalpata, Exallopus cropion, Ophryotrocha profunda , and Apophryotrocha mutabiliseta , all from the deep North Pacific. A key to the genera is provided, as are listings of all the known species within each genus.     

Upper temperature tolerance of North Atlantic and North Pacific geographical isolates ofChondrus species (Rhodophyta)

The upper survival temperature for most isolates ofChondrus crispus from localities ranging from northern Norway and Iceland to Spain, and for an isolate from Nova Scotia, was 28 °C after 2 weeks of exposure to temperatures of 20–31 °C at intervals of 1 °C. An upper survival limit of 29 °C was exhibited by a few European isolates from the English Channel, the North Sea, and one Irish isolate from the upper intertidal. The warm-temperate Japanese speciesC. nipponicus andC. giganteus formaflabellatus survived 30 °C, whereas 29 °C was the upper survival limit for the coldtemperatureC. pinnulatus formapinnulatus from northern Japan. A possible origin ofC. crispus in the north Pacific is discussed.     

Presence of Erwinia carotovora in surface water in North America

Erwinia carotovora was frequently isolated from samples of surface water collected from 66 rivers, springs, creeks, streams, lakes, reservoirs and ponds in 16 states in the US but was not found in the single fresh water sample collected in Canada. The organism was also isolated from water collected from the Pacific Ocean and the Gulf of Mexico. In Colorado and Wyoming, E. carotovora was isolated from water samples nearly every month of the year when monthly samples were collected from several streams. Erwinia carotovora subsp. carotovora represented 98–8% of the strains recovered from the water samples; E. carotovora subsp. atroseptica made up the remainder of the strains; E. chrysanthemi was not found.     

Phytoplankton species structure in the central North Pacific: Is the edge like the center?

Phytoplankton samples were collected on July 14 and 18, 1985from a station 460 km off the coast of northern Baja, California,near the eastern edge of the North Pacific central gyre. Thevertical distributions and species structures at this edge stationare compared with those observed over a 12 year period at astation 900 km north of Hawaii (central station). The edge station is somewhat colder and fresher than the centralstation but the chemical and general biological parameter aresimilar. At both locations, the phytoplankton are divided verticallyinto two assemblages, with a zone of transition near 100 m depth.Neither species composition nor dominance order within the shallowor deep zones at the edge station are significantly differentfrom those at the central station. The spatial differences ona scale of 3200 km are the same as those observed at the centralstation over temporal intervals of 4–5 and 12 years, respectively,in the shallow and deep assemblages.     

Phytoplankton species structure in the central North Pacific 1973-1996: variability and persistence

Acquisition of recent phytoplankton samples from JGOFS' station ALOHA and the Climax area prompted updating and re-evaluation of 23 years of floristic data from the summer central North Pacific environment. Recurrent group analysis clearly shows the dichotomy between shallow and deep associations. A new finding is that the deep flora consists of two related groups of species whose abundance centers are vertically displaced from one another. At the Climax area, the species structure in both shallow and deep strata persisted throughout the study period. Within each stratum, differences in rank orders of species' abundances between station ALOHA and the Climax area are no greater than expected from physical mixing processes. However, abundances of species in the deeper recurrent groups were significantly lower at ALOHA.