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Sulfide oxidizing bacterial mats are common in regions of the continental shelves characterized by high primary production and the resultant oxygen minimum zone. These mats are made up of several species of Beggiatoa and/or Thioploca, which oxidize sulfide that is generated in the sediment. Thioploca spp. inhabit a large polysaccharide sheath that encompasses bundles of 1-20 filaments (trichomes), each ranging from 3 to 60 μm in diameter. This sheath has been shown to be a critical component of the autecology of Thioploca. Analysis of Thioploca from cold seeps in Monterey Bay using light and transmission electron microscopy identified new and diverse microbial assemblages associated with interstitial spaces between trichomes, inside the sheath. Small diameter, non-vacuolate, filamentous prokaryotes were numerous. Amoebae, euglenozoa, ciliates and other protists of unknown affiliation were observed in sheaths. Most of the protists possessed food vacuoles and some protists showed ultrastructural evidence of endosymbionts. These observations suggest that Thioploca sheaths may serve as oases on the sea floor, providing nutritional and detoxification services to previously unrecognized microbial partners. [ABSTRACT FROM AUTHOR]

The utility of alkenone abundance and U37K′ ratios as proxies for haptophyte productivity and temperature variations, respectively, was examined in an upwelling setting by comparison of alkenones with other environmental variables including carbon concentrations, plankton populations, productivity, and temperature. Suspended particulate organic material (SPOM) was collected from surface waters (1–5 m) in Monterey Bay, California during the 1992 El Nin˜o. Haptophyte algae comprise a small but significant fraction of the plankton assemblage (0.5–30%). In this upwelling environment either the haptophytes contain low cellular abundances of alkenones (0.4–5% Corg) and/or alkenone producers are weakly represented among their populations. The U37K′-temperature relationship for SPOM exhibits a better correlation (r2=0.870; n=8) during periods of active upwelling and in the winter than throughout the entire annual cycle (r2=0.308; n=18). The alkenone-based temperatures also suggest, as observed elsewhere, that these compounds originated in colder waters at depth and were subsequently transferred to surface waters. [Copyright &y& Elsevier]

Presents a study which examined sediments collected from seeps in California for the presence of benthic foraminifera. Methods Results; Discussion.

Reports on the eukaryotic community of the Santa Barbara Basin in California. Support of an abundant protistan and metazoan meiofaunal community; The presence of prokaryotic symbionts; and microaerophile and anaerobic taxa; Opportunities for the testing of symbiosis hypotheses of eukaryogensis.

Provides information on a study which reported the biodiversity of nanoflagellates in central California waters. Materials and methods of the study; Classification of primitive green algae; Discussion on prasinophycean taxa.

Examines the external morphology and ultrastructure of an autotrophic athecate dinoflagellate cyst from Antarctic sea ice. Storage bodies and cell wall; Maximum abundances observed; Role that the formation of the cyst may play in the ecology of sea ice communities.

We report the finding of two species of Mantoniella from the Weddell Sea and Prydz Bay. Antarctica. As well as M. squamata, a cosmopolitan species, we describe M. Antarctica sp. Nov., the second species in this genus. M. Antarctica is covered with two distinctive types of discoid scales. The flagella bear only the smaller of the scale types whereas the cell body has both types, the larger overlying the smaller. [ABSTRACT FROM AUTHOR]

A significant amount of the primary production in the Southern Ocean and other ice-covered oceans takes place in localized ice edge plankton blooms. The dynamics of these blooms appear to be closely related to seasonal melting of sea ice. Algal cells released from the ice are a possible source of ice edge planktonic assemblages, but evidence for this "seeding" has been equivocal. We compared algal assemblages in ice and water in the Weddell Sea during the austral spring of 1983 at a receding ice edge with a well-developed ice edge bloom. The high degree of similarity between ice and water column assemblages, the spatial and temporal patterns in the distribution and abundances of species, and preliminary evidence for the viability and growth of ice-associated species provide evidence for seeding from sea ice of some species in Antarctica. [ABSTRACT FROM AUTHOR]

The influence of ocean acidification in deep-sea ecosystems is poorly understood but is expected to be large because of the presumed low tolerance of deep-sea taxa to environmental change. We used a newly developed deep-sea free ocean CO2 enrichment (dp-FOCE) system to evaluate the potential consequences of future ocean acidification on the feeding behavior of a deep-sea echinoid, the sea urchin, Strongylocentrotus fragilis. The dp-FOCE system simulated future ocean acidification inside an experimental enclosure where observations of feeding behavior were performed. We measured the average movement (speed) of urchins as well as the time required (foraging time) for S. fragilis to approach its preferred food (giant kelp) in the dp-FOCE chamber (-0.46 pH units) and a control chamber (ambient pH). Measurements were performed during each of 4 trials (days -2, 2, 24, 27 after CO2 injection) during the month-long period when groups of urchins were continuously exposed to low pH or control conditions. Although urchin speed did not vary significantly in relation to pH or time exposed, foraging time was significandy longer for urchins in the low-pH treatment. This first deep-sea FOCE experiment demonstrated the utility of the FOCE system approach and suggests that the chemosensory behavior of a deep-sea urchin may be impaired by ocean acidification. [ABSTRACT FROM AUTHOR]

Sequestration of carbon dioxide (CO2) in the ocean is being considered as a feasible mechanism to mitigate the alarming rate in its atmospheric rise. Little is known, however, about how the resulting hypercapnia and ocean acidification may affect marine fauna. In an effort to understand better the protistan reaction to such an environmental perturbation, the survivorship of benthic foraminifera, which is a prevalent group of protists, was studied in response to deep-sea CO2 release. The survival response of calcareous, agglutinated, and thecate foraminifera was determined in two experiments at ∼3.1 and 3.3 km water depth in Monterey Bay (California, USA). Approximately 5 weeks after initial seafloor CO2 release, in situ incubations of the live–dead indicator CellTracker Green were executed within seafloor-emplaced pushcores. Experimental treatments included direct exposure to CO2 hydrate, two levels of lesser exposure adjacent to CO2 hydrate, and controls, which were far removed from the CO2 hydrate release. Results indicate that survivorship rates of agglutinated and thecate foraminifera were not significantly impacted by direct exposure but the survivorship of calcareous foraminifera was significantly lower in direct exposure treatments compared with controls. Observations suggest that, if large scale CO2 sequestration is enacted on the deep-sea floor, survival of two major groups of this prevalent protistan taxon will likely not be severely impacted, while calcareous foraminifera will face considerable challenges to maintain their benthic populations in areas directly exposed to CO2 hydrate. [ABSTRACT FROM AUTHOR]

Reports that differences in the type of resting stages became apparent while examining three species of endemic Antarctic diatoms. Eucampia balaustium Castracane; Odontella weissflogii Grunow; O. litigiosa Hoban; Presence of girdle bands in all three species; Presence of morphologic similarities which may indicate taxonomic relationships.

Among eukaryotes, four major phytoplankton lineages are responsible for marine photosynthesis; prymnesiophytes, alveolates, stra- menopiles, and prasinophytes. Contributions by individual taxa, however, are not well known, and genomes have been analyzed from only the latter two lineages. Tiny "picoplanktonic" members of the prymnesiophyte lineage have long been inferred to be ecologically important but remain poorly characterized. Here, we examine pico-prymnesiophyte evolutionary history and ecology using cultivation-independent methods. 185 rRNA gene analysis showed pico- prymnesiophytes belonged to broadly distributed uncultivated taxa. Therefore, we used targeted metagenomics to analyze uncultured picoprymnesiophytes sorted by flow cytometry from sub-tropical North Atlantic waters. The data reveal a composite nuclear-encoded gene repertoire with strong green-lineage affiliations, which contrasts with the evolutionary history indicated by the plastid genome. Measured pico-prymnesiophyte growth rates were rapid in this region, resulting in primary production contributions similar to the cyanobacterium Prochiorococcus. On average, pico-prymnesiophytes formed 25% of global. picophytoplankton biomass, with differing contributions in five biogeographical provinces spanning tropical to subpolar systems. Elements likely contributing to success include high gene density and genes potentially involved in defense and nutrient uptake. Our findings have implications reaching beyond picoprymnesiophytes, to the prasinophytes and stramenopiles. For example, prevalence of putative Ni-containing superoxide dismutases (SODs), instead of Fe-containing SODs, seems to be a common adaptation among eukaryotic phytoplank- ton for reducing Fe quotas in low-Fe modern oceans. Moreover, highly mosaic gene repertoires, although compositionally distinct for each major eukaryotic lineage, now seem to be an underlying facet of successful marine phytoplankton. [ABSTRACT FROM AUTHOR]

Deep-sea Bathymodiolus mussels, depending on species and location, have the capacity to host sulfuroxidizing (thiotrophic) and methanotrophic eubacteria in gill bacteriocytes, although little is known about the mussels' mode of symbiont acquisition. Previous studies of Bathymodiolus host and symbiont relationships have been based on collections of nonoverlapping species across wide-ranging geographic settings, creating an apparent model for vertical transmission. We present genetic and cytological evidence for the environmental acquisition of thiotrophic endosymbionts by vent mussels from the Mid-Atlantic Ridge. Open pit structures in cell membranes of the gill surface revealed likely sites for endocytosis of free-living bacteria. A population genetic analysis of the thiotrophic symbionts exploited a hybrid zone where two Bathymodiolus species intergrade. Northern Bathymodiolus azoricus and southern Bathymodiolus puteoserpentis possess species-specific DNA sequences that identify both their symbiont strains (internal transcribed spacer regions) and their mitochondria (ND4). However, the northern and southern symbiont-mitochondrial pairs were decoupled in the hybrid zone. Such decoupling of symbiont-mitochondrial pairs would not occur if the two elements were transmitted strictly vertically through the germ line. Taken together, these findings are consistent with an environmental source of thiotrophic symbionts in Bathymodiolus mussels, although an environmentally "leaky" system of vertical transmission could not be excluded. [ABSTRACT FROM AUTHOR]