Phytoplankton responses to marine climate change – an introduction

Phytoplankton are one of the key players in the ocean and contribute approximately 50% to global primary production. They serve as the basis for marine food webs, drive chemical composition of the global atmosphere and thereby climate. Seasonal environmental changes and nutrient availability naturally influence phytoplankton species composition. Since the industrial era, anthropogenic climatic influences have increased noticeably – also within the ocean. Our changing climate, however, affects the composition of phytoplankton species composition on a long-term basis and requires the organisms to adapt to this changing environment, influencing micronutrient bioavailability and other biogeochemical parameters. At the same time, phytoplankton themselves can influence the climate with their responses to environmental changes. Due to its key role, phytoplankton has been of interest in marine sciences for quite some time and there are several methodical approaches implemented in oceanographic sciences. There are ongoing attempts to improve predictions and to close gaps in the understanding of this sensitive ecological system and its responses

Heterotrophic bacteria from brackish water of the Southern Baltic Sea: biochemical and molecular identification and characterisation

Six bacterial strains isolated from the surface water of the southern Baltic Sea were described on the basis of their morphological, physiological and biochemical features, and were classified on the basis of 16S rDNA sequence analysis. Comparative analyses of the 16S rDNA sequences of five of the six bacterial strains examined displayed a ≥98% similarity to the sequences available in the NCBI GenBank. The 16S rDNA sequence of strain 2 shared only a 96% similarity with other published sequences, which suggests that this is a new, hitherto unknown species. The isolated heterotrophic bacteria belong to the families Bacillaceae (strain 1), Flexibacteriaceae (strain 2), Sphingomonadaceae (strains 3, 5), Micrococcaceae (strain 4) and Aurantimonadaceae (strain 6). This is the first study in which the polyphasic approach has been applied to the identification of heterotrophic bacteria from the brackish waters of the Gulf of Gdańsk and Gdańsk Deep

Microbial communities in Messinian evaporite deposits of the Vena del Gesso (northern Apennines, Italy).

The Vena del Gesso (Northern Apennines) is a 230 m-thick succession consisting of up to 16 gypsum-shale cycles belongingto the \u201cLower Evaporites\u201d formed during the Messinian salinity crisis in theMediterranean. The study of the microbial communitiespreserved in the gypsum crystals of one complete cycle (6th cycle at Monte Tondo quarry) showed abundant, regularly arranged filamentous forms that resemble morphologically modern obligate phototrophes, cyanobacteria colonizing modern photic, shallow-water gypsum basins.At least four different bacterial populations have been recognized:a) filamentous type cyanobacteria with characteristic inserted funnel shaped structure resembling the modern Scytonematacean;b) Type 1 organisms consisting of filamentous structures impregnated by clay minerals containing pyrite grains in the outer sheath;c) Type 2 filaments filled by clay minerals with dolomite in the outer sheath;d) Type 3 filamentous organisms with a central hollow tube and an encrusted outer sheath mainly composed of calcium carbonate.These organisms were probably associated with other heterotrophic bacteria as suggested by the presence of dolomite and pyrite structures.The size and preservation suggest that most of these cyanobacteria were likely conducting oxygenic photosynthesis as presently observed in modern solar salt works. It follows that they were living in shallow water settings or settled down from the water column to the bottom of a relatively deep evaporite basin

Opportunistic cyanobacteria in benthic microbial mats of a tropical lagoon, Tikehau Atoll, Tuamotu Archipelago : minor in natural populations, major in cultures

Studies in microbial ecology focus on identifying field dominant microbial populations using culture independent tools, whereas minor populations are often ignored. We characterized the cyanobacterial populations from the Tikehau Atoll lagoon, Tuamotu Archipelago, which responded to standard culturing media. The cultivation approach recruited cryptic cyanobacterial taxa, which were not observed in the studied mats, as revealed by microscopic comparison. Twelve strains belonging to the unicellular genera (Aphanothece NAGELI, Chlorogloea WILLE and Cyanocystis BORZI) and the filamentous cyanobacteria with narrow filaments (Leptolyngbya ANAGNOSTIDIS et KOMAREK, Phormidium KUZING ex GOMONT and Pseudanabaena LAUTERBORN) dominated the cultures. The genera Cyanocystis and Chlorogloea were genotypically characterized for the first time. Four strains assigned to Phormidium showed 100% identity using 16S rRNA sequences but additional gene analyses as well as phenotypic distinctions suggest finer differentiation within this group. Eight cyanobacterial strains out of twelve fixed dinitrogen with rates ranging from 3.3 up to 15.8 nmoles N-2 mu g(-1) Chl-a h(-1) and their nitrogen fixation ability was further confirmed by molecular detection of nifH gene. Nine strains possessed phycoerythrin, and two performed complementary chromatic adaptation. The present study documented the existence of an autochthonous subdominant cyanobacterial assemblage with variable physiological features that may enable them to replace dominant species in the microbial mats of Tikehau Atoll lagoon. These minor populations may be ecologically important, particularily in case of environmental disturbances

Ribosomal RNA gene fragments from fossilized cyanobacteria identified in primary gypsum from the late Miocene, Italy

Earth scientists have searched for signs of microscopic life in ancient samples of permafrost, ice, deep-see sediments, amber, salt and chert. Until now evidence of cyanobacteria were notreported in any studies of ancient DNA. Here we investigate morphologically, biochemically and genetically primary evaporites deposited in situ during the late Miocene (Messinian) Salinity Crisis from the north-eastern Apennines of Italy. The evaporites contain fossilized bacterial structures having identical morphological forms as modern biota.We successfully extracted and amplified genetic material belonging to ancient cyanobacteria from gypsum crystals dating back to 5.910-5.816 million years ago, when the Mediterraneanbecame a giant hypersaline brine pool. This finding represents the oldest ancient cyanobacterial DNA to date. Our clone library and its phylogenetic comparison with present cyanobacterialpopulations point to a marine origin for the depositional basin. Our investigation opens the possibility to include fossil cyanobacterial DNA into the paleo-reconstruction of variousenvironments and could also be used to quantify the ecological importance of cyanobacteria through geological time. These serve as biosignatures providing important clues about ancientlife and begin new discussion concerning the debate on the origin of late Miocene evaporites in the Mediterranean

THE OLDEST RIBOSOMAL RNA GENE FRAGMENTS OF CYANOBACTERIA IDENTIFIED IN PRIMARY GYPSUM FROM THE LATE MIOCENE, ITALY

Earth scientists have searched for signs of microscopic lifein ancient samples of permafrost, ice, deep-see sediments,amber, salt and chert. Until now cyanobacteria were notreported in any studies of ancient DNA. We investigatemorphologically, biochemically and genetically the depositionof in situ, primary evaporites deposited during thelate Miocene (Messinian) Salinity Crisis from the northeasternApennines of Italy. The evaporites contain fossilizedcharacteristic filamentous structures that remainintact as long as the sulphate deposits are not altered andclearly evident within preserved crystals having identicalmorphological forms as modern biota from hypersalinesettings (bacteria, cyanobacteria and algae). Althoughstudies of ancient DNA are complicated by the extremesensitivity of analytical techniques to DNA contamination,requiring adequate test procedures for both experimentaland authentication methodology, we successfully extractedand amplified genetic material belonging to ancientcyanobacteria from gypsum crystals dating back to 5.910-5.816 million years ago, when the Mediterranean becamea giant hypersaline brine pool. These cyanobacterial rRNAsequences represent the oldest known cyanobacterial DNAever isolated. The age of this DNAis inferred from the primarynature of the host crystals, and the lack of contaminationin any of the sampled crystals.Our clone library andits phylogenetic comparison with present cyanobacterialpopulations point to a marine origin for the depositionalbasin. We also demonstrate here that genetic signals ofcyanobacterial 16S rDNA and bacterial 16S rDNA can bepreserved in gypsum deposits. This means that the primaryselenite may act as effective seal for materials trapped duringtheir growth. Several previous studies isolated sporeformingmicrobes that could be thought to survive suchlong-term suspension as cryptobiotic spores using bothancient halite and amber, but no previous studies havebeen done using gypsum crystals. Our investigation opensthe possibility of including cyanobacteria and their DNAinto paleo-reconstruction of various environments. Theseserve as biosignatures providing important clues aboutancient life and begin new discussion concerning the possibilityto use terrestrial evaporite settings as analogues ofhydrated sulfate deposits documented on the surface ofMars