Search results for "Photic zone"
showing 10 items of 21 documents
Modern sedimentary analogues and integrated monitoring to understand varve formation in the Mediterranean Lake Montcortès (Central Pyrenees, Spain)
2018
Este artículo contiene 13 páginas, 6 figuras, 1 tabla.
Plankton Tracker: A novel integrated system to investigate the dynamic sinking behavior in phytoplankton
2020
Abstract Phytoplankton sinking is an important property that can determine community composition, affecting nutrient and light absorption in the photic zone, and influencing biogeochemical cycling via material loss to the deep ocean. To date, the difficulty in exploring the sinking processes is partly due to methodological limitations in measuring phytoplankton sinking rate. However, in the last decade, works have illustrated various methods based on some non-invasive and low perturbing approaches (laser scanner, video-microscopy, fluorescence spectroscopy). In this study, we review the methods for sinking rate estimation and describe the Plankton Tracker, a novel integrated system to inves…
Seasonal cycle of benthic denitrification and DNRA in the aphotic coastal zone, northern Baltic Sea
2020
Current knowledge on the seasonality of benthic nitrate reduction pathways in the aphotic, density stratified coastal zone of the Baltic Sea is largely based on data from muddy sediments, neglecting the potential contribution of sandy sediments. To gain a more comprehensive understanding of seasonality in this part of the Baltic Sea coast, we measured rates of benthic denitrification, anammox and dissimilatory nitrate reduction to ammonium (DNRA) monthly in the ice-free period of 2016 in both sandy and muddy aphotic sediments, northwestern Gulf of Finland. No anammox was observed. The seasonal cycle of denitrification in both sediment types was related to the hydrography-driven development …
Novel Autotrophic Organisms Contribute Significantly to the Internal Carbon Cycling Potential of a Boreal Lake
2018
ABSTRACT Oxygen-stratified lakes are typical for the boreal zone and also a major source of greenhouse gas emissions in the region. Due to shallow light penetration, restricting the growth of phototrophic organisms, and large allochthonous organic carbon inputs from the catchment area, the lake metabolism is expected to be dominated by heterotrophic organisms. In this study, we test this assumption and show that the potential for autotrophic carbon fixation and internal carbon cycling is high throughout the water column. Further, we show that during the summer stratification carbon fixation can exceed respiration in a boreal lake even below the euphotic zone. Metagenome-assembled genomes an…
Photoferrotrophy: Remains of an Ancient Photosynthesis in Modern Environments
2017
Photoferrotrophy, the process by which inorganic carbon is fixed into organic matter using light as an energy source and reduced iron [Fe(II)] as an electron donor, has been proposed as one of the oldest photoautotrophic metabolisms on Earth. Under the iron-rich (ferruginous) but sulfide poor conditions dominating the Archean ocean, this type of metabolism could have accounted for most of the primary production in the photic zone. Here we review the current knowledge of biogeochemical, microbial and phylogenetic aspects of photoferrotrophy, and evaluate the ecological significance of this process in ancient and modern environments. From the ferruginous conditions that prevailed during most …
Fine metagenomic profile of the Mediterranean stratified and mixed water columns revealed by assembly and recruitment
2018
Background: The photic zone of aquatic habitats is subjected to strong physicochemical gradients. To analyze the fine-scale variations in the marine microbiome, we collected seven samples from a single offshore location in the Mediterranean at 15 m depth intervals during a period of strong stratification, as well as two more samples during the winter when the photic water column was mixed. We were able to recover 94 new metagenome-assembled genomes (MAGs) from these metagenomes and examine the distribution of key marine microbes within the photic zone using metagenomic recruitment. Results: Our results showed significant differences in the microbial composition of different layers within th…
THE BEHAVIORAL RESPONSE OF AMPHIPODS HARBORING CORYNOSOMA CONSTRICTUM (ACANTHOCEPHALA) TO VARIOUS COMPONENTS OF LIGHT
2006
Many studies have shown that photic behavior of amphipods is subject to parasitic manipulation. However, all these investigations have focused on but one property of light (i.e., intensity). This study investigated the possibility that variable wavelength sensitivity, as a potentially important component of amphipod ecology, is subject to parasitic manipulation. The photic behavior of freshwater amphipods Hyalella azteca, infected with the duck acanthocephalan Corynosoma constrictum, was tested. The phototactic responses of infected and uninfected amphipods to various wavelengths in the visible spectrum were compared, and to delineate the effects of intensity and wavelength on behavior, the…
Responses of microbial food web to increased allochthonous DOM in an oligotrophic subarctic lake
2013
Climate-induced changes in catchment area vegetation and runoff alter the quality and quantity of carbon that enters lakes, with implications for food webs in recipient water bodies. The effect of dissolved organic matter (DOM) on the ratio between heterotrophic and autotrophic biomass and productivity was studied in a subarctic, clear water lake in northern Finland. In a mesocosm experiment, natural DOM from a subarctic bog and a boreal lake was added to the lake water, doubling the initial dissolved organic carbon (DOC) concentration. Optical indices sug- gested that the subarctic DOM addition was more bioavailable, which was in line with the greater increase in bacterial biomass and prod…
Deep-water stromatolites andFrutexites Maslov from the early and Middle Jurassic of S-Germany and Austria
1993
Despite extensive discussions during the last 20 years stromatolites are still used by many geologists as unequivocal indicators of very shallow-water conditions. We investigated four stratigraphic units from the Lower and Middle Jurassic of southern Germany (Posidonien-Schiefer, Amaltheen-Ton) and of the Northern Calcareous Alps (Adneter Kalk, Klauskalk), which were formerly interpreted as shallow marine sediments by some authors due to the occurrence of stromatolites. Our interpretations of the macro-, micro- and ultrafacies of these sediments are not compatible with shallow-water settings. We therefore propose a deep-marine, aphotic origin of these stromatolites. Former interpretations o…
Comparison of thermal stratification, light attenuation and Chlorophyll-a dynamics between the ends of Lake Tanganyika
2002
Thermal structure, light attenuation, and chlorophyll-a dynamics within the upper 100 m at the northern and southern ends of Lake Tanganyika were measured from August 1995–July 1996. Pronounced variability of thermal structure in time, depth and region were observed. During the dry windy season (June–September), the water column in the south was largely isothermal down to 100 m, while in the north stratification was detectable. Subsequently, in October, cessation of winds coincided with a reestablishment and strengthening of thermal stratification in the south, and a distinct rise of a weakened thermocline in the north was accompanied by an increase in epilimnetic concentrations of dissolve…