Coccolithophore diversity and abundance within Levante Bay may be due to (1) slow surface currents that carry upper photic zone
coccolithophores into the bay, with detrimental conditions resulting in assemblage depauperization toward the seeps; or (2) almost complete dissolution of the community at the seep and subsequent dilution further from this area, coupled with the mixing of new surface water from offshore.
The occurrence of Archaias and Peneroplis is typical of recent tropical and subtropical shallow-water environments [42,34] and are characteristics of the upper part of the upper photic zone
The system allows automatically real-time observation and recording in dynamical culture process through circular photic zone
, which facilitates light irradiation and benefits the microscopic observation.
Canonical Correspondence Analyses confirmed a correlation between higher diatom densities and the increased photic zone
following macrophyte removal.
Through this study, we show that biomarker distributions differ only slightly among the samples, which strongly suggests that differences in [[delta].sup.13][C.sub.kerogen] are related to the difference in [[delta].sup.13]C of C[O.sub.2] in the photic zone
. Therefore, in the Toarcian, the ocean-atmosphere system was subject to one of the largest perturbations of the carbon cycle in the last 250 Myr known as the Toarcian Oceanic Anoxic Event (TOAE) .
This research not only provides the first clear evidence that microorganisms were directly involved in the deposition of Earth's oldest iron formations; it also indicates that large populations of oxygen-producing cyanobacteria were at work in the shallow areas of the ancient oceans, while deeper water still reached by the light (the photic zone
) tended to be populated by anoxyenic or micro-aerophilic iron-oxidizing bacteria which formed the iron deposits.
"These data strongly suggest that oxygenic photoautotrophs flourished in the photic zone
of the 3.46 billion-year-old oceans and supplied molecular oxygen to the deep water," said the researchers.
transport from bottom layers to the photic zone
(Holdren & Armstrong, 1980; Moore et al., 1991; Haggard et al., 2005).
Water samples were collected from the photic zone
at each of the three locations on the following day using an integrated sampler fitted with 80-[micro]m mesh Nytex[R] on the inlet, so as to exclude zooplankton.
The photic zone
extends to approximately the base of the wall.
Secchi disk readings were also taken to ensure that the mesocosm depths were consistently in the photic zone
. After abiotic measurements were taken, the mesocosm bags were stirred to evenly distribute the zooplankton and algal populations.
This productivity is due to the upwelling of cold, nutrient rich waters to the photic zone
where it is taken up by primary producers--particularly, large diatoms.