Phytoplankton are the autotrophic components of the plankton community and a key part of oceans and freshwater basin ecosystems. The name comes from the Greek words φυτόν, meaning "plant", πλαγκτός, meaning "wanderer" or "drifter". Most phytoplankton are too small to be individually seen with the unaided eye. However, when present in high enough numbers, some varieties may be noticeable as colored patches on the water surface due to the presence of chlorophyll within their cells and accessory pigments in some species. About 1% of the global biomass is due to phytoplankton. Phytoplankton are diverse, varying from photosynthesising bacteria, to plant-like diatoms, to armour-plated coccolithophores. Phytoplankton are photosynthesizing microscopic biotic organisms that inhabit the upper sunlit layer of all oceans and bodies of fresh water on Earth, they are agents for "primary production", the creation of organic compounds from carbon dioxide dissolved in the water, a process that sustains the aquatic food web.
Phytoplankton obtain energy through the process of photosynthesis and must therefore live in the well-lit surface layer of an ocean, lake, or other body of water. Phytoplankton account for about half of all photosynthetic activity on Earth, their cumulative energy fixation in carbon compounds is the basis for the vast majority of oceanic and many freshwater food webs. While all phytoplankton species are obligate photoautotrophs, there are some that are mixotrophic and other, non-pigmented species that are heterotrophic. Of these, the best known are dinoflagellate genera such as Noctiluca and Dinophysis, that obtain organic carbon by ingesting other organisms or detrital material. Phytoplankton are crucially dependent on minerals; these are macronutrients such as nitrate, phosphate or silicic acid, whose availability is governed by the balance between the so-called biological pump and upwelling of deep, nutrient-rich waters. Phytoplankton nutrient composition drives and is driven by the Redfield ratio of macronutrients available throughout the surface oceans.
However, across large regions of the World Ocean such as the Southern Ocean, phytoplankton are limited by the lack of the micronutrient iron. This has led to some scientists advocating iron fertilization as a means to counteract the accumulation of human-produced carbon dioxide in the atmosphere. Large-scale experiments have added iron to the oceans to promote phytoplankton growth and draw atmospheric CO2 into the ocean. However, controversy about manipulating the ecosystem and the efficiency of iron fertilization has slowed such experiments. Phytoplankton depend on B Vitamins for survival. Areas in the ocean have been identified as having a major lack of some B Vitamins, correspondingly, phytoplankton; the effects of anthropogenic warming on the global population of phytoplankton is an area of active research. Changes in the vertical stratification of the water column, the rate of temperature-dependent biological reactions, the atmospheric supply of nutrients are expected to have important effects on future phytoplankton productivity.
The effects of anthropogenic ocean acidification on phytoplankton growth and community structure has received considerable attention. Phytoplankton such as coccolithophores contain calcium carbonate cell walls that are sensitive to ocean acidification; because of their short generation times, evidence suggests some phytoplankton can adapt to changes in pH induced by increased carbon dioxide on rapid time-scales. Phytoplankton serve as the base of the aquatic food web, providing an essential ecological function for all aquatic life. Under future conditions of anthropogenic warming and ocean acidification, changes in phytoplankton mortality may be significant. One of the many food chains in the ocean – remarkable due to the small number of links – is that of phytoplankton sustaining krill, which in turn sustain baleen whales; the term phytoplankton encompasses all photoautotrophic microorganisms in aquatic food webs. However, unlike terrestrial communities, where most autotrophs are plants, phytoplankton are a diverse group, incorporating protistan eukaryotes and both eubacterial and archaebacterial prokaryotes.
There are about 5,000 known species of marine phytoplankton. How such diversity evolved despite scarce resources is unclear. In terms of numbers, the most important groups of phytoplankton include the diatoms and dinoflagellates, although many other groups of algae are represented. One group, the coccolithophorids, is responsible for the release of significant amounts of dimethyl sulfide into the atmosphere. DMS is oxidized to form sulfate which, in areas where ambient aerosol particle concentrations are low, can contribute to the population of cloud condensation nuclei leading to increased cloud cover and cloud albedo according to the so-called CLAW Hypothesis. Different types of phytoplankton support different trophic levels within varying ecosystems. In oligotrophic oceanic regions such as the Sargasso Sea or the South Pacific Gyre, phytoplankton is dominated by the small sized cells, called picoplankton and nanoplankton composed of cyanobacteria and picoeucaryotes such as Micromonas. Within more productive ecosystems, dominated by upwelling or high terrestrial inputs, larger dinoflagellates are the
Jeunes filles en serre chaude is a 1934 novel by the French author Jeanne Galzy. Its protagonists are young women at the École normale supérieure de jeunes filles in Sèvres, a suburb of Paris, at the time a girls-only school; the school, which Galzy herself attended, trained girls as teachers for the secondary education system. The background for the events in the novel is the 50th anniversary of the secondary school system for women. Following Burnt Offering and Les Démons de la solitude, it is the third novel by Galzy to explore lesbian desire; the intergenerational love in the novel is a reflection of Galzy's own experiences. The school was reputed to be a "breeding ground of homosexual relationship", had earlier been the subject of a novel exploring same-sex desire, Les Sévriennes by Gabrielle Reval. Like most of Galzy's novels, Jeunes filles is neglected by modern readers, though it did attract some attention at the time of publication. A French reviewer remarked that the novel shows that "overworked brains" sometimes fall prey to "dangerous aberrations".
A brief note in The Modern Language Journal remarked that "trivial but intensely human emotional reactions are realistically depicted", the 1935 New International Year Book warned that the students depicted in the book have a "strong emotional reaction of an undesirable nature". The book is no longer in print.
Rocky Ford is a town in Screven County, United States. The population was 186 at the 2000 census; the community was named after a rocky ford over the nearby Ogeechee River. Rocky Ford is located at 32°39′51″N 81°49′42″W. According to the United States Census Bureau, the town has a total area of 1.2 square miles, of which 1.2 square miles is land and 0.04 square miles is water. As of the census of 2000, there were 186 people, 78 households, 53 families residing in the town; the population density was 153.6 people per square mile. There were 88 housing units at an average density of 72.7 per square mile. The racial makeup of the town was 31.72 % African American. There were 78 households out of which 23.1% had children under the age of 18 living with them, 52.6% were married couples living together, 14.1% had a female householder with no husband present, 30.8% were non-families. 29.5% of all households were made up of individuals and 21.8% had someone living alone, 65 years of age or older. The average household size was 2.38 and the average family size was 2.94.
In the town, the population was spread out with 21.5% under the age of 18, 5.9% from 18 to 24, 23.1% from 25 to 44, 28.5% from 45 to 64, 21.0% who were 65 years of age or older. The median age was 44 years. For every 100 females, there were 84.2 males. For every 100 females age 18 and over, there were 80.2 males. The median income for a household in the town was $25,000, the median income for a family was $28,750. Males had a median income of $28,125 versus $21,719 for females; the per capita income for the town was $12,989. About 4.2% of families and 9.3% of the population were below the poverty line, including 18.8% of those under the age of eighteen and 10.5% of those sixty five or over. List of towns in Georgia Media related to Rocky Ford, Georgia at Wikimedia Commons