Spelling suggestions: "subject:"planktonic communities""
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Coccolithophorid communities in the North-East AtlanticJordan, Richard William January 1988 (has links)
Caccolithopliorids are important members of phytoplankton communities in most parts of the world's oceans. The formation, release and flux of the calcite scales (coccoliths) of these organisms over millions of years, has led to sedimentary deposits of great geological significance. The reporting of immense blooms of coccolithophorids by satellite photography and their passible involvement in atmospheric sulphur emissions has emphasised the necessity for further information on their distribution and ecology. During an extensive sampling programme in the N.E. Atlantic, water samples were collected throughout the photic zone at 30 stations. Scanning electron microscopy of filtered water samples enabled coccolithophorid family and species distributions to be compiled. It was found that certain species assemblages could be assigned to distinct biogeographic zones and that these zones closely conformed to the movements of the N. Atlantic surface currents. However, at the Azores Front it was shown that a transitional region existed between the cold and warm water masses, where the flora of each zone could be found. Detailed studies of coccolithophorid vertical distribution has shown that most species can be assigned to discrete depth bands within the euphotic zone. Furthermore, it was noticed that in two species which have no depth preference, the degree of calcification increased with depth. One of these species, E. huxleyi, displayed two ecomorphotypic variants differing in their calcification, size and morphology. During two east to west transects it was noticed that the halocaccolitiiophorid numbers increased towards the Mid-Atlantic Ridge. A number of new species are described and current taxonomic problems reviewed.
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Laboratory and field investigations into the feeding performance of the Lake Malawi oreochromisHartnell, Robert Massey January 1996 (has links)
No description available.
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Spatio-temporal patterns of biophysical parameters in a microtidal, bar-built, subtropical estuary of the Gulf of MexicoGable, George M., IV 15 May 2009 (has links)
Plankton communities are influenced, in part, by water exchange with adjacent
estuarine and oceanic ecosystems. Reduced advective transport through tidal passes or
with adjacent bay systems can affect chemical processes and biological interactions,
such as nutrient cycling, phytoplankton abundance and productivity, community
respiration, and zooplankton biovolume. The most threatened estuarine ecosystems are
shallow, bar-built, microtidal estuaries with small water volumes and restricted
connections through tidal passes and other water exchange points.
This research explored spatio-temporal trends in plankton communities and the
physicochemical environment in Mesquite Bay, Texas a microtidal, bar-built,
subtropical estuary in the Gulf of Mexico. This research couples sampling at fixedstations
for multiple physical and biological parameters with high-resolution spatial
mapping of physicochemical parameters.
Spatial trends were less in magnitude and affected fewer parameters in fixed station
and spatial data. Two dimensional ordination plots indicated spatial heterogeneity with a
more pronounced temporal trend affecting parameters including temperature, salinity as a function of inflow timing, and seasonal wind direction affecting primary production
and zooplankton biovolume.
Temperature was positively correlated with gross production and respiration rates
during spring and late summer with sporadic positive and negative correlations with
phytoplankton biomass. The timing and magnitude of freshwater inflow affected
various physicochemical and biological parameters. Higher than 71-year inflow rates
resulted in low salinity system wide, with spatial heterogeneity increasing over the
course of the study, which was confirmed by spatial maps. Additionally, high inflow
rates led to two periods of increased inorganic nutrients and dissolved organic matter.
Low salinity periods coincided with persistence of higher turbidity, likely because of
decreased sediment flocculation. Gross production was low at this time, and likely from
light limitation. Additionally, wind magnitude and direction created spatial
heterogeneity in turbidity levels and phytoplankton biomass. Zooplankton biovolume
was highest during spring and late summer with high species diversity in total rotifers.
Copepod biovolume and phytoplankton biomass were positively correlated. Other
zooplankton taxonomic groups exhibited variable correlations with phytoplankton
biomass and other taxonomic groups. Further long-term studies are needed to determine
interactions of various components of trophic food-webs and account for interannual
variability in all system parameters.
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