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A new method of determining the efficiency of towed plankton samplersGilfillan, Edward Smith January 1967 (has links)
In recent years interest has increased concerning the accuracy with which collections made with plankton samplers describe the size and species composition of zooplanktonic communities. The indications are that errors arising from the avoidance of sampling devices by zooplankton may be important, especially when precise data are required.
A model is proposed to describe the processes by which zooplanktonic organisms escape or avoid a sampler in terms of the radius of the mouth of the sampler, the speed at which it is towed, the effective speed the organisms can attain in order to escape, and the distance at which the organisms can detect the sampler. The model is capable of being fitted to field data to provide a curve of percentage catch plotted against speed of towing. The results presented indicate that the model gives a good representation of the processes of biological escapement. Implications of the results are embodied in recommendations respecting the design of plankton samplers. / Science, Faculty of / Zoology, Department of / Graduate
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Relation of freshwater plankton productivity to species composition during induced successionsDickman, Michael David January 1968 (has links)
The species composition, primary productivity and relative
abundance of the plankton organisms in Marion Lake, British Columbia
were recorded at biweekly intervals for two months following artificial
enrichment with nitrate or phosphate or both, of six large wooden
enclosures within the lake in four seasons during the year.
Enrichment resulted initially in a decrease in diversity and
an increase in the productivity of the phytoplankton and standing
crop of the entire plankton community. These events were collectively
termed a "regressive succession" because their "direction" of change
was the reverse of that normally encountered in primary and secondary
successions. The regressive succession terminated following algal
bloom formation, and diversity began to increase slowly while the
primary productivity and standing crop of the plankton dropped. This
was indicative of the beginning of a secondary succession in which one
group of dominant species was replaced by another and then others in
turn replaced these.
This successional pattern occurred regardless of season, prevailing
physical, chemical, or climatological factors. Thus, such a pattern
appeared to be a very general one and was disrupted only by the physical
removal of the majority of the planktonic species from the lake resulting
from persistent and heavy rains which "flushed" the lake.
A statistical analysis of each of the 167 euplankton species
observed in the lake was performed using the data from each of the
four enrichment series to determine which species responded significantly
to artificial enrichment. The individual response patterns were nearly
as diverse as the species themselves, however, one of the most common
responses was made by very rare species which "bloomed" two to three
weeks after nutrient addition. Few primary producers responded to
more than one type of nutrient enrichment in any one season which
emphasized the importance of Liebig’s Law of the Minimum. The higher
trophic levels, on the other hand, responded more to the increase in
standing crop in the different enclosures than to any one particular
type of nutrient enrichment.
The Shannon-Weaver formula, H =nP, log P, was modified by
changing the definition of Pi, that is, the individuals in the ith
species divided by the total number in the sample. This index was
insensitive to changes in the relative abundance of the planktonic
species from the higher trophic levels. Pi was redefined so that it
was less sensitive to number and more sensitive to both relative biomass
and relative productivity. This new index of diversity (Hp ) did not
act selectively on the different trophic levels represented in the
plankton samples.
An understanding of the principles governing community organization
and biotic succession should be based on the life history of the
individual species comprising the community and not on assumptions
about supposed trophic changes. This study indicated that pertinent
information about the changes in the structure of a planktonic community
could be gained from an analysis of the changes in the relative abundance
of each of the species without artificially isolating and culturing these
species and without lumping all the organisms into vague trophic
categories. / Science, Faculty of / Zoology, Department of / Graduate
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Plankton and nutrient ecology of the Columbia River estuaryHaertel, Lois Steben 24 July 1969 (has links)
Monthly samples of nutrients, phytoplankton and zooplankton
were taken in the Columbia River estuary over a period of 16 months
in order to determine distribution with season and salinity, and interrelationships
between plankton and nutrients.
Nitrate and phosphate levels in the river water entering the
estuary are high in the winter and show depletion during the summer.
Silicate levels are high in the river water at all seasons. Nitrate
and phosphate levels are high in the entering ocean water during summer
offshore upwelling. The nutrient levels in the estuary generally
show a linear relationship with salinity, resulting from the levels of
nutrients in the entering river and ocean water. Superimposed upon
this linear relationship is a tendency for the nutrients to be enriched
in the bottom waters of the central part of the estuary.
The estuary phytoplankton are primarily composed of freshwater
forms, and probably represent a downstream extension of the
river flora. Regression analysis of phytoplankton levels vs. light,
nutrients, and river flow indicates that light probably limits phytoplankton
abundance on most dates.
The zooplankton of the estuary are composed of three groups,
preferring fresh, oligohaline, and polyhaline waters respectively.
Regression analysis indicates a strong correlation between abundance
of the freshwater group and river temperature. The factors controlling
the abundance of the oligohaline and polyhaline groups are less
obvious. The oligohaline group, principally Eurytemora affinis,
reaches the greatest population density (100,000/m³ or more).
Regression analysis indicates a close correlation between
Eurytemora abundance and phosphate levels. This indicates a strong
potential for zooplankton regeneration of phosphate necessary for
phytoplankton growth. / Graduation date: 1970
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Testing hypotheses with regard to measurement of primary productivity by 14C techniques: International Indian Ocean ExpeditionNewhouse, Jan January 1967 (has links)
Typescript. / Thesis (Ph. D.)--University of Hawaii. 1967. / Bibliography: leaves 211-218. / xi, 218 l illus., maps, tables
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