In 1960 a program was carried out to study some aspects of the distribution of planktonic ostracods in Indian Arm, an inlet of the coast of British Columbia. As a result, Paradoxostoma striungulum Smith, Phllomedes sp., Conchoecia elegans Sars, and C. pseudohamata n.sp. were collected, described and illustrated. Of these species, C. elegans and C, pseudohamata were abundant in the plankton, and provided material for the diagnoses of growth stages and for the comparison of the adult stages with those collected from other British Columbia inlets and from the Ocean Weather Station ”P” (50° N., 145° W.) The distributions of Conehoecia elegans and C. pseudohamata were studied in relation to temperature, salinity, oxygen, and light. The species were seldom found in water above the thermocline and halocline. The general distributions of Conehoecia elegans and C. pseudohamata may have been partly influenced by the mixing between water long resident in Indian Arm and water entering by way of the mouth of the Inlet. . Both species generally inhabited waters having temperatures from 7 to 9° C, and salinities from 26 to 27°/₀₀. Both occurred at depths greater than the shallow sill at the mouth; the one living more deeply seems to have been more restricted to the inlet than the other. Diurnal vertical migration differed for the two species except within the shallower part of the water column, where both seem to have descended in the presence of light. The time of maximal breeding seems to have been in the early summer for Conchoecia elegans and from early summer to early autumn for C. pseudohamata. Examination of stomach contents shows that both species were omnivorous. / Science, Faculty of / Zoology, Department of / Graduate

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

The role of heterotrophic bacteria in the carbon and nitrogen flux of the pelagic food web was investigated during laboratory and field-based studies of the temporal development of the planktonic community after upwelling. Bacterial community structure, activity and production were closely coupled to the upwelling cycle and to the dynamics of the phytoplankton community. The initial bacterial population (<l x 10⁶ cells ml⁻¹, 20 to 40 μg C l⁻¹) was metabolically dormant. Increased availability of phytosynthetically produced dissolved organic carbon (PDOC) stimulated bacterial growth (0.016 h⁻¹) and abundance (8 to 10 x 10⁶ cells ml⁻¹, 140 to 200 μg C l⁻¹). Rapid successions in the dominant plateable strains were attributed to substrate preferences and substrate availability. Significant correlations of bacterial biomass with total standing stocks of phytoplankton and particulate carbon provided evidence of close coupling between bacteria and PDOC, and between bacteria and recalcitrant substrates available during phytoplankton decay. These relationships were best described by power functions, suggesting that bacterial biomass was relatively reduced at high levels by predation. A microcosm study indicated that zooflagellate predation could control bacterial biomass. Low net growth yields (34 to 36%) of flagellates suggested inefficient transfer of carbon to higher trophic levels, but considerable nitrogen regeneration (ca 6 to 7 μg N mg dry weight⁻¹ h⁻¹). Thymidine-measured bacterial production (TTI, <0.1 to 1.25 mg C m⁻³ h⁻¹) was linearly related to phytoplankton growth. Non-uniform response of bacteria to added tracer substrates may result in underestimates of bacterial production by 2 to 34 times by TTI, particularly in deep or oligotrophic waters, or during phytoplankton decay. Close coupling of copepod (Calanoides carinatus) production to the upwelling cycle suggested co-existence of the microbial food web and the classical diatom-copepod food chain. Recently upwelled water was dominated by phytoplankton. Assuming that all phytoplankton carbon was available for utilisation, copepods and bacteria were calculated to consume approximately 12 and 22% of primary production respectively. As the bloom declined the planktonic community was increasingly dominated by bacteria, detritus and mesozooplankton. On average, copepods consumed 60% of primary production, while bacteria consumed 49%. Carbon consumption requirements of both bacteria and copepods were satisfied by resource partitioning and carbon cycling. Under food-limiting conditions herbivorous copepods may switch to omnivory, ingesting microzooplankton of the microbial food web, and stimulating enhanced remineralisation to further sustain primary production. A generic size-based simulation model of the dynamics of the plankton community indicated that bacteria and the microbial food web increase the overall productivity of the planktonic food web, and that heterotroph predation in the smaller size classes (<200 μm) is an important mechanism in nutrient recycling.

No description available.

No description available.

Limnological study of Moss Reservoir from May, 1975 through August, 1976 was conducted to evaluate the use of ATP assay in describing planktonic changes within the water column.

Plankton samples were taken periodically from one station in Salem Lake from the fall of 1955 through the winter of 1957. Other data including the pH, dissolved oxygen content, turbidity, brightness of day, temperature, and time of day were recorded at the time of each collection. The plankton samples were centrifuged and preserved in a 4% formalin solution. They were later examined microscopically, and density, percent density, and percent frequency calculations were made from them for ten selected species and for the five phyla which they represent.

The plankton community of the Gulf of California exist in a transition region from oceanic to neritic habitats, tropical to warm-temperature waters that is strongly influenced by a complex hydrography and bathymetry. Hyperiid Amphipods were chosen as a focus of this study to elucidate the various forces that shape the distributions of the entire community. To test how strongly hyperiids select water of a particular type (the "Water Mass" hypothesis), multiple regression analysis was applied to species' distributions and station hydrography. The quantitative results indicate that there is a strong relation between the distribution of a given hyperiid and the location of discrete water bodies in the Gulf of California. Three linked gyral currents, powered by a tidally-driven interval wave have been hypothesized to influence phytoplankton distributions in the Gulf. Through both qualitative and quantitative statistical analysis, these gyres are shown to be quite important in structuring species' distributions and have a strong effect on the character of the Gulf hydrography. Significant change in community diversity are found to occur only at the boundaries of these gyres. Many authors consider hyperiid amphipods as obligate parasites upon gelatinous zooplankton, and not worthy of distributional analyses. Both qualitative and quantitative test of this hypothesized relationship between hyperiid and "host" offer little support for the concept of hyperiid amphipods as parasites. Instead, there is considerable evidence that hyperiids are "substrate-bound," as are most amphipods, and use gelatinous zooplankton as facultative, transient hosts. Being able to switch hosts as desired, hyperiids can select for optimum conditions, and can serve to model the zooplankton community as a whole.

Chan Lai-chun. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1991. / Bibliography : leaves 139-154. / List of Tables --- p.V / List of Figures --- p.VI / Acknowledgements --- p.XIV / Abstract --- p.1 / Chapter Chapter 1 --- General introduction --- p.4 / Chapter Chapter 2 --- Literature review / Chapter 2.1. --- The Tolo Harbour Water Control Zone --- p.8 / Chapter 2.2. --- Hydrography of Tolo Harbour --- p.11 / Chapter 2.2.1. --- Temperature --- p.12 / Chapter 2.2.2. --- Salinity --- p.13 / Chapter 2.2.3. --- Secchi depth --- p.14 / Chapter 2.2.4. --- Dissolved oxygen --- p.15 / Chapter 2.3. --- Eutrophication in Tolo Harbour --- p.16 / Chapter 2.3.1. --- Nutrients --- p.17 / Chapter 2.3.2. --- Chlorophylls --- p.20 / Chapter 2.3.3. --- Red Tides --- p.21 / Chapter 2.4. --- Marine plankton in Tolo Harbour --- p.24 / Chapter 2.4.1. --- Phytoplankton --- p.24 / Chapter 2.4.2. --- Zooplankton --- p.25 / Chapter Chapter 3 --- The hydrography and marine plankton of Tolo Harbour / Chapter 3.1. --- Introduction --- p.27 / Chapter 3.2. --- Materials and Methods --- p.30 / Chapter 3.3. --- Results --- p.33 / Chapter 3.4. --- Discussion --- p.50 / Chapter Chapter 4 --- Seasonal dynamics of crustacean zooplankton in Tolo Harbour / Chapter 4.1. --- Introduction --- p.57 / Chapter 4.2. --- Materials and Methods --- p.58 / Chapter 4.3. --- Results --- p.59 / Chapter 4.4. --- Discussion --- p.71 / Chapter 5 Biology of the marine cladoceran Penilia avirostris Dana in Tolo Harbour / Chapter 5.1. --- Introduction --- p.77 / Chapter 5.2. --- Materials and Methods --- p.79 / Chapter 5.3. --- Results --- p.81 / Chapter 5.4. --- Discussion --- p.92 / Chapter Chapter 6 --- Grazing behaviour of the marine cladoceran Penilia avirostris Dana in Tolo Harbour / Chapter 6.1. --- Introduction --- p.97 / Chapter 6.2. --- Materials and Methods --- p.99 / Chapter 6.2.1. --- Isolation of algae from Tolo Harbour --- p.99 / Chapter 6.2.2. --- Algal culture --- p.99 / Chapter 6.2.3. --- Measurement of gut content --- p.100 / Chapter 6.2.4. --- Measurement of gut evacuation rate --- p.101 / Chapter 6.2.5. --- Measurement of ingestion rate and clearance rate --- p.102 / Chapter 6.2.6. --- Feeding impact --- p.103 / Chapter 6.2.7. --- Laboratory feeding experiments --- p.103 / Chapter 6.2.8. --- In situ experiment --- p.104 / Chapter 6.3. --- Results --- p.107 / Chapter 6.3.1. --- Indoor experiment --- p.107 / Chapter 6.3.2. --- In situ study --- p.120 / Chapter 6.4. --- Discussion --- p.129 / Chapter Chapter 7 --- General conclusion --- p.135 / References --- p.139

MOCNESS plankton tows, sediment traps and sedimentary material are used to determine the linkage between bio-physical forcing and foraminiferal response over a range of time scales from the event scale to the glacial interglacial cycle. The annually averaged planktic foraminiferal fauna of the modem California Current is a diverse community composed of individuals from subarctic, transitional, and subtropical foraminiferal assemblages. This community is more diverse, but less abundant in total standing stock and shell flux than the subarctic community of the Gulf of Alaska. The use of plankton tow and isotopic data allow us to partition the foraminiferal community into shallow dwelling euphotic zone species and deep dwelling sub-thermocline species. On both the event and seasonal time scales, heterotrophic species were most abundant in cold, biomass rich coastal waters. In contrast, species which harbored endosymbionts were more abundant in oligotrophic waters with higher ambient light levels. During the Last Glacial Maximum (LGM), the diverse modern fauna was replaced with a low diversity, high flux, heterotrophic community similar to that of the modern Gulf of Alaska. Modern analog temperature estimates suggest the California Current was roughly 3��C cooler during the LGM than today. Coupled with oxygen isotopic results from G. bulloides, the surface thermal structure implies an equatorward flowing glacial California Current at these sites. The Polar Front thus remained north of these locations during the LGM. Comparison of glacial G. bulloides carbon isotopes and shell accumulation rates with organic carbon flux estimates implies the glacial California Current was (1) higher in nutrient content, (2) lower in plankton biomass, and (3) lower in export carbon flux than its modem counterpart. This description suggests that during the LGM the plankton community of the California Current was very similar to the modern plankton community of the Gulf of Alaska. / Graduation date: 1996