Natural populations of phytoplankton from Yaquina Bay, Oregon, were incubated in large polyethelene bags in- situ, with and without the natural assemblage of zooplankton. Samples were taken daily for two weeks in April, 1974. The biomass of phytoplankton in the bag without grazers reached values two to three times the biomass of phytoplankton in the bag with grazers. Sixty-eight to 93% of the cells in the bag without zooplankton were Thalassiosira fluviatilis, while the major species in the bag with zooplankton were T. fluviatilis, T. decipiens and Chaetoceros debilis, no one of which ever accounted for more than 40% of the cells. Nitrate-nitrite became depleted two days earlier in the bag without grazers and urea and ammonia values were higher in the bag with the grazers. Primary productivity, per unit cell volume, was higher in the grazed bag following nutrient depletion, suggesting some productivity enhancement by grazers. Physiological parameters indicate that the cells in the bag with zooplankton were richer in carbon, nitrogen and chlorophyll a, a higher percentage of the chlorophyll was degraded to phaeophytin and carbon to nitrogen ratios were lower. Data obtained from the bag with zooplankton were similar in range to data from the bay. The results support the contention that zooplankton can have a large effect on phytoplankton in terms of biomass, species composition, productivity and physiological state. / Graduation date: 1975

Graduation date: 1967

Thesis (M.A.)--Pan American University, 1983. / Includes bibliographical references (p. 127-137). Also available via Internet as PDF file through Southern Oregon Digital Archives: http://soda.sou.edu. Search History Collection.

A study was conducted at Yaquina Bay, Oregon, to determine the age-fecundity relationships in the striped seaperch Embiotoca lateralis. A questionnaire was sent to California, Oregon, and Washington to ascertain what regulations were in effect, and the value of the family Embiotocidae with regard to the sport and commercial harvest. The questionnaire revealed that no state maintained a systematic account of each species landed, and further life history data appeared desirable for sport and commercial species. Fish were collected from March 20 to August 21, 1960, with 140 females and 26 males being collected for analysis by hook and line or 125-foot experimental gill net. Scales were imprinted on cellulose acetate cards or mounted between glass slides, The catch was measured in centimeters of standard length and weighed in grams. From 123 females, 2, 654 embryos were obtained, and a maximum of 22 embryos per female was measured in millimeters of standard length. The estimated time of annulus formation in most scales was from March 15 to June 12. Second and third annuli were primarily laid down in March and April, with the probable peak of annulus formation for females of ages IV, V and VI in May. Length-frequencies were presented by age-class and sex. Eighty-one females of age-class III dominated the sample. Females of age-classes II and III attained greater average lengths than males. In age-class II, average weights for females were slightly greater than those for males. Both sexes generally mature for the first time in their third year of life. Length-weight, and length-number of embryos per female, for females of age-classes III-IV, were expressed by the regression equation Y[subscript c] = a+ b (X). High correlations for length-weight were ob- tained. Additional females were needed to evaluate that age when weights would digress. Females of age-class V produced the most embryos per unit increase in length; this rate declined in age-class VI. The largest number of embryos produced by an age class was 1, 431, in age-class III. The average number (in parentheses) of embryos produced per female of each age class, was: II ( 17); III (18); IV (21); V (30); VI (31) and VII (32). The most prolific female was seven years old and contained 45 embryos. Sixteen diminutive embryos were collected in 10 out of 128 mature females. Most older females were thought to have ovulated earlier than younger females, for their embryos were generally larger than embryos of younger females. However, embryos from younger females could reach the approximate mean size of embryos of older females, but at a later date. Birth of embryos began about June 12 and ended in late July. Embryos averaged about 50 mm in standard length at birth. Suggestions are given for management of the striped seaperch. / Graduation date: 1966

Due to accelerated climatic warming during the past fifty years, interest and concerns have been growing about changes in the ecological integrity of shallow freshwater ponds that dominate the landscape of the Hudson Bay Lowlands (HBL). Climatic warming is altering the hydrological processes that influence the water balances in these ponds, but knowledge remains insufficient to determine the effects these changes have on ecological conditions in the ponds. To address this knowledge gap, this study examines the relations between current hydrological and limnological conditions and recently deposited sedimentary assemblages of diatoms and photosynthetic pigments in 23 shallow ponds in the HBL. The knowledge from the contemporary studies will be used to inform paleolimnological reconstructions using multiple proxies at two ponds to assess how hydroecological conditions have changed during the past several centuries in response to climatic variations. Water samples were collected three times in 2010 to explore the relations between current hydrological and limnological conditions. The climatic conditions in 2010 provided an excellent opportunity to assess the effects that continued climate warming may exert on hydrolimnological conditions in the study ponds as the warm, dry conditions during the early thaw-season (May- mid-July) followed by extremely wet conditions for the remainder of the thaw-season are likely representative of future climate scenarios. The analysis revealed that the water chemistry in the ponds evolved along one of four different ‘trajectories’ throughout the thaw-season in 2010. These seasonal patterns of limnological conditions closely aligned with similar patterns identified in a study of contemporary hydrological conditions (Light, 2011; Wolfe et al., 2011). The patterns identified in both the hydrological and limnological studies were attributed to differences among ponds in catchment characteristics and hydrological connectivity with adjacent basins. Surface sediment samples were collected in 2010 to determine if hydrolimnological conditions are reflected in the distribution of recently deposited diatom and pigment communities. It was determined that diatom community composition was most highly influenced by the availability of microhabitat in the ponds which did not appear to be controlled by hydrological conditions. Nitrogen availability was determined to be indirectly influencing diatom community composition as the nitrogen-limited conditions in the ponds favoured the proliferation of N2-fixing cyanobacterial mats that provided a large amount of epiphytic habitat in the majority of the study ponds. This resulted in the complete domination of diatom assemblages by one diatom specie that was closely associated with these algal mats in the surface sediments of most ponds. Aphanizophyll, a photosynthetic pigment representative of nitrogen-fixing cyanobacteria, was also in the highest concentration in most of the study ponds as a result of the nitrogen-limiting conditions that allowed these organisms to dominate. Ponds located in the tundra ecozone were also found to have the highest overall pigment concentration which was related to a longer growing season due to the small size of these ponds that resulted in earlier ice-off conditions. The longer growing season of ponds in the tundra ecozone may also be due to high winds that cause a decrease in snow cover, lower surface albedos and an earlier onset of the spring thaw. The paleolimnological reconstruction of two of the ponds revealed similar shifts in diatom community composition in the stratigraphic record even though patterns of past change in their basin hydrology, as explored though the analysis of the δ18OPW record archived in the aquatic cellulose contained in the pond sediments, was very different. The water balance of “Left Lake” was found to be highly influenced by increased evaporation associated with recent warming trends as it is a relatively small basin that becomes hydrologically isolated after the melt period. However, “Erin Lake” was not as susceptible to evaporation during the recent warming trend due to its larger catchment and hydrological connections to other ponds. Both of these ponds experienced marked changes in the diatom assemblages. The changes were characterized by a shift from assemblages containing both small, adnate, benthic taxa that prefer mineral grain substrates and epiphytic taxa that are associated with the cyanobacterial mats covering the pond bottoms to assemblages entirely dominated by epiphytic taxa. The shift in diatom community composition occurred ~1820 in Left Lake, but the timing cannot be determined with any degree of confidence in Erin Lake as no diatoms are observed in the sediment record during the period when the change occurred (~1550 to 1850) due to preservation issues. Analysis of fossil pigments indicates that nitrogen-fixing cyanobacteria have been important to the ecology of the ponds over the entire sediment record. However, there is a trend towards lower concentrations of pigments representative of N2-fixing cyanobacteria in the most recent sediments. The trend in cyanobacterial pigment concentrations coincides with inferred changes in nitrogen availability from the geochemical analysis of the pond sediments by Light (2011). This recent shift in nutrient status may be the result of a number of factors including the increased atmospheric deposition of anthropogenically-derived nitrogen or changes in biogeochemical cycling in the ponds.

Acoustic current meter data collected in the shallow ( 3m depth) Trinity Bay, (TB a sub-bay in Galveston Bay), TX, estuary were used to characterize locally generated windwaves. Significant wave heights, periods, and directions were estimated from dynamic pressure time-series (P; near bottom) and horizontal current velocities (U, V). Surface wave spectra were calculated from the pressure time-series and fitted to the empirical shallowwater Texel, Marsen, and Arsloe wave spectrum. The mean shape parameters used to define the TB wave spectra were:alpha = 0:016, gamma = 4:26, sigma-a = 0:063, sigma-b = 0:089. Waves heights were also hindcast using empirical and numerical models. The empirical formulas were derived from fetch-limited shallow water observations and follow the current proposed asymptotic limit to wave growth in shallow depth. The depth range for this empirical formulation is extended from 0.5–2m out to 3.5m. The model does not work for wind speeds less than 1m/s and during rapid wind direction changes. The Shallow WAves Nearshore numerical model was implemented in a Galveston Bay (GB; encompassing TB) computational domain. The model was forced with wind speeds and directions measured on-site and in four surrounding locations maintained by the NOAA PORTS. Currents measured on-site in TB and calculated bottom frictions were input homogeneously in space. The model was run in steady and unsteady conditions, and the modeled wave spectra were compared to the observations. The modeled wave spectra do not recreate the observed spectral shape for the steady and unsteady conditions. However, the total wave energy is represented in the unsteady conditions. In both the steady and unsteady cases, the wave period is underpredicted by one-half times the observed spectra and the model direction agrees with the observed wave directions.

Abstract The Tapong Bay and the Chiku Lagoon are major lagoons in the south of Taiwan and are ideal sites to study the influence of coastal environment change on the ecosystem. Therefore, this study aims to evaluate the influence of oyster culture racks removal on biochemical processes of carbon, nutrients and mercury in the Tapong Bay, as well as to compare the status of mercury and trace-metal pollution in Tapong Bay and Chiku Lagoon. Before the removal of the oyster culture racks from the Tapong Bay, the annual mean of water exchange time is about 10 days that is longer than that of the present condition (7.1 days). This suggests that the flushing condition of lagoon water is improved after the racks were removed. The annual mean of each nutrient concentration is also lower at present than before, probably due to the enhanced water exchange rate and biological utilization. The annual mean of ∆POC/∆PN is 8.1 that is larger than that of the previous condition (7.3), possibly resulting from the increase of inputs of organic detritus. The Tapong Bay is an autotrophic system (p-r>0) both before and after the removal of oyster culture racks. However, the net ecosystem production (p-r) at present is twice as large as before the removal of oyster racks. After the removal of racks, the annual nitrogen fixation still exceeds the annual denitrification in the Tapong Bay with a magnitude of 5.35 mole N m-2 yr-1. Mercury (Hg) is a highly toxic metal with high affinity to biota. As the lack of Hg distribution data around the coastal zone of Taiwan, the study also aims to develop the analytical methods of Hg species and apply to study Hg biogeochemistry in Tapong Bay and Chiku Lagoon. Distributions of Hg species in the Tapong Bay are spatio-temporally variable, ranging from 6.66 to 12.40 ng/l (ave., 10.01 ng/l) for total Hg (unfilt.), from 1.79 to 3.75 ng/l (ave., 2.56 ng/l) for total dissolved Hg (filt.), from 1.59 to 2.67 ng/l (ave., 1.90 ng/l) for reactive Hg and from 2.51 to 9.45 ng/l (ave., 5.60 ng/l) for particulate Hg. Distributions of Hg species in the Chiku Lagoon are also spatio-temporally variable, ranging from 4.47 to 9.20 ng/l (ave., 6.22 ng/l) for total Hg (unfilt.), from 2.03 to 5.69 ng/l (ave., 4.54 ng/l) for total dissolved Hg (filt.), from 1.70 to 2.87 ng/l (ave., 2.12 ng/l) for reactive Hg and from 2.50 to 7.65 ng/l (ave., 4.79 ng/l) for particulate Hg. The abundance of particulate Hg is positively correlated with chlorophyll a, and total dissolved Hg and reactive Hg are negatively correlated with chlorophyll a. Such relationships imply that distributions of Hg species are primarily controlled by biological uptake and/or adsorption/desorption. Reactive Hg (Hg2+) is also correlated positively with dissolved oxygen concentration suggesting the biological redox effect in modulating the distribution of Hg2+. Particulate Hg also shows positive relationships with total suspended matter and particulate organic carbon, primarily due to biological absorption and particle adsorption/desorption. Enrichment factor (EF) are employed to evaluate trace metal pollution in Tapong Bay and Chiku Lagoon. The results show that the magnitudes of EF are larger in Tapong Bay than in Chiku Lagoon for most metals, particularly for Hg, indicating an thropogenic influence on metal distributions in both lagoons. On the other hand, particulate Hg is poorly correlated with particulate Fe, Mn and Al, strongly indicating relatively little influence of terrestrial detritus in modulating the distributions of particulate Hg.

ii Abstract Tapeng Bay has distinct dry (October to May) and wet (June to September) seasons. The salinity was 33‰ in the dry season, but may as low as 21‰ during the wet season. The yearly average temperature, salinity and chlorophyll a of Tapeng Bay are 26.9 ¢J, 29.7 ‰ and 2.24 £gg/L respectively. Thirty-six species of copepods belonging 18 families and three orders plus 16 unidenitified species were found in the materials of this study. The average abundance of copepods was 5.8 ¡Ó8.4 x10 5 ind./100m 3 . The nine most dominant species were Acartia tsuensis , Paracalanidae (copepodites), Acartiidae (copepodites), Parvocalanus crassi rostris , Oithonidae (copepodites), Oithona dissimilis , n auplius, Acrocalanus indicus and Zausodes spp., contibuting to 81% of the total copepods. Majority of the dominant species exhibited clear seasonal changes in abundance, varying positively with temperature. Acartia tsuensis and Acartiidae were dominant species in station N in the wet season, but other dominant species had higher abundance in the dry season. Aurelia aurita (Cnidaria, Scyphozoa) which was dominant in the dry season, may play the role of a keystone species at stations S and C. Species composition was different among stations. Fish-pond species was dominant at station S, copepodite and nauplii, and neritic species at station N. The abundance of copepods may be influenced by tidal action. When inlet species abundance is higher than neritic species, total copepod abundance at high tide is lower than at low tide, but the trend is reverse for neritic species. The grazing impact of copepods on phytoplankton was 0.04 to 40.36 % per day.

No description available.

No description available.