<p> Wetlands exhibit high primary productivity and play a significant role in the global carbon cycle. Brackish and salt marshes co-occur in Southern California; yet, restoration designs often eliminate remnant brackish marshes, along with their ecosystem functions, without evaluation. Vegetation, soil organic matter, and carbon flux were compared between brackish and salt marsh habitats in the Huntington Beach Wetlands. Newland Brackish Marsh had more carbon aboveground in denser and taller vegetation than the other two marshes. Brookhurst Salt Marsh sediments had more organic matter than the other two marshes. CH₄ emissions were negligible at all sites, and there were no differences in CO₂ flux or aerobic and anaerobic microbial respiration among sites. Although these components of the carbon cycle were similar among sites in this project, such quantitative functional evaluations should be part of the restoration planning process.</p>

<p>Estuarine organisms, such as juvenile penaeid shrimp, experience fluctuating oxygen pressures on a daily basis. In coastal waters of the southeastern United States, severe hypoxia (&lt; 4&ndash;6 kPa) is common in the summer, also a time during which bacterial concentrations in seawater are high. In response to invading bacteria, crustaceans mount an immune defense resulting in aggregations of circulating hemocytes. These aggregates can be trapped in and obstruct hemolymph flow through the gills, inhibiting oxygen uptake. Hypoxia itself is also known to inhibit immune function. In this study we investigated some key characteristics of penaeid shrimp that are likely to be associated with their ability to cope with hypoxia and bacterial infection. We compare critical Po₂, the oxygen pressure below which oxygen uptake depends on available ambient oxygen, in two commercially important shrimp species: wild <i> Litopenaeus setiferus</i>, the Atlantic white shrimp, and aquacultured <i> Litopenaeus vannamei</i>, the Pacific whiteleg shrimp. We also compare whole body lactate concentrations following acute exposure to severe environmental hypoxia (5.3 kPa), and injection with a sub-lethal dose of bacteria (<i> Vibrio campbellii</i> 90-69B3), in aquacultured <i>L. vannamei</i> and in wild-caught <i>Farfantepenaeus duorarum</i>, the Atlantic pink shrimp. LD₅₀ tests indicate that the virulence of <i> V. campbellii</i> in <i>L. setiferus</i> (LD₅₀ = 6.4 &times; 10⁵ CFU g^&minus;1 shrimp) is similar to that previously determined in <i>L. vannamei</i> (LD₅₀ = 3.06 &times; 10⁵ CFU g^&minus;1 shrimp). We found no difference between <i>L. vannamei</i> and <i>L. setiferus </i> in critical Po₂, which fell between 3.5&ndash;5.2 kPa in both species. Whole body lactate concentration was measured in shrimp held in normoxia (>16 kPa) or hypoxia and injected with saline or bacteria. There were no effects of exposure in <i>L. vannamei</i>, however lactate concentration in <i>F. duorarum</i> increased by 60% in shrimp exposed concurrently to hypoxia and injected-bacteria, compared to saline-injected shrimp exposed to hypoxia and <i>Vibrio</i>-injected shrimp exposed to normoxia. This is consistent with previous findings in our lab, that hemocyanin in <i>L. vannamei</i> has a higher concentration and O₂ affinity, resulting in better tissue oxygenation, than that in wild species of Atlantic shrimp. These data suggest that aquacultured <i>L. vannamei </i> has an adaptive advantage over at least one species of wild penaeid shrimp in coping with hypoxia and bacterial infection. </p>

The aim of this study was to improve our understanding of the biology of two alien, invasive, free-floating species, the Water Fern Azollafiliculoides and the Least Duckweed Lemna minUla, which cause severe weed problems in Britain. Hence, control practices, which had been based upon anecdotal information, could be given a scientific foundation. An appraisal of the known distributions of the two species in Britain was undertaken. From an analysis of spread to date, it can be predicted that L. minUla will be present in 150 and A.filiculoides in 500, 10 x 10 km grid squares by the year 2000. Neither A. filiculoides nor L. minuta produce specialised overwintering structures and both rely heavily on ordinary, vegetative plants to overwinter. It was found that vegetative plants of both species can survive encasement in ice and laboratory studies show that they can withstand short exposure to sub-zero temperatures above approximately -4 °C. However, field evidence suggests that both species can survive much more severe temperature conditions, so both are considerably less cold-sensitive than previously suggested. L. minuta is not known to reproduce sexually in Britain. However, A. filiculoides sporulates regularly over a wide geographical range to produce numerous, viable sporocarps. These sporocarps form a 'seed' bank in the sediment and may ensure population survival because they are more freeze- and desiccation- tolerant than adult plants. Sporocarps require temperatures of not less than 10 °C and a short burst of light to germinate. L. min uta plants vary very little seasonally (although larger summer fronds can be easily confused with the common, native duckweed Lemna minor). In contrast, three forms of A. jilicuJoides can be identified; survival, mat and colonising. Competition experiments suggested the following tentative order of decreasing competitive ability; A. filiculoides > L. minuta > L. minor. This was probably a result of the more erect A filiculoides plants growing over the Lemna fronds. Not all field evidence supports this finding. Floating mats of A.filiculoides and L. minuta cause similar ecological problems because they reduce light, pH and oxygen and increase detrit~:s and probably alter nutrient loading. Laboratory studies showed that morphologically and physiologically plastic species of submerged plants, ego Elodea nuttall;;, could withstand these conditions better than less adaptable species, ego Potamogeton crispus. Four chemical control methods were tested over a range of dosages in the laboratory; diquat (as both spray and sub-surface injection), glyphosate (as spray) and terbutryn (as sub-surface application). These treatments were unsuccessful in controlling L. minuta, in contrast to anecdotal field evidence where terbutryn is considered effective. Glyphosate and diquat sprayed at 1.8 kg ai ha-1 and 1 kg ai ha-1 controlled A. jiliculoides. A. jiliculoides sporocarps were resistant to all chemical treatments.

published_or_final_version / Botany / Master / Master of Philosophy

Diets of two zooplanktivores were studied in Lake Winnipeg: the non-indigenous rainbow smelt (Osmerus mordax) and the native cisco (Coregonus artedi). Gut contents of smelt (70-130 mm total length) and cisco (100-200 mm TL) were concurrently collected with zooplankton (integrated vertical tows) from pre-determined locations throughout Lake Winnipeg in 2010 and 2011. When spatially separated, both zooplanktivores showed similar shifts from preference for fast-moving copepods during low total zooplankton density to slow-moving large cladocerans (Daphnia spp. and Eubosmina sp.) during high total zooplankton density. When spatially overlapped in the North Basin, dietary overlap was high between smelt and cisco, but possible vertical segregation was apparent during daylight-dark trawls. Diel variation in smelt diet was minimal. Overall, impact of smelt on the food web seemed weaker than in other smelt-invaded lakes, potentially owing to the warm, shallow nature of Lake Winnipeg providing a poorer quality habitat than cooler, deeper lakes.

This thesis examines the creation of an environmental monitoring system for inhospitable environments. It has been named The Remote Environmental Sensor Array System or RESA System for short. This thesis covers the development of RESA from its inception, to the design and modeling of the hardware and software required to make it functional. Finally, the actual manufacture, and laboratory testing of the finished RESA product is discussed and documented. The RESA System is designed as a cost-effective way to bring sensors and video systems to the underwater environment. It contains as water quality probe with sensors such as dissolved oxygen, pH, temperature, specific conductivity, oxidation-reduction potential and chlorophyll a. In addition, an omni-directional hydrophone is included to detect underwater acoustic signals. It has a colour, high-definition and a low-light, black and white camera system, which it turn are coupled to a laser scaling system. Both high-intensity discharge and halogen lighting system are included to illuminate the video images. The video and laser scaling systems are manoeuvred using pan and tilt units controlled from an underwater computer box. Finally, a sediment profile imager is included to enable profile images of sediment layers to be acquired. A control and manipulation system to control the instruments and move the data across networks is integrated into the underwater system while a power distribution node provides the correct voltages to power the instruments. Laboratory testing was completed to ensure that the different instruments associated with the RESA performed as designed. This included physical testing of the motorized instruments, calibration of the instruments, benchmark performance testing and system failure exercises. / Thesis (Ph.D, Civil Engineering) -- Queen's University, 2007-12-19 10:49:51.335

Diets of two zooplanktivores were studied in Lake Winnipeg: the non-indigenous rainbow smelt (Osmerus mordax) and the native cisco (Coregonus artedi). Gut contents of smelt (70-130 mm total length) and cisco (100-200 mm TL) were concurrently collected with zooplankton (integrated vertical tows) from pre-determined locations throughout Lake Winnipeg in 2010 and 2011. When spatially separated, both zooplanktivores showed similar shifts from preference for fast-moving copepods during low total zooplankton density to slow-moving large cladocerans (Daphnia spp. and Eubosmina sp.) during high total zooplankton density. When spatially overlapped in the North Basin, dietary overlap was high between smelt and cisco, but possible vertical segregation was apparent during daylight-dark trawls. Diel variation in smelt diet was minimal. Overall, impact of smelt on the food web seemed weaker than in other smelt-invaded lakes, potentially owing to the warm, shallow nature of Lake Winnipeg providing a poorer quality habitat than cooler, deeper lakes.

No description available.

No description available.

<p>White croaker (<i>Genyonemus lineatus</i>) are a sentinel fish species for contamination due to their direct interaction with contaminated sediments through benthic foraging. White croaker within the Los Angeles and Long Beach Harbor exhibited hierarchical habitat selection: avoiding dredged areas while selecting for areas of high sediment total organic carbon (4.8&ndash;8.1%), high polychaete density (406&ndash;700 polychaetes/0.1 m²), and small sediment grain size (&lt;23.5 &micro;m). Model results suggest that these fish are moving into shallower waters at night to forage and may refuge more during the day to avoid predation. The predictive model for white croaker habitat use indicated three important areas of use within the LA-LB Harbor: Consolidated Slip, Inner LB Harbor, and Fish Harbor. The areas containing the most preferable habitat to white croaker are also areas of high sediment contamination, and thus are the likely locations where these fish are acquiring contaminants. </p>