Science and Natural Resources
http://hdl.handle.net/2148/231
2024-03-29T15:30:53ZTreatments for hinge ligament disease in juvenile Pacific oysters (Crassostrea gigas)
http://hdl.handle.net/10211.3/207189
Treatments for hinge ligament disease in juvenile Pacific oysters (Crassostrea gigas)
Rich, Kimberly Suzanne
Cytophaga-like bacteria are the known etiological agent responsible for hinge ligament disease in juvenile Pacific oysters (Crassostrea gigas). An economically viable, natural way to manage this disease has not been documented. In vitro efficacy of hydrogen peroxide, CitroBio and ozone were determined for one strain (C1B-2) of Cytophaga-like bacteria. In vitro results showed that the CLB strain had the greatest sensitivity to CitroBio at 1000 ppm after 30 seconds. In vivo trials with hydrogen peroxide and extensive histological work failed to show a decrease in hinge ligament erosion. Approximately 71-74% of juvenile C. gigas were observed with ligament erosion at the conclusion of field trials. No serious pathological conditions resulting from a weakened hinge ligament were observed. No mortality nor negative effects on growth were noted as a result of treatment with hydrogen peroxide. In vitro results suggest further testing with CitroBio would be of benefit.
Thesis (M.S.)--Humboldt State University, Natural Resources: Fisheries Biology, 2006
2006-12-01T00:00:00ZVertebrate response to a tidal marsh restoration in Humboldt Bay, California
http://hdl.handle.net/10211.3/161038
Vertebrate response to a tidal marsh restoration in Humboldt Bay, California
Jacobson, Sandra L.
A 5.5-ha abandoned log pond (originally salt marsh) at the end of Park Street, Eureka, California was chosen as the off-site mitigation area for the destruction of 6.8 ha of wildlife habitat during the construction of the Woodley Island marina. Passive saltmarsh restoration was attempted by breaching a dike separating the log pond from Freshwater Slough (an estuary of Humboldt Bay) in December 1980, thus allowing the periodic tidal intrusion of salt water into 3.8 ha of the area. This study measured the response of amphibians, reptiles, birds, and mammals to the change in vegetation and other habitat conditions brought about by the reestablishment of tidal action. Previously, in August 1979 an interior dike had been constructed within a portion of the mitigation area to enhance an existing 0.7-ha freshwater marsh, and the effect of this change on the vertebrate life also was appraised.
Frogs disappeared and snakes declined in numbers within the tidal portion of the mitigation area after the dike was breached. Savannah Sparrows (Passerculus sandwichensis) were the most common birds in the grassland of the dried log pond before breaching, and declined after breaching. Several species of shorebirds and the Snowy Egret (Egretta thula) increased their use of the tidal portion of the mitigation area after breaching. Small mammals such as California Vole (Microtus californicus), Vagrant Shrew (Sorex vagrans), and Western Harvest Mouse (Reithrodontomys megalotis) were common before breaching, but declined in numbers in the first month after breaching. Use of the area by the most common large mammal, the Domestic Dog (Canis familiaris), increased after breaching because people used the flooded marsh to train retrievers.
Within the freshwater marsh five species of birds showed significant increases in numbers during subsequent corresponding seasons, whereas one species showed a significant decrease in numbers.
The success of the restoration after breaching was not fully known at the end of 1.5 years of study, but the trend was towards a renewed, vigorous salt marsh. In addition, the interior dike construction enhanced the freshwater marsh. In the interim the tidal and freshwater marshes provided valuable foraging areas for many species of wetland birds, and the freshwater marsh also served as a nesting area for certain bird species.
Thesis (M.S.)--Humboldt State University, Wildlife Management, 1986
1986-12-01T00:00:00ZThe effects of suspended and accreted sediment on the marine invertebrate fouling community of Humboldt Bay
http://hdl.handle.net/10211.3/157159
The effects of suspended and accreted sediment on the marine invertebrate fouling community of Humboldt Bay
Houle, Katie C.
Humboldt Bay, in far northern California receives a large amount of sediment, predominantly silts and clays from the surrounding watersheds at an estimated 62,532 metric tons/yr. (Barrett 2004). Fine grained sediments such as silts and clays have a high transport rate and remain in suspension longer than coarser sands and gravels, creating periods of high turbidity during winter rainfall events, which can last from a few hours to several weeks due to time lags following the event. While some of this sediment is washed out into the ocean, a large amount accumulates in the bay, which must be dredged annually by the U.S. Army Corps of Engineers to permit large commercial ships to move in and out of the bay. Winter rainfall events and human activity are the main drivers that elevate turbidity above normal background levels (>30 Nephelometric Turbidity Units; Shaughnessy and Williams 2005). We know very little about how the biological communities of Humboldt Bay respond to these extended disturbances of sediment suspension and deposition. Environmental Impact Assessments for dredging and development projects have provided some general information of potential impacts on select communities (U.S. Army Corps of Engineers San Francisco District, 2012), but direct effects of high (> 30 NTU) suspended and accreted sediment have not been rigorously tested. To address some of these gaps, the following study exposed naturally settled communities of sessile marine “fouling” invertebrates to 14-days of suspended or accreted sediment in a controlled laboratory setting, mimicking a high suspension event in Humboldt Bay. The experimental trials compared the effects of constant turbidity, generated by daily sediment addition at three treatment levels; Control (< 2 NTU), Low (20 NTU) and High (130 NTU). The role of surface orientation (vertical versus horizontal) was also explored during the 14-day turbidity trials to study the effect of sedimentation on communities by positioning panels either on the sides (vertical) or bottom (horizontal) of each tank. Average depths of sediment after 14-days of accretion for horizontal panels were ~3mm in the low and ~8mm in the high turbidity treatments. Overall, results showed the highest level of mortality was incurred in the high turbidity, horizontally oriented (~8mm final sediment accumulation) communities by organisms with low-profile (colonial ascidians; Botryllus spp., Botrylloides spp.) or encrusting growth forms (Celleporella hyalina). Organisms with upright growth forms (Bugula neritina, Bugula californica, Scrupocellaria diegensis, Ciona intestinalis, and Mytilus edulis) within these same communities were largely unaffected by sedimentation and high turbidity. Communities oriented vertically in both the low and high turbidity treatments experienced no statistically significant mortality across all species in comparison with the control treatment. These results suggest that position/orientation and morphology (encrusting versus upright) play important roles in individual survival and overall community response during high turbidity events in Humboldt Bay.
Thesis (M.S.)--Humboldt State University, Biology, 2015
2015-05-01T00:00:00ZModeling the effects of sea level rise on Long-billed Curlews at Humboldt Bay
http://hdl.handle.net/10211.3/144395
Modeling the effects of sea level rise on Long-billed Curlews at Humboldt Bay
Evangelista, Alan Glen B.
Sea level rise is predicted to have a negative effect on shorebird populations living in coastal environments. At Humboldt Bay, the availability of tidal flats that serve as habitat to many shorebirds throughout the year may become increasingly limited as higher sea levels permanently inundate lower elevation tidal flats. The Long-billed Curlew (Numenius americanus) is amongst the shorebird species at Humboldt Bay that may face reductions in population as feeding habitat becomes less available. I estimate how curlews will react to habitat change by developing a model that simulates the dynamics between the curlews, their prey, and their environment at Humboldt Bay. To understand how curlews are affected by habitat change due to sea level rise, I introduce predicted changes in habitat to the model. To predict how the habitat changes, I use the Sea Level Affecting Marshes Model, SLAMM, to estimate how different extents of sea level rise change intertidal habitat area. Based on the observed local sea level rise at Humboldt County, SLAMM predicts that mean sea level will increase 0.2-0.9 m over the next hundred years. This corresponds to a loss of 17-64% of current intertidal habitat area. Less dominant curlews are predicted to be strongly affected by the changes in the habitat and will have significant decreases in foraging time, overall weight, and overwinter success. In contrast, higher dominant curlews are more resistant to changes in the habitat and will be less affected by moderate changes in habitat. Given the maximum sea level rise scenario, overwinter success of higher dominant curlews may drop to 50% of the present value. In the same conditions, only 5% of low dominance curlews are expected to be successful. The model predicts that the maximum carrying capacity of Humboldt Bay will stay above 90% given moderate increases in sea level, while maximum
carrying capacity will drop below 40% given the maximum sea level rise scenario. The loss of intertidal habitat at Humboldt Bay will not only affect the Long-billed Curlew population, but will also limit other shorebird species. Modeling the effects of habitat change on Long-billed Curlew is a first step in understanding how shorebirds will respond to sea level rise. My methods can be extended to other shorebird species in the future to predict how overall abundance and diversity at Humboldt Bay will change in response to sea level rise.
Thesis (M.S.)--Humboldt State University, Environmental Systems: Mathematical Modeling, 2015
2015-05-01T00:00:00Z