Union Bay Research Articles

Investigation of duty cycles for measuring activity in passive acoustic bat monitoring

Echolocating bats are important bioindicators that can be monitored effectively using passive acoustic monitoring (PAM) techniques. In PAM, duty-cycle-based temporal subsampling is often used to collect data at ON/OFF intervals to circumvent the limitations of recorder battery and storage capacity to enable long-term monitoring. However, potential bias introduced by temporal subsampling has not been systematically investigated for bat monitoring. Here, we use continuous audio recordings from the Union Bay Natural Area in Seattle in Summer 2022 to simulate the effects of temporal subsampling using different duty cycle parameters. We detected bat calls automatically using a deep learning model [Aodha et al., 2022, BioRxiv] and calculated three metrics as proxy for bat activity: number of calls, Activity Index (AI), and Bout Time Percentage (BTP). We found that although the number of calls and AI are more readily computable using the detected calls, BTP is likely a more accurate measure that relies less on the performance of automated call detection methods. In addition, reduced sampling for only a portion of the night (e.g., 4 hrs) was generally inadequate for capturing bat activity. Our results suggest that considering species-specific acoustic characteristics is crucial for reducing sampling bias for PAM of bats.

Depositionally-Induced Magnetic Frequency Variations of a Sandstone Facies from the Copper Harbor Conglomerate of the North American, Mid-Continent Rift at Union Bay, Michigan

Precambrian sandstones were investigated to determine whether deep-time, fluvial red-beds can maintain magnetic variations related to deposition. Using an easily accessible site on Earth, it is possible to define methods that benefit future studies related to magnetic variations as linked to conditions of formation. The study utilized environmental magnetism and cyclostratigraphic techniques to determine magnetic characteristics and susceptibility variation frequencies. Magnetite and hematite were inferred from laboratory measurements and the magnetic fabric agreed with previous paleocurrent observations, suggestive that susceptibility correlates with deposition. Hematite concentration controlled susceptibility: high-susceptibility corresponded with large grain-sizes and cross-bedding, while low-susceptibility was attributed to small grain-sizes and erosional or color boundaries. A statistically-significant, cyclic, susceptibility signal was observed from the stratigraphy, suggesting that susceptibility variations may arise from climatically-induced variations in depositional or post-depositional processes. The observed frequency also supports the capacity for fluvial red-bed deposits to maintain depositional characteristics original to formational processes.

Predatory Copepods and Bosmina: Replacement Cycles and Further Influences of Predation Upon Prey Reproduction

In the days of large lakes, populations of cladocerans and rotifers often appear to undergo seasonal morphological changes. In the past, these transformations were thought to reflect phenotypic plasticity within lineages (cyclomorphosis). However, in Union Bay populations of Bosmina, the transformations clearly involve regular seasonal replacements (termed "taxocene cycles") by genetically different lineages. In Union Bay, Washington, USA, selective predation by both visually foraging and blindly grasping predatrory copepods, combined with reproductive and competitive costs associated with prey defense, created a spatial and temporal environment where the seasonally fluctuating selective regimes exceed the ability of individual lineages to adapt phenotypically to changes. Genetically different clones, some derived from biologically isolated populations, rapidly replace one another in time and space. While most clones remain extant throughout the year, even times of relatively small density differences are punctuated by rapid clonal replacement. Detailed study of the clonal replacements disclosed that: (1) phenotypes generally fall into three modal classes (short—, intermediate—, and long—featured forms); (2) the short and longs are separate species; and (3) intermediates are not the results of crosses between extremes, but are heterogeneous mixtures of convergent lines derived from the other two species. While there is limited sexual activity, and certainly opportunity for mating between clones, there is no electrophoretic evidence for crossing. The distinctive nature of certain secondary sexual features seems associated with mate choice and thus aids the isolation of various lineages. In general, the frequency of sexual activity, the evolution of the brood chamber, and the transparent ephippium all appear intimately associated with predation and the selective advantage of rapid reproductive responses.

Competition in Cladoceran Communities: The Cost of Evolving Defenses against Copepod Predation

An intimate relationship is apparent between fecudity and predator resistance in clones of the parthenogenic cladoceran Bosmina longirostris. Young of certain clones possess spines slightly larger bodies, the thicker carapaces, all of which frustrate the handling tactics of predatory copepods. During periods of abundant resources, the resistance is purchased at considerable cost, since eggs and developing young are carried n a restricted space, a special brood chamber formed from the dorsal portion of the carapace. The energy used in the development of protective defenses comes from the egg yolk supply, leading to larger eggs and small broods. During the spring algal bloom in Union Bay, Lake Washington, long—featured lines carry few large eggs, while short—featured lines fill their pouches with many small lines in the inshore regions after fisher remove predatory copepods.

The Divergence of Adjacent Populations

In Union Bay, a temperate embayment in Seattle, Washington, USA two different kinds of predators maintain a polymorphism of the cladoceran Bosmina longirostris. The boundary separating these two Bosmina populations is unusual because it is maintained in a freely mixing body of water, and important because its distinctness is a consequence of trophic dynamics, a result of the interactions of visual predators (fish) and grasping predators (copepods). Not only do the fish directly affect the morph composition by differentially removing the more conspicuous morphs, they also indirectly control the magnitude of counter—selection forces by regulating the abundance of predatory copepods. The joint action of both predators sets up a spatial situation in which adjacent populations of Bosmina actually diverge phenotypically and genetically during the summer.

Calculation of surface motions of a layered half-space

Abstract A new method is presented for computing the transient response of a set of horizontally stratified, linearly elastic layers overlying a uniform half-space and excited by vertically incident, transient plane waves. In addition, a simple approximate method of satisfactory accuracy is developed that reduces the computing time required. Calculated responses are compared with motions recorded under Union Bay in Seattle to evaluate the agreement between recorded and calculated motions.

Analyses of ground motions at Union Bay, Seattle during earthquakes and distant nuclear blasts

abstract Recordings of accelerations at three different depths within the soil profile at Union Bay were obtained during a mild nearby earthquake and three distant nuclear blast events. These recordings were made by instruments which had been placed in peat 10 feet below the ground surface, in clay 61 feet below the ground surface and in glacial till 105 feet below the ground surface. Accelerations in the EW, NS and vertical directions were recorded simultaneously at these three depths. Using an equivalent linear variable damping lumped-mass solution, incorporating strain-dependent material properties for the peat and clay layers, the motions throughout the deposits were computed. The recorded accelerations in the glacial till were used as input base motion. Comparisons of the time histories of accelerations, maximum accelerations and spectral values of the motions recorded during the nearby earthquake with the corresponding computed motions indicated a high degree of agreement. The maximum accelerations recorded during the distant nuclear blast events also compared well with the computed accelerations.

NOTES ON PETROCHEMISTRY OF ULTRAMAFIC INTRUSIVES

Some petrochemical features of ultramafic rocks are firstly discussed by taking account of mantle norms and M values. The existence of iron-rich ultramafic intrusives, e.g., the Union Bay complex, is pointed out and world-wide occurrences of these complexes are suggested. Commonly the rocks constituting ultramafic intrusives contain less aluminium than mantle peridotite, as represented by peridotite inclusions in basaltic rocks, and have a considerable wide range in their M values, whereas peridotite inclusions show relatively uniform M values. Secondly, the distribution relation of aluminium with four-fold co-ordination and silicon between co-existing clinopyroxenes and orthopyroxenes is discussed. Although tschermakitic molecule may be more soluble in clinopyroxenes than in orthopyroxenes at a given pressure, AlIV contents in orthopyroxenes are greater than those in clinopyroxenes from ordinary ultramafic intrusives. The reverse relation is observed in pyroxenes from peridotite inclusions and the Lizard primary peridotites which were formed at higher pressure. This is interpreted on the basis of physico-chemical considerations.

ORIGIN OF THE ULTRAMAFIC COMPLEX AT UNION BAY, SOUTHEASTERN ALASKA

An ultramafic complex at Union Bay, in southeastern Alaska, is an exceptionally well-exposed example of a series of similar complexes forming a belt parallel to the Coast batholith. A body of gabbro, approximately circular in plan and about 6 miles in diameter, intrudes folded sedimentary rocks of probably Triassic and Cretaceous age. A moderately low grade of regional metamorphism in the sedimentary rocks is increased to almandite-zone grade adjacent to the gabbroic contact. Intrusive into the gabbro is a remarkable ultramafic complex which comprises a vertical pipe approximately 1 mile in diameter, to which is attached a lopolithic offshoot approximately 5 miles long and 3 miles wide. The ultramafic units range through hornblende pyroxenite, pyroxenite, olivine pyroxenite, peridotite, and dunite, and both the pipe and the lopolith show a well-developed concentric zoning with dunite in the center and pyroxenite or hornblende pyroxenite on the periphery. Magnetite is a primary constituent of the pyroxenite unit. The most plausible explanation of the structure and petrology of the ultramafic complex is a hypothesis of successive injections of an ultramafic magma changing in composition with time and intruded in reverse of the order of crystallization of the component minerals. It has not been possible to explain the gabbro (which is olivine-free) by the same mechanism, yet the space and time relationships here, as elsewhere in the world, are probably not accidental. It is proposed, therefore, that a body of gabbro was emplaced, and into this was injected a plug and associated lopolith first of diopside-magnetite magma with minor olivine, then diopside-olivine magma, and finally olivine magma, each new magma intruding the central, incompletely solidified portion of the earlier magma. Minor mixing and melting explain the composition and distribution of the intermediate units of the complex. Lack of contact metamorphism of grade that might be expected to accompany intrusions of such high temperature is explained first by the fact that the ultramafic magmas were almost everywhere in contact with gabbro, not sedimentary rocks, and second by the fact that, being anhydrous, the ultramafic magmas absorbed, rather than expelled, volatiles. The only likely source for magmas of these compositions would be melting portions of the mantle, but no proposed mechanism for supplying the energy for this process is suggested herein. With an available source of energy, however, it can be postulated that magmas would be generated in the succession proposed. The gabbroic magma probably would originate as a result of melting at a shallower level.

Winter Roost of Starlings at Union Bay, Seattle

Winter Roost of Starlings at Union Bay, Seattle

SED Research Report No. 21: Sanitary Land Fill Tests Investigating Refuse Volume Reduction and Other Phenomena

Tests performed at Union Bay Sanitary Landfill Disposal site, Seattle, Wash, to ascertain compaction, settlement, fill temperature and gas production; critical review of these data with reference to obtaining optimum refuse disposal volume into given land fill area.

Union Bay. The Life of a City Marsh.Harry W. Higman , Earl J. Larrison

<i>Union Bay. The Life of a City Marsh.</i>Harry W. Higman , Earl J. Larrison

Union Bay. (The Life of a City Marsh)

Union Bay. (The Life of a City Marsh)

Union Bay (The Life of a City Marsh) by Harry W. Higman and Earl J. Larrison [Review

Union Bay (The Life of a City Marsh) by Harry W. Higman and Earl J. Larrison [Review

Union Bay: The Life of a City Marsh

Union Bay: The Life of a City Marsh

Union Bay State Proudly Presents...

Union Bay State Proudly Presents...

Magnetic anomalies in Alaska

Magnetic anomalies are the rule rather than the exception in Alaska, particularly in southeastern Alaska. Observations taken by Coast and Geodetic Survey parties indicate the presence of local disturbance all along the coast from Dixon Entrance at the southern extremity to the Bering Sea. St. George Island in the Bering Sea shows variations ranging from 6° east to 20° east, 17° east being normal.In western Alaska, on the Aleutian Peninsula, disturbances have been found, but are not fully developed. This will be done as the surveys of that area are completed. Chilkoot Inlet, southeastern Alaska, has variations ranging from 12° to 37° east, the normal being 32° east. Union Bay, southeastern Alaska, has variations ranging from 32° to 68° east, the normal being about 30°. At many places the disturbance extends out over the water‐areas in sufficient strength to affect the compasses of passing vessels. Wherever the surveys are sufficiently complete these disturbances are indicated on the navigation charts by local isogonic lines printed in red over the area affected.