Geology topics

Bradley D. Cramer

Publications and source records attributed to Bradley D. Cramer.

6 recordsLinked to original sources

USGS2016

Avian predation on juvenile Salmonids: Spatial and temporal analysis based on acoustic and passive integrated transponder tags

We evaluated the impact of predation on juvenile steelhead Oncorhynchus mykiss and yearling and subyearling Chinook Salmon O. tshawytscha by piscivorous waterbirds from 11 different breeding colonies in the Columbia River basin during 2012 and 2014. Fish were tagged with both acoustic tags and PIT tags and were tracked via a network of hydrophone arrays to estimate total smolt mortality (1 – survival) at various spatial and temporal scales during out‐migration. Recoveries of PIT tags on bird colonies, coupled with the last known detections of live fish passing hydrophone arrays, were used to estimate the impact of avian predation relative to total smolt mortality. Results indicated that avian predation was a substantial source of steelhead mortality, with predation probability (proportion of available fish consumed by birds) ranging from 0.06 to 0.28 for fish traveling through the lower Snake River and the lower and middle Columbia River. Predation probability estimates ranged from 0.03 to 0.09 for available tagged yearling Chinook Salmon and from 0.01 to 0.05 for subyearlings. Smolt predation by gulls Larus spp. was concentrated near hydroelectric dams, while predation by Caspian terns Hydroprogne caspia was concentrated within reservoirs. No concentrated areas of predation were identified for double‐crested cormorants Phalacrocorax auritus or American white pelicans Pelecanus erythrorhynchos . Comparisons of total smolt mortality relative to mortality from colonial waterbirds indicated that avian predation was one of the greatest sources of mortality for steelhead and yearling Chinook Salmon during out‐migration. In contrast, avian predation on subyearling Chinook Salmon was generally low and constituted a minor component of total mortality. Our results demonstrate that acoustic and PIT tag technologies can be combined to quantify where and when smolt mortality occurs and the fraction of mortality that is due to colonial waterbird predation relative to non‐avian mortality sources.

Transactions of the American Fisheries Society↗

USGS2015

Colonial waterbird predation on Lost River and shortnose suckers based on recoveries of passive integrated transponder tags

We evaluated predation on Lost River suckers ( Deltistes luxatus ) and shortnose suckers ( Chasmistes brevirostris ), both listed under the Endangered Species Act (ESA), from American white pelicans ( Pelecanus erythrorhynchos ) and double-crested cormorants ( Phalacrocorax auritus ) nesting at mixed species colonies on Clear Lake Reservoir, CA and Upper Klamath Lake, OR during 2009-2014. Predation was evaluated by recovering passive integrated transponder (PIT) tags that were implanted in suckers, subsequently consumed by pelicans or cormorants, and deposited on the birds’ nesting colonies. Data from PIT tag recoveries were used to estimate predation rates (proportion of available tagged suckers consumed) by birds to evaluate the relative susceptibility of suckers to avian predation in Upper Klamath Basin. Data on the size of pelican and cormorant colonies (number of breeding adults) at Clear Lake and Upper Klamath Lake were also collected and reported in the context of predation on suckers. Results indicate that predation rates varied by sucker species (Lost River, shortnose), sucker age-class (adult, juvenile), bird colony location (Upper Klamath Lake, Clear Lake), and year (2009-2014), demonstrating that predator-prey interactions in the system were dynamic during the study period. Tagged suckers ranging from 72 mm to 730 mm were susceptible to cormorant or pelican predation; all but the largest of the tagged Lost River suckers were susceptible to avian predation. Estimates of minimum, annual predation rates ranged from <0.1% to 4.6% of the available Lost River suckers and from <0.1% to 4.2% of the available shortnose suckers during the study period. Of the two colony locations evaluated, predation rates on suckers in Clear Lake were generally higher by birds nesting at mixed-species colonies on Clear Lake. Birds nesting on Clear Lake also commuted over 75 kilometers to forage on suckers in Upper Klamath Lake. Conversely, there was no evidence that birds nesting in Upper Klamath Lake foraged on tagged suckers in Clear Lake. Although sample sizes of tagged juvenile suckers were small and limited to fish tagged in Upper Klamath Lake, there was evidence that bird predation on juvenile suckers was higher than on adult suckers, with annual predate rate estimates on juvenile suckers ranging from 5.7% to 8.4% of available fish. The minimum annual predation rates presented here suggests that avian predation may be a factor limiting recovery of populations of Lost River and shortnose suckers, particularly juvenile suckers in Upper Klamath Lake and adult suckers in Clear Lake. Additional research is needed, however, to better assess the impacts of avian predation on sucker populations by (1) recovering PIT tags in a manner so that the species of avian predator is known (i.e., pelican vs. cormorant), (2) measuring predator-specific PIT tag deposition probabilities at each colony, (3) increasing the sample of juvenile suckers in the population that are PIT-tagged, and (4) recovering sufficient sample sizes of PIT tags on bird colonies to describe how various biotic and abiotic factors (e.g., fish size and condition, water levels and quality, and other factors) contribute to sucker susceptibility to avian predation in the Upper Klamath Basin.

California, Oregon↗

USGS2011

A revised 87Sr/86Sr curve for the Silurian: Implications for global ocean chemistry and the Silurian timescale

Recent recalibration of the Silurian timescale and improved global chronostratigraphic correlation of Silurian strata significantly altered the Silurian 87 Sr/ 86 Sr curve and the temporal extent of available data. Whereas previous Silurian 87 Sr/ 86 Sr composites showed a generally monotonic increase throughout the Silurian, revisions to the Silurian timescale now require a major increase in the rate of change in 87 Sr/ 86 Sr at or near the onset of the Gorstian Age of the Ludlow Epoch. Similarly, improved chronostratigraphic correlations between Silurian outcrops on Anticosti Island, Canada, and Gotland, Sweden, indicate that the middle part of the Telychian Age, which is roughly 10%–15% of the total duration of the Silurian period, is undersampled and underrepresented in Silurian 87 Sr/ 86 Sr composites. A revised Silurian 87 Sr/ 86 Sr curve based on 241 new and published analyses confirms the significant increase in the rate of change of 87 Sr/ 86 Sr toward more radiogenic values near the base of the Ludlow Series. On the basis of these data, we propose that the rapid trend toward more radiogenic 87 Sr/ 86 Sr values is indicative of increased weathering of old sialic crust exposed during the Silurian uplift of portions of Baltica, Laurentia, and Avalonia. Importantly, however, the actual rate of change of 87 Sr/ 86 Sr will remain equivocal until the durations of Silurian epochs and ages are better constrained.

Journal of Geology↗

USGS2010

Testing the limits of Paleozoic chronostratigraphic correlation via high-resolution (<500 k.y.) integrated conodont, graptolite, and carbon isotope (δ 13 C carb ) biochemostratigraphy across the Llandovery–Wenlock (Silurian) boundary: Is a unified Phanerozoic time scale achievable?

The resolution and fidelity of global chronostratigraphic correlation are direct functions of the time period under consideration. By virtue of deep-ocean cores and astrochronology, the Cenozoic and Mesozoic time scales carry error bars of a few thousand years (k.y.) to a few hundred k.y. In contrast, most of the Paleozoic time scale carries error bars of plus or minus a few million years (m.y.), and chronostratigraphic control better than ??1 m.y. is considered "high resolution." The general lack of Paleozoic abyssal sediments and paucity of orbitally tuned Paleozoic data series combined with the relative incompleteness of the Paleozoic stratigraphic record have proven historically to be such an obstacle to intercontinental chronostratigraphic correlation that resolving the Paleozoic time scale to the level achieved during the Mesozoic and Cenozoic was viewed as impractical, impossible, or both. Here, we utilize integrated graptolite, conodont, and carbonate carbon isotope (??13Ccarb) data from three paleocontinents (Baltica, Avalonia, and Laurentia) to demonstrate chronostratigraphic control for upper Llando very through middle Wenlock (Telychian-Sheinwoodian, ~436-426 Ma) strata with a resolution of a few hundred k.y. The interval surrounding the base of the Wenlock Series can now be correlated globally with precision approaching 100 k.y., but some intervals (e.g., uppermost Telychian and upper Shein-woodian) are either yet to be studied in sufficient detail or do not show sufficient biologic speciation and/or extinction or carbon isotopic features to delineate such small time slices. Although producing such resolution during the Paleozoic presents an array of challenges unique to the era, we have begun to demonstrate that erecting a Paleozoic time scale comparable to that of younger eras is achievable. ?? 2010 Geological Society of America.

Geological Society of America Bulletin↗

USGS2010

Paleobiogeography, high-resolution stratigraphy, and the future of Paleozoic biostratigraphy: Fine-scale diachroneity of the Wenlock (Silurian) conodont Kockelella walliseri

The Wenlock Epoch of the Silurian Period has become one of the chronostratigraphically best-constrained intervals of the Paleozoic. The integration of multiple chronostratigraphic tools, such as conodont and graptolite biostratigraphy, sequence stratigraphy, and ??13Ccarb chemostratigraphy, has greatly improved global chronostratigraphic correlation and portions of the Wenlock can now be correlated with precision better than ??100kyr. Additionally, such detailed and integrated chronostratigraphy provides an opportunity to evaluate the fidelity of individual chronostratigraphic tools. Here, we use conodont biostratigraphy, sequence stratigraphy and carbon isotope (??13Ccarb) chemostratigraphy to demonstrate that the conodont Kockelella walliseri, an important guide fossil for middle and upper Sheinwoodian strata (lower stage of the Wenlock Series), first appears at least one full stratigraphic sequence lower in Laurentia than in Baltica. Rather than serving as a demonstration of the unreliability of conodont biostratigraphy, this example serves to demonstrate the promise of high-resolution Paleozoic stratigraphy. The temporal difference between the two first occurrences was likely less than 1million years, and although it is conceptually understood that speciation and colonization must have been non-instantaneous events, Paleozoic paleobiogeographic variability on such short timescales (tens to hundreds of kyr) traditionally has been ignored or considered to be of little practical importance. The expansion of high-resolution Paleozoic stratigraphy in the future will require robust biostratigraphic zonations that embrace the integration of multiple chronostratigraphic tools as well as the paleobiogeographic variability in ranges that they will inevitably demonstrate. In addition, a better understanding of the paleobiogeographic migration histories of marine organisms will provide a unique tool for future Paleozoic paleoceanography and paleobiology research. ?? 2010 Elsevier B.V.

Palaeogeography, Palaeoclimatology, Palaeoecology↗

USGS2008

Record of the Late Devonian Hangenberg global positive carbon-isotope excursion in an epeiric sea setting: Carbonate production, organic-carbon burial and paleoceanography during the late Famennian

Latest Famennian marine carbonates from the mid-continent of North America were examined to investigate the Late Devonian (very late Famennian) Hangenberg positive carbon-isotope (??13 Ccarb) excursion. This global shift in the ?? 13C of marine waters began during the late Famennian Hangenberg Extinction Event that occurred during the Middle Siphonodella praesulcata conodont zone. The post-extinction recovery interval spans the Upper S. praesulcata Zone immediately below the Devonian-Carboniferous boundary. Positive excursions in ?? 13 Ccarb are often attributed to the widespread deposition of organic-rich black shales in epeiric sea settings. The Hangenberg ??13 Ccarb excursion documented in the Louisiana Limestone in this study shows the opposite trend, with peak ??13 Ccarb values corresponding to carbonate production in the U.S. mid-continent during the highstand phase of the very late Famennian post-glacial sea level rise. Our data indicate that the interval of widespread black shale deposition (Hangenberg Black Shale) predates the peak isotope values of the Hangenberg ??13 Ccarb excursion and that peak values of the Hangenberg excursion in Missouri are not coincident with and cannot be accounted for by high Corg burial in epeiric seas. We suggest instead that sequestration and burial of Corg in the deep oceans drove the peak interval of the ??13Ccarb excursion, as a result of a change in the site of deep water formation to low-latitude epeiric seas as the global climate shifted between cold and warm states.

Conference Paper↗