Holocene climate and El Nino history as recorded in the sediments of northern coastal Peru [abstract, table, and references]

EXTRACT (SEE PDF FOR FULL ABSTRACT): The history of the El Nino phenomena is recorded in both the fluvial and coastal sediments of northern Peru. The fluvial record was presented at the 1987 PACLIM Workshop and is discussed in detail elsewhere (Wells, 1987). However, the number of radiocarbon dated El Nino events has increased since Wells (1987) was published; this data is presented in Table 1.

Paleoenvironmental records from the Quelccaya ice cap, Peru and preliminary results from the Dunde ice cap, China [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): The 1000 year records of particulate deposition (soluble and insoluble), oxygen isotopic ratios, and net accumulation from the Quelccaya ice cap are presented. The net accumulation record from Quelccaya is shown to serve as a reasonable proxy for the water levels in Lake Titicaca. ... The ice core record from the Dunde ice cap offers the potential to reconstruct a very detailed history of environmental conditions on the Tibetan Plateau for the last 3000 years.

A review of water year 1987 in northern California [abstract and figures]

EXTRACT (SEE PDF FOR FULL ABSTRACT): It seems that an average water year is a rare beast; 1987 was no exception. It turned out to be the ninth driest this century in Northern California's Sacramento River basin. I'd like to summarize for you some interesting facts about water year 1987 and how it affected rainfall, snowpack, runoff, and water storage in California.

Trans-Sierran climatic contacts during the last 12,000 years [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): The early-Holocene warm period, ca. 9000 years ago, is a realistic analog for the possible effects of greenhouse warming. At that time the vegetation of the western Sierra Nevada resembled that currently found east of the crest. ... Tourism, water supply, and the logging industry will be negatively effected if climate changes during the next century are in the direction and magnitude of those of the early Holocene. Increased precipitation in the eastern Sierra could offset some of the effects.

Associations among chlorophyll concentration and climatic variables for Suisun Bay and the Sacramento-San Joaquin Delta [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): The recent changes in phytoplankton production and community composition within the Suisun Bay and Sacramento-San Joaquin Delta may be related to climate. Chlorophyll a concentration, decreased by 42% (spring-summer) and 29% (fall) between 1972 through 1976 and 1977 through 1981. The decrease in biomass was characterized by a shift in phytoplankton community dominance from Skeletonema spp., Cyclotella spp. and Coscinodiscus spp. to Melosira granulata. The possible influence of climate on phytoplankton abundance was suggested by multivariate statistical analyses that demonstrated an association between changes in phytoplankton community composition and abundance between 1975 and 1982 and the climate related variables wind velocity, precipitation, river flow and water temperature.

Record of the 1983 El Nino in Santa Barbara basin [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): The 1983 El Nino resulted in a decrease in the flux of diatoms and planktonic foraminiferans into the Santa Barbara basin. These may both be related to the decrease in productivity and therefore standing crops of these two groups.

A sensitivity analysis of Southwestern climate [abstract and conclusions]

EXTRACT (SEE PDF FOR FULL ABSTRACT): We provide here an estimate of the extent that modern climate in the southwest US is sensitive to changes in several parameters that reflect global climatic changes. For the purposes of this study, we define modern climate as mean monthly values for the months of February and August (called winter and summer, respectively) of temperature and precipitation, at points representing the average of cells of dimension 7.5' on a side. The area studied surrounds the drainage basin of Death Valley, California.

Regulation of primary production in the Gulf of California through interaction of large-scale and local ocean processes [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): The suppression of primary productivity observed in eastern boundary ecosystems of the Pacific during El Nino episodes does not occur throughout the Gulf of California. On the contrary, analysis of the modern siliceous phytoplankton record from annually layered sediments and compilation of available primary productivity measurements indicate that production is significantly increased in the central Gulf during El Nino years compared to anti-El Nino years. Integrated observations of biological and physical variability during the spring of 1983, under the influence of the strong El Nino, show that very high primary productivity occurred along the eastern margin of the central Gulf. This resulted from the upwelling of a nutrient rich source provided by the locally formed Gulf water mass originating in the northern Gulf. Lower productivity and phytoplankton biomass were associated with the anomalous penetration of Tropical Surface Water along the western side of the Gulf.

Climatic controls on diatom succession at Elk Lake, Minnesota [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): Sediment traps placed in the profundal region of Elk Lake, north central Minnesota during the 1979 spring and 1983-84 fall and spring seasons monitored seasonal diatom production for two climatically distinctive periods.

Stratigraphy and chronology of Holocene marine sedment core from the California continental borderland and their paleoceanographic/paleoclimatic significance [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): Paleomagnetic secular variation (PSV) records have been recovered from three marine sediment cores from Santa Catalina basin, California continental borderland, in order to more accurately date these late Quaternary sediments. ... The sedimentation rates derived from the time/depth curves suggest a constant rate of 20-25 cm/ky for the last 6700 years throughout Santa Catalina basin, and more variable rates (but constant within each core) of 13-86 cm/ky prior to 6700 ybp. The sedimentation rates prior to 6700 ybp are lowest in the southcentral portion of the basin and systematically increase toward the north end of the basin. These results suggest that 6700±300 ybp marks a major change in paleoceanographic processes within Santa Catalina basin.

Trends and long-term variability of ocean properties at Ocean Station P in the northeast Pacific Ocean [abstract]

Twenty-seven years (1956-1983) of oceanographic data collected at Ocean Station P (50°N/145°W), as well as supplementary data obtained in its neighborhood, have been examined for trends and interannual variability in the northeast Pacific Ocean. There is evidence that the water is warming and freshening and that the isopycnal surfaces are deepening. Trends in oxyty are mostly not significant. The most common periods for the interannual variability appear to be 2 1/2 and 6-7 years. The vertical movement of water accounts for one half of the changes in temperature and salinity and 30% of those in oxyty. Other factors, such as a shift of water masses, may also be important.

New insights into the diets of harbor seals (Phoca vitulina) in the Salish Sea revealed by analysis of fatty acid signatures

Harbor seals (Phoca fvitulina) are an abundant predator along the west coast of North America, and there is considerable interest in their diet composition, especially in regard to predation on valued fish stocks. Available informationon harbor seal diets, primarily derived from scat analysis, suggests that adult salmon (Oncorhynchus spp.), Pacific Herring (Clupea pallasii), and gadids predominate. Because diet assessments based on scat analysis may be biased, we investigated diet composition through quantitative analysis of fatty acid signatures. Blubber samples from 49 harbor seals captured in western North America from haul-outs within the area of the San Juan Islands and southern Strait of Georgia in the Salish Sea were analyzed for fatty acid composition, along with 269 fish and squid specimens representing 27 potential prey classes. Diet estimates varied spatially, demographically, and among individual harbor seals. Findings confirmed the prevalence of previously identified prey species in harbor seal diets, but other species also contributed significantly. In particular, Black (Sebastes melanops) and Yellowtail (S. flavidus) Rockfish were estimated to compose up to 50% of some individual seal diets. Specialization and high predation rates on Black and Yellowtail Rockfish by a subset of harbor seals may play a role in the population dynamics of these regional rockfish stocks that is greater than previously realized.

Historical knowledge of sharks: ancient science, earliest American encounters, and American science, fisheries, and utilization

In western civilization, the knowledge of the elasmobranch or selachian fishes (sharks and rays) begins with Aristotle (384–322 B.C.). Two of his extant works, the “Historia Animalium” and the “Generation of Animals,” both written about 330 B.C., demonstrate knowledge of elasmobranch fishes acquired by observation. Roman writers of works on natural history, such as Aelian and Pliny, who followed Aristotle, were compilers of available information. Their contribution was that they prevented the Greek knowledge from being lost, but they added few original observations. The fall of Rome, around 476 A.D., brought a period of economic regression and political chaos. These in turn brought intellectual thought to a standstill for nearly one thousand years, the period known as the Dark Ages. It would not be until the middle of the sixteenth century, well into the Renaissance, that knowledge of elasmobranchs would advance again. The works of Belon, Salviani, Rondelet, and Steno mark the beginnings of ichthyology, including the study of sharks and rays. The knowledge of sharks and rays increased slowly during and after the Renaissance, and the introduction of the Linnaean System of Nomenclature in 1735 marks the beginning of modern ichthyology. However, the first major work on sharks would not appear until the early nineteenth century. Knowledge acquired about sea animals usually follows their economic importance and exploitation, and this was also true with sharks. The first to learn about sharks in North America were the native fishermen who learned how, when, and where to catch them for food or for their oils. The early naturalists in America studied the land animals and plants; they had little interest in sharks. When faunistic works on fishes started to appear, naturalists just enumerated the species of sharks that they could discern. Throughout the U.S. colonial period, sharks were seldom utilized for food, although their liver oil or skins were often utilized. Throughout the nineteenth century, the Spiny Dogfish, Squalus acanthias, was the only shark species utilized in a large scale on both coasts. It was fished for its liver oil, which was used as a lubricant, and for lighting and tanning, and for its skin which was used as an abrasive. During the early part of the twentieth century, the Ocean Leather Company was started to process sea animals (primarily sharks) into leather, oil, fertilizer, fins, etc. The Ocean Leather Company enjoyed a monopoly on the shark leather industry for several decades. In 1937, the liver of the Soupfin Shark, Galeorhinus galeus, was found to be a rich source of vitamin A, and because the outbreak of World War II in 1938 interrupted the shipping of vitamin A from European sources, an intensive shark fishery soon developed along the U.S. West Coast. By 1939 the American shark leather fishery had transformed into the shark liver oil fishery of the early 1940’s, encompassing both coasts. By the late 1940’s, these fisheries were depleted because of overfishing and fishing in the nursery areas. Synthetic vitamin A appeared on the market in 1950, causing the fishery to be discontinued. During World War II, shark attacks on the survivors of sunken ships and downed aviators engendered the search for a shark repellent. This led to research aimed at understanding shark behavior and the sensory biology of sharks. From the late 1950’s to the 1980’s, funding from the Office of Naval Research was responsible for most of what was learned about the sensory biology of sharks.

Climatic impacts of the 1991-92 Western winter

EXTRACT (SEE PDF FOR FULL ABSTRACT): The latest in a series of unusual winters affected the western United States during 1991-92. This report is primarily concerned with the 6 to 8 coolest months, with some consideration of the adjacent summer months. ... Much of the winter was characterized by "split flow" west of North America. As it approached the West Coast, the jet stream frequently diverged into a northern branch toward Panhandle Alaska and a second southern branch that dived south along the California coast and then eastward along the US-Mexican border. Repeatedly, storms approaching the West Coast were stretched north-to-south, losing their organization in the process.

Demographic assessment of the blue crab (Callinectes sapidus) in Chesapeake Bay using extractable lipofuscins as age markers

The blue crab (Callinectes sapidus) plays an important economic and ecological role in estuaries and coastal habitats from the Gulf of Mexico to the east coast of North America, but demographic assessments are limited by length-based methods. We applied an alternative aging method using biochemical measures of metabolic byproducts (lipofuscins) sequestered in the neural tissue of eyestalks to examine population age structure. From Chesapeake Bay, subsamples of animals collected from the 1998–99 (n=769) and 1999–2000 (n=367) winter dredge surveys were collected and lipofuscin was measured. Modal analysis of the lipofuscin index provided separation into three modes, whereas carapace-width data collected among the same individuals showed two broad modes. Lipofuscin modal analysis indicated that most adults (carapace width >120 mm) were <2 years old. The results indicate that use of extractable lipofuscin can provide a more accurate and better resolved estimation of demographic structure of blue crab populations in the field than size alone.