University of Maine

About: University of Maine is a education organization based out in Orono, Maine, United States. It is known for research contribution in the topics: Population & Ice sheet. The organization has 8637 authors who have published 16932 publications receiving 590124 citations. The organization is also known as: University of Maine at Orono.

Chemical alarm signalling in aquatic predator-prey systems: A review and prospectus

Abstract: The importance of chemical cues in predator-prey interactions has recently received increasing attention from ecologists. The sources of chemicals to which prey species respond often originate as cues released by the predator (reviewed by Kats and Dill, this issue). Alternatively, cues may be released by other prey animals when they detect or are attacked by a predator. Such cues, known as chemical alarm signals, are particularly common in aquatic systems. These signals provide the basis of our current review. Short-term behavioural responses of prey animals to alarm signals have received the most attention. Behavioural responses of prey resemble those exhibited to known predators, and are therefore likely to make receivers less vulnerable to predation. More recently, studies have shown that benefits to alarm signal receivers extend beyond the immediate behavioural response of nearby conspecifics over a few minutes. For example, alarm signals are important in mediating the learning of unknown pred...

Fluorescence Inner-Filtering Correction for Determining the Humification Index of Dissolved Organic Matter

Abstract: The use of fluorescence spectrometry has been suggested as a simple method to determine the extent of natural organic matter humification by quantifying the red-shifting of fluorescence emission that occurs with increasing humification. Humification indices are calculated by dividing fluorescence intensity at longer wavelengths by intensity at shorter wavelengths. These indices calculated without any specific efforts to standardize dissolved organic matter (DOM) concentration will result in index values thatvary with DOM concentration due to fluorescence innerfiltering effects. This study critically evaluated the effect of DOM concentration on humification index determination using organic matter isolated from field corn extract, soil: water extract, and soil fulvic acid. The results show that humification index values are sensitive to DOM concentration of the solution and are linear with respect to transmittance of the solution at the 254 nm used as the excitation wavelength. An approximate correction for DOM is to exploit the linear nature of the regression fit and to determine index values at the extrapolated 100% transmittance value. An exact correction using explicit correction factors for both primary and secondary innerfiltration effects was shown to give humification index values that are concentration invariant when absorbance of the solution at 254 nm was less than approximately 0.3 unit. Defining the humification index as the fluorescence intensity in the 300-345 nm region divided by the sum of intensity in the 300-345 nm and 435-480 nm regions was statistically advantageous. This study suggests that for quantitative results which can be used to compare humification of natural organic matter across different studies, correction of the fluorescence emission spectra for innerfiltration effects is needed.

Oxygen isotope calibration of the onset of ice-rafting and history of glaciation in the North Atlantic region

Abstract: We report here that DSDP Site 552A, cored with the hydraulic piston corer on the west flank of Rockall Bank, recovered an undisturbed sequence of alternating white deep-sea carbonate oozes and dark-coloured layers that are rich in glacial debris. Oxygen isotope analysis of the sequence together with detailed nannofossil and palaeomagnetic stratigraphy shows that the first major horizon of ice-rafting occurred at about 2.4 Myr, and was preceded by a minor pulse of ice-rafting at about 2.5 Myr. The carbon isotope record shows that the site has been bathed by a water mass of similar characteristics to present-day North Atlantic deep water at least since 3.5 Myr.

Contemporary evolution meets conservation biology

Abstract: Recent research has revealed that evolution often occurs on contemporary timescales, often within decades. Contemporary evolution is associated with the same factors that are driving the current extinction crisis: habitat loss and degradation, overharvesting and exotic species. Thus, it is relevant to many conservation situations. First, habitat fragmentation might influence the potential of a population to adapt in response environmental degradation. Second, certain harvesting strategies can result in the evolution of life-history traits, ultimately resulting in negative impacts on harvestable yield. Third, the establishment of exotic species can be influenced by their adaptive potential and our ability to limit that potential. Furthermore, contemporary evolution is of concern for intensively managed species, because it might reduce their fitness in native habitats. Ultimately, contemporary evolution is influenced by complex interactions among population size, genetic variation, the strength of selection, and gene flow, making most management scenarios unique. In a world filled with contemporary evolution, conservation efforts that ignore its implications will be less efficient and perhaps even risk prone. Humans have become an evolutionary force of extraordinary influence [1], evidenced most obviously by an unprecedented extinction rate that is attributable to their activities [2]. Human activities are also associated with evolutionary changes that can occur within a few hundred years, otherwise known as CONTEMPORARY EVOLUTION (see Glossary) [3‐5].