193 research outputs found
Year-Round Algal Toxin Exposure in Free-Ranging Sea Lions: Implications of Trophic Exposure for Declining Populations
Harmful algal bloom (HAB) toxins have led to illness and mortality of many species of marine mammals and seabirds, including species with declining populations. On the US West Coast, the two most common HAB toxins affecting both humans and wildlife are domoic acid and saxitoxin. In an effort to document baseline concentrations and to investigate factors that affect exposure to HAB toxins, I measured concentrations of domoic acid and saxitoxin in scats from Steller sea lions Eumetopias jubatus (n = 383 scats) and California sea lions Zalophus californianus (n = 125 scats) in Washington State over a two-year period. Toxin concentrations in the scat were compared to the prey remains in the scat and to concentrations in nearshore bivalves. Saxitoxin was detected in 45 % and domoic acid was detected in 17 % of all scats tested, and both toxins were detected in all seasons and months of the year. Saxitoxin in scat was variable by season, year, and location, whereas domoic acid levels were consistently higher in the summer and at the southern-most haulout complex. Both toxins were detected in scat in winter when it was not detected in nearshore bivalves, confirming for the first time that marine mammals can be exposed to algal toxins through their prey outside periods of active algal blooms, most likely through benthic to pelagic food web transfer of precipitated cells and resting cysts. This study also found that prey with low occurrence in the sea lions’ diet, including walleye pollock Theragra chalcogramma, may act as vectors of significant algal toxin transfer up the food chain, a finding that could have profound implications for the endangered western distinct population segment of Steller sea lions because pollock are a dominant prey species in their diet. A variety of planktivorous, benthic, and pelagic fish were significantly associated with toxins in sea lion scat suggesting that multiple pathways through the marine food web lead to HAB toxin exposure in these top predators. In the face of increasing HABs worldwide, the finding that generalist predators, like sea lions, can be exposed to algal toxins year-round via multiple prey species may signal disproportionate impacts on declining populations already enduring multiple stressors
Aspects of the grammar of focus in English.
Massachusetts Institute of Technology. Dept. of Foreign Literatures and Linguistics. Thesis. 1970. Ph.D.Vita.Bibliography: leaves 331-334.Ph.D
Zipf's Law and Avoidance of Excessive Synonymy
Zipf's law states that if words of language are ranked in the order of
decreasing frequency in texts, the frequency of a word is inversely
proportional to its rank. It is very robust as an experimental observation, but
to date it escaped satisfactory theoretical explanation. We suggest that Zipf's
law may arise from the evolution of word semantics dominated by expansion of
meanings and competition of synonyms.Comment: 47 pages; fixed reference list missing in v.
Year-round Algal Toxin Exposure in Free-ranging Sea Lions
Harmful algal bloom toxins cause illness and mortality in marine mammals worldwide, yet the potential for year-round exposure to these toxins has not previously been studied. We measured concentrations of domoic acid and saxitoxin in scats from Steller sea lions Eumetopias jubatus (n = 383 scats) and California sea lions Zalophus californianus (n = 125 scats) over a 2 yr period. Toxin concentrations in the scats were compared to the prey remains in the scats and to concentrations in nearshore bivalves. Saxitoxin was detected in 45% and domoic acid was detected in 17% of all scats tested, and both toxins were detected in all seasons and months of the year. A variety of benthic and pelagic fish were significantly associated with toxins in sea lion scats, including prey with low occurrence in the sea lions’ diet. Toxins detected in winter scats confirm that US West Coast marine mammals are exposed to domoic acid and saxitoxin through their prey outside of the expected algal bloom season
Bringing features of human dialogue to web surveys
When web survey respondents self-administer a questionnaire, what they are doing is in many ways similar to what goes on in human–human interviews. The studies presented here demonstrate that enabling web survey respondents to engage in the equivalent of clarification dialogue can improve respondents' comprehension of questions and thus the accuracy of their answers, much as it can in human–human interviews. In two laboratory experiments, web survey respondents (1) answered more accurately when they could obtain clarification, that is, ground their understanding of survey questions, than when no clarification was available, and (2) answered particularly accurately with mixed-initiative clarification, where respondents could initiate clarification or the system could provide unsolicited clarification when respondents took too long to answer. Diagnosing the need for clarification based on respondent characteristics—in particular, age—proved more effective than relying on a generic model of all respondents' need for clarification. Although clarification dialogue increased response times, respondents preferred being able to request clarification than not. The current results suggest that bringing features of human dialogue to web surveys can exploit the advantages of both interviewer- and self-administration of questionnaires. Copyright © 2007 John Wiley & Sons, Ltd.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/55951/1/1335_ftp.pd
Apparent filler–gap mismatches in Welsh
AbstractFiller–gap dependencies involving a clause-initial filler constituent of some kind followed by a matching gap are an important feature of human languages. There are also certain cases where what looks like a filler differs in some way from the following gap. In the case of Welsh there is a mismatch between apparent filler and gap in some nominal cleft sentences. It can be argued, however, that the initial constituent is not a filler but one term of a hidden identity predication. There are various other complexities in this area. There is one word, the identity copula, which only allows a complement that is a gap. There are two cases where a deletion process conceals the identity of the initial constituent in a cleft sentence, making a Progressive Phrase look like a Verb Phrase and a Predicative Phrase look like an Adjective Phrase or a Noun Phrase. Finally, there are three cases where a verb with a gap as a dependent has a special form, two cases involving the predicational copula and one involving all transitive verbs. Thus, a number of mechanisms are required to deal with the full set of facts.</jats:p
Language as an instrument of thought
I show that there are good arguments and evidence to boot that support the language as an instrument of thought hypothesis. The underlying mechanisms of language, comprising of expressions structured hierarchically and recursively, provide a perspective (in the form of a conceptual structure) on the world, for it is only via language that certain perspectives are avail- able to us and to our thought processes. These mechanisms provide us with a uniquely human way of thinking and talking about the world that is different to the sort of thinking we share with other animals. If the primary function of language were communication then one would expect that the underlying mechanisms of language will be structured in a way that favours successful communication. I show that not only is this not the case, but that the underlying mechanisms of language are in fact structured in a way to maximise computational efficiency, even if it means causing communicative problems. Moreover, I discuss evidence from comparative, neuropatho- logical, developmental, and neuroscientific evidence that supports the claim that language is an instrument of thought
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Status of the European Green Crab, Carcinus maenas, in Oregon and Washington coastal Estuaries. Report for 2020 and 2021
The European green crab (Carcinus maenas) has persisted in Oregon and Washington coastal estuaries since the late 1990s. A strong year class arrived in the Davidson Current during the 1998 El Niño, but numbers decreased and remained below 1 per trap per day until the arrival of the 2015-2016 El Niño. Ocean indices indicate that California was the predominate source of larvae prior to the 2015-2016 El Niño (Behrens Yamada & Kosro, Behrens Yamada, Peterson & Kosro, 2015). Since then, numbers have increased steadily to an average of around 6 crabs per trap per day for Yaquina and Coos estuaries, with maximums of up to 25- 28 per trap. Measurable ecological impact is predicted to occur around 10 per trap (Grosholz et al. 2011). Between the two El Niños recruitment of young green crabs to these estuaries was sporadic with many years of recruitment failure. But since 2015 recruitment has been good every year. Since green crabs live for 6 years, these recent strong year classes can produce larvae until 2027. Evidence suggests that the Davidson Current transporting larvae from California during the winter is no longer the only source of larvae for our coastal estuaries (Behrens Yamada, Fisher and Kosro 2021). Now that populations in Oregon, Washington and British Columbia have built up, we have evidence for local production and for larvae sources from a genetically distinct population on Vancouver Island (Alan Shanks and Carolyn Tepolt, personal communication). The current cooler ocean conditions could hold recruitment in check, but a return to high PDO and strong El Niño patterns would signal good recruitment and higher green crab densities.
Even though green crab abundance in Oregon and Washington is still low when compared to Europe, eastern North America, Tasmania, California and the west coast of Vancouver Island, it is imperative to continue monitoring efforts for two reasons:
1) To elucidate the process of range expansion and population persistence of European green crabs. It could serve as a model for the spread of other non-indigenous species with planktonic larvae.
2) To predict the arrival of strong year classes from ocean conditions and to alert managers and shellfish growers of possible increases in predation pressure from this invader
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Status of the European Green Crab, Carcinus maenas, in Oregon and Washington coastal Estuaries in 2017
The European green crab (Carcinus maenas) has persisted in Oregon and Washington coastal estuaries since the late 1990’s. After the arrival of a strong year class in 1998, significant recruitment to the populations occurred only in 2005, 2006, 2015, 2016 and 2017. Warm winter water temperatures, high Pacific Decadal Oscillation (PDO) and Multivariate ENSO (El Niño Southern Oscillation) Indices, weak southward shelf currents in March and April and a high abundance of southern copepods are all correlated with strong year classes and vice versa (Behrens Yamada Peterson and Kosro 2015). Prior to 2015, green crabs were too rare to exert measurable effects on the native benthic community and on shellfish culture in Oregon and Washington. Following the recent strong El Niño, however, we documented the arrival of three strong year classes in 2015, 2016 and 2017. Average catch rates in over the last three years steadily increased from 0.5 to 0.8 and to 1.9 crabs per trap. These catches are much higher than in any of the previous years, including 1998. Since green crabs live for 6 years, these three consecutive year classes will provide larvae until 2023. A switch to cooler ocean conditions in the coming years will result in poor recruitment, but a return to high PDO and strong El Niño patterns would signal good recruitment and higher green crab densities. For example, green crabs were first documented in New England in 1817, but it took warm ocean conditions during the 1950’s for their numbers to build to a level at which they decimated the soft-shelled clam industry in Maine. With the recent warm trend on the East Coast, green crabs are again abundant. Not only are they preying on shellfish, they are also damaging valuable eelgrass habitat by ripping up the plants in search of food (Neckles 2015).
Even though green crab abundance in Oregon and Washington is still low when compared to Europe, eastern North America, Tasmania, California and the west coast of Vancouver Island, it is imperative to continue monitoring efforts for two reasons:
1) to elucidate the process of range expansion and population persistence of this model non-indigenous marine species with planktonic larvae, and
2) to predict the arrival of strong year classes from ocean conditions and alert managers and shellfish growers of possible increases in predation pressure from this invader
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Status of the European Green Crab, Carcinus maenas, in Oregon and Washington coastal estuaries in 2019
The European green crab (Carcinus maenas) has persisted in Oregon and Washington coastal estuaries since the late 1990s. After the arrival of a strong year class in 1998, significant recruitment to the populations occurred only in 2003, 2005, 2006, 2010, 2015, 2016, 2017, 2018 and 2019. Warm winter water temperatures, high Pacific Decadal Oscillation (PDO) and Multivariate ENSO (El Niño Southern Oscillation) Indices, and a high abundance of southern copepods are all correlated with strong year classes and vice versa (Behrens Yamada, Peterson and Kosro 2015; Behrens Yamada, Fisher and Kosro 2020 in review). Prior to 2015, green crabs were too rare (<0.2 per trap) to exert measurable effects on the native benthic community and on shellfish culture in Oregon and Washington. But after the 2015-2016 El Niño, we document the arrival of five strong year classes. Average catches steadily increased from 0.5 crabs per trap, in 2015 to around 3 crabs per trap in 2017 to 2019. The catches in the last 3 years are much higher than in any of the previous years, including 1998. Catches in some hot spots exceed 10 crabs per trap, a level at which measurable ecological impact can be expected (Grosholz et al. 2011). Since green crabs live for 6 years, these five consecutive year classes can produce larvae until 2025. A switch to cooler ocean conditions in the coming years will result in poor recruitment, but a return to high PDO and strong El Niño patterns would signal good recruitment and higher green crab densities. For example, green crabs were first documented in New England in 1817, but it took warm ocean conditions during the 1950s for their numbers to build to a level at which they decimated the soft-shelled clam industry in Maine (Welch 1968). With the recent warm trend on the East Coast, green crabs are again abundant. Not only are they preying on shellfish, they are also damaging valuable eelgrass habitat by ripping up the plants in their search for food (Neckles 2015).
Even though green crab abundance in Oregon and Washington is still low when compared to Europe, eastern North America, Tasmania, California and the west coast of Vancouver Island, it is imperative to continue monitoring efforts for two reasons:
1) to elucidate the process of range expansion and population persistence of this model non-indigenous marine species with planktonic larvae, and
2) to predict the arrival of strong year classes from ocean conditions and alert managers and shellfish growers of possible increases in predation pressure from this invader
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