5,344 research outputs found
Temperature and food quantity effects on the harpacticoid copepod Nitocra spinipes : combining in vivo bioassays with population modeling
The harpacticoid copepod Nitocra spinipes has become a popular model species for toxicity testing over the past few decades. However, the combined influence of temperature and food shortage, two climate change-related stressors, has never been assessed in this species. Consequently, effects of three temperatures (15, 20 and 25˚C) and six food regimes (between 0 and 5 × 10^5 algal cells/mL) on the life cycle of N. spinipes were examined in this study. Similarly to other copepod species, development times and brood sizes decreased with rising temperatures. Mortality was lowest in the 20˚C temperature setup, indicating a close-by temperature optimum for this species. Decreasing food concentrations led to increased development times, higher mortality and a reduction in brood size. A sex ratio shift toward more females per male was observed for increasing temperatures, while no significant relationship with food concentration was found. Temperature and food functions for each endpoint were integrated into an existing individual-based population model for N. spinipes which in the future may serve as an extrapolation tool in environmental risk assessment. The model was able to accurately reproduce the experimental data in subsequent verification simulations. We suggest that temperature, food shortage, and potentially other climate change-related stressors should be considered in environmental risk assessment of chemicals to account for non-optimal exposure conditions that may occur in the field. Furthermore, we advocate combining in vivo bioassays with population modeling as a cost effective higher tier approach to assess such considerations
The role of BoFLC2 in cauliflower (Brassica oleracea var. botrytis L.) reproductive development
In agricultural species that are sexually propagated or whose marketable organ is a reproductive structure, management of the flowering process is critical. Inflorescence development in cauliflower is particularly complex, presenting unique challenges for those seeking to predict and manage flowering time. In this study, an integrated physiological and molecular approach was used to clarify the environmental control of cauliflower reproductive development at the molecular level. A functional allele of BoFLC2 was identified for the first time in an annual brassica, along with an allele disrupted by a frameshift mutation (boflc2). In a segregating F2 population derived from a cross between late-flowering (BoFLC2) and early-flowering (boflc2) lines, this gene behaved in a dosage-dependent manner and accounted for up to 65% of flowering time variation. Transcription of BoFLC genes was reduced by vernalization, with the floral integrator BoFT responding inversely. Overall expression of BoFT was significantly higher in early-flowering boflc2 lines, supporting the idea that BoFLC2 plays a key role in maintaining the vegetative state. A homologue of Arabidopsis VIN3 was isolated for the first time in a brassica crop species and was up-regulated by two days of vernalization, in contrast to findings in Arabidopsis where prolonged exposure to cold was required to elicit up-regulation. The correlations observed between gene expression and flowering time in controlled-environment experiments were validated with gene expression analyses of cauliflowers grown outdoors under 'natural' vernalizing conditions, indicating potential for transcript levels of flowering genes to form the basis of predictive assays for curd initiation and flowering time
Biological processes and links to the physics
Analysis of the temporal and spatial variability of biological processes and identification of the main variables that drive the dynamic regime of marine ecosystems is complex. Correlation between physical variables and long-term changes in ecosystems has routinely been identified, but the specific mechanisms involved remain often unclear. Reasons for this could be various: the ecosystem can be very sensitive to the seasonal timing of the anomalous physical forcing; the ecosystem can be contemporaneously influenced by many physical variables and the ecosystem can generate intrinsic variability on climate time scales. Marine ecosystems are influenced by a variety of physical factors, e.g., light, temperature, transport, turbulence. Temperature has a fundamental forcing function in biology, with direct influences on rate processes of organisms and on the distribution of mobile species that have preferred temperature ranges. Light and transport also affect the physiology and distribution of marine organisms. Small-scale turbulence determines encounter between larval fish and their prey and additionally influences the probability of successful pursuit and ingestion.
The impact of physical forcing variations on biological processes is studied through long-term observations, process studies, laboratory experiments, retrospective analysis of existing data sets and modelling. This manuscript reviews the diversity of physical influences on biological processes, marine organisms and ecosystems and their variety of responses to physical forcing with special emphasis on the dynamics of zooplankton and fish stocks
Somatic growth dynamics of West Atlantic hawksbill sea turtles: a spatio-temporal perspective
This is the final version of the article. Available from the publisher via the DOI in this record.Somatic growth dynamics are an integrated response to environmental conditions. Hawksbill
sea turtles (Eretmochelys imbricata) are long-lived, major consumers in coral reef habitats that move over
broad geographic areas (hundreds to thousands of kilometers). We evaluated spatio-temporal effects on
hawksbill growth dynamics over a 33-yr period and 24 study sites throughout the West Atlantic and explored
relationships between growth dynamics and climate indices. We compiled the largest ever data set
on somatic growth rates for hawksbills – 3541 growth increments from 1980 to 2013. Using generalized additive
mixed model analyses, we evaluated 10 covariates, including spatial and temporal variation, that could
affect growth rates. Growth rates throughout the region responded similarly over space and time. The lack
of a spatial effect or spatio-temporal interaction and the very strong temporal effect reveal that growth rates
in West Atlantic hawksbills are likely driven by region-wide forces. Between 1997 and 2013, mean growth
rates declined significantly and steadily by 18%. Regional climate indices have significant relationships with
annual growth rates with 0- or 1-yr lags: positive with the Multivariate El Niño Southern Oscillation Index
(correlation = 0.99) and negative with Caribbean sea surface temperature (correlation = −0.85). Declines
in growth rates between 1997 and 2013 throughout the West Atlantic most likely resulted from warming
waters through indirect negative effects on foraging resources of hawksbills. These climatic influences are
complex. With increasing temperatures, trajectories of decline of coral cover and availability in reef habitats
of major prey species of hawksbills are not parallel. Knowledge of how choice of foraging habitats, prey
selection, and prey abundance are affected by warming water temperatures is needed to understand how
climate change will affect productivity of consumers that live in association with coral reefs
The role of BoFLC2 in cauliflower (Brassica oleracea var. botrytis L.) reproductive development
In agricultural species that are sexually propagated or whose marketable organ is a reproductive structure, management of the flowering process is critical. Inflorescence development in cauliflower is particularly complex, presenting unique challenges for those seeking to predict and manage flowering time. In this study, an integrated physiological and molecular approach was used to clarify the environmental control of cauliflower reproductive development at the molecular level. A functional allele of BoFLC2 was identified for the first time in an annual brassica, along with an allele disrupted by a frameshift mutation (boflc2). In a segregating F2 population derived from a cross between late-flowering (BoFLC2) and early-flowering (boflc2) lines, this gene behaved in a dosage-dependent manner and accounted for up to 65% of flowering time variation. Transcription of BoFLC genes was reduced by vernalization, with the floral integrator BoFT responding inversely. Overall expression of BoFT was significantly higher in early-flowering boflc2 lines, supporting the idea that BoFLC2 plays a key role in maintaining the vegetative state. A homologue of Arabidopsis VIN3 was isolated for the first time in a brassica crop species and was up-regulated by two days of vernalization, in contrast to findings in Arabidopsis where prolonged exposure to cold was required to elicit up-regulation. The correlations observed between gene expression and flowering time in controlled-environment experiments were validated with gene expression analyses of cauliflowers grown outdoors under 'natural' vernalizing conditions, indicating potential for transcript levels of flowering genes to form the basis of predictive assays for curd initiation and flowering time
Temperature and food quantity effects on the harpacticoid copepod <i>Nitocra spinipes</i>: combining in vivo bioassays with population modeling
The harpacticoid copepod Nitocra spinipes has become a popular model species for toxicity testing over the past few decades. However, the combined influence of temperature and food shortage, two climate change-related stressors, has never been assessed in this species. Consequently, effects of three temperatures (15, 20 and 25°C) and six food regimes (between 0 and 5 × 105 algal cells/mL) on the life cycle of N. spinipes were examined in this study. Similarly to other copepod species, development times and brood sizes decreased with rising temperatures. Mortality was lowest in the 20°C temperature setup, indicating a close-by temperature optimum for this species. Decreasing food concentrations led to increased development times, higher mortality and a reduction in brood size. A sex ratio shift toward more females per male was observed for increasing temperatures, while no significant relationship with food concentration was found. Temperature and food functions for each endpoint were integrated into an existing individual-based population model for N. spinipes which in the future may serve as an extrapolation tool in environmental risk assessment. The model was able to accurately reproduce the experimental data in subsequent verification simulations. We suggest that temperature, food shortage, and potentially other climate change-related stressors should be considered in environmental risk assessment of chemicals to account for non-optimal exposure conditions that may occur in the field. Furthermore, we advocate combining in vivo bioassays with population modeling as a cost effective higher tier approach to assess such considerations
Bridging the gap between pupping and molting phenology: behavioral and ecological drivers in Weddell seals
Thesis (Ph.D.) University of Alaska Fairbanks, 2018In Antarctica, the narrow window of favorable conditions constrains the life history phenology of female Weddell seals (Leptonychotes weddellii) such that pupping, breeding, foraging, and molting occur in quick succession during summer; however, the carry-over effects from one life history event to another are unclear. In this dissertation, I characterize the phenological links between molting and pupping, and evaluate feeding behavior and ice dynamics as mechanistic drivers. First, I review the contributions of natural and sexual selection to the evolution of molting strategies in the contexts of energetics, habitat, function, and physiology. Many polar birds and mammals adhere to an analogous biannual molting strategy wherein the thin, brown summer feathers/fur are replaced with thick, white winter feathers/fur. Polar pinnipeds are an exception to the biannual molting paradigm; most rely on blubber for insulation and exhibit a single molt per year. Second, I describe the duration and timing of the Weddell seal molt based on data from 4,000 unique individuals. In adult females, I found that successful reproduction delays the molt by approximately two weeks relative to non-reproductive individuals. Using time-depth recorder data from 59 Weddell seals at the crucial time between pupping and molting, I report a striking mid-summer shallowing of seal dive depths that appears to follow a vertical migration of fishes during the summer phytoplankton bloom. The seals experience higher foraging success during this vertical shift in the prey distribution, which allows them to re-gain mass quickly before the molt. Across four years of study, later ice break-out resulted in later seal dive shallowing and later molt. In combination, the data presented in this dissertation suggest that molting, foraging, and pupping phenology are linked in Weddell seals and are affected by ice break-out timing.National Science Foundation Graduate Research Fellowship Program Grant No. DGE-124278
Report of the 2005 Workshop on Ocean Ecodynamics Comparison in the Subarctic Pacific
I. Scientific Issues Posed by OECOS
II. Participant Contributions to the OECOS Workshop
A. ASPECTS OF PHYTOPLANKTON ECOLOGY IN THE SUBARCTIC PACIFIC
Microbial community compositions by Karen E. Selph
Subarctic Pacific lower trophic interactions: Production-based grazing rates and grazing-corrected production rates by Nicholas Welschmeyer
Phytoplankton bloom dynamics and their physiological status in the western subarctic
Pacific by Ken Furuya
Temporal and spatial variability of phytoplankton biomass and productivity in the northwestern Pacific by Sei-ichi Saitoh, Suguru Okamoto, Hiroki Takemura and Kosei Sasaoka
The use of molecular indicators of phytoplankton iron limitation by Deana Erdner
B. IRON CONCENTRATION AND CHEMICAL SPECIATION
Iron measurements during OECOS by Zanna Chase and Jay Cullen 25 The measurement of iron, nutrients and other chemical components in the northwestern North Pacific Ocean by Kenshi Kuma
The measurement of iron, nutrients and other chemical components in the northwestern North Pacific Ocean by Kenshi Kuma
C. PHYSICAL OCEANOGRAPHY, FINE-SCALE DISTRIBUTION PATTERNS AND AUTONOMOUS DRIFTERS
The use of drifters in Lagrangian experiments: Positives, negatives and what can really be measured by Peter Strutton
The interaction between plankton distribution patterns and vertical and horizontal physical processes in the eastern subarctic North Pacific by Timothy J. Cowles
D. MICROZOOPLANKTON
Microzooplankton processes in oceanic waters of the eastern subarctic Pacific:
Project OECOS by Suzanne Strom
Functional role of microzooplankton in the pelagic marine ecosystem during phytoplankton blooms in the western subarctic Pacific by Takashi Ota and Akiyoshi Shinada
E. MESOZOOPLANKTON
Vertical zonation of mesozooplankton, and its variability in response to food availability, density stratification, and turbulence by David L. Mackas and Moira Galbraith
Marine ecosystem characteristics and seasonal abundance of dominant calanoid copepods
in the Oyashio region by Atsushi Yamaguchi, Tsutomu Ikeda and Naonobu Shiga
OECOS: Proposed mesozooplankton research in the Oyashio region, western subarctic
Pacific by Tsutomu Ikeda
Some background on Neocalanus feeding by Michael Dagg
Size and growth of interzonally migrating copepods by Charles B. Miller
Growth of large interzonal migrating copepods by Toru Kobari
F. MODELING
Ecosystem and population dynamics modeling by Harold P. Batchelder
III. Reports from Workshop Breakout Groups
A. PHYSICAL AND CHEMICAL ASPECTS WITH EMPHASIS ON IRON AND IRON SPECIATION
B. PHYTOPLANKTON/MICROZOOPLANKTON STUDIES
C. MESOZOOPLANKTON STUDIES
IV. Issues arising during the workshop
A. PHYTOPLANKTON STOCK VARIATIONS IN HNLC SYSTEMS AND TROPHIC CASCADES IN THE NANO AND MICRO REGIMES
B. DIFFERENCES BETWEEN EAST AND WEST IN SITE SELECTION FOR OECOS TIME SERIES
C. TIMING OF OECOS EXPEDITIONS
D. CHARACTERIZATION OF PHYSICAL OCEANOGRAPHY
V. Concluding Remarks
VI. References
(109 page document
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