Stress-induced apoptosis in sea urchin embryogenesis

We find that early sea urchin embryos have the capability to induce programmed cell death, or apoptosis, in response to chemical and physical stress. Strongylocentrotus purpuratus embryos (fertilized, 4 cell, 16 cell, 64 cell, and early blastula) were exposed to known cytotoxins, in order to determine when apoptosis occurs naturally and in response to stress. Using cell permeability as an indicator of early stage apoptosis, caspase activation as a mid-stage indicator, and DNA fragmentation as a late stage indicator, we find that during the cleavage stage of embryogenesis apoptosis is almost completely absent. However, a statistically significant (p<0.001) rise in apoptosis in stressed embryos is evident around 24 h after fertilization, during the early blastula stage and shortly after hatching. Before this stage, exposed embryos show no statistically significant increases in apoptosis in comparison to the controls. This pattern of apoptosis in development is similar to that seen in lower vertebrate models in which stress-induced apoptosis occurs only around the mid-blastula transition. We conclude that apoptosis may be used to rid embryos of aberrant or damaged cells in early development, but this response is stage-dependant. Repair, rather than apoptosis, may be utilized during earlier stages, or alternatively, embryos exposed to such stressors may continue development with damaged cells and perhaps damaged DNA. Our continued studies will focus on these alternative hypotheses.     

Nd and Sr isotopic variations of Early Paleozoic oceans

We report¹⁴³Nd/¹⁴⁴Nd and⁸⁷Sr/⁸⁶Sr isotopic data for Lower Paleozoic phosphatic brachiopod and conodont fossils. The data appear to represent the isotopic values of Early Paleozoic seawaters. We show that different paleoceanic water masses can be distinguished on the basis of their ε_Nd signatures. Two sides of what is classically considered one circulating Iapetus Ocean have different ε_Nd signatures from at least the Middle Cambrian until the Late Middle Ordovician. We infer two ocean basins between North America and Baltica separated by an island and/or shoal circulation barrier. Thus, it appears necessary to redefine the area of the Iapetus Ocean. The ε_Nd signature of the redefined smaller Iapetus Ocean ranges from −5 to −9 and the ε_Nd signature of the larger, coeval Panthalassa Ocean, including part of what was formerly called the Iapetus Ocean, ranges from −10 to −20. The first time that the ε_Nd values are identical in these two water masses is coincident with the onset of the Taconic Orogeny of North America. The paleogeographic geometry we infer from this work is consistent with paleogeographic reconstructions having the Baltica continent at very high latitudes in the Early/Middle Ordovician. The ε_Nd and faunal distribution support temperature-controlled conodont faunal provinciality. A rough mean age for exposed continental crust in the Early Paleozoic can be obtained from the average ε_Nd value of Early Paleozoic Oceans. The data suggest that the mean age of the crust as a function of time has remained essentially constant or even decreased during the past 500 Ma, and suggest substantial additions of new crust to the continents through the Phanerozoic.     

Resource partitioning among air‐breathing marine predators: are body size and mouth diameter the major determinants?

Although the body size of consumers may be a determinant factor in structuring food webs, recent evidence indicates that body size may fail to fully explain differences in the resource use patterns of predators in some situations. Here we compared the trophic niche of three sympatric and sexually dimorphic air‐breathing marine predators (the South American sea lion, Otaria flavescens, the South American fur seal, Arctocephalus australis, and the Magellanic penguin, Spheniscus magellanicus) in three areas of the Southwestern Atlantic Ocean (Río de la Plata and adjoining areas, Northern Patagonia and Southern Patagonia), in order to assess the importance of body size and mouth diameter in determining resource partitioning. Body weight and palate/bill breadth were used to characterize the morphology of each sex and species, whereas the trophic niche was assessed through the use of stable isotope ratios of carbon and nitrogen. The quantitative method Stable Isotope Bayesian Ellipses in R (SIBER) was used to compute the area of the Bayesian ellipses and the overlap of the isotopic niches. The results showed that morphological similarity was significantly correlated with isotopic distance between groups within the δ¹³C–δ¹⁵N bi‐plot space in the Río de la Plata area, but not in Northern and Southern Patagonia. Furthermore, resource partitioning between groups changed regionally, and some morphologically distinct groups exhibited a large trophic overlap in certain areas, such as the case of male penguins and male sea lions in Southern Patagonia. Conversely, female sea lions always overlapped with the much larger males of the same species, but never overlapped with the morphologically similar male fur seals. These results indicate that body size and mouth diameter are just two of the factors involved in resource partitioning within the guild of air‐breathing predators considered here, and for whom – under certain environmental conditions – other factors are more important than morphology.     

Community perspectives on integrated coastal management: Voices from the Annapolis Basin area,Nova Scotia,Canada

This paper seeks to address the missing dimension of the place of Maritime communities in Canadian Integrated Coastal Management (ICM). This work is part of a larger network of projects on ICM through the participatory Coastal Community University Research Alliance. The implementation of ICM with full community involvement is a challenge, for example: communities are not unified or homogenous units, power varies among stakeholders, and silo constructs and turf wars discourage involvement of the wider public. In 2007, a survey of nine community-based organizations and associations and a First Nation community, located within the Annapolis Basin and surrounding areas of the Nova Scotia side of the Bay of Fundy was conducted. The purpose of the survey was to better understand how the concept of ICM is conceptualized and acted upon by local communities and to draw upon this to enrich ICM theory.Approximately 30 projects representing community-based ICM initiatives over the last 10 years were identified, including: capacity building, habitat and stock enhancement/ management programs and responses to new policies or legislative interventions. Several enabling and constraining factors for community involvement in ICM were identified. One key finding is a major difference between community and government approaches. Government ICM initiatives have captured some aspects of the environmental and economic management issues, but have generally failed to consider cultural and social components. They have also failed to take into account the interconnections within and between human and ecological systems. Community members report that government is more interested in forming partnerships with the corporate sector than with the people who rely on local resources. From the community perspective, dealing with the resulting power imbalances must involve revisiting the “core values” that underpin regulation and resource exploitation.This study demonstrates that communities are usually the “first responders"” for many ecological problems, and there is a willingness to take responsibility for the management of resources. ICM is already embedded in on-going community projects, networks and forums. These initiatives promote the principles identified in Canada's Oceans Act and Oceans Strategy, but the relevant government agencies have provided little support to them. ICM has the potential to bring together many issues that can be addressed by the multi-stakeholder process, but this needs to be facilitated by on-going government collaborations, contributions and recognition.     

Seasonal changes of antioxidant and oxidative parameters in the coral Pocillopora capitata on the Pacific coast of Mexico

The physiological responses of the coral Pocillopora capitata to environmental conditions common in winter and summer were studied in 2007 during February–March (winter) and June–July (summer) at La Boquita reef (Manzanillo, Colima, Mexico). Shallow and deep sampling stations were established at different distances from a small jetty built next to the Juluapan Lagoon. We analyzed superoxide radicals () and lipid peroxidants (TBARS); the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), and glutathione‐S‐transferase (GST); chlorophyll a (Chl a), zooxanthellae density (ZD); and mycosporine‐like amino acids (MAAs). Our results showed that the , TBARS, CAT, GST, MAAs, and Chl a, levels were significantly higher in summer (P < 0.05); no seasonal difference was found for GPx, GR or ZD. We found significant differences (P < 0.05) in winter only for Chl a and ZD at shallow sites and, in contrast, for at deeper sites. The results of this study indicate that increasing temperature and radiation associated with seasonal changes (from winter to summer), the efficiency of the enzymes GST, CR and GPX, and the production of MAAs together form a powerful mechanism for P. capitata to offset the detrimental effects of environmental change.     

On the existence of long-term periodicities in solar activity

Solar Physics - Application of the non-integer technique of power spectral analysis has yielded evidence for long-term periodicities in the Zürich sunspot series. Although the spectrum shows...     

Nd isotopic variations of Phanerozoic paleoceans

The size of various Phanerozoic paleoceans, determined from paleogeographic maps, provides a framework for assigningε_Nd measurements of primary authigenic marine minerals to individual paleoceans and for establishing theirε_Nd versus age curves. We report newε_Nd data (in the range from 80 to 750 Ma) for the largest Phanerozoic and Late Precambrian paleocean, the Pacific/Panthalassa Ocean (PPO), and limited data on some small Paleozoic paleoceans. These new data and all other published data on paleoceanε_Nd values are used to determine the trends through time ofε_Nd in seven Phanerozoic paleoceans. The variations in paleoceanε_Nd curves are due to changes in the rate of crustal additions and in paleoceanic geometry. From these data we can calculate a meanε_Nd curve and a mean Nd model age curve for Phanerozoic seawater. These curves show large variations with age and reflect the variations ofε_Nd in erosion products from the continents as a function of age. The high erosion rates of young, uplifted areas enhanceε_Nd and Nd model age variations of Phanerozoic seawater. This makes it difficult to quantitatively recover crustal addition rates from these curves; however, it makes the episodic nature of continental additions more evident.