Community unity: Experimental evidence for meiofauna and macrofauna

The response of two different size classes of marine benthos, macrofauna and meiofauna, to manipulation of disturbance/predation and size specific utilization of biogenic structural refuges by each benthic size category were studied in an intertidal sandflat in Virginia. A field investigation was conducted during August and September 1980 in the same Diopatra tube system which Woodin (1978; 1981) previously utilized for macrofauna I experiments. Predator/disturber exclusion cages were employed to experimentally evaluate changes in patterns of abundance of both meiofauna and macrofauna in areas of varying Diopatra tube densities (0, 1, 3 or 6 Diopatra 0.01 m–2). Samples were collected for macrofauna and meiofauna in areas immediately adjacent to tubes (= inner) and in outer areas with no tubes present from all treatment (caged or uncaged) and tube density (0, 1, 3, 6) combinations after 2 and 4 weeks. A significant increase in total macrofaunal polychaetes, nematodes and copepods was recorded inside cages after 2 and 4 weeks. Those species which were numerically abundant in control sites were also dominant inside cages. Adult densities of the bivalve, Gemma gemma increased inside cages after 2 weeks but declined dramatically after 4 weeks. Juvenile Gemma abundances, unlike those of the adults, increased inside enclosures after both 2 and 4 weeks. Along with the density increases noted in cages, a variety of main effects (i.e., tube number or position) and interactions were revealed, but these were not consistent even among benthos of similar sizes. Although densities of both meiofauna and selected macrofauna increased over similar time scales in response to predator/disturber exclusion, their spatial patterns and relationships with tubes were highly variable. Our analyses of spatial patterns of macrofauna and meiofauna in caged and uncaged sites do not fit our a priori predictions necessary to support a refuge hypothesis for all meiofauna and macrofauna by Diopatra tubes. The discrepancies between the findings of this study and earlier reports of macrofaunal utilization of Diopatra tube-caps as refuges may be related to yearly changes in community composition and/or predator/disturber activity or possibly the time scale of experiments reported here. We suggest that simultaneous monitoring of various size classes from soft-bottom communities, coupled with field experimentation, would provide valuable insight into the relative importance of forces organizing soft-bottom assemblages

The Structure of σ-Ideals of Compact Sets

Motivated by problems in certain areas of analysis, like measure theory and harmonic analysis, where σ-ideals of compact sets are encountered very often as notions of small or exceptional sets, we undertake in this paper a descriptive set theoretic study of σ-ideals of compact sets in compact metrizable spaces. In the first part we study the complexity of such ideals, showing that the structural condition of being a σ-ideal imposes severe definability restrictions. A typical instance is the dichotomy theorem, which states that σ-ideals which are analytic or coanalytic must be actually either complete coanalytic or else G_δ. In the second part we discuss (generators or as we call them here) bases for σ-ideals and in particular the problem of existence of Borel bases for coanalytic non-Borel σ-ideals. We derive here a criterion for the nonexistence of such bases which has several applications. Finally in the third part we develop the connections of the definability properties of σ-ideals with other structural properties, like the countable chain condition, etc

Modeling interactions of browsing predation, infaunal activity and recruitment in marine soft-sediment habitats

In marine soft-sediment habitats, the sediment surface is altered by activities of sediment dwellers (infauna). Such biogenic disturbance can influence recruitment success if settling larvae and juveniles avoid disturbed sites or if juveniles die as a result of disturbance after settling. Because infauna commonly lose exposed body parts to browsing predators and disturb less sediment as a result, we developed a simulation model to examine the interactions between browsing predation, infaunal adult activity, and recruitment. Sediment disturbance in the model was based on data for the polychaete Abarenicola pacifica. We simulated the activity of two general types of predators: prey nippers, which damaged adults only, and sediment biters, which damaged adults and consumed settled juveniles. As both types of predation rates increased, habitat rejection by settlers decreased, but juvenile mortality increased as settlers landing near damaged adults were killed when those adults resumed activity. When prey nippers were active, the interaction between predation and infaunal activity determined recruitment success, and juvenile mortality was highest at intermediate predation rates. When sediment biters were active, they controlled recruitment success by directly consuming larvae. At low adult worm densities, habitat rejection by settlers and juvenile mortality were both low, and browsing predation did not affect recruitment success. At higher adult densities, net recruitment success increased with the rate of predation by prey nippers (the magnitude of increase depended on bite rate and the length of time juveniles were susceptible to mortality), but it was never enhanced by sediment biters

Global intercomparison of hyper-resolution ECOSTRESS coastal sea surface temperature measurements from the space station with VIIRS-N20

The ECOSTRESS multi-channel thermal radiometer on the Space Station has an unprecedented spatial resolution of 70 m and a return time of hours to 5 days. It resolves details of oceanographic features not detectable in imagery from MODIS or VIIRS, and has open-ocean coverage, unlike Landsat. We calibrated two years of ECOSTRESS sea surface temperature observations with L2 data from VIIRS-N20 (2019–2020) worldwide but especially focused on important upwelling systems currently undergoing climate change forcing. Unlike operational SST products from VIIRS-N20, the ECOSTRESS surface temperature algorithm does not use a regression approach to determine temperature, but solves a set of simultaneous equations based on first principles for both surface temperature and emissivity. We compared ECOSTRESS ocean temperatures to well-calibrated clear sky satellite measurements from VIIRS-N20. Data comparisons were constrained to those within 90 min of one another using co-located clear sky VIIRS and ECOSTRESS pixels. ECOSTRESS ocean temperatures have a consistent 1.01 °C negative bias relative to VIIRS-N20, although deviation in brightness temperatures within the 10.49 and 12.01 µm bands were much smaller. As an alternative, we compared the performance of NOAA, NASA, and U.S. Navy operational split-window SST regression algorithms taking into consideration the statistical limitations imposed by intrinsic SST spatial autocorrelation and applying corrections on brightness temperatures. We conclude that standard bias-correction methods using already validated and well-known algorithms can be applied to ECOSTRESS SST data, yielding highly accurate products of ultra-high spatial resolution for studies of biological and physical oceanography in a time when these are needed to properly evaluate regional and even local impacts of climate change.National Aeronautics and Space Administration | Ref. 80NSSC20K007

Extension and reconstruction theorems for the Urysohn universal metric space

We prove some extension theorems involving uniformly continuous maps of the universal Urysohn space. We also prove reconstruction theorems for certain groups of autohomeomorphisms of this space and of its open subsets.Comment: Final and shortened version, 25 pages, to appear in Czechoslovak Math.

The Obliteration of Truth by Management: Badiou, St. Paul and the Question of Economic Managerialism in Education

This paper considers the questions that Badiou’s theory of the subject poses to cultures of economic managerialism within education. His argument that radical change is possible, for people and the situations they inhabit, provides a stark challenge to the stifling nature of much current educational climate. In 'Saint Paul: The Foundation of Universalism', Badiou describes the current universalism of capitalism, monetary homogeneity and the rule of the count. Badiou argues that the politics of identity are all too easily subsumed by the prerogatives of the marketplace and unable to present, therefore, a critique of the status quo. These processes are, he argues, without the potential for truth. What are the implications of Badiou’s claim that education is the arranging of ‘the forms of knowledge in such a way that truth may come to pierce a hole in them’ (Badiou, 2005, p. 9)? In this paper, I argue that Badiou’s theory opens up space for a kind of thinking about education that resists its colonisation by cultures of management and marketisation and leads educationalists to consider the emancipatory potential of education in a new light

Experimenting with ecosystem interaction networks in search of threshold potentials in real-world marine ecosystems

Thresholds profoundly affect our understanding and management of ecosystem dynamics, but we have yet to develop practical techniques to assess the risk that thresholds will be crossed. Combining ecological knowledge of critical system interdependencies with a large-scale experiment, we tested for breaks in the ecosystem interaction network to identify threshold potential in real-world ecosystem dynamics. Our experiment with the bivalves Macomona liliana and Austrovenus stutchburyi on marine sandflats in New Zealand demonstrated that reductions in incident sunlight changed the interaction network between sediment biogeochemical fluxes, productivity, and macrofauna. By demonstrating loss of positive feedbacks and changes in the architecture of the network, we provide mechanistic evidence that stressors lead to break points in dynamics, which theory predicts predispose a system to a critical transition