Phytoplankton Response to Intrusions of Slope Water on the West Florida Shelf: Models and Observations

Previous hypotheses had suggested that upwelled intrusions of nutrient-rich Gulf of Mexico slope water onto the West Florida Shelf (WFS) led to formation of red tides of Karenia brevis. However, coupled biophysical models of (1) wind- and buoyancy-driven circulation, (2) three phytoplankton groups (diatoms, K. brevis, and microflagellates), (3) these slope water supplies of nitrate and silicate, and (4) selective grazing stress by copepods and protozoans found that diatoms won in one 1998 case of no light limitation by colored dissolved organic matter (CDOM). The diatoms lost to K. brevis during another CDOM case of the models. In the real world, field data confirmed that diatoms were indeed the dominant phytoplankton after massive upwelling in 1998, when only a small red tide of K. brevis was observed. Over a 7-month period of the CDOM-free scenario the simulated total primary production of the phytoplankton community was ∼1.8 g C m−2 d−1 along the 40-m isobath of the northern WFS, with the largest accumulation of biomass on the Florida Middle Ground (FMG). Despite such photosynthesis, these models of the WFS yielded a net source of CO2 to the atmosphere during spring and summer and suggested a small sink in the fall. With diatom losses of 90% of their daily carbon fixation to herbivores the simulation supported earlier impressions of a short, diatom-based food web on the FMG, where organic carbon content of the surficial sediments is tenfold those of the surrounding seabeds. Farther south, the simulated near-bottom pools of ammonium were highest in summer, when silicon regeneration was minimal, leading to temporary Si limitation of the diatoms. Termination of these upwelled pulses of production by diatoms and nonsiliceous microflagellates mainly resulted from nitrate exhaustion in the model, however, mimicking most del15PON observations in the field. Yet, the CDOM-free case of the models failed to replicate the observed small red tide in December 1998, tagged with the del15N signature of nitrogen fixation. A large red tide of K. brevis did form in the CDOM-rich case, when estuarine supplies of CDOM favored the growth of the shade-adapted, ungrazed dinoflagellates. The usual formation of large harmful algal blooms of \u3e1 ug chl L−1 (105 cells L−1) in the southern part of the WFS, between Tampa Bay and Charlotte Harbor, must instead depend upon local aeolian and estuarine supplies of nutrients and CDOM sun screen, not those from the shelf break. In the absence of slope water supplies, local upwelling instead focuses nitrate-poor innocula of co-occurring K. brevis and nitrogen fixers at coastal fronts for both aggregation and transfer of nutrients between these phytoplankton groups

The complexity of interacting nutritional drivers behind food selection, a review of northern cervids

The research literature on food selection by large herbivores is extensive. Still, we are generally lacking in our knowledge of the influence of potentially interacting chemical contents of the food. We made a qualitative review of a systematic literature search of studies that empirically link chemical contents of food to the food selection by northern cervids (genera Alces, Capreolus, Cervus, Dama, Odocoileus, Rangifer). We found that although the majority of the 98 relevant studies measuring any given food constituent (energy, protein, fiber, minerals, plant secondary metabolites) provided support for it acting as a driver of food selection (in either a negative or positive way), there was little support for the traditional hypotheses of maximization or limitation of any single constituent. Rather, because of the animals’ need to acquire an appropriate intake of several constituents at the same time, our review highlights how new empirical stud- ies need to focus on several food constituents in synchrony: (1) Study designs should capture sufficient variation in the content of food constituents in order to tease apart their many co-variations; and (2) insights about nutritional drivers may be lost if one uses only composite currencies such as crude energy, crude fiber, ash, or tannins, which may mask contrasting selection patterns of the lumped constituents. Season had an apparent influence on the selection of some food constituents, particularly various fiber frac- tions. In contrast, our review revealed a lack of evidence that cervids more strongly select for protein in summer than they do in winter. Our overall conclusion of the review is that interacting chemical contents of food make the nutritional value of a given food type into a varying entity. To better elucidate this varia- tion, we need new technologies that non-invasively capture nutrient intake of free-ranging animals, across seasons.The complexity of interacting nutritional drivers behind food selection, a review of northern cervidspublishedVersio

Environmentalism, pre-environmentalism, and public policy

In the last decade, thousands of new grassroots groups have formed to oppose environmental pollution on the basis that it endangers their health. These groups have revitalized the environmental movement and enlarged its membership well beyond the middle class. Scientists, however, have been unable to corroborate these groups' claims that exposure to pollutants has caused their diseases. For policy analysts this situation appears to pose a choice between democracy and science. It needn't. Instead of evaluating the grassroots groups from the perspective of science, it is possible to evaluate science from the perspective of environmentalism. This paper argues that environmental epidemiology reflects ‘pre-environmentalist’ assumptions about nature and that new ideas about nature advanced by the environmental movement could change the way scientists collect and interpret data.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45449/1/11077_2005_Article_BF01006494.pd

Re-appropriating the political through enacting a pedagogical politics of place

This paper critically analyses the post-political thesis, highlighting its universalising and agencygrabbing tendencies. Drawing on my own family life, anarchist theory and long-standing traditions of ‘properly’ political placemaking by past and present grassroots actors, the paper unsettles two interrelated claims on which the post-political thesis sits. First, that the political (le politique) is in retreat. Second, that ‘proper’ politics constitutes a confrontational set of relations. Informed by empirical observations I present an existing form of rigorous political encounter enacted in anarchistinfluenced social centres. The politics on offer here has a supportive pedagogical quality to it and, crucially, there are semblances of this pedagogical politics found in multiple sites. Focusing on the ‘micro-physics of power’ at work in social centres, I show how such organisational practices counter the predetermined finalities of the post-political condition by enacting what I call ‘equality-as-tactic’. Community here is not an empty vessel that can be easily filled with ‘empty signifiers’. On the contrary, post-political practices tend to crack under the scrutiny of a pedagogical politics aimed at equalising participation in the decisionmaking process