Mississippi River diversions and phytoplankton dynamics in deltaic Gulf of Mexico estuaries: A review

River systems worldwide have become substantially influenced by human activities, including land use changes, river diversion operations, and flood control measures. Some of the unambiguous and best studied examples of effects of enhanced eutrophication on biotic resources can be found in Louisiana estuaries at the terminus of the Mississippi-Atchafalaya River system. The Mississippi River delta has experienced large losses of coastal wetlands due to a combination of human impacts and sea-level rise. State and Federal agencies are moving ahead with plans for building large-scale river sediment diversions, which will capture maximum sediment during spring flood pulses and direct a sediment subsidy into the eroding coastal basins. These large-scale river sediment diversions will also substantially increase freshwater and nutrient inputs and are likely to affect algal bloom formation, including harmful cyanobacterial blooms. There are concerns that discharge of river water containing high concentrations of N, P and Si may trigger algal blooms in the coastal receiving basins. River sediment diversions, as any other flood pulsing, will likely be disruptive to the coastal ecology and so balancing the benefits of slowing coastal land loss against potential negative effects on water quality remains a formidable management challenge. We review here the physical, chemical and biological factors affecting primary production in shallow coastal systems and provide known data on ecosystem response to freshwater diversions, large and small. We also discuss potential management approaches to mitigate the negative impacts of the diversions on the health and stability of the coastal food webs

Divergent gene expression among phytoplankton taxa in response to upwelling

Frequent blooms of phytoplankton occur in coastal upwelling zones creating hotspots of biological productivity in the ocean. As cold, nutrient-rich water is brought up to sunlit layers from depth, phytoplankton are also transported upwards to seed surface blooms that are often dominated by diatoms. The physiological response of phytoplankton to this process, commonly referred to as shift-up, is characterized by increases in nitrate assimilation and rapid growth rates. To examine the molecular underpinnings behind this phenomenon, metatranscriptomics was applied to a simulated upwelling experiment using natural phytoplankton communities from the California Upwelling Zone. An increase in diatom growth following 5 days of incubation was attributed to the genera Chaetoceros and Pseudo-nitzschia. Here, we show that certain bloom-forming diatoms exhibit a distinct transcriptional response that coordinates shift-up where diatoms exhibited the greatest transcriptional change following upwelling; however, comparison of co-expressed genes exposed overrepresentation of distinct sets within each of the dominant phytoplankton groups. The analysis revealed that diatoms frontload genes involved in nitrogen assimilation likely in order to outcompete other groups for available nitrogen during upwelling events. We speculate that the evolutionary success of diatoms may be due, in part, to this proactive response to frequently encountered changes in their environment

Pseudo-nitzschia physiological ecology, phylogeny, toxicity, monitoring and impacts on ecosystem health

This paper is not subject to U.S. copyright. The definitive version was published in Harmful Algae 14 (2012): 271-300, doi:10.1016/j.hal.2011.10.025.Over the last decade, our understanding of the environmental controls on Pseudo-nitzschia blooms and domoic acid (DA) production has matured. Pseudo-nitzschia have been found along most of the world's coastlines, while the impacts of its toxin, DA, are most persistent and detrimental in upwelling systems. However, Pseudo-nitzschia and DA have recently been detected in the open ocean's high-nitrate, low-chlorophyll regions, in addition to fjords, gulfs and bays, showing their presence in diverse environments. The toxin has been measured in zooplankton, shellfish, crustaceans, echinoderms, worms, marine mammals and birds, as well as in sediments, demonstrating its stable transfer through the marine food web and abiotically to the benthos. The linkage of DA production to nitrogenous nutrient physiology, trace metal acquisition, and even salinity, suggests that the control of toxin production is complex and likely influenced by a suite of environmental factors that may be unique to a particular region. Advances in our knowledge of Pseudo-nitzschia sexual reproduction, also in field populations, illustrate its importance in bloom dynamics and toxicity. The combination of careful taxonomy and powerful new molecular methods now allow for the complete characterization of Pseudo-nitzschia populations and how they respond to environmental changes. Here we summarize research that represents our increased knowledge over the last decade of Pseudo-nitzschia and its production of DA, including changes in worldwide range, phylogeny, physiology, ecology, monitoring and public health impacts

Concurrent Exposure of Bottlenose Dolphins (Tursiops truncatus) to Multiple Algal Toxins in Sarasota Bay, Florida, USA

Sentinel species such as bottlenose dolphins (Tursiops truncatus) can be impacted by large-scale mortality events due to exposure to marine algal toxins. In the Sarasota Bay region (Gulf of Mexico, Florida, USA), the bottlenose dolphin population is frequently exposed to harmful algal blooms (HABs) of Karenia brevis and the neurotoxic brevetoxins (PbTx; BTX) produced by this dinoflagellate. Live dolphins sampled during capture-release health assessments performed in this region tested positive for two HAB toxins; brevetoxin and domoic acid (DA). Over a ten-year study period (2000–2009) we have determined that bottlenose dolphins are exposed to brevetoxin and/or DA on a nearly annual basis (i.e., DA: 2004, 2005, 2006, 2008, 2009; brevetoxin: 2000, 2004, 2005, 2008, 2009) with 36% of all animals testing positive for brevetoxin (n = 118) and 53% positive for DA (n = 83) with several individuals (14%) testing positive for both neurotoxins in at least one tissue/fluid. To date there have been no previously published reports of DA in southwestern Florida marine mammals, however the May 2008 health assessment coincided with a Pseudo-nitzschia pseudodelicatissima bloom that was the likely source of DA observed in seawater and live dolphin samples. Concurrently, both DA and brevetoxin were observed in common prey fish. Although no Pseudo-nitzschia bloom was identified the following year, DA was identified in seawater, fish, sediment, snails, and dolphins. DA concentrations in feces were positively correlated with hematologic parameters including an increase in total white blood cell (p = 0.001) and eosinophil (p<0.001) counts. Our findings demonstrate that dolphins within Sarasota Bay are commonly exposed to two algal toxins, and provide the impetus to further explore the potential long-term impacts on bottlenose dolphin health

What is an Insurrection? Destituent Power and Ontological Anarchy in Agamben and Stirner

The aim of this article is to develop a theoretical understanding of the insurrection as a central concept in radical politics in order to account for contemporary movements and forms of mobilisation that seek to withdraw from governing institutions and affirm autonomous practices and forms of life. I will develop a theory of insurrection by investigating the parallel thinking of Giorgio Agamben and Max Stirner. Starting with Stirner’s central distinction between revolution and insurrection, and linking this with Agamben’s theory of destituent power, I show how both thinkers develop an ontologically anarchic approach to ethics, subjectivity and life that is designed to destitute and profane governing institutions and established categories of politics. However, I will argue that Stirner’s ‘egoistic’ and voluntarist approach to insurrection provides a more tangible and positive way of thinking about political action and agency than Agamben’s at times vague, albeit suggestive, notion of inoperativity

Disjecta Membra: Ponovni premislek Althusserjeve estetike

This essay takes a synthetic and critical approach to the scattered pieces of art criticism and aesthetic theory authored by Louis Althusser. Connecting these texts to his larger philosophical and political project, we argue that these reflections make an independent contribution to its worth and that they offer different perspectives on lingering theoretical problems. We piece together the insights that form the core of the Althusserian approach to aesthetics and show how these are formulated (in connection with the work of Pierre Macherey as well as the dominant controversies of the time) and trace how their formulations take shape in relation to the work of different authors and artists. In addition to helping us better understand his overall project, Althusser’s aesthetic theory is, we argue, a powerful and original contribution to Marxist aesthetics. Specifically, it points us to the idea that we need to take aesthetic production seriously as a practice with its own specificity – one that has its own logics of determination, rituals of production, circulation, and consumption, one that commands effects that need to be theorized on their own terms.Pričujoči članek ima sintetičen in kritičen pristop do razpršenih fragmentov umetnostne kritike in estetske teorije v delih Louisa Althusserja. S tem ko te tekste umestiva v Althusserjev širši filozofski in politični projekt, trdiva, da predstavljajo te refleksije neodvisni prispevek k njegovem pomenu in da ponujajo drugačne perspektive na persistentne teoretične probleme. Skupaj poveževa uvide, ki tvorijo jedro althusserjanskega pristopa k estetiki, pokaževa, kako so ti formulirani (v navezavi na delo Pierra Machereya in na prevladujoče kontroverze tistega časa) ter oriševa, kako se njihove formulacije oblikujejo v razmerju do del različnih avtorjev in umetnikov. Poleg tega, da nam pomaga razumeti njegov celotni projekt, trdiva, da predstavlja Althusserjeva estetska teorija pomemben in izviren prispevek k marksistični estetiki. Natančneje, usmeri nas k misli, da moramo estetsko proizvodnjo jemati resno kot prakso z lastno specifičnostjo – takšno, ki ima svoje logike določenosti, ritualov proizvodnje, cirkulacije in potrošnje, takšno, ki določa učinke, ki potrebujejo svojo lastno teoretizacijo