Laws Edward A.

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Edward A.

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Now showing 1 - 5 of 5
  • Article
    Ocean acidification as one of multiple stressors : growth response of Thalassiosira weissflogii (diatom) under temperature and light stress
    (Inter-Research, 2015-12-15) Passow, Uta ; Laws, Edward A.
    Future shifts in phytoplankton composition and productivity are anticipated given that continuing changes are expected in environmental conditions such as temperature, the partial pressure of CO2 (pCO2) and light climate, all of which regulate phytoplankton communities and their physiology through bottom-up control. Culture experiments revealed that future (elevated) pCO2 had no effect on Thalassiosira weissflogii in the absence of environmental stressors, whereas growth rates drastically decreased under future pCO2 when cells were grown under light and temperature stress. Reduction in growth rates and a smaller decline in cellular photosynthesis under high pCO2 were associated with 2- to 3-fold increases in the production of transparent exopolymer particles (TEP) and in the cell quotas of organic carbon, as well as a similar decrease in the C:chl a ratios. Results suggest that under light- and temperature-stressed growth, elevated pCO2 led to increased energy requirements, which were fulfilled by increased light harvesting capabilities that permitted photosynthesis of acclimatized cells to remain relatively high. This was combined with the inability of these cells to acclimatize their growth rate to sub-optimal temperatures. Consequently, growth rate was low and decoupled from photosynthesis, and this decoupling led to large cell sizes and high excretion rates in future pCO2 treatments compared to ambient treatments when growth temperature and light were sub- optimal. Under optimal growth conditions, the increased energy demands required to re- equilibrate the disturbed acid-base balance in future pCO2 treatments were likely mediated by a variety of physiological acclimatization mechanisms, individually too small to show a statistically detectable response in terms of growth rate, photosynthesis, pigment concentration, or excretion.
  • Article
    Centers for Oceans and Human Health : contributions to an emerging discipline
    (BioMed Central, 2008-11-07) Laws, Edward A. ; Fleming, Lora E. ; Stegeman, John J.
    The oceans are the dominant feature of the planet and are fundamentally linked to human history and to human health. Concerns about the impact of the oceans on human health can be traced to ancient times. Jewish law prohibited the consumption of shellfish, probably reflecting the fact that filter-feeding bivalves can accumulate pathogens and toxins. The Portuguese explorer Pedro Fernandes de Queirós described symptoms associated with ciguatera fish poisoning after eating Caribbean sea bream in 1606, and several of British explorer James Cook's crew experienced similar symptoms after eating fish off the coast of Vanuatu in 1774 [1]. Roughly 1,200 people died from the consumption of fish and shellfish contaminated with methyl mercury in Minamata (Japan) during the 20th century; an even larger number were affected by chronic long-term neurotoxicological impacts [2]. A tsunami caused by an undersea earthquake on December 26, 2004 killed more than 225,000 people in eleven countries bordering the Indian Ocean; and more than 1,400 people died within a single day when the storm surge generated by Hurricane Katrina overwhelmed the New Orleans levee system on August 29, 2005 [3]. Looking ahead, the International Panel on Climate Change has projected a sea level rise of as much as 88 cm during the 21st century as a result of global warming [4], with major implications for the welfare and sustainability of coastal communities.
  • Article
    Environmental controls, oceanography and population dynamics of pathogens and harmful algal blooms: connecting sources to human exposure
    (BioMed Central, 2008-11-07) Dyble, Julianne ; Bienfang, Paul ; Dusek, Eva ; Hitchcock, Gary ; Holland, A. Fredrick ; Laws, Edward A. ; Lerczak, James A. ; McGillicuddy, Dennis J. ; Minnett, Peter ; Moore, Stephanie K. ; O'Kelly, Charles ; Solo-Gabriele, Helena M. ; Wang, John D.
    Coupled physical-biological models are capable of linking the complex interactions between environmental factors and physical hydrodynamics to simulate the growth, toxicity and transport of infectious pathogens and harmful algal blooms (HABs). Such simulations can be used to assess and predict the impact of pathogens and HABs on human health. Given the widespread and increasing reliance of coastal communities on aquatic systems for drinking water, seafood and recreation, such predictions are critical for making informed resource management decisions. Here we identify three challenges to making this connection between pathogens/HABs and human health: predicting concentrations and toxicity; identifying the spatial and temporal scales of population and ecosystem interactions; and applying the understanding of population dynamics of pathogens/HABs to management strategies. We elaborate on the need to meet each of these challenges, describe how modeling approaches can be used and discuss strategies for moving forward in addressing these challenges.
  • Preprint
    Impacts of Hurricanes Katrina and Rita on the microbial landscape of the New Orleans area
    ( 2007-03-20) Sinigalliano, Christopher D. ; Gidley, M. L. ; Shibata, T. ; Whitman, D. ; Dixon, T. H. ; Laws, Edward A. ; Hou, A. ; Bachoon, D. ; Brand, Larry E. ; Amaral-Zettler, Linda A. ; Gast, Rebecca J. ; Steward, Grieg F. ; Nigro, Olivia D. ; Fujioka, Roger S. ; Betancourt, W. Q. ; Vithanage, G. ; Mathews, J. ; Fleming, Lora E. ; Solo-Gabriele, Helena M.
    Floodwaters in New Orleans from Hurricanes Katrina and Rita were observed to contain high levels of fecal indicator bacteria and microbial pathogens, generating concern about long-term impacts of these floodwaters on the sediment and water quality of the New Orleans area and Lake Pontchartrain. We show here that fecal indicator microbe concentrations in offshore waters from Lake Pontchartrain returned to prehurricane concentrations within 2 months of the flooding induced by these hurricanes. Vibrio and Legionella species within the lake were more abundant in samples collected shortly after the floodwaters had receded compared with samples taken within the subsequent 3 months; no evidence of a long-term hurricane-induced algal bloom was observed. Giardia and Cryptosporidium were detected in canal waters. Elevated levels of fecal indicator bacteria observed in sediment could not be solely attributed to impacts from floodwaters, as both flooded and nonflooded areas exhibited elevated levels of fecal indicator bacteria. Evidence from measurements of Bifidobacterium and bacterial diversity analysis suggest that the fecal indicator bacteria observed in the sediment were from human fecal sources. Epidemiologic studies are highly recommended to evaluate the human health effects of the sediments deposited by the floodwaters.
  • Dataset
    Series 5: pCO2 as one of multiple stressors for Thalassiosira weissflogii
    (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact:, 2015-12-14) Passow, Uta ; Laws, Edward A.
    The increase in partial pressure of CO2 (pCO2) is causing ocean acidification, which impacts the growth rates and elemental composition of phytoplankton. Here, shifts in growth rates and cell quotas of Thalassiosira weissflogii grown under a variety of different temperatures, irradiances, and pCO2 conditions are discussed. The presented data suggest that acclimatization times of exponentially growing diatoms to environmental perturbations may be weeks to months, rather than days to weeks. The response of acclimatized T. weissflogii to pCO2 depended on irradiance and temperature and was highly interactive, non-linear, and non-uniform. A very significant negative effect of pCO2 was observed under growth conditions that were light-, and temperature-limited; a smaller, but still significant negative response was seen under light-limiting growth conditions, whereas pCO2 did not affect growth rates of T. weissflogii under light-saturated growth conditions. Cell quotas of organic carbon, nitrogen, or chlorophyll a were linked to growth rate. The cell-normalized production of transparent exopolymer particles (TEP) was positively correlated with POC cell quotas, with some minor impact of irradiance and pCO2 on the relationship. This correlation of TEP production with carbon cell quotas is consistent with the hypothesis that extracellular release is an inherent component of cell etabolism. Results suggest that elevated pCO2 functions as an (additional) metabolic stressor for T. weissflogii and that the interaction of different stressors determines growth rates and cell characteristics in a complex, non-linear relationship.