Collaborative Reseach: Nitrogen Limitation and Ultraviolet Stress in Marine Macroalgae

Physical factors such as light, temperature and nutrient availability are known to limit marine productivity and play an important role in determining species distribution and community structure. Most understanding of the role of physical factors is based on studies with a single variable with other conditions being optimized for growth. Consequently, little information is available on physiological responses to the natural environment where several physical factors may be suboptimal. The ability to understand the constraints on marine productivity requires not only an understanding of potential synergistic or antagonistic interactions but also an analysis of their effects on algae with different ecological strategies. This investigation will examine the response of marine red macroalgae to simultaneous nitrogen limitation and ultraviolet radiation stress. Both factors are known to be important determinants of marine primary productivity and they frequently co-occur. This is true not only of the tropics, but also in cold- temperate oceans such as the Gulf of Maine. Red macroalgae were selected for this research because they provide the opportunity to study interactions between UV and nitrogen limitation in a group of algae with similar physiological and morphological characteristics but with well-defined differences in UV-tolerance and well-characterized contents of mycosporine-like amino acids. Furthermore, in contrast to phytoplankton, benthic macroalgae experience a more predictable light climate and are relatively long-lived, exposing individuals to a wider range of environmental conditions. The red algae studied from the Gulf of Maine will include Porphyra umbilicalis, Chondrus crispus, Membranoptera alata and Phycodry rubens. These species range from UV-tolerant intertidal and shallow sublittoral species to UV-susceptible species from the deeper sublittoral. The investigators anticipate that the costs and benefits of UV-tolerance and the impact of nitrogen limitation will vary between UV-tolerant and UV-susceptible species. The research will focus on the effect of nitrogen metabolism (limited or replete) on (a) short and long-term effects of UV-stress (e.g., short-tem inhibition of photosynthesis, lipid peroxidation, and growth), (b) UV-photoprotection including contents of sunscreens such as mycosporine-like amino acids (MAAs), antioxidants such as ascorbate, gluathione and tocopherols, and enzymes of reactive oxygen metabolism such as catalase, superoxide dismutase and ascorbate peroxidase, and (c) ability to recover from UV-stress (e.g., the role of protein synthesis in recovery). The research will also examine the effect of UV-stress on nitrogen metabolism (e.g., nitrogen content and rates of uptake and assimilation). The research will involve measurements on field-collected material, laboratory experiments under controlled conditions and outdoor experiments in flowing seawater and natural radiation manipulated by a variety of UV and photosynthetically active radiation (PAR)-filters. The research will substantially contribute to an understanding of the effect of UV and inorganic nitrogen availability on marine productivity and, in particular, elucidate the importance of interactions between these factors. The research involves collaboration between faculty at an undergraduate teaching institution (Westfield State College, MA) and a Land and Sea Grant research University (University of Maine). In addition to graduate education, the project has a substantial research experience for undergraduate component, providing undergraduates from Westfield State College with the opportunity to become involved in research

RAPID: A Unique Cruise Opportunity to Test the Effect of Trace Metal Limitation on Oxidative Stress and Coral Bleaching

Intellectual Merit. Coral bleaching has increased dramatically in frequency, severity, and geographic extent since the 1980\u27s and this trend is anticipated to continue, causing major environmental and economic impacts in tropical regions. This bleaching, or loss by corals of their photosynthetic endosymbiotic dinoflagellates (zooxanthellae; Symbiodinium spp.), appears to result from increased oxidative stress arising from the combined effects of elevated temperature at high light intensities. However, the mechanisms underlying this failure are not understood. The premise of the PIs\u27 current project entitled Effects of Trace Metal Limitation on Oxidative Stress in Zooxanthellae and Its Role in Coral Bleaching (OCE - 0648478) is that the necessary up-regulation of zooxanthellae antioxidant defenses is restricted by low concentrations of dissolved Fe, Zn and Cu; metals essential for antioxidant enzyme function (Cu, Zn-, Mn-, and Fe-SOD; catalase [Fe]; ascorbate peroxidase [Fe]). Findings from their laboratory and field manipulation experiments show that restricting Fe, and Cu/Zn availability to coral hosts under high (but not low) temperature and light intensity indeed can significantly decrease both photosynthetic efficiency of symbionts in-hospite and ROS enzyme activities, while increasing non-photosynthetic quenching of their photosystems; each indicators of the onset of bleaching conditions. However, although there is high integrity within each experiment, they have found this pattern is not consistent with all coral colonies. Based on limited sampling, it appears that corals collected from the outer shelf region normally (but not always) display indications of oxidative stress under conditions of decreased metal availability, while those collected nearshore, or maintained in coastally-derived flowing seawater (where dissolved metal concentrations are higher), often show little discernable effect. Excess metal uptake and storage is well described in the marine phytoplankton literature, which suggests that the history of the coral metal exposure is a critical factor, both with respect to our experiments as well as to the distribution of coral bleaching observed. The PIs have an unique and unforeseen opportunity to test this hypothesis by joining an Australian Institute for Marine Sciences research cruise to Flinders Reef; an offshore atoll in the Coral Sea that is substantially more distant from sporadic terrestrial metal inputs that our previous study sites. They will participate in this cruise to run on-deck incubations testing the effect of reduced and marginally elevated Fe, Cu, Zn and Mn concentrations on coral photosynthetic efficiency, ROS enzyme activities, symbiont pigment composition, and ROS enzyme and other gene expression. This geographical site will provide the ideal test site for verifying their findings of metal effects on oxidative stress in zooxanthellae, and identify some of the key mechanisms and nutritional factors contributing to the increasingly frequent and severe coral bleaching events in tropical waters.Broader Impacts: This project will provide a unique research opportunity for two graduate students and a junior female Ph.D. scientist, who will use aspects of the work for their thesis and career development. The research addresses the fundamental unknowns of the controls of coral bleaching, one of the leading threats to marine biodiversity and economic stability of tropical nations. The findings will provide a key test of laboratory- and field-developed hypotheses of the role of trace metal limitation as a contributor to oxidative stress of zooxanthellae and their coral hosts; a precursor to coral bleaching. A modular series of lectures and demonstrations targeting both upper K-12 and undergraduates will be developed and will be incorporated into existing outreach programs and undergraduate courses in Marine Science at the University of Maine. The phototrophic symbiosis between zooxanthellae and corals, and its disruption by physical environmental factors, provides an inherently powerful case study for the integration of chemistry, physics, and biology that will illustrate to marine science undergraduates the need for rigorous training in the quantitative physical sciences. The findings will provide key insights to the factors that influence the severity of bleaching events, and possibly suggest realistic mitigation strategies to minimize bleaching events in localized environmentally or economically sensitive regions

Effects of Trace Metal Limitation on Oxidative Stress in Zooxanthellae and Its Role in Coral Bleaching

Coral bleaching has increased dramatically in frequency, severity, and geographic extent since the 1980s and this trend is anticipated to continue, causing major environmental and economic impacts in tropical regions. This bleaching - the loss by corals of their photosynthetic endosymbiotic dinoflagellates (zooxanthellae; Symbiodinium spp.) - involves increased oxidative stress arising from the combined effects of elevated temperature at high light intensities. Although the production of reactive oxygen species (ROS) in corals and phytoplankton is routine during daylight hours, the failure of antioxidant defenses in zooxanthellae becomes catastrophic under comparatively small changes in environmental temperature, because reef corals live close to their upper thermal limits. The mechanisms underlying this failure are not understood, but fall into two categories: (1) the temperature/irradiance conditions lie beyond the capacity for thermal acclimatization by corals and their endo-symbionts, or (2) the necessary enhancement of antioxidant defenses in zooxanthellae is hindered by nutrient deficiencies. In this project, the working hypothesis is that low ambient concentrations of dissolved iron, zinc, copper and perhaps manganese (Fe, Zn, Cu, and Mn) in oligotrophic tropical surface waters, combined with regulation of metal supply to zooxanthellae by the coral host, restrict the compensatory elevation of metal-dependent antioxidant enzymes with rising ROS production, and this resource limitation contributes to coral bleaching. This hypothesis will be investigated in three stages: with pure clonal cultures of zooxanthella isolates; in coral colony culture experiments; and in samples on areas of the Great Barrier Reef, Australia, observed to be susceptible or resistant to coral bleaching. The primary goals of the pure culture experiments are to 1) identify which of the known metals involved in antioxidant enzymes (Fe, Cu, Zn, Mn) are important in zooxanthellae, 2) determine the thresholds of metal nutrition (both in supply and intracellular metal quotas) below which onset of uncontrolled oxidative stress occurs in the zooxanthellae, and 3) ascertain whether these relationships differ significantly among bleaching sensitive and insensitive Symbiodinium species. In addition to verifying the findings in coral/algal symbioses, coral experiments will be used to determine whether the timing and magnitude of bleaching indicators change with metal nutrition, and whether bleaching-sensitive corals can become more resistant by increasing their metal quotas. The linkage between trace metals and antioxidant enzymes is well established in other biological systems but has not been examined in coral/zooxanthellar associations. The proposed work brings together experts in trace metal/ phytoplankton interactions, phytoplankton photo-physiology and oxidative stress, photo-oxidative defenses in reef corals, and molecular biology of marine symbioses to provide mechanistic understanding of coral bleaching, increasing predictive insights to the global trend of coral bleaching. This project will support the education and research training of two Ph.D. students who would test hypotheses integral to the work as parts of their dissertations. Two postdoctoral scientists will participate in the planning, management, and research of the project, providing opportunities to refine their professional development and their mentoring skills necessary for career success. Public lectures on corals and global climate change are planned. The findings will provide insights to the factors influencing the severity of bleaching events, and may suggest realistic mitigation strategies to minimize bleaching in localized environmentally or economically sensitive regions

Global genome analysis of the shikimic acid pathway reveals greater gene loss in host-associated than in free-living bacteria

<p>Abstract</p> <p>Background</p> <p>A central tenet in biochemistry for over 50 years has held that microorganisms, plants and, more recently, certain apicomplexan parasites synthesize essential aromatic compounds via elaboration of a complete shikimic acid pathway, whereas metazoans lacking this pathway require a dietary source of these compounds. The large number of sequenced bacterial and archaean genomes now available for comparative genomic analyses allows the fundamentals of this contention to be tested in prokaryotes. Using Hidden Markov Model profiles (HMM profiles) to identify all known enzymes of the pathway, we report the presence of genes encoding shikimate pathway enzymes in the hypothetical proteomes constructed from the genomes of 488 sequenced prokaryotes.</p> <p>Results</p> <p>Amongst free-living prokaryotes most Bacteria possess, as expected, genes encoding a complete shikimic acid pathway, whereas of the culturable Archaea, only one was found to have a complete complement of recognisable enzymes in its predicted proteome. It may be that in the Archaea, the primary amino-acid sequences of enzymes of the pathway are highly divergent and so are not detected by HMM profiles. Alternatively, structurally unrelated (non-orthologous) proteins might be performing the same biochemical functions as those encoding recognized genes of the shikimate pathway. Most surprisingly, 30% of host-associated (mutualistic, commensal and pathogenic) bacteria likewise do not possess a complete shikimic acid pathway. Many of these microbes show some degree of genome reduction, suggesting that these host-associated bacteria might sequester essential aromatic compounds from a parasitised host, as a 'shared metabolic adaptation' in mutualistic symbiosis, or obtain them from other consorts having the complete biosynthetic pathway. The HMM results gave 84% agreement when compared against data in the highly curated BioCyc reference database of genomes and metabolic pathways.</p> <p>Conclusions</p> <p>These results challenge the conventional belief that the shikimic acid pathway is universal and essential in prokaryotes. The possibilities that non-orthologous enzymes catalyse reactions in this pathway (especially in the Archaea), or that there exist specific uptake mechanisms for the acquisition of shikimate intermediates or essential pathway products, warrant further examination to better understand the precise metabolic attributes of host-beneficial and pathogenic bacteria.</p

Where Corals Lie: A Natural and Cultural History

For millennia, corals were a marine enigma, organisms that confounded scientific classification and occupied a space between the animal and plant kingdoms. Our cultural relationships with coral have been similarly ambiguous. The danger posed by unseen underwater reefs led to an association of coral with death and interment that has figured in literature, poetry, music, and film, while the bright redness of precious Mediterranean coral was associated in European and Indian mythology with its origins in blood and gore. And yet, coral skeletons have long been prized as jewelry and ornament, featuring prominently in Renaissance cabinets of curiosities. Opening the door onto these most peculiar of animals, this unique book treats the many manifestations of coral across biology, geology, and culture. Today, the tide of danger flows in reverse. Seen as rainforests of the sea, coral reefs have become emblematic of the fragility of marine biodiversity, their declining health a warning sign of the human-driven climate change that has produced warming seas, ocean acidification, and rising sea levels. Looking at corals as builders of islands and protectors of coastlines, as building materials themselves, as well as at the myriad ways in which diverse corals have come to figure in art, medicine, folklore, geopolitics, and international trade, Where Corals Lie reveals how the threatening has become threatened—and of the danger this poses to humans. Exceptionally embellished with a wide range of biological illustrations, underwater photography, and fine art, Where Corals Lie is a beautiful and informative resource for anyone interested in ocean environments and the cultures that flourish or fail there.https://digitalcommons.library.umaine.edu/fac_monographs/1300/thumbnail.jp

PHOTOBIOLOGY OF THE SYMBIOTIC SEA ANEMONE, ANTHOPLEURA ELEGANTISSIMA: DEFENSES AGAINST PHOTODYNAMIC EFFECTS, AND SEASONAL PHOTOACCLIMATIZATION

Volume: 167Start Page: 683End Page: 69

ASEXUAL REPRODUCTION AND GENETIC POPULATION STRUCTURE IN THE COLONIZING SEA ANEMONE HALIPLANELLA LUCIAE

Volume: 153Start Page: 604End Page: 61