louisiana state university - ocean sciences 2016 monday, february 22… · 2016. 2. 19. · the...

OCEAN SCIENCES 2016

Monday, February 22, 2016 TIME: 8:45 AM - 09:00 AM LOCATION: RO3

#LSURESEARCHFor more information, call the LSU Division of Strategic Communications at 225-578-8654.

RESEARCH WORKS

Animal dispersal behaviors have both ecological and evolutionary significance. However, due to the logistical challenges of tracking animals in the Antarctic marine environment little is known about the winter dispersal and migration of Antarctic marine predators. We used a combination of direct tracking (Geolocation sensors; GLS) and compound-specific stable isotope analysis of carbon in essential amino acids (CSIA-AA) to describe the winter distribution of two wide-ranging marine predators, the Adélie penguin (Pygoscelis adeliae) and chinstrap penguin (P. antarctica) along the Antarctic Peninsula and Scotia Arc. GLS and CSIA-AA identified two general migration strategies, with animals overwintering to the east or west of the Antarctic Peninsula, with CSIA-AA also being able to discriminate

between ice-free vs. pack-ice habitats. In addition, CSIA-AA provided the ability to assign non GLS-tracked chinstrap penguins from multiple breeding sites across the Scotia Arc to specific over-wintering areas. This provided a first ever, regional-scale analyses of the winter movements and distributions of the species and identified a cryptic latitudinal trend that would have been otherwise undetectable. Breeding colonies farther north were more likely to have individuals dispersing eastwards relative to colonies further south where most individual dispersed westwards, possibly due to a combination of proximity and competition avoidance. Finally we highlight how CSIA-AA approaches can be applied to other studies of the distribution and ecology of marine top predators.

MICHAEL POLITOLSU DEPARTMENT OF OCEANOGRAPHY & COASTAL SCIENCES

Direct Tracking and Compound-Specific Stable Isotope Analysis Identifies Dispersal Routes and Cryptic Latitudinal Trends in the Winter Distribution of Two Antarctic Penguin Species

OCEAN SCIENCES 2016

Monday, February 22, 2016 TIME: 12:00 PM - 12:15 PM LOCATION: 220-221


RESEARCH WORKS

In the past decade, interest in wave attenuation by vegetation has increased considerably as coastal scientists and engineers search for sustainable solutions to mitigate the impacts of climate change and natural hazards. It is well known that vegetation in wetlands can effectively reduce the flow speed, modify turbulence structure, attenuate wave energy, and affect sediment dynamics. Restoring coastal wetlands and reducing flood risks require improved understanding and better predictive capability of wave and surge attenuation over inundated coastal landscapes with vegetation. The interactions of surface waves and natural vegetation span over a large range of scales, from turbulence and eddies at the vegetation stem scale to wave generation in vast inundated wetlands of hundreds of square miles under

hurricane conditions. The study is focused on a phase-averaged energy-based model and phase-resolving Euler and Navier-Stokes (N-S) solvers with different representations of submerged vegetation. We will present recent advances in multi-scale modeling of wave attenuation by wetland vegetation. Numerical modeling results ranging from vegetation-resolved large eddy simulation under idealized conditions to incorporating vegetation-induced drag forces into conservation laws of momentum and energy for engineering applications will be shown. Effects of vegetation flexibility, turbulence closure, and various wave theories on the prediction of wave attenuation and the choice of vegetation drag coefficients will be discussed.

QIN JIM CHENLSU DEPARTMENT OF CIVIL & ENVIRONMENTAL ENGINEERING

Multi-Scale Modeling of Wave Attenuation by Vegetation

OCEAN SCIENCES 2016

Wednesday, February 24, 2016TIME: 8:00 AM - 8:15 AM LOCATION: 222


RESEARCH WORKS

Deltas and estuaries are productive and fertile links between the land and the sea. Deltas occupy only about 5% of the Earth’s surface but sustain over a half billion people all around the world. Many river deltas are endangered because of extensive dam and levee construction, declining sediment supply, groundwater withdrawal, relative sea level rise and severe coastal erosion, leading to a variety of threats to natural, economic and social systems. About 630 million people now live at an elevation of 10 m or less above mean sea level, and maintaining sustainable land with a rising sea will be a challenging problem for many major deltaic coasts and cities in the next century. Stemming from 20 years of LOICZ (Land-Ocean Interactions in the Coastal Zone), Future Earth Coasts is a new global initiative that seeks to enable

the scientific and social scientific communities to build knowledge through collaborative processes to better understand and address the profound and urgent changes occurring in vulnerable coastal zones. The topics of this comparative study are the Mississippi and Yangtze (Changjiang) Rivers, the largest in the United States and China, respectively. We use these two rivers as examples to evaluate current conditions and catalyze future discussion. The Mississippi and Yangtze both have had long-term observations of physical and biological processes that affect human activities, making it possible to quantify both natural and anthropogenic impacts. We also consider the limits to the concept of sustainability for the Earth’s biosphere and human civilization, and emphasize biophysical constraints and demographic challenges.

CHRIS D’ELIALSU COLLEGE OF THE COAST & ENVIRONMENT

Future Earth Coasts: The Mississippi and Yangtze Rivers as Examples

OCEAN SCIENCES 2016

Wednesday, February 24, 2016 TIME: 9:30 AM - 9:45 AM LOCATION: 222


RESEARCH WORKS

The shelf offshore Louisiana is characterized by a dominantly muddy seafloor with a paucity of restoration-quality sand proximal to shore. Discrete sand deposits associated with ancient rivers that incised the shelf during lower sea-level positions occur close to shore. These shelf channel sands have been targeted for coastal restoration projects resulting in significant cost savings over more distal deposits. Several recent projects targeted shelf paleo-fluvial deposits comprising relatively deep (10 m) channel sands underlying a muddy overburden. Because of contrasting characteristics of cohesive mud vs. non-cohesive sand and potential modern fluvial mud supply from the Mississippi and Atchafalaya Rivers, long term pit evolution is poorly understood relative to their more common sand-only counterparts. Alterations to seafloor topography from dredging shelf sediment resources can potentially affect oil and gas infrastructure or other resources of concern (i.e. historic

shipwrecks) located proximal to dredge pits. Site-specific data required to make accurate predictions and empirical measurements to test and validate predictive models were only available for Peveto Channel offshore Holly Beach, Louisiana. Here we present new geophysical and geological data (bathymetry, sidescan, subbottom, and radionuclide of sediment cores) and physical oceanographic observations (hydrodynamics and sediment dynamics) collected at Raccoon Island (dredged in 2013) dredge pit in Louisiana. These field data collections along with pre-existing data provide a time-series to capture evolution at Raccoon Island post-excavation. Conceptual morphological models will be developed for dredge pit evolution and testing effectiveness of setback buffers protecting pipelines, habitats, and cultural resources. Our results will increase decision making ability regarding safety and protecting environmental and cultural resources, and better management of valuable sand resources.

KEHUI XULSU DEPARTMENT OF OCEANOGRAPHY & COASTAL SCIENCES

Assessment of Mud-Capped Dredge Pit Evolution Offshore Louisiana: Implications to Sand Excavation and Coastal Restoration

OCEAN SCIENCES 2016

Wednesday, February 24, 2016TIME: 9:45 AM – 10:00 AM LOCATION: 222


RESEARCH WORKS

Many fluvial channels incised the Northern Gulf of Mexico inner continental shelf during the late Quaternary. Mud-capped dredge pits (MCDPs), which are generally elongate and deep (8-10 m) excavations, target sandy fluvial channel deposits for coastal restoration projects. The morphological evolution of dredge excavations in noncohesive sandy substrate is well studied, but MCDPs have up to a several-meter-thick veneer of Holocene shelf mud overlying sandy channel deposits. This stratigraphy is hypothesized to result in more complex post-dredge morphology than pit walls simply slumping to the angle of repose shortly after excavation. Numerical modeling of MCDP post-dredge response conducted prior to excavation indicates pit walls may retrogressively fail, which is accounted for in pit design by assigning no-dredge setback buffers from pipelines or cultural and environmental resources. To validate model results and test effectiveness of setback buffers, a geophysical survey of the Sandy Point MCDP (20 km west of the Mississippi River Delta in 10m deep water), where 1.7 million m3 of sandy sediment was excavated in 2012, was conducted May 2015. A total of 84 line-km of high-

resolution chirp subbottom and a 27 km2 grid of swath bathymetry and sidescan sonar were collected.

The data indicate the dredge pit walls are differentially slumping, with the western pit wall in a more active state of failure than the eastern wall. The western failures morphologically resemble features observed along the muddy Mississippi River Delta Front at water depths of 20-100 m, including bowl-shaped collapse failures and retrogressive stair-stepped slumps; these failures may play a key role in evaluating the distance of setback buffer zone to pipelines. These features indicate the cohesive mud overlying the sandy infill has a prominent role in pit wall stability. A 0.5-1 m thick acoustically transparent package overlies the entire pit floor (interpreted as a possible fluid mud layer), overlying 1-3 m of post-dredge deposition that is concentrated along the western wall and center of the pit. The Sandy Point MCDP lies within a clockwise gyre, and its relief may serve as a significant trap of suspended sediment. These findings emphasize the role MCDPs play in sediment dynamics as well as their potential for submarine geohazards.

JEFFREY OBELCZLSU COASTAL STUDIES INSTITUTE

Evolution of Mud-capped Dredge Pits Following Excavation: Sediment Trapping and Slope Instability

OCEAN SCIENCES 2016

Wednesday, February 24, 2016TIME: 2:30 PM – 2:45 PM LOCATION: 231-232


RESEARCH WORKS

Sediment-water interface represents an important exchange surface that regulates the cycling and transfer of many elements and nutrients between sediments and overlying water. Traditionally, rate of transfer across the sediment–water interface is determined by deploying benthic chambers or modeling the depth profiles of a dissolved species of interest in the sediment. In this study we utilize224Ra: 228Th disequilibrium in the sediment to determine solute transport rates in coastal Louisiana sediments. In marine sediments, 224Ra (half-life = 3.66 d) is continuously produced by alpha decay of its parent nuclide, 228Th (half-life = 1.91 y). While 228Th is strongly bound to sediments, 224Ra tends to remain in dissolved phase in the interstitial water, and migrate across the

sediment–water interface into the overlying water. This results in a deficit of 224Ra with respect to 228Th in near-surface sediments that can be utilized to calculate solute transport rates. Depth profiles of dissolved and surface-bound 224Ra and 228Th in the upper 10 cm sediment column indicate significant deficit of 224Ra relative to 228Th. By modeling the 224Ra depth profiles in the sediment using the general diagenetic equation along with 234Th bioturbation rates we demonstrated that molecular diffusion and bioturbation together accounts for less than 50% of the measured fluxes of 224Ra in this region. The solute transport derived from this method are also utilized to understand transport/consumption of other species like O2 and Fe

2+ in these sediments.

WOKIL BAMLSU DEPARTMENT OF OCEANOGRAPHY & COASTAL SCIENCES

224Ra: 228Th Disequilibrium in Sediments as a Tracer for Solute Transfer across the Sediment-Water Interface in Coastal Louisiana

OCEAN SCIENCES 2016

Thursday, February 25, 2016TIME: 9:00 AM – 9:15 AM LOCATION: 206


RESEARCH WORKS

Gulf hypoxia has received considerable scientific and policy attention because of its large size (up to 22,000 square km), potential ecological and economic effects, and the need to understand the implications of various nutrient management strategies in the large Mississippi River watershed. Over the past 20 years, a number of different models have been developed to simulate the severity and areal extent of hypoxia in the northern Gulf of Mexico, and to predict the consequences of management actions. The models range from simple statistical models to complex three-dimensional fully coupled hydrodynamic-biogeochemical models. The

size and the complexity of these models have been steadily increasing due to developments in computer technology and computational techniques, and also in response to new scientific paradigms that have emerged over time forcing modelers to broaden the scope of their original models. We present an overview of hypoxia models developed for the Gulf of Mexico hypoxic zone and discuss the lessons learned, and some fundamental differences between simple and complex models in evaluating the effectiveness of nutrient management strategies for reducing hypoxia.

DUBRAVKO JUSTICLSU DEPARTMENT OF OCEANOGRAPHY & COASTAL SCIENCES

Reducing Hypoxia in the Northern Gulf of Mexico: Lessons from Simple and Complex Models

OCEAN SCIENCES 2016



RESEARCH WORKS

Coastal wetlands in southern Louisiana are vanishing rapidly due to a host of environmental stressors including sea level rise, subsidence, and lack of sediment deposition. Since these wetlands provide significant environmental and economic value, their stability and preservation are critical issues for scientists and policyholders. A key question concerns the spatial and temporal variability of wetland accretion rates, particularly the role of hurricanes as an agent in wetland sedimentation. Since 1996, thousands of wetland accretion measurements have been determined at 390 sites across South Louisiana as a result of a regional monitoring network (Coastal Reference Monitoring System, or CRMS), under the collaboration of the Louisiana Office of Coastal Protection and Restoration (CPRA) and the United States Geological Survey (USGS). We utilized this voluminous dataset to analyze the spatial and temporal

patterns of wetland accretion by mapping the rates during three time periods around the landfall of Isaac, a category 1 hurricane, in August 2012. By analyzing sites with sampling dates no more than 7 months from establishment, the results indicate that wetland accretion rates averaged about 2.89 cm/yr from stations sampled before Isaac, 4.04 cm/yr during the period containing Isaac’s impact, and 2.38 cm/yr from sites established and sampled after Isaac. Wetland accretion rates determined from the period containing Isaac’s impact were 40% and 70% greater than rates before and after the hurricane, respectively. Wetland accretion rates associated with Isaac were highest at sites along the Mississippi River and its tributaries instead of along the path of the hurricane, suggesting that freshwater flooding from rivers and streams, rather than storm surge, is the main mechanism responsible for increased wetland accretion.

THOMAS BIANCHETTELSU DEPARTMENT OF OCEANOGRAPHY & COASTAL SCIENCES

Wetland Accretion Rates along Coastal Louisiana: Spatial and Temporal Variability in Light of Hurricane Isaac’s Impacts

OCEAN SCIENCES 2016



RESEARCH WORKS

The modern Mississippi River Delta plain has been largely disconnected from the main distributary by a highly engineered system of levees and floodways. This vast and fragile landscape is experiencing land-loss and is increasingly susceptible to inundation. Intense debate exists in the scientific community as to whether direct fluvial or hurricane-driven re-suspension and sedimentation are the present dominant sources of mineral sediment to the wetland surfaces of the modern delta complex. The relative importance of these sources remains a matter of public discussion and scientific debate, and this lack of clarity strongly influences development of tools, strategies, and policies to conserve coastal Mississippi River Delta lands.

Research fueling this debate has been restricted both spatially and temporally thus far. Furthermore, the contribution of organic production is unknown at these scales. A comprehensive study of the Lafourche and Plaquemine-Balize Mississippi River Delta complexes

at a temporal scale similar to that of natural deltaic cycles (102 - 103years) is being completed to address the deficiencies in our current understanding. A suite of 38 5m vibracores and 33 co-located 1m piston cores are being analyzed at moderate- to high- resolution for bulk density, grain-size, organic matter, magnetic susceptibility, and X-ray fluorescence to create the recognition criteria necessary to distinguish sedimentary sources for this time period.

210Pb and 137Cs data show that despite rapid subsidence and sea-level rise, many studied wetlands are still able to maintain their elevations. Sedimentary accumulation rates in the subaerial components of the Lafourche complex would seem to indicate that following distributary abandonment/cutoff and the elimination of pre-levee and overbank flooding and crevasse sediments, resuspension by cold fronts and hurricanes has become the primary sediment source for affected wetlands.

CRAWFORD WHITELSU DEPARTMENT OF GEOLOGY & GEOPHYSICS

Influences of Hurricanes, Floods, and Organic Production on River-Delta Evolution

OCEAN SCIENCES 2016

Thursday, February 25, 2016TIME: 9:00 AM – 9:15 AM LOCATION: 217-219


RESEARCH WORKS

Arctic storms in the late summer and early fall can produce severe weather conditions for the seasonally unfrozen coastal waters. The alternating wind directions due to the movement of Arctic high pressure systems and atmospheric low pressure frontal systems produce a low frequency subtidal oscillation of water levels, causing flushing and through flows in Arctic lagoons with multiple inlets. From 2013 to 2015, we conducted surveys in late summer and early fall with bottom deployed acoustic Doppler current profilers (ADCP) in a 16-m deep tidal pass of the Elson Lagoon, and ship based surveys in the nearshore Barrow region of Alaska. Atmospheric, CTD, water level, and wave data were also obtained during this period. An atmospheric

Weather Research and Forecasting (WRF) model was run to resolve the evolution of the high pressure movement and wind regime changes. A coastal ocean hydrodynamics model was run to illustrate the dynamical processes as shown by the observations. Our results have shown the sensitivity of the flushing and through flow oscillations in the multi-inlet lagoon to the atmospheric pressure systems, which also can be used to explain the great inter-annual variabilities and impact on ice movement in and out of the lagoons. This variability in hydrodynamic conditions, driven by meteorological phenomenon, is believed to play a significant role in structuring the nearshore ecology of the region.

CHUNYAN LILSU DEPARTMENT OF OCEANOGRAPHY & COASTAL SCIENCES

Summer Time Flushing of an Arctic Multi-inlet Lagoon under Storms from 2013 to 2015

OCEAN SCIENCES 2016



RESEARCH WORKS

Dujiangyan, also known as the Dujiangyan Project, is a hydraulic engineering complex built more than 2,260 years ago on the Mingjiang River near Chengdu in China’s Sichuan Province. The complex splits the river into two channels, a so-called “inner river” (Leijiang) and an “outer river” (Waijiang) that carry variable water volumes and sediment loads under different river flow conditions. The inner river and its numerous distributary canals are primarily man-made for irrigation over the past 2000 years, while the outer river is the natural channel and flows southward before entering into the Yangtze River. Under normal flow, 60% of the Mingjiang River goes into the inner river for irrigating nearly 1 million hectares of agricultural land on the Chengdu plain. During floods, however, less than 40% of the Mingjiang River flows into the inner river. Under both flow conditions, about 80% of the riverine sediments is carried by the outer river and continues downstream. This hydrology is achieved through a weir work complex that comprises three major components: a V-shaped bypass dike in the center of the Mingjiang River, a sediment diversion canal in the inner river

below the bypass dike (the Feishayan Floodgate), and a flow control in the inner river below the sediment diversion canal (the Baopingkou Diversion Passage). Together with ancillary embankments, these structures have not only ensured a regular supply of silt-reduced water to the fertile Chengdu plain, but have provided great benefits in flood control, sediment transport, and water resources regulation over the past 2,000 years. The design of this ancient hydraulic complex ingeniously conforms to the natural environment while incorporating many sophisticated techniques, reflecting the concept that humankind is an integral part of nature. As we are urgently seeking solutions today to save the sinking Mississippi River Delta, examination of the ancient engineering marvel may offer insights into sustainable practices in river engineering of the lower Mississippi under climate change and sea level rise. This paper will introduce the Dujiangyan Project and will discuss possibilities of applying Dujiangyan’s fundamental concept for sediment diversions in the Lower Mississippi River.

YI-JUN XULSU SCHOOL OF RENEWABLE NATURAL RESOURCES

Dujiangyan: Could Ancient Hydraulic Engineering be a Sustainable Solution for Mississippi River Diversions?

OCEAN SCIENCES 2016

Wednesday, February 24, 2016TIME: 3:30 PM - 3:45 PM LOCATION: 231-232


RESEARCH WORKS

Photosynthetic microbial mats produce organic matter, cycle nutrients, bind pollutants, and stabilize sediment in sandy marine environments. Here, we investigate the influence of bedforms and wave motion on the growth rate, composition, and spatial variability of microbial mats by growing cyanobacterial mats on a rippled bed of carbonate sand in a wave tank. The tank was forced with an oscillatory flow with velocities below the threshold for sediment motion yet able to induce a porewater flow within the sediment. Different spatial patterns developed in mats depending on the initial biochemistry of the water medium. When growing in a medium rich in nitrogen, phosphorous, and micronutrients, mats grew faster on ripple troughs than on ripple crests. After two months, mats covered the bed surface uniformly, and the microbial communities on the crests and in the troughs had similar compositions. Differences in bed shear stress and nutrient availability between crests and troughs

were not able to explain the faster growth in the troughs. We hypothesize that this growth pattern is due to a “strainer” effect, i.e. the suspended bacteria from the inoculum were preferentially delivered to troughs by the wave-induced porewater flow. In the experiments initiated in a medium previously used up by a microbial mat and thus depleted in nutrients, mats grew preferentially on the ripple crests. This spatial pattern persisted for nearly two years, and the microbial composition on troughs and crests was different. We attribute this pattern to the upwelling of porewater in the crests, which increased the delivery of nutrients from sediment to the cyanobacteria on the bed surface. Thus, the macroscopic patterns formed by photosynthetic microbial mats on sand ripples may be used to infer whether mats are nutrient-limited and whether they are recently colonized or older than a month.

GIULIO MARIOTTILSU DEPARTMENT OF OCEANOGRAPHY & COASTAL SCIENCES

Spatial Patterns of Cyanobacterial Mat Growth on Sand Ripples

OCEAN SCIENCES 2016

Thursday, February 25, 2016TIME: 3:45 PM – 4:00 PM LOCATION: 206


RESEARCH WORKS

The northwestern Gulf of Mexico (USA) currently experiences a large hypoxic area (“dead zone”) during the summer. The population-level effects of hypoxia on coastal fish are largely unknown. We developed a spatially-explicit, individual-based model to analyze how hypoxia effects on reproduction, growth, and mortality of individual Atlantic croaker could lead to population-level responses. The model follows the hourly growth, mortality, reproduction, and movement of individuals on a 300 x 800 spatial grid of 1 km2 cells for 140 years. Chlorophyll-a concentration and water temperature were specified daily for each grid cell. Dissolved oxygen (DO) was obtained from a 3-D water quality model for four years that differed in their severity of hypoxia. A bioenergetics model was used to represent growth, mortality was assumed stage- and age-dependent, and movement behavior was based on temperature preferences and avoidance of low DO. Hypoxia effects were imposed using exposure-effects sub-models that converted time-varying

exposure to DO to reductions in growth and fecundity, and increases in mortality. Using sequences of mild, intermediate, and severe hypoxia years, the model predicted a 20% decrease in population abundance. Additional simulations were performed under the assumption that river-based nutrient loadings that lead to more hypoxia also lead to higher primary production and more food for croaker. Twenty-five percent and 50% nutrient reduction scenarios were simulated by adjusting the cholorphyll-a concentrations used as food proxy for the croaker. We then incrementally increased the DO concentrations to determine how much hypoxia would need to be reduced to offset the lower food production resulting from reduced nutrients. We discuss the generality of our results, the hidden effects of hypoxia on fish, and our overall strategy of combining laboratory and field studies with modeling to produce robust predictions of population responses to stressors under dynamic and multi-stressor conditions.

KENNETH ROSELSU DEPARTMENT OF OCEANOGRAPHY & COASTAL SCIENCES

Modeling the Population-level Effects of Hypoxia on a Coastal Fish: Implications of a Spatially-explicit Individual-based Model

OCEAN SCIENCES 2016

Friday, February 26, 2016TIME: 8:45 AM – 9:00 AM LOCATION: 225-227


RESEARCH WORKS

Coastal regions of eutrophication-driven oxygen depletion are widespread and increasing in number. Also known as dead zones, these regions take their name from the deleterious effects of hypoxia (dissolved oxygen less than 2 mg/L) on shrimp, demersal fish, and other animal life. Dead zones result from nutrient enrichment of primary production, concomitant consumption by chemoorganotrophic aerobic microorganisms, and strong stratification that prevents ventilation of bottom water. One of the largest dead zones in the world occurs seasonally in the northern Gulf of Mexico (nGOM), where hypoxia can reach up to 22,000 square kilometers. To explore the underlying genomic variation and metabolic potential of microorganisms in hypoxia, we performed metagenomic and metatranscriptomic sequencing on six samples from the 2013 nGOM dead zone from both hypoxic and oxic bottom waters. Over 217 Mb of sequence was assembled into contigs of at

least 3 kb with IDBA-UD, with 72 greater than 100 kb, and the largest 495 kb in length. Annotation by IMG recovered over 224,000 genes in these contigs. Binning with tetra-ESOM and quality filtering based on relative coverage of sample-specific reads led to the recovery of 83 partial to near complete (31 over 70%) high-quality genomes. These metagenomes represent key microbial taxa previously determined to be numerically abundant from 16S rRNA data, such as Thaumarcheaota, Marine Group II Euryarchaeota, SAR406, Synechococcus spp., Actinobacteria, and Planctomycetes. Ongoing work includes the recruitment of metatranscriptomic data to binned contigs for evaluation of relative gene expression, metabolic reconstruction, and comparative genomics with related organisms elsewhere in the global oceans. These data will provide us with detailed information regarding the metabolic potential and activity of many of the key players in the nGOM dead zone.

CAMERON THRASHLSU DEPARTMENT OF BIOLOGICAL SCIENCES

A Metagenomic Assembly-based Approach to Decoding Taxa in the Dead Zone

OCEAN SCIENCES 2016

Friday, February 26, 2016TIME: 8:45 AM – 9:00 AM LOCATION: 211-213


RESEARCH WORKS

Orbicella (formerly Montastraea) faveolata is an Atlantic massive coral species used by paleoclimatologists to reconstruct monthly- and annually-resolved sea surface temperature (SST) variations. Previous studies found discrepancies in coral strontium-to-calcium ratios (Sr/Ca) among colonies separated by meters to kilometers possibly attributed to either biological processes inherent to each colony, environmental differences at each coral site, and/or sampling-analytical methods. Here we examine coral Sr/Ca variations in five O. faveolata colonies offshore from Veracruz, Mexico (19.06ºN, 96.93ºW), two colonies from different water depths (3 and 6 m) in the same local reef environment (Santiaguillo) and three colonies in nearby reefs closer to the mainland (water depth of 4, 6, and 12 m); all colonies were cored in 1993. We control for sampling-analytical methods by using a refined sampling protocol that follows a corallite thecal wall that is parallel to the coral slab surface (i.e., optimal alignment) and we use the same analytical

method and instrument for all colonies. Coral annual growth rates decrease by 44% for colonies in deeper water (12 m) with no significant correlation in annual growth rates among the colonies. Monthly coral Sr/Ca determinations co-vary among colonies up to 16 km apart suggesting a common environmental signal. Means in coral Sr/Ca among the colonies is similar until 1986 when a divergence occurs that does not follow the expected differences due to water depth and growth rate. The two colonies farthest from the mainland (Santiaguillo) have similar means and coral Sr/Ca variations from 1986–1993. In the mid-1980s, Veracruz experienced changes in land use with increased river runoff delivering more sediment to the ocean that could shift seawater chemistry in coastal waters causing the observed coral Sr/Ca divergence in the near shore colonies. Increased sedimentation could stress coral colonies causes different biological responses evident in the coral Sr/Ca records.

KRISTINE DELONGLSU DEPARTMENT OF GEOGRAPHY & ANTHROPOLOGY

Assessment of Coral Sr/Ca Variations in Orbicella faveolata Colonies in Veracruz, Mexico

OCEAN SCIENCES 2016

Friday, February 26, 2016TIME: 2:00 PM – 2:15 PM LOCATION: RO5


RESEARCH WORKS

It has been well established that the composition of oil, when spilled into the marine environment, undergoes substantial changes caused by weathering. The general sequence of this compositional change begins with straight chain alkanes (the fastest to degrade), followed by low molecular weight branched and cyclic alkanes and, finally the aromatics. Most resistant to weathering are the higher molecular weight cyclic and branched alkanes (i.e., the “forensic biomarker compounds” such as the hopanes and steranes) and tri-aromatic ringed steroids. The composition of these biomarker compounds is particularly resistant to change because they are not affected by evaporative weathering,

are not water soluble, and are not readily degraded by microbial and/or photo-oxidation. However, after extensive time in the environment, being subjected to numerous weathering factors, biomarker compositional patterns are beginning to exhibit significant changes. This presentation will describe the general weathering patterns of petroleum residues in sediment samples collected from marsh areas of coastal Louisiana over a five year period. Particular attention will focus on compositional changes that have been observed in the steranes and diasteranes compounds that traditionally have been considered the most resistant to compositional changes due to weathering.

EDWARD OVERTONDEPARTMENT OF ENVIRONMENTAL SCIENCES

Weathering Patterns of Forensic Biomarker Compounds and PAHs in Coastal Marsh Sediment Samples since the 2010 Deepwater Horizon Oil Spill

OCEAN SCIENCES 2016

Friday, February 26, 2016TIME: 3:30 PM – 3:45 PM LOCATION: RO5


RESEARCH WORKS

On April 20, 2010, the Macondo well in Mississippi Canyon 252 blew and the well gushed oil uncontrollably into the sea and subsequently into the saltmarsh. Aromatics were measured and found to increase until May 2011. In Sept 2012, Hurricane Isaac remobilized oil in the marsh further increasing aromatics once again and oiled areas of marsh that were previously not contaminated with Macondo oil. Over the course of the next year, monthly samples were taken and the aromatics decreased. Also, a large number of extracted oil samples emerged in the marsh that matched the Macondo oil, but differed significantly from the original patterns seen which we started calling “Pattern A” and “Pattern B.” Additionally, in 2013 an uptick in aromatic compounds was observed at previously-oiled sites and lesser so at some previously-unoiled sites. Associated with this increase in aromatics was a shift from mostly Pattern A oil to

more Pattern B oil or a combination of Pattern AB.

Previously, we’ve shown that the ants in the marsh are intimately connected to the terrestrial food web and that they are good indicators of the presence of stressors that affect food availability for vertebrates such as fish and birds. Initially populations of ants survived the oiling of the marshes but the population crashed in the summer of 2011 in response to the decreased food availability in the marsh. We started to see recovery of ants in the oiled areas in August 2012, but the populations were annihilated by hurricane Isaac. The ants largely recovered in the unoiled plots, but not in oiled plots in 2013, which matches the uptick in the aromatic compounds measured at the same sites. In 2015, we started to measure recovery of the ant population in the oiled areas but lack hydrocarbon data at this time to associate with the recovery.

LINDA HOOPER-BUIDEPARTMENT OF ENVIRONMENTAL SCIENCES

Tracking Macondo Oil in the Marsh: Sampling Directly via Sediment and Indirectly via Ants

louisiana state university - ocean sciences 2016 monday, february 22… · 2016. 2. 19. · the...

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