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Cruise 15: R/V Pelican M15

MechanismsControlling Hypoxia on the LouisianaShelf 6 April - 11 April 2010

Port: LUMCON, Cocodrie, Louisiana
Mobilization: 5 April
De-Mobilization: 12 April 2010
TAMU departure: 7:30 AM (in front of O&M)
Cruise: 6 - 11 April 2010 Return: 12 April 2010

R/V Pelican
Objectives

(a) to conduct 24-hour microbial, zooplankton, phytoplankton,DOC/POC, and biomarker process measurements at 3 stations;
(b) to obtain a series of box-cores;
(c) to obtain zooplankton and phytoplankton flux measurements;
(d) to collect hydrography data

Personnel

Scientists
Dr. Thomas S. Bianchi: Chief Scientist, Biogeochemistry Leader
Dr. Mike Dagg: Zooplankton Leader
Dr. Heath Mills: Microbial Process Leader

Technicians
2 LUMCON techs

Students
Li Shen: TAMU, CO Graduate Student (female)
Jun Zhao: OUC, CO Graduate Student (male)
Rick Smith: TAMU, CO Graduate Student (male)
Kelly Cole: TAMU, PO Graduate Student (female)
Stuart Pearce: TAMU, PO Graduate Student (male)
Alicia Shepard: TAMU, CO Graduate Student (female)
Jiang Yuelu – TAMUG, postdoc (female)
Kimberly Janusaitis –TAMUG, research assistant (female)
Robin Wilson, Dalhousie University, Graduatestudent (male)

Winch Operators
Two provided by LUMCOM

Texas/Louisiana Coast
Funding Agent

National Oceanic and Atmospheric Administration (NOAA), Centerfor Sponsored Coastal Ocean Research.

ParticipatingInstitutions

TAMU – College Station,Dept. of Oceanography
TAMUG - Marine Biology Department
LUMCON
Dalhousie University University of Texas Institute for Geophysics
Louisiana State University: Dept. of Ocean.and Coastal Studies (remote sensing)
Coastal Carolina University

Project Website:

http://hypoxia.tamu.edu/

Data Collection

Instrumentation and Equipment (LUMCON): 12-bottle Rosette (with bottle 1 (5 L)
CTD package (PAR, fluorescence, DO, OBS,T,S)
Navigation computers
Flow-through system computers
Nutrient sample bottles, syringes, and filters (TAMU)
(nutrients samples will be filtered and frozen on this cruise)
Winkler dissolved oxygen titration system (*chemicals prepared by GERG)
Titrator, sample bottles, chemicals
(large) LUMCON box-core
Shipboard ADCP: 600 kHz Workhorse (new LUMCON instrument)
Ashtech GPS (LUMCON)
Salinity bottles (GERG
Bucket (TUMU to provide)
Assorted box-coring materials (Mills and Zhao, and Smith)
Chest Freezer (LUMCON)
TSP/POC filters (Li Shen and Smith)
Chlorophyll filters (Quigg to provide)
Microbial filters (Mills to provide)
2-m intake system for MIDAS flow-through system (LUMCON)
Vacuum pump/filtration system/generator (Li Shen and Smith)
Microbial filtration system (Mills)
Digital cameras, DVDs (All)

General ProcessMeasurements:


CTD (continuous): salinity, temperature, DO, transmission,chlorophyll, PAR
Bottle: ammonia, nitrate, nitrite, phosphate, silicate, urea, dissolved oxygen,salinity
microbial populations
Bucket salinity and nutrients
3-m salinity, temperature (MIDAS), >chlorophyll (Chelsea fluorometer)
Box-core (freeze samples for on-shore analysis): biological/chemical coresamples
Nutrient samples will be filtered, frozen, and stored for on-shore chemicalanalysis
Salinity bottles will be stored for analysis on shore

ResearchGroup Measurements:

Bianchi:

Niskin bottlesamples: From the water column (Niskin bottles) we will sample one or twodepths in the upper layer, and one or two depths in the lower sub-pycnoclinelayer. We will close multiple bottles at each depth depending on water needs. AllPOM and DOM duplicate samples will be collected from CTD/rosette casts at 0, 6,12, 18, 24 hr during each 24 hr station = 5 cycles per 24 hr.

Anticipated water needs are:
DOC, POC, amino acids, and plant pigments (Bianchi) –approximately 500 mL for each Sediments: sediment cores will be collected for surface anddown-core samples. Surface (0-2 cm)samples will be used to examine benthic-pelagic coupling with sedimentaryorganic carbon (SOC) and plant pigments.

Dagg/Quigg:

We would sample at0, 6, 12, 18, 24 hr during each 24 hr station = 5 cycles per 24 hr station). Ateach station we would like CTD/rosette casts every 6 hr to determine watercolumn structure (including the depth of the pycnocline – we assume there willbe a two layer water column). We will take water for preserving and forexperiments.

Niskin bottle samples: From the water column (Niskin bottles) wewill sample one or two depths in the upper layer, and one or two depths in thelower sub-pycnocline layer. We will close multiple bottles at each depthdepending on water needs.

Anticipated water needs are:
Bacteria (Dagg) - a few 100 mL from all depths for bacterialcounts (flow cytometer) - freeze in liquid N
Chlorophyll (Dagg, Quigg) – about 1 L from all depths sampled,for size fractionated chlorophyll to be measured on shipboard and for frozensamples to be analyzed on shore. We will also do chlorophyll analyses from yourbucket samples.
Fecal pellets (Dagg) - about 10 L from each sample depth, to besieved through a 20 μm screen, backwashed into a small jar and preserved inweak formalin.
Zooplankton net tows (Dagg) - will do zooplankton net tows tocharacterize the zooplankton community above and below the pycnocline. Twodepth strata will be sampled - from the pycnocline to the surface and from nearbottom to the pycnocline. Duplicateseach time period; samples will be collected either every 6 hr or every 12 hr,depending on time availability.

Fennel:

No measurements inparticular. Graduate student Robin Wilson is participating in the cruise togain seagoing experience (a graduate program requirement he has to fulfill). Heis willing to help with anything as needed.

Mills:

Active microbialpopulations in water column and sediment; sediment geochemical profiles (SO42-,H2S, Fe(II), Fe(III), TRS, Cl, TOC)

sampling stations

Figure 1. Locations at 3 anchor process stations along the 20 m isobath. Ignore the locations indicated by the red circle.

Cruise Synopsis

This cruise will examine short-term biogeochemical processes at 3 stations located on the inner Louisiana shelf and how they with relate to physical processes. This is the first time in the history of the MCH program that such an emphasis will be made on the biogeochemical flux and rate measurements. The main objective of this research is to investigate the mechanisms that control the onset hypoxia, which occurs off of coastal Louisiana each summer, by examining dissolved and particulate organic matter (DOM and POM) cycling rates and sources in the region between the Atchafalaya and Mississippi River Plumes. The methods include deployment of real-time reporting instrument systems, an extensive coupled biological/physical/sediment numerical modeling effort, and shipboard process studies (to complement the real-time observations). Sampling on this cruise will consist of CTD/bottle casts and box-cores. Depending on time and weather considerations, we have planned biogeochemical sampling for 24-hour at each of the 3 anchored stations. A test station will be done on the transit to the first CTD station to train graduate students on CTD and rosette sampling and test scientific apparatus. The ship's flow-through system will be run for the duration of the cruise. Bucket nutrients and salinity may be done between planned stations to best locate the river plume. A bottom-tripped frame containing 5 L Niskin bottles, CTD, and transmissometer will be deployed at each station in addition to the 12-bottle rosette. An RDCP current profiler and short-term sediment trap will be deployed at the start of the station. A shipboard 600-kHz ADCP will run throughout the cruise. We will also conduct a number of additional complementary and related experiments during the course of this cruise. These experiments involve the collection of additional water and sediment samples for analysis both at sea and on shore.

Prokaryotic community ecology: A combined molecular and geochemical approach will provide a better understanding of the prokaryotic community ecology. Building upon data from previous cruises, sediment associated prokaryotic activity will be assessed by observing transitions in sulfur and iron valence states and concentrations. Supporting anion and cation measurements will provide a more complete view of the potential nutrient cycling. The inorganic chemistry will be compared to the organic chemistry and the physical sediment characteristics. The focal point of the sediment biogeochemistry will be high-resolution sampling and sequencing of the active prokaryotic populations (i.e., Bacteria and Archaea domains). Structural and functional gene targets will be used to determine active metabolic processes within the sediment. Data collected on this cruise will be compared to previous cruises to identify potential trends in population distribution and activity.

For the first time on an MCH cruise, the water column prokaryotic populations will also be subjected comprehensive molecular analysis. Focus will shift from sulfur and iron to nitriogen related populations and processes. Again, active populations will be observed through both structure and function based comparisons. Geochemistry obtained via shipboard operation will be used to support molecular analysis. Data collected will provide baseline assessment of water column prokaryotic ecology prior to the onset of summer hypoxia.