Factors impacting the formation & modification of sinking oil snow : Processes and Pathways K.L. Daly 1, U. Passow 2, C. Hu 1, N. Prouty 3, F. Mienis 4,A. Remsen 1, K. Kramer 1, and S. Murasko 5 1 University of South Florida; 2 UC Santa Barbara; 3 USGS, Santa Cruz, CA; 4 Royal Netherlands Institute for Sea Research, 5 Florida Fish & Wildlife
Why is Marine Snow Important? Marine snow affects transport and fate of components (including oil): Marine snow provides microhabitats (hot spots) for bacteria and protozoa with high turnover rates. Marine snow provides food for large invertebrates and fish entrance into the food web! Marine snow sinks (usually) a velocities significant enough to transport components to great depths Active microbial loop Marine snow high sinking velocities Effective transport to depth Mesozooplankton food, fecal pellets 1. Exporting toxic components (petroleum/dispersants) 2. Exporting a large volume/mass 3. Exporting highly degradable material to seafloor (avoiding microbial degradation in water column)
There are several pathways by which oil may be associated with rapidly sinking marine snow particles (= particulate transport pathway) OMAs: oil mineral aggregations (salinity and clay type affects aggregations) Physical coagulation of marine particles, e.g. diatoms that trap oil in interstices Microbially mediated formation of mucus snow, due to the presence of weathered oil consisting of oil carbon Doliolid fecal pellets (next example) Other zooplankton fecal pellets?
Example Pathways from Experimental Research
Oil Droplets in Fecal Pellets of Doliolids after Uptake of Dispersed Oil (poster) Richard F. Lee, G. A. Paffenhöfer and Marion Köster Oil droplet sizes (2 to 30 μm) were similar in size to their phytoplankton food. Oil droplets observed in doliolid stomach within four hours Fecal pellet production rate of 2 pellets/hr and oil droplet concentrations ranging from 10 to 85 droplets/ fecal pellet In these experiments, 36 and 90% of the oil droplets were discharged in doliolid fecal pellets.
% Organic Carbon in Marine Snow from Oil Based on δ 13 C Mucus oil snow: Bacterial mediated mucus production Forms in the absence of particles Forms only from weathered oil ~100% of δ13c in marine snow originates from oil Diatom aggregates (physical coagulation): Coagulation of diatoms D. fragilissismus or T. weissflogii Oil if present is trapped in interstices Any type of oil may be incorporated 16%, 65% & 91% of carbon in diatom aggregates originates from oil Passow unpubl.
Formation of mucus-oil snow 1. Marine oil snow forms in the absence of particles > 1 µm (NOT physical coagulation)! 2. Such marine oil snow forms ONLY in the presence of oil collected after the spill from the oil carpet or from photo chemically aged (altered) oil. Total Volume mm 3 tank 1 300 200 100 0 No marine snow No Oil No marine snow Crude Oils Spill Oil A Crude Oil aged > 3 wks. GRIIDC ID: R1.x132.139.0004 Passow unpubl
Microbial activity in marine oil snow Microbial exoenzyme activity is increased in marine oil snow Ziervogel et al. 2012. PLoS One
Environmental Complexity: Satellite Data and Field Observations
Environmental Factors Affecting Lower Trophic Levels August 2010 unusual conditions Deepwater Horizon Oil Spill Released Mississippi River water created very shallow density layer offshore High chlorophyll concentrations (1.5 2 ug/l) Satellite data showed ocean color anomaly (Hu et al. 2011) Decreased phytoplankton photosynthesis Highest marine snow concentrations observed over 18 cruises
Influence of Riverine Outflow Caernarvon Discharge and Mississippi River Flow 1990 2011 Eberline (2012) MS Thesis LSU
Timing and duration of freshwater events in Breton Sound. Caernarvon (blue) and Mississippi River (gray)discharge between March and September 2010 and 2011 at USGS water quality sites. 2010 2011 Eberline (2012) MS Thesis LSU
Model Output Showing Spatial Extent Surface Salinity Fields: August 2010 R. He model: http://omgsrv1.meas.ncsu.edu
Challenge: Assess Oil Impacts vs. Time Varying Ecosystem Complexity August 2013 Dr. Ruoying He (NCSU) Model http://omgsrv1.meas.ncsu.edu
C IMAGE Time Series Cruises: Field Observations
August 2010: Strong Surface Low Salinity Layer May 2010 Aug 2010 Dec 2010 Feb 2011 May 2011 Sept 2011
Satellite Data: Phytoplankton Surface oil presence statistics Phytoplankton fluorescence anomaly during Aug 2010 compared to 8 yr climatology [Hu et al. 2011, GRL] 17
Impacts on Phytoplankton: August 8 10 2010 Chlorophyll positive anomaly (> 1 mg m 3 ) in Northern Gulf of Mexico (Hu et al. 2011 GRL). Also high in situ chlorophyll observed (2 mg m 3 ) Phytoplankton photosynthetic capacity decreased (DCMU) Phytoplankton diversity decreased at stations near DWH Diatom dominated community Thalassionema nitzschioides Dactyliosolen fragilissimus Leptocylindrus minimus Pseudo nitzschia spp. Phytoplankton images courtesy of FWRI
Chlorophyll (ug/l) profiles during years of high river outflow Chlorophyll maxima in near surface layer Highest chlorophyll maxima out of 18 cruises August 2010 August 2013 2010 DSH08 2010 DSH09 2013 DSH08 2013 DSH09 0.00 5.00 10.00 0.0 0.00 5.00 10.00 0.0 0.00 5.00 10.00 0 0.00 5.00 10.00 0 50.0 50.0 50 50 Depth (m) 100.0 150.0 200.0 Depth (m) 100.0 150.0 200.0 Depth (m) 100 150 Depth (m) 100 150 250.0 250.0 200 200 300.0 300.0 250 250
SIPPER Imaging System
Total Zooplankton Abundance May 2010 Aug 2010 Dec 2010 Feb 2011 May 2011 Sept 2011 Max zooplankton biomass during high stratification, high chl
Examples of SIPPER images of non oiled and presumably oiled detrital particles collected within 20 miles of the DWH site between May August 2010 Particle size range: 0.23 to 9 mm 2 Most particles 0.23 1 mm 2 size range
Marine Snow Profiles (No./m3) High river outflow Ocean salinity High river outflow August 2012 similar to 2011
Satellite Data: Time Series POC Concentrations MODIS derived watercolumn POC over an area of about 32 km x 37 km centered at 29.1115N 87.5615W Data from C. Hu (USF)
Is Export of Surface Organic Matter Triggered by Riverine Processes?
Rapid Sinking velocity of marine oil snow collected in situ in May 2010 The sinking velocity of the marine snow that formed in the vicinity of the oil spill was high. Sinking velocity (m/day) 600 500 400 300 200 100 0 0 2 4 6 8 ESD (mm) GRIIDC ID: R1.x132.139.0001 June 2013 St Pete, FL. Passow et al. ERL 2012
Seasonal and interannual variation in organic carbon flux, based on results from a sediment trap located at 29.1115 N 87.5615 W. Viosca Knoll region @ 480 m
Passow sediment trap 2 miles SW DWH
Sediment trap results: Organic Carbon 26 at ~1400 m depth POC mg m 2 d 1 TEP Gxeq. mg m 2 d 1 150 100 50 POC 0 8/1/2010 8/1/2011 10000 1000 Same date 2011 & 2012 Focus on cup 1: Exceptionally high POC sedimentation Skeletonema (diatom, brackish) bloom diatoms 28º 42.360N, 88º 25.325W, 100 10 Passow, Noethig, Asper, unpubl. 1 8/1/2010 8/1/2011
Group 1: Oil associated Marine Snow Factors impacting the formation & modification of sinking oil snow Nutrients Riverine Influences Salinity Clays OMAs Marine oil snow Feces, feeding Mucus production structures, removal Marine biota Mucus oilsnow Aggregates with Oil Aggregation & Fragmentation Petrogenic, weathering Oil, Dispersant Dispersant Pyrogenic