how$an$offshore$oceanic$ecosystem$responded$ … · 2019-11-08 · macondo blowout • point...

With contributions from:

Sara Kleindienst, Kim Hunter, Melitza Crespo-Medina,

Sairah Malkin, Matt Saxton & Ryan Sibert (Univ. Georgia)

Sharon Grim & Mitch Sogin (Marine Biological Laboratory)

How$an$offshore$oceanic$ecosystem$responded$to$extreme$perturba6on:$$

!

The!2010!Gulf!of!Mexico!BP/Deepwater!Horizon!oil!well!blowout.!Samantha$Joye$

Dis6nguished$Professor$of$Marine$Sciences$Project$Director:$Ecosystem$Impacts$of$Oil$and$Gas$Inputs$to$the$Gulf$(GoMRI)$

Department$of$Marine$Sciences,$University$of$Georgia$

EKmail:$mjoye@uga.edu$$

Gulf of Mexico - a petroleum basin - salt tectonics drives gas and oil seepage

Harry Roberts, LSU

ECOGIG Video Caroline Johannson

Ian MacDonald

Map: Ian MacDonald (FSU)

Human oil extraction short circuits the “geologic” C cycle

• natural oil release <2,600 bbl/day >50 Million reservoir Turnover time

www.globe.gov/projects/carbon

Map: Ian MacDonald (FSU)

Human oil extraction short circuits the “geologic” C cycle

• natural oil release <2,600 bbl/day • ~US oil use ~19,110,000 bbl/day •global oil use ~64,000,000 bbl/day ~<1000 yr TT

Humans are mining a resource that took 100’s of millions of years to produce, and which naturally cycles back into the active C cycle on a similar time scale, and releasing it directly to the Earth’s atmosphere in the blink of a geologic eye

www.globe.gov/projects/carbon

Natural seeps • >20,000 documented seeps • ~1,000 surface oil slicks • natural release ~ 2,600 BOPD • diffuse, slow, variable in time/space

Natural seepage vs. the Macondo Blowout

Macondo Blowout • point source injection (jet) • at least 57,000, up to 70,000, BOPD • 84 days @ 1500m water depth • 460,539 – 690,176 tonnes of oil + gas; ~50% entrained in deepwater

Still, offshore drilling will continue

Gulf UDWD - 2000-3000 m water depth - 46 billion BOE (OCS Report MMS 2100-22)

Maximal surface oil cover (early June)

Major points

• natural hydrocarbon degrading communities are limited by biological

and environmental factors

• impact of dispersants

on microbial community composition and oil

biodegradation activity

• microbial oil snow formation and sedimentation

Head et al. 2006 Nat Rev Microbiol.

Kleindienst, Paul & Joye, Nat. Rev. Microbiol. 2015

Hydrocarbon metabolism is mutualistic & synergistic *regulation is complex and poorly understood*

What is the impact of chemical dispersants on microbial hydrocarbon degradation & community

composition?

Dispersants drive microbial community evolution

* * * *

Potential key players involved into hydrocarbon degradation Dispersant treatments = Colwellia spp. Oil only = Marinobacter spp. Kleindienst et al. in press

Oligotypes

Notably, dispersant addition selected for specific

oligotypes of Colwellia

That was not the case for Marinobacter or Cycloclasticus

(or Oceaniserpentilla)

Do these different microbial communities function

similarly?

Is activity stimulated by dispersant addition?

d

o

Kleindienst et al. in press

**if not visible, error bars are indistinguishable from bar

Degradation rates of alkanes (~hexadecane) and polycyclic aromatic hydrocarbons (~napthalene) were

reduced in the presence of dispersants

Kleindienst et al. in press

Microbial “oil snow”

dual CARD-FISH hybridizations using probes targeting Bacteria (green; o-t) and Alteromonadales (incl. Marinobacter) (red; o-t).

! Nutrients + oil + dispersants (11, 15 days)

! Dispersants only (“lasso” after 15 days)

! oil (g & h ), dispersed oil (i)

(a) (b) (c)

(d) (e) (f)

(g) (h) (i)

(j) (n) (m) (l) (k)

(o) (p) (q)

(r) (s) (t)

10 µm

5 µm

10 µm

500 µm

500 µm

500 µm

Seafloor “footprint” of oil snow sedimentation event

Chanton et al. 2014 ES&T

2-15% of discharged oil = 8 to 96 × 103 tonnes oil or 8 to 96 Gg of oil * covering a seafloor area of 3,000 to 8,400 km2 (avg. thickness ~1cm) *

Similar microbial “fingerprint”

Joye et al. 2015 Science

What was the fate of Macondo oil?

Conclusions • Chemical dispersant addition altered

microbial community composition and reduced oil degradation rates

Conclusions •  Chemical dispersant addition altered microbial community composition and

reduced oil degradation rates

• Chemical dispersant addition also led to the highest rates of marine oil snow formation

Conclusions •  Chemical dispersant addition altered microbial community composition and

reduced oil degradation rates •  Chemical dispersant addition also led to the highest rates of marine oil snow

formation

• Sedimentation of weathered oil-containing marine snow was a considerable fate for Macondo oil; this process was significantly stimulated by microbial processes

Conclusions •  Chemical dispersant addition altered microbial community composition and

reduced oil degradation rates •  Chemical dispersant addition also led to the highest rates of marine oil snow

formation •  Sedimentation of weathered oil-containing marine snow was a considerable

fate for Macondo oil; this process was significantly stimulated by microbial processes

• The Gulf system is resilient; some of response efforts may have impaired that resiliency

Thank You