The role of the copepod Calanus finmarchicus in affecting the fate of marine oil spills
Doctoral thesis
Permanent lenke
http://hdl.handle.net/11250/2372794Utgivelsesdato
2015Metadata
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- Institutt for biologi [2616]
Sammendrag
Background:
Oil spills in marine environments are subject to biological, physical and chemical
weathering processes, including entrainment of oil as droplets in the water column. The
oil droplets with diameter < 100 μm are within the size range of particles ingested by
marine filter-feeders. Ingestion of oil droplets has been reported for several species of
zooplankton, including the calanoid copepod Calanus finmarchicus. C. finmarchicus is
ubiquitous in the North Sea, the Norwegian Sea, and the Barents Sea. Based on their
high abundance, high feeding activity, and indiscriminate feeding strategy, copepods
have been suggested to contribute to weathering and transport processes of oil spills.
Aim:
The aim of this thesis was to investigate how the abundant marine filter-feeder C.
finmarchicus influence transport and weathering of oil dispersions.
The work included:
1. A modelling approach using the oil spill contingency and response model
OSCAR with a filter-feeder module implemented, determining the quantity of an
oil spill that can be removed by ingestion by C. finmarchicus.
2. Laboratory studies determining:
a. Concentration of oil in C. finmarchicus feeding in dilute oil dispersions
b. Feeding activity of C. finmarchicus in dilute oil dispersions
c. Accumulation of oil compounds to C. finmarchicus from dilute oil
dispersions and the corresponding water soluble fraction (WSF)
d. Viable and total microbial communities in clean and oil-containing feces
from C. finmarchicus
e. Biodegradation of dilute oil dispersions in the presence of feces from C.
finmarchicus
Results and discussion:
The modeling approach estimated that C. finmarchicus may ingest between 1 and 40%
of an oil spill. The estimates in the lower ranges (≤ 2%) were suggested to be realistic,
since the high range estimates combined extreme values for several input parameters.
The input parameters that had highest impact on the quantity of oil removed by C.
finmarchicus were the size limit for droplets ingested, and the population density.
The laboratory studies showed that at fixed density (50 ind. L-1) and oil droplet size
(diameter < 40 μm), the concentrations of oil in C. finmarchicus biomass were ranging
between 3 and 14 mg oil kg-1 (exposure concentration 5.5-0.3 mg L-1). Both the concentration of oil in the biomass and the feeding activity of the copepods were low at
the high concentration of oil. The feeding activity were rapidly significantly reduced at
low concentrations of oil (17 h, 1.4 μL L-1,) indicating that C. finmarchicus have largest
impact on oil spills at an early stage and at low concentrations. Ingestion of oil droplets
contributed to rapid accumulation of all oil compounds. Accumulation from the WSF
reached steady state for the low lipophilic (log Kow < 5) compounds within 24 hours,
while the high lipophilic compounds (log Kow > 5) did not reach steady state within the
96 hour exposure. Over time, lower concentrations of the low lipophilic compounds
were observed in oil dispersion exposed C. finmarchicus compared to WSF-exposed.
This indicated elimination to the water, and may cause redistribution of these
compounds during oil spills. Since the concentration of the high lipophilic compounds
not was affected similarly, C. finmarchicus biomass may act as a sink for high lipophilic
oil compounds.
The oil-containing feces from C. finmarchicus feeding in dilute oil dispersions
contained significantly higher concentrations of viable oil-degrading microorganisms.
The total microbial communities were similar between the clean and oil-containing
feces, and the oil-degrading activity was suggested to be mediated by indigenous feces
bacteria. The presence of oil-containing feces resulted in higher biodegradation of the nalkanes
in a dilute oil dispersion, while the presence of clean copepod feces resulted in
lower biodegradation of the n-alkanes. This supported the suggestion that the
indigenous feces bacteria were mediating the oil-degrading activity. These bacteria may
have preferred carbon in feces prior to the carbon in the n-alkanes. The oil and copepod
feces also formed large agglomerates. These may increase the sedimentation of
relatively un-weathered oil towards the seabed during oil spills, depending on their
effective density. The presence of clean C. finmarchicus feces resulted in higher
biodegradation of the aromatic fraction, suggested to be caused by leaking of nutrients
from the copepod feces. The presence of C. finmarchicus feces can thus increase the
biodegradation of the dissolved fraction of an oil spill.
Conclusion:
The results indicated that a substantial concentration of oil can be contained in the C.
finmarchicus biomass during oil spills. Further, C. finmarchicus biomass can contribute
to redistribution of the low lipophilic oil compounds and function as a sink for dissolved
high lipophilic compounds. The excretion of oil in feces increased the concentration of
viable oil-degrading microorganisms in the feces, mediated by the indigenous feces
bacteria. Biodegradation of the n-alkanes was dependent on the quantity of feces
present, while the biodegradation of the aromatic compounds was increased in the
presence of copepod feces.
Består av
Paper 1: Nepstad, Raymond; Størdal, Ingvild Fladvad; Brönner, Ute; Nordtug, Trond; Hansen, Bjørn Henrik. Modeling filtration of dispersed crude oil droplets by the copepod Calanus finmarchicus. Marine Environmental Research 2015 ;Volum 105. s. 1-7 http://dx.doi.org/ 10.1016/j.marenvres.2015.01.004 The article in is reprinted with kind permission from Elsevier, sciencedirect.comPaper 2: Nordtug, Trond; Olsen, Anders Johny; Salaverria-Zabalegui, Iurgi Imanol; Øverjordet, Ida Beathe; Altin, Dag; Størdal, Ingvild; Hansen, Bjørn Henrik. Oil droplet ingestion and oil fouling in the copepod Calanus finmarchicus exposed to mechanically and chemically dispersed crude oil. Environmental Toxicology and Chemistry 2015 ;Volum 34.(8) s. 1899-1906 http://dx.doi.org/10.1002/etc.3007 (C) 2015 SETAC Copyright © 1999-2016 John Wiley & Sons, Inc. All Rights Reserved.
Paper 3: Størdal, I.F., Jenssen, B.M. Uptake of PAHs in Calanus finmarchicus from seawater petroleum oil dispersions and the water soluble fraction
Paper 4: Størdal, Ingvild; Olsen, Anders Johny; Jenssen, Bjørn Munro; Netzer, Roman; Hansen, Bjørn Henrik; Altin, Dag; Brakstad, Odd Gunnar. Concentrations of viable oil-degrading microorganisms are increased in feces from Calanus finmarchicus feeding in petroleum oil dispersions. Marine Pollution Bulletin 2015 ;Volum 98.(1-2) s. 69-77 http://dx.doi.org/10.1016/j.marpolbul.2015.07.011 The article in is reprinted with kind permission from Elsevier, sciencedirect.com
Paper 5: Størdal, Ingvild; Olsen, Anders Johny; Jenssen, Bjørn Munro; Netzer, Roman; Altin, Dag; Brakstad, Odd Gunnar. Biotransformation of petroleum hydrocarbons and microbial communities in seawater with oil dispersions and copepod feces. Marine Pollution Bulletin 2015 ;Volum 101.(2) s. 686-693 http://dx.doi.org/10.1016/j.marpolbul.2015.10.029 The article in is reprinted with kind permission from Elsevier, sciencedirect.com