Abstract:

The water samples were collected from coastal waters at Cocodrie, LA. In the laboratory, one-milliliter aliquots of the coastal water were used to inoculate 125-milliliter glass flasks containing artificial seawater (Instant Ocean) enriched with inorganic nutrients and vitamins according to the protocol for f/2 medium (Guillard, 1975). All experiments were run in triplicate. The control flasks received no added oil. The treatment flasks received oil at concentrations ranging from 0.1 to 19.2 parts per million according to the protocol of Singer et al. (2001). The flasks were incubated in front of a bank of fluorescent lamps that provided about 300 micro-mol quanta per square meter per second of visible light on a continuous basis. The temperature was 20 ± 1 C. The growth of the phytoplankton was monitored via optical density (OD) measured at a wavelength of 750 nm on a spectrophotometer. Growth rates were estimated from the slope of the natural logarithm of the OD during the period of time, typically several days, during which the cells were in log phase growth. OD measurements were made at intervals of 12 hours.

Suggested Citation:

Laws, Edward. 2015. Effects of Macondo oil on growth rates of Gulf of Mexico phytoplankton.. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N7K35RMS

Purpose:

The laboratory experiment studies the effect of oil concentration on the growth rate of phytoplankton.

Data Parameters and Units:

Growth rates of phytoplankton relative to control treatments as a function of oil concentration. File summary.xlsx: duration of time lag worksheet: time between inocculation of the medium and when phytoplankton started to grow (days); growth rates worksheet - oil concentration (0.1, 0.3, 0.6, 1.2, 2.4, 4.8, 6.9, 19.2 parts per million) and growth rate (per day); pigment analysis worksheet - ppm (oil concentration 0.1, 0.3, 0.6, 1.2, 2.4, 4.8, 6.9, 19.2 parts per million), mL = sample volume in milliliters, pigment (CHLDA = chlorophyllide a, CHLC = chlorophyll c, PER= peridinin, BUT = 19'-butanoyloxyfucoxanthin, FUCO = fucoxanthin, HEX= 19'-hexanoyloxyfucoxanthin, PRAS=prasinoxanthin, NEOX=neoxanthin, VIOLA=violaxanthin, DDX=diadinoxanthin, ALLOX=alloxanthin, DTX=diatoxanthin, LUT= lutein, ZEAX= zeaxanthin, MV-CHLB=monovinyl chlorophyll b, A-CAR= alpha carotene, B-CAR= beta carotene,DV- CHLA=divinyl chlorophyll a, MV-CHLA=monovinyl chlorophyll a,TOTCHLA=total chlorophyll a), pigment concentration nanogram per liter; File OD summary4.xlsx: optical density measured at a wavelenght of 750 nm for control and oil treatments concentration (ppm) over time (Time reports as M-DD-YYYY(experiment day))

Methods:

Samples of water from the coastal zone of Louisiana were collected on multiple occasions. One-milliliter aliquots of this water were added 125-milliliter glass flasks containing artificial seawater enriched with inorganic nutrients and vitamins. All treatments were run in triplicate. One set of flasks served as the control treatment. Others contained oil (water-accommodated fraction) at concentrations ranging from 0.1 to 19.2 parts per million. The flasks were incubated at 20 degrees Celsius in front of a bank of fluorescent lights that provided continuous irradiance of roughly 300 micro-mol quanta per square meter per second of visible light (400–700 nm wavelength range). The growth rates of the cultures were monitored by optical density readings at 750 nm. The growth rates in the treatments containing oil were divided by the growth rates in the control flasks to quantify any effects of the oil on the growth rates of the phytoplankton. These experiments have been repeated up to four times with different samples of Gulf of Mexico water. There is no evidence of any effect of the oil on growth rates of the phytoplankton community at oil concentrations as high as 9.6 parts per million. Some depression (about 30%) of growth rate is evident at an oil concentration of 19.2 parts per million.

Instruments:

spectrophotometer

Error Analysis:

The error bars in the figure are standard deviations of the mean values.

Provenance and Historical References:

Guillard, R.R.L., 1975. Culture of phytoplankton for feeding marine inveretebrates. In: Smith, W.L., Chanley, M.H. (Eds.), Culture of Marine Invertebrate Animals. Plenum Press, New York. Singer, M.M., Aurand, D.V., Coelho, G.M., Bragain, G.E., Clark, J.R., Sowby, M., Tjeerdema, R.S., 2001. Making, measuring, and using water-accommodated fractions of petroleum for toxicity testing., International Oil Spill Conference, pp. 1269–1274.

Individual Files: