Detecting Chronic Effects Of Oil Development In Caddo Lake
Charles W. Ramcharan Dept. Biological Sciences Louisiana State University Baton Rouge, LA
Louisiana Oil Spill Research And Development Program (OSRADP) Ramsar area Oil development area Munitions dump Lake ‘O t he Pines
Big Cypress Bayou Oi l Ci t y Caddo Lake Map Red Ri ver
Caddo Lake
10 km Texa s Louisiana Shreveport 6.3 miles NW-Basin near RAMSAR
North-west basin of Caddo Lake in Ramsar watershed area. Main Basin
Main basin of Caddo Lake. Oil head in North Arm
Active oil head found in the North Arm of Caddo Lake. Historical Marker – First over-water oil well
Historical Marker for first oil well in Caddo Lake. Early wells on Pine Island?
Some of the first wells in Caddo Lake. Early wells in main basin
Extensive oil field in Caddo Lake. The Problem
• Chronic effects of oil development in freshwater lakes are not well understood • Chronic effects may be difficult to identify because many disturbed ecosystems face multiple stressors • Usually there are available few long-term, pre- and post-perturbation data Lake Food Web Reconstruction
Game Fish
Planktivorous Fish
Invertebrate Predators Small Large Zooplankton Zooplankton Benthic Invertebrates Inedible Algae Edible Algae
Lake Sediment Handle Purge valve PVC coupling
Lake Coring
1 m Transparent core tube Transparent liner Core catcher Nosepiece
Core from Caddo Lake showing about 70 years of accumulation. (Army Corps of Engineers) Applications Of Paleo- Limnology
• Impacts of agriculture,urbanization, and forestry • Long-term estimates of fish production • Effects of acid precipitation • Determining frequency and intensity of droughts • Studies of climate change • Fish stock degradation due to overfishing • Effects of different types of fish predation Oil contamination site Lake ‘O t he Pines
Big Cypress Bayou Oi l Ci t y Expt. Design Red Ri ver
Metal contamination site Caddo Lake Reference site
10 km Texa s Louisiana Shreveport 6.3 miles Metal Contamination In LOP And Caddo Lake (406 + 66.0) 150 Lake O’ the Pines ) -1 Caddo Lake
100
50 Metal Concentration (mg L Metal Concentration 0 c c n i m r n y m e d r n o n u o a i u p u b e i Ir e Z r p c s mi * L a r m o r o e C A d a r C . h M C g C r -1 O (*Iron levels are g L ) Variables
Dating - 210Pb and 137Cs using a gamma-ray counter
PAH’s - some residues of creosote are refractory - detectable with HPLC Metals - metal contamination can be detected using AA
Foodweb - various degradation products of phytoplankton phytopigments are detectable with HPLC - lignins produced by rooted plants are also detectable with HPLC - invertebrate hard-parts can be studied by light microscopy A Solution
• Use sediment records to re-create long-term data. • Compare sediment profiles before and after perturbation • Compare sediment profiles in impacted and reference systems Statistical Analyses – Randomized Intervention Analysis 800
600
400 Frequency
200
Dobserved = 61 p<0.001 0 0 20406080
Drandom Cesium Dating Results 0 2000
1980
1960 -10 1940
1920 Year
1900 -20 Core A 1880
Sediment (cm) Depth Core B 1860
1840 -30 0.0 0.5 1.0 1.5 2.0 2.5 Cesium Level (pCi g-1 dry wt.) Sedimentation Rates
Our Value (0.18)
0.0 0.1 0.2 0.3 0.4 0.5 0.6 Sedimentation Rate (cm yr-1) James Bayou Profile
Flooded James Bayou
Original James Bayou Summary
• Acute effects of oil development in Caddo Lake occurred (1920-19 • Chronic effects may continue today due to creosote • Lake history can be re-constructed using paleo-limnology.
• Cores can be dated successfully. • Sedimentation rates low and variable.
• Now underway: 210Pb dating, phytopigments, invertebrate hard pa • Bottom features will be revealed using geo-referenced, side-scan Charles W. Ramcharan Dept. Biological Sciences Louisiana State University Baton Rouge, LA
Louisiana Oil Spill Research And Development Program (OSRADP) Lake History
Before 1850 • Caddo Lake exists as an ephemeral water body. • The lake area was always at the least a wet marsh. • A lake would form whenever a log-jam blocked the outflow river.
1850-1910 • Lake was formed by a large log jam. • Army Corps of Engineers replaced the log jam in 1910 with an earthen dam. • Dam served to raise the water level enough to float barges carrying drilling machinery. 1920 – 1970’s • Hundreds of oil platforms installed in the lake, then decommissione • Oil rigs constructed of creosote-soaked timbers. • Decommissioned rigs were cut down and the timbers were left on the lake bottom. Summary
• Caddo Lake is the first freshwater lake to have been subjected to oil development. • Chronic effects of oil development may be caused by leaching of creosote from oil rig support timbers. • Chronic effects are now only detectable by searching for clues in the lake’s sediments. • Cores from contaminated and reference sites will be dated. determinations of levels of phytopigments, metals, and invertebrate hard-parts will be performed. • Differences in time-series between the two sites will be attributed to effects of oil development. • A second comparison will be made between the creosote-contaminated site (Caddo Lake) and a metal-contaminate site (LOP) Historical Marker – Caddo-Pine oil field
Historical Marker for Caddo-Pine Island Oil Field. Another oil head in North Arm
A typical oil head located in the North Arm of Caddo Lak