Quick Start Guide to Using the Sampling Matrix Web Map:
To use the map, click on a sample site (the colored icons). Clicking on the individual site opens a data box that indicates date of collection, species collected, method of collection, geographic location coordinates, and also provides quantitative information on average PAH levels detected, the range or spread of levels detected (called Standard Deviation), and whether those levels exceed formal Levels of Concern for PAH exposure. Use the zoom tool on the left side of the map to get a closer look at tightly layered sample sites.
The Average PAH level found in the samples can be compared to the Level of Concern (LOC) (at the bottom center of the data box) for that species of seafood to see how the detected level relates to the LOC. Only two of the samples exceeded the LOC. The text below the map provides background and context for the seafood sampling aspect of GC-HARMS, as well as some further explanation of scientific terminology, and information on the scientific process used to determine Levels of Concern. Links are provided within the text to extend the depth of the general information but information in the FAQ / Glossary and the Quick Start should be sufficient to browse the map.
Background and Context for the Sampling Matrix Web Map:
The GC-HARMS sampling matrix map documents seafood sampling activities of the project’s Citizen Science Network of community fishermen in coastal Louisiana, Mississippi and Alabama, Working out of sampling hubs in Coden / Bayou la Batre (AL), Biloxi / Pass Christian (MS) and Houma (LA), local commercial and recreational fishermen sampled selected seafood species during the course of their work as commercial fishermen. Between July 2011 and January 2014, network fishermen collected samples of shellfish / crustaceans (white and brown shrimp, blue crab and oysters) and a variety of frequently consumed fin fish (speckled trout, sheepshead, red fish, flounder, red snapper, grouper). The seafood samples were taken from 208 discrete sites in Mobile Bay and coastal Alabama, coastal Mississippi, and inside / coastal waters of Louisiana. Sample sizes varied by species, ranging from single specimens of finfish to1 lb. lots of brown or white shrimp, 5 – 7 blue crab, and 20 oysters. The sampling matrix map marks each geographic point where samples were taken and subsequently analyzed, and reflects the scope and range of the tri-state sampling effort. (For additional information on how seafood samples were taken and prepared for laboratory analysis, click here.)
All seafood samples were analyzed with GC-MS (Gas Chromatography / Mass Spectrometry) technology in a UTMB laboratory to measure the petrogenic Polycyclic Aromatic Hydrocarbons (PAH) load in edible tissues. The petrogenic PAH are important components of crude oil and comprise a mixture of dozens if not hundreds of related but distinct compounds. Another class of PAH, called pyrogenic, are common products of incomplete combustion; some pyrogenic PAH are manufactured components of industrial materials such as roofing tar or creosote. GC-HARMS is only focused on the petrogenic PAH; the sole purpose of our project’s seafood sampling and analysis is to measure quantities of petrogenic PAH in targeted species within the Gulf food web.
- For an explanation of Parts Per Billion (ppb), click here.
- For explanation of the GC-MS process, click here.
- For more information about PAHs, click here.
- For information on linkages between detected PAH levels in targeted seafood species and bioavailability of PAH compounds, click here.
Looking at Special Features of the Map:
The GC-HARMS sampling matrix web map displays all of the specific sites where seafood samples were gathered during the project’s active sampling period (2011 – 2014). Each sample site is associated with a unique data box containing information on the species gathered: where and when the sampling occurred, which species was sampled, and results from a laboratory assay to determine polycyclic aromatic hydrocarbons (PAH) content. A species-specific Level of Concern is provided in each box so that detected levels of PAH may be compared with an established benchmark. A Level of Concern indicates the smallest quantity of a potentially toxic substance that might cause a measureable negative health outcome like cancer. For this project, we have used the known toxicity of Benzo(a)Pyrene (also known as BaP) – the most extensively studied individual PAH – as a benchmark Level of Concern in a validated bioassay. By comparing the biological response to a PAH mixture found in the sample with the B(a)P level of concern (indicated at the bottom in blue), map users can see whether this amount approaches the benchmark Level of Concern.
- For more information about Benzo(a)Pyrene, click here.
It should be noted that B(a)P may originate from both petrogenic and pyrogenic sources.
- For additional information on how project scientists developed the relationship between B(a)P and PAH levels detected in seafood samples to arrive at Levels of Concern found in the data boxes, click here.
A Standard Deviation value is also provided in the event that multiple organisms of the same species from the same site were analyzed. The Standard Deviation (SD) shows the amount of variability found in samples taken from the same site: a small SD means less variation in measurements; higher SD values show a wider spread among the measurements. (For additional information on the meaning and applications of Standard Deviation, click here.)
What the Aggregate PAH and LOC Information in the Data Boxes Mean:
The data box associated with each sample site provides a snapshot of the PAH load carried by the species sampled in that specific location at the time when the finfish, shrimp, crab or oysters were harvested. Because the species analyzed in this project are mobile – with the exception of reef-bound organisms like oysters – these data do not extend beyond that time frame and cannot be used to generalize on whether a fishing area is safe, or not. For a given oyster reef, it is useful to know that even though oysters may be “bound” together physically in the structure of a reef, there is still a great deal of variability among individual measurements of detected PAH. It is also important to bear in mind that the data provided in the GC-HARMS Sampling Matrix Web Map cannot be used to make definitive comparisons between / among fishing areas within the tri-state region. Finally, based on observed trends, any sample results displayed on this map that exceed PAH Levels of Concern do not appear to represent a persistent problem.