tomlinson et al (2016) - sediment & biota
TRANSCRIPT
Using multivariate statistics to identify analyte sources in sediments & biota at a
shallow-water, military munitions disposal site off leeward O‘ahu, Hawai‘i
Michael S. Tomlinson Eric H. De Carlo
Geoffrey L. Carton Dennis R. Helsel
Oʻahu, Hawaiʻi
Oʻahu
Hawaiʻi
Maui
Kauaʻi
Molokaʻi
Lānaʻi Kahoʻolawe
Niʻihau
Ordnance Reef Study Area
Diamond Head Honolulu Barbers
Point
Kaʻena Point
Kahuku Point
Makapuʻu Point
Kailua
Kāneʻohe
Māmala Bay
Waiʻanae
What is the problem?
Discarded Military
Munitions or DMM
(conventional)
How extensive is the problem?
The Study
• 141 sediment samples from 4 strata – DMM (discarded military munitions) – CON (control) – NPS (nonpoint source) – WWT (wastewater treatment)
• 286 biota samples from 4 organism types – Limu (seaweed) – He‘e (octopus) – Weke (fish) – Pāpaʻi kua loa (Kona crab)
The Study (continued)
• 5 sediment sampling events (different seasons)
• 4 biota sampling events (different seasons) • Sediments & biota analyzed for elements &
energetics (propellants & explosives) • Multiple nondetects • Multiple detection levels
Nondetects (NDs) are data! (Partial table below is a good format for biogeochemical data)
The “U” data qualifier inserted by data validator is a confirmation of the lab result, i.e., “ND”. Note: “ND” provides NO information without the detection limit (DL)
So what do you do with nondetects (NDs) Ignore
0
½DL
DL
RL
We used some of the multivariate statistical techniques described in
These techniques included:
• Summary statistics using: – Kaplan-Meier – Regression on order statistics
• Kendall’s tau nonparametric correlation • Interval-censored score test (analogous to
generalized Wilcoxon test) • Nonmetric multidimensional scaling (NMDS)
(discussing today) using interval censored data
We used interval-censored data thereby avoiding substitution
We applied nonmetric multidimensional scaling (NMDS) to the interval-censored
data to identify analyte sources
NMDS revealed distinct analyte clusters
Notice how DMM analytes (Mg, Pb, Cu, & Zn & energetics) cluster
And, notice how terrestrial elements cluster
(Typically, a Kruskal’s stress ≤ 0.20 indicates pattern is not random)
And, if you overlay the samples…
Most DMM samples cluster with the DMM analytes
and most samples influenced by terrestrial processes cluster with terrestrial analytes
And, now something for the biologists –
• NMDS of biota (Hawaiian food)
• No strong patterns by strata, but…
Not surprisingly, data clustered by organism
Cu-based hemocyanin & Cu- & Zn-based enzymes (White & Rainbow, 1985)
Only limu exhibited clustering by strata – Why?
• Biology differs from other organisms? • Sessile rather than motile organism
Conclusions There are a number of multivariate statistical routines that
can work with left-censored data with multiple DLs Substitution (e.g., ½DL) is neither necessary nor
recommended Nonmetric multidimensional scaling (NMDS) was able to
identify the sources of most analytes in sediment Overlaying the NMDS results for sediment samples generally
corroborated the analyte results The elements Cu, Zn, Pb & Mg and energetics clustered with
each other and the DMM samples Terrestrial elements clustered with samples from the CON,
NPS, and WWT strata
Conclusions (continued) NMDS plots of biota (typical Hawaiian food), not surprisingly,
clustered by organism Octopus & crabs clustered with each other & with Cu & Zn
o Cu – because the blood of both organisms contain hemocyanin
o Cu & Zn – because of the high concentrations of Cu & Zn enzymes found in both organisms
Only limu kohu or asparagus seaweed (Asparagopsis taxiformis) showed any clustering by strata – Why? o Different biology (plant rather than animal)? o Sessile rather than motile
Multivariate statistical analyses such as NMDS can aid in the identification of analyte sources
Acknowledgments My coauthors
– Eric H. De Carlo (UHM Oceanography) – Geoffrey L. Carton (CALIBRE Systems) – Dennis R. Helsel (Practical Stats)
And a special Mahalo to Mr. Keoki Stender for allowing me to use his marine life photos www.keokiscuba.com/ www.marinelifephotography.com