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

Mahalo nui loa! Questions?

Michael Tomlinson – mtomlins@hawaii.edu