C
COMPARISON OF DDT RESIDUE VALUES OF PLANKTONIC
ORGANISMS AT THE AIR:WATER INTERFACE AND
SUBSURFACE LEVELS OF MONTEREY BAY
Keith G. Baxter
Hopkins Marine Station
of Stanford Universit
running title--

S AT THE AIR:WATER INTERFACE
DDT RESIDUE
Send correspondence to: Hopkins Marine Station,
Pacific Grove, California
C
ABSTRAC
Plankton samplos from the surface and ten meters depth
were collected in Monterey Bay and analyzed for DDT residues.
The results show a trend toward higher concentration at the
air-sea interface. Possible mechanisms of concentration are
discussed, with some consideration given to the ecological
implications.
C
O
4
—-
INTRODUCTTON
Investigation of the unique properties of the air:
water interface with relation to DDT content of its resident
species has generally been neglected in the scientific
literature. There are, however, many important attributes
of this surface layer which indicate that it might play
a significant role in both the concentration and eventual
biological magnification of DDT.
The major difference between the surface layer and
other sub-surface depth zones is its constant contact with
the air. This allows significant imput of DDT residues due
to atmospheric fallout (Cox, a-1971; Risebrough,1968).
ly evidence suggesting this process were studies of:
i) the codistillation of chlorinated hydrocarbons with water
(Sowman, et.al.,1964; ibid.,1969); ii) its detection in air
and rain water (Antommaria, et.al.,1965; Abbot,et.al.,1965:
ibid.,1966; Wheally, et.al.,1966); iii) its appearance in
atmospheric dust originating in Texas and subsequently
deposited in Ohio (Cohen, et.al.,1966). More recent analysis
has shown that an average of 32 X 10 g of DDT residues
were present in dust particles over the Bay of Bengal
(Goldberg and Griffen,1970). Risebrough (1968) has found
1.8 X 10"2 total pesticides/gram of dust in La Jolla, Calif-
ornia. However, these estimates of pesticides should be
considered minimal. The sampling techniques used elimin-
ated particles less than one micron, which may constitute
47
the majority of the adsorptive interface of DDT residues
(Dolaney, ot.al.,1967; Pfister, et.al., 1969; Routh,1971)
The upper layer of the ocean in enriched with potassium,
ammonium, organic nitrogen, and organic particulate matter
(Wilson,1959). The latter aggregates are produced in thin
films by the adsorption of dissolved organic material on
rising bubbles (as those produced by wave action and active
photosynthesis), other subsurface objects, and the sea surface
itsolf (Riley,1963,; ibid.,et.al.,1961; Siegal & Burke, 1965;
Blanchard,196; Sutcliffe, et.al.,1963.) This process allows
for a mechanism of concentration of DDT residues. Seba and
Corcoran (1969) have shown values of chlorinated hydrocarbns
up to 13 X 10"2 g/ml in surface slicks in Biscane, Florida,
mpared to approximately loi
g/ml in the surrounding water.
or
The fact that a small crustacean has been shown to exist
solely on organic aggregates (Baylor & Sutcliffe,1963) suggests
a means of entry of these concentrated pesticides into
various foodchains. DDT residues, being insoluble in water,
have been linked with specific particulates (Pfister, et.al.,
1969; Routh,1971), and hence would be ammendable to this
scheme of input.
The soa surface itself is a natural concentrator of
detrital matter. Most debris is either heavier or lighter
than sea water (Wilson, 1959). The latter rises to the tor
to form an upper layer, while the heavier sinks to benthic
411
sediments. The very fact that an interface is present is
significant, for they account for many of the chemical
roactions ofthe ocean (Horn,1969).
In most regions of the world, the surface layer is
inhabitated by unique neustonic populations (David,a-1971).
which have maximum contact with the interface. These in turn
are preyed upon by a variety of organisms which provide for
a means of both the concentration and transformation of DDT
through various trophic levels. These creatures include
larve, fish, vertically migrating predators, and skimming
birds (Cox,a-1971). The latter, especially, are known to
have very high concentrations of DDT (Tatton & Zicka,1967).
The surface in unique in its chemistry and tendency
to concentrate particulate matter. The chemical properties
of DDT residues associate themselves with particulates.
These two observations, in addition to the contribution to
atmospheric fallout, lead one to believe that surface organisms
leeding on surface populations and injesting and adsorbing
particulates at the air:water interface would show higher
levels of pesticides than organisms exposed to greater depth
zones. This experiment will attempt to show this phenomenum
mpling and analyzing several different groups of organ-
by sa
isms which are found at the surface (designated as neustonic),
These will be compared to similar organisms taken from
subsurface samples (labelled as plankton).
4
ETIIODS
MATERIALS AND!
Samples were collected using a nouston sled towed at the
surface (David,b-1965) and a small zooplankton net
simultaneously towed about ten meters below the surface.
The two nets had openings of similar area (0.016 M- for
the sled, 0.061 M for the plankton net) and similar mesh
(220.5 microns -- sled, 291 microns -- plankton net).
The sled was either towed off to the side of the boat
by moans of a boom, or was trailed far enough aft so that
the wake had little effect. Tows lasted from one-half hour
to one hour. All inshore tows were taken at about the same
time of day. Boat speed was recorded and used in the cal-
culations of relative biomass density. While on board, the
fresh samples were taken from the net and placed in acid-
cleaned (M-6 N HNO,) glasswear, covered with aluminum foil,
and stored on ice.
In the lab, major groups of organisms were seperated
from each other. This usually consisted of seperating
calaniod copepods from ctenaphores (Pleurobrachia bachii)
jatina). This was easily done
and medusea (especially Oct
by the sample through a course (inch mesh) net. The
remaining sample was strained through a ring of phytoplankton
netting, retaining the copepod segment of the sample.
Excess water was removed and wet weights recorded.
Initial preparation of the samples was done by the
method described by Burnett (1971). The only deviation
50
C
M-2
was the addition of 0.05g of acid washed Nuchar Attaclay
to the silica gol (Grade 950,mesh 60-200, dessicant-activated)
microcolumn to remove additional pigments and impurities.
In addition, the samples in tow number 5 were mixed with
metalic mercury to remove sulfur compounds.
Pesticide analysis was accomplished by a Beckman Go-I
gas liquid chromatograph. The solid support for the colunn
was 80-100 mesh Chromosorb W, acid washed and DMOS treated.
It was a mixed bed arrangoment, employing equal parts ol
65 QF 1 and 8% DC 200.
Initialidentification of peaks was based on retention
times as determined by known injected standards. Various
samples throughout the experiment were analyzed by
Pesticidequality hexane and acetonitrile partition
coefficients to supplement retention times.
5
5
RESULT
The rosults of three inshore and two offshore tows
are summarized in Figure 1 and Table 1. Table 2 gives
probability values for the following comparisons:
I. Examination of concentrations of all neustonic copepods
ys. all planktonic copepods yields p values of .10 for DDD
and.20 for DDT.
II. There is a significant difference between inshore
copepods and offshore copepods for DDE (p-.02) and DDT
(p-.001).
—-+
111. Comparison of ctenaphores (Pleurobrachia bachii) in

the neuston and plankton samples showed no signilicant
correlation (pp.10).
IV. A comparison between Euphasia pacifica in the neuston
and plankton samples yields p values y.30.
V. As the relative density of neustonic copepods decreased
in a series of runs, there was a corresponding increase
in the relative density of planktonic calanoid copepods
(Figure 2).
VI. There is an inverse correlation between relative densit
and concentration for individual DDT residues and sums in neustonic
calanoid copepods (Figures 3,1, & 5).
DISCUSSION
A comparison of the results with other values in the
literature is difficult because of the scarsity of the latter.
Woodwell etal. (1967) did find 10 ppb total DDT residues
in plankton from a polluted esturary on the East Coast.
Cox (a-1971) found 30 ppb in large pooled copepod samples
in Monterey Bay. (Converted to wet weight concentrations
as shown by Martin, 1971). These values compare with the
range of 10-37 ppb for individual samples in the three
inshore tows.
The differences between the neustonic and planktonic
populations were not as great as expected. This is undoubt-
edly due to sampling techniques which did not allow collection
of those organisms that are uniquely and consistently
found at the air :water interface. Instead of true "neustonic"
residenis, the organisms consisted primarily of vertically
migrating calanoid copepods. However, the fact that a trend
towards higher values (especially with DDT) was found in
the upper layers is encouraging. Here one must conclude
that the differences in residue values is attributable to
exposure to the concentrating capacity of the surface.
Marian (1971) found similar results when analyzing Hermissinda
ssicornis collected from floats and wharf pilings at
O.3-7.0 meters. The organisms at the surface had residue
values of 2.3 X that of the mean of the piling population.
The significant difference between inshore and offshore
53
copopods may be duo to the location of the sewer outfalls,
other effulonts, and the marina inshore relative to off-
shore (Figure 1). Large differences in DDT values further
substantiate this rolationship, since the organisms immediate
responso to the onvironment would be reflected in these values.
In addition, the largest DDT values were found in the
tow nearest the two outfalls, with levels decreasing as
a function of distance from the effulents. The same correlation
with distance was found in Tow 1 away from the mouth ofthe
marina. Swarbrick (1971) found a similar falloff in the
same transect in DDT analysis of Pagurus samuelis.
The ctenaphores sampled from both dopths were showm
to be from the same population. Because of their sensitivity
to sunlight and weather conditions (Hyman,1910,p662, they
are in continual movement in the water column. This is
substantiated by observation of changing densities throughout
the five tows. This consistent fluctuation may eliminate
the possibility for effective concentration. In addition,
the high S/V ratio and high water content (95-97%) minimizies
the amount of adsorptive and assimilative surfaces.
i
Similarity of the neustonic and planktonic E.
oifica
may be a result of the strength of migration of the population.

The 0030-0230 runs of Tow 5 resulted in 99% E. pacilica
at both the surface and 10 meters. The 0600-0700 netted
only scattered euphausids in both samples. Accompaning
these movements is undoubtedly a large amount of mixing,
which would tend to mask differences in concentration levels.
Examination of Figure 2 shows an inverse relationship
between the rolative densities of the neustonic and planktonic
copepod populations. This is what one might expect from
a partly migrating species. That their migration is not
total is shown by their presence in different densities in
all tows at all times of the day. It is likely that some
organisms seldom leave the surface, while others spend most
of their time at subsurface depths. This is reasonable,
since in any migrating population, there will be member:
which are skowed to either side of the mean movement of
the population.
There is some evidence that this distribution may be
physiologically determined. Marshall and Orr (1955)
have noted that copepod females migrate to the surface to
lay their eggs. Moreover, females tend to migrate more
regularly than males. Bainbridge (1952) noted two distinct
layers of copepods in a summer bloom: a dense population
in the top 30 cm, and a subsurface layer in which the
copepods were more sparsley distributed.
That the relative density may be an indication of
residence time of the members in any one layer is shown
by the inverse relationship between concentration and
density in neustonic copepods (Figures345). As the relative
density of the neuston layer is decreased by downward
movement, the relative concentration of DDT residues is
increased, since the remaining animals will have been
exposed to the surface for a longer period.
63
Supplementing the residence time with respect to
concontration are the proporties of injestion and adsorption
at the surface. Both of these properties are taking
place simultanoously (Cox,c-1971). As density increases,
loss pollutants are available/organism, and the concentration
values drop per unit weight. The fact that Cox (b-1971)
showed similar slopes for the density vs. concentration
of organic particulate matter may indicate that while at the
surface, adsorption contributes significantly to the total
DDT levels.
A third contribution to the inverse density:concentration
relationship is the location of the various tows. Location
of effluents could have completely determined the concentration
values irrespective of density. However, Lopez (1971) found
no correlation between values for heavy metals as a function
of location. He did demonstrate the same relationship for
y and concentration. This indicates that something
dens
more than location is responsible for this phenomenum.
That the planktonic samples did not exhibit this relation-
ship is presumably due to scattering after leaving the two
dimensional confinements of the surface.
56
C
CONCLUSTO
The rosults presented here favorthe hypothesis that
DDT residues are concentrated at the air:water interface
relative to the subsurface zones. Problems encountered
in sampling, analysis, and population structure of the
study orcanisms tended to mask these dil
ferences.
The implications from this surface concentrating effect
may be significant. Any organism that is subjected to this
region will be brought into contact with higher concentrations
of DDT residues than its usual medium. Therefore surface
feeding larve, filter feeders, and skimming birds may be
receiving relatively high levels of pesticides in their food.
By this method an important means of DDT input to both marine
and terrestrial food webs is established.
O
5
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Acknowledgements
I would like to thank the entire staff of Hopkins Marine
Station for their valuable assistance and encouragement,
especially Dr. Malvern Gilmartin, Mr. Phillip Murphy, Mr.
Robin Burnett, and the crew of the R/V Proteus.
This would was made possible by grant GY 8950 of the
Undergraduate Research Program of the National Science
Foundation.
Literature Cited
Abbot, R.B., (1965), Organochlorine Pesticides in the
Atmospheric Environment, Mature, 208:1317.
, et.al., (1966), Organochlorine pesticides in the
mosphere, Nature, 211:259.
Antommaria, P., et.al., (1965), Airborn Particulates in
Pittsburg: Association with p,p' DDT, Science,
150:1176.
Bainbridge, (1952), Underwater Observations on the Swimming
of a Marine Zooplankton, J. Mar. Bio. Ass. U.K., 31:
107.
Baylor, E.R., & W.H. Sutcliffe, (1963), Dissolved Organic
Matter in Sea Water as a Source of Particulate Food,
J5.
mnol. and Oceanog., 8:369.
Li
Blanchard, D.C., (1964), Sea to Air Transport of Surface
Active Material, Science, 1146:396.
Bowman, M.C., et.al., (1964), Chlorinated Insecticides
Fate in Aqueous Suspensions Containing Mosquito
Larve, Science, 116:1180.
Burnett, R., (1971), DDT residues: Their Distribution Along
Coastal California, Science, submitted.
J.H., & C. Pinkerton, (1966), Widespread Translocation
Cohen,
of Pesticides by Air: Transport and Rainout, p 163,
icides in the
ic Pes
in R.F. Gould (ed.), 0
nvironment, American Chemical Society, Washington
5
D.C., 309 pp.
Cox, J.L., (a-1971), DDT Residues in Coastal Marine Phyto¬
plankton and Their Transfer in Pelagic Food Chains,
Ph. D. Thesis, Stanford University.
. (5-1971), DDT Residues in Sea Water and Particulate
Matter in the California Current System, Fish. Bull.
submitted.
(c-1971), Uptake, Assimilation, and Loss of DDI
Residues by E. pacifica, a Euphasid shrimp,
Fish.
Bull., submitted.
P.M., (a-1965), The Surface Fauna of the Ocean, Endeavour
David,
21:95.
. (b-1965), The Neuston Net, a Device for Sampling
the Surface Fauna of the Ocean, J. Mar. Bio. Assoc.,
U.K.,15:313.
A.C., et.al. (1967), Airborn Dust Collected at Barbados,
Delan
Geo
m. Cosmochim. Acta., 31:885.

riffen, (1970), The Sediments of the Northern
Goldberg & (
Sea Res., 17:513.
Indian Ocean, Dee
y, John Wiley & Sons,
R.T., (1969), Marine Chemistr
Horne,
New York, 566 pp.
The Invertebrates: Protozoa throu?
man,
L.H., (1940),
tenophora, MoGraw Hill, New York, 726 pp.
Lopez, G. (1971), Analysis of Heavy Metal Concentrations at
the Air: Water Interface and Subsurface Waters of
Monterey Bay, unpublished.
rine
Biology of aM
Marshall, S.M. and A.P. Orr (1955), The!
60
Copepod: Calanus fenmarchicus (Gunnerus), Oliver and
Boyd, London, 188 pp.
Marian, R., (1971), Assimilation and Transfer of DDT Residues
in a Hydroid-Nudibranch-Tetribranch Food Chain, un-
published.
Martin, J.H., (1970), The Possible Transport of Trace Metals
Via Molting Copepod Exoskeletons, Limnol. Oceanog.,
15:756.
Pfister, R.M., et.al., (1969), Microparticulates:Isolation
From Water and Identification of Associated Chlorinated
Pesticides, Science, 166:878.
Riley
G.A., (1963), Organic Aggregates in Sea Water and the
Dynamics of Their Formation, Limnol Oceanog., 6:372.
, et.al., (1964), Organic Aggregates in Tropical &
Subtropical Surface Waters of the North Atlantic Ocean,
imnol. Oceanog, 9:516.
Risebrough, (1968), Pesticides: Transatlantic Movement in the
Northeast Trades, Scjence 159:.
Seba & Corcoran, (1969), Surface Slicks as Concentrators
of Pesticides in the Marine Environment, Pest. Monit.
J., 3:190.
Siegal, A, & B. Burke (1965), Sorption Studies of Cations
on Bubble Produced Organic Aggregates in Sea Water,
Deep Sea Res., 12:789.

Sutclille, W.H., et.al., (1963), Sea Surface Chemistry and
Langmuir Circulation, Deep Sea Res. 10:233.
Gwarbrick, S., (1971), DDT Residues in the Marine Intertidal
61
C
s in California Wators,
Hormit Crab P
gurus sane
unpublished.
Tatton, J O'G., & J.H. Ruzicka, (1967), Organochlorine
o 215:316.
Posticides in Anarctica, Matu
Wheatley, G.A., & J.A. Hardman, (1965), Indication of tho
Presence of Organochlorine Insecticides in Rainwater
in Central England, Nature, 207:166.
Wilson, A.T., (1959), Surface of the Ocean as a Source of
Air Born Nitrogenous Material and Other Plant
Nutrients, Nature, 164:99.
Woodwell, et.al., (1967), DDT Residues in an East Coast
Estuary:A Case of Biological Concentration of a
Persistent Insecticide, Science, 156:871.
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Table jl - Mean values obtained for p,p' DDE, p,p'DDD,
us of all
p.p' DDT, andthe means of the si
three residues in samples collected during
five tows in Monterey Bay. The standard error
was computed as follows
: SE - (P
N-1
TABLE 1
SAMPLS
POPULATTON
DD
Nouston copenods
.611.7
Plankton copepods
6.111.3
Inshore N.copepods
6.1+1.8
Inshore P. copepods
6.211.5
Inshore copepods

6.311.1
Offshore copepods
2.2+0.1
Neuston E.paci
3.110.5
ia

Plank
aEpaifice
5.312.8
All E.paci
1.311.1
Neu. ctenaphores
O.6+0.3
—
Plan. ctenaphores
O.5+0.2
All copepods
16
5.8-1.0

All ctenaphores
O.5+0.1
09
CONCENTRATIONg/1
Total residues
DDT
8.9+2.1
3.310.8
17.912.9
13.212.9
5.6-1.1
1.9-0.1
10.012.1
20.041.3
3.6-0.9
6.211.
11.513.0
2.1+0.1
6.111.3
2.840.5
17.212.6
1.1+0.2
1.1+0.7
2.211.1
8.1-0.8
2.712.1
2.0+1.7
2.911.9
9.710.8
1.510.2
——

6.9+0.7
1.8+0.6
2.8+1.
O.6+0.3
O.7-0.2
1.6-1.3

O.5+0.3
0.340.1
1.3+0.3
15.612.5
7.311.3
1.1+0.8
1.1+O.8
O.6+0.5
O.1+0.2
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Table 2 - The probability that the two populations compared
are from the same general population, as computed
by the "t" test, ie.
t- 2-X.
—
2
61
n- + n-
6
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POPULATTONS COMPARE
All neuston copopods
All plankton copepods
Inshore N. copepods
Inshore P. copepods

Neuston E. pac
ica

Plankton E.
ie
Inshore copepods
Offshore copepods
Neuston ctenaphores
Plankton ctenaphores
TABLE 12
DDE
.50
.90
.50
.02
.90
DDI
.10
.20
.80
.60
.80
DDT
.20
.10
.90
.001
.10
66
2SIDU
TAL REIDOD
.10
.30
.30
.O1
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Figure 71 - Species composition and towing conditions for
the 11 runs in Monterey Bay. Abundance scale
is: +++ most abundant; ++ frequently observed;
seldom observed. Circles indicate sewer
effluents, corresponding numbers show treatment
(ie. primary, secondary, etc.)
San Lorenzo
68
FIGURE T
River
SANTA CRUZ



Tow j-3 runs
1./29/7
0715-0915
Calm-overcast
Calano oe +++
+ ++
P. bachi
Tow 2-1
run
o8oo-0830
5/61
Overcast,cold,windy
Plankton: (10-15 M)
Neuston: Calanoid oppods +++
Calnid oed +++
surface)P. bachii ++
bachii ++
Iarval shrimp ++
larval shrimp +
larval crab (zoa) +
Elkhern
larval crab +
Leptomedusae +
Gammarid amphipod +

Beroe forskali
ish +
Slough
larval
uphausid +
To
3-3 runs
5/1
0830-1030
Calm,overcast.
Plankton: Calanoid coper
Heuston:alnoid oepod ++
P. bachii ++
+ ++
bace
larval crab (megalops)

amphapods +
Tow -3 run
Salinas River
5/11/7
o900-1300
par
ly cloudy,choppy
Plankton:Calanoid copepods +++
euston:alanoid opepods +++
perid amphapods +
honophores -
larval fish+
Hyperid amphapods +
Euphausid
bachii
lomopterus+
3runs
Tor

2
10w1
0030-02
TOW3
Windy,choppy,cold
Sron
+ ++
Neuston: E. paifica
la:
rval crab (megalopa
sh (small)
MONTEREY
Siphonophores +


Medusae +

Calanoid copepod
Tow 15 (con);0600-0700
H.paifica
+ +++
Windy,choppy,cold
Plankton:
euston:Calanoid copepods ++
P. bachi.
(10 M)
crab larve (megalops
Calanoid copopods
ica
squid (juvenile)
d amphapods+

Pla
ton-10 M:
tarmel Rivef Calanoid copepods:

honophores +
Medusae ++
P. bachi
TOW 5
larval fish +
C
Figure j2 - Neuston copepod relative density vs. plankton
copepod relative density for tows j1,3,811.
6
-0.0
-10.0
-11.C

9.O
FIGURE II
o-701
o -101 2
X -101 4
-7.0
-8.0
log plankton density (g/m3)

70
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Figure 3 - A graph of the concentrations of the means of
neustonic DDE, DDD, and DDT residues vs. relative
density as collected on inshore tows il & 42.
Wach point represents seven pooled samoles,
c

58+
38
-104/
DDT RESIDUES
NEUSTONIC COPEPODS
LOG DENSITY - /
9.37
FIGURE 3
72
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Figure 31 - A graph of neustonic DDT residue concentrations
ys, relative density as collected on inshore
tows jl & 13. Each point represents two pooled
ples.
10.4
O.O
8.6
7.2
54
40-
-10.47
DDT
NEUSTON COPEPODS
-9.77
10G DENSITY - 6/M
FIGURE 4
-9.37
C
74
O
Figure 75 - A graph of neustonic DDD concentrations ys.
relative density as collected on inshore tows
1 8. 13.
Each point represents two pooled
samples.
0
147


43
-10
082
078
-10.47
DOD
NEUSTON COPEPODS
9.77
LOG DENSITY /m
-9.37
FIGURE 5
76