The use of the terrestrial amphipod arcitalitrus dorrieni (Crustacea; Amphipoda; Talitridae) as a potential biomonitor of ambient zinc and copper availabilities in leaf-litter

Chemosphere, Voi.24, No.10, pp 1505-1522, 1992 Printed in Great Britain

THE USE OF THE TERRESTRIAL AMPHIPODA;

AMPHIPOD

0045-6535/92 $5.00 + 0.00 Pergamon Press Ltd.

ARCITALITRUS

TALITRIDAE)

AS A POTENTIAL

COPPER

AVAILABILITIES

Jason

M.

DORRIENI

BIOMONITOR IN

(CRUBTACEA~

OFAMBXENTZINCKND

LEAF-LITTER

Weeks I

School of Biological Sciences Queen Mary & W e s t f i e l d College University of London Mile End Road London, E1 4NS U.K. iInstitute of Biology, Odense University, Campusvej-55, DK-5230 Odense M Denmark

ABSTRACT

The mode of metal accumulation

employed by the t e r r e s t r i a l t a l i t r i d

amphipod A r c i t a l i t r u s dorrieni (Hunt) feeding on leaf litter v a r i o u s ly e n r i c h e d

w i t h the e s s e n t i a l

established

in the laboratory.

metals

and zinc h a v e b e e n

Body c o n c e n t r a t i o n s

were found to increase over time dietary metal concentrations.

copper

of b o t h m e t a l s

c o r r e l a t i n g w i t h the i n c r e a s i n g

Field trials to assess the p o t e n t i a l

use of this a m p h i p o d as a terrestrial b i o m o n i t o r for a m b i e n t copper and zinc availabilities

in leaf litter are described.

The results

indicate a potential b i o m o n i t o r i n g c a p a c i t y for zinc (and p o s s i b l y for copper also).

The presently

restricted

distribution

of this

species, however, limits its b i o m o n i t o r i n g p o t e n t i a l to m e t a l l i f e r o u s areas of S.W. England, but reflects u n k n o w n p o t e n t i a l in its native Australia. INTRODUCTION The use of aquatic organisms to m o n i t o r trace metal b i o a v a i l a b i l i t i e s 1505

1506

is well established centrations

(see Phillips, 1980 for review); the metal con-

in bodies of net a c c u m u l a t o r s

function of the amounts of bioavailable

b e i n g by d e f i n i t i o n

metal

in the environment

integrated over time. Prerequisite characteristics have been listed by Bryan e_~t al.

a

of biomonitors

(1980, 1985) and Phillips

(1980).

The recent use of littoral talitrid amphipod crustaceans as convenient biomonitors for the essential metals copper and zinc (Rainbow et al~, 1989; Moore e_~tal., 1991) has already highlighted several areas of copper and zinc enrichment in coastal locations conventionally regarded as being uncontaminated. The similar use of isopod crustaceans as

indicators of anthropogen-

ic or natural "hotspots" of metal pollution in terrestrial habitats is similarly well documented (Wieser e_ttal., 1976; Coughtrey et al., 1977; Martin & Coughtrey, 1982; Hopkin e t al., 1986). To the author's knowledge no attempt has been made to use t e r r e s t r i a l (landhoppers)

amphipods

in similar circumstances. The introduced terrestrial

talitrid Ar~italitrus dorrieni has been recorded now from more than 90 localities in Britain and Ireland (Harding & Sutton, 1988), mostly in the west and south of Cornwall and along the southern coast of Devon and Dorset. The metals copper and zinc are Grey List s u b s t a n c e s

within the

definition of the Paris Convention and European Community "Dangerous Substances" Directive. Although both these metals may become toxic in excess, they are essential trace elements required, for example, for the metabolic functioning of proteins

(e.g. Cu for the respiratory

pigment haemocyanin and Zn for the enzyme carbonic anhydrase). This study therefore investigates the suitability of Arcitalit~us dorrieni as a biomonitor for copper and zinc. Laboratory studies were designed to verify that this talitrid is a net accumulator of metals assimilated from food (cf. supralittoral talitrids,

Weeks,

1990; Weeks &

1507

Rainbow, 1990, W e e k s & Rainbow, 1991). Moreover, to assess the relative p o t e n t i a l

and m e r i t s of u s i n g A_~. d o r r i e n i as a b i o m o n i t o r ,

a

c o m p a r a t i v e field study was u n d e r t a k e n of c o p p e r and zinc c o n c e n t r a tions

in A__~.d o r r i e n i c o l l e c t e d from six l o c a l i t i e s

MATERIALS

Accumulation

Groups

and zinc

of i0 A r c i t a l i t r u s

Plymouth, ments

of c o p p e r

Devon,

U.K.

No d i s c r i m i n a t i o n acid-washed

Petri

AND METHODS

from a l d e r

dorrieni

(see T a b l e

such that each group between dishes

filter paper moistened

dishes

polythene

was

"leaf s h a p e s "

regime of 16hL:

i),

were

(suitably

humidified

by

for

experi-

of s i m i l a r

Amphipods

were

with

size.

held

in

a strip

of

water held by capil-

Survivorship

improved

the

cut f r o m a c i d - w a s h e d

Animals

from B u d s h e a d Wood,

amphipods

sexes was made.

(Alnus ulutinosa)

selected

in d o u b l e - d i s t i l l e d

markedly

a n i m a l s c o u l d nestle.

leaves

collected

contained

larity to the inside of the lid). Petri

in the U.K..

of A. d o r r i e n i

provision

of

in

black

sheets under which

w e r e h e l d at 15"C w i t h a l i g h t i n g

8hD.

TABLE i. D e t a i l s of the c o l l e c t i o n s of ~ ~ sites in SW England, SE E n g l a n d and the Island of C o l o n s a y Hebrides), Scotland.

from (Inner

Collection details

Site

Date

T r e l i s s i c k Gardens, C o r n w a l l Carbis bay, C o r n w a l l St Euny, Redruth, C o r n w a l l B u d s h e a d wood, Plymouth, D e v o n Kew Royal B o t a n i c gdns, L o n d o n Colonsay, S c o t l a n d

1/7/89 2/9/89 2/9/89 2/9/89

22/2/89 24/1/88

O.S. grid reference SW SW SW SX SU NR

839395 528390 692414 426599 188774 396972

Each g r o u p of a m p h i p o d s was a l l o w e d to feed for 21 days

on discs

1508

of a l d e r leaf

(Alnus glutinosa)

using a stainless distilled

steel

water)

concentrations. had r e s u l t e d

(cut so as to a v o i d the mid-rib,

cork-borer previously

containing

The metal

one

concentrations

from 24h e x p o s u r e

tilled water,

of a n u m b e r

at 1 5 ° C

rinsed

in d o u b l e -

of c o p p e r

in the

or

zinc

a l d e r leaf discs

in 50 cm 3 of d o u b l e - d i s -

either w i t h o u t a d d i t i o n of metal

(control exposure)

or w i t h one of a logarithmic series of d i s s o l v e d metal c o n c e n t r a tions

(prepared

Analar grade

from a s t a n d a r d

(BDH Ltd)).

concentrations 476,

1372,

2584,

case

of c o p p e r :

33.3

3800 ~g Cu g-i dry wt.

added

chloride

salt,

In the case of zinc the m e a s u r e d

metal

Petri

77.8

(control),

3250 or 4967 ~g Zn g-i dry wt; (control),

112,

248,

556,

1138,

and

106,

in the

1725,

or

A f t e r e x p o s u r e the a l d e r leaf d i s c s were

d r y a n d two w e i g h e d

to the

of the

in the alder leaf discs were:

261,

blotted

solution

dishes.

discs Leaf

for e a c h discs

were

concentration changed

were

every

2-3

days as appropriate. A f t e r 21 days feeding, individual a m p h i p o d s w e r e w a s h e d in d o u b l e d i s t i l l e d water, dried to c o n s t a n t w e i g h t at 60°C, d i g e s t e d in A r i s tar conc. HNO 3 (BDH Ltd., U.K.)

at 100°C and m a d e up to v o l u m e

(2

cm 3) w i t h d o u b l e - d i s t i l l e d water. Digests were s u b s e q u e n t l y a n a l y s e d for total c o p p e r and zinc by flame atomic a b s o r p t i o n s p e c t r o p h o t o m e try (background c o r r e c t i o n for zinc) on an IL-157 a t o m i c a b s o r p t i o n spectrophotometer.

Leaf discs were

s i m i l a r l y dried,

digested

and

a n a l y s e d for total copper and zinc.

Field survey

A r c i t a l i t r u s dorrieni w e r e c o l l e c t e d from the v a r i o u s

s i t e s listed

in T a b l e 1 - e i t h e r individually by hand, or by m a s s c o l l e c t i o n s of leaf litter. A m p h i p o d s w e r e r e t u r n e d to the l a b o r a t o r y a l i v e w i t h i n

1509

b 1000

1000

?= |

|

6 c

o

~jl

100

0 cJ

j~

u ,u

p-

o F10

100

, 10

.

.

.

.

.

.

.

.

'

100

Food copper

.

.

.

.

.

.

'

1000

concentration

.

.

.

.

.

r

I

104

10

pg g-1

104

1000

100

F o o d zinc c o n c e n t r a t i o n

Pg g - i

Fig. i. M e a n total (a) copper and (b) zinc c o n c e n t r a t i o n s (~g g-i ± 1 SD) of Arcitalitrus dorrieni fed for 21 days on a range of v a r i o u s l y enriched dietary litter copper or zinc concentrations. E q u a t i o n s of the r e g r e s s i o n l i n e s f i t t e d b y l e a s t s q u a r e s a r e (a) l o g y = 0.302(logx) + 1.39, R = 0.96 (P<0.01) and (b) log y= 0.247(iog X) + 1.79, R = 0.97 (P<0.01). Line (b) excludes the final data point (see text).

i

~,

- • 12-

20

'o~ 10 -

~

u u

m

o

6

q 0

o 0

1000

2000

3000

F o o d c o p p e r c o n c e n t r a t i o n (~Jg g - l }

4000

0

1000

2000

3000

F o o d zinc c o n c e n t r a t i o n (pg 3 -I}

Fig. 2. M e a n rates of (a) copper and (b) zinc net accumulation (~g g-~ ± 1 SD) (measured as the net increase over controls) by A r c i t e l i trus dorrieni, fed on a range of variously enriched litter copper or zinc concentrations (~g g-±) for 21 days. Equations of regression lines fitted by least squares are (a) y= 0.002(x) + 0.520, R=0.92 (P<0.Ol) and (b) y= O.003(x) + 1.99, R=0.95 (P
4000

1510

24h of collection in plastic bags containing some of the substratum on which they were feeding.

It was decided not to allow time for

depuration of the guts of individual amphipods since available data suggest that gut contents are not significant variables in the assessment of body burdens of copper and zinc in this talitrid (Rainbow & Moore, 1986; Moore & Rainbow, 1987; Weeks, 1990). Collections were made in February, July and September,

1989, and additional material

was collected from the Island of Colonsay, Inner Hebrides (courtesy of J. & P. Clarke)

in January,

1988.

Landhoppers were sorted and individually washed in double-distilled water, dried, digested

and made up to volume. Digests were analysed

for total copper and zinc

as described previously. Leaf litter from

each respective site was similarly dried, digested and analysed for total copper and zinc. Logarithmic transformation of the data enabled statistical investigation by parametric techniques

including regression analysis and

analysis of variance (ANOVA) according to Sokal & Rohlf (1981), both Drlori

testing for differences amongst all means, and a Dosteriori

testing for differences between selected groups was undertaken. All metal concentrations

are quoted as ~g g-i on a dry weight basis,

unless otherwise stated.

RESULTS copper accumulation by Arcitalitrus dorrieni Fig.

la shows the mean concentrations

of copper in e x p e r i m e n t a l

amphipods allowed to feed on alder leaf discs previously exposed to a range of elevated copper concentrations. The mean body copper concentration of control amphipods

(85.5 #g g-l; i SD 16.6, no8) did not

differ significantly (P>0.05) from the mean copper concentrations of the initial amphipods

(82.8 ~g g-l; i SD 12.0, no10). Analysis of

1511

these data by ANOVA showed that the amphipods feeding on elevated dietary copper concentrations had mean body copper concentrations significantly raised above that of control amphipods (P<0.01). There was a s i g n i f i c a n t c o r r e l a t i o n

(P<0.01)

b e t w e e n m e a n b o d y copper

concentrations and food copper concentrations at all food concentrations above the control. There was no significant change (P>O.05) in mean body zinc concentration of amphipods with exposure to elevated dietary copper concentration. Thus there is a significant increase in the whole body copper concentration of A_~.dorrieni with increasing exposure to elevated dietary copper concentrations.

zinc accumulation by Arcitalitrus dorrieni Fig.

ib s h o w s the m e a n c o n c e n t r a t i o n s

of zinc

in e x p e r i m e n t a l

amphipods allowed to feed on alder leaf discs previously exposed to a range of zinc concentrations. The mean body zinc concentration of control amphipods differ s i g n i f i c a n t l y

(174 .g g-l;

(P>0.05)

of i n i t i a l a m p h i p o d s

i SD 55.0;

no8)

did not

from the m e a n zinc concentrations

(199 ~g g-l;

1 SD 39.8;

n=10).

A N O V A re-

vealed that the amphipods feeding on e l e v a t e d d i e t a r y zinc concentrations raised

had

above

mean

that

body

zinc

of c o n t r o l

concentrations

amphipods

significantly

(P<0.01).

There

was

a

significant regression (P<0.01) between mean body zinc concentration and d i e t a r y

zinc c o n c e n t r a t i o n at all

food c o n c e n t r a t i o n s

above the control. The apparently reduced mean total zinc concentration of amphipods exposed to the highest food zinc concentration is p o s s i b l y due to a r e d u c t i o n the h i g h e r

increase

in food metal

in feeding a s s o c i a t e d w i t h

concentration

(Weeks,

1990).

Consequently, this datum point was omitted from the final regression plot.

There

was

no s i g n i f i c a n t

change

(P>0.05)

in b o d y

1512

copper

concentration

of amphipods

with

exposure

to elevated

zinc

concentrations. Thus there is a significant increase in the whole body zinc concentrations of A. dorrieni with exposure to e l e v a t e d dietary zinc concentrations.

Rates of a c c u m u l a t i o n of copper and zinc from food by A_~. d o r r i e n i

Copper A significant

regression

(P<0.01)

could be p l o t t e d

the mean copper a c c u m u l a t i o n rate by A r c i t a l i t r u s dietary

(Fig.

2a)

for

dorrieni against

copper concentration.

The mean copper a c c u m u l a t i o n rate of A_~.dorrieni, as c a l c u l a t e d from the r e g r e s s i o n line in Fig. 2a, for an a m p h i p o d feeding on alder leaf litter from an u n p o l l u t e d location (7.7 ~g Cu g-l; 1 SD 6.7) is 0.539 ~g g-i

day-l.

This

rate

of c o p p e r

accumulation

for A.

dorrieni

amounts to c_~a0.65% of the total body c o p p e r per day. During 21 days feeding at a constant rate the amount of copper a c c u m u l a t e d

in the

body would therefore be 13.6% of the initial total body c o p p e r (82.8 ~g Cu g-l),

i.e.

11.3 ~g Cu g-l.

Zinc A significant

regression

could also be p l o t t e d

of the mean zinc a c c u m u l a t i o n

(P<0.01)

rate of A. dorrieni

(Fig.

2b)

against dietary

zinc concentration. The mean zinc a c c u m u l a t i o n rate of A_= dorrieni,

as c a l c u l a t e d from

the regression line in Fig. 2b, for an a m p h i p o d feeding on alder leaf litter from the same u n p o l l u t e d 2.21 ~g g-i day-l.

site (70.3 ~g Zn g-l; i SD 12.3) is

This rate of zinc a c c u m u l a t i o n

for A__~.dorrieni

amounts to ca 1.11% of the total body zinc per day. During 21 days

1513

a

15o

d

b

L

400 "

i" \~'

300-

\ "~

== ~ ~"

• % ","

o

•

•

• • •

~

100-

i, /i \

.

•

...

•

0 1

2

3

4

5

2

6

4

6

8

10

12

Dry wt. (mg)

Dry w t (mg)

Fig. 3 . Plots of (a) copper and (b) zinc concentrations (~g g-l) against dry weight (mg) for two samples of Arcitalitrus dorrieni collected from Budshead wood, Plymouth. T h e ~ i n e s drawn are the bestfit lines of the power relationship (y= axe).

o~

loo •

•:

, • . ,

=~

sell

.:

,oo

8

~

1o

Dry wt. (mg)

Dry wt. (rag)

Fig. 4.. Plots. of lOgl0 metal concentration (~g g-l) (a) copper and (b) zlnc agalnst lOgl0 dry weights (mg) of Arcitalitrus dorrieni collected from Budshead wood, Plymouth.

151~

feeding at a constant rate,

the amount of zinc accumulated would

therefore be 23.3% of the initial body zinc

(199 ~g Zn g-l),

i.e.

46.4 ~g Zn g-1.

Field survey

Rainbow

& Moore

(1986)

metal concentration concentration, power function,

have

reported

in amphipods,

effects

of b o d y

the relationship

(y) and body dry weight

size

on

between metal

(x) being modelled by the

y=ax b. Animals of less than 2 mg body dry weight

exhibited elevated metal concentrations

(probably as a feature of

the relative increase in surface area available for adsorption in small animals).

To minimise size effects it was intended wherever

possible to analyse only large

(>2 mg)

individuals,

the inherent small size of Arcitalitrus dorrieni, able in some instances to include values for small pods

in o r d e r

to m a i n t a i n

a statistically

but,

due to

it was unavoid(< 2mg) amphi-

satisfactory

sample

size. As such it was essential to account for any significant relationships of metal concentrations against body weight.

Fig. 3a shows a

plot of copper concentration against dry weight for A__~.d o r ~ e n ~

from

Budshead Wood, Plymouth. The data revealed a clear size effect, with small amphipods having

much raised metal concentrations. Similarly,

Fig. 3b shows a plot of zinc concentrations against dry weight for a different sample of the same

population. Clearly it is meaningless

to compare mean metal concentrations between amphipods without allowance for this size effect. Data for individual dry weights and metal concentrations were therefore transformed. The step of taking logarithms (logl0) transforms the power equation y=ax b into the straight line log y = log a + blogx. The transformed data are then amenable to

1515

t r e a t m e n t by p a r a m e t r i c statistics,

and the d e r i v e d linear r e g r e s -

sions can be c o m p a r e d by A n a l y s i s of C o v a r i a n c e

(ANCOVA)

(Sokal &

Rohlf, 1981). Figures 4a and 4b show the same data as Figs 3a and 3b but now log transformed. There is now no s i g n i f i c a n t (P>0.05) r e g r e s sion a g a i n s t b o d y dry weight for either metal,

in this p a r t i c u l a r

example.

TABLE 2. A r c i t a l i t r u s ~orrieni: the n u m b e r (n) and dry w e i g h t s (mg, mean and range) of a m p h i p o d s a n a l y s e d for (a) copper and (b) zinc c o n c e n t r a t i o n s with d e t a i l s of the r e l a t i o n s h i p log y = l o g a+blogx, where y is the metal c o n c e n t r a t i o n (~g g-l), and x is the dry w e i g h t (mg) and ~ and ~ (the r e g r e s s i o n c o e f f i c i e n t ) are constants. SIG. REG. is the s i g n i f i c a n c e of the r e g r e s s i o n ; ns not significant. Dry W e i g h t Site

(mg)

(min,max)

Double log r e g r e s s i o n

n

Mean

Range

b

SIG REG

log a

i0 15 i0 i0 9 i0

1.27 3.95 3.81 1.27 2.42 3.80

0.9 1.8 0.7 0.9 0.5 5.5

1.9 6.8 13.7 1.9 6.1 6.1

-0.123 -0.376 -0.342 -1.240 0.029 0.029

ns ns P<0.05 ns ns ns

1.374 0.964 1.002 -1.664 1.899 1.843

I0 15 l0 i0 9 i0

1.27 3.95 3.81 1.27 2.42 3.80

0.9 1.8 0.7 0.9 0.5 5.5

1.9 6.8 13.7 1.9 6.1 6.1

-0.071 0.280 -0.255 -0.174 -0.392 -0.308

ns ns P=0.05 ns ns ns

2.087 2.218 1.392 2.075 1.302 1.389

(a) C o p p e r Trelissick Carbis Bay St. E u n y Budshead Kew G a r d e n s Colonsay (b) Zinc Trelissick Carbis Bay St. Euny Budshead Kew G a r d e n s Colonsay

Copper

Table 2a s u m m a r i z e s the i n f o r m a t i o n on the double log r e g r e s s i o n s of body c o p p e r c o n c e n t r a t i o n against dry w e i g h t for A. dorrieni. For one site, St Euny,

there was a s i g n i f i c a n t r e g r e s s i o n

in s p i t e of the

t r a n s f o r m a t i o n of the data. A N C O V A allows the c o m p a r i s o n of c o p p e r c o n c e n t r a t i o n s in a m p h i p o d s from d i f f e r e n t locations, by c o m p a r i n g the e l e v a t i o n of r e s p e c t i v e r e g r e s s i o n lines.

]516

A c o n v e n i e n t m e t h o d for p r e s e n t i n g such c o m p a r a t i v e data is to use each r e g r e s s i o n e q u a t i o n to estimate the c o p p e r c o n c e n t r a t i o n of an amphipod

of s t a n d a r d body weight.

Table

copper c o n c e n t r a t i o n of landhoppers confidence

limits

antilogarithms

(asymmetrical

3 presents

the e s t i m a t e d

of 5 mg dry w e i g h t w i t h

a b o u t the e s t i m a t e

of the t r a n s f o r m e d data).

Table

95 %

after taking

3 also p r o v i d e s

a

summary of the results of i n t r a s p e c i f i c c o m p a r i s o n s by ANCOVA. The copper c o n c e n t r a t i o n s of amphipods from sites s h a r i n g a c o m m o n letter in the A N C O V A do not d i f f e r significantly.

TABLE 3. ~ ~ : e s t i m a t e s of c o p p e r and zinc concentrations (~g g-~), w i t h 95% c o n f i d e n c e limits (CL) for amphipods of 5 mg s t a n d a r d i z e d dry w e i g h t d e r i v e d from b e s t - f i t double log regressions. Samples s h a r i n g any letter in A N C O V A c o l u m n for one metal are not s i g n i f i c a n t l y different. Site

Copper conc.

Trelissick Carbis Bay St Euny Budshead Kew g a r d e n s

45.3 67.5 61.4 15.4 68.1

Of p a r t i c u l a r

note

(CL) 34.9,58.8 50.8,89.6 40.7,92.6 2.6,91.6 45.8,77.1

any other site.

a b,c,d,e d,e a,c,e a

is the r e l a t i v e l y

tion for A_~. d o r r i e n i is not s u f f i c i e n t

shown.

c o n c e n t r a t i o n s were ent n a t u r a l

(Dines,

which

low body copper concentraalthough

the r e d u c t i o n

the

SW C o r n w a l l

sites,

lowest at T r e l i s s i c k

were

however, once

of the w i d e v a r i a -

indicated by the w i d e c o n f i d e n c e

or a n t h r o p o g e n i c m e t a l

lodes

132,238 a 125,179 c 69.4,131 e 52.2,1714 a,b 106,149 d

is p r o b a b l y a r e f l e c t i o n

Carbis Bay and St Euny, copper

ANCOVA

to cause a s i g n i f i c a n t d i f f e r e n c e from that at

This

For

(CL)

177 149 95.3 299 125

from B u d s h e a d wood,

bility in the data at this site, limits

Zinc conc.

ANCOVA

A__~.d o r r i e n i

gardens,

influences.

copper

with no appar-

The s a m p l e s

from

are from sites w i t h n e a r surface

the

scene

of m u c h

mining

activity

1956).

Table 4 p r e s e n t s the copper c o n c e n t r a t i o n s m e a s u r e d in the litter

1517

c o l l e c t e d from each site. There are no g r o s s l y e l e v a t e d c o n c e n t r a tions of copper in the litter Martin,

1982). ANOVA, however,

copper concentrations

were

(normal range 10-20 ~g g-l, H o p k i n & has shown

somewhat

(see T a b l e 4) t h a t litter

r a i s e d at B u d s h e a d W o o d and

Carbis Bay, but w e r e lower at the other t h r e e sites. It is u n f o r t u nate that the a v a i l a b l e data span only a l i m i t e d r a n g e of p o s s i b l e litter c o p p e r c o n c e n t r a t i o n s . It w o u l d be i n s t r u c t i v e to o b t a i n data for an e n t i r e l y u n c o n t a m i n a t e d e n v i r o n m e n t or an e x c e p t i o n a l l y cont a m i n a t e d habitat.

T A B L E 4. Mean (SD) c o p p e r and zinc c o n c e n t r a t i o n s of l e a f - l i t t e r from t h e c o l l e c t i o n s i t e s of ~ ~ . Samples snaring any letter in the A N O V A c o l u m n for one m e t a l are not s i g n i f i c a n t l y different. Litter C o p p e r conc. (~g g-l)

Site

Zinc conc. (~g g-l)

ANOVA

Trelissick 9.5 (3.3) Carbis Bay 11.4 (1.7) St Euny 5.7 (1.2) B u d s h e a d wood 16.2 (3.3) Kew gardens 9.8 (5.3) Colonsay 10.2 (0.96)

a b a b a a

88.5 66.7 91.1 496 50.3 148

ANOVA

(33.5) (ll.0) (27.8) (16.2) (17.7) (23.2)

a a a b a a

Zinc

Table 2b

summarizes the i n f o r m a t i o n on d o u b l e log r e g r e s s i o n s of

zinc c o n c e n t r a t i o n St E u n y

there

for ANCOVA. confidence ANCOVA. trations

in A.

is a s i g n i f i c a n t

Table

3 presents

limits,

As T a b l e

together

3 shows,

in A__~.d o r r i e n i

tions were particularly, from

Budshead

dorrieni

wood,

and

against dry weight.

regression,

the with

there

estimated summaries

is a w i d e

from the sites

but

for

confirming

the

dry

with

95%

comparisons

by

of

weight

need

range

of z i n c c o n c e n -

sampled.

Zinc concentra-

and s i g n i f i c a n t l y , lower,

Again,

not

raised

in a m p h i p o d s

significantly

so,

in

1518

samples

from St Euny and Colonsay.

Table 4 p r e s e n t s the zinc c o n c e n t r a t i o n s of litter from the collection sites.

A N O V A has shown that litter

BudsheadWoodare

zinc c o n c e n t r a t i o n s

from

s i g n i f i c a n t l y (P<0.001) e l e v a t e d in c o m p a r i s o n with

the o t h e r sites. Hopkin & M a r t i n (1982) have shown that zinc concent r a t i o n s in u n c o n t a m i n a t e d litter can vary w i t h i n the range 50 - 300 ~g g-l,

i n d i c a t i n g that B u d s h e a d Wood leaf litter

is i n d e e d

zinc

enriched. Thus it w o u l d appear that A_~.d o r r ~ e n i may prove u s e f u l as a m o n i t o r of a m b i e n t zinc availabilities, copper,

and may s i m i l a r l y p r o v e u s e f u l for

over a w i d e r range of ambient c o p p e r a v a i l a b i l i t i e s .

DISCUSSION

There is no c o m p a r a b l e p u b l i s h e d i n f o r m a t i o n on the b i o a v a i l a b i l ities of h e a v y m e t a l s

at the

collected.

for the h i g h

The reasons

from B u d s h e a d

wood

remain

sites

from w h i c h

are

areas

Atkinson, appear

of p a s t

unclear,

1988),

not

to

extensive

although

influence

do~rieni

zinc c o n c e n t r a t i o n although

aerial d e p o s i t i o n from local P l y m o u t h industry. Euny

A.

mining

it m a y

were

in litter be d u e

to

Carbis Bay and St

activity

(Dines,

1956;

it m a y be a r g u e d t h a t s u c h a c t i v i t i e s the

litter

metal

concentrations,

and

serious p o l l u t i o n is p r o b a b l y r e s t r i c t e d to the i m m e d i a t e area on and a r o u n d spoil tips

(Marples,

1979).

These studies have shown that A. d o r r i e n i is a net a c c u m u l a t o r of essential

trace metals and does not r e g u l a t e b o d y c o p p e r or zinc

concentrations. Weeks

(1990) had shown that s e m i - t e r r e s t r i a l tali-

trids eat p r o p o r t i o n a t e l y more m a c r o a l g a l m a t e r i a l w i t h low c o n c e n t r a t i o n s of c o p p e r or zinc than algal material with h i g h e r c o n c e n t r a tions of c o p p e r or zinc. The r e d u c t i o n in m e a s u r e d b o d y zinc concen-

1519

tration

in A r c i t a l i t r u s d o r r i e n i w h e n f e e d i n g at the h i g h e s t zinc

concentration may

similarly

reflect

such

feeding at high food metal concentrations.

a tendency

for r e d u c e d

Care, however, s h o u l d be

taken w h e n i n t e r p r e t i n g such results. It is p o s s i b l e that the amphipods w e r e not d i s c r i m i n a t i n g on the basis of c o p p e r or zinc concent r a t i o n s in the food, but that t h e i r c h a n g e in c o n s u m p t i o n rate was a r e s p o n s e to a d i f f e r e n c e in c o n c e n t r a t i o n of the anion (in this case chloride,

from the metal salt) w h i c h t h e y were able to taste.

W i e s e r et al.

(1976) p r o p o s e d that a g o o d m o n i t o r species s h o u l d

contain the e l e m e n t in p r o p o r t i o n to its c o n c e n t r a t i o n in e i t h e r the s u r r o u n d i n g m e d i u m or in the food, and s h o u l d c o n c e n t r a t e the e l e m e n t in some part of its body to increase the s e n s i t i v i t y of detection. A r G i t a l i t r u s d o r r i e n i satisfies the first of these conditions. T h e r e does not a p p e a r to be any s e l e c t i v e a d v a n t a g e in m e a s u r i n g the c o p p e r or zinc c o n c e n t r a t i o n s

of i n d i v i d u a l

body components when

it is

s a t i s f a c t o r y to use whole animals. H o p k i n e_~tal, (1986) a d v o c a t e d the use of t h e h e p a t o p a n c r e a s

of the w o o d l o u s e

Porcellio

scaber

for

m o n i t o r i n g the d i s p e r s i o n of c a d m i u m from a c o n t a m i n a t e d locus, due to its g r e a t e r s e n s i t i v i t y c o m p a r e d w i t h the use of w h o l e animals. Many t e r r e s t r i a l

invertebrates

are u n s u i t a b l e m o n i t o r s

of metal

pollution. H o p k i n (1989) put forward seven c r i t e r i a p e r t a i n i n g to the e s t a b l i s h m e n t of a regular s a m p l i n g programme. criteria

A feature of these

is t h a t the chosen animal s h o u l d be g e o g r a p h i c a l l y w i d e -

spread enough to allow direct c o m p a r i s o n s of c o n t a m i n a t i o n b e t w e e n w i d e l y spread areas. This is p r o b a b l y the single m o s t r e l e v a n t chara c t e r i s t i c at p r e s e n t p r e v e n t i n g the f u r t h e r d e v e l o p m e n t of A. dorri~ni as an "alternative"

Arcitalitrus

terrestrial biomonitor

d o r r i e n i has scope

in the U.K.

as a t e r r e s t r i a l

biomonitor

for

the e s s e n t i a l metal zinc and p o s s i b l y c o p p e r in the m e t a l l i f e r o u s

1520

districts of S.W. England. however,

will

limit

(though the species' land over,

(Australia), it is q u i t e

the

Its presently restricted distribution, extent

of

its

usefulness

range seems to be expanding).

however, likely

it has u n a s s e s s e d that

other

related

in B r i t a i n

In its native

potential.

More-

landhoppers

would

perform a similar function. ACKNOWLEDGEMENTS

Thanks are due to Dr P.S. Rainbow and Dr P.G. Moore for their help and discussion during this project and for reading drafts of the manuscript. Prof. M.H. Depledge is also thanked for discussion and critically reading the manuscript. The comments of Dr A.M.M. Richardson were also greatly appreciated.

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