16 Marine Conditioning Films GEORGE I. LOEB and REX A. NEIHOF
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Naval Research Laboratory, Washington, D.C.
Changes on the surfaces of well-defined solids exposed to sea water from diverse sources have been observed by microelectrophoresis, ellipsometry, and contact angle measurements. These observations indicate that an adsorbed film forms rapidly on a variety of surfaces. Other experiments with artificial and photo-oxidized sea waters show that the film is organic. It lowers the surface energy of platinum and imparts a moderately negative electrical charge to most surfaces. Dissolved polymeric materials of biological origin have properties required for this interaction. Fluorescence measurements give a direct indication of some participation by humic substances in film formation. Adsorption of dissolved organic materials thus constitutes a very early step in fouling, a step that may affect the sequence of events leading to macrofouling.
"iyj"arine organisms select t h e i r h a b i t a t s o n t h e basis of m a n y (I). which
factors
A m o n g these, t h e n a t u r e of the surface of the m a t e r i a l o n
an organism
settles
or
t h r o u g h w h i c h it b u r r o w s
has
a
pro-
n o u n c e d effect. T h e surfaces of m a t e r i a l s i m m e r s e d i n sea w a t e r m a y be a l t e r e d b y p r i m a r y films d e s c r i b e d b y H e n r i c i ( 2 ) , Z o B e l l a n d A l l e n
(3),
a n d others. T h e p r i m a r y film consists of a c o m m u n i t y of m i c r o o r g a n i s m s , t h e i r s l i m y exudate a n d c o m p o n e n t s a d s o r b e d researchers
f r o m the w a t e r .
r e p o r t that p r e l i m i n a r y exposure of c u l t u r e vessels
Many to
sea
w a t e r , w h i c h a l l o w s the f o r m a t i o n of a p r i m a r y film, favors t h e subseq u e n t g r o w t h of m a r i n e organisms i n t h e m . surfaces
M o s t studies of i m m e r s e d
h a v e not d i s t i n g u i s h e d b e t w e e n the effects of
adsorption
of
d i s s o l v e d substances f r o m the n a t u r a l w a t e r a n d c o l o n i z a t i o n b y m i c r o organisms.
H o w e v e r , m e m b r a n e - f i l t e r e d sea w a t e r does not r e n d e r c l e a n
s a n d a t t r a c t i v e to c e r t a i n b u r r o w i n g m a r i n e w o r m s t h e r e s i d u e left o n the
filter
without replacing
(4). 319
Baier; Applied Chemistry at Protein Interfaces Advances in Chemistry; American Chemical Society: Washington, DC, 1975.
320
A P P L I E D
C H E M I S T R Y
A T
P R O T E I N
I N T E R F A C E S
A d s o r p t i o n of d i s s o l v e d m a t e r i a l w i t h o u t s i m u l t a n e o u s
adsorption
of m i c r o o r g a n i s m s is sufficient to change the s u i t a b i l i t y of a surface for subsequent
b i o l o g i c a l settlement.
tissue culturists w h o
T h i s is r e c o g n i z e d
by many
c o n d i t i o n c u l t u r e vessels i n s e r u m
biologists also h a v e exposed
(5).
organ Marine
surfaces to cell-free extracts of a d u l t b a r -
nacles to e n h a n c e s e t t l i n g of l a r v a e (6);
extracts of different a l g a l species
a d s o r b e d o n i m m e r s e d surfaces r e n d e r t h e surfaces s e l e c t i v e l y attractive to the species of Spirobis n o r m a l l y f o u n d o n that p a r t i c u l a r t y p e of algae (7,
8).
Q u a n t i t i e s of m a t e r i a l e q u i v a l e n t to those f o u n d i n
adsorbed
films are sufficient to m o d i f y the attractiveness of surfaces for a t t a c h i n g organisms. Downloaded by CORNELL UNIV on July 20, 2016 | http://pubs.acs.org Publication Date: June 1, 1975 | doi: 10.1021/ba-1975-0145.ch016
T h e s e cases are clear e v i d e n c e that extracts of species closely a l l i e d to the l i f e c y c l e of a n a t t a c h i n g o r g a n i s m m a y h a v e p r o n o u n c e d
effects
o n its a t t a c h m e n t ; m e c h a n i s m s b a s e d o n m o l e c u l a r r e c o g n i t i o n s i m i l a r to enzyme-substrate
or a n t i g e n - a n t i b o d y c o m p l e m e n t a r i t y m a y b e
envi-
s i o n e d . H o w e v e r , it is c o n c e i v a b l e t h a t d i s s o l v e d c o m p o n e n t s i n t h e sea m a y alter surface p r o p e r t i e s of i m m e r s e d surfaces i n m o r e g e n e r a l w a y s t h a t w o u l d affect a t t a c h m e n t a n d c o l o n i z a t i o n . T h u s , a d h e s i o n of o r g a nisms to a surface m i g h t b e i n f l u e n c e d b y h y d r o p h i l i c or
hydrophobic
characteristics of the surface, the surface c h a r g e a n d charge d e n s i t y , a n d the c h e m i c a l f u n c t i o n a l groups a v a i l a b l e for r e a c t i o n .
Zisman ( 9 ) and
B a i e r , S h a f r i n , a n d Z i s m a n ( J O ) h a v e r e v i e w e d the surface c h e m i s t r y and physics
of
biological adhesion
M a r s h a l l , Stout, a n d M i t c h e l l ( I I )
emphasizing wetting
phenomena;
h a v e p r e s e n t e d arguments a n d e v i -
d e n c e that e m p h a s i z e the p o s s i b l e i m p o r t a n c e of e l e c t r i c a l c h a r g e a n d d i p o l e interactions i n a t t r a c t i n g m a r i n e b a c t e r i a to surfaces i n the r e v e r s i b l e phase of t h e i r i n t e r a c t i o n . T h e s e p r o p e r t i e s of surfaces m a y b e d r a s t i c a l l y a l t e r e d b y a d s o r p t i o n of d i s s o l v e d substances f r o m the surr o u n d i n g m e d i u m (12,
13).
W e h a v e i n v e s t i g a t e d the a d s o r p t i o n of s o l u b l e components
from
sea w a t e r a n d its effects o n the w e t t a b i l i t y a n d c h a r g e characteristics of s e v e r a l w e l l c h a r a c t e r i z e d s o l i d surfaces i n o r d e r to d e t e r m i n e w h e t h e r changes d o i n d e e d o c c u r f r o m this cause a n d w h e t h e r t h e i r m a g n i t u d e is l i k e l y to b e
sufficient to affect
s i g n i f i c a n t l y later processes o n
surface. W e h a v e c a l l e d this a d s o r p t i o n m o l e c u l a r f o u l i n g
the
(14).
Experimental Water Samples and Their Treatment. Samples of sea w a t e r f r o m a v a r i e t y of sources w e r e u s e d . C o l l e c t i o n m e t h o d s e v o l v e d w i t h e x p e r i ence. T h e most satisfactory m e t h o d uses a v a c u u m c h a m b e r i n t o w h i c h a T e f l o n b o t t l e is p l a c e d . A T e f l o n t u b e d i p p i n g i n t o t h e sea d r a w s the w a t e r s a m p l e i n t o the c h a m b e r a n d b o t t l e . E a r l i e r samples w e r e t a k e n
Baier; Applied Chemistry at Protein Interfaces Advances in Chemistry; American Chemical Society: Washington, DC, 1975.
16.
L O E B
A
N
D
N E I H O F
Marine
Conditioning
321
Films
b y a w e l l - r i n s e d p o l y e t h y l e n e b u c k e t , or b y s u c t i o n t h r o u g h w e l l - r i n s e d p o l y e t h y l e n e or p o l y p r o p y l e n e tubes a n d stored i n p o l y e t h y l e n e or p o l y p r o p y l e n e bottles t h a t w e r e r i n s e d w i t h sea w a t e r at the t i m e of the collection. Glass a n d Teflon ware was acid-cleaned a n d rinsed; Teflon ware was s u b s e q u e n t l y steamed. O t h e r p l a s t i c w a r e was d e t e r g e n t - w a s h e d , r i n s e d w i t h water followed b y methanol, and exhaustively rinsed w i t h distilled w a t e r (15, 1 6 ) . Sea w a t e r samples w e r e c o l l e c t e d f r o m ( a ) C h e s a p e a k e B a y at the P a t u x e n t N a v a l A i r S t a t i o n at h i g h t i d e w i t h s a l i n i t y of the samples v a r y i n g b e t w e e n 9% a n d 16%
