CHAPTER 9 The Principal Fouling Organisms The purpose of this chapter is to present an ele- an introduction to the scientific literature wil find mentary account of the principal organisms found references at the end of the chapter. When identi- in fouling communities in order that those un- fication to the scientific name is essential, speci- trained in zoology may observe fouling with mens should be sent to the United States National greater understanding. It contains an account of Museum, Washington, D. C., or to a museum of the appearance, habits, mode of dispersal, and natural history where they can be classified by ex- relative importance of these forms. perts. The descriptions are intended only to enable practical workers to recognize the commoner or- MICROSCOPIC FOULING ORGANISMS ganisms by the name of the group to which they The microscopic fouling organisms include bac- A B FIGURE 1. Photomicrographs of slime Elm organisms. A. A type of bacteria from a bacterial slime film. From Dobson (5). B. A diatom slime film. belong. In the case of the barnacles, the more com- tcria, diatoms, protozoa, and rotifers. The bacteria mon North American species are described in suf- aLd diatoms produce slime films which form ficient detail to indicate how species may be iden- promptly on submerged surfaces. The protozoa are tified, but the descriptions are inadequate to per- commonly associated with these films though they mit the inexperienced worker to classify barnacles take no part in their production. The successive to the species with certainty. The identification changes in these populations on a submerged sur- and naming of the species of all fouling organisms face are shown in Figure 1, Chapter 4. It is char- are beyond the scope of this work. acteristic that the early multiplication of bacteria Three manuals, prepared to assist dockyard work- is followed by the development of diatoms and ers in reporting the conditions of ship bottoms, protozoa in the slime. which describe and ilustrate fouling organisms in In addition to the living forms in slime films, an even more elementary way, are listed as Refer- organic and inorganic detritus, mud, sand, and ences 96, 97, and 98. other particulate materials suspended in sea water Persons desiring more complete descriptions or become incorporated in the film. A common type 118 THE PRINCIPAL FOULING ORGANISMS 119 of slime bacteria is shown in Figure 1A; a slime The importance of slime films is twofold: they consisting predominantly of diatoms is ilustrated may influence directly the attachment of. other or- in Figure lB. ganisms; and they may decompose paint materials or otherwise alter the activity of a paint. The direct Bacteria and Bacterial Slimes effect of the slime on the attachment of other or- The bacteria which form slime films are present . ganisms has been discussed Ín Chapter 4, where in sea water at all times of the year, though their it is shown that the slime film may favor the at- numbers vary within wide limits depending upon tachment of several species of macroscopic ani- available organic matter, temperature, and degree mals. The effects of slime bacteria on paints and of pollution. A slime fim may, therefore, be ex- pected whenever a surface is submerged, but there 25 are marked seasonal variations in its rate of de- velopment. Its magnitude at different seasons 20 u 15 parallels the sea temperature. The total weight of o ii the fim varies about thirtyfold-from a few ~ w hundred micrograms per square centimeter in the f- winter, to 4000 in the summer. The amount of sea water contained in a square centimeter of film is of the order of .005 to .05 cubic centimeters. The rm SEA SALTS '" dry material of the film is about 30 per cent of the ~ D INSOLUABLE ASH total wet fim. Figure 2 shows the dry weight of -! :1 2.0 D ORGANIC MATTER slime developed during each thirty-day period "~ I- throughout a year at Woods Hole. Organic matter ;: makes up 10 to 25 per cent of the total dry weight, ~ 1.0 and averages about 20 per cent. During the colder o parts of the year the insoluble ash is low, increas- ing during the summer to as much. as 60 per cent of the entire weight. The remainder of the fim FMAMJJASON D consists of sea salts. FIGURE 2. Weight and composition of slime films developed in 30-day period, at Woods Hole, 1940-1941. (Above). The sea water temperature. The initial step in the production of a slime fim is the attachment of bacteria to the sub- merged surface. After attachment the bacterial paint materials are discussed in Chapters 14 and cells reproduce by dividing. Each of the resulting 16. For specific works on bacterial and slime films, daughter cells then grows to normal size and di- see References 10-17. vides again. Bacterial counts on developing slime films indicate that the population doubles in about Diatoms four hours (14). The reproductive rate depends Diatoms are microscopic plants which may live mainly upon the temperature and the availability suspended in the water or attached to submerged of nutrients. Thus, the amount of slime on a sur- surfaces. They contain a brown pigment which face submerged in the sea may depend both upon gives them a characteristic color. They also con- the population of bacteria originally present in the tain chlorophyll and, in the presence of light, water and upon their growth after attachment. manufacture their own foods from the chemical Thirty-seven kinds of bacteria reported from nutrients in the water. Ilustrations of some com- fouled structures are listed in the Appendix to mon diatoms are given in Figure 3. Chapter 10. It has been observed that 74 per cent - Each diatom is a single cell enclosed in a siliceous of the bacteria isolated from panels suspended in shell which consists of two similar halves, one the sea were able to attach themselves to surfaces fittng inside the other like a pil-box and its cover. firmly enough so that they could not be washed In many species the shells are simple in structure, off with gently running water (15). Among these others have hair-like or horn-like projections. The periphitic or attaching bacteria, 21 distinct and shells are marked with many rows of minute dots representative types were isolated and studied. All or striations which are so fie, indeed, that the were gram-negative rods which varied greatly in usual test of the quality of a microscope is its length. Only 4 of them were capsulated, and none ability to make them visible. Figure 3A indicates of them produced spores. None were found to the construction of the shell and the arrangement have special attachment organs. of the cell contents. 120 MARINE FOULING AND ITS PREVENTION !t,~.'..'...c.'h......:"d:~j''7~K''HO~' '~~~1~ I 3 A c E D B ~~w.;i ::n':,,:~:~ ci~~i~~~lli:I:II!IWNlt,I:I',~im::~m IIIHUlll:liIIHII=rIH:IIfI ~:,¡¡:~i~i¡'~i~h.".ii;;iî~iÎi~i~~i~:.~~!;ii~~¡~ 1::~~~~;~::;!:!~ïi~::~;;!~:;i~~i!¡i:ti~~:~~.'~~~~ e::~!':":::1:'::':.:::I':I:'''I::!III::;::I:.;¡:'I!:i:::I:,m::!;i:; ~41!"..!':,":::::I:!::lm::I:!,,';!::i::.:::I:,~ -= ( :~~:;.,,,~~,,,,,.";;,,,~;',~,,,:';::::::;:;;;¡~i:=ii~~'t~~~¡;=!~~~¡;í:~::m.!~ ~~~~:~~~'f¡j~~~~~:::~~:~":'~:~¡,:~!;:;i:;;I;¡::;::';:~~.:";;;'~:::;:;::--~I~':.~:::-,.::) ci:r:~~'~:::::::::'~::~~~~~:'::::~::~~:!~:::;ir.!:~:::~::r.~~::~~:'imm:''::~:::~~::~\:::ti::¡¡~\:im::::::\::::~:::::::,:::~::::::: ~::::::!:'::'::~::::::::!.: ,-:: ~-,: ':'.: "::':':: G F FIGUR 3. Diatoms. A. Diagrammatic lengthwise sections of three stages in From Boyer (18). the division of a diatom. 1 is the mature parent cell; in 2, the halves of the shell D. Three forms of Fragilaria. Actuallength of the longest individual: 0.07 mm. are being pushed apart and the division of the cell contents has begun; in 3, the From Boyer (18). daughter cells are complete and the new "male" halves are forming within the E. Top and bottom views of Cocconeis pediculus. Actuallength: 0.03 mm. From edges of the parent's shells. Modified from Wolle (20). Boyer (18). B. Licmophora llabel/ala. A stalked colonialdiatom, Several fan-like groups F. Various forms of Synedra. Actuallength of the longest individual: 0128 mm. of individual diatoms are attached to the branches of the stalk. Actuallength of From Boyer (18). individuals in the uppermost group: 0.03 mm. From Wolle (20). G. Meloseira nummuloides. Eight individuals connected to form a fiament. C. Seven species of Navicula. Actuallength of the longest individual: 0.07 mm. Actual width of fiament: 0.02 mm. From Wolle (20). All diatoms have a gelatinous covering over the other surfaces. The slimes formed by diatoms are shell. Some colonial species, like that shown in less slippery than bacterial slimes, and when dry Figure 3B, have their gelatinous coverings ex- are gray or greenish-gray (10). Fresh dìatom tended as tubes or stalks which attach to immersed slimes may be colored or gritty, may resemble objects and prevent the diatoms from being car- brown oil, or look like bubble-filled mud. ried away. These colonies may break up, disperse For detailed works on diatoms, Boyer (18), Van in water currents, and establish new çolonies on Heurck (19), and Wolle (20) may be consulted. THE PRINCIPAL FOULING ORGANISMS 121 Protozoa B. Branching tree-shaped growths, the branches not expanded at the tips. Bryozoa p. 141 Protozoa are single-celled animals which range C. Straight or branching growths, each thread ter- in size from .002 milimeters to several centimeters minatingin an expanded tip.......... Hydroids p.l44 in the greatest dimension. Their minute size and D. Rounded soft spongy masses. Tunicates p. 147 their failure to form massive colonies render them The names applied to fouling organisms by unimportant as fouling organisms.