The Pipeline Menace of Freshwater Bryozoans 203-208 © Biologiezentrum Linz/Austria; Download Unter

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Zeitschrift/Journal: Denisia

Jahr/Year: 2005

Band/Volume: 0016

Autor(en)/Author(s): Wood Timothy S.

Artikel/Article: The pipeline menace of freshwater bryozoans 203-208 © Biologiezentrum Linz/Austria; download unter www.biologiezentrum.at

The pipeline menace of freshwater bryozoans

T.S. WOOD

Abstract: Under certain conditions, conduits carrying unfiltered water from lakes or rivers eventually become lined with bryozoans, hydroids, sponges, and many other organisms. By blocking the conduit or clogging end use devices, these nuisance animals impose serious economic costs. Bryozoans are probably the most common among the fouling animals. Three factors hinder control efforts: (1) dormant bo- dies (statoblasts or hibemaculae) that tolerate harsh physical and chemical treatments; (2) regeneration of bryozoan colonies from pockets of living tissue; (3) easy dispersal of bryozoans through air and water. Control measures must take into account the species involved, their source, their accessibility, the end use of the water, and the seasonal conditions in which the problem occurs.

Key words: Bryozoa, biofouling, economic costs, control measures.

Introduction Before the widespread use of sand filtration, „pipeline animals" were discharged Whenever a pipeline or waterway car- regularly from household faucets. One bryo- ries untreated water from a lake or river it zoan species was discovered in New Zealand soon becomes home to a variety of inverte- for the first time after "...specimens had brate animals. This point was graphically il- come through the ordinary (Dunedin) town lustrated by HASSALL (1850) in his classic water-supply tap, about a mile and a half color plates published in "Microscopical Ex- from the reservoir, and were floating in a amination of the Water Supplied to the In- white earthenware basin" (HAMILTON habitants of London and Suburban Dis- 1902). Today colonies of that same species tricts" (Fig 1). The drawings, showing an ab- still plague water lines in the City of undance of rotifers, nematodes, protists and Dunedin, clogging filters and microstrain- microcrustaceans enlarged 250x, contribu- ers, often causing considerable damage and ted to a heated debate in England over the impeding the supply of drinking water quality of water supplied by public utilities. (Smith et al. this volume). Pipeline residents are not always so microscopic. Hydroids and bryozoans are The situation in Dunedin is unique only among the invertebrate animals that thrive in that the cause is recognized. Typically, in dark places where continuously flowing seasonally clogged filters are tolerated as an water brings an unlimited supply of particu- unknown nuisance. For example, filters for late food (Fig 2). Free branches of the tubu- the water piped from Lake Springfield (Illi- lar colonies may become tangled and inter- nois) are frequently burdened by what wa- twined, filling the pipeline interior with a terworks operators term „moss and turds", dense meshwork that impedes or blocks wa- actually living bryozoans and sponges. Dur- ter flow. Pieces of colonies are eventually ing peak seasons these are laboriously carried off by the water until they clog a fil- scooped out by hand, and the old cement ter, water sprinkler orifice, or other end-use conduit bringing water from lake depths re- device. The colonies leave behind dormant, mains a large source of the fouling animals. resistant structures attached to the pipeline Throughout the world, bryozoans grow on interior, which are the „seeds" to start new filters, fountains, irrigation systems, cooling Denisia 16, zugleich Kataloge der OÖ. Landesmuseen colony growth. tower grids, water supply and wastewater fa- Neue Serie 28 (2005), 203-208 © Biologiezentrum Linz/Austria; download unter www.biologiezentrum.at

Fig. 1: Representation of cilities (WOOD & MARSH 1999). Typically microscopic organisms appearing known as "moss" or "algae" they are seldom in the water lines in the City of London to alert recognized as animals (Fig. 3). Fouled sur- residents to the poor quality faces are usually ineffectively cleaned and of the public water supply, then returned to service. from a color plate by HASSALL (1850). The economic costs of bryo:oan fouling is probably high. In 1907 a wastewater treatment plant in Phoenix, Arizona had bryozoans removed by the truckload until an en- gineering firm recognized the problem and took steps to eliminate it (MARSH & WOOD 1997). At Florida golf courses entire clogged irrigation systems sometimes have to be dug up and replaced. The chronic fouling of decorative fountain pumps causes the motors to burn out prematurely (Fig 4). Because the cause is so seldom recognized there is no uniform reporting, and the economic cost is impossible to estimate. Information about bryozoan fouling is scanty at best in scientif- Fig. 2: Colony of the bryozoan, ic, popular, or commercial literature. Even Plumatella bombayensis, growing 1 cm the internet is practically silent on the issue. on a plastic substratum in eutrophic waters of Thailand. Good summary information on the biology of freshwater bryozoans is provided by WOOD (2001) and WOOD & OKAMURA (2005). This paper will present basic information about bryozoans that may be useful to anyone trying to solve a problem of bryozoan fouling.

Bryozoan dormancy

It is an axiom of aquatic biology that freshwater invertebrates include in their life cycle a dormant structure specialized in sur- viving adverse conditions (BARNES et al. 2001). These may be thick-walled eggs or cysts, encapsulated germinal tissue, or even entire organisms that undergo long-term aestivation. For various lengths of time such structures may be unaffected by desiccation, freezing temperatures, toxic chemicals, lack of oxygen, and other suboptimal conditions.

Bryozoans have evolved several types of dormant structures. Those species classified in the exclusively freshwater class Phylacto- laemata (such as Plumatella) produce asexu- al statoblasts that are either attached firmly to the substratum or else released freely into the water. Sessile statoblasts, called sessoblasts, adhere firmly to the substratum (Fig. Fig. 3: Handful of plumatellid bryozoans (Plumatella vaihiriae) from the wall of a 5b). No larger than a period on this page, secondary clarifier of a municipal wastewater treatment plant in Phoenix, Arizona, USA. They look more like plants than animals. they are easily overlooked by workers clean-

204 © Biologiezentrum Linz/Austria; download unter www.biologiezentrum.at ing away bryozoan colonies. Sessoblasts can Fig. 4: Bryozoans lie dormant for months, either wet or dry, (Plumatella rugosa) growing on a and then germinate to form new colonies. submersible pump for a The free types of statoblast are termed floa- decorative fountain in a toblasts because they are usually buoyant pond in Centerville, (Fig. 5a). Far more numerous than sesso- Ohio, USA. blasts but just as small, floatoblasts are the form most likely to gain entry to pipelines.

Not all freshwater bryozoans produce statoblasts. In the class Gymnolaemata a few species, such as Paludicella, isolate a small part of the colony, thicken the walls, and fill it with yolk and germinal tissue (HARMER 1913). There are apparently two types of these so-called hibernacula: one is dark, spindle-shaped, and occurring within the normal zooid walls; the other is a yel- lowish, irregularly shaped body attached to the substratum. Both of these are too small to be examined without magnification. Vir- tually nothing is known about the tolerance of hibernacula to adverse conditions. How- ever, like statoblasts, they are capable of overwintering in a dormant state and then germinating whenever suitable conditions return.

Being dormant, statoblasts and hiher- naculae are unresponsive to treatments that Fig. 5: Typical would normally kill a living colony. Bryo- bryozoan zoans may be removed from a fouled surface, statoblasts. but if dormant structures are left behind the a: buoyant fouling problems will continue to recur. statoblast (floatoblast) of Plumatella The problem of resilience vaihiriae; b: attached Bryozoans respond to unfavourable con- statoblast (sessoblast) of ditions by withdrawing deeply into the Plumatella colony interior. In this position they may emarginata. Scale withstand exposure to low levels of heavy bar = 100 urn. metals and other toxins for hours or even days. In a toxicity bioassay it is not uncom- mon for such an apparently dead colony to "revive" when it is returned to clean water. The same observation has been made for hydroid colonies of Cordylophora (FOLINO- ROREM & INDELICATO 2005).

Death does not overtake the entire colony at once, but occurs instead one zooid at a time, depending on zooid age, condi- tion, position within the colony, and possi- bly other factors. It is even possible for a dead zooid to be replaced by an entirely new zooid derived from a small reservoir of ger-

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high water line on homes submerged for several weeks during spring flooding of the Mis- sissippi River. Similar scenes are common during the rainy season in Southeast Asia (Fig. 6). Floatoblasts are easily drawn from rivers or lakes into irrigation systems where they may lodge and germinate. Because of their small size the floatoblasts are difficult and expensive to remove from incoming water.

Bryozoan statoblasts are also carried pas- sively by migrating animals. Microsatellite data suggest that waterfowl are likely vectors for ongoing dispersal of Crisuitella mucedo in Europe (FREELANP et al. 2000). In some instances, species distribution often seems to follow routes of bird migration (WOOP 2002). In a series of experiments, CHAR- ALAMBIROU et al. (2003) determined that Fig. 6: Bryozoan colonies left behind when minal tissue (WüOP 1973). Exactly how this floatoblasts can survive passage through the flood waters retreated from a house along occurs and under what circumstances are the Bang Pakong River in central Thailand. digestive tract of ducks, suggesting that Colonies appear on the neck and body of questions not yet resolved. these and other waterfowl could disperse the decorative ceramic goose as well as on bryozoans even during long distance migra- some of the woodwork. Photo by Jukkrit Because of these resilient mechanisms, tion. Not surprisingly, wastewater treatment Mahvjchariyawong. it requires surprisingly high concentrations of biocides to kill live bryozoan colonies. plants reporting bryozoans in their second- Often this cannot be done without inflict- ary clarifiers also note frequent visits by ducks that may be carrying viable statoblasts ing serious damage on nontarget organisms. from natural habitats. For example, low concentrations of copper sulfate may have little long-term impact, Those bryozoan species lacking free sta- while higher concentrations would create toblasts (Fredericella, Paludiceüa) are proba- unacceptable consequences in irrigation or bly distributed either by drifting fragments public water supply systems. of colonies or by substrata (e.g. aquatic plants) bearing colonies or other dormant The problem of dispersal structures.

Freshwater bryozoans are common in freshwater habitats worldwide. Species such Control of bryozoan fouling as Plumatella casmiana are reported from Successful control strategies must be tai- every continent except Antarctica (WOOD lored to each fouling situation. Important & WOOP 2000), while others, such as Plu- considerations should include the source of matella mukaii, have widely distributed but water, the source of fouling bryozoans, the highly disjunct populations (WOOD 2002). species of bryozoans involved, and the end It is clear from distribution data that fresh- use of water. Also important are the nature water bryozoans have little difficulty getting of the fouled surfaces, access to those sur- around. faces, whether they can be taken out of service, and for how long. Buoyant floatoblasts are responsible for much of bryozoan dispersal. Produced in The first step of effective control is to large numbers by most species, they are ef- determine whether bryozoans are generated fectively transported in flowing water. Flood within the system or entering with the wa- waters also distribute statoblasts over wide ter source. If the bryozoans are the type that areas where they find new places to germi- produce buoyant statoblasts it may be possi- nate. Terrence Marsh (pers. comm.) has re- ble to find the source by setting out a series ported plumatellid colonies growing at the of statoblast traps: small blocks of rough

plastic foam (expanded polystyrene, such as hour LCj0 for P. bombayensis is established at Styrofoam®). Smooth foam, as in some fast 0.17 mg/1 (WOOD et al. 2004). food containers or construction panels, is Antifouling paints have so far proven not as effective as rough, sandpapery materi- ineffective against freshwater bryozoans al from hobby shops. Small blocks of foam (APROSI 1988). Zinc galvanized surfaces ap- are tethered in the water at appropriate sites pear not to support bryozoan growth and allowed to remain for several days or (COLLINS 1978), but plastic and aged wood weeks to see where statoblasts accumulate. present very favorable substrata. Data from Unmagnified, the statoblasts appear as uni- GREENLAND et al. (1988) suggest that poly- form black specks; with a lOx lens it is pos- ethylene is more attractive to bryozoan col- sible to distinguish the outer buoyant cells onization than vinyl, but virtually all known and the darker central capsule. plastics, rubber, stone, glass and even cor- Technically, statoblasts and colony frag- roding iron will support bryozoan growth to ments entering an irrigation system from some degree. surface waters can be removed by filtration. Although all bryozoans thrive in quiet Products such as the self-cleaning filters water, the most rapid and luxuriant growth made by Orival, Inc. (Englewood, New Jer- occurs in lotic conditions. Experimental sey) claim to remove statoblasts and other studies of PI. fungosa in pipelines showed particles larger than 200 urn from all cm that germinating statoblasts can take hold line with a flow rate up to 1500 most easily in currents of less than 0.2 m/s; liters/minute. colony growth is inhibited at 0.6 m/s and at However, once a fouling problem has 0.9 m/s the mound-shaped colonies are developed other treatment becomes neces- swept away (APROSI 1988). Species that sary. Unfortunately, the most effective tox- form a flatter colonies, such as P. emarginata ins for controlling bryozoans also kill fish and P. reticulata, tolerate much greater water and other nontarget organisms. Sodium velocities under natural conditions. hypochlorite (commercial bleach) is proba- Few reliable experimental data are avail- bly the least offensive chemical for effec- able to guide the practitioner on methods to tively killing bryozoan colonies. For heavy control bryozoan fouling. Moreover, the growths in clean water a single static expo- wide range of situations where bryozoans are sure to 1 mg/1 for at least 5 hours is normal- a serious nuisance places a heavy reliance on ly sufficient. Occasional maintenance treat- improvisation. Colonies can usually be ments of 0.3 mg/1 over 24 hours should keep killed by 3 hours of anoxic conditions or wa- bryozoans under control. For a highly organ- ter temperatures above 35 °C. Brief expo- ic environment it may be necessary to in- sures of high ammonia levels have success- crease either the hypochlorite concentra- fully killed colonies in some wastewater tion or the exposure time. Note that these treatment plants. No species can survive treatments will kill colonies but not stato- complete desiccation, although dense blasts. colonies, like a thick carpet, will retain wa- Among heavy metals, copper is widely ter for a surprisingly long time. used to control algae, and in higher concen- Probably none of the above treatments trations it can also control bryozoans. How- will affect the dormant stages, although so ever, in most instances the necessary con- far nothing is known about the tolerances of centrations are ecologically unacceptable hibernaculae. Sometimes the simplest op- and the results are only temporary. The ef- tion is to wait for statoblasts to germinate fective concentration will vary with water and then treat the young colonies. If stato- hardness. Additives and formulations to blasts cannot be observed directly, it should make the copper more toxic to algae have be sufficient to conduct treatments once in little apparent effect on bryozoans. For Plu- the early and late spring and in early fall. mateila emarginata a 96-hour LC^ in moder- Most colonies stop growing at temperatures ately hard water has been calculated at 0.14 below 20 °C, or below 5 °C in the case of mg/1 (PARDUE 1980); in soft water the 24- Fredericetia species. Another possible option

is to pressure-spray fouled surfaces with very HASSAU. A.H. (1850): Microscopical examination of hot water, which will blast away colonies the water supplied to the inhabitants of Lon- don and suburban districts. — Samuel High- and kill the dormant stages. ley, London: 1-12. Sometimes it is possible to apply more MARSH T.G. & T.S. WOOD (1997): Report to Carollo creative strategies. For example, a golf Engineers regarding biofouling organisms at the 23"1 Avenue Wastewater Treatment Plant course in Indiana (USA) took water from a (Carollo Project No. 4300A.10 510). — Unpub- small retention pond to irrigate the turf. lished. During spring and fall the sprinklers were of- PARDUE W.J. (1980): Baseline toxicity data for fresh- ten seriously clogged with fragments of bryo- water bryozoa exposed to copper, cadmium, zoan colonies dislodged from inside the irri- chromium, and zinc. — J. Tennessee Acad. Sei. gation lines. The lake itself had a large pop- 55(1): 27-31. ulation of bryozoans (Plumatella casmiana) WOOD T. (1973): Colony development in species of growing on rocky rubble that lined the Plumatella and Fredericella (Ectoprocta: Phy- lactolaemata). — In: BOARDMAN R.S., CHEETHAM lakeshore. Masses of buoyant statoblasts A.H. & W.A. Jr. OLIVER (Eds.): Animal Colonies. formed what appeared to be a brown scum Development and Function through Time. nearly a meter wide along the windward Dowden Hutchinson & Ross, Stroudsburg, shore. The solution was not to treat the wa- Pennsylvania: 395-432. ter, but to remove the rubble. With no sub- WOOD T. (2001): Bryozoans. — In: THORP J. & A. strate on which to grow, bryozoans disap- COVICH (Eds.): Ecology and Classification of North American Freshwater Invertebrates, 2nd peared from the lake. The irrigation system ed. Academic Press, London: 505-525. was treated only once with hypochlorite and WOOD T. (2002): Freshwater bryozoans: a zoogeo- thereafter the fouling problem was resolved. graphical reassessment. — In: WYSE JACKSON P.N., BUTTLER C.J. & M. SPENCER JONES (Eds.): Bry- ozoan Studies 2001. Proc. 12th Intern. Bryozo- References ol. Assoc. Balkema, Rotterdam & Brookfield: 339-345. APROSI G. (1988): Bryozoans in the cooling water circuits of a power plant. — Verh. Intern. WOOD T.S. fi T.G. MARSH (1999): Biofouling of Vereinig. Theoret. Angew. Limnol. 23: 1542- wastewater treatment plants by the freshwa- 1547. ter bryozoan, Plumatella vaihiriae (HASTINGS, 1929). — Water Research 33(3): 609-614. BARNES R.S.K., CALOW P, OLIVE P.J.W., GOLDING D.W. & J.J. SPICER (2001): The Invertebrates: A Synthe- WOOD T. S B. OKAMURA (2005): A new key to the rd sis. 3 ed. — Blackwell Science, Oxford: 1-497. freshwater bryozoans of Britain, Ireland and Continental Europe, with notes on their ecol- CHARALAMBIDOU I., SANTAMARIA L. & J. FIGUEROLA (2003): Cristatela mucedo CUVIER 1798 (Bryo- ogy. — Freshw. Biol. Assoc. Publ. 63, Amble- zoa: Phylactolaemata) statoblasts survive side, UK: in press. duck gut passage. — Arch. Hydrobiol. 157: WOOD T.S. & L.J. WOOD (2000): Statoblast morphol- 547-554. ogy in historical specimens of phylactolae- COLLINS CM. (1978): Catfish cage culture, finger- mate bryozoans. — In: HERRERA CUBILLA A. & th lings to food fish. — Kerr Foundations, Inc. J.B.C. JACKSON (Eds.): Proc. 11 Intern. Bryozo- Publication 13, Poteau, Oklahoma: 1-31. ol. Assoc. Conf. Panama: Smithsonian Tropical Research Institute, Panama: 432-430. FOUNOROREM N.C. a J. INDEUCATO (2005): The effects of temperature and chlorine on the colo- WOOD T., ANURAKPONGSATORN P., MAHUJCHARIYAWONG nial, freshwater hydroid, Cordylophora. — J., SATAPANAJARU T, CHAICHANA R. S N. INTORN Water Research (in press). (2004): Guidebook on the use of bryozoans as bioindicators in the Mae Klong River Basin. — FREELAND J.R., NOBLE L.R. & B. OKAMURA (2000): Ge- Kasetsart University, Bangkok, Thailand: 1-39 netic consequences of the metapopulation [in Thai]. biology of a facultatively sexual freshwater invertebrate. — J. Evol. Biol. 13: 383-395.

GREENLAND D.C., NEWTON S.H. & R.F. Jr. FAUCETTE (1988): Effects of cage encrustation by the bryozoan Plumatella casmiana on production Address of author: of cannel catfish. — The Progr. Fish Culturist Dr. Timothy S. WOOD 50: 42-45. Department of Biological Sciences HAMILTON A. (1902): On the occurrence of Paludi- cella in New Zealand. — Transact. Proc. New Wright State University Zealand Instit. 35: 262-264. 3640 Colonel Glenn Highway

HARMER S.F. (1913): The Polyzoa of waterworks. — Dayton, OH 45435 USA Proc. Zool. Soc. London 1913: 426-457. E-Mail: [email protected]

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