Settling Plates of Cold-Cure Acrylic Plastic Replicated from Natural Surfaces

Settling Plates of Cold-Cure Acrylic Plastic Replicated from Natural SurfacesAuthor(s): Michael J. RiskSource: Limnology and Oceanography, Vol. 18, No. 5 (Sep., 1973), pp. 801-802Published by: American Society of Limnology and OceanographyStable URL: http://www.jstor.org/stable/2834212 .

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NOTES 801

Settling plates of cold-cure acrylic plastic replicated from natural surfaces'

ABSTRACT

"Formatray," a strong inert, cold-cure dental acrylic, seems to satisfy most of the requirements of an ideal settling plate ma- terial. Field tests show rapid colonization, with no systematic exclusion of particular groups of organisms.

Many different substances have been used in the field and in the laboratory as substrates for colonizing communities of plants and animals. Excellent reviews are given by Slade6kova (1962) and Cooke (1956).

Recent work using a broad range of materials (Cairns et al. 1969; McIntire and Wulff 1969; Fager 1971) has emphasized one of the continuing problems of such studies, that "the nature of most artificial surfaces used bears no relation to the surfaces of natural hosts" (Tippet 1970, p. 198). The species makeup of settling communities is important as an indicator of water quality and in studies of the succes- sional process. Each of the three main types of substrate now in use, glass plates, asbestos, and plastics, suffers from some drawback. Pomerat and Weiss (1946) and Risk (1972) have commented on low growth levels on smooth glass plates, and Tippet (1970) has shown populations developed on glass slides to be different from natural populations. Asbestos board is difficult to procure in a variety of surface textures and may, due to the fibrous nature of the silicate mineral itself, present an un- natural situation: Barnes and Powell (1950) noted that projection of glass filaments from "staple cloth" fiber glass inhibited

1 Field assistance was provided by the staff of the Santa Catalina Marine Biological Laboratory and technical information by the Detroit Research Department of Kerr Manufacturing Company. This work was financially supported by the National Research Council of Canada and the McMaster University Divisional Research Board. Contri- bution No. 9 from the Santa Catalina Marine Bio- logical Laboratory.

larval settling. Plastics in general seem to be the best choice, providing they are inert, but there is difficulty in producing a surface texture similar to a natural substrate.

"Formatray" (Kerr Manufacturing Co.) is a cold-cure dental acrylic used for mak- ing custom trays. It comes as a powder- liquid pair, which on mixing becomes a hard and rigid mass of poly-methylmethac- rylate (Civjan et al. 1971). Formatray can be mixed at various powder: liquid ratios, so that it can be formed by hand or poured into molds; its physical properties are good in a wide range of powder to liquid ratios (Civjan et al. 1971) and it passes American Dental Association speci- fications for cold-curing polymers, having high tensile and compressive strength, and low porosity, sorption, and solubility.

My settling plates were made by pouring mixed Formatray into latex rubber impressions of various surfaces. Latex impressions can successfully be made of almost any natural surface; I have recently produced a series of impressions of artificial sandstones, made by lithifying various size grades of sand with polyester resin. Formatray has about 40% calcium carbonate filler ma- terial and chemically approximates a calcareous sandstone or siltstone. A virtu- ally unlimited number of plates can be poured up from one latex impression, thus allowing the operator to place identical plates in different locations or a series of plates, chemically identical and texturally different, in one location.

In the field, plates are colonized rapidly and support heavy growths of algae and invertebrates. In a preliminary study in Big Fisherman's Cove, Santa Catalina Island, California, plates set out in shallow water picked up the most common algae settling on rocks in the area (B. Setzer, personal communication). Colonizing as- semblages are similar to those developed on fresh rock surfaces nearby. So far, 41 species of algae and at least 11 species of invertebrates have been identified growing



802 NOTES

on these plates; there seems to be no selec- tive exclusion of groups.

I have used several types of cold-cure acrylic; Formatray is the best so far. It is normally pure white, but can be dyed easily. The only problem is cost; at normal retail prices each of my artificial plates, 14.1 x 14.1 cm (1/50 m2) and 0.6-0.7 cm thick, costs about $1.00.

MICHAEL J. RISK

Department of Geology McMaster University Hamilton, Ontario

REFERENCES

BARNES, J., AND H. T. POWELL. 1950. Some observations on the effects of fibrous glass surfaces upon the settlement of certain sedentary organisms. J. Mar. Biol. Ass. U.K. 29: 299-302.

CAIRNS, J., JR., M. L. DAHLBERG, K. L. DICKSON, N. SAnTH, AND W. T. WALLER. 1969. The relationship of freshwater protozoan communities to the MacArthur-Wilson equilibrium model. Amer. Natur. 103: 439-454.

CIVJAN, S. T., V. RAPHELD, AND R. L. RICHARD-

SON. 1971. Suitability of commercial cold- curing resins for direct intraoral splinting. J. Amer. Dental Ass. 83: 1058-1062.

COOKE, W. B. 1956. Colonizing of artificial bare areas by microorganisms. Bot. Rev. 22: 613-638.

FAGER, E. W. 1971. Pattern in the development of a marine community. Limnol. Oceanogr. 16: 241-253.

MCINTIRE, C. D., AND B. L. WULFF. 1969. A laboratory method for the study of marine benthic diatoms. Limnol. Oceanogr. 14: 667-678.

POMERAT, C. M., AND C. M. WEISS. 1946. The influence of texture and composition of surface on the attachment of sedentary marine organisms. Biol. Bull. 91: 57-65.

RIsK, M. J. 1972. Intertidal substrate rugosity and species diversity. Ph.D. thesis, Univ. S. Calif., Los Angeles. 70 p.

SLADECKOVA, A. 1962. Limnological investiga- tion methods for the periphyton ("Aufwuchs") community. Bot. Rev. 28: 286-350.

TIPPET, R. 1970. Artificial surfaces as a method of studying populations of benthic micro- algae in fresh water. Brit. Phycol. J. 5: 187-199.

Submitted: 20 February 1973 Accepted: 20 June 1973

Preparation of filtered plankton and detritus for study with scanning electron microscopy'

ABSTRACT

A simple, rapid method of fixing plankton and detritus for the scanning electron microscope is described, which can be used in the laboratory or in the field. The sample is fixed with 2% glutaraldehyde followed by stepwise dehydration in increasing concentrations of ethyl alcohol. Fixed samples can be stored for up to 2 weeks. Critical point drying of the fixed samples is done in the laboratory. Nuclepore filters proved superior to other filters for most sample preparations.

Scanning electron microscopy (SEM) has recently been applied to the study of aquatic bacteria, phytoplankton, and detritus (Schrader 1971; Paerl and Goldman 1972; Paerl 1973). Its most notable use is in describing and differentiating frustules

1 This study was supported by NSF-RANN Grant GI-22.

of diatoms (Round 1970). This communication describes a method by which in situ plankton can be prepared for SEM ob- servation.

We thank J. Pangborn for his advice on the operation of the scanning electron microscope. C. R. Goldman, R. L. Leonard, and A. F. Carlucci critically reviewed the manuscript and M. Smith aided in its preparation.

METHODS

Filtered lake (Tahoe) and seawater (off Scripps Institution pier) samples have re- ceived most attention. However, dense suspensions of periphyton, plankton, or sediments fixed before filtration have also been studied.

Several types of 2.4-cm-diameter filters were used: glass-fiber filters (Whatman GFA and GFC), membrane filters made of



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Settling Plates of Cold-Cure Acrylic Plastic Replicated from Natural Surfaces