Tide Pool Transect
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Tide Pool Transect By WILLIAMB. NUTTING,ROBERT ZOTTOLI, and ALTONH. GUSTAFSON Downloaded from http://online.ucpress.edu/abt/article-pdf/33/5/282/28168/4443463.pdf by guest on 01 October 2021 D uring the past seven years at the Bowdoin Col- transect. In one area that we have used for class lege Marine Institute for High School Teachers we studies we have at least six adequate rock pools have tried many methods of gathering meaningful located at different levels above the mean low-tide data on marine ecology. Ecologic studies both above mark. Analysis of these pools for species diversity (eulittoral: rock, sand, and mud substrates) and be- reveals that if only two pools and the ocean edge low (sublittoral) the intertidal zone have been in- were available we would still be able to show ad- teresting and useful, but none of these has proved equate ecologic differences. as intellectually stimulating and enlightening as our Our most troublesome situation for site selection work on the tide pool transect. We call this a tide has been the problem of wave wash at the ocean pool transect since we establish a line (much as a edge. Some control over this may be achieved by transect) from ocean edge through or beside several selecting a shore station that fronts at an acute angle tide pools and sample each tide pool along the line. to the wash of the wave pattern. Sites on shore may This method of study, with some added refinements, be particularly dangerous during periods of onshore has also been found successful by one of us (Zottoli) winds or in areas where there is a big difference for a college class in marine biology. From our ex- between high and low tide; in the Bay of Fundy, periences it seems apparent that this procedure for example, where the tidal range may be 8 m or should have wide applicability as a teaching tool in more, the velocity and force of the incoming water studies of the intertidal zone. is exceptionally great. It is a good plan to have a Although this report is based on studies of rock throw-ring life preserver on hand as well as a substrate tide pool, the procedures and suggestions (mandatory!) first aid kit. Workers would be well should be useful for any area where a series of tide- advised to wear cleat-bottomed sneakers or boots. water pools is available. Timing is important, especially if one is to do anv extensive ecologic study on tide pools. As a handy Site Selection and Timing index one can say that the study should be started Along the Maine coast one experiences little dif- at a low-tide time (refer to tide tables published by ficulty in locating an adequate site for a tide pool the Environmental Science Services Administration) minus the length of time required to complete the shore station analysis. Thus, if low tide occurs at Authors' addresses: William B. Nutting-Zoology Dept., University of Mas- 3 P.M. and it takes 30 minutes to complete analysis sachusetts, Amherst, Mass. 01002. of the low-tide shore station, one should start sam- Robert Zottoli-Biology Dept., Fitchburg State College, pling at 2:30 P.M. (see procedure below). Much Fitchburg, Mass. 01420. greater exposure, and usually more tide pools, can Alton H. Gustafson-Biology Dept., Bowdoin College, be obtained if one selects for low tides rather Brunswick, Maine 04011. (His work as director of the Bow- spring doin College Marine Institute has been supported by Na- than for neap tides. Excellent contrasts may be ob- tional Science Foundation grants.) tained if the tide pool series is sampled at low tide 282 THE AMERICANBIOLOGY TEACHER, MAY 1971 one afternoon and then again, 12 hours later, at low The sequence of sampling for a general picture of tide early in the morning, preferably before sunrise. the ecology of the pools should follow some pre-set One of us (Zottoli) has been successful in studying pattern, such as the following: tide pools at intervals for a 29-hour period (table 2). 1. Discussion (and note-taking) at the station of If, as is the case in many parts of the world, you the general characteristics of the pool, noting es- have an area where the total tidal sweep is small pecially any wind disturbance or current action in (0.5-m amplitude in Florida vs. a 3-m amplitude in the pool, evidences of decay, stagnation, or pollu- Brunswick, Maine) you may have to replace the tion, and distribution of flora and fauna. tide pool transect with a transect line that either 2. Temperature measurements of air, water (sur- crosses a spit or narrow isthmus with differing con- face, mid-, and bottom depths), and rock surface (in ditions on each side or one that parallels the shore and out of the pool). A simple thermometer on a yet embraces a variety of substrates (mud, sand, string, if retrieved rapidly, will suffice for most rock). pools. For very deep pools take the temperature of Site selection for any transect should be based as water sample as in step 4, below. closely as possible on freedom from traffic. An area 3. Sampling for chemical tests. Several inex- exposed to heavy people-pressure is often deranged pensive kits are available commercially; they are for flora and fauna. relatively foolproof for student use in testing for Downloaded from http://online.ucpress.edu/abt/article-pdf/33/5/282/28168/4443463.pdf by guest on 01 October 2021 oxygen concentration and pH. Inexpensive hydro- Location of Stations meters (urine hydrometers, for example) can be Individual tide pools in the tide pool series should used to determine the specific gravity of sea water. be positioned at markedly different levels and situ- Specific gravity may then be converted to salinity, ated, if possible, along a straight line extending, at using Watanabe's conversion tables. All test results right angles to the shore line, from the low-tide line should be repeated three times and the average to the top of the eulittoral zone. Our results with recorded. classes at Bowdoin indicate that a fine series of con- 4. Subsurface samples for chemical tests and trasts can be found with one shore station, one sta- planktonic organisms should be obtained in a se- tion at 1 m, one station at 2 m, one station at 2.5 m, quence from surface down so that the characteristics and one station at 4.5 m above mean low water (high of the samples in each layer are undisturbed. They tide, here, is approximately 3 m). If the class making should also be taken by one of a variety of instru- the study is large or unusually energetic, any or all ments, such as a Kemmerer sampler, which ensnares of the stations can be replicated (two shore, two at the sample without mixing it with air (Nutting, 1 m, etc.), providing useful comparison data and 1966). Perform the tests at once and record in chart serving as a valuable check on results. This also, as form (as in table 1). Preserve planktonic organisms we have found, introduces a healthy between-group in well-labeled plastic vials. competitive spirit. 5. Rough measurement and sketch of the pool. If It is the sad situation that in these days of popula- depth contours are made, an estimate of pool volume tion pressure the tide pool area should be prechecked can be derived. The type of rock and its mineral for fouling. Since the fouling is often of human in- characteristics should also be noted, since these may testinal origin, an instructor should be alert to the well determine the pH of the pool. disease potential. Although as highly instructive as a 6. Make quantitative counts (numbers/standard polluted-nonpolluted study might be, such could be area) of dominant species. Select for this "first run" disastrous unless the instructor is prepared to use only large, easily evident organisms. Many marine sanitary technique in working polluted pools. algae are permanently attached to the substrate and therefore should be counted in the pool. For algae, Sampling Procedure ''percent cover" within the standard area may be We have indicated above that for safety's sake the best way to record distribution. Organisms that sampling should be done during the outgoing tide. are not permanently attached may be removed from If the instructor can plan a full-day study, he can the pool, counted, and then returned. As you make begin at high tide and sample, at hourly intervals, your counts be sure to note the distribution of each each tide pool as it becomes exposed. This procedure species within the standard sampling area and within has the following advantages: (i) all students have the pool. If certain species are not known, assign time to investigate each tide pool, and (ii) the time each a number and bring a specimen of each to the of pool exposure at examination time is the same laboratory for identification. Since specimens may for each pool. In this case the shore station is sam- best be identified in the living state it is important pled last, just before low tide. The timing procedure to keep them cool, shaded, and aerated. Only one or recommended in site selection demands, unless the two specimens of very common species should be study is somewhat superficial, that separate groups pickled (70% alcohol or 1: 9 commercial formalin to examine each pool or shore station. In revisiting the sea water). area for successive studies it is important in either 7.