Water temperature and freshwater macrophyte distribution

Aquatic Botany, 34 (1989) 367-373

367

Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands

WATER T E M P E R A T U R E A N D F R E S H W A T E R M A C R O P H Y T E DISTRIBUTION

EVA PIP

Department of Biology, University of Winnipeg, Winnipeg, Manitoba, R3B 2E9 (Canada) (Accepted for publication 10 January 1989)

ABSTRACT Pip, E., 1989. Water temperature and freshwater macrophyte distribution. Aquat. Bot., 34: 367373. Distributions of aquatic macrophytes and community species richness were examined in relation to water temperature at 345 sites in central North America. No significant interspecific differences were found for the monthly temperature ranges of the various macrophytes found within each of the ponds, lakes and lotic habitats during the growing season in the area studied. However, some species showed significant differences when all habitat types were pooled. Species richness was positively correlated with maximum seasonal water temperature in lakes. Temperature in itself does not appear to be an important factor governing the distribution of macrophytes within the study area, although it may operate through other site variables such as water body size and type, and through indirect effects on water chemistry.

INTRODUCTION

Temperature is known to be an important factor in macrophyte growth. It influences a variety of physiological responses such as dormancy and turion formation (Haag, 1979; Winston and Gorham, 1979; Sastroutomo, 1980), seed germination (Teltscherova and Hejn~, 1973), development (Setchell, 1946; Barko and Smart, 1981; Barko et al., 1982), photosynthetic rate (Titus and Adams, 1979; Barko and Smart, 1981) and oxygen consumption (Anderson, 1969). A number of workers have noted that growth of some species is more robust at high temperatures, although the growth cycle is compressed (Anderson, 1969; Young, 1974; Grace and Tilly, 1976; Barko and Smart, 1981 ). Sheldon and Boylen (1977) have pointed out that in many lakes the lower boundary for rooted angiosperm growth coincides with the depth of the maximum penetration of the summer thermocline. In deeper waters, low temperature may limit the length of the growing season (Moeller, 1980). Changes in the temperature regime of a water body have been reported to result in alterations of macrophyte community composition (Allen and Gorham, 1973). However, 0304-3770/89/$03.50

© 1989 Elsevier Science Publishers B.V.

368 as has been pointed out by Barko and Smart (1981), almost nothing is known regarding the influence of temperature on the distributions of individual macrophyte species. The objective of the present study was to determine whether significant interspecific differences exist with respect to water temperature for macrophytes in central North America, and whether temperature is related to community species richness within similar types of water bodies. MATERIALS AND METHODS Sampling was carried out during the M a y - S e p t e m b e r 1972-1985 seasons (except 1977 and 1979) at 345 sites located within the area bounded by 4754 °N and 94-106 ° W. All sites contained water year-round and represented a wide spectrum of trophic states. The distribution of macrophytes in the study area with respect to water chemistry has been reported elsewhere (Pip, 1979, 1987a, 1988). Each site was examined for macrophytes by dredging with a rake or using SCUBA. Search time at each site was limited to 1 h. The species of some taxa were grouped as genera because reproductive structures required for specific identification were often immature or absent. Surface water temperatures were measured with a thermometer; subsurface measurements were made with a Yellow Springs Instruments telethermometer. Temperatures were measured where the plants were growing; where plants were tall and vertically spanned several thermal strata, the maximum temperature at the top of the shoots was recorded. While most locations were visited only once, 37 sites were sampled a number of times during the season and in different years. Monthly values for these sites were included in statistical analyses. A number of sites was also visited in February 1985, in order to determine temperatures beneath the winter ice cover. Temperatures for all sites were grouped according to month. All of the different regions of the study area were represented in each month, to avoid bias that might arise from possible regional temperature differences. No significant differences in water temperature were found for the different years encompassed by the study. Sites were classified as lakes ( > 10 ha), ponds ( < 10 ha) and lotic habitats. Cochrans C and Barlett-Box F tests (Sokal and Rohlf, 1981 ) were applied to all data subjected to one-way analysis of variance in order to ensure variances were sufficiently homogeneous. The critical significance level for all statistical tests was P < 0.05. RESULTS Temperature differences between the three classes of water bodies (Table 1 ) were examined using one-way analysis of variance. Data for sites sampled once and those sampled a number of times were pooled. A total seasonal range

369 TABLE 1 Mean monthly surface water temperatures at the 3 water body types May

Ponds Lakes Loticsites

June

2

SE

n

Z

16.9 17.1 15.5

0.9 0.9 1.3

14 19.3 16 19.0 6 18.8

July 2

August

SE

n

SE

0.7 0.8 1.4

40 23.0 0.6 25 22.9 0.2 13 21.7 0.4

n

2

SE

22 20.9 0.9 91 21.1 0.5 26 19.7 0.8

September n

x

SE

27 33 22

14.7 0.4 15.1 0.4 12.9 0.6

n 37 33 17

of 0-30 ° C was encompassed by the study. The results indicated no significant differences between site classes in May ( n = 3 6 ) , June ( n = 7 8 ) or August (n -- 82 ). However, in July (n = 139), Student-Newman-Keuls multiple range tests (Winer, 1971 ) indicated that lakes showed significantly higher temperatures than lotic habitats. In September (n-- 87), both ponds and lakes showed significantly higher temperatures than lotic sites. Multivariate analysis of variance (Tatsuoka, 1971) showed that time of season (month) was the most important factor affecting water temperature (F--- 80.6, P < 0.001, n = 422), while water body type was less important, but still significant (F= 4.3, P = 0.014, n = 422 ). There was no significant tendency for any water body class to be overor under-represented in the sampling program in any particular month (F=0.25, P=0.98, n=422). Winter water and bottom sediment temperatures below the ice cover of 0.75> 1 m thickness ranged from 0 to 5 ° C at different site types, with the warmest temperatures generally located in the sediments. It was not unusual to find green, living, submerged macrophyte shoots at these temperatures under the ice cover in late winter in some lakes. The mean temperatures at which the more common species or genera were found in each summer month are given in Table 2. Differences among species were examined for each month and water-body class individually using 1-way analysis of variance and Student-Newman-Keuls multiple range tests. None of the interspecific differences was significant for any month within any of the three water body classes. However, when all water body classes were pooled, significant interspecific differences were found for May (F ratio=l.66, P=0.018, n=182), June (F ratio---1.69, P--0.003, n--482), July (F ratio=1.43, P=0.025, n=1230) and September (F ratio=l.46, P=0.029, n= 551 ). In May, a significant difference was identified only between Potamogeton foliosus Raf. and P. pectinatus L. In June, significant differences were identified between P. foliosus and each of P. pectinatus and P. richardsonii (Benn.) Rydb. and between Sium suave Walt. and each of P. pectinatus and P. richardsonii. In July, P. praelongus Wulfen contrasted with each of Hippuris vulgaris L., Callitriche spp., P. pusillus L. and P. vaginatus Turcz. August was

370 TABLE2 Mean m o n t h l y w a t e r t e m p e r a t u r e s observed for each species in the study area May 2

Potamogeton ampli[olius T u c k e r m . P. epihydrus Raf. P. foli[ormis Pets. P. filiosus Raf. P. friesii Rupr. P. gramineus L. P. natans L. P. obtusifolius Mert. & K o c h P. pectinatus L. P. praelongus Wulfen P. pusillus L. P. richardsonii ( B e n n . ) Rydb. P. robbinsii Oakes P. spiriUusTuckerm. P. vaginatusTurcz. P. zosteriformisFern. Charaspp. Sparganiumspp. Ruppia maritima L. Najasflexilis (Willd.) Rostk. &

June

July

August

September

SE

n

x

SE

n

2

SE

n

2

SE

n

x

SE

n

-

13 2 1 6 1 1 2 4 7 8 5 4

22.9 17.4 19.6 22.4 20.1 19.0 21.8 19.2 19.9 18.2 23.3 18.2

23.8 22.6 23.3 22.5 23.7 23.5 22.5 23.1 23.0 24.3 21.7 22.9 25.0 23.8 21.8 22.9 23.2 22.4 23.0 23.4

0.6 0.7 0.4 0.7 0.5 0.4 0.4 0.8 0.4 0.5 0.4 0.3 1.5 1.2 0.5 0.4 0.4 0.4 0.6 0.5

19 16 16 23 22 38 32 7 32 22 12 74 5 6 16 39 39 41 9 34

21.3 20.6 20.4 22.5 20.8 22.2 20.3 21.6 20.5 23.0 20.6 18.0 23.3 19.2 22.2 20.4 25.0 20.6

0.9 1.2 1.4 1.0 2.6 0.7 0.9 1.2 0.7 0.6 2.7

23 4 13 17 3 22 4 9 28 3 3

0.4 0.8 0.6 0.4 0.9

29 10 10 34 4

0.8 1.0 0.9 1.2

16 15 24 1 10

13.3 17.5 12.0 14.2 12.3 14.5 13.4 15.1 14.0 15.1 15,1 15.8 14,8 14,3 14,0 13,9 12.3 14.1

9 2 1 13 3 13 15

1.0 0.5 1.6 1.0 2.1 1.2 1.1 1.1 2.1

3 7 3 13 2 17 8 18 5 10 18 4 2 3 9 19 28 2 6

0.8 0.5 0.9 1.5 0.5 0.7

18.2 20.5 15.0 17.5 13.0 17.0 22.0 14.3 17.0 15.9 19.5 14.3

2.5 1.6 1.9 0.5 3.8 0.9 1.6 0.8 1.6 1.4 1.1 2.7 1.0 2.6 1.8 0.8 0.8 0.3 1.5

7 20

3

17.0 19.7 22.7 15.8 23.8 19.0 18.3

1.4 0.7

14.8

0.5 2.7

0.9 0.6 0.5 0.6 2.3 0.7

7 20 27 18 3 12

15.0 15.5 12.0 17.0 14.8 16.1 18.5 16.0 16.6 -

0.5 2.0 1.0 2.7 1.6 1.5 1.0 1.2 -

4 4 3 1 3 6 2 7 11

20 49 28 30 12 30 13 37 27 26 37 57 11 14 12 39 14 13 83 15 23 14 18 9 51 19 4

21.1 19.8 18.3 21.2 20.5 19.6 20.5 20.6 20.1 20.2 18.5 20.2 20.2 18.7 25.5 21.2 19.8 21.3 20.7 18.7 18.5 20.2 20.1 18.9 20.3 19.4 19.8

1.1 0.8 0.8 1.0 0.9 0.6 1.2 0.9 1.1 0.8 0.6 0.7 1.6 1.3 0.5 1.0 2.0 1.2 0.7 1.9 0.8 1.1 0.9 1.5 0.8 1.4 1.0

14 22 12 11 12 23 6 22 18 17 19 37 5 3 2 19 6 12 33 7 11 5 14 7 27 11 8

18 17 3 11 26 4 2

0.9 1.0

11 9

0.4 0.8 0.6

42 7 8

0.9 0.8 -

0.6 0.3 0.6 0.5 0.7 0.4 0.7 0.3 0.5 0.5 0.4 0.3 0.8 0.6 0.6 0.4 0.7 0.7 0.3 0.5 0.5 0.5 0.6 0.7 0.3 0.7 2.4

0.5 0.6 1.5 0.7 0.5 1.0 0.5

14.0 15.6 11.9 10.0

22.1 22.5 22.7 23.0 23.5 22.6 22.7 22.8 22.4 23.1 22.3 22.8 23.6 24.0 23.5 23.1 23.3 21.3 22.5 21.0 22.2 22.2 22.5 22.7 22.6 22.6 21.3

12 20 32 21 8 8

0.9 2.0 1.4 0.8 1.2 1.6

16 15 8 7 7 19 7 18 14 5 9 21 3 2 11 5 2 35 12 22 8 5 3 32 6 1

0.6 0.5 0.4 0.5 1.0 1.1

15.5 17.0 15.4 13.5 15.0 17.3 21.0 17.5 18.0

0.9 1.3 1.6 1.5 1.6 0.8 2.0 1.2 1.6 2.8 1.5 1.1 1.2 4.0 1.6 1.0 0.3 0.8 1.0 0.9 1.2 1.1 2.1 0.8 1.2 -

0.7 0.5 0.7 0.8 0.7

5 2 16 15 10

17.0 12.5 18.0

1 9 1 -

Schmidt

Alisma triviale P u r s h Sagittaria spp. Elodea canadensis Michx. VaUisneria americana Michx. Zizania aquatica L. Eleocharis spp. CaUapalustris L. Lemna minor L. L. trisulca L. Spirodelapolyrhiza (L.) Schleid. Polygonum amphibium L. CeratophyUum demersum L. Nymphaea odorata Ait. N tetragona Georgi Nuphar microphyUum (Pers.) Fern. N. variegatum Engelm. Ranunculus aquatilis L. CaUitriche spp. Myriophyllum exalbescens Fern. Hippuris vulgaris L. Slum suave Walt. Mentha arvensis L. Utricularia intermedia H a y n e U. minor L. U. vulgaris L. Megalodonta beckii ( T o r r . ) G r e e n e ZostereUa dubia Jacq.

19.6 20.9 17.7 20.1 17.8 18.7 21.0 19.1 20.0 19.2 17.3 16 18.8 1 15.7

18.0 4 20.8 3 16.7 1 18.3 24 20.9 1 17.8 4 16.7 3 17.9 15.8 1 18.1 9 18.6 4 16.6 1 14.0

13.5 13,6 14.7 14,5 12,2 13.5 13.6 14.0 12.2 13.9 14.6 14.8 14.5 12.5 13.2 -

15.1 13.4 13.3 13.3 16.5 13.4 13.4 15.8

371 associated with no significant differences, but in September Zosterella dubia Jacq. was found at significantly higher temperatures than Zizania aquatica L. Macrophyte species richness was examined by m o n t h in each of the waterbody classes. Species richness was significantly positively correlated with temperature only in July in lakes (r--0.22, P= 0.015, n--95 ), when water temperatures reached the seasonal maxima. Thus, the warmest lakes also tended to show the greatest numbers of macrophyte species. DISCUSSION

It has been suggested (e.g. Barko and Smart, 1981 ) that different species of macrophytes may differ with respect to their ranges of thermal tolerance, which may in turn affect the geographical ranges of various macrophytes. Although interspecific differences could not be demonstrated within any given waterbody type in the present study, some differences emerged when all sites were prefpooled. These differences were due in some cases to different water body tolerances of certain species (Pip, 1979, 1987a,b) and the temperature differences seen for the respective water body types in July and September. However, in other cases, differences were seen as a result of the increased numbers of samples when sites were pooled. The results of the present study showed that, while at some times of the year some species occupied habitats that were distinctly colder than those of other species, these differences did not remain consistent throughout the growing season. Because of the wide ecological temperature tolerances of most of the species examined, none of the taxa could be classed as either cold- or warmwater types within the area studied. While temperature may have operated indirectly through its effects on variables such as pH and other chemical variables, since many of the macrophytes in the area show well-defined ecological ranges with respect to water chemistry (e.g. Pip, 1979, 1987a,b) temperature did not in itself appear to influence the geographical distributions of individual species, in terms of limiting the sites where any given species could occur. Of course, it was still possible that some of the rare species occurring in the region may have had thermal restrictions, but these could not be examined statistically owing to low sampling numbers. A number of species, e.g. Potamogeton foliosus, P. gramineus L., P. natans L., P. pectinatus, P. pusiUus, P. richardsonii, Chara spp., Alisma triviale Pursh, Lemna minor L., L. trisulca L., CeratophyUum demersum L., Callitriche spp. and MyriophyUum exalbescens Fern., were observed in shallow ponds where the surface temperature was as high as 30 ° C. However, ponds were also the most strongly vertically stratified, where a difference of as much as 11.5°C could be observed in the first 0.5 m below the surface on a calm hot day. Thus larger rooted macrophytes reaching the surface in such habitats experienced a wide range of temperature throughout the length of their shoots, although the

372 r e p r o d u c t i v e o r g a n s were e x p o s e d to t h e highest t e m p e r a t u r e s . A n u m b e r of w o r k e r s (e.g. A n d e r s o n , 1969; S t a n l e y a n d N a y l o r , 1972; T i t u s a n d Adams, 1979 ) have r e p o r t e d t h a t some m a c r o p h y t e s can w i t h s t a n d w a t e r t e m p e r a t u r e s as high as 35 °C a n d m a i n t a i n high rates of p h o t o s y n t h e s i s . Since differences b e t w e e n t h e t e m p e r a t u r e ranges o f t h e various species were m i n o r , species richness was also relatively u n a f f e c t e d b y t e m p e r a t u r e . T h e correlation between m a x i m u m s u m m e r t e m p e r a t u r e s a n d species richness in lakes m a y have b e e n r e l a t e d to t h e fact t h a t t h e w a r m e s t lakes were also t h e m o s t shallow a n d n u t r i e n t - r i c h , a n d t h e r e f o r e p r o v i d e d the greatest n u m b e r of niches a n d r o o t i n g areas for m a c r o p h y t e s . T h u s , t e m p e r a t u r e in itself a p p e a r s to be relatively u n i m p o r t a n t in determ i n i n g species d i s t r i b u t i o n o f m a c r o p h y t e s w i t h i n the s t u d y area. It is likely t h a t o t h e r variables, such as depth, light availability, b o t t o m s u b s t r a t e type, t u r b u l e n c e a n d w a t e r c h e m i s t r y (e.g. K a d o n o , 1982; Pip, 1987a,b, 1988) are the p r i m a r y g o v e r n i n g factors for m a c r o p h y t e d i s t r i b u t i o n in the s t u d y area. REFERENCES Allen, E.D. and Gorham, P.R., 1973. Changes in the submerged macrophyte communities of Lake Wabamun as a result of thermal discharge. Proceedings of the Symposium on the Lakes of Western Canada, University of Alberta, Edmonton, pp. 313-324. Anderson, R.R., 1969. Temperature and rooted aquatic plants. Chesapeake Sci., 10: 157-164. Barko, J.W. and Smart, R.M., 1981. Comparative influences of light and temperature on the growth and metabolism of selected submersed freshwater macrophytes. Ecol. Monogr., 51:219235. Barko, J.W., Hardin, D.G. and Matthews, M.S., 1982. Growth and morphology of submersed freshwater macrophytes in relation to light and temperature. Can. J. Bot., 60: 877-887. Grace, J.B. and Tilly, L.J. 1976. Distribution and abundance of submerged macrophytes including MyriophyUum spicatum L. (Angiospermae) in a reactor cooling reservoir. Arch. Hydrobiol. 77: 475-487. Haag, R.W., 1979. The ecological significance of dormancy in some rooted aquatic plants. J. Ecol., 67: 727-738. Kadono, Y., 1982. Distribution and habitat of Japanese Potamogeton. Bot. Mag., Tokyo, 95: 6376. Moeller, R.E., 1980. The temperature-determined growing season of a submerged hydrophyte: tissue chemistry and biomass turnover of Utriculariapurpurea. Freshwater Biol., 10:391-400. Pip, E., 1979. Survey of the ecology of submerged aquatic macrophytes in central Canada. Aquat. Bot., 7: 339-357. Pip, E., 1987a. The ecology of Potamogeton species in central North America. Hydrobiologia, 153: 203-216. Pip, E., 1987b. Species richness of aquatic macrophyte communities in central Canada. Hydrobiol. Bull., 21: 159-165. Pip, E., 1988. Niche congruency of aquatic macrophytes in central North America with respect to 5 water chemistry parameters. Hydrobiologia, 162: 173-182. Sastroutomo, S.S., 1980. Environmental control of turion formation in curly pondweed (Potamogeton crispus ). Physiol. Plant, 49: 261-264. Setchell, W.A., 1946. The genus Ruppia. Proc. Calif. Acad. Sci., 25: 469-478. Sheldon, R.B. and Boylen, C.W., 1977. Maximum depth inhabited by aquatic vascular plants. Am. Midl. Nat., 97: 248-254. Sokal, R.R. and Rohlf, F.J., 1981. Biometry. W.H. Freeman, New York, NY, 859 pp.

373 Stanley, R.A. and Naylor, A.W., 1972. Photosynthesis in Eurasian watermilfoil (MyriophyUum spicatum L.). Plant Physiol., 50: 149-151. Tatsuoka, M.M., 1971. Multivariate Analysis: Techniques for Educational and Psychological Research. Wiley, New York, NY, 310 pp. Teltscherova, L. and Hejn~, S., 1973. The germination of some Potamogeton species from SouthBohemian fishponds. Folia Geobot. Phytotaxon., 8: 231-239. Titus, J.E. and Adams, M.S., 1979. Coexistence and the comparative light relations of the submersed macrophytes MyriophyUum spicatum L. and VaUisneriaamericana Michx. Oecologia, 40: 273-286. Winer, B.J., 1971. Statistical Principles in Experimental Design. McGraw-Hill, New York, NY, 907 pp. Winston, R.D. and Gorham, P.R., 1979. Turions and dormancy states in Utricularia vulgaris. Can. J. Bot., 57: 2740-2749. Young, C.A., 1974. The effects of temperature and other environmental factors on standing crop and phenological development of MyriophyUum spicatum L. Master's Thesis, University of Tennessee, 100 pp.