- Email: [email protected]
Leaf dimensions of transplants of Thalassia testudinum in a Mexican Caribbean reef lagoon
A.quatic m)tany ELSEVIER
Aquatic Botany 55 (1996) 133-138
Short communication
Leaf dimensions of transplants of Thalassia testudinum in a Mexican Caribbean reef lagoon Brigitta I. van Tussenbroek
1
Estacidn Puerto Morelos, lnstituto de Ciencias del Mar y Limnologfa, Universidad Nacional Autdnoma de M~xico, Apdo. Postal 1152, Cancan, 77500 Q.Roo, Mexico
Accepted 6 May 1996
Abstract Thalassia testudinum Banks ex KSnig in a Mexican Caribbean reef lagoon showed considerable differences in leaf length and width between three sampling stations. A reciprocal transplantation experiment between these stations was completed in July 1991. After one and a half years of observation, no significant differences in leaf length were recorded among the transplants from different origins. Although differences in leaf width diminished between the transplants from different origins, leaf width showed less plasticity than leaf length, and at one station, significant small differences were still evident after 2 years. Keywords: Seagrass; Thalassia testudinum; Leaf morphology;Spatial variability; Transplantation
1. I n t r o d u c t i o n Spatial variability in leaf morphology of seagrasses is determined by environmental factors such as nutrient conditions (Short, 1987; Powell et al., 1989; Erftemeijer, 1994; P&ez et al., 1994), depth or light conditions (Strawn, 1961; Phillips, 1974; Phillips and Lewis, 1983), sediment depth (Zieman, 1972) and wave action (Patriquin, 1973). However, it is not certain to what degree this spatial variability in leaf morphology is environmentally or genetically controlled. If the environment is modified, for example by fertilization, leaf length or both leaf length and width are known to increase (Powell et al., 1989; P~rez et al., 1994). Z o s t e r a m a r i n a L., transplanted along depth gradients, showed in some cases a similar width to local plants, whereas in others, leaf width of the
~Tel.: (+ 52-5)-6228596 (satellite); fax: (+ 52-987)-10138; e-mail: [email protected]. 0304-13770/96/$15.00 Copyright © 1996 Elsevier Science B.V. All rights reserved. PII S0304-3770(96)01068-6
134
B.Lv. Tussenbroek /Aquatic Botany 55 (1996) 133-138
transplants remained different from that of the local population (Phillips and Lewis, 1983), suggesting both environmental and genetic control of leaf morphology. However, spatial differences in leaf morphology of two species of Halophila and two species of Halodule in Australia (McMillan, 1983) and of Posidonia oceanica (L.) Delile in the Mediterranean (Meinesz et al., 1993) were primarily environmentally controlled. As for the turtle grass, Thalassia testudinum Banks ex K~nig, Phillips and Lewis (1983) failed to show phenotypic flexibility over a depth gradient, as the plants died when transplanted to deeper areas. Leaves of Thalassia testudinum in the Puerto Morelos reef lagoon showed an approximate 2.5-fold difference in length, and 1.5-fold difference in leaf width, depending on the sampling site (Van Tussenbroek, 1995). These large differences in leaf dimensions within a small sampling area presented a good opportunity to test, by means of transplantation experiments, whether differences in leaf length and width are inherent to the plants or whether they are principally determined by environmental factors.
2. Materials and methods
Three sampling stations were sited in well developed Thalassia testudinum beds within differing environments in the Puerto Morelos reef lagoon, Mexican Caribbean (21°51' N). Principal differences between sampling sites were sources of external nutrient input and degree of exposure to waves. The lagoon station was approximately 30 m offshore near undersea mangrove discharges at a depth of 4.5 m; the coastal station was situated in an approximately 30-m-wide coastal fringe at the edge of the seagrass meadow where dead material accumulated (depth 2.5 m); and the back reef station was situated in a relatively wave-exposed back reef area far removed from any source of external nutrient input (depth 2.5 m). In July 1991, a reciprocal transplantation experiment was initiated between the three sampling stations. At each station, three core samples (diameter 20 cm) were taken, one of each was placed at each station and marked with a hoop. The length and width of the longest blade of each shoot were measured at monthly intervals until October or November of the same year. From January 1992 until July 1993, these characteristics were measured twice annually. In October 1991, the hoops indicating the location of the transplants were lost at the lagoon station, and further observations were discontinued at this station. A one-way ANOVA was used to compare the mean lengths and widths of the transplants from different origins. Leaf length data were log transformed to approach homogeneity of variance (Zar, 1984).
3. Results
All Thalassia testudinum leaves showed a decrease in leaf dimensions in the following months after transplantation (Figs. 1 and 2). At the lagoon station, plants were lost after 4 months, and at this station, observations were discontinued after the initial period of decline in leaf dimensions. At the coastal and back reef stations, leaves of the
B.I.o. Tussenbroek / Aquatic Botany 55 (1996) 133-138
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Fig. 1. Thalassia testudinum mean leaf length measured during the transplantation experiment at the three receptor stations in the Puerto Morelos lagoon. Shaded area represents period of twice-yearly measurements. Bars represent standard error.
transplants from different origins gradually reached similar lengths (Fig. 1). In January and July 1993, no significant differences in leaf length were recorded between the transplants at the coastal station ( F = 1.71, P = 0.19, d.f. = 68 and F = 2.40, P = 0.10, d.f. = 69 for January and July 1993, respectively), and at the back reef station ( F = 1.40, P = 0.25, d.f. = 102 and F = 0.05, P = 0.95, d.f. = 104 for January and July 1993,
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Fig. 2. Thalassia testudinum mean leaf width measured during the transplantationexperiment at the three receptor stations in the Puerto Morelos lagoon. Shaded area represents period of twice-yearlymeasurements. Bars represent standard error.
respectively). Leaf width remained significantly different origin at the coastal station until July Fig. 2), although differences were small. At transplants attained a similar width at the end P --- 0.09, d.f. = 104; Fig. 2).
different between the transplants from 1993 ( F = 6.67, P = 0.002, d.f. = 69; the back reef station, leaves of the of the observation period ( F = 2.48,
B.l.v. Tussenbroek / Aquatic Botany 55 (1996) 133-138
137
4. Discussion The sudden decrease in leaf length, and to a lesser degree, in leaf width, immediately after the onset of the experiment were most likely an effect of transplantation, and 5 months to 1 year were necessary for recovery (Fig. 1). These results suggest that, with the increasing use of mesocosms for seagrass studies (Short, 1987; Tomasko and Lapointe, 1991; Burkholder et al., 1994; Short et al., 1995), a possible acclimation period of transplants should be taken into account. Short (1985) reported little changes in plant abundance and leaf morphology after transplantation of plugs of Thalassia testudinum from shallow environments to culture tanks; however, he did not present quantitative data. Fuss and Kelly (1969), in accordance with the findings of this study, reported a decline of leaf weight for T. testudinum transplants when placed in a throughflow sea-water system, and that the plants required a full year for complete recovery. Leaf width is considered to be an indicator of environmental stress (Phillips and Lewis, 1983) and generally, leaf width is used as a parameter for assessment of the effect of transplantations (Phillips, 1974; Phillips and Lewis, 1983; Meinesz et al., 1993). However, leaf length as well as leaf width was included in this study, as differences between T. testudinum at the stations were characterized by variations in both leaf dimensions. Leaf length showed a slightly greater plasticity than leaf width, as the lengths of plants from different origins were similar at both stations after 1.5 years. Plants of different origins only reached similar widths after 2 years at the back reef station, and they remained significantly different (at P = 0.05) at the coastal station at the conclusion of the experiment after 2 years. Thus, T. testudinum in the Puerto Morelos lagoon showed phenotypic plasticity in leaf dimensions, but several years were necessary to eliminate the effects of the original environment. Similar plasticity was reported for Posidonia oceanica in the Mediterranean by Meinesz et al. (1993), who reported a considerable reduction in differences in leaf width of plants from different origins after they were grown in a common environment for 2 years.
Acknowledgements I would like to express my gratitude to Francisco Rufz-Rente~a and the students who assisted with the field work of this study.
References Burkholder, J.M., Glasgow, Jr., H.B. and Cooke, J.E., 1994. Comparative effects of water-column nitrate enrichment on eelgrass Zostera marina, shoalgrass Halodule wrightii, and widgeongrass Ruppia maritima. Mar. Ecol. Prog. Ser., 105: 121-138. Erftemeijer, P.L.A., 1994. Differences in nutrient concentrations and resources between seagrass communities on carbonate and terrigenons sediments in South Sulawesi, Indonesia. Bull. Mar. Sci., 54: 403-419. Fuss, C.M. and Kelly, Jr., J.A., 1969. Survival and growth of seagrasses transplanted under artificial conditions. Bull. Mar. Sci., 19: 351-365.
138
B.l.v. Tussenbroek / Aquatic Botany 55 (1996) 133-138
McMillan, C., 1983. Morphological diversity under controlled conditions for the Halophila ovalis-H, minor complex and the Halodule uninervis complex from Shark Bay, Western Australia. Aquat. Bot., 17: 29-42. Meinesz, A., Caye, G., Loques, F. and Molenaar, H., 1993. Polymorphism and development of Posidonia oceanica transplanted from different parts of the Mediterranean into the National Park of Port-Cross. Bot. Mar., 36: 209-216. Patriquin, D., 1973. Estimation of growth rate, production and age of the marine angiosperm Thalassia testudinum KSnig. Carib. J. Sci., 13: 111-123. P6rez, M., Duarte, C.M., Romero, J., Sand-Jensen, K. and Alcoverro, T., 1994. Growth plasticity in Cymodocea nodosa stands: the importance of nutrient supply. Aquat. Bot., 47: 249-264. Phillips, R.C., 1974. Transplantation of seagrasses, with special emphasis on eelgrass, Zostera marina L. Aquaculture, 4: 161-176. Phillips, R.C. and Lewis, R.L., III, 1983. Influence of environmental gradients on variations in leaf widths and transplant success in north American seagrasses. Mar. Tech. Soc. J., 17 (2): 59-68. Powell, G.V.N., Kenworthy, W.J. and Fourqurean, J.W., 1989. Experimental evidence for nutrient limitation of seagrass growth in a tropical estuary with restricted circulation. Bull. Mar. Sci., 44: 324-340. Short, F.T., 1985. A method for the culture of tropical seagrasses. Aquat. Bot., 22: 187-193. Short, F.T., 1987. Effects of sediment nutrients on seagrasses: literature review and mesocosm experiment. Aquat. Bot., 27: 41-57. Short, F.T., Burdick, D.M. and Kaldy, J.E., III, 1995. Mesocosm experiments quantify the effects of eutrophication on eeigrass, Zostera marina. Limnol. Oceanogr., 40: 740-749. Strawn, K., 1961. Factors influencing the zonation of submerged monocotyledons at Cedar Key, Florida. J. Wildl. Manage., 25: 178-189. Tomasko, D.A. and Lapointe, B.E., 1991. Productivity and biomass of Thalassia testudinum as related to water column nutrient availability and epiphyte levels: field observations and experimental studies. Mar. Ecol. Prog. Ser., 75: 9-17. Van Tussenbroek, B.I., 1995. Thalassia testudinum leaf dynamics in a Mexican Caribbean coral reef lagoon. Mar. Biol., 122: 33-z40. Zar, J.H., 1984. Biostatistical Analysis, 2nd edn. Prentice Hall, New York, 718 pp. Zieman, J.C., 1972. Origin of circular beds of Thalassia (Spermatophyta: Hydrocharitaceae) in South Biscayne Bay, Florida, and their relationship to mangrove hammocks. Bull. Mar. Sci., 22: 559-574.
Aquatic Botany 55 (1996) 133-138
Short communication
Leaf dimensions of transplants of Thalassia testudinum in a Mexican Caribbean reef lagoon Brigitta I. van Tussenbroek
1
Estacidn Puerto Morelos, lnstituto de Ciencias del Mar y Limnologfa, Universidad Nacional Autdnoma de M~xico, Apdo. Postal 1152, Cancan, 77500 Q.Roo, Mexico
Accepted 6 May 1996
Abstract Thalassia testudinum Banks ex KSnig in a Mexican Caribbean reef lagoon showed considerable differences in leaf length and width between three sampling stations. A reciprocal transplantation experiment between these stations was completed in July 1991. After one and a half years of observation, no significant differences in leaf length were recorded among the transplants from different origins. Although differences in leaf width diminished between the transplants from different origins, leaf width showed less plasticity than leaf length, and at one station, significant small differences were still evident after 2 years. Keywords: Seagrass; Thalassia testudinum; Leaf morphology;Spatial variability; Transplantation
1. I n t r o d u c t i o n Spatial variability in leaf morphology of seagrasses is determined by environmental factors such as nutrient conditions (Short, 1987; Powell et al., 1989; Erftemeijer, 1994; P&ez et al., 1994), depth or light conditions (Strawn, 1961; Phillips, 1974; Phillips and Lewis, 1983), sediment depth (Zieman, 1972) and wave action (Patriquin, 1973). However, it is not certain to what degree this spatial variability in leaf morphology is environmentally or genetically controlled. If the environment is modified, for example by fertilization, leaf length or both leaf length and width are known to increase (Powell et al., 1989; P~rez et al., 1994). Z o s t e r a m a r i n a L., transplanted along depth gradients, showed in some cases a similar width to local plants, whereas in others, leaf width of the
~Tel.: (+ 52-5)-6228596 (satellite); fax: (+ 52-987)-10138; e-mail: [email protected]. 0304-13770/96/$15.00 Copyright © 1996 Elsevier Science B.V. All rights reserved. PII S0304-3770(96)01068-6
134
B.Lv. Tussenbroek /Aquatic Botany 55 (1996) 133-138
transplants remained different from that of the local population (Phillips and Lewis, 1983), suggesting both environmental and genetic control of leaf morphology. However, spatial differences in leaf morphology of two species of Halophila and two species of Halodule in Australia (McMillan, 1983) and of Posidonia oceanica (L.) Delile in the Mediterranean (Meinesz et al., 1993) were primarily environmentally controlled. As for the turtle grass, Thalassia testudinum Banks ex K~nig, Phillips and Lewis (1983) failed to show phenotypic flexibility over a depth gradient, as the plants died when transplanted to deeper areas. Leaves of Thalassia testudinum in the Puerto Morelos reef lagoon showed an approximate 2.5-fold difference in length, and 1.5-fold difference in leaf width, depending on the sampling site (Van Tussenbroek, 1995). These large differences in leaf dimensions within a small sampling area presented a good opportunity to test, by means of transplantation experiments, whether differences in leaf length and width are inherent to the plants or whether they are principally determined by environmental factors.
2. Materials and methods
Three sampling stations were sited in well developed Thalassia testudinum beds within differing environments in the Puerto Morelos reef lagoon, Mexican Caribbean (21°51' N). Principal differences between sampling sites were sources of external nutrient input and degree of exposure to waves. The lagoon station was approximately 30 m offshore near undersea mangrove discharges at a depth of 4.5 m; the coastal station was situated in an approximately 30-m-wide coastal fringe at the edge of the seagrass meadow where dead material accumulated (depth 2.5 m); and the back reef station was situated in a relatively wave-exposed back reef area far removed from any source of external nutrient input (depth 2.5 m). In July 1991, a reciprocal transplantation experiment was initiated between the three sampling stations. At each station, three core samples (diameter 20 cm) were taken, one of each was placed at each station and marked with a hoop. The length and width of the longest blade of each shoot were measured at monthly intervals until October or November of the same year. From January 1992 until July 1993, these characteristics were measured twice annually. In October 1991, the hoops indicating the location of the transplants were lost at the lagoon station, and further observations were discontinued at this station. A one-way ANOVA was used to compare the mean lengths and widths of the transplants from different origins. Leaf length data were log transformed to approach homogeneity of variance (Zar, 1984).
3. Results
All Thalassia testudinum leaves showed a decrease in leaf dimensions in the following months after transplantation (Figs. 1 and 2). At the lagoon station, plants were lost after 4 months, and at this station, observations were discontinued after the initial period of decline in leaf dimensions. At the coastal and back reef stations, leaves of the
B.I.o. Tussenbroek / Aquatic Botany 55 (1996) 133-138
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Fig. 1. Thalassia testudinum mean leaf length measured during the transplantation experiment at the three receptor stations in the Puerto Morelos lagoon. Shaded area represents period of twice-yearly measurements. Bars represent standard error.
transplants from different origins gradually reached similar lengths (Fig. 1). In January and July 1993, no significant differences in leaf length were recorded between the transplants at the coastal station ( F = 1.71, P = 0.19, d.f. = 68 and F = 2.40, P = 0.10, d.f. = 69 for January and July 1993, respectively), and at the back reef station ( F = 1.40, P = 0.25, d.f. = 102 and F = 0.05, P = 0.95, d.f. = 104 for January and July 1993,
136
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Fig. 2. Thalassia testudinum mean leaf width measured during the transplantationexperiment at the three receptor stations in the Puerto Morelos lagoon. Shaded area represents period of twice-yearlymeasurements. Bars represent standard error.
respectively). Leaf width remained significantly different origin at the coastal station until July Fig. 2), although differences were small. At transplants attained a similar width at the end P --- 0.09, d.f. = 104; Fig. 2).
different between the transplants from 1993 ( F = 6.67, P = 0.002, d.f. = 69; the back reef station, leaves of the of the observation period ( F = 2.48,
B.l.v. Tussenbroek / Aquatic Botany 55 (1996) 133-138
137
4. Discussion The sudden decrease in leaf length, and to a lesser degree, in leaf width, immediately after the onset of the experiment were most likely an effect of transplantation, and 5 months to 1 year were necessary for recovery (Fig. 1). These results suggest that, with the increasing use of mesocosms for seagrass studies (Short, 1987; Tomasko and Lapointe, 1991; Burkholder et al., 1994; Short et al., 1995), a possible acclimation period of transplants should be taken into account. Short (1985) reported little changes in plant abundance and leaf morphology after transplantation of plugs of Thalassia testudinum from shallow environments to culture tanks; however, he did not present quantitative data. Fuss and Kelly (1969), in accordance with the findings of this study, reported a decline of leaf weight for T. testudinum transplants when placed in a throughflow sea-water system, and that the plants required a full year for complete recovery. Leaf width is considered to be an indicator of environmental stress (Phillips and Lewis, 1983) and generally, leaf width is used as a parameter for assessment of the effect of transplantations (Phillips, 1974; Phillips and Lewis, 1983; Meinesz et al., 1993). However, leaf length as well as leaf width was included in this study, as differences between T. testudinum at the stations were characterized by variations in both leaf dimensions. Leaf length showed a slightly greater plasticity than leaf width, as the lengths of plants from different origins were similar at both stations after 1.5 years. Plants of different origins only reached similar widths after 2 years at the back reef station, and they remained significantly different (at P = 0.05) at the coastal station at the conclusion of the experiment after 2 years. Thus, T. testudinum in the Puerto Morelos lagoon showed phenotypic plasticity in leaf dimensions, but several years were necessary to eliminate the effects of the original environment. Similar plasticity was reported for Posidonia oceanica in the Mediterranean by Meinesz et al. (1993), who reported a considerable reduction in differences in leaf width of plants from different origins after they were grown in a common environment for 2 years.
Acknowledgements I would like to express my gratitude to Francisco Rufz-Rente~a and the students who assisted with the field work of this study.
References Burkholder, J.M., Glasgow, Jr., H.B. and Cooke, J.E., 1994. Comparative effects of water-column nitrate enrichment on eelgrass Zostera marina, shoalgrass Halodule wrightii, and widgeongrass Ruppia maritima. Mar. Ecol. Prog. Ser., 105: 121-138. Erftemeijer, P.L.A., 1994. Differences in nutrient concentrations and resources between seagrass communities on carbonate and terrigenons sediments in South Sulawesi, Indonesia. Bull. Mar. Sci., 54: 403-419. Fuss, C.M. and Kelly, Jr., J.A., 1969. Survival and growth of seagrasses transplanted under artificial conditions. Bull. Mar. Sci., 19: 351-365.
138
B.l.v. Tussenbroek / Aquatic Botany 55 (1996) 133-138
McMillan, C., 1983. Morphological diversity under controlled conditions for the Halophila ovalis-H, minor complex and the Halodule uninervis complex from Shark Bay, Western Australia. Aquat. Bot., 17: 29-42. Meinesz, A., Caye, G., Loques, F. and Molenaar, H., 1993. Polymorphism and development of Posidonia oceanica transplanted from different parts of the Mediterranean into the National Park of Port-Cross. Bot. Mar., 36: 209-216. Patriquin, D., 1973. Estimation of growth rate, production and age of the marine angiosperm Thalassia testudinum KSnig. Carib. J. Sci., 13: 111-123. P6rez, M., Duarte, C.M., Romero, J., Sand-Jensen, K. and Alcoverro, T., 1994. Growth plasticity in Cymodocea nodosa stands: the importance of nutrient supply. Aquat. Bot., 47: 249-264. Phillips, R.C., 1974. Transplantation of seagrasses, with special emphasis on eelgrass, Zostera marina L. Aquaculture, 4: 161-176. Phillips, R.C. and Lewis, R.L., III, 1983. Influence of environmental gradients on variations in leaf widths and transplant success in north American seagrasses. Mar. Tech. Soc. J., 17 (2): 59-68. Powell, G.V.N., Kenworthy, W.J. and Fourqurean, J.W., 1989. Experimental evidence for nutrient limitation of seagrass growth in a tropical estuary with restricted circulation. Bull. Mar. Sci., 44: 324-340. Short, F.T., 1985. A method for the culture of tropical seagrasses. Aquat. Bot., 22: 187-193. Short, F.T., 1987. Effects of sediment nutrients on seagrasses: literature review and mesocosm experiment. Aquat. Bot., 27: 41-57. Short, F.T., Burdick, D.M. and Kaldy, J.E., III, 1995. Mesocosm experiments quantify the effects of eutrophication on eeigrass, Zostera marina. Limnol. Oceanogr., 40: 740-749. Strawn, K., 1961. Factors influencing the zonation of submerged monocotyledons at Cedar Key, Florida. J. Wildl. Manage., 25: 178-189. Tomasko, D.A. and Lapointe, B.E., 1991. Productivity and biomass of Thalassia testudinum as related to water column nutrient availability and epiphyte levels: field observations and experimental studies. Mar. Ecol. Prog. Ser., 75: 9-17. Van Tussenbroek, B.I., 1995. Thalassia testudinum leaf dynamics in a Mexican Caribbean coral reef lagoon. Mar. Biol., 122: 33-z40. Zar, J.H., 1984. Biostatistical Analysis, 2nd edn. Prentice Hall, New York, 718 pp. Zieman, J.C., 1972. Origin of circular beds of Thalassia (Spermatophyta: Hydrocharitaceae) in South Biscayne Bay, Florida, and their relationship to mangrove hammocks. Bull. Mar. Sci., 22: 559-574.