Population studies of the Gigartinaceae (Rhodophyta) have often observed that the ratio of gametophytes to tetrasporophytes varies with the location of the population or the time of sampling. For some species, patterns have emerged that correlate this ratio to one or a few particular environmental variables, such as elevation, wave exposure, or season. Identifying these distributional patterns is an important step towards understanding what (if any) ecological differences exist between the two free-living life history stages.
The purpose of this study was to measure the ratio of gametophytes to tetrasporophytes of intertidal populations of Chondrus crispus across a decreasing salinity gradient from Rhode Island Sound, Rhode Island to Long Island Sound, Connecticut

Grace, Sean

Guidone, Michele

English

Sacred Heart University: DigitalCommons@SHU

Sacred Heart UniversityDigitalCommons@SHUBiology Faculty Publications Biology Department1-2010The Ratio of Gametophytes to Tetrasporophytes ofIntertidal Chondrus Crispus (Gigartinaceae)Across a Salinity GradientMichele GuidoneSacred Heart University, guidonem@sacredheart.eduSean GraceSouthern Connecticut State UniversityFollow this and additional works at: http://digitalcommons.sacredheart.edu/bio_facPart of the Marine Biology Commons, Population Biology Commons, and the Terrestrial andAquatic Ecology CommonsThis Article is brought to you for free and open access by the Biology Department at DigitalCommons@SHU. It has been accepted for inclusion inBiology Faculty Publications by an authorized administrator of DigitalCommons@SHU. For more information, please contactferribyp@sacredheart.edu.Recommended CitationGuidone, Michele and Grace, Sean, "The Ratio of Gametophytes to Tetrasporophytes of Intertidal Chondrus Crispus (Gigartinaceae)Across a Salinity Gradient" (2010). Biology Faculty Publications. 55.http://digitalcommons.sacredheart.edu/bio_fac/55BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors,nonprofit publishers, academic institutions, research libraries, and research funders in the common goal ofmaximizing access to critical research.The Ratio of Gametophytes to Tetrasporophytes ofIntertidal Chondrus crispus (Gigartinaceae) Across aSalinity GradientAuthor(s): Michele Guidone and Sean GraceSource: Rhodora, 112(949):80-84. 2010.Published By: The New England Botanical Club, Inc.DOI: http://dx.doi.org/10.3119/08-35.1URL: http://www.bioone.org/doi/full/10.3119/08-35.1BioOne (www.bioone.org) is a nonprofit, online aggregation of coreresearch in the biological, ecological, and environmental sciences. BioOneprovides a sustainable online platform for over 170 journals and bookspublished by nonprofit societies, associations, museums, institutions, andpresses.Your use of this PDF, the BioOne Web site, and all posted and associatedcontent indicates your acceptance of BioOne’s Terms of Use, available atwww.bioone.org/page/terms_of_use.Usage of BioOne content is strictly limited to personal, educational, andnon-commercial use. Commercial inquiries or rights and permissionsrequests should be directed to the individual publisher as copyright holder.NEW ENGLAND NOTETHE RATIO OF GAMETOPHYTES TOTETRASPOROPHYTES OF INTERTIDAL CHONDRUSCRISPUS (GIGARTINACEAE) ACROSS ASALINITY GRADIENTMICHELE GUIDONEDepartment of Biological Sciences, University of Rhode Island,120 Flagg Road, Kingston, RI 02881e-mail: mguidone@mail.uri.eduSEAN GRACEDepartment of Biology, Southern Connecticut State University,501 Crescent Street, New Haven, CT 06515e-mail: graces2@southernct.eduPopulation studies of the Gigartinaceae (Rhodophyta) have oftenobserved that the ratio of gametophytes to tetrasporophytes (theG:T ratio) varies with the location of the population or the time ofsampling. For some species, patterns have emerged that correlateG:T ratio to one or a few particular environmental variables, suchas elevation (Scrosati and Mudge 2004b), wave exposure (Dyck andDe Wreede 2006; Dyck et al. 1985; Mudge and Scrosati 2003), orseason (De Wreede and Green 1990; Dyck and De Wreede 1995,2006). Identifying these distributional patterns is an important steptowards understanding what (if any) ecological differences existbetween the two free-living life history stages.Chondrus crispus Stackhouse is a relatively well studied species inthe Gigartinaceae, yet a distributional pattern remains to beestablished for its life history stages. Two studies of subtidal C.crispus populations reported an increase in relative tetrasporophyteabundance with increasing water depth (Craigie and Pringle 1978;Mathieson and Burns 1975); however, Lazo et al. (1989) found noconsistent relationship between tetrasporophyte abundance anddepth, indicating this pattern does not hold under all environmentalconditions. Studies of intertidal C. crispus have reported a widerange of G:T ratios, with populations ranging from 62% to100% gametophytic (Bhattacharya 1985; Carrington et al. 2001;RHODORA, Vol. 112, No. 949, pp. 80–84, 2010E Copyright 2010 by the New England Botanical Club80Dudgeon and Johnson 1992; Scrosati and Mudge 2004a; Scrosati etal. 1994).The purpose of this study was to measure the G:T ratio ofintertidal populations of Chondrus crispus across a decreasingsalinity gradient from Rhode Island Sound, Rhode Island to LongIsland Sound, Connecticut. Previous work conducted by Lindgrenand A˚berg (1996) detected a negative relationship between salinityand C. crispus G:T ratio at two sites with yearly salinity ranges of 0–10 PSU and 10–35 PSU. Although the east to west change insalinity at our study sites was not as extreme as the one examined byLindgren and A˚berg (1996), we hypothesized that a negativecorrelation between salinity and G:T ratio would be found.Our study sites were, from east to west: Bass Rock (Narragansett,Rhode Island, 41u24.2739N, 71u27.4489W), Bluff Point (Groton,Connecticut, 41u18.8449N, 72u2.1569W), Meigs Point (Madison,Connecticut, 41u14.9989N, 72u32.5159W), and Lighthouse Point(New Haven, Connecticut, 41u14.9729N, 72u54.2429W). Salinity forthe four study sites, from east to west, decreases from an average of32 PSU to 26 PSU (CTDEP 2006; Shonting and Cook 1970). Thefour study sites also represent an east to west decrease in waveexposure (pers. obs.), however, this was not expected to impactChondrus crispus G:T ratio, as both C. crispus phases are equallyvulnerable to removal by wave action (Carrington et al. 2001) andhigh G:T ratios have been observed at both exposed (Bhattacharya1985; Dudgeon and Johnson 1992) and protected (Carrington et al.2001) sites.Fifty Chondrus crispus fronds were haphazardly collected on 15October 2006 from Bluff Point and on 3–4 November from BassRock, Meigs Point, and Lighthouse Point. All fronds were collectedat mean low water, each at least 10 cm away from the others, toincrease the likelihood that each frond represented a different genet(Scrosati and Mudge 2004b). Life history stages were determinedusing a resorcinol-acetal chemical test (Garbary and De Wreede1988). A Chi-Square test was conducted using SIGMA-STATH 2.0(SPSS Inc., Chicago, IL).The three Long Island Sound populations were found to begametophyte dominated with an east to west decrease in the relativeproportions of gametophytes. The Bluff Point, Meigs Point, andLighthouse Point populations were 90%, 78%, and 62% gameto-phytic, respectively. In contrast, the Bass Rock population showedslight tetrasporophyte dominance, at 48% gametophytic. Results of2010] New England Note 81the Chi-Square analysis showed that the proportion of life historystages differed significantly among sites (df 5 3, x2 5 23.487, p ,0.05).While an east to west decrease in relative gametophyteabundance was positively correlated to salinity decreases withinLong Island Sound, this pattern was inconsistent when the BassRock population was considered. Bass Rock had a higher salinityand a greater relative abundance of tetrasporophytes than thesampled Long Island Sound populations. As such, our results failedto confirm the negative relationship between salinity and Chondruscrispus G:T ratio observed by Lindgren and A˚berg (1996).However, our results may not be directly comparable to those ofLindgren and A˚berg (1996), as our sites spanned a smaller salinitygradient and the C. crispus populations we sampled were intertidalwhile those in the Lindgren and A˚berg (1996) study were shallowsubtidal. In addition, the high percentage of intertidal tetrasporo-phytes observed at the Bass Rock site might have been due to an‘‘uplifting’’ of the subtidal population, where tetrasporophytes arethought to be more abundant (Mathieson and Burns 1975). Thisuplift of the subtidal population would obscure any G:T ratiopattern due solely to salinity. Another factor to consider is that ourstudy populations were located at the southern edge of the C.crispus distribution in the western Atlantic. Previous studies haveshown the reproductive potential of several Rhodophyta species tobe restricted at the edges of their distributional ranges, resulting inabnormal life history ratios (Dixon 1965). However, we do notbelieve this to be the case for our study populations, as many thalliwere reproductive at the time of sampling.One factor not considered in our study was the impact ofherbivores that may preferentially consume one of the two lifehistory stages. Within the Gigartinaceae, selective grazing has beenobserved to impact Chondrus crispus (Lindgren et al. 2003),Mazzaella laminarioides (Buschmann and Santelices 1987), andM. flaccida (Thornber et al. 2006). Herbivores were not quantifiedin this study, so it is not known if herbivore composition differsbetween the study sites or how it might affect C. crispus G:T ratio atthese sites.ACKNOWLEDGMENTS. We thank A. Mathieson, C. Thornber, andC. Yarish for their valuable comments on earlier drafts of thismanuscript.82 Rhodora [Vol. 112LITERATURE CITEDBHATTACHARYA, D. 1985. The demography of fronds of Chondrus crispusStackhouse. J. Exp. Mar. Biol. Ecol. 91: 217–231.BUSCHMANN, A. H. AND B. SANTELICES. 1987. Micrograzers and spore release inIridaea laminarioides Bory (Rhodophyta: Gigartinales). J. Exp. Mar. Biol.Ecol. 108: 171–179.CARRINGTON, E., S. P. GRACE, AND T. CHOPIN. 2001. Life history phases and thebiomechanical properties of the red alga Chondrus crispus (Rhodophyta).J. Phycol. 37: 699–704.CRAIGIE, J. S. AND J. D. PRINGLE. 1978. Spatial distribution of tetrasporophytesand gametophytes in four maritime populations of Chondrus crispus.Canad. J. Bot. 56: 2910–2914.CTDEP. 2006. Water Quality Monitoring Program. Connecticut Dept.Environmental Protection, Bureau of Water Management, Hartford, CT.DE WREEDE, R. E. AND L. G. GREEN. 1990. Patterns of gametophyte dominanceof Iridaea splendens (Rhodophyta) in Vancouver harbour, Vancouver,British Columbia. Canad. J. Appl. Phycol. 2: 27–34.DIXON, P. S. 1965. Perennation, vegetative propagation, and algal life histories,with special reference to Asparagopsis and other Rhodophyta. Bot.Gothob. 3: 67–74.DUDGEON, S. R. AND A. S. JOHNSON. 1992. Thick versus thin: Thallusmorphology and tissue mechanics influence differential drag anddislodgement of two co-dominant seaweeds. J. Exp. Mar. Biol. Ecol.165: 23–43.DYCK, L. J. AND R. E. DE WREEDE. 1995. Patterns of seasonal demographicchange in the alternate isomorphic stages of Mazzaella splendens(Gigartinales, Rhodophyta). Phycologia 34: 390–395.——— AND ———. 2006. Seasonal and spatial patterns of population densityin the marine macroalga Mazzaella splendens (Gigartinales, Rhodophyta).Phycol. Res. 54: 21–31.———, ———, AND D. GARBARY. 1985. Life history phases in Iridaea cordata(Gigartinaceae): Relative abundance and distribution from BritishColombia to California. Jap. J. Phycol. 33: 225–232.GARBARY, D. J. AND R. E. DE WREEDE. 1988. Life history phases in naturalpopulations of Gigartinaceae (Rhodophyta): Quantification using resor-cinol, pp. 174–178. In: C. S. Lobban, D. J. Chapman, and B. P. Kremer,eds., Experimental Phycology: A Laboratory Manual. Cambridge Univ.Press, Cambridge, U.K.LAZO, M. L., M. GREENWELL, AND J. MCLACHLAN. 1989. Population structure ofChondrus crispus Stackhouse (Gigartinaceae, Rhodophyta) along the coastof Prince Edward Island, Canada: Distribution of gametophytic andsporophytic fronds. J. Exp. Mar. Biol. Ecol. 126: 45–58.LINDGREN, A. AND P. A˚BERG. 1996. Proportion of life cycle stages of Chondruscrispus and its population structure: A comparison between a marine andan estuarine environment. Bot. Mar. 39: 263–268.———, H. PAVIA, AND P. A˚BERG. 2003. 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The Ratio of Gametophytes to Tetrasporophytes of Intertidal Chondrus Crispus (Gigartinaceae) Across a Salinity Gradient

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The Ratio of Gametophytes to Tetrasporophytes of Intertidal Chondrus Crispus (Gigartinaceae) Across a Salinity Gradient

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