Nature of the Distributional Boundary of Fucus Serratus on the North Shore of Spain
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MARINE ECOLOGY PROGRESS SERIES Vol. 93: 183-193, 1993 Published February 23 Mar. Ecol. Prog. Ser. Nature of the distributional boundary of Fucus serratus on the north shore of Spain Julio Arrontes Laboratorio de Ecologia, Departamento de Biologia de Organismos y Sistemas. Universidad de Oviedo, E-33005 Oviedo, Spain ABSTRACT The distribution of Fucus serratus has a sharp boundary In northern Span F serratus dominates the m~d-~ntert~dalleg~on west of Novellana, Asturias but is absent further east In a short trans~t~onzone F serratus 1s abundant within patches The causes underlying this pattern were inves- tlgated by exper~rnentaltransplants of F serratus to locations In the transit~onzone and outs~deits normal range Plants moved outslde the normal range had slmllar growth and reproductive rates to those transplanted to the transition zone and ivith~nthe zone of abundance F serratus recruited at s~tes outside the normal boundary apparently from transplanted thalli Temperature affected the growth rate of embryos of F serratus in laboratory exper~rnentsThough high summer temperatures may be responsible for the lack of F serratus in the inner part of the Bay of Blscay temperature alone cannot explain the observed llm~tof distribution Other tactors such as l~miteddispersal ablllty and Inter- specific compet~tionw~th other macroalgae might also be important In settlng the boundary for F serratus in northern Spain INTRODUCTION Spain. Important differences exist in the species compo- sition between northwestern Spain (facing the open The geographical distribution of marine algae has Atlantic waters) and the Basque coast (in the inner part of frequently been related to the influence of physical the Bay of Biscay) (e.g. Fischer-Piette 1957, Anadon & factors (e.g. Dring 1982, van den Hoek 1982, Liining Niell 1981, Anadon 1983, Luning 1990). In his study 1990). The limits of distribution are often set by the on phytogeographic provinces, van den Hoek (1975) effect of critical temperatures on survival, reproduction grouped the flora of NW Spain with the floras of NW and growth of plants (van den Hoek 1982). Much Brittany and Clare Island, and the flora of the Basque experimental work has shown the relationship be- coast with the flora of Morocco. Several species of large tween distribution and tolerance to temperature in brown algae reach their limit of distribution in a middle algae (e.g. Norton 1977a, Yarish et al. 1987, Breeman zone in north Spain (including Fucus serratus, Laminaria 1988, Cambridge et al. 1990). In addition to tempera- ochroleuca, Himanthalia elongata and others) (Anadon ture, photoperiod (Breeman 1988), longitudinal barri- & Niell 1981, Anadon 1983, Luning 1990).Their pattern ers (van den Hoek 1975, 1987) and salinity (Bird & of distribution has been frequently explained by the lack McLachlan 1986, Russell 1987) have been invoked to of rocky substratum from the Loire to the Basque coast explain patterns of distribution. and locally hgh temperature during summer in the inner In addition to physical factors, biological factors are part of the bay (Luning 1990).Summer upwelling condi- recognized as acting on the distribution of macroalgae tions would produce temperature ranges suitable for at small scales. Their role has been much less fre- these macroalgae, permitting their reappearance on the quently studied, though herbivory can be important in west shore of northern Spain. Although the dstributional explaining the patterns of algal abundance in different boundaries are not exactly coincident for all these geographical areas (Lubchenco 1980, Hay 1981, Gaines species, they lie in approximately the same part of the & Lubchenco 1982). shore. Past evidence suggests, however, that the hits A conspicuous change in the composition of marine of distribtion of these species have moved considerably algae has been described along the shores of northern during this century (Fischer-Piette 1957). 0 Inter-Research 1993 184 Mar. Ecol. Prog. Ser. 93: 183-193, 1993 Among the species displaying an unequal distribu- absent negatively influences growth and/or reproduc- tion along the shore of N Spain, Fucus serratus exhibits tion and so prevents the spread of E serratus. In addition a sharp decline in abundance from west to east. It is to the transplant experiment, I present information on abundant in NW Spain, where it often dominates the the growth and reproduction of the species in its natural space in mid and lower tidal levels, but is absent from environment and a laboratory experiment on the effect the Basque coast. E serratus is a species widely dis- of temperature on the growth of F. serratusembryos. tributed on the Atlantic shores of Europe and is locally abundant in Nova Scotia (Canada). Its southern distri- butional boundary on the European shores lies in MATERIAL AND METHODS northern Portugal (Pazo & Niell 1977, Liining 1990). If its distribution is primarily determined by temperature, A survey, between 6" and 7" W, was made along the then it can be assumed that high temperatures are coast of Spain to detect the exact location of the dis- important in setting the distribution boundary on the tributional boundary of Fucus serratus. Field experi- shore of N Spain (see Breeman 1988). ments were made at 3 localities, Oleiros (43'34' N, Several oceanographic features with potential influ- 6" 12' W), Campiello (43" 33' N, 6" 24' W) and Torbas ence on the dispersal, growth and survival of macroalgae (43" 33' N, 6" 47' W) (Fig. 1). All 3 stations are rock have been described for the Spanish shore of the bay of platforms under steep cliffs exposed to moderate wave Biscay. Coastal currents are W-E du~gwinter but in- action. The substratum is formed by quartzite and verse, E-W, during summer. During summer, surface slate. Oleiros is outside the normal range of distribu- waters are warmer towards the inner part of the bay (US tion of FL~CUSserratus, Campiello is in a transition zone, Naval Oceanographic Office 1967, Maillard 1986).The where F. serratus occurs in patches, while at Torbas difference in temperature between the inner and outer E serratus is abundant. Intertidal zonation was studied part can be as large as 3 "C. This differe~cecan be tem- at Torbas and Oleiros by making a transect perpen- porarily increased in some zones due to upwelling con- dicular to the shoreline from 0.5 m to 2.5 m above the ditions near the shore during summer. Underwater cur- lowest tidal level. At regular intervals (2 m at Oleiros, rents, driven by northeasterly winds, are responsible for 3 m at Torbas), percentage cover of macroalgae was the elevation of cold water (Botas et al. 1990).Upwelling estimated in 3 replicate 1 m2 quadrats with 100 regu- conditions are more persistent and intense towards the larly spaced points. western part of the Spanish north shore of the bay. At the 3 localities, temperature and concentration of During winter, minimum seawater temperature is be- nitrate and nitrite were measured at monthly or fort- tween 10 and 11 "C. Maximum temperature in summer nightly intervals, coinciding with spring tides, from is 19 to 20 "C for most of the shore and 21 and occasion- January 1990 to January 1991. At each locality, 4 repli- ally 22 "C in the inner part of the bay. In the littoral zone cate samples of seawater were collected at each of 4 of those parts of the shore under upwelling conditions, randomly chosen sites. Nitrate and nitrite were temperature is expected to be lower and concentra- analysed using an Autoanalyser Technicon AAII. tion of inorganic nutrients (e.g. nitrate, phosphate) Chemical analysis were made using the methods to be higher than those in oceanic waters or in adjacent, non-upwelled coastal waters. CAMPIELLO During winter, oceanographic I I conditions are the same for the entire coast (Maillard 1986, +SOON 43O40' N SATMER 1990a). L3O 30' In this paper, I explore the factors with putative influence Novellana 43O 20' on the distribution of Fucus serratus in northern Spain. 7O W b0 - 4 5O Specifically, I investigate the ability of transplanted thalli of F. serratus to grow and develop reproductive structures in lo- Fig. 1 Study sites. The shaded area represents the calities outside its range of dis- -4 0° zone where Fucus serratus is present. Discontinuous tribution. It was hypothesized shading represents the transition zone that the environment of the to0 50 W places where the species is I I Arrontes: Distributional boundary of Fucus serratus 185 described in Grashoff (1983). No other nutrients were size. Three sites were chosen at Torbas and Oleiros analysed since they are considered less important for and 4 at Campiello. At each site, 4 replicated quadrats the primary production of macroalgae (DeBoer 1981, were scraped at each of 2 tidal levels. At Oleiros, the Lobban et al. 1985). quadrats were cleared in the zones dominated by To study the seasonal variation in biomass and re- Fucus vesiculosus (high tidal level) and Bifurcaria productive status of Fucus serratus at Torbas and bifurcata (low tidal level). At Camplello, in 2 sites Campiello, 5 canopy-forming plants were collected at the quadrats were scraped in the zones dominated by random from 4 sites at monthly intervals. Reproductive F. vesiculosusus and B. bifurcata, whlle in the remain- allocation of each plant was calculated as percentage ing 2 the experimental surfaces were in zones of of dry weight represented by receptacles. Differences F. vesiculosus (high level) and F. serratus (low level). in size between canopy plants of F. serratus in Torbas At Torbas, the quadrats were in the zones dominated and Campiello were estimated from 2 random samples by F. vesiculosus and E serratus. The experimental of 65 plants taken at each locality in May 1990 (5 sites surfaces were left to recover for 6 mo.