Browsing by Author "SANTELICES, B"

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    A HARVESTING STRATEGY FOR IRIDAEA-LAMINARIOIDES IN CENTRAL CHILE
    (1987) SANTELICES, B; NORAMBUENA, R
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    A NEW SPECIES AND NEW RECORDS OF MARINE-ALGAE FROM CHILE
    (1989) SANTELICES, B; RAMIREZ, ME; ABBOTT, IA
    Continued study of the marine algae of the coast of northern and central Chile has revealed the presence of a number of new forms. A new species (Gastroclonium cylindricum), two new combinations (Cryptonemia lobata (Howe, 1914) [Chrysymenia lobata] and Gastroclonium trichodes Pujals 1967) [Coeloseira trichodes] and the presence of four species with highly disjunct patterns of geographic distribution (Cutleria multifida, Colpomenia phaeodactyla, Petroglossum pacificum and Schotteria nicaeensis) are reported.
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    ABIOTIC CONTROL OF REATTACHMENT IN GELIDIUM-CHILENSE (MONTAGNE) SANTELICES-AND-MONTALVA (GELIDIALES, RHODOPHYTA)
    (1994) SANTELICES, B; VARELA, D
    Many of the agar-producing species of Gelidium and Pterocladia live on calcareous substrata in habitats with strong water movement. The thalli may suffer fragmentation by hydrodynamic drag but the vegetative fragments may reattach through differentiation of bundles of colorless, elongated rhizoids produced by inner and outer cortical cells. These rhizoids pass through intercellular spaces in the cortex, protrude outside the frond and cement the thallus fragments to the substratum. In Gelidium chilense (Montagne) Santelices & Montalva, differentiation and abundance of bundles of attachment cells are stimulated by the presence of calcareous substratum, minor additions (0.5 mM) of Ca2+ to the culture medium and by the highest photon flux density used (50-90 muE.m-2.s-1). Photoperiod does not affect production of bundles of attachment cells. Reattachment time can be as short as 10 days under optimal culture conditions. The significant effects of calcium substratum and dissolved Ca2+ on the differentiation process of these attachment cells is consistent with the high number of reports describing species of Gelidium living associated with calcareous substratum.
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    ADDITIONAL EVIDENCE FOR ECOLOGICAL DIFFERENCES AMONG ISOMORPHIC REPRODUCTIVE PHASES OF IRIDAEA-LAMINARIOIDES (RHODOPHYTA, GIGARTINALES)
    (1989) LUXORO, C; SANTELICES, B
    Gametophytes are more abundant than sporophytes in wave exposed rocky intertidal populations of Iridaea laminarioides Bory in Central Chile. In this study we experimentally tested the differential effects of selected ecological factors on karyologically different life history phases. In the field, gametophytes dominated at higher elevations and during summer; tetrasporophytes were most abundant low in the intertidal and during the fall. Laboratory responses correlated with these patterns. Gametophytes exhibited greater desiccation tolerance than tetrasporophytes. Optimum growth of gametophytes occurred at higher temperatures (20.degree. C) and longer photoperiods (16:8 h LD) than sporophytes (15.degree. C and 12:12 h LD). Grazing preferences changed with the developmental stage of the alga, but all herbivores tested had increased preference for diploid tissues as compared to haploid. Number of spores produced with respect to total plant surface, or total rocky surface, or settlement of spores and their germination rate did not show significant differences between phases but showed great variability in space and time. Spontaneous spore release, however, was always higher in cystocarpic than in tetrasporangial thalli. Such a combination of results suggests tht some real ecological differences exist between the two life history phases of I. laminarioides. Such ecological differences permit a prediction of vertical and temporal patterns of distribution for both phases. Horizontal Horizontal patterns of distribution cannot be explained because the several selection factors probably interact differently in various habitats.
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    ALGAL LIFE-HISTORY STRATEGIES AND RESISTANCE TO DIGESTION
    (1987) SANTELICES, B; UGARTE, R
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    BENTHIC ALGAL SPORES SURVIVING DIGESTION BY SEA-URCHINS
    (1983) SANTELICES, B; CORREA, J; AVILA, M
    Present ideas on benthic algal adaptations to animal herbivory focus mainly on defensive and escape mechanisms of settled plants, and disregard the ability of algal reproductive bodies to escape from digestion by animals. To test this hypothesis, 150 individuals of the common Chilean sea urchin, T. niger Molina, were collected over a period of 7 mo., covering spring through fall. Fifty were examined for gut contents which revealed a total of 31 algal species, 62.9% of which could be categorized as opportunists and 37.1% as late successional forms. When the contents of fecal pellets were cultured the resulting algal species that had successfully resisted digestion by means of incomplete digestion or protective spore walls showed 84.6% as opportunists and 15.4% as late successional forms. There was no significant correlation between frequency of occurrence in the gut contents and in the fecal cultures, indicating that digestion survival depended on factors other than abundance. The capacity to survive digestion may play a role in the abundance of these species in overgrazed areas.
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    COMPARATIVE ECOLOGY OF LESSONIA-NIGRESCENS AND DURVILLAEA-ANTARCTICA (PHAEOPHYTA) IN CENTRAL CHILE
    (1980) SANTELICES, B; CASTILLA, JC; CANCINO, J; SCHMIEDE, P
    The L. nigrescens-D. antarctica belt is the most conspicuous feature of the intertidal-subtidal boundary in central Chile, with L. nigrescens attaining larger cover and biomass values than D. antarctica. Human predation of the otherwise competitively dominant D. antarctica has been suggested as accounting for its scarcity. Testing of this hypothesis included field studies of species distribution in places with and without human accessibility and various degrees of wave impact, comparative morphometric and population studies, evaluation of the ecologic role of the limpet-kelp association and comparative measurements of growth, reproduction and survival capacity. Results indicate that L. nigrescens and D. antarctica have morphologies typically adapted to habitats with different wave shock. Contrary to previous predictions, L. nigrescens appears as a plant better adapted for places with strong wave impact, which are the most common in central Chile. Complete space monopolization by L. nigrescens is prevented by a series of adaptations of D. antarctica. Certain morphological forms of this species are less affected by wave action, allowing a population stock to persist even at the most exposed places. Boring into algal holdfasts by invertebrates weakens the mechanical resistance of old, eroded plants providing open space where juveniles of either species could settle. D. antarctica seems to take greater advantage of this primary space by a fugitive life history. Finally, the survival of D. antarctica increases if attached to the top of L. nigrescens holdfasts. The result of the interaction between these 2 brown algae depends on the degree of water impact. In sheltered habitats competitive displacement of L. nigrescens could occur but it is unlikely to be a continuous process. In exposed habitats D. antarctica is constantly removed by water movement, but persists because of a higher colonization rate.
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    COMPETITIVE ALGAL COMMUNITY ORGANIZATION IN EXPOSED INTER-TIDAL HABITATS FROM CENTRAL CHILE
    (1981) SANTELICES, B; MONTALVA, S; OLIGER, P
    Measurements of cover in the field indicate that most of the lower intertidal wave-exposed habitats of Central Chile are dominated by the colonial, non-calcareous, crustose chlorophyte Codium dimorphum. Summer bleaching of the C. dimorphum colonies results in reduction of cover below the 1.5 m intertidal level and disappearance from levels above the 1.5 m mark. This, in turn, results in seasonal distributional changes in mid and upper intertidal species. Field removal experiments indicate that C. dimorphum is able to overgrow, exclude and therefore limit the lowermost extent of most other intertidal species. Recovery of C. dimorphum and the course of successional events thereafter (followed during 41 mo.) are affected by seasonal bleaching and grazing. Herbivore exclusion experiments indicate that grazing plays a major role in the seasonal reduction of cover of C. dimorphum after initial summer bleaching of the colony. These results are discussed in view of presently accepted hypotheses on intertidal algal zonation, intertidal community structure, successional events and ecological adaptation of non-calcareous crustose algal morphologies.
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    DETERMINATION OF THE DISTRIBUTION AND ABUNDANCE OF THE LIMPET SCURRIA SCURRA ON THE STIPES OF THE KELP LESSONIA-NIGRESCENS IN CENTRAL CHILE
    (1989) MUNOZ, M; SANTELICES, B
    In Central Chile, the limpet Scurria scurra lives in open cavities on the stipes of the kelp Lessonia nigrescens. Several characters in this association, including number of limpets per cavitity and number and position of cavities along the stipes, are highly fixed. In this study we use explanations suggested elsewhere for equivalent specific patterns in other limpet-kelp associations a testable hypothesis for the Scurria-Lessonia relationship. Results indicate that the limpet has a highly predictable location in the kelp bed, decreasing in abundance with decreasing tide levels and with increasing time exposed to waves. Usually one limpet is found per scar and only one scar per stripe, generally excavated under the first stipe bifurcation. Limpets can wander out of the cavities during high tides. They show no significant ontogenic changes in radular structure or in excavating capacities. They could occupy any new suitable stipe one they are dislodged due to accidents while wandering out of the cavity or because of strip breakage. In addition, close to 20% of the limpet population survives stipe breakage by remaining attached to the stipe stumps. Field experiments indicate that friction between the stipes of L. nigrescens is the most important factor determining the number and distribution of cavities on the stipes. A comparison of our findings with results on other limpet-kelp associations indicate that generalizations are restricted to a few common features only. In each association there are several additional specific characters which seemingly represent the outcome of specific life history adjustments of each interacting partner.
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    DIFFERENTIAL SURVIVAL OF MACROALGAE TO DIGESTION BY INTERTIDAL HERBIVORE MOLLUSKS
    (1985) SANTELICES, B; CORREA, J
    This study evaluates the capacity of algal propagules to survive digestion by 7 intertidal herbivore mollusks. Individual [30] Littorina peruviana, 36 of Siphonaria lessoni, 35 of Collisella ceciliana, and 25 each of C. zebrina, Chiton granosus, Fissurella crassa and F. limbata were collected at different dates between Oct., 1983 and April, 1984. About half of the individuals of each species were examined for gut contents and the other half was used to provide fecal pellets for culture. Diet of these grazers ranged from 8 macroalgal species in Collisella zebrina to 17 in F. limbata. Macroalgal propagules of 56% of the 27 algal species found in these gut contents survive digestion. There was no positive correlation between diet and number of algal taxa growing in the respective fecal cultures. Survival through L. peruviana and Chiton granosus was low (20-30% of the algal species consumed) while it was high (75-83%) through the 2 spp. of Collisella. No significant correlation was found between frequency of algae in the gut contents and its frequency in the fecal cultures. Algal capacity to survive digestion was almost exclusively restricted to opportunistic species, especially in the Chlorophyta and Phaeophyta. Survival of algal propagules through the digestive tract of generalist grazers may be a rather random phenomenon.
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    DISTRIBUTIONAL PATTERNS AND DIETS OF 4 SPECIES OF SEA-URCHINS IN GIANT-KELP FOREST (MACROCYSTIS-PYRIFERA) OF PURETO-TORO, NAVARINO ISLAND, CHILE
    (1984) VASQUEZ, JA; CASTILLA, JC; SANTELICES, B
    The distribution pattern of microhabitat and diet was studied in 4 spp. of sea urchins (Loxechinus albus, Pseudechinus magellanicus, Arbacia dufresnei, Austrocidaris canaliculata) in a forest of M. pyrifera in southern Chile. There is no overlap in space utilization (microhabitat) except for the species pair P. magellanicus-A. canaliculata. All 4 spp. of sea urchins feed on M. pyrifera in different percentages; this results in a high diet overlap in at least 3 of them; this resource does not appear to be limiting. Neither competition among adults nor predation on adults appears to be a key factor in regulating the present population desenties of the 4 spp. of sea urchins in the habitat studied. Differences in intensity of water movement, correlated with bathymetric distribution, regulate population density, size of test and biomass in these 4 spp.
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    ECOLOGICAL DIFFERENCES BETWEEN THE ISOMORPHIC REPRODUCTIVE PHASES OF 2 SPECIES OF IRIDAEA (RHODOPHYTA, GIGARTINALES)
    (1985) HANNACH, G; SANTELICES, B
    This study tests the hypothesis that species traditionally characterized as isomorphic exhibit similar physiological and ecological responses to different environmental factors, by comparing the ecological and ecophysiological responses of reproductive phases of 2 isomorphic species of Iridaea. Results indicate that although the tetrasporic and cystocarpic phases of I. laminarioides and I. ciliata have similar morphology, they do not have identical responses to ecological variables. In the field, the reproductive stages differ in their relative abundances and in their patterns of spatial and temporal distribution. In laboratory experiments, the reproductive phases showed intraspecific differences in growth rates under conditions of varying temperature, light intensity, water movement and salinity. Differences in susceptibility to grazing vary from juvenile to adult frond and from one grazer to another. The degree of ecological divergence between phases found was greater in the upper intertidal I. laminarioides and smaller in the low intertidal-shallow subtidal I. ciliata. Cystocarpic thalli of I. laminarioides dominated the upper margin of species distribution and grew faster than tetrasporic thalli under several laboratory conditions. In both species the cystocarpic phase was more abundant i the field than the tetrasporic phase. These results call into question the general belief of increased adaptivity of diploidy over haploidy in the algae.
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    ECOLOGICAL DOMINANCE OF LESSONIA-NIGRESCENS (PHAEOPHYTA) IN CENTRAL CHILE
    (1984) OJEDA, FP; SANTELICES, B
    Experimental removal of various types of dominant canopies has resulted in predictable patterns of competitive hierarchies among algae in intertidal and subtidal communities. Few attempts were made to distinguish functionally different groups of algae in these communities. The intertidal/subtidal boundary of exposed rocky habitats in central Chile is numerically dominated by the kelp L. nigrescens. When the kelp is absent, 2 other algal formations can be found at this intertidal level. In vegetational openings surrounded by individuals of L. nigrescens and in the absence of large grazers, large patches of Geldium chilense occur. In vegetational openings with abundance of grazers, patches of calcareous algae and bare rock are normally found. Through experimental manipulation the ecological changes of the understory algal assemblages following removal of the numerically dominant L. nigrescens were evaluated and with minor differences, the 3 functional groups of algae distinguished elsewhere (canopy forming, fugitive and obligated understory) also occur here. By experimental removal at different seasons and in presence or absence of sea urchins the occurrence of the 2 algal formations found in areas devoid of kelp is explained.
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    EFFECTS OF FILTER-FEEDERS AND GRAZERS ON ALGAL SETTLEMENT AND GROWTH IN MUSSEL BEDS
    (1988) SANTELICES, B; MARTINEZ, E
    Macroalgae and mussels are common users of the often limiting primary space on mid- and low-intertidal rocky surfaces. As a result most studies of their interactions have focused primarily on resource competition. Yet, frequently a diversity of algae is found coexisting with mussels.sbd.neither asphyxiating them nor being outcompeted by them. In this study, we look for other sets of ecologically important interactions between mussels and algae in the habitats where they coexist. Experimental studies showed that mussels ingest and digest algal spores, affect the pattern of algal settlement, and protect the algal germlings from desiccation. Probably, they also fertilize the growing thalli. Small grazers among the mussels select the type of algae surviving in the bed and together with the abiotic environment control algal growth and abundance. Reproductive output, antiherbivore escape and defense mechanisms, and tolerance to desiccation appear to be the most important algal adaptations for survival in this type of habitat. The resulting flora found among mussels is a function of all these interactions and of the age and history of the individual mussel bed.
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    EFFECTS OF LIGHT-INTENSITY AND NUTRIENTS ON GAMETOPHYTES AND GAMETOGENESIS OF LESSONIA-NIGRESCENS BORY (PHAEOPHYTA)
    (1982) HOFFMANN, AJ; SANTELICES, B
    Meiospores of L. nigrescens Bory collected in Central Chile, were cultivated under different light and nutrient conditions to test for their influence on the development of gametophytes and gametogenesis. The microscopic stages of the life cycle are described. Under 45 .mu.E [Einsteins] .cntdot. m-2 .cntdot. s-1 (12 h daily) and sea water enriched with nitrate and phosphate, development of few-celled gametophytes, gametogenesis and sporophyte differentiation occur within 35 days. At 10 .mu.E .cntdot. m-2 .cntdot. s-1, most gametophytes are multicellular and remain vegetative up to 65 days. Only enriched sea water or enriched sea water with double concentrations of phosphate lead to fertile few-celled gametophytes under 45 .mu.E .cntdot. m-2 .cntdot. s-1. The addition of double concentrations of nitrate - allows for the development of few-celled gametophytes but inhibits gametogenesis. The average gametophyte size progressively decreases when increasing amounts of nitrate and phosphate are added to the media.
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    EFFECTS OF SOME ENVIRONMENTAL-FACTORS ON GROWTH OF SPORELINGS IN 2 SPECIES OF GELIDIUM (RHODOPHYTA)
    (1985) CORREA, J; AVILA, M; SANTELICES, B
    The effects of temperature, photoperiod and photon-flux density on growth of sporelings of 2 spp. of the economically important [agar production] red algal genus Gelidium [G. lingulatum, G. chilense] were evaluated, and a basic set of abiotic conditions for growing these sporelings was defined.
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    EFFECTS OF STOCK LOADING AND PLANTING DISTANCE ON THE GROWTH AND PRODUCTION OF GRACILARIA-CHILENSIS IN ROPE CULTURE
    (1993) SANTELICES, B; WESTERMEIER, R; BOBADILLA, M
    Through experimental manipulation of stock loading and planting distances in rope culture, this study evaluates the hypothesis that optimum density for growth and production of Gracilaria chilensis vary within a bed. Small packages of Gracilaria disposed at short distances exhibit higher growth and production rates in the landward ends of ropes than larger packages of seaweed disposed at longer distances. In these experiments, the landward end of ropes faces estuarine conditions, with reduced salinities and increased sediment loads during low tides. The interacting effects of stocks loading and position in the rope can affect growth and production rates so much as to nullify the 3.5-fold summer increments in production that occur in these estuarine beds of southern Chile. It is concluded that through manipulation of planting distances and stock loading, the production of this species could be increased up to 35% in some areas.
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    EXPERIMENTAL TANK CULTIVATION OF GRACILARIA-CHILENSIS IN CENTRAL CHILE
    (1992) UGARTE, R; SANTELICES, B
    Gracilaria chilensis was grown continuously in tanks over a 13-month period, changing the water only every 15 days, and adding CO2, air and nutrients. Biomass production was markedly seasonal, with a summer maximum of 100 g m-2 day-1 (wet) and a winter minimum of 10 g m-2 day-1. Average production was 4.1 kg m-2 year-1 (dry), fourfold greater than the production of wild beds. The material from tank cultivation contained 30-35% agar, as compared to 18% in wild G. chilensis. Epiphytism was the main problem in these cultures, and its control with chloride may reduce productivity by 40%. Pre-treatment of the water seems to be the best method to prevent epiphytes. The marked seasonality in biomass production suggests the need to change stock density, air bubbling frequency, levels of CO2 and nutrient enrichment, and harvest frequency from summer to winter. It was estimated that such adjustments could increase the productivity of this system to 6 kg m-2 year-1 of dry Gracilaria chilensis with an annual average agar yield of 30%.
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    INTRA-CLONAL VARIATION IN THE RED SEAWEED GRACILARIA-CHILENSIS
    (1993) SANTELICES, B; VARELA, D
    The phenotypic plasticity often found in seaweed populations has been explained only from the perspective of inter-population or inter-individual differences. However, many seaweeds grow and propagate by fragmentation of genetically identical units, each with the capacity to function on its own. If significant differences in performance exist among these supposedly identical units, such differences should be expressed upon the release and growth of these units. In this study we document two such types of variation in the red seaweed Gracilaria chilensis. Populations of sporelings, each grown under similar culture conditions and derived from carpospores shed by the same cystocarp exhibit significant differences in growth. In this species, each cystocarp develops from a simple gametic fusion, and cystocarp fusions occur too infrequently to account for the growth differences observed among recruits. In adult thalli, branches (ramets) derived from the same thallus (genet) and grown under similar conditions exhibit significant variation in growth rates and morphology. These findings have several implications. They suggest that carpospore production is not only an example of zygote amplification but that it also could increase variability among mitotically replicated units. Intra-clonal variability followed by fragmentation and re-attachment may increase intra-population variation which, in species of Gracilaria, is often larger than inter-population variation. In addition, the existence of intra-clonal variability suggests that strain selection in commercially important species may require a more continuous screening of high-quality strains because of frequent genotypic or phenotypic changes in the various cultivars.