B. Santelices

A review of Gracilaria farming

Abstract Close to 5000 tonnes (t) of agar are processed annually from 25 000 to 30 000 t of Gracilaria, harvested mainly from the wild in Chile, Argentina, Brazil and South Africa and from fishpond culture in Taiwan, Hainan Island, China, and mainland China. Steady increases in market demand together with lack of crop management have led to overharvesting the natural stocks, to shortages of Gracilaria, to higher prices for the crop and, along with the increased market, to a demand for reliable crop quantity and quality. The outcome has been great interest in Gracilaria farming, and a diversity of farming methods has been developed. In open waters, basically three approaches are used for planting Gracilaria crops: on the bottom, on nets or lines, and on floating rafts. With each approach, either vegetative material or spores can be planted. Alternatively, Gracilaria can be farmed in ponds, raceways or tanks. A comparative review of these methods indicates that bottom planting and line farming techniques, either from spores or from vegetative material, may provide the crops for agar and agarose production. The species so cultured yield relatively large amounts of good quality seaweed by labor-intensive means at low cost in the less-developed countries. The future of fishpond cultivation of Gracilaria is difficult to predict. Perhaps the seaweed will continue to be cultivated as feed for more economically-important organisms, such as sea urchins and abalone. Production in tanks or mixed systems of pond cultivation, with or without air pumping or CO2 addition, probably will be restricted to supplying Gracilaria as a luxury-priced fresh vegetable. A variety of production ecology studies has been important in the development of the various farming methods, and increased requirements for farmed Gracilaria in the near future are likely to stimulate new approaches. Additional field population studies are required to increase the efficiency of wild crop management and bottom planting. Research on nutrient metabolism is crucial for tank cultivation. Understanding the environmental effects on gel production is needed to control the quality and quantity of gel produced under the various farming techniques. Farming involving the outplanting of sporelings will require further knowledge of Gracilaria spore biology, while biomass demands will probably stimulate new efforts in strain selection and Gracilaria farming methods.

Down under the southeastern Pacific: marine non-indigenous species in Chile.

This article presents the first compilation of marine non-indigenous species (NIS) of algae and macro-invertebrates invading Chilean waters. A total of 32 cosmopolitan and non-cosmopolitan species are reported. Among them there are six species considered as extending their southern range of distribution in connection with El Niño events. The article highlights negative and positive impacts caused by marine NIS invasions. Among the first are Codium fragile var. tomentosoide, considered as a pest in Gracilaria chilensis aquaculture facilities in northern Chile, and Ciona intestinalis, a pest in scallop aquaculture installations. Among the second are bio-engineers species, such as the ascidian Pyura praeputialis and the sea grass Heterozostera tasmanica, which have caused an increase in local biodiversity and enhancement of nursery grounds via the creation of new habitats. Further more, invaders such as the algae Mastocarpus papillosus, Porphyra linearis and P. pseudolinearis represent new exploitable resources, extracted by coastal food gatherers along the coast (M. papillosus) or potential species to develop aquaculture. Additional information is presented on the anemone Anemonia alicemartinae, which appears to be a native species (?), having shown in the past 40–50 years, a geographical southward range extension of approximately 1900 km. The number of NIS reported for Chile is compared with those published for the southwestern Atlantic, South Africa, North America (Atlantic and Pacific coasts) and New Zealand. It is suggested that probably the low number of Chilean NIS is due to the fact that the Chilean coasts are environmentally less stressed than other coasts in the world, due to the scarcity of estuaries, gulfs, enclosed bays, lagoons and low human populations. These kinds of sheltered areas have been suggested as centers for bio-invasions, due to the high rate of human-mediated transfer and increase of pollutants. Furthermore, none of NIS reported from Chile show a fast geographical expansion rate (exception of A. alicemartinae), nor invading strategies such as those described for marine NIS in other latitudes, where notorious ecological unbalances following invasions have been observed. An alternative hypothesis is that the low number of marine NIS invading Chile is underestimated, since the modern list of species generated through specific taxonomically intensive port and harbor surveys is still lacking. Fifteen species (five invertebrate and 10 fish) have been deliberately imported to Chile for aquaculture. The invertebrates appear to be controlled within aquaculture facilities and have not established naturalized populations or caused direct ecological impacts on local communities. On the contrary, several millions of salmoniforms (and rainbow trout) have escaped from farming facilities in southern Chile and established naturalized populations. Studies on ecological impacts are lacking. These escapees are also playing a role in the enhancement of artisanal and sport fishery activities.

Comparative ecology of Lessonia nigrescens and Durvillaea antarctica (phaeophyta) in Central Chile

The Lessonia nigrescens-Durvillaea 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 means of a fugitive life history. Finally, the survival of D. antarctica increases if attached to the top of L. nigrescens holdfasts. It is therefore concluded that 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.

How many kinds of individual are there

The concept of the individual links population biology with darwinian selection. In spite of its importance, the concept is used with great ambiguity. Confusions seemingly stem from a limited analysis of the variability found in attributes classically used to characterize individuality. Such characterization involves the simultaneous holding of genetic uniqueness, genetic homogeneity and autonomy, which in turn are considered invariant attributes. Data accumulated over the past 15 years, however, indicate that all three characters can independently be present or absent in different types of multicellular organism. Combining their respective presence or absence leads to recognizing different kinds of individual; a realization that has ecological and evolutionary implications.

CONVERGENT BIOLOGICAL PROCESSES IN COALESCING RHODOPHYTA

Sporeling coalescence in Gracilaria chilensis Bird, McLachlan et Oliveira produces genetically polymorphic, chimeric individuals. If this is common in red algae, it may have significant biological consequences. In this study, we evaluate the hypotheses that coalescence is widespread among the Rhodophyta and that specific and convergent morphological and ecological responses characterize this as a unique growth style among marine algae. A literature survey on coalescence was undertaken to assess the distribution of this condition in the Florideophycidae. Sixty‐two (54.9%) of 113 species considered germinated to form a disk. Subsequent development in 37 of these species showed crust formation and coalescence during development with other crusts in 31 species (84%). Coalescing red algae were members of the orders Ahnfeltiales, Corallinales, Gigartinales, Gracilariales, Halymeniales, Palmariales, and Rhodymeniales. Ultrastructural studies in species of Ahnfeltiopsis, Chondrus, Gracilaria, Mazzaella, and Sarcothalia suggested a common pattern of early development. Newly released, naked spores may fuse into a single cell, as they do in Chondrus canaliculatus, or they may develop individual cell walls that later are surrounded by a thickened common wall. Ultrastructural studies demonstrated two kinds of immediate development after the first mitotic division: direct development by symmetric divisions resulting in discoid sporelings or an indirect asymmetric arrangement of divisions before a diskoid sporeling was formed. Germination in coalescing species is a linear function of the initial spore density, whereas in noncoalescing species maximum germination occurs at intermediate densities. In the field, coalescing species may recruit either from solitary or aggregated spores. However, survival is significantly higher for plantlets grown from a larger number of coalescing spores. Total number of erect axes formed by the coalesced mass is a logarithmic function of the initial number of spores. Thus, germlings grown from a larger number of coalescing spores exhibited a larger photosynthetic canopy than do plantlets grown from a few spores. Juveniles and mature clumps grown from a coalescing mass may exhibit size inequalities among erect axes, with the larger axes located toward the center of the clump. These larger axes mature first or, in some cases, are the only to produce spores. The widespread occurrence of coalescence inroughly half the number of orders of the Florideophycidae, the similarity of the coalescence process, and the finding of various adaptive traits associated with coalescence characterizes this as a unique growth style, splitting the diversity of species now included in the Florideophycidae into two major groups: coalescing and noncoalescing Rhodophyta.

Patterns of organizations of intertidal and shallow subtidal vegetation in wave exposed habitats of central Chile

Wave-exposed rocky intertidal habitats of central Chile exhibit zonation of algal morphologies rather than strict patterns of species zonation. In low shore areas, there is a vertical sequence of perennial belts of calcareous crusts, kelp-like forms and expanded cushions or non-calcareous crusts. The calcareous crusts are represented by species of Mesophyllum, the kelp-like forms include Lessonia nigrescens and Durvillaea antarctica, while the cushions are represented by Gelidium chilense and G. lingulatum and the noncalcareous, expanded crusts by Codium dimorphum. Thin and thick blades, represented by Iridaea laminarioides, Ulva rigida and Porphyra columbia and filamentous forms including Ceramium rubrum, Centroceras clavulatum and Polysiphonia spp. are more patchy than the lower, perennial belts. They may, however, form distinct temporal monocultures at upper intertidal levels. Upper and lower limits of the various zones are set by interactions of several factors, the relative importance of which can change seasonally. When some of the factors restricting species distribution are experimentally removed, other interactions among factors become limiting.Within each zone, species are morphologically similar, with the abundance of species being regulated by symmetric competitive interactions. Competition is often asymmetric at the boundaries of zones except when adults of small-sized forms interact with morphologically similar juveniles of larger forms. Irrespective of their extremely different morphologies, the permanent, zone-forming algal species generally combine escape from grazers or defensive adaptations with clear competitive abilities. Nevertheless, there is a clear competitive hierarchy which is expressed in vertical displacements and zonation. The lowershore habitats could potentially be occupied by any of the different types of algae. Fast growth and large size allow the kelps to occupy this zone pushing the calcareous crust dominated-zone down into shallow subtidal areas and displacing the cushions and fleshy crusts into the low and middle intertidal regions. In turn, these last forms can displace thick and thin foliose forms and filaments to upper levels on the shore. Displaced forms may exist as patches at various levels of the shore.

SPORELING COALESCENCE AND INTRACLONAL VARIATION IN GRACILARIA CHILENSIS (GRACILARIALES, RHODOPHYTA)

This study evaluates the hypothesis that spore coalescence may cause intraclonal variation. Spore coalescence might allow the occurrence of unitary thalli that in fact correspond to genetically different, coalesced individuals. Plant portions simultaneously derived from these chimeric individuals may exhibit dissimilar growth responses even when incubated under similar abiotic conditions. Testing of the hypothesis included various approaches. Transmission electron microscopy observations of early stages of sporeling coalescence indicated that polysporic plantlets were formed by groups of spores and their derivatives. Even though adjacent cells in two different groups may fuse, these groups maintained an independent capacity to grow and form uprights. Laboratory‐grown plantlets showed a significant correlation between the initial number of spores and the total number of erect axes differentiated from the sporeling. Construction and growth of bicolor individuals indicated the chimeric nature of the coalesced individuals. Coalesced, bicolor holdfasts had green and red cells, which subsequently produced green and red uprights, respectively. Individuals fronds were also chimeric, as indicated by the production of green and red branchlets from single, red uprights. The existence of mixed tissues was further substantiated by random amplified polymorphic DNA analysis. The banding pattern produced by branchlets of a unisporic thallus was consistently monomorphic, whereas the patterns produced by the polysporic thallus were polymorphic. Growth rates of polysporic thalli had larger data dispersal and variation coefficients than oligosporic or monosporic thalli. Therefore, all results support the original hypothesis and suggest that coalescence might be ecologically more important than previously thought.

Experimental tank cultivation of Gracilaria chilensis in central Chile

Abstract 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%.

Micrograzers and spore release in Iridaea laminarioides Bory (Rhodophyta: Gigartinales)

Abstract Preferential consumption of algal reproductive tissues has been predicted to potentially reduce algal fitness by reduction of reproductive output. This study shows that the amphipod Hyale media (Dana) has a marked trophic preference for mature cystocarpic tissues of Iridaea laminarioides Bory. However, during the feeding process the amphipod tears the cystocarps releasing large numbers of spores into the water column. Germination and growth rate experiments indicate that grazer-mediated release does not affect further spore development. Field populations of I. laminarioides might have unopened cystocarps even in senescent, decaying fronds, while the total number of open cystocarps in mature and senescent fronds increases at higher amphipod density sites, suggesting a facilitation mechanism. Laboratory observations indicate spores can stick to the legs and body sides of the amphipods while a fraction of the ingested spores survives passage through the amphipod digestive tract. Thus, the amphipod seems ecologically important not only as a grazer but also as spore releaser and disperser.

A conceptual framework for marine agronomy

Between the late 1960s and the early 1980s, several generations of phycologists in Hawaii and the Philippines, associated with M. S. Doty, contributed to developing a new approach, and to advance concepts in marine agronomy. This study reviews the approach and the main concepts contributed. Integrating these contributions with others, a basic conceptual framework for marine agronomy is presented.