Carlos A. Moreno

Impacts of local human activities on the Antarctic environment.

Abstract We review the scientific literature, especially from the past decade, on the impacts of human activities on the Antarctic environment. A range of impacts has been identified at a variety of spatial and temporal scales. Chemical contamination and sewage disposal on the continent have been found to be long-lived. Contemporary sewage management practices at many coastal stations are insufficient to prevent local contamination but no introduction of non-indigenous organisms through this route has yet been demonstrated. Human activities, particularly construction and transport, have led to disturbances of flora and fauna. A small number of non-indigenous plant and animal species has become established, mostly on the northern Antarctic Peninsula and southern archipelagos of the Scotia Arc. There is little indication of recovery of overexploited fish stocks, and ramifications of fishing activity on bycatch species and the ecosystem could also be far-reaching. The Antarctic Treaty System and its instruments, in particular the Convention for the Conservation of Antarctic Marine Living Resources and the Environmental Protocol, provide a framework within which management of human activities take place. In the face of the continuing expansion of human activities in Antarctica, a more effective implementation of a wide range of measures is essential, in order to ensure comprehensive protection of the Antarctic environment, including its intrinsic, wilderness and scientific values which remains a fundamental principle of the Antarctic Treaty System. These measures include effective environmental impact assessments, long-term monitoring, mitigation measures for non-indigenous species, ecosystem-based management of living resources, and increased regulation of National Antarctic Programmes and tourism activities.

ESCAPED SALMON IN THE INNER SEAS, SOUTHERN CHILE: FACING ECOLOGICAL AND SOCIAL CONFLICTS

During heavy storms in 1994–1995, salmon farms in southern Chile lost several million fish from the most commonly farmed species, rainbow trout (Oncorhynchus mykiss), coho salmon (Oncorhynchus kisutch), and Atlantic salmon (Salmo salar). To determine the abundance and distribution of such exotic salmon populations in the wild and their effect on native organisms, we conducted experimental fishing, in six locations in the salmon farming regions (41°–46° S) in the inner seas of Chiloe (X Region) and Aysen (XI Region), between November 1995 and December 1996. At the same time, we collected information from salmon farms and insurance companies about escaped individuals. During the experimental fishing we captured 2602 coho salmon, 984 trout, and 271 Atlantic salmon. Captures of the three species declined through the duration of the study; thus in November 1996 we captured <10% of initial catches. Population projections based on three possible mortality rates (0.4, 0.8, and 1.2) predicted the disappearance of salmon by year 2000, and the highest mortality rate was the best predictor of the observed available biomass in 1996. Thus, artisanal fishing may control escaped salmon. Of the three species, coho salmon had the best chances of becoming established in the remote XI Region where the artisanal fishing pressure was less intense. The three salmon species showed feeding similarities, since each kept feeding on pellets beneath the farms, particularly Atlantic salmon, while coho salmon showed greater preference for schooling fish, and rainbow trout fed more often on crustaceans. Thus, the three species, particularly coho salmon, could compete with native southern hake and mackerel. As a management approach to avoid salmon colonization and naturalization in southern Chile, local artisanal fishing should be encouraged because it is probably the most efficient way to remove escaped individuals and reduce the chance of populations becoming self-sustaining.

Diversity, dynamics and biogeography of Chilean benthic nearshore ecosystems: an overview and guidelines for conservation

A pesar de que Chile ha sido un pais pionero en estudios del efecto del impacto humano sobre la estructura comunitaria en ambientes marinos, y a pesar de la enorme importancia economica y social que el ambiente marino tiene para el pais, el desarrollo de programas de conservacion marina y de bases cientificas para la sustentabilidad no se han generado a la misma tasa a la que han explotado los recursos y se ha utilizado el ambiente costero para diversos fines. Aunque nosotros pensamos que el establecimiento de planes de conservacion a lo largo de la costa de Chile debe basarse en varios factores, los principios cientificos, biologicos y ecologicos deben guiar muchos de estos esfuerzos, y en este trabajo nosotros intentamos presentar una vision general del estado actual del conocimiento sobre la ecologia y la biogegrafia del sistema costero en Chile. En base a la informacion mas relevante existente, nuestros objetivos son: 1) identificar las caracteristicas biogeograficas y ecologicas del ecosistema costero y tambien vacios en informacion, 2) identificar las actividades humanas mas daninas que tengan impacto en la estructura y dinamica de estos sistemas, y 3) sugerir el uso de posibles indicadores para determinar la situacion de diferentes areas de la costa de Chile, y las necesidades de conservacion. Esta revision muestra, por un lado, areas geograficas con informacion critica deficitaria para planes futuros de manejo y conservacion marina , y por el otro lado, la disponibilidad de informacion de alta calidad para otras zonas geograficas del pais. Respecto de la informacion existente sobre taxonomia y patrones de distribucion de especies a gran escala, existen importantes vacios de informacion; no se esperan en el futuro grandes cambios en el numero total de especies. Existen pocos estudios sobre patrones de distribucion de especies a gran escala, y mas informacion es necesaria para identificar areas de alta diversidad de especies, especialmente para algunos taxa, como tambien para identificar areas que posean caracteristicas unicas en relacion a especies (endemicas, especies claves) y a procesos ecosistemicos (disturbios, surgencias). Para la mayoria de los invertebrados y macroalgas, las areas de alta diversidad de especies se encuentran en el sur de Chile. Nuevos estudios dirigidos a entender los factores que podrian generar patrones a macroescala son necesarios, como tambien informacion sobre oceanografia costera y disponibilidad de larvas. Esta informacion es clave para el diseno de una futura red de parques marinos. Por otro lado, la informacion disponible sobre estructuras comunitarias y funcionamiento ecosistemico, especialmente sobre el efecto del impacto humano, provienen de pocas regiones geograficas. Mas informacion sobre otras zonas geograficas es requerida, particularmente si se consideran las diferencias notables en temperatura, patrones de circulacion, heterogeneidad del habitat, y composicion de especies, como tambien el efecto de surgencia y de El Nino a lo largo de los mas de 4.000 km de costa de Chile. Finalmente, listamos las que consideramos son las actividades humanas mas daninas para el ambiente marino, e integramos esta informacion para sugerir posibles indicadores ambientales y necesidades basicas y sugerencias para conservacion marina in Chile

The response of an intertidal Concholepas concholepas (Gastropoda) population to protection from Man in southern Chile and the effects on benthic sessile assemblages

In this paper we document the changes experienced by the carnivorous Concholepas concholepas snail population after the establishment of a marine reserve in May 1978. Our data indicate that the release from human predation results in a striking change of the Concholepas population structure, due to the increment of individuals larger than 40-50 mm peristomal length. This evidence strongly indicates that the usual absence of larger size classes from the intertidal is not a consequence of physiological limitations of the muricid, as was previously thought. Significant density differences were detected only in 1984, but they were due to substantial reduction of the snails in the harvested control area.

Discovery of a blue whale feeding and nursing ground in southern Chile

After the extensive exploitation that reduced the Southern Hemisphere blue whale (Balaenoptera musculus) populations to less than 3% of its original numbers, studies on its recovery have been compounded by the inaccessibility of most populations and the extensive migrations between low and high latitudes, thus ensuring that knowledge about blue whale ecology and status remains limited. We report the recent discovery of, arguably, the most important blue whale feeding and nursing ground known to date in the Southern Hemisphere, which is located near the fjords off southern Chile. Through aerial and marine surveys (n=7) 47 groups, comprising 153 blue whales including at least 11 mother–calf pairs, were sighted during the austral summer and early autumn of 2003. The implications of this discovery on the biological understanding and conservation of this endangered species are discussed.

The role of grazers in the zonation of intertidal macroalgae of the Chilean coast

The role of herbivores in maintaining the pattern of zonation of macroalgae in the mid-intertidal community of semi-exposed shores was studied during 8 months (January to September 1979). Herbivores were totally removed every 15 days from a semi-exposed intertidal rocky wall, while another wall served as a control. Percent cover of algae was measured at two month intervals. Herbivore removal resulted in a disruption of the pattern of zonation. Iridaea boryana and Gymnogongrus furcellatus expanded the width of their belts into the zone initially occupied only by Ulva rigida and Lithophyllum spp. We conclude that herbivory is the basic mechanism which maintains the limits between the zones of these macroalgae in southern Chile.

Physical and biological processes in a Macrocystis pyrifera community near Valdivia, Chile

SummaryFrom October 10, 1979 to August 26, 1981 we investigated the effect of physical disturbance, herbivory and algal-algal competition on the dynamics of the Macrocystis community near Valdivia, Chile. The most abundant herbivore, Tegula atra, was continuously removed from one of two sites with high initial Tegula density (control and Tegula-removal rocks) and added to one of two sites where Tegula was initially absent (Tegula-addition and addition-control rocks). Macrocystis was rare at the beginning of the study. From October 1980 to April 1981 we continuously removed Macrocystis from an additional rock near the addition-control rock. On each site the response of the algal community was monitored by photographing 9, 0.25 m2 permanent quadrats at 2–4 week intervals. Tegula had little effect on Macrocystis and there were no other important herbivores present. Each summer Macrocystis dominated all 4 sites of the Tegula experiment and Tegula migrated towards the intertidal to feed. Macrocystis was reduced each winter by winter storms, the holdfasts (but not the canopy) surviving the first winter but not the second. The Macrocystis removal rock was dominated by lower growing perennial algae, indicating a competitive hierarchy among the algae of the form: Macrocystis>perennial algae>ephemeral algae>encrusting algae.Except for the presence of a competitive hierarchy among the algae and the importance of winter storms, Chilean kelp communities share few of the organizational features of their northern hemisphere counterparts. Marine mammals (excluding man) do not prey on algal consumers (Tegula and the urchin, Loxechinus albus) and these consumers have little effect on perennial macroscopic algae. Urchins apparently feed only on drift algae. Species richness in the algal community is low.

Indirect effects of human exclusion from the rocky intertidal in southern Chile: a case of cross-linkage between herbivores

Differences in size structure of the limpet Siphonaria lessoni in different localities have been related to variations in density of the key-hole limpet Fissurella picta under the supposition that they compete for food. Here, we test the hypothesis that the human exploitation of F. picta is responsible for changes in the individual growth rate of S. lessoni. Removals of F. picta before the springtime period of recruitment produced greater availability of algae in the rocks. Analysis of monthly size frequency distributions of S. lessoni cohorts recruited into these experimental zones were compared with other obtained in areas with natural densities of F. picta. In the presence of F picta, S. lessonis individual growth rate decreased; also, fecundity decreased near to 38% because individuals of the same age are smaller.

Selection of substrata by juvenile Choromytilus chorus (Mytilidae): are chemical cues important?

The importance of filamentous algae, and filamentous structures in general, to patterns of recruitment in mytilids is well documented. Surprisingly, the relative importance of physical and chemical cues in mediating this interaction has rarely been examined for mytilid larvae or plantigrades. Here we examine the distribution and abundance of three mytilid species on three common species of algae on the mid to low intertidal zone of southern Chile and then test the responses of plantigrades of one of these mytilid species to extracts from the surface of these algae and from conspecifics. We found that mytilids were always associated with the robust filamentous red alga Gymnogongrus furcellatus, but were present on less than 30% of the fronds of Iridaea laminarioides and Ulva rigida. In addition, average densities of mytilids on G. furcellatus exceeded 500 individuals per frond, more than an order of magnitude higher than on the other algal species. This alga forms an important refuge from gastropod predation for one of the mytilids examined, Choromytilus chorus (Molina), which only recruits successfully to the rocky substratum in the presence of this alga. In laboratory trials, we tested the response of juvenile (~30 mm) C. chorus to surface extracts from three species of algae which co-occur with this mytilid and extracts from the byssal threads and periostracum of conspecifics. We predicted that juveniles of this mytilid would show a strong preference for extract from G. furcellatus. Surprisingly, extract from this alga was the only extract rejected by these juvenile mussels; they produced significantly fewer byssal threads in response to treatments as compared to controls. We found no evidence that juveniles of C. chorus are responding to positive cues, but they emphatically rejected a negative cue (antifouling paint). We concluded that chemical cues are unlikely to be important in the formation of aggregations of C. chorus.

Predation upon Laternula elliptica (Bivalvia, Anatinidae): A field manipulation in South Bay, Antarctica

SummaryThe presence of empty shells of Laternula elliptica that provide refuge sites for juvenile fishes on the soft-bottom surface of South Bay, Antarctica, has been difficult to explain because this bivalve normally lives deeply buried (>50 cm). L. elliptica individuals unburied and aggregated at the surface by the action of icebergs could be consumed by mobile predators. This paper examines experimentally both burying rates and predation upon unburied L. elliptica in the field at South Bay. Live and intact L. elliptica were hand-collected by diving, and separated in 16 groups of 10 each, and placed on mud-sand bottoms protected from the ice disturbance at a depth of 17 m in South Bay. Eight groups were confined by open wooden frames so as to exclude predators, mainly star-fish and gastropods, the other eight remained as control. Species and number of predators and burying rates were estimated during 23 days. Within the first 24 h, 30% of the bivalves buried themselves, after which, rates fell abruptly. By the end of the day 23, only 60% had successfully buried; of the 40% which remained unburied, 20% were consumed by the following sequence of predators: Odontaster validus, Cryptasterias turqueti, Parborlasia corrugatus, Neobuccinum eatoni and two species of amphipods; all completely consumed one bivalve in 5–7 days. The 20% that remained unburied constituted potential prey though they showed no signs of being attacked by O. validus during the observation period. In addition to serving as prey, L. elliptica provides empty and intact shells used as refuge sites by juvenile fishes.