Coral reefs and reef-associated habitats are widely distributed in the Colombian Caribbean, and take up a total area of roughly 1800 km2. Nearly 3/4 of that area corresponds to oceanic reef complexes, atolls and banks of the Archipelago of San Andrés and Providencia, along the lower Nicaragua Rise. The remainder area is split in 16 discrete coral formations along the continental coast and around offshore islands on the continental shelf. These reef areas provide a considerable quantity and variety of resources (fish, conch, lobsters, etc.) and constitute a major item for the development of a rapidly increasing tourism industry. As a result of a 5 year baseline study of Colombian coral reefs, a total of 18 different habitat types (or map units) were recognized and mapped in these areas basing on the most remarkable physical and biological features of the sea bottom. Depending on extension, wave regime, terrestrial runoff, and topographical features of each area, some habitat types are absent or may be better or poorer represented, and the availability of certain resources that may be associated to particular habitats are consequently variable. The overall "health" status of coral communities shows remarkable differences between the reef areas and among the habitat types within the areas as well as to anthropogenic influences. Such statements arise well when habitat maps are combined in a GIS with other topological layers (condition of corals, human uses, etc.) and relational databases and analized through spatial overlays to discern interrelationships that are not readily apparent. Management issues in coastal zones where coral reefs and other associated habitats are major constituents of the seascape should focus on the well-being of these habitats, and a first step towards understanding the ecological and spatial relationships within a particular area is to make available habitat maps. They represent an essential tool for assesing which particular sectors within an area might be more affected by specific human activities and the supposed availability of certain resources and for designing marine protected areas (MPA). For example, the decisions concerning the construction of a submarine sewage effluent and the regulations in the matter of boat traffic and anchoring in San Andrés Island were based on a map of habitat susceptibility derived from the habitat maps. Moreover, in the current process in designing MPAs within the coral banks and reef-complexes in the Archipelago of San Andrés and Providencia, the spatial limits of "no take" and "no enter" zones is being traced after consulting with the stakeholders on the basis of habitat and resources availability maps.

In most developing countries, the lack of suitable maps of coastal and marine habitats represents one of the major obstacles for undertaking accurate environmental assesment of human impacts and establishing satisfactory management plans in the coastal zone. Habitat mapping for these and other purposes does not necessarily imply sofisticated techniques and high costs, and can be performed using readily available information and spending relatively short time in the field. As part of a five-year baseline study of coral reef areas in the Colombian Caribbean, started in 1994, habitat mapping was a major goal. The purpose of this paper is to summarize the approach used in that study to mapping habitats associated to coral reef formations as a kind of role model for other countries. The available geographical, morphological, ecological, and environmental information of the 23 studied areas was very variable in quantity and quality, and this usually determined the resolution and scale of the maps and the effort that had to be made in aquiring complementary data in the field. Despite minor variations, the approach and the procedures for mapping remained basically standard. Once the available information (including nautical charts, aerial photographs, satellite imagery, geographical descriptions, etc.) was gathered and assessed, the scale and spatial resolution of the thematic maps were established (in this study they ranged from 1:50,000 to 1:10,000). Analog data from conventional panchromatic aerial photographs (available at the Colombian Geographical Institute) were converted to digital format allowing application of image enhancement techniques that are normally associated with satellite imagery. At least four conspicuous control points within each photograph were located and verified preliminary from nautical charts or available topographic maps. The extraction of spatially significant features of the sea bottom (depending on the water transparency down to depths of 8 to more than 20 m) from the images ("habitats" discriminated according to grey tones and textures) was conducted by digitizing from the screen into a GIS (ILWIS 4). Based on personal experience (which increased as the study advanced), a suspected ecological unit or habitat was tentatively assigned to each recognized photo-pattern (e.g. sand, seagrass, coral, rubble, etc.). The setting of a particular area of the reef according to wave exposure and estimated depth can be used, for example, to infer the coral species dominating that area applying the classical wave-zones.model for Caribbean reefs. One or more sites corresponding to each photo-pattern were preliminary chosen for later corroboration in the field. The field work consisted basically in a general reconnaissance of the area and observations (skin and/or scuba diving) focused to characterize the physical and biological features of the bottom in so many sites as possible including the previously chosen on the photographs. Satellite positioning (GPS) and complementary data on habitat zoning, topography, depth, current, wave exposure, etc. were gathered at each site. In areas where bathymetric information was lacking or inadequate, depth profiles along representative navigated transects with GPS control points were performed using a conventional echosounder (200 khz, paper recorder) from a small vessel or boat. Classification (map units) and naming of the habitats based on the emergent biological and physical features of the bottom. The 23 mapped areas range in extension from less than 0.2 (Isla Arena) to 375 km2 (Serrana Bank), and the total extension covered by these areas is 1820 km2. Examples of the final maps obtained are shown and explained.

La Provincia Malacológica Pacífico-Panameña es la de mayor extensión del Pacífico Este y, también, la más rica y diversificada en su composición faunística. Se extiende desde la parte superior del Golfo de California, sobre los 30 30' de latitud norte, y hacia el sur hasta Cabo Blanco, al noroeste de Perú, en los 4 15' S, cubriendo una distancia de 7.375 km. Sus aguas son cálidas, pero los fenómenos de afloramiento costero ("upwellings"), en el Golfo de Panamá y algunas partes de Costa Rica, conducen a una disminución importante de la temperatura de las mismas.

Estudios detallados a lo largo de la costa Pacífica de América Central y Sudamérica podrían, quizá, mostrar la necesidad de introducir modificaciones o conducir al reconocimiento de subprovincias, como por ejemplo alrededor de las Islas Galápagos. Se han definido tres provincias comprendidas actualmente dentro de la Provincia Pacífico-Panameña. El estudio de la distribución de las especies de moluscos de la Provincia Pacífico-Panameña podría permitir definir o reconocer otras provincias o subprovincias o apoyar las propuestas por otros autores.

El presente trabajo consiste en la revisión y estudio de las especies de moluscos del Pacífico panameño presentes en la Colección de la Sociedad Panameña de Malacología (SPM) y en colectas personales. La colección consta de miles de ejemplares de gasterópodos, bivalvos y otros grupos no incluidos en este estudio. La distribución regional biogeográfica se ha efectuado a partir de la obra de KEEN (1971) con puntualizaciones concretas que se señalan en cada caso. Se han establecido siete categorías o grupos zoogeográficos dentro de la Provincia Pacífico - Panameña que contemplan los límites norte y sur dado para las 614 especies de este estudio.

Las categorías zoogeográficas son: 1. En toda la Provincia Pacífico-Panameña; 2. Especies norteñas con límite sur en Panamá (31 20' - 23 20' N a 7 12'); 3. Especies norteñas con límite norte en Chiapas, El Salvador, o Nicaragua y sur en Panamá (15 42' N a 7 12' N); 4. Especies sureñas con límite norte en El Salvador o Nicaragua y sur en Perú o Ecuador (4 15' S); 5. Especies sureñas con límite norte en Panamá o Costa Rica y sur en Perú o Ecuador; 6. Especies endémicas de Panamá; 7. Especies que se distribuyen en más de una provincia malacológica. Se han señalado, aparte, las especies cuyo primer registro para Panamá proviene del material estudiado.

Varios autores consideran, como factor relacionado con las distribuciones, al factor histórico señalando que es posible que grupos de especies con una historia paleogeográfica similar puedan compartir similares requerimientos fisiológicos y tolerancias, las cuales pueden reflejarse en patrones de distribución similar. La existencia de grupos faunísticos bien definidos puede haber sido causada por determinantes inconexos a la geografía presente y a los actuales climas marinos. Entre estos determinantes, según varios autores, deben ser considerados en los patrones de distribución presentes, la diversidad de especies del Terciario, la paleoecología del Cuaternario y, especialmente, los eventos del Holoceno y los movimientos faunísticos.

Se concluye que, la distribución actual en territorios amplios responde a factores climáticos, oceanográficos (principalmente térmicos), disponibilidad de recursos tróficos y a condiciones pasadas (paleocorrientes, paleoecología, etc.).