Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

The: bottom topography around Isla del Caño, to a distance of 11 km was determined during the Costa Rica expedition of the German Research Vessel Victor Hensen. A map resulting from that survey is presented in this paper. Additionally, sediment samples were taken using a box corer, along three transects, one on the north side of the island, one on the northwest and one on the east. The sediments around Isla del Caño are of tenigenous origin. with small contributions of carbonates from the island's coral reefs.

Coral reefs around Carrie Bow Cay, Belize, Central America were investigated in 1972 and reefs of the 10hn Pennekamp Coral Reef State Park off Key Largo, Florida in 1973. Both sites were resurveyed in 1997 and a new threat to coral health was found: a rather epizootic occurrence of other organisms overgrowing living coral. On the reef-flat of the Barrier Reef north of Carrie Bow Cay, there are fields of Acropora cervicornis and Porites porites, scattered over shallow sand-bottom. A large number of these corals show either "tufts" of blue-green algae, or fila­mentous "flags". Both may cover substantial portions of individual coralla; the living tissue disappeared at the of con­ tact area. Another type of overgrowth on living corals is represented by the red alga Metapeyssonnelia corallepida, as well as the brown alga Lobophora variegata. Both overgrow mainly Millepora complanata and Malcicornis, but a1so other corals with smooth surface, such as Porites porites and P. astreoides. This syndrome occurs about equally abundant around Carrie Bow Cay, Belize, and in reefs off Key Largo, Florida. A similar kind of tightly attached over­ growth is represented by the sponge Cliona caribbea. It was found regularly in the reefs around Carrie Bow Cay on a wide variety of coral species. An identical type of epizoism is represented by Chondrilla cf. nucula, which, so far, was observed only in Belize. All these new syndromes together amount to a considerable coral-degrading factor, which was not found in these reefs 25 years ago.

Sediment echosounder records (18 KHz) of 14 profiles were made in the fjord-like embayment of Golfo Dulce. Pacific of Costa Rica. to investigate morphology and sediment structure. The NW-SW section includes an oriental fault that is the main internal tectonic characteristic of the Gulf; that has a very steep slope and reaches 170 m in height. Two parallel. but less prominent tectonic faults are also evident on the echographs. The sediments in the flat inner basin consist mainly of turbidites, which reach the deepest part of Golfo Dulce by channels. leaving most of the slope sediments unaffected.

Life cycle stages responsible for fluctuations in population sizes have often been described as "key fac­tors". In this study, a key factor approach was used to examine the dynamics of a shallow-water gorgonian popula­tion from 1983-1996 near La Parguera Gil the southwest coast of Puerto Rico. Gorgonian abundances increased from 8.1 to 99.6 colonies/m2 between 1983 to 1985 and gradually declined to 57.3 colonies/m2 in 1996. These variations in population size are largely attributable to recruitment, which increased from 2.1 to 44.9 colonies/m2 between 1983 to 1985, and declined thereafter. Survival. of recruit colonies which was generally higher after periods of high recruit­ment also played a contributing role in these population fluctuations. In contrast, survival of large colonies (2:10 cm in height) was essentially constant (about 94.1%/yr), and consequently had negligible effects on variations in abun­dances. These results demonstrate that large colonies are no! a key factor underlying fluctuations in gorgonian popu­lations. However, this assessment of large colonies differs if the results are examined in a different conceptual con­text. The combination of high and constant large colony survival, and variable "reproductive success" (recruitment and recruit survival) conforms to the "bet-hedging" interpretation of life history pattern. According to bet-hedging theory, large colonies are essential to the persistence of populations.

A dry season nutrient survey was conducted in the Gulf of Nicoya. Costa Rica. The highest concentrations of nitrate and phosphate over the surveyed range ocurred at the deep waters off the gulf mouth. Vertical stratification kept the nutrient rich Equatorial Subsurface Water (ESW) at the deeper levels below the thermocline over most of the lower (outer) section of the Gulf. Higher tidal energy dissipation on the mid Gulf appears to be mixing this nutrients over the entire water column. Additionally two anchor stations were set at the western and eastern lower (outer) Gulf. There was a net flux into the Gulf of nitrate and phosphate at the west end, while at the east side nutrients are exported offshore. Survey data suggests that the major source of nitrate and phosphate for the embayment is the ESW, whereas silicate would be mostly provided by rivers. Our data and that of previous workers indicate that this pattern does not change in the rainy season. The influx of the ESW water into the Gulf of Nicoya may be dampening the seasonal signal due to runoff. at least for inorganic nitrogen and phosphorus, keeping relatively steady levels of these nutrients throughout the year over most of the Gulf.

Rainfall is a common phenomenon in tropical forests influencing the behavior of many animals, however, little is known about its post-occurrence effect on behavior. We investigated the effect of diurnal rainfall on the nocturnal activity of the wandering spider species Phoneutria reidyi in nights without rainfall. Our study included two different areas and periods: a coconut plantation, located 108 km from the city of Manaus, containing an area of 80 m x 80 m with 105 palms, from July 2014 to July 2015; and an area of 80 m x 80 m in a rainforest fragment in Manaus, from December 2015 to March 2016. Each night, we counted active spiders (found outside refugees) searching carefully on the vegetation and on the ground using a headlamp between 19:00-00:00. Spiders were not captured to avoid the effect of disturbance, and were measured by approaching a caliper rule. We used an index to measure the diurnal rainfall effect (DRE) which was the percentage of change in the number of active spiders at night after a diurnal rainfall, considering 100 % the number of spiders active at the previous or following night, without previous rainfall during the day. This pairwise approach was used to avoid seasonal bias and included 15 pairs of nights in the plantation, and 15 pairs in the forest. A total of 2 243 active spiders were counted. The number of active spiders was always smaller in nights after diurnal rainfall, with a mean reduction of 53.4 %. The abundance of active spiders reduced significantly in both areas after a diurnal rainfall, and the effect was not different between areas. Larger spiders (mostly adults) reduced their activity (-62.8 %) more than smaller spiders (juveniles, -48.5 %). The amount of rainfall during the day had no effect on the nocturnal activity, i.e., the effect of strong diurnal rainfall is similar to the effect of a weak rainfall. The air temperature did not change significantly at night after diurnal rainfalls. The seasonality of rainfall apparently has a weak or absent effect on the abundance of P. reidyi, which was approximately constant through one year. We believe that the moisture, which may affect the chemical cues of prey, is the major cause to reduce the active spiders after rainfall, but we discuss other potential causes. Smaller individuals are probably more active under less favorable conditions due to the stronger need of food for growing. If this effect of rainfall on the behavior is common for wandering spiders in general, the rainfall events may have important consequences for the entire community of arthropods and small vertebrates. We suggest that studies based on relative abundance of spiders should take in account this potential effect in collection and analysis of data. 

Parque Nacional Corcovado is famous for its terrestrial ecosystems but also has important but unappreciated coastal- marine environments. These environments, which have not been studied, include sandy beaches, rocky out-crops, soft and hard bottoms and coral reefs. We describe three intertidal rocky sites. list the coral species, and describe several coral communities from Corcovado. Species composition and distribution on the intertidal zone are similar to other areas on the Pacific coast of Costa Rica. Eleven species of scleractinian corals were found in the Park, a richness equivalent to other reefs in the country. The most important species were Pocillopora damicornis, Pocillopora elegans and Porites lobata. Pocillopora reefs were found in Corcovado, the y are common in other parts of the eastern Pacific but rare in Costa Rica. The Park is an important refuge for species of commercial value that have been depleted from most of the coast. This National Park, together with most of the other protected areas in the country. e.g. Isla del Caño. Santa Rosa and Manuel Antonio, have become the sole reservoirs and sources of larvae, juveniles and adults of many species for adjacent areas

In subtropical regions like the Chaco Serrano (33° S), rainfall has a marked seasonality, and water flood, caused by heavy rains, may have important consequences for dependent ecosystems. Conversely, the high pressure on available resources during dry periods can also affect the fauna diversity and distribution. Even though birds have shown to be excellent ecological indicators of these shifts in the environment, currently little is known about the avifauna of the Argentine Chaco Serrano phytogeographic district. Our aim was to study the resident bird population status in the Southern Chaco Serrano, its fluctuations in richness and abundance, and its relationship to seasonal variations, in monthly and annual hydroperiods. In order to assess the resident bird status over a two year period (2011 Mar.-2013 Feb.) we carried out 18 sampling surveys during pre-breeding (spring), breeding (summer) and non breeding periods (autumn-winter), in the Northeastern part of the Valle Fértil Natural Park, San Juan province, Argentina. During each site survey, we recorded bird assemblages found in six transects, and obtained bird abundance and species diversity. A mixed general linear model was employed to evaluate relationships between the studied variables. We found a total of 98 species of birds belonging to 33 families (44 resident species, 23 spring visitors, six summer visitors, two winter visitors and 23 with scarce registers). We also registered 68 of these species in both hydroperiods, 28 only during rainy periods and only two during the dry period. Both richness and abundance showed the highest values during the pre-breeding and rainy seasons, while different tendencies were detected during the isolated monthly rainfalls. These changes in bird densities were associated with the arrival of migratory species, mainly spring visitors, and probably in relationship with their reproductive activity, and to seasonal fluctuations in food resources. The Southern Chaco Serrano is a subtropical semiarid place that seems to be an important breeding habitat for many migrant bird species, which in turn promoted seasonal changes in species density and diversity, mainly during rainy years. This work contributed to our understanding on the causes of richness and abundance variations on birds, and will contribute to this important group management and conservation in this area.