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

Mass mortalities of sea fans (Gorgonia spp.) off the South and Central American coasts were reported in the 1980s. In some cases, populations never recovered. Widespread tissue mortality in G. ventalina and G. flabellum throughout the Caribbean was reported in 1997. Although colony mortality was apparently lower in the more recent epizootic, the geographic distribution of the disease appeared much greater. Tissue samples of affected colonies were found to be infected with a fungus (Aspergillus sp.) with was shown to be able to cause the disease in healthy sea fans. We describe observations on the early infection process and subsequent development of the disease. Based on these observations, we report the response of Gorgina spp. to infection by Aspergillus.

Epizootics of type II white-band disease (WBD II) can be confused with type I white-band disease (WBD I) and with bleaching. The only well documented cases of WBD II have been on Acropora cervicornis from the Bahamas, but descriptive reports indicate that it may be widespread. WBD n begins as a bleaching margin which pre­cedes a necrotic margin. The bleachíng margin usually progresses at a faster rate than the necrotic margin and can arrest, allowing the necrotic margin to catch up. In this case, the disease has the appearance of WBD I. Living polyps are found in the bleached zone although recovery has not been observed. A. bacterium, similar to Vibrio charcharia is always isolated from the surface mucapolysaccharide layers (SML) of the bleached zone, but not from the SML of unbleached areas.

Strombus galeatus is a gastropod distributed from the Gulf of California in Mexico to the Galapagos Islands in Ecuador. and as other strombid species. in the costarican coast is a resource of high overfishing with no governmental control or regulations and scarce biological information about the species. Biological studies on this conch natural populations from managed and unmanaged areas were conducted during a four year period (November 1993 to December 1997). Results showed that this conch is found in sandy-gravel bottoms and roost of them found in less than 15 meter deep areas. Shell growth is first done in length and lip formation and afterwards on lip thickness: shell morphology was found different in juvenile and adult stages. The shell represented 8O% of total fresh weight, and presented an external brownish and white colors with some spots inside it. This dioecious species, performed a special reproductive behavior: the female genital groove appeared thickned, males seek for females, and conchs used to form groups of more than two individuals (from which one used to be a female); mating is presume d and the female lays an egg mass from which the veliger larvae appears after 3 to S days. It is believed that their most important diet is macroalgae. No predation was observed upon the conchs during surveys; no shell damage was observed in adults and little in juveniles: few adult conchs were observed with scars in the in foot and other structures. This species seems to have a high regeneration potential in juvenile and adult stages. A parasitic isopod was found attached to the upper right side of the foot in 10 of thc 627 conchs observed.

The conch S. galeatus used to be a common gastropod in the Pacific coast of Costa Rica. but high exploitation levels have diminished natural stocks. A natural, unexploited, population was studied in San Miguel tidal pool at Cabo Blanco Absolute Reserve. from December 1993 through December 1997. using the mark-recapture method and biometrics. This population can inmigrate and emigrate from the mostly rocky-bottom pool by its western natural en trance. From a total of 627 marked conchs. 70.3 % were adults. 23,0 % subadults and only 6.7% were juveniles, and this pattern was constant throughout the survey. Males represented 51.4% or the population. females 43.7% and undetermined individuals 4,8%. An average of 74 % of the conchs were recovered during surveys (with a mean recapture index of 14.7 %), and only 26 % of the conchs were observed. Average adult, subadult and juvenile lengths were, respectively 183.2 mm (S.D. 9.5).162.8 mm (S.D. 5,7) and 132.1 mm (5.0, 15,0). Density was estimated as 500 conch/ha.

Nutrients, temperture, Secchi disk depth and dissolved oxygen spatial distributions were determined along the Puntarenas Estuary. Eleven sampling cruises look place in 1982 and twelve more were carried out during 1990-1992, collecting water samples on a surface and bottom basis along tile salinity gradient at six and nine stations, respectively. Salinity profiles indicated a partially mixed estuary during most of 1he cruises. although the strong tidal current ocasionally modified the pattern. During the second part of the study, the global concentration ranges for nitrate and phosphate were broader than those in the first part. Total and fecal coliforms (TC, FC) were determined 35 most probable number (MPN/100 ml) during six cruises of the second period in nine stations; results showed a typical situation of a very polluted estuary, with values in the range of less than 2 to 1.6 x 107 MPN/100 ml for TC and less than 2 to 9.2 x 106 ml MPN/100 ml for FC.

The water dynamics of the upper part of the Gulf of Nicoya were studied under high discharges of the Tempisque river. The salinity values close to freshwater found north of Chira island are the lowest reported for this lone. and have importance in mariculture planing. A salinity gradient is developed during low tide, indicating a strong stratification in the inner Gulf. High freshwater river discharge is coup led with an upstream bottom flow (sail wedge) that reacher; the head of the estuary. Under high river discharges, surface and bottom salinity values are correlated with depth, where vertical shear and tidal pumping must explain the high salinity values found in the bottom inward flow. A fish distribution pattern is proposed based on the observed salinity distribution and some field data. Salinity gradients appear to influence the concentration of fish in several relatively deep areas in the inner Gulf of Nicoya.

Growth of the mytilid species Mycella guyanensis was studied on a floating raft in Chira Island. inner Gulf of Nicoya. Costa Rica. Natural seed collection was done with 1.5 m long spat collectors suspended from a wooden raft. The collectors produced a total of 3 kg of seed each (202S seeds per collector) after three months, reaching a mean size of 19.4 mm and 0,79 g per seed. Seed mussels were retubed and resuspended for nine more months and reached a marketable size of 44.4 mm (S.D. 3.43) and 8.5 g (S.D. 1.98). Mean growth rates were 5.7 mm and 0.57 g per month, with a meat yield of 32.7% for the fifth month. As in other mollusks, growth rate was higher during the first six culture months.

The Golfo de Nicoya is among the largest tropical estuaries (1530km2) in Central America and the main. and already overexploited. fishing area of Costa Rica. It can be separated into a shallow (25m) interior part fringed by mangroves and mud flats and a deeper part that extends to the shelf edge to about 200m. In order to integrate available information on biomass. catches. food spectrum and dynamics of the main species populations of the system. a trophic model of 21 compartments was constructed by the use of tile ECOPATH II software. The larger portion of system biomass is confined to the benthic domain (18.4 gm-2, mangroves excluded, compared to 13.8 gm-2 for the pelagic domain). Mangroves, although only covering 1% of tile gulf area, contribute 76% to the system biomass, but only about 1%, to the system's primary production. Through their root system, their provide surface area for about 90% of the gulfs biomass of epifauna (12 gm-2), the second largest group of the model. It serves as food source for commercially important species and also fuels the system by the production of large amounts of pelagic larvae and faecal material. Based on these findings, it is emphasized that mangroves, even if they cover only small areas of an estuarine system. have a fundamental role in biomass distribution and flow pattern. and must be considered when constructing a trophic model of the system. Most of !he system's energy throughput is achieved from the trophic levels I to II (62%) and II to III (34%) as expected for coastal phytoplankton/detritus based systems. Total catch amounts to 3.38 gm-2. which is considered intermediate for tropical coastal systems. A high gross efficiency of the fishery (catch/ primary production) of 0.3% confirms the known high level of fisheries exploitation in the Golfo de Nicoya As shown by the model, shrimps occupy a central role within the gulf as converters of detritus and other food into prey biomass for many predators, that seem to be simultaneously affected by the overexploitation of this resource. The network summary stadistics computed for the model suggest an overall picture of!he Golfo de Nicoya as a system of a low degree of maturity, which seems to be characteristic for tidally driven. tropical estuarine systems. The results are compared and discussed with other published trophic models of coastal systems. Among these, is Golfo Dulce, a further Costarrican gulf system about 200km south of the Golfo de Nicoya.

A total of 136 sediment subsamples was analyzed (500 μm mesh screen) for benthic invertebrates from 26 box corer samples collected by the RV Victor Hensen (Dec. 7, 8, 9, 1993), at nine stations ranging in depth from 43 to 200 m in the Golfo Dulce embayment. Pacific coast of Costa Rica. A total of 1690 individuals and 69 species was found; polychaetes dominated the fauna in terms of number of individuals (1506) and species (47). Eight species of polychaetes accounted for 73% of the total number of individuals: Prionospio (Minuspio) sp. A (19.53%) Aricidea (Acesta) catherinae (13.31%), Levinsenia gracilis (11.00%), Aphelochaeta longisetosa (10.18%), Paraprionospio pinnata (6.63%) Cossura brunnea (5.27%), Mediomastus californiensis (3.61%), and Scoletoma platylobata (3.43%). No organisms were collected at the two deepest statiQns (200 m) located inside Golfo Dulce; however, a diverse fauna was found at similar depths II the embayment mouth and in waters shallower than 100 m inside Golfo Dulce. The station located at the sill (75 m) was the most diverse (37 species). The species composition of the fauna found during this study has little resemblance to that reported for Golfo Dulce in 1976. Diversity (H') and Evenness (J'), however, were similar in both surveys. The results of cluster analyses performed on the 1976 and 1993 data sets yielded two main groups of stations. One group was made of the stations located at the mouth and shelf, while another group included those located inside Golfo Dulce. The fauna of the sill sediments may represent a transition zone between the environments characteristic of the entrance to Golfo Dulce and those inside the embayment. The fluctuating bottom conditions of hypoxia-anoxia characteristic of most of Golfo Dulce, in addition to the likely impact of strong El Niño in the marine ecosystems, might be the causes for drastic shifts in species composition and abundance. Golfo Dulce is still a relatively unpolluted embayment, but an Integrated Area Management Plan is urgently needed. This paper, in addition to those already published resulting from the RV Victor Hensen Expedition, are a step towards this goal.