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

The year 1996 had a high pluviosity in Morrocoy National Park (western coastal zone, Venezuela) and low salinity in December 1996 affected the seagrass beds, dominated by Thalassia testudinum. Patches without T. testudinum were observed in localities of the park that used to have very dense populations of this plant. Sampling was done at Las Luisas to determine leaf productivity, turnover rate, short shoot density and relative biomass of plant sections, in order to compare with data obtained in September 1996, previous to the event. Green leaves, roots and rhizomes were the most affected parts. Mean green leaf biomass decreased in January and February 1997 to 5% of the plant's total biomass; mean root biomass decreased in March to 40% and mean rhizome biomass decreased in February to 30%. The density of the active short shoots decreased to a minimum in February, but in April it reached a value similar to that of September 1996. The density of the inactive short shoots decreased to a minimum in March, and they dissappeared in April, matching the increasing density of the active short shoots between these two months. In February 1997, 56% of the inactive short shoots showed evidence of leaf initiation. In January 1997 the leaf productivity and turnover rate values (2.72 it 0.35 g/m2/d and 2.15% leaf DW/d) were similar to the annual mean previously determined from Las Luisas (2.35 it 0.72 g/m2/d and 1.96% leaf DW/d). Nevertheless, the values of productivity and turnover rate detected at Las Luisas in April 1997 (4.88 it 2.14 g/m2/d and 4.66% leaf DW/d) were higher than those values previously reported for this location. In response to the mortality episode, the leaf productivity and turnover rate of T testudinum increased and the leaf initiation was activated in the inactive short shoots.

Some atmospheric properties in the Pacific and Caribbean marine basins close to the Central American Isthmus and their possible interconnections are analized, based on a statistical study. The band describing southern Nicaragua is taken as reference, because it has the least orographic features that may disturbe the Trade winds flow­ing from the northwest (NW) and from the southeast (SE). The atmospheric properties are associated to the incidence of synoptic phenomena like tropical cyclones and their probability of crossing the Isthmus with minimun energy loss. The warm El Niño-Southern Oscillation (ENSO) eventsproctuced a systematic weakening of sporadic cyclone type events in the western Atlantic, while in the eastern Pacific, because of surface water temperatures higher than 27°C, they are reinforced. During the transition from warm-ENSO to cold-ENSO events, there are interconnections between both oceanic basin with cyclonic systems crossing the Isthmus, mainly across the Nicaragua depression (from the Atlantic to the Pacific); and with only one Case, through Tehuantepec (from the pacific to the Atlantic). During the cold-ENSO events, similar.conditions to the transition stage can be expected; i.e., the number of events increased in the Atlantic Basin while in the Pacific they are reduced.

In order to increase the scientific knowledge about the ingestion and digestion processes of the microalga Tetraselmis suecica by veliger larvae, we did a comparative analisis of feeding kinetics of two Caribbean conch lar­vae: Queen conch, Strombus gigas, and Pighting conch, Strombus pugilis. These kinetics have been determined in a direct way by means of epifluorescence microscopyc with this technique the potential nutritive value of different microalgae, can be detected in terms of their ingestion and digestion rates. Given the all to fluorescence of algal cells and transparency of both larvae tissues and shell, the algae within the stomach, their lisis and subsequent degradation are observed. The evolution of the ingestion and digestion processes can be follow in live larvae, where other events like the expulsion of intact algae cells initially ingested by the larvae can be observed. The nutritional effects of T. suecica on veliger larvae are explained infunction of a cromatic scale of four nutritional stages, and by means of temporal and absolute ingestion and digestion indices.

The basal behaviour and relationship with organic carbon (Corg) content and prevailing granulometric fractions, of organic nitrogen (Norg), total phosphorus (P-total) and C/N ratio in surface sediments of Chacopata lagoon, Sucre State, Venezuela, Were studied. Concentrations and spatial gradients were determined in sixteen stations following a common method for marine sediments. Norg concentrations varied between 0.102 and 0510% (x = 0.237%), total phosphorus between 0.012 and 0.094% (X = 0.058%) and C/N ratio between 9.27 and 44.47 (x = 20.53). The higher contents of Norg and total phosphorus are from sections with an.abundance of mangroves, marine phanerogams, macroalgae, benthonic biomass and migratory birds shelters. The C/N ratio shows the typ­ical values for carbonated sediments, indicating that the nitrogenous compounds are rapidly degraded and the organic matter presents itself as humic substances. This parameter was moderately associated with silt and clay, and showed antagonism with sand, whereas Norg and phosphorus showed no correlation with them. The organic contribution is purely autochthonous: no anthropogenous contributions were found.

Diversity and abundance of benthic macro fauna associated to Thalassia testudi11u m were studied at Ensenada de Reyes, Mochima Bay, in the northeastem coast of Venezuela. Samples were taken monthly in six stations, three at 1 m in depth and three at 6 m, between December 1992 and February 1994, using a quadrat of 0.25 m2 for collecting plants and sediment; each sample was washed with seawater through a 1 mm sieve. The speeimens were fixed in 6% formaldehyde. A total of 1 722 organisms (6 888 ind . m2) and 127 species of macroinvertebrates were collected. Mollusks dominated with 53 species, followed by polychaetes (40), erus­taceans (18) and echinoderms (8). Remaining groups were represented by 1-2 species. The highest abundance was in October (214 specimens), and the lowest in December 1993 (79 specimens). Specific richness was between 47 species in October and 18 in May 1993. Mean species diversity was 2.79-1.36 bits/ind. There were differences (ANOVA p

The concentration of copper, cadmium and lead in superficial sediment, water and the fish Cyprinodon dearborni was determined in two coastal lagoons of Sucre State, Venezuela. Chacopata lagoon is hyper saline while Los Patas lagoon is hypo saline and receives significant wastewater from Cumaná city. Water, sediment and fish samples were collected in February 1998. In the laboratory, samples underwent acid digestion and were analyzed by atomic absorption spectophotometry. The mean values of the metals in C dearborni from the Chacopa­ta lagoon were: 159.26 ± 210.68 μg/g for Cu, 44.71 ± 45.58 μg/g for Cd; and 9.31 ± 23.34 μg/g for Pb, while for Los Patos lagoon the mean values were: 64.88 ± 16.30, 19.48 ± 5.81 lUllÍ 22.85 ± 20.00; respectively. In the water column, the metal concentration ranges were; 2.3-11.6, 3.9-5.4 and 21-32 mg/l for copper, cadmium and lead, respectively. These results suggest that metal levels in sediment, water column and organisms in both lagoons do not differ, except for lead, even though only Los Patos receives waste water.

The benthic fauna and diel variation in a shallow seagrass bed (Thalassia testudinum) were studied in Playa Mero, Venezuela Samples of organisms and sediments were taken using PVC cylinders, 5 cm in diameter, along a transect perpendicular to the coast Seagrass cover, shoot density and biomass were estimated. The sea­ grass cover was homogeneous a10ng the transect. The intermediate zone had the highest number of shoots and of above- ground and rhizome biomass. Composition and.abundance of benthic organisms were related with seagrass and sediment characteristics. Sediment organic matter contentand organism abundance were highest near the shore. Molluscs, polychaetes, oligochaetes and nematodes were the most abundant groups. Species richness-was higher in daytime (40 versus 28 at night). Gastropods were the most abundant organisms both at day and night while polychaetes and crustaceans increased during the day, and holoturids were more numerous at night.

The development or Strombus pugilis larvae was studied over a period of 31 days in laboratory culture. Experiments were conducted al 29°C ± 1°C. Veligers were reared at 200 larvae·l-1 in 4 liter containers. Larvae were fed with the microalgae Tetraselmis suecica at l000 cells·l-1. Nineteen development characteristics are described from hatching to settlement. Based on chronological appearance of the characteristics three sets (larval maturation, metamorphic processes and settlement) and seven development stages are proposed.

In October 1995, a mass bleaching event was reported in the Western Atlantic, including areas such as Belize, where little bleaching damage had been recorded previously. Reports based on remote sensing data suggest­ ed that sea temperatures in the region were warmer than normal during early October. In November, a monitoring team found that bleaching was well above background levels on the patch reefs around San Salvador Island, Bahamas, a location well out of the main influences of the wider Caribbean. These San Salvador patch reefs have been studied in a long-term monitoring project since 1991. The team found that the overall bleaching level in November was 14% of all coral colonies counted on the three monitored reefs. Bleaching affected the various coral species differently. Agaricia sp. were the most affected, as measured both by the number of colonies affected and by the total coral sur­face area bleached; however, Agaracia was not the most abundant species on any of the sampled reefs. Of those corals colonies affected, the percent of surface area bleached.differed from reef to reef. On Lindsay's Reef, an average of 42.2% of the surface area of the bleached corals was affected, while at Rice Bay, the average was 31.3%, and at French Bay, the average was 15.2%. Sea temperatures taken at each reef during the census were normal for this lime period. Seven corals were marked and photographed at Lindsay's Reef for future analysis. In addition, samples of the surface mucopolysaccharide layer (SML) from bleached and non-bleached Agaricia sp. were taken for microbiolog­ical analysis. The survey and microbiological sampling were repeated in February. One of the marked coral colonies had 100% of its surface bleached in November; by February, it was well on the way lo complete recovery. Metabolic comparisons of bacteria from the SMLs showed that the normal microbiota, which had changed during bleaching, returned to a normal distribution in recovery. The February 1996 census showed that bleaching patterns had remained the same, but that the extent and severity of the bleaching had returned 10 background levels. Sea temperatures at this time were almost 1°C below normal for the time period. By July of 1996, most corals affected by the bleaching event had recovered, with the number damaged or dead representing <1% of the total hard coral cover on these reefs. While ¡he extent of this bleaching event was significant, the long-term impact was negligible.

This study, done at Morrocoy National Park, Venezuela, describes and analyzes tumor-like growths resul­ting from the invasion of Plexaura flexuosa axial skeleton and surrounding tissues by filaments of the chlorophycean Entocladia endozoica. A stratified random sampling was done in three transects of 72 m2 each at 4,8 and 12 m depth. At each depth, all tumors present in nine randomly chosen colonies of P. flexuosa were cut and preserved and five tu­mors ere collected in each of the remaining colonies on the transect. The external and internal morphology of the tu­mors and the spatial relationship of the algal filaments with the axial rod of the octocoral was studied through stan­dard microscopy and scanning electron microscopy. Transmission electron microscopy was used for taxonomic pur­poses and to identify the reproductive stage of the filaments. In addition, optical fiber sensors were used to detect the light path of laser beam projected from a discharge lamp through the coenenchymal material of the tumor, in order to find out if ambient light can reach the algal filaments. Results showed that the E. endozoica filaments in a tumor of P. Flexuosa were found on the tips of axis projections of variable size that were perpendicular to the main rod. The­se projections often penetrate the axial sheath towards the coenenchyma and could contact the ambient water through fractures of the external wall of the tumor. Reproductive filaments were only found on axis projections that had grown enough to penetrate the axial sheath and the coenenchyma. Filaments on the main axial rod or on small projections were in the vegetative stage. The laser study indicated that the light could at least reach the coenenchymal material where the reproductive filaments are found. We postulate a mechanism through which the oetocoral tries to get rid of the algal filaments by pushing them out by the development of projections, thus causing vegetative filaments to be­ come reproductive. Light may also contribute to this transformation.