David Bone

Sedimentation Rates and Metal Content of Sediments in a Venezuelan Coral Reef

The sedimentation rate and metal content in trapped sediments were determined at four localities at the Parque Nacional Morrocoy and for a sampling period of 1 year. The sedimentation rate was inversely related to the distance from the main terrestrial sources of sediment and ranged from 44+7 to 281+46 g m-2d -n (mean+SE) for the farthest two localities (11 km apart). February through May showed the highest sedimentation rate considering all localities. Except for Ca and Hg, metals in sediments also varied inversely to the distance from terrestrial sources and ranged as follows: AI 1.01-2.57, Fe 0.70-2.08, Ca 22.3-34.8 in %; and Zn 44.6-77.9, V 19.9-41.8, Pb 18.1-35.6, Cr 18.1-31.9, Cu 6.8-40.3, Hg 0.269-0.325 in lag g i based on dry weight. A common source of metal pollution is suggested from the positive and significant correlation found between the concentrations of most metals. Only Hg was not correlated with any other metal and its concentration was relatively constant for all localities. Based on our results we speculate that reef environments of P.N. Morrocoy are being affected by long-term continuous load of sediment moderately contaminated, brought about by drainage of the neighboring rivers.

Influence of riverine outputs on sandy beaches of Higuerote, central coast of Venezuela

The influence of riverine outputs from the Tuy River on the coastal processes of near sandy beaches was assessed by measuring the physical and chemical characteristics of water and sediment samples at eight sites along the north central Venezuelan coast and from the rivers that flow through this region into the sea (Tuy, Capaya, Curiepe) during two field surveys. In addition, the behavior of the Tuy River discharge plume was evaluated using remote sensors, and its effect on the population abundance and size structure of the clam Tivela mactroides was determined. Of the three rivers evaluated, the Tuy River had the highest impact on the coastal zone (789.15 ± 190.63 km 2 ) in terms of flow rate (246.39 m 3 s -1 ), nutrients (659.61 ± 503.27 g s -1 total nitrogen; 52 ± 53.09 g s -1 total phosphorus) and sedimentary material (9320.84 ± 9728.15 g s -1 ). The variables measured (salinity, total nitrogen and phosphorus, pH, turbidity, and total organic carbon) showed a spatial gradient along the coast. Tivela mactroides had the highest biomass and density (9126.8 ± 1562 g m -2 ; 9222.22 ± 1976.72 ind m -2 ) at the sites farthest from the river mouths and smaller sizes (< 13 mm long) at sites close to the river mouths. The Tuy River plume modifies the functioning of the coastal system processes by discharging large amounts of nutrients and sedimentary material into the water column, which are then distributed by marine currents and alongshore transport. These contributions are used by T. mactroides populations, which show high abundances and differentiation in size structure along this coastline.

Ecological aspects of syllids (Annelida: Polychaeta: Syllidae) on Thalassia testudinum beds in Venezuela

The spatial and temporal variations of syllids associated with the tropical Thalassia testudinum were studied at four seagrass beds in the Morrocoy National Park. The epifaunal syllids were collected at quarterly intervals throughout one year using a modified suction sampler. Possible relationships between sampling sites, months and species were evaluated by Principal Components Analysis. The spatial-temporal variability of the predominant species was tested by means of a 2-factor ANOVA with the sampling sites and months as factors. A total of 1138 individual syllids were collected, belonging to 41 species and 12 genera, of which Branchiosyllis, Exogone, Odontosyllis, Sphaerosyllis and Syllis showed the highest diversity. Spatial variations were defined by the species of Branchiosyllis (B. exilis, B. lorenae, B. oculata) whereas temporal variability was defined by certain species of Syllis (S. beneliahui, S. broomensis and S. prolifera), the latter also being the most species rich genus present. Of the 41 species found, only these six showed consistent presence—absence and abundance patterns. Species richness and abundance were significantly higher in March at all sampling sites. Collectively, the syllid fauna of the Morrocoy seagrass beds was richer than recorded from other similar habitats. These findings are discussed in relation to the physical and biotic factors that may affect the variability of syllid populations in these seagrass habitats.

Widespread local chronic stressors in Caribbean coastal habitats

Coastal ecosystems and the livelihoods they support are threatened by stressors acting at global and local scales. Here we used the data produced by the Caribbean Coastal Marine Productivity program (CARICOMP), the longest, largest monitoring program in the wider Caribbean, to evidence local-scale (decreases in water quality) and global-scale (increases in temperature) stressors across the basin. Trend analyses showed that visibility decreased at 42% of the stations, indicating that local-scale chronic stressors are widespread. On the other hand, only 18% of the stations showed increases in water temperature that would be expected from global warming, partially reflecting the limits in detecting trends due to inherent natural variability of temperature data. Decreases in visibility were associated with increased human density. However, this link can be decoupled by environmental factors, with conditions that increase the flush of water, dampening the effects of human influence. Besides documenting environmental stressors throughout the basin, our results can be used to inform future monitoring programs, if the desire is to identify stations that provide early warning signals of anthropogenic impacts. All CARICOMP environmental data are now available, providing an invaluable baseline that can be used to strengthen research, conservation, and management of coastal ecosystems in the Caribbean basin.

Polychaeta Diversity in the Continental Shelf Off the Orinoco River Delta, Venezuela

Coastal waters are mainly influenced by two large spatial scale processes: upwellings and river inputs (Mann & Lazier, 2006). Rivers are the main conduits of water, dissolved and particulate organic matter, salt, and other organic materials from the continents to the sea (Alongi, 1998). In Venezuela, the largest watercourse is the Orinoco River, covering a total basin of 106 km2 and discharging an average of 1,080 km3/yr of water, and 150x 106 tons3/yr of sediment to the Atlantic Ocean, representing the fourth largest river of the world in terms of discharge (Alongi, 1998). Several authors have shown that the Orinoco’s river plume can extend up to 100 km from the coast line, during the rainy season, influencing the salinity patterns, coastal currents, suspended materials and nutrient concentrations in the Venezuelan Atlantic coast and the Caribbean Sea (Muller-Karger et al., 1989; Penchaszadeh et al., 2000). The dispersion of the riverine front follows a northwest direction due to the influence of the northeasterly trade winds and the Guayana current flow. The surface plume is well-mixed inshore but it is stratified on the outer shelf, creating unique environmental conditions that greatly modify the marine waters and sediments. Very scarce information was available for this Atlantic area until recent years, as the Venezuelan government has undergone offshore gas exploration activities in the continental shelf off the Orinoco River delta (Gomez et al., 2005, Martin & Bone, 2007). This effort has allowed the scientific community to conduct large multidisciplinary base line studies for this Atlantic region, characterized by a large continental shelf, partly influenced by the Orinocos continental waters, with salinity values ranging from 0.25 to 36.92‰ (Martin & Bone, 2007), and a steep slope, reaching more than 2,500 m deep. These studies have included the characterization of the environmental and biological settings of the area, including the benthic component. The benthic community has been recently reported in terms of the main groups inhabiting these large soft-bottom areas (Bone et al., 2007), where polychaetes represented the most important one, achieving more than 64% of the total macrofaunal abundance. The biodiversity knowledge of the polychaeta fauna in Venezuela has been traditionally focused on shallow water areas. Previous studies have revealed a total of 40 families, 138 genera and 206 species for the Caribbean coast (Bone & Linero, 2003), but there is no previous information for the Atlantic region or deep waters. In the course of this study we

Correction: Widespread local chronic stressors in Caribbean coastal habitats

[This corrects the article DOI: 10.1371/journal.pone.0188564.].

Monitoring coastal pollution associated with the largest oil refinery complex of Venezuela

This study evaluated pollution levels in water and sediments of Península de Paraguaná and related these levels with benthic macrofauna along a coastal area where the largest Venezuelan oil refineries have operated over the past 60 years. For this, the concentration of heavy metals, of hydrocarbon compounds and the community structure of the macrobenthos were examined at 20 sites distributed along 40 km of coastline for six consecutive years, which included windy and calm seasons. The spatial variability of organic and inorganic compounds showed considerably high coastal pollution along the study area, across both years and seasons. The southern sites, closest to the refineries, had consistently higher concentrations of heavy metals and organic compounds in water and sediments when compared to those in the north. The benthic community was dominated by polychaetes at all sites, seasons and years, and their abundance and distribution were significantly correlated with physical and chemical characteristics of the sediments. Sites close to the oil refineries were consistently dominated by families known to tolerate xenobiotics, such as Capitellidae and Spionidae. The results from this study highlight the importance of continuing long-term environmental monitoring programs to assess the impact of effluent discharge and spill events from the oil refineries that operate in the western coast of Paraguaná, Venezuela.