Southeastern Caribbean Sea Research Articles

A new species of Lysmata (Crustacea, Decapoda, Hippolytidae) from Venezuela, southeastern Caribbean Sea

A new species of Lysmata (Crustacea, Decapoda, Hippolytidae) from Venezuela, southeastern Caribbean Sea

Evolution of the Grenada and Tobago basins and implications for arc migration

The tectonic mechanisms controlling how volcanic arcs migrate through space and geologic time within dynamic subduction environments is a fundamental tectonic process that remains poorly understood. This paper presents an integrated stratigraphic and tectonic evolution of Late Cretaceous to Recent volcanic arcs and associated basins in the southeastern Caribbean Sea using seismic reflection data, wide-angle seismic refraction data, well data, and onland geologic data. We propose a new tectonic model for the opening of the Grenada and Tobago basins and the 50–250-km eastward jump of arc volcanism from the Late Cretaceous Aves Ridge to the Miocene to Recent Lesser Antilles arc in the southeast Caribbean based on the mapping of three seismic megasequences. The striking similarity of the half-graben structure of the Grenada and Tobago basins that flank the Lesser Antilles arc, their similar smooth basement character, their similar deep-marine seismic facies, and their similar Paleogene sediment thickness mapped on a regional grid of seismic data suggest that the two basins formed as a single, saucer-shaped, oceanic crust Paleogene forearc basin adjacent to the now dormant Aves Ridge. This single forearc basin continued to extend and widen through flexural subsidence during the early to middle Eocene probably because of slow rollback of the subducting Atlantic oceanic slab. Rollback may have been accelerated by oblique collision of the southern Aves Ridge and southern Lesser Antilles arc with the South American continent. Uplift and growth of the southern Lesser Antilles arc divided the Grenada and Tobago basins by early to middle Miocene time. Inversion of normal faults and uplift effects along both edges of the Lesser Antilles arc are most pronounced in its southern zone of arc collision with the South American continent. The late Miocene to Recent depositional histories of the Grenada and Tobago basins are distinct because of isolation of the Grenada basin by growth and uplift of the Neogene Lesser Antilles volcanic ridge.

A new species of Lysmata (Crustacea, Decapoda, Hippolytidae) from Venezuela, southeastern Caribbean Sea

Lysmata udoi n. sp., a new peppermint shrimp, is described from Venezuela, southeastern Caribbean Sea. All individuals were collected from dens of the toadfish Amphichthys criptocentrus (Valenciennes, 1837) in the subtidal zone. This new species can be distinguished from other closely related species of Lysmata by the number of teeth, length and shape of the rostrum, the relative length of the antennular peduncle, and the number of carpal articles of the second pereiopod. The color pattern is distinctive. The fourth abdominal segment almost lacks color, but bears a posterior red thin line with three short forward projections. Morphological and molecular characters demonstrate that L. udoi n. sp. is most closely related to the Gulf of Mexico L. boggessi Rhyne and Lin, 2006 and the Caribbean L. rafa Rhyne and Anker, 2007 and L. ankeri Rhyne and Lin, 2006. Field observations suggest that L. udoi n. sp. is a protandric simultaneous hermaphrodite, with a primary male phase followed by a simultaneous hermaphrodite phase.

Receiver function study of the crustal structure of the southeastern Caribbean plate boundary and Venezuela

We have investigated crustal thickness and composition across the southeastern Caribbean plate boundary with the receiver function technique. We used teleseismic data recorded by a temporary broadband array deployed under the BOLIVAR project and the permanent national seismic network of Venezuela. We used the primary P‐to‐S conversion and crustal reverberations to estimate crustal thickness and average crustal VP/VS ratio over the region. We observe large variations in crustal thickness and Poisson's ratio. Estimated Moho depth ranges from ∼16 km beneath the southeastern Caribbean Sea to ∼52 km beneath northeastern Venezuela and the Venezuelan Andes. There is a good correlation between crustal structure and tectonic terranes. Data from the Precambrian Guayana Shield suggest that the underlying crustal structure is relatively uniform with a moderate thickness (∼37 km) and an intermediate composition. A thick crust is found below the foreland basins. The two mountain systems in northern Venezuela, the Serrania del Interior and the Serrania del Falcon, have a thin crust with arc composition and are likely dynamically supported by elastic rebound or underthrusting of the oceanic plateau that characterizes the southern Caribbean. On the other hand, the Venezuelan Andes and Perija Range on the western side of the country are probably isostatically balanced by thick crustal roots.

On the absorption of light in the Orinoco River plume

The spectral absorption coefficients of particles (phytoplankton and detritus) and colored dissolved organic matter (CDOM) were measured in the Orinoco River plume in the Gulf of Paria (GOP) and southeastern Caribbean (SEC) Sea in the wet (June, October) and dry (February, March) seasons of 1998, 1999, and 2000. During both seasons and over the three years, there was substantial patchiness in water color off the Orinoco Delta, and CDOM accounted for 61–98% of the total light absorption coefficient at 440 nm in the GOP and SEC at most stations ( x ¯ ≈ 89 ± 7.6 % ; N = 44 ). Detritus dominated absorption due to particles ( x ¯ ≈ 70 ± 20 % ; N = 27 ) near the Orinoco Delta, while phytoplankton dominated particle absorption in the northern GOP and in the SEC ( x ¯ ≈ 65 ± 17 % ; N = 42 ). Absorption coefficients of CDOM, phytoplankton, and detritus at 440 nm ranged 0.23–2.59, 0.016–0.55, and 0.002– 0.545 m - 1 during the dry seasons, and 0.38–3.21, 0.013–0.113, and 0.003– 0.754 m - 1 during the wet seasons, respectively. The ratio of CDOM to phytoplankton absorption in the Orinoco plume [ a CDOM ( 440 ) / a ph ( 440 ) ] ranged from 3.3 to 139 ( x ¯ ≈ 30 ± 24 ; N = 44 ), which are extremely high compared to other coastal regions. These values are explained by the unique characteristics of the Orinoco River (e.g. low phytoplankton biomass and high discharge of sediments and CDOM which inhibit phytoplankton growth). Our results demonstrate that it is fundamentally difficult to estimate phytoplankton absorption or chlorophyll- a concentrations from space using wavelengths in the blue portion of the light spectrum in coastal and estuarine waters affected by large rivers like the Orinoco. New chlorophyll algorithm development efforts need to focus on the red wavelengths (e.g. fluorescence peak) where CDOM influence is minimal.

Caridean and sergestid shrimp from the Kick'em Jenny submarine volcano, southeastern Caribbean Sea

[Kick'em Jenny is a submerged active volcano located in the southeastern Caribbean off the island of Grenada. It is the southernmost active volcano, and the only active submerged volcano, in the Lesser Antilles volcanic arc. In 2003, an expedition to the volcano returned several specimens of caridean and penaeoidean shrimp collected at depths of approximately 260 m. The specimens represented three species, two oplophorids (Janicella spinicauda and Oplophorus gracilirostris) and one sergestid (Sergia sp., close to S. robusta). The latter is the first penaeoid shrimp recorded from the vicinity of any hydrothermal vent system. Interestingly, many of the shrimp were found immobile, lying on their side on the floor of the submerged volcano's caldera. All three species are known members of the mesopelagic community, raising the possibility (explored in a separate paper by Wishner et al., submitted) that they were killed or entrapped by the toxic volcanic gases in the water column. All three species are thus considered vagrants (sensu Martin & Haney, submitted) rather than vent endemics, as there are no obvious indications that any of the three species is modified for life at underwater hydrothermal regions. Kick'em Jenny est un volcan actif submerge situe dans les Caraibes sud-est, au large de l'ile de Grenade. C'est le volcan actif le plus meridional, et le seul volcan submerge actif, dans l'arc volcanique des Petites Antilles. En 2003, une expedition sur le site du volcan a rapporte plusieurs specimens de crevettes carides et peneides, recoltes a des profondeurs d'environ 260 m. Les specimens representent trois especes, deux Oplophoridae (Janicella spinicauda et Oplophorus gracilirostris ) et un Sergestidae (Sergia sp., proche de S. robusta). Cette derniere espece est la premiere crevette peneide signalee au voisinage d'un systeme de cheminees hydrothermales. Curieusement, beaucoup de crevettes ont ete trouvees immobiles, reposant sur le cote sur le sol de la caldera du volcan submerge. Les trois especes sont des membres connus de la communaute mesopelagique, suggerant la possibilite (exploree dans un article de Wishner et al., soumis) qu'elles ont ete tuees ou piegees dans la colonne d'eau par les gaz volcaniques toxiques. Toutes les trois sont ainsi considerees comme vagabondes (sensu Martin & Haney, soumis) plutot qu'endemiques des cheminees, car il n'y a pas d'indications claires qu'aucune de ces especes ne soit modifiee pour la vie dans les regions sous-marines hydrothermales., Kick'em Jenny is a submerged active volcano located in the southeastern Caribbean off the island of Grenada. It is the southernmost active volcano, and the only active submerged volcano, in the Lesser Antilles volcanic arc. In 2003, an expedition to the volcano returned several specimens of caridean and penaeoidean shrimp collected at depths of approximately 260 m. The specimens represented three species, two oplophorids (Janicella spinicauda and Oplophorus gracilirostris) and one sergestid (Sergia sp., close to S. robusta). The latter is the first penaeoid shrimp recorded from the vicinity of any hydrothermal vent system. Interestingly, many of the shrimp were found immobile, lying on their side on the floor of the submerged volcano's caldera. All three species are known members of the mesopelagic community, raising the possibility (explored in a separate paper by Wishner et al., submitted) that they were killed or entrapped by the toxic volcanic gases in the water column. All three species are thus considered vagrants (sensu Martin & Haney, submitted) rather than vent endemics, as there are no obvious indications that any of the three species is modified for life at underwater hydrothermal regions. Kick'em Jenny est un volcan actif submerge situe dans les Caraibes sud-est, au large de l'ile de Grenade. C'est le volcan actif le plus meridional, et le seul volcan submerge actif, dans l'arc volcanique des Petites Antilles. En 2003, une expedition sur le site du volcan a rapporte plusieurs specimens de crevettes carides et peneides, recoltes a des profondeurs d'environ 260 m. Les specimens representent trois especes, deux Oplophoridae (Janicella spinicauda et Oplophorus gracilirostris ) et un Sergestidae (Sergia sp., proche de S. robusta). Cette derniere espece est la premiere crevette peneide signalee au voisinage d'un systeme de cheminees hydrothermales. Curieusement, beaucoup de crevettes ont ete trouvees immobiles, reposant sur le cote sur le sol de la caldera du volcan submerge. Les trois especes sont des membres connus de la communaute mesopelagique, suggerant la possibilite (exploree dans un article de Wishner et al., soumis) qu'elles ont ete tuees ou piegees dans la colonne d'eau par les gaz volcaniques toxiques. Toutes les trois sont ainsi considerees comme vagabondes (sensu Martin & Haney, soumis) plutot qu'endemiques des cheminees, car il n'y a pas d'indications claires qu'aucune de ces especes ne soit modifiee pour la vie dans les regions sous-marines hydrothermales.]

Planktic foraminifers and hydrography of the eastern and northern Caribbean Sea

The distribution of living planktic foraminifers and their relation to the hydrography of the Caribbean Sea was investigated in plankton net tows and surface sediment samples taken along the Antilles island arc during April/May 1996. The planktic foraminiferal community was strongly influenced by spatial variations in salinity that were largely due to the influx of Orinoco River water into the southeastern Caribbean Sea and inflowing Sargasso Sea water in the north. Along the Antilles island arc, Globigerinoides ruber was the dominant species in the surface waters throughout. In the southeastern Caribbean Sea, where Orinoco River outflow influences the planktic community, standing stocks of planktic foraminifers (>100 μm) between 4 and 50 specimens m −3 were medium to low. The southeastern faunas between Tobago and Guadeloupe were characterized by increased proportions of Neogloboquadrina dutertrei. Highest standing stocks of 159 specimens m −3 in the upper 20 m of the water column were recorded in the northeastern Caribbean Sea and the assemblages were characterized by high proportions of Globigerinita glutinata, associated with cyclonic eddies. In the Anegada Passage, where Sargasso Sea water flows into the Caribbean Sea, low standing stocks of 18 specimens m −3 indicate oligotrophic conditions. Together with the oligotrophic surface waters, the Subtropical Underwater enters the Caribbean Sea through the Anegada Passage in water depths between 100 and 300 m. These waters are characterized by higher concentrations of Globorotalia truncatulinoides relative to the adjacent water masses. Comparison of the living planktic foraminiferal fauna with empty test assemblages from the water column and from surface sediments shows that differences in the faunal composition mostly correspond to the distribution of water masses and to the differential dissolution of species. In the vicinity of islands Globigerinoides ruber reaches higher relative frequencies than in the open ocean, pointing towards a higher tolerance of this species towards neritic conditions than in other species.

LARVAL DEVELOPMENT OF MEGALOBRACHIUM ROSEUM (DECAPODA: ANOMURA: PORCELLANIDAE) UNDER LABORATORY CONDITIONS

Abstract The larval development of Megalobrachium roseum is completely described and illustrated on the basis of laboratory-reared material obtained from four ovigerous females captured on rocky bottoms of shallow waters in the southeastern Caribbean Sea. Megalobrachium roseum hatches as a prezoea of less than 120 minutes duration, and then molts through two subsequent zoeal stages of 5–7 and 6–8 days duration, respectively, at 25°C and 37‰ salinity, before attaining megalopal stage. Morphology of the zoeal and megalopal stages of M. roseum is compared with those of the three other species of Megalobrachium for which the larval development has been described (i.e., M. pacificum, M. poeyi, and M. soriatum).

PHYTOPLANKTON COMMUNITY STRUCTURE: TEMPORAL VARIABILITY IN A TROPICAL UPWELLING ECOSYSTEM

The Cariaco Basin (Southeastern Caribbean Sea) is the largest anoxic basin of oceanic character. Its surface waters are affected by coastal upwelling during boreal winter and spring. Historical information on the phytoplankton communities in the basin is scarce. In November 1995, an oceanographic time‐series station was established at 10.5°N ‐ 64.66°W. In this study changes in the structure of the phytoplankton community in the upper 100‐m layer were studied. Monthly samples to determine phytoplankton abundance and pigment composition (HPLC) were collected from November 1995 to January 1999; water temperature was used as proxy for upwelling. Surface waters reached temperatures ≤24° C during the upwelling season, and surpassed 26° C during the rest of the year. A total of 300 species were found. Generally, the highest number of cells (>500 cells ml−1) were measured from January to April every year. Diatoms were the dominant group in terms of abundance, species composition (168 species) and pigments (Chl c and fucoxanthin) during this period. The abundance and marker pigment concentration (peridinin, but‐ and hex‐fucoxanthin) for other groups support this observation. During the rest of the year diatom and total abundance decreased markedly (<100 cells ml−1). Small organisms (<5 μm) became dominant. The maximum concentration values of zeaxanthin and But‐ and Hex‐Fuco in this period indicated the presence of cyanobacteria and prymnesiophytes. The sparse and relatively low concentration of Chl b, lutein and prasinoxanthin indicated that chlorophytes and its allies are a minor floral component.

Biotic changes in the reef complex of San Andres Island (Southeastern Caribbean Sea, Columbia) occuring over three decades

Biotic changes in the reef complex of San Andres Island (Southeastern Caribbean Sea, Columbia) occuring over three decades

GHOST SHRIMPS OF THE GENUS LEPIDOPHTHALMUS FROM THE CARIBBEAN REGION, WITH DESCRIPTION OF L. RICHARDI, NEW SPECIES, FROM BELIZE (DECAPODA: THALASSINIDEA: CALLIANASSIDAE)

ABSTRACT Lepidophthalmus jamaicense, originally described in limited detail on the basis of two male type specimens from Montego Bay, Jamaica, is redescribed and fully illustrated in the course of our examination of the original types, a large series of recently collected male and female topotypes, and recent collections from the southeastern Caribbean Sea. Comparative morphological studies of all the known western Atlantic species serve to distinguish materials from Belize, which are herein recognized as L. richardi, new species. Included in these comparisons and descriptions are detailed studies of ventral cuticular armor in the anterior abdominal somites, an apparent apomorphic character of particular value in segregating tropical western Atlantic populations. The occurrence of L. jamaicense in southeastern Cuba is confirmed from reexamination of museum material, and the range of the species is extended to Tobago and coastal Venezuela in the extreme southeastern Caribbean. While there appears to be strong potential for regional endemism in western Atlantic species of the genus Lepidophthalmus, the widely separated insular populations of L. jamaicense in the Antillean region appear to be undifferentiated. Reproductive history and potential for larval dispersal in this species remains unknown and may not conform to the abbreviated life histories reported for its western Atlantic congeners.

Southeastern Caribbean sea level variability and viscoelastic relaxation

Viscoelastic modeling of earthquakes in the southeast Caribbean shows that distant dip‐slip earthquakes in the Lesser Antilles and the geometry of the subduction zone play a significant role in vertical deformation observed along the southern Caribbean plate margin. We find that dip‐slip earthquakes yield vertical displacements that are 1–2 orders of magnitude greater than those generated by strike‐slip earthquakes along the Caribbean‐South American plate boundary. In addition, postseismic vertical displacements are at least as great or greater at distances of several hundred kilometers than the coseismic counterpart depending upon the geometry of the source. Tide gage data from Venezuela suggest that these vertical displacement rates may still be observed several decades after the occurrence of large subduction zone earthquakes (Ms 7 or greater). In addition, the uplift rate observed at the tide gages largely follows the anticipated flexure of the Caribbean plate due to the subduction process.

A synoptic view of the levels of dispersed/dissolved petroleum hydrocarbons (DDPH) and heavy metals in the south-eastern Caribbean Sea

A synoptic view of the levels of dispersed/dissolved petroleum hydrocarbons (DDPH) and heavy metals in the south-eastern Caribbean Sea

Methane and carbon monoxide production, oxidation, and turnover times in the Caribbean Sea as influenced by the Orinoco River

The surface distribution of CH4, photoproduction capacity of seawater for CO, and CH4 and CO microbial oxidation rates and turnover times were determined for the surface waters of the southeastern Caribbean Sea and Gulf of Paria as affected by the Orinoco River. Measurements were made during the spring (low river flow) and the fall (high river flow) in order to determine the influence of Orinoco River discharge on these parameters. Methane concentrations were generally lower in the fall than in the spring. Low CH4 oxidation rates and similar surface distributions were observed during both seasons. Methane oxidation in the river plume was significantly higher in the fall. Potential CO photoproduction and CO oxidation rates were generally higher during the fall. Possible effects of the Orinoco River on potential CO photoproduction capacity were observed as far as Puerto Rico. Turnover times for CH4 were in the order of years, whereas CO turnover times were in the order of hours. The Orinoco River has a significant impact on the consumption of CO and CH4 and the photoproduction of CO in the southeastern Caribbean Sea, presumably resulting from inputs of riverine carbon and nutrients.

Reflections on the Lawfulness of Invasion

Grenada is a micro-state located in the southeastern Caribbean Sea, approximately 1600 miles from the United States. Its territory covers some 133 square miles—about twice the size of the District of Columbia—and its citizen population numbers around 110,000. Granted independence from British colonial rule in 1974, Grenada functioned under a parliamentary government until March 1979, when Maurice Bishop’s New Joint Endeavor for the Welfare, Education, and Liberation (JEWEL) Movement ousted then Prime Minister Sir Eric Gairy in a near bloodless coup. Since attaining independence, Grenada sought and secured membership in the British Commonwealth, the Organization of American States, the Caribbean Common Market and the United Nations.

Evidence of coastal Seiche excitation by tide‐generated internal solitary waves

Coastal seiches at Magueyes Island, Puerto Rico, occur in distinct fortnightly groups with maximum seiche activity following new and full moon by 7 days. The size of the fortnightly groups depends upon the amplitude of the preceding spring tide and upon the Caribbean surface water temperature. Temperature records from the upper thermocline on the slope seaward of the shelf edge off Magueyes Island indicate the arrival of semidiurnal packets of negative internal solitary waves. We suggest that these internal waves are generated by tides in the southeastern Caribbean Sea and that they are responsible for exciting the coastal seiches. This hypothesis is supported by the characteristics of coastal seiching at Puerto Princesa on Palawan Island in the Philippines which indicate excitation by the Sulu Sea internal waves reported by Apel, Holbrook and Tsai (1980).

Studies on the marine algal flora of Venezuela. VI. Cryptonemia delicatula subsp. venezuelensis subsp. nov. (Rhodophyta, Cryptonemiales)

A new subspecies of Cryptonemia delicatula Joly et Cordeiro subsp. venezuelensis Ganesan (Rhodophyta, Cryptonemiales) is described and figured from eastern Venezuela (southeastern Caribbean Sea).