Southeastern Gulf Of Mexico Research Articles

Caribboecetes progreso, a new species of sand-dwelling amphipod (Amphipoda: Corophiidea: Ischyroceridae) from the Gulf of Mexico, with a key for the genus.

A new species of the genus Caribboecetes Just, 1983 is described and illustrated from specimens collected on sandy bottoms of the northern Yucatan Peninsula, southeastern Gulf of Mexico. Caribboecetes progreso sp. nov. differs from the closely related species Caribboecetes barbadensis Just, 1983 and Caribboecetes jenikarpae Just, 1984 by the inflated triangular anterolateral flange on basis of gnathopod 2, and from Caribboecetes justi Ortiz & Lemaitre, 1997 by the setose anterolateral surface of coxal plate 7 and basis of pereopod 7. Ecological notes for the new species, a morphological comparison, map of distribution and key for all members in the genus are also provided.

Subsidence controls on foreland basin development of northwestern offshore Cuba, southeastern Gulf of Mexico

We reviewed the tectonostratigraphic evolution of the Jurassic–Cenozoic collision between the North American and the Caribbean plate using more than 30,000 km (18,641 mi) of regional two-dimensional (2-D) academic seismic lines and Deep Sea Drilling Project wells of Leg 77. The main objective is to perform one-dimensional subsidence analysis and 2-D flexural modeling to better understand how the Caribbean collision may have controlled the stratigraphic evolution of the offshore Cuba region. Five main tectonic phases previously proposed were recognized: (1) Late Triassic–Jurassic rifting between South and North America that led to the formation of the proto-Caribbean plate; this event is interpreted as half grabens controlled by fault family 1 as the east-northeast–south-southwest–striking faults; (2) Middle–Late Jurassic anticlockwise rotation of the Yucatan block and formation of the Gulf of Mexico; this event resulted in north-northwest–south-southeast–striking faults of fault family 2 controlling half-graben structures; (3) Early Cretaceous passive margin development characterized by carbonate sedimentation; sedimentation was controlled by normal subsidence and eustatic changes, and because of high eustatic seas during the Late Cretaceous, the carbonate platform drowned; (4) Late Cretaceous–Paleogene collision between the Caribbean plate, resulting in the Cuban fold and thrust belt province, the foreland basin province, and the platform margin province; the platform margin province represents the submerged paleoforebulge, which was formed as a flexural response to the tectonic load of the Great Arc of the Caribbean during initial Late Cretaceous–Paleocene collision and foreland basin development that was subsequently submerged during the Eocene to the present water depths as the arc tectonic load reached the maximum collision; and (5) Late Cenozoic large deep-sea erosional features and constructional sediment drifts related to the formation of the Oligocene–Holocene Loop Current–Gulf Stream that flows from the northern Caribbean into the Straits of Florida and to the north Atlantic.

Presence of longfin mako shark Isurus paucus (Chondrichthyes: Lamnidae) in the south-eastern Gulf of Mexico, Tabasco, Mexico

A male longfin mako shark Isurus paucus of 303 cm total length was found during the monitoring of small scale fishery in Nuevo Torno Largo, Tabasco. This is the first record of the species in the south-eastern Gulf of Mexico. The specimen was caught by a small longline vessel at 18 o 49′45″N 94 o 08′14″W. Snout and ventral coloration, pectoral fin length and dorsal fin position were used to verify the identification.

Morphological variation of Thalassia testudinum in two shallow coastal environments from the southeastern Gulf of Mexico

Total biomass, shoot density, leaf length and leaf width of the dominant seagrass Thalassia testudinum were compared between two coastal environments in the northeastern part of the Yucatan peninsula (Mexico). The coastal environments were (a) an exposed sublittoral zone (<1 km from the shoreline) and (b) a sheltered coastal lagoon. Plant morphology was monitored at monthly intervals from June 2001 to May 2002. There was a clear morphological variation between coastal environments throughout the period of study. In the exposed sublittoral zone, total biomass and shoot density were lower and leaves were longer and wider. In contrast, in the sheltered lagoon, total biomass and shoot density were higher and the leaves shorter and narrower. Overall, high values of total biomass, shoot density and leaf width were observed during the warm weather seasons (rainy and dry) whereas the low values were observed during the cold fronts weather season (nortes); leaf length followed a reverse trend. Results presented here stress the need to take into account the natural pattern of morphological variation in the design of sampling and monitoring programs.

Tithonian–Early Valanginian evolution of deposition along the proto-Caribbean margin of North America recorded in Guaniguanico successions (western Cuba)

In the Guaniguanico Mountains of western Cuba, the Late Jurassic–Early Cretaceous limestones occur in three stratigraphic successions, which have accumulated along the proto-Caribbean margin of North America. The Late Jurassic subsidence and shallow-water carbonate deposition of the Guaniguanico successions have no counterpart on the northeastern Maya block, but some distant similarities with the southeastern Gulf of Mexico may exist. Four facies types have been distinguished in the Tithonian–Lower Valanginian deposits of the Guaniguanico tectonic units. Drowning of the Late Jurassic carbonate bank of the Sierra de los Organos occurred at the Kimmeridgian/Tithonian boundary. During this boundary interval, sedimentation in the west Cuban area and southwestern margin of the Maya block (Mexico) has evolved in a similar way in response to a major second-order transgression. The Lower Tithonian ammonite assemblages of the Guaniguanico successions indicate, in general, the neritic zone. Presence of juvenile gastropods and lack of adult specimens suggest unfavorable environment for these molluscs, probably related to low oxygenation levels. The Early Tithonian transgressive phase terminated about the lower boundary of the Chitinoidella Zone. The Late Tithonian “regressive” phase is weakly marked, whereas the latest Tithonian–earliest Berriasian strata were deposited during a deepening phase. The latter transgressive phase has ended in the Late Berriasian Oblonga Subzone. We correlate the bioturbated pelagic biomicrites of the Tumbitas Member of the Guasasa Formation with a significant fall of the sea level during the latest Berriasian–Early Valanginian. The average sedimentation rate for the Tumbitas Member biomicrites was about three times faster than for the Berriasian Tumbadero Member limestones. Sedimentation rates for the Tumbitas Member and the Valanginian limestones at the DSDP Site 535 in the southeastern Gulf of Mexico were similar. In the Los Organos succession, the Late Valanginian transgressive interval is associated with radiolarian limestones and black chert interbeds in the lower part of the Pons Formation. In the Southern Rosario succession, the pelagic limestones pass into the radiolarian cherts of the Santa Teresa Formation indicating a proximity of CCD during Late Valanginian–Hauterivian times.

Bacterial Diversity of Marine Seeps in the Southeastern Gulf of Mexico

The diversity of bacterial communities of shallow (< or = 100 m depth) oil seep marine sediments from the southern Gulf of Mexico was evaluated. The geochemical properties of seep sediments were characterized as well as their microbial diversity in oil seep and control sediments. Bacteria were identified through molecular tools as belonging to the genera Marinobacter, Idiomarina, Marinobacterium, Frauteria and an unknown bacterium. Bacteria might be important components of microbial communities in Total Petroleum Hydrocarbon (TPH)-containing environments, displaying either facultative metabolism or able to grow only in petroleum-containing media. The identification of bacteria in shallow oil seep sediments could be used as indicators of marine hydrocarbons in southeastern Gulf of Mexico.

Multiple cues from multiple habitats: Effect on metamorphosis of the Florida stone crab, Menippe mercenaria

The Florida stone crab, Menippe mercenaria, is an economically and ecologically important species that ranges from North Carolina throughout the Caribbean and the southeastern Gulf of Mexico. However, there is little known about its early life history stages as compared to other commercially important species in the region. The goal of this research was to examine effects of putative cues on metamorphosis from the megalopa stage to the first juvenile stage. Our study investigated the effect of water-soluble exudates from four substrata, as well as natural biofilms, and exudates from adult stone crabs. In addition, the influence of natural substrata was compared to that of artificial substrata. Adult exudate had no significant effect on metamorphosis, despite a wide range of tested concentrations. In contrast, there was a significant effect on mean time to metamorphosis in experimental groups exposed to multiple cues associated with the brown alga Sargassum fluitans, rubble from stone crab habitat, the eastern oyster Crassostrea virginica, and biofilms associated with the oyster. Furthermore, we provide evidence for metamorphic responses to water-soluble chemical cues, as well as biochemical and physical cues associated with different substrata. Overall results were coherent with the relevant body of previous work on metamorphosis of brachyuran crab larvae and indicate that both physical and chemical cues are important factors in facilitating the settlement and metamorphosis of M. mercenaria larvae in juvenile nursery habitat.

A filterable lytic agent obtained from a red tide bloom that caused lysis of Karenia brevis (Gymnodinum breve) cultures

A filterable lytic agent (FLA) was obtained from seawater in the southeastern Gulf of Mexico during a red tide bloom that caused lysis of Karenia brevis (formerly Gymnodinium breve) Piney Island. This agent was obtained from < 0.2 µm filtrates that were concentrated by ultrafiltration using a 100 kDa filter. The FLA was propagated by passage on K. brevis cultures, and the filtered supernatants of such cultures resulted in K. brevis lysis when added to such cultures. The lytic activ- ity was lost upon heating to 65°C or by 0.02 µm filtration. Epifluorescence and transmission electron microscopy (TEM) of supernatants of K. brevis cultures treated with the lytic agent indicated a high abundance of viral particles (4 × 10 9 to 7 × 10 9 virus-like particles (VLPs) ml -1 ) compared to control cultures (~10 7 ml -1 ). However, viral particles were seldom found in TEM photomicrograph thin sec- tions of lysing K. brevis cells. Although a virus specific for K. brevis may have been the FLA, other explanations such as filterable bacteria or bacteriophages specific for bacteria associated with the K. brevis cultures cannot be discounted.

ABSTRACT: Seismic Stratigraphy Analysis of the South-Eastern Gulf of Mexico (NW Offshore Cuba) - Regional Mesozoic Tectono-Stratigraphy and Platform Evolution

ABSTRACT: Seismic Stratigraphy Analysis of the South-Eastern Gulf of Mexico (NW Offshore Cuba) - Regional Mesozoic Tectono-Stratigraphy and Platform Evolution

NORMJONESIA DANIELI, A NEW GENUS AND SPECIES OF NANNASTACID CUMACEAN (MALACOSTRACA: PERACARIDA) FROM THE SOUTHWEST FLORIDA CONTINENTAL SHELF

Abstract The nannastacid cumacean, Normjonesia danieli, n. g., n. sp., is described from a depth of 88 m on the Southwest Florida shelf in the southeastern Gulf of Mexico. The new genus appears to have its closest affinities with Campylaspis Sars and Cubanocuma Bacescu and Muradian, also known from the shallow waters of the Caribbean Sea. A combination of characters, including: (1) the apparent lack of terminal aesthetes on antenna 1; (2) the absence of exopods on the female; (3) the presence of 5 pairs of exopods on the male; and (4) the presence of long terminal setae on the third maxilliped, distinguishes Normjonesia from the other known genera of the family Nannastacidae.

Normjonesia Danieli, a New Genus and Species of Nannastacid Cumacean (Malacostraca: Peracarida) from the Southwest Florida Continental Shelf

The nannastacid cumacean, Normjonesia danieli, n. g., n. sp., is described from a depth of 88 m on the Southwest Florida shelf in the southeastern Gulf of Mexico. The new genus appears to have its closest affinities with Campylaspis Sars and Cubanocuma Băcescu and Muradian, also known from the shallow waters of the Caribbean Sea. A combination of characters, including: (1) the apparent lack of terminal aesthetes on antenna 1; (2) the absence of exopods on the female; (3) the presence of 5 pairs of exopods on the male; and (4) the presence of long terminal setae on the third maxilliped, distinguishes Normjonesia from the other known genera of the family Nannastacidae.

Micro- and macrodiversity in rbcL sequences in ambient phytoplankton populations from the southeastern Gulf of Mexico

Ribulose-1,5-diphosphate carboxylase/oxygenase (RuBisCO) large subunit genes (rbcL) were obtained by amplification and cloning of 554 or 614 bp sequences of indigenous phytoplankton populations at 2 stations in the southeastern Gulf of Mexico. One station (Stn 4) was located in a low salinity, high chlorophyll plume (the 'Green River') which has previously been shown to contain elevated levels of Form IA rbcL mRNA while the other (Stn 7) was in oligotrophic, oceanic water. A diversity of rbcL sequences was obtained, spanning 3 of the 4 evolutionary clades of Form I RuBisCOs. Six nucleotide sequences obtained from Stn 4 were closely related (92 to 96% similar) to the Form IA-containing Prochlorococcus GP2. Flow cytometry and pigment analysis indicated that Prochlorococcus was abundant at this site. Other sequences found included a Form IB rbcL closely related to prasinophytes, and Form ID sequences related to prymnesiophytes, diatoms, and pelagophytes. One sequences was nearly identical to the pelagophyte, Pelagomonas calceolata. At Stn 7, sequences were obtained that were more deeply rooted, and less similar to rbcLs in existing databases (77 to 83% similar), and no Form IA rbcLs were detected. HPLC pigment signatures and flow cytometry data were consistent with the forms obtained by cloning. The similarity of the 6 Prochlorococcus GP2-like sequences (93 to 98%) is consistent with the phenomenon of molecular microdiversity as found at other loci in marine (and other environmental) microorganisms.

Seabirds of the Campeche Bank Islands, Southeastern Gulf of Mexico

Seabirds of the Campeche Bank Islands, Southeastern Gulf of Mexico

Demography of the bonnethead shark, Sphyrna tiburo (Linnaeus, 1758), in the southeastern Gulf of Mexico

The bonnethead shark, Sphyrna tiburo, is one of the most abundant species in catches from the Gulf of Mexico, particularly from Campeche. It is mainly caught with gill nets and it is available throughout the year. A demographic analysis was carried out, incorporating the best available information about its life history, such as age at first maturity, fecundity, longevity, sex ratio (1:1) and age-specific natural mortality. The age and growth data used come from northern individuals of the Gulf of Mexico. The first run was done to obtain the demographic parameters under natural conditions. Other simulations varying age at first capture and incorporating fishing mortality were made to estimate the rate of change of the net reproductive rate (R0), generation time, intrinsic rate of increase and doubling time. Using an age-structured dynamic model, R0 was projected until the year 2010. The results of the simulations showed that S. tiburo has a higher reproductive potential than other sharks. This analysis will allow us to establish the management strategies for the fishery.

Cenozoic tectonic history of the North America‐Caribbean plate boundary zone in western Cuba

Structural studies of well‐dated Jurassic to lower Miocene rocks in western Cuba constrain the sequence of structural events affecting this oblique collisional zone between the late Cretaceous island arc and the Jurassic‐Cretaceous North America passive margin in the southeastern Gulf of Mexico and Straits of Florida. Results of detailed mapping and collection of fault slip data at 34 sites define a regionally consistent, five phase tectonic model for the period from the late Paleocene to the post‐early Miocene. During the late Paleocene to the early Eocene, the Cuban island arc collided with the North American passive margin (Bahamas Platform). Northwest‐ward overthrusting during the collision defines tectonic phase I. A NNE‐SSW compression concurrent with early Eocene left‐lateral strike‐slip faulting along the Pinar fault zone defines phase II. This result is consistent with structural mapping showing sinistral shear within the 065° striking Pinar fault zone. An ENE‐WSW to E‐W compression defining phase III overprinted phase II faults in the lower Eocene and older rocks. Post‐early Miocene normal faulting characterizes phase IV. Inversion of fault slip data indicates two contemporaneous directions of tension of 120 and 170. Strike‐slip faults that overprint phase IV normal faults yield a 120 compression (phase V). The direction of compression associated with the arc/continent collision rotates clockwise from NW‐SE in the late Paleocene/early Eocene (phase I), to NNE‐SSW (phase II) and to ENE‐WSW by the middle Eocene (phase III). The rotation in the compression direction occurred because the arc turned toward an oceanic area in the present‐day area of central and eastern Cuba. Progressive collision led to complete subduction of the remnant oceanic crust by middle to late Eocene time.

A Late Jurassic Rift, Southeastern Gulf of Mexico: ABSTRACT

A Late Jurassic Rift, Southeastern Gulf of Mexico: ABSTRACT

Suspended sediments in the southeastern Gulf of Mexico

Suspended sediment concentration was determined from samples collected during oceanographic cruises dinamo I and dinamo II, aboard the R/V Justo Sierra in the southeastern Gulf of Mexico, during dry and north wind climatic periods in 1990. The average suspended matter concentration was 5.1 mg/l for the dry period and 5.5 mg/l for the period with a northern wind. The maximun value was 25.2 mg/l on dinamo II cruise and was obtained off the Grijalva and Usumacinta rivers, as well as the maximun observed during dinamo I. The suspended sediment is composed mainly of silt and clay particles toward the terrigenous zone and silicious organic debris and tar balls toward the offshore carbonate region. The relative abundance of elements in samples from the terrigenous and transitional zones reflects the influence of fluvial fine sediments by cationic elements of argillaceous origin. Sigma- t distribution patterns show the presence of a current coming from the north of Yucatan Peninsula, which penetrates in the study area parallel to the isopycnals. CTD data, satellite images, Ca/Al distributions and suspended sediments distributions suggest that off the Grijalva-Usumacinta mouth the direction of the current is eastward. Lower concentrations of total suspended matter are located seaward Terminos Lagoon and are apparently associated to a cyclonic circulation zone.

Ribulose bisphosphate carboxylase gene expression in subtropical marine phytoplankton populations

Oceanic phytoplankton are known to fix CO2 primarily through the action of the enzyme ribulose-1,5-bisphosphate carboxylase (RuBPCase). The amino acid and nucleotide sequence of the large subunit of this enzyme have been conserved across the evolution of the chlorophytic plants (from cyanobacteria to higher plants via green algae) with approximately 80 and 70 % homology at the amino acid and nucleotide levels respectively. To understand the molecular regulation of this enzyme in phytoplankton, we have measured levels of the RuBPCase large subunit (rbcL) mRNA and DNA, in combination with rates of photosynthetic CO2 fixation, autofluorescent cell counts, and chlorophyll a in natural phytoplankton communities of Tampa Bay (Flonda, USA) and the southeastern Gulf of Mexico. We measured rbcL mRNA, rbcL DNA, and the ratio of rbcL mRNA to rbcL DNA by extracting RNA and DNA and probing the extracts with the Synechococcus PCC 6301 rbcL gene as a probe. Additionally, rbcL mRNA was amplified from certain samples using a reverse transcriptase-linked polymerase chain reaction procedure. In a transect from Tampa Bay seaward, levels of rbcL mRNA decreased 3to 8-fold from the estuarine environment to the offshore environment, and followed similar trends as photosynthetic CO2 fixation, picocyanobacterial counts, and chlorophyll a. In an offshore vertical profile, the subsurface maximum in the rbcL mRNA/DNA ratio coincided with the 60 m maximum in photosynthetic assimilation rates. In a die1 study using 150 1 of offshore water in a deck-top incubator, the rbcL mRNA.DNA ratio was nearly an order of magnitude greater (76 ng mRNA ng-' DNA) during the light period than in the dark (17 ng mRNA ng-' DNA). Likewise, the photosynthetic rate (PB) at constant illun~ination was highest during daylight hours (6.2 pg C pg-' chl a h-') and lowest at night (1.9 pg C pg-' chl a h-'). These results indicate that (1) carbon fixation in oceanic phytoplankton may be transcriptionally regulated at the level of the RuBPCase gene and (2) that the quantitatlon of particular target mRNAs and DNAs is an effective means to study the regulation of conserved gene functions in natural water column microbial populations.

Concentration of viruses and dissolved DNA from aquatic environments by vortex flow filtration

Vortex flow filtration (VFF) was used to concentrate viruses and dissolved DNA from freshwater and seawater samples taken in Florida, the Gulf of Mexico, and the Bahamas Bank. Recoveries of T2 phage and calf thymus DNA added to artificial seawater and concentrated by VFF were 72.8 and 80%, respectively. Virus concentrations determined by transmission electron microscopy of VFF-concentrated samples ranged from 3.4 x 10(7)/ml for a eutrophic Tampa Bay sample to 2.4 x 10(5) for an oligotrophic oceanic surface sample from the southeastern Gulf of Mexico. Viruslike particles were also observed in a sample taken from a depth of 1,500 m in the subtropical North Atlantic Ocean. Filtration of samples through Nuclepore or Durapore filters (pore size, 0.2 micron) prior to VFF reduced phage counts by an average of two-thirds. Measurement of dissolved-DNA content by Hoechst 33258 fluorescence in environmental samples concentrated by VFF yielded values only ca. 35% of those obtained for samples concentrated by ethanol precipitation (the standard dissolved-DNA method). However, ethanol precipitation of VFF-concentrated extracts resulted in an increase in measurable DNA, reaching 80% of the value obtained by the standard method. These results indicate that a portion of the naturally occurring dissolved DNA is in a form inaccessible to nucleases and Hoechst stain, perhaps bound to protein or other polymeric material, and is released upon ethanol precipitation. Viral DNA contents estimated from viral counts averaged only 3.7% (range, 0.9 to 12.3%) of the total dissolved DNA for samples from freshwater, estuarine, and offshore oligotrophic environments.(ABSTRACT TRUNCATED AT 250 WORDS)

Enumeration and sizing of aquatic bacteria by use of a silicon-intensified target camera linked-image analysis system

Modern image analysis systems incoroporating video cameras and epifluorescence microscopy provide accurate cell counts and size measurements of natural populations of aquatic bacteria. This paper presents comparisons of counts and size measurements made manually and with an Image Technology Corporation Model 2000 image analysis system of bacteria from diverse aquatic environments of southwestern Florida, including the Alafia and Crystal Rivers, Tampa Bay, and the southeastern Gulf of Mexico. The modification of automated counting and sizing software and addition of a silicon-intensified target camera to the image-analysis system enabled collection of data statistically equivalent to manually derived data in all cases. Bacterial cells from 0.18 > 7.00 μm were measured at cell densities up to 1.14 × 10 7 cells·ml −1. Estimation of biomass based upon published values of g C·μm −3 and image analysis-derived cell abundances and volumes ranged between 2.79 × 10 −8 g C·ml −1 for the oligotrophic Crystal River and 1.27 × 10 −6g C·ml −1 for the eutrophic Alafia River.