Western Central Atlantic Research Articles

First record of darter goby, Ctenogobius boleosoma (Jordan & Gilbert, 1882) (Gobiiformes: Gobiidae), in the Mediterranean with notes on larval morphology and cryptic diversity

Darter goby, Ctenogobius boleosoma (Jordan & Gilbert, 1882), is a small euryhaline fish of the Gobiidae family (Gobiiformes). It is naturally found in the shallow marine and brackish waters of the Western Central Atlantic. This study reports the first record of C. boleosoma in the Mediterranean Sea. In August and October 2019, two postflexion stage larvae were sampled during ichthyoplankton surveys in Antalya Bay in the Northeastern Mediterranean. The larvae were identified using the barcoding of cytochrome oxidase 1 gene sequence of mitochondrial DNA (COI). The morphology of the pre-transitional stage larvae was described and compared to previously published data. A phylogenetic analysis revealed that two distinct clades of C. boleosoma exist in its distribution range. The COI records belonging to one of the clades were generally collected within the Caribbean Sea, while the others were collected primarily in North American Western Atlantic waters from Florida to North Carolina. The average divergence between the clades was calculated to be 9.36 ± 1.34 (± 95% confidence interval), which likely indicates the existence of undescribed species. The specimen from the Mediterranean was identified as most closely related to the North American clade. This study shows how the integrative taxonomy of ichthyoplankton can improve knowledge about non-indigenous fish in the Mediterranean.

Ecological niche modeling reveals manta ray distribution and conservation priority areas in the Western Central Atlantic

AbstractThe Western Central Atlantic (WCA) hosts a population of manta rays whose distribution and habitat preference is poorly understood. Addressing this lack of knowledge will be essential to aid the effective implementation of targeted conservation measures. Here, we use ensemble ecological niche modeling to predict the monthly distribution of manta rays in the WCA using multiple sources of species occurrence data, and consequently identify core areas, which represent suitable habitat in all months of the year. Models suggest a seasonal cycle of expansion and contraction of suitable habitat from coastal areas in spring‐summer, to open ocean in autumn‐winter. Core areas are concentrated along the coast of the USA, Mexico, and Venezuela. Only 24% of predicted suitable habitat is encompassed by the present regional network of MPAs, and is intersected by numerous, heavily trafficked shipping lanes. Manta rays are slow‐growing animals that only produce a limited number of offspring; as such, this species is sensitive to even moderate increases in mortality rates. For this reason, the existing regional network of MPAs may offer them limited protection. As manta rays in the WCA are challenged by a complex landscape of threats and protective measures, future marine conservation planning in the region should explicitly address the conservation of manta rays, focusing on areas identified as key habitats for the species.

Octopus americanus: a cryptic species of the O. vulgaris species complex redescribed from the Caribbean

The common octopus Octopus vulgaris Cuvier, 1797, once considered a cosmopolitan species, is a species complex composed by six species: O. tetricus, O. cf tetricus and O. sinensis in the Pacific; type I and II, in the West Atlantic; and type III in the Indian Ocean around South Africa. The tropical western central Atlantic is an important octopus fishing ground targeting O. maya, O. insularis, and a cryptic species considered to be O. vulgaris type I. In order to clarify the identification of this octopod, phylogenetic analyses were carried out with mitochondrial (COI and 16S) and nuclear (rhodopsin) genes, together with morphological analyses of 16 specimens caught in the northeastern continental shelf of Yucatan (Mexico). The main morphological traits differing from O. vulgaris were the presence, position and size of enlarged suckers and hectocotylus sucker number in males. Genetic distances and haplotype networks of the species complex were estimated using 285 COI sequences of nine Octopus species from 14 different locations around the world. The octopod sequences from Yucatan clustered within a monophyletic group that included sequences of O. vulgaris type II for the three genes analyzed. Phylogenetic distances with other members of the complex ranged between 2.71 and 3.89% using COI data. These genetic results support the presence of Octopus americanus Monfort, 1802 (formerly known as O. vulgaris type II) along the Yucatan continental shelf, a new octopod extending from the north of Argentina to the northwest coast of the USA.

First record of the ragged-tooth shark, Odontaspis ferox (Risso, 1810), in the Venezuelan Caribbean

One specimen of the ragged-tooth shark, Odontaspis ferox, was caught by a commercial shark fishery to the north of Cape Codera (10° 56′ N, 66° 02′ W), northeastern Venezuela. The specimen (sex unidentified, ~ 180 cm TL, ~ 30 kg) was identified on the basis of its dry jaw and characteristic dentition: which comprise teeth moderately large, with prominent narrow cusps and two or three pairs of lateral cusplets. This is the first record of O. ferox in the Venezuelan Caribbean, and this finding complements the knowledge of geographic distribution of this rare species in the Western Central Atlantic.

Dissolved cadmium and its relation to phosphate in the deep region of the Gulf of Mexico

Abstract We evaluated the factors that control the variability in dissolved cadmium (Cdd), phosphate (PO43−) and the Cdd/PO43− ratio in the upper 1000 m of the deep region of the Gulf of Mexico (GoM), a marginal sea where trace element data are limited. These variables were compared to data from studies of adjacent areas (in the Western Central Atlantic), related to physical processes (mesoscale structures and upwelling events) occurring inside the GoM, and to dinoflagellate and diatom abundances in surface waters of this region. Vertical distributions of Cdd concentrations and the Cdd/PO43− ratio displayed the typical nutrient profile that has been extensively reported for different oceans. Cdd and PO43− concentrations in the GoM were higher than those in the Western Central Atlantic. The slope of the Cdd vs. PO43− relationship for samples within the Loop Current (LC) in the GoM was similar (242 pmol μmol−1, R2 = 0.96) to that calculated for the Western Central Atlantic waters (same depth range) that reach the GoM through the LC (235 pmol μmol−1, R2 = 0.98). The linear regression for all the GoM samples, though having a similar slope (249 pmol μmol−1), presented a larger deviation (R2 = 0.91). We propose that this deviation is due to spatial inhomogeneity that can be explained by 1) preferential remineralization of PO43− vs. Cdd at subsurface waters in some regions, 2) Cdd inputs from the north, transported by mesoscale processes, and 3) interactions with the continental slope at the minimum O2 layer. Local changes in the relationship between Cdd and PO43− were traced with Cd*, which represents the deviation of measured Cd to that expected by the deep-water Cdd vs. PO43− relationship. Cd* presented mainly negative values at surface and subsurface waters (~150 m) indicating preferential uptake of Cdd vs. PO43− by the phytoplankton at the surface and preferential remineralization of PO43− vs. Cdd from the organic matter at the subsurface waters. At deeper waters (~400–1000 m) Cdd was preferentially remineralized. In order to understand the inhomogeneity of the horizontal distribution of Cdd, PO43− and the Cdd/PO43− ratio in surface waters, three regions were defined considering their biological and physical characteristics. These were: I) the Oligotrophic region (in the northwest GoM) where the variability in the Cdd/PO43− ratio was largely explained by salinity, II) the Upwelling region (off the coast of the Yucatan Peninsula) where the variability in the Cdd/PO43− ratio was principally due to the diatom abundance and, III) Semi-permanent Cyclonic Gyre region (Bay of Campeche) where the variability in Cdd and the Cdd/PO43− ratio were primarily influenced by the upwelling generated by the cyclonic gyre, and the variability in PO43− was likely due to the consumption of this nutrient by phytoplankton. In summary, physical processes, river inputs, and phytoplankton abundance appear to play an important role in explaining the spatial variation in the Cdd/PO43− ratio.

Shark and ray diversity in the Tropical America (Neotropics)-an examination of environmental and historical factors affecting diversity.

We present the first comprehensive review of the present and past shark and ray diversity in marine waters of Tropical America, examining the patterns of distribution in the Eastern Central Pacific (EP) and Western Central Atlantic (WA) realms. We identified the major regions of diversity and of endemism, and explored the relations to physical variables. We found a strong relationship between shark and ray diversity with area and coastal length of each province. The Tropical Northwestern Atlantic Province is characterized by high diversity and greater occurrence of endemic species, suggesting this province as the hotspot of sharks and rays in Tropical America. The historical background for the current biogeography is explored and analyzed. Referential data from 67 geological units in 17 countries, from both shallow and deep-water habitats, across five time-clusters from the Miocene to the Pleistocene were studied. New data include 20 new assemblages from six countries. The most diverse Neogene and extant groups of shark and ray are Carcharhiniformes and Myliobatiformes, respectively. The differentiation between Pacific and Atlantic faunas goes to at least the middle Miocene, probably related with the increasing closure of the Central American Seaway acting as a barrier. The highest faunal similarity between the assemblages from the EP and the WA at the early Miocene could be related to the lack of a barrier back then, but increased sampling is needed to substantiate this hypothesis.

A re-evaluation of the basal age in the DSDP hole at Site 534, Central Atlantic

For 30 years, the initial sedimentation following the opening of the western Central Atlantic has been considered to be of Middle Callovian age (approximately 164.5 Ma) based on the biochronostratigraphical estimation for the basal sedimentary unit of the borehole from Site 534A of the Deep Sea Drilling Program (DSDP). That age has been used in kinematic models of the opening of the Central Atlantic. A reconsideration of the available biochronostratigraphical data and correlation of the δ¹³Ccarb record from Site 534A with those from the Tethyan and North Atlantic records suggest that the initial sedimentation at Site 534A is, in fact, of Middle Oxfordian age (approximately 160.6 Ma). The high biostratigraphic similarity among the basal sedimentary units of the boreholes at DSDP Site 534A and Ocean Drilling Program Site 801C in the Western Pacific suggest the same age for both sites. The Middle Oxfordian δ¹³Ccarb records from the different sites covary, marking the same palaeoenvironmental changes, although such an agreement was not previously acknowledged. A combination with additional data proposes that Middle Oxfordian age corresponds to the precise date of the opening of the Hispanic Corridor between the Atlantic and Pacific oceans.

First report of the whitesaddled catshark Scyliorhinus hesperius (Springer 1966) in Guatemala’s Caribbean Sea

Abstract Background The present study represents the first record of Scyliorhinus hesperius in Guatemala’s Caribbean Sea. Methods Five male whitesaddled catsharks, S. hesperius , were captured in 200 m deep waters of Guatemala’s Caribbean coast. Results and Conclusion All specimens were male with total lengths ranging from 420 mm to 510 mm. These fish represent the first record of mature male S. hesperius , the first record for this species in Guatemalan territorial waters, and a range extension in the Western Central Atlantic.

Variación fenotípica de la langosta espinosa Panulirus argus (Decapoda: Paniluridae) en el Caribe Suroccidental

The spiny lobster Panulirus argus is an important fishery species in the Western Central Atlantic. Changes in the dispersion range through its life cycle and heterogeneous habitats, suggest that P. argus exhibit phenotypic plasticity. However, the morphometric variation of this species is unknown so far, although this information is relevant in evolutionary studies as well as to solve questions of fishery interest. Thus, the aim of this study was to determine whether P. argus exhibit phenotypic variation between sexes, among five geographic origins and three oceanographic conditions of Southwest Caribbean (Colombian archipelago San Andrés, Providencia y Santa Catalina). A total of 193 P. argus adults were submitted to geometric morphometrics using six landmarks that delimit one half of the sternal plate. The differences in sternal plate size were compared with Kruskal-Wallis and Mann-Whitney Tests. The allometric effect was estimated using Multivariate Regression Analysis, the model of allometric slopes was tested by Multivariate analysis of covariance and the sternal plate shape differences was explored using non-parametric comparisons of Euclidian distances and Neighbour Joinnig trees. The results showed that the morphometric variation of sternal plate of this spiny lobster varied according to the gender since the sexual size and shape dimorphisms were significant. In both sexes, the sternal plate shape differed among oceanographic scenarios as it was evidenced by significant differences among Euclidian distances, and the tendency to cluster by North, Centre and South sections of San Andrés archipelago. Additionally, the morphometric variation resulting from phenotypic plasticity to variable ecological contexts may explain the phenotypic differences among genetically similar populations. This information permits to define management units, support the selection of regulatory policies of this fishery and complement the genetic analysis of the species in this Caribbean region.

Mitochondrial DNA Variation Reveals a Sharp Genetic Break within the Distribution of the Blue Land Crab Cardisoma guanhumi in the Western Central Atlantic.

The blue land crab Cardisoma guanhumi is widely distributed throughout tropical and subtropical estuarine regions in the Western Central Atlantic (WCA). Patterns of population genetic structure and historical demographics of the species were assessed by mtDNA control region sequence analysis to examine the connectivity among five populations (n = 97) within the region for future conservation strategies and decision-making of fishery management. A total of 234 polymorphic nucleotides were revealed within the sequence region, which have defined 93 distinct haplotypes. No dominant mtDNA haplotypes were found but instead a distribution of a few low-frequency recurrent haplotypes with a large number of singletons. A NJ-tree and a median-joining haplotype network revealed two distinct clusters, corresponding to individuals from estuaries located along the Caribbean Sea and Brazilian waters, respectively. AMOVA and FST statistics supported the hypothesis that two main geographic regions exists. Phylogeographical discontinuity was further demonstrated by the Bayesian assignment analysis and a significant pattern of isolation-by-distance. Additionally, tests of neutral evolution and analysis of mismatch distribution indicate a complex demographic history in the WCA, which corresponds to bottleneck and subsequent population growth. Overall, a sharp genetic break between Caribbean and Brazilian populations raised concerns over the conservation status of the blue land crab.

A new deep-sea species of Barathronus Goode & Bean from Brazil, with notes on Barathronus bicolor Goode & Bean (Ophidiiformes: Aphyonidae)

A new species of Barathronus (Ophidiiformes: Aphyonidae) is described from a single, mature male specimen (101 mm SL) bottom trawled on the continental slope of Rio Grande do Norte, northeastern Brazil, between 1,964 and 2,045 m depth. The new species is diagnosed among congeners by the following combination of characters: peritoneum transparent, deep-set eyes not visible, eight fangs on vomer, anal fin rays 69, predorsal length 42.0% SL, preanal length 49.5% SL, penis long, slender, and lacking a pair of lobes at its base, and presence of a ventral flexure of the anterior 2-3 vertebrae. Additionally, morphological data of three specimens of Barathronus bicolor collected in Brazilian waters are presented and compared with those from 51 specimens from the western Central Atlantic.

Octopus lipid and vitamin E composition: interspecies, interorigin, and nutritional variability.

Octopus vulgaris, Octopus maya, and Eledone cirrhosa from distinct marine environments [Northeast Atlantic (NEA), Northwest Atlantic (NWA), Eastern Central Atlantic, Western Central Atlantic (WCA), Pacific Ocean, and Mediterranean Sea] were characterized regarding their lipid and vitamin E composition. These species are those commercially more relevant worldwide. Significant interspecies and interorigin differences were observed. Unsaturated fatty acids account for more than 65% of total fatty acids, mostly ω-3 PUFA due to docosahexaenoic (18.4-29.3%) and eicosapentanoic acid (11.4-23.9%) contributions. The highest ω-3 PUFA amounts and ω-3/ω-6 ratios were quantified in the heaviest specimens, O. vulgaris from NWA, with high market price, and simultaneously in the lowest graded samples, E. cirrhosa from NEA, of reduced dimensions. Although having the highest cholesterol contents, E. cirrhosa from NEA and O. maya from WCA have also higher protective fatty acid indexes. Chemometric discrimination allowed clustering the selected species and several origins based on lipid and vitamin E profiles.

Predicting the vertical distributions of reef fish larvae in the Straits of Florida from environmental factors

Three seasons of vertically stratified ichthyoplankton sampling at the edge of the Florida Current revealed consistent accumulations of some coral reef fish larvae under taxon-specific environmental conditions. Environmental variability ranging from predictable (seasonal differences in temperature, diel changes in light, and vertical gradients in many variables) to stochastic (changes in wind-driven turbulence and patchiness of zooplankton) was used to model larval distributions. In five taxa, including the commercially important Epinephelini (groupers), relative larval densities were predicted with significant accuracy based entirely on sampling depth. Models yielding these predictions were cross-validated among all seasons, indicating that larval vertical distributions were remarkably unaffected by other environmental factors, while revealing strong behavioral preferences for specific ranges of hydrostatic pressure. Pomacentridae (damselfish) larvae consistently occupied shallower depths at night than during the day, demonstrating diel vertical migrations. At the community level, depth and season were two major factors structuring larval coral reef fish assemblages. Predictable vertical distributions of larvae in the Straits of Florida can facilitate modeling the same taxa elsewhere in the Western Central Atlantic.

The Living Marine Resources of the Western Central Atlantic. Volume 1: Introduction, molluscs, crustaceans, hagfishes, sharks, batoid fishes, and chimaeras. Volume 2: Bony fishes part 1 (Acipenseridae to Grammatidae). Volume 3: Bony fishes part 2 (Opistognathidae to Molidae), sea turtles and marine mammals. FAO Species Identification Guide for Fishery Purposes and American Society of Ichthyologists and Herpetologists Special Publication No.

The Living Marine Resources of the Western Central Atlantic. Volume 1: Introduction, molluscs, crustaceans, hagfishes, sharks, batoid fishes, and chimaeras. Volume 2: Bony fishes part 1 (Acipenseridae to Grammatidae). Volume 3: Bony fishes part 2 (Opistognathidae to Molidae), sea turtles and marine mammals. <i>FAO Species Identification Guide for Fishery Purposes</i> and <i>American Society of Ichthyologists and Herpetologists Special Publication</i> No.

The Biology of Wahoo (Acanthocybium solandri) in the Western Central Atlantic

This contribution summarizes aspects of the biology of the wahoo, Acanthocybium solandri (Scombridae), that are pertinent to assessment and management of this species in the western central Atlantic (WCA). In this region wahoo is a target species for both commercial and recreational fisheries, and annual landings appear to have increased steadily over the last 30 years to in excess of 2000 mt. Wahoo is believed to be migratory, but little is known of the migration patterns. Significant seasonal variation in catches within the region indicates that it is seasonally abundant in most locations. Periods of peak abundance occur from the fall through spring in the southeastern and northern Caribbean islands, and are restricted to the warmer months (late spring through early fall) in the more northerly locations (northern Gulf of Mexico, North Carolina, and Bermuda). Wahoo exhibits early sexual maturity (within the first year) and a spawning season that extends from at least May to October. Females are multiple batch spawners and are highly fecund. Limited age and growth studies indicate that it is a relatively fast-growing species, has high mortality, and probably lives for 5-6 years. Wahoo is primarily piscivorous, although some invertebrates including squids are eaten. A relatively small number of parasite species have been associated with it. There is no evidence of more than a single shared stock of wahoo in the WCA, and recent genetic studies, using RAPD markers, suggest that stock boundaries may extend beyond this region. The status of the wahoo resource in the WCA remains unclear. Reliable wahoo catch and fishing effort data from the entire WCA, improved knowledge of migration patterns, reproductive characteristics and critical habitat (e.g., preferred spawning areas), validation of age, growth and mortality estimates, and a more comprehensive analysis of stock structure for the entire Atlantic are needed for informed wahoo stock assessment and management.

Palaeoenvironmental implications of palygorskite clays in Eocene deep-water sediments from the western Central Atlantic

Abstract Clay mineral analyses were performed on Eocene sediments from drill sites in the western Central Atlantic. The investigated sites cover the full range of early Palaeogene deep waters above and below the calcite compensation depth (CCD), but otherwise represent different depositional and hydrographic regimes. Palygorskite clays with authigenic microstructures were discovered in Lower Eocene hemipelagic sediments from the distal end of the Blake Nose depth transect and in pelagic clays of the same age from the distal Nares Abyssal Plain, where terrigenous input was reduced. Palygorskite clays were not detected in coeval sediments from a distal near-CCD setting on Bermuda Rise that received major terrigenous input. The distribution of palygorskite clays at these sites, the microstructures of the constituent minerals, their absence from contemporaneous deposits on the American margin, and the position of the northerly sites outside the range of a potential African aeolian supply strongly suggest an authigenic origin of these clays at the early Eocene sea floor. Palygorskite clays are widely distributed in lower Eocene sediments from about 50° N to 50° S palaeolatitude. The most widespread distributions and peak abundances in Atlantic oceanic sediments are reported from shelf to deep-water sites of the palaeo-tropical and -subtropical belt and correlate with the Early Eocene period of extreme warmth. Marine authigenic palygorskite clay may provide an indication of the localities and the time periods that were characterized by high bottom-water temperatures, by elevated alkalinity, silica and magnesium concentrations, and by reduced sediment accumulation rates.

Precautionary assessment and management of dolphinfish in the Caribbean

Dolphinfish in the Caribbean are fast growing and short-lived, living for about 12 to 18 months in the southern Caribbean and a maximum of 2-3 years in the north of the region. They are believed to be highly migratory, are seasonally abundant, and likely to have a more complex stock structure than the larger oceanic epipelagic species. Most of the information on dolphinfish in the western central Atlantic comes from studies in the waters of the USA and the eastern Caribbean, and there is a general paucity of information particularly for stock-based management of this species. No Caribbean country undertakes regular assessment of dolphinfish, or has put in place any species-specific management program. Yield-per-recruit analyses for this species in the eastern Caribbean suggest that maximization of Y/R is likely to lead to very low levels of mature stock biomass. A stock recruitment analysis does not show any dependency of recruitment on stock size within the observed stock size range. This suggests that recruitment failure could be sudden at some threshold below the minimum observed stock size, probably at about one third of the average observed stock size. Given the trends observed in landings of dolphinfish, a precautionary approach to management is needed for this species in the western central Atlantic. Given the migratory, shared nature of the dolphinfish resource, a regional approach to assessment and management is required. However, the institutional basis for this approach does not currently exist within the region in a form that is functional. The membership of the International Commission for the Conservation of Atlantic Tunas (ICCAT) does not include any of the small island states where dolphinfish is of primary importance. ICCAT would need to establish a regional presence in order to serve the needs of Caribbean states. The FAO Western Central Atlantic Fishery Commission (WECAFC) does not operate in a mode which would allow it to address this issue. The Association of Caribbean States is too new to address it within the near future. Subregional organizations with fisheries programs, such as the Caribbean Community (CARICOM) and the Organisation of Eastern Caribbean States (OECS), represent only a subset of states. However, given the ratification of United Nations Convention on the Law of the Sea (UNCLOS) and the recent International Agreement on Highly Migratory Stocks and Straddling Stocks, these organisations could take the initiative to establish a regional management programme for dolphinfish.

Dinoflagellate cysts of the Early Cretaceous North Atlantic Ocean

Early Cretaceous dinoflagellate cysts were reinvestigated from nine deep-sea sites of the North and Central Atlantic. In general the zonation scheme developed for the western Central Atlantic ( Habib, 1977; Habib and Drugg, 1983) can also be applied to the eastern Central Atlantic. Comparison with the probabilistic zonation of Gradstein et al. (1992) show, however, that the first occurrences of the important marker species Druggidium apicopaucicum, Druggidium deflandrei, Druggidium rhabdoreticulatum and Odontochitina operculata appear to occur slightly later in the eastern Central Atlantic in respect to nannofossils and benthic foraminifers. Muderongia neocomica has a shorter stratigraphic range in the eastern Central Atlantic than in the western Central Atlantic.

Natural fishery management areas in the Western Central Atlantic region

The extent to which the region covered by the Western Central Atlantic Fishery Commission (WECAFC) of the United Nation's Food and Agriculture Organization (FAO) consists of distinct faunal regions that could be used as a basis for defining fishery management areas is examined using the distribution areas of fishes and invertebrates from FAO species-identification sheets. The region was divided into 26 areas, and the occurrence of species in four groups—demersal fishes, pelagic fishes, molluscs, and crustaceans—was used in a cluster analysis of the areas. The study indicates a high degree of faunal homogeneity. However, if for logistic reasons it were necessary to define management areas within the WECAFC region, three major areas could be considered on the basis of faunal distribution: coastal North America, including the Gulf of Mexico; coastal Central and South America, including Trinidad and Tobago; and the Caribbean islands, the Greater and Lesser Antilles, including the Bahamas. Because faunal differences between these areas are weak, especially for pelagics, other practical fishery management considerations may appropriately override biogeographic considerations. However, for the same reason, subareas within the WECAFC region cannot reasonably be considered in total isolation. Thus, it may be more appropriate to concentrate fishery management efforts along fishery-specific lines, rather than geographically.

The vertical structure of the zonal and meridional pressure gradients in the equatorial Atlantic during 1983 and 1984

The vertical structures (relative to 500 dbar) of the equatorial pressure gradients, as well as the meridional pressure gradients at the equator in the Gulf of Guinea, were studied in response to the seasonal synoptic wind field from eight FOCAL (programme Françis Océan-Climat Atlantique équatorial) basin-wide hydrographic cruises in the equatorial Atlantic form October 1982 to September 1984. The vertically integrated zonal pressure gradient to 130 m was in equilibrium with the zonal wind stress in the western-central Atlantic. In the Gulf of Guinea, the frictional influence of the average local wind stress did not penetrate below the strong equatorial thermocline lying at the mean depth of 50 m. A very dramatic 50 m deepening of the equatorial thermocline occurred in February 1984 in the eastern equatorial Atlantic, following a basin-wide relaxation of the winds in December 1983–January 1984. The resulting large zonal pressure gradient anomaly of February 1984 in the Gulf of Guinea was not forced by the local wind stress. The meridional structure of the first empirical orthogonal function of the sea levels at 6°E, as well as the vertical structure of the pressure gradient anomalies in the Gulf of Guinea, suggests a contribution of the second baroclinic mode during this warm event. Cross correlation statistics of bandpass filtered sea levels at 29°21'W and 6°31'E bolsters the occurrence of remotely forced second vertical mode of Kelvin waves between February 1983 and November 1984 in the equatorial Atlantic.