Eastern Gulf Of Mexico Research Articles

Reef fish assemblages differ both compositionally and functionally on artificial and natural reefs in the eastern Gulf of Mexico

Reef fish assemblages differ both compositionally and functionally on artificial and natural reefs in the eastern Gulf of Mexico

Vertebral chemistry distinguishes regional populations of Blacktip Sharks in the northern Gulf of Mexico

AbstractObjectiveUnderstanding the spatial connectivity of elasmobranch populations is critical for regional fisheries management. The Blacktip Shark Carcharhinus limbatus is abundant in coastal waters of the Gulf of Mexico (GoM) and important in recreational and commercial fisheries. Based on genetic and tagging studies, GoM Blacktip Sharks are currently managed under separate quotas between the eastern and western GoM (divided at 88°W), but no studies have used vertebral chemistry to assess the population structure of adult Blacktip Sharks.MethodsWe compared vertebral elemental signatures (barium [Ba], magnesium [Mg], manganese [Mn], strontium [Sr], and zinc [Zn]) for the first year of life with last occupied habitats (vertebral edges) in Blacktip Sharks collected from the western (Texas and Louisiana) and eastern (Alabama and Florida) coastal waters of the northern GoM.ResultWe found significant regional differences in Ba, Mg, Mn, and Sr vertebral edge signatures, suggesting ecological separation of Blacktip Sharks. Significant correlation between first‐year and edge signatures suggested a high degree of residency between life stages. Cross‐validated discriminant function analyses yielded highest regional classification accuracies when Florida sharks were grouped separately west of 88°W (90%), demonstrating the unique elemental signatures of eastern versus western GoM Blacktip Sharks under current management delineations.ConclusionCombined, these findings demonstrate that trace element markers can distinguish regional populations of Blacktip Sharks and provide a complimentary approach in addition to genetics and physical tagging to support current stock management efforts.

Mesoscale eddies in the Gulf of Mexico: A three-dimensional characterization based on global HYCOM

The Gulf of Mexico (GoM) is characterized by strong mesoscale eddy activities that have been studied extensively, yet the comprehensive three-dimensional (3-D) kinematic properties of GoM eddies are still not well documented. In this study, the 3-D mesoscale eddy activities in the upper layer (0–800 m) of the GoM are characterized using 14-year (1997–2010) global Hybrid Coordinate Ocean Model (HYCOM) outputs. Most eddies in the upper layer (both cyclonic and anticyclonic) have radii of ∼30–60 km and lifespans shorter than 30 days. The spatial distributions of GoM eddies do not vary much with depth, while their intensity decreases with depth. The size of cyclonic eddies does not vary much with depth, while the size of anticyclonic eddies decreases slightly with depth. Cyclonic eddies are often found to be generated in the eastern GoM (especially in the Loop Current region), the Bay of Campeche, and on the continental slope of the Campeche Bank, while anticyclonic eddies are often generated on the northeastern and northwestern GoM continental slopes, and in the central GoM (near 24°N) and the Bay of Campeche (92–94°W). In addition, long-lived GoM eddies (e.g., lifespan >150 days) tend to have intermediate eddy intensity (e.g., 0.13–0.32 for cyclonic eddies at the 10 m level). Both cyclonic and anticyclonic eddies are found to play an important role in the horizontal and vertical transport of heat and salt, and eddy-induced anomalies of water temperature and salinity at both surface and subsurface are generally more pronounced in the eastern GoM than in the western GoM.

Modeling the larval dispersal and connectivity of Red Snapper (Lutjanus campechanus) in the Northern Gulf of Mexico

Advancements in computing power and improved biophysical dispersal models, have enhanced our ability to realistically simulate distributions and behaviors of fish larvae. In this study, a 1 km high-resolution ocean model capable of capturing the ocean's mesoscale and sub-mesoscale motions is integrated with a biophysical dispersal model that considers a range of larval behaviors. Together they are used to investigate the dispersal and connectivity of Red Snapper (Lutjanus campechanus) larvae, a key species for both commercial and recreational fisheries in the northern Gulf of Mexico (GOM). We quantify how various larval behaviors influence the spatiotemporal dispersal, connectivity and settling of Red Snapper larvae focusing on egg buoyancy, larvae swimming capability, and ontogenetic vertical migration. Alongside habitat preferences, the ocean advection of Red Snapper larvae is crucial in shaping their dispersal patterns. Moreover, our simulations suggest different settling and connectivity characteristics between the eastern and western GOM. These results, indicate the need to divide these regions into distinct entities for stock management, rather than treating them as a unified stock as conventionally done.

An Aggregation of the Pandalid Shrimp, Heterocarpus ensifer, on Deep Reef Habitats of the West Florida Slope, Eastern Gulf of Mexico

An Aggregation of the Pandalid Shrimp, Heterocarpus ensifer, on Deep Reef Habitats of the West Florida Slope, Eastern Gulf of Mexico

Pelagic Sargassum in the Gulf of Mexico driven by ocean currents and eddies

Pelagic Sargassum in the Gulf of Mexico (GoM) plays an important role in ocean biology and ecology, yet our knowledge of its origins and transport pathways is limited. Here, using satellite observations of Sargassum areal density and ocean surface currents between 2000 and 2023, we show that large amounts of Sargassum in the GoM can either originate from the northwestern GoM or be a result of physical transport from the northwestern Caribbean Sea, both with specific transport pathways. Sargassum of the northwestern GoM can be transported to the eastern GoM by ocean currents and eddies, eventually entering the Sargasso Sea. Sargassum entering the GoM from the northwestern Caribbean Sea can be transported in three different directions, with the northward and eastward transports governed by the Loop Current System (LCS) and westward transport driven by the westward extension of the LCS, the propagation or relaying of ocean eddies, the wind-driven westward currents on the Campeche Bank with or without eddies, and the westward currents with/without currents associated with eddies in the northern/central GoM. Overall, the spatial distribution patterns of pelagic Sargassum in the GoM are strongly influenced by the LCS and relevant eddies.

Signatures of Oceanic Wind Events in Convection-Resolving WRF Model Simulations

Abstract Analyses of cloud-top temperature and lightning characteristics of 48 Weather Research and Forecasting (WRF) Model–simulated ocean-based wind events, with 1-min temporal and 0.5-km horizontal resolution, revealed signatures similar to the corresponding 13 observed events detected by buoys and Coastal-Marine Automated Network (C-MAN) stations as shown in prior research on ocean-based wind events by the first author. These events occurred in the eastern Gulf of Mexico and in the Atlantic Ocean from Florida northward through South Carolina. The coldest WRF cloud-top temperature (WCTT) and peak WRF-estimated lightning flash rate values of the model-simulated events, where each event was required to have a negative vertical velocity of at least 10 m s−1 in the lowest 2 km associated with a convective storm, occurred at an average of 4.2 and 1.1 min prior to the events, respectively. With 36 of the events, the peak estimated flash rate occurred within 5 min of the coldest WCTT. Cloud depth typically increased as the WCTT decreased, and the maximum depth occurred at an average of 2.9 min prior to the events. Thermal cooling and precipitation loading provided negative buoyancy needed to help drive the wind events. Environmental characteristics of the model-simulated ocean-based wind events also resembled those associated with land-based wet downbursts, including moist air near the surface, lapse rates near moist adiabatic, and low cloud bases.

A New Species of Fenimorea (Gastropoda: Drilliidae), from the Eastern Gulf of Mexico

A new species of Drilliidae, Fenimorea falloni, is named from relatively deep water, inhabiting the easternmost half of the Gulf of Mexico, and is compared with similar congeners from the Gulf of Mexico. This new Fenimorea is a large, immaculately white species with strong shouldered whorls and beaded spiral threads, which differentiates it from other taxa.

Regional Variation in the Trophic Ecology of Wahoo (Acanthocybium solandri) in the Western Atlantic Ocean

Intrinsic tracers, such as stable isotopes of carbon and nitrogen, are common dietary markers that accumulate in the muscle tissue of consumers and can be used to determine the dietary sources and trophic positions of consumers. The aim of this study was to assess regional variation in the trophic ecology of wahoo (Acanthocybium solandri) using bulk stable isotopes. Muscle biopsies of wahoo were collected from four regions in the western Atlantic Ocean: the eastern Gulf of Mexico, western Gulf of Mexico, Northwest Atlantic Ocean, and Caribbean Sea. Muscle tissue δ13C and δ15N values for wahoo ranged from −15.8‰ to −18.8‰ and from 7.2‰ to 12.8‰, respectively. Wahoo collected in the Caribbean Sea displayed the highest mean δ13C value (−16.3‰), and individuals from this region were statistically different from the three other regions sampled. Mean δ15N values were elevated for wahoo collected in the eastern and western Gulf of Mexico (11.4‰ and 11.1‰, respectively), and the values were over 2‰ higher than samples from the Northwest Atlantic Ocean and Caribbean Sea. Trophic position (TP) was estimated using δ15N baselines (zooplankton) and δ15N wahoo values for each region, and mean TP was 0.4 to 0.9 higher in the Caribbean Sea relative to the three other regions, suggesting that wahoo in this region feed on higher-trophic-level prey. The results indicate that δ15N baselines and the trophic positions of wahoo each vary as a function of their geographic location, which supports the hypothesis that this species feeds opportunistically throughout its range.

Nototanoides oliveri, a new sponge-dwelling nototanaid tanaidacean (Crustacea, Tanaidomorpha, Tanaidacea) from eastern Gulf of Mexico, with an illustrated taxonomic key, and the first record of harpacticoid copepods within the marsupium of ovigerous female tanaids.

A new species of tanaidacean, Nototanoides oliveri sp. nov. from the eastern part of the Gulf of Mexico is described and illustrated. The new species appears to be most closely related to the recently described western Atlantic species, N. polytrichus. It can be easily distinguished from that species, as well as the other members of the genus, N. trifurcatus and N. ohtsukai, by a combination of characters, including: (1) female antennular article-3 with up to 11 aesthetascs (2) female maxilliped palp article-2 with multifurcate spiniform seta and (3) male cheliped basis having mid-ventral margin swollen, forming a rounded apophysis/protuberance. In addition, an unknown living harpacticoid copepod is reported for the first time within the marsupium of ovigerous females of Tanaidacea. An illustrated key to the four species comprising the genus Nototanoides is presented.

Near-inertial oscillations in the deep Gulf of Mexico

Near-inertial oscillations (NIOs) are important for maintaining turbulent mixing that affects ocean circulation, biogeochemistry, and climate. The spatial and temporal variability of NIOs in the deep part of the Gulf of Mexico (GoM) has rarely been reported. In this study, a collection of moored current observations was used to examine the spatiotemporal variability of NIOs in the GoM. In the upper layer (0–800 m), a strong seasonal variability of NIOs appears in the eastern GoM with larger amplitudes in winter than in summer and is attributed to the seasonal variability of surface winds and mixed layer depth. In the bottom layer (within 400 m above the bottom), strong NIOs are found in the middle and eastern GoM and show weaker seasonal variability. While winds still matter for the seasonal variability of NIOs in the bottom layer in the eastern GoM, low-frequency flows generally play a more important role in regulating NIOs through interactions with topography, particularly on the continental slope.

Fluvial-style migration controls autogenic aggradation in submarine channels: Joshua Channel, eastern Gulf of Mexico

Abstract There has been debate over the processes acting on deep-water channels, with comparisons made to the evolution of meandering fluvial systems. We characterized a three-dimensional seismic-reflection dataset of the Joshua deep-water channel–levee system located in the eastern Gulf of Mexico and interpreted 13 horizons showing its kinematic evolution over a 25 km reach. Over this reach, we documented channel migration through systematic bend expansion and downstream translation, which was sustained through channel aggradation as sinuosity increased from 1.25 to 2.3 at abandonment. An abrupt decrease in sinuosity was associated with a neck cutoff, which changed the subsequent migration direction of the channel in that locality. These processes are analogous to the evolution of meandering fluvial systems. We show that increasing channel sinuosity correlates to a reduction in channel slope and hypothesize that this promoted increasingly depositional turbidity currents that led to channel aggradation. Using a simple forward stratigraphic model in which vertical movements of the channel are governed by a stream power law, we show how aggradation can be driven autogenically. Trends in sinuosity, aggradation and slope are in broad agreement between the Joshua Channel and the model. This highlights the potential importance of intrinsic channel processes as a control on system evolution.

Toward generalized models for machine-learning-assisted salt interpretation in the Gulf of Mexico

Interpreting salt bodies in the Gulf of Mexico (GoM) can be complex due to various factors affecting the accuracy of automated techniques. Variability of salt structures, seismic acquisition parameters, and imaging algorithms can impact the resulting seismic image. These differences can result in variations in seismic resolution and texture, making it challenging to develop automated interpretation techniques that are accurate and reliable for identifying salt bodies in the GoM. However, using seismic images with similar acquisition parameters and processing methods minimizes these differences and makes machine-learning (ML) models applicable. Utilizing nine data sets from the eastern GoM, a nine-fold cross-validation technique was applied to measure the generalization performance of the ML model. This method involves using one data set as the test set and the remaining eight for training and repeating the process for all subsets. We further applied an ensemble of the nine models to predict salt on a new unseen survey in Green Canyon. The study aimed to illustrate how salt variability and morphology in the GoM can impact the ability of the ML algorithm to predict salt bodies on unseen data.

Metabarcoding analysis of meiobenthic biodiversity along the Gulf of Mexico continental shelf

This study explores how diverse the meiobenthic (meiofauna and other benthic micro-eukaryotes) community is throughout the United States Gulf of Mexico (GOM) continental shelf. In late 2010 and 2011, 51 sediment samples were collected along GOM from Texas through Florida at a range of depths (40m–496m). An additional six deep-sea slope sediment cores were collected in December 2010 near the Deepwater Horizon platform (1370–1385m and 1865m). Metabarcoding of the 18S hypervariable V9 region was conducted to assess biodiversity. Within continental shelf samples, there was greater meiobenthic diversity off the Eastern GOM coast in comparison to both Central and Western GOM coast locations. The Eastern GOM coast has known sediment differences from Western GOM sites. These sediment differences along with influences from the Gulf of Mexico Loop Current may account for observed variations in GOM meiobenthic diversity.

The Loop Current Circulation Over the MIS 9 to MIS 5 Based on Planktonic Foraminifera Assemblages From the Gulf of Mexico

AbstractThe loop current (LC) in the Gulf of Mexico (GoM) is part of the western North Atlantic circulation. Recording its strength and slowdown variations can help us characterize the regional climate over the Late Pleistocene. To reconstruct the sea surface and the LC intensity in the eastern GoM, we study the distribution patterns of planktonic foraminifera in the core EN‐032‐18PC, spanning the end of Marine Isotope Stage (MIS) 9 to early MIS‐4. We reconstructed a sequence of paleoceanographic events based on stable isotopes (δ18O and δ13C) of the surface dweller Globigerinoides ruber and two faunal assemblages. The first assemblage explains most of the glacial and late interglacial periods, suggesting a subtropical environment with a deep thermocline and a reduced LC due to a moderate inflow of warm Caribbean waters. The second assemblage explains the warmest interglacial substages, dominated by tropical species, a shallow thermocline, and an extended LC, driven by summer insolation. Overall, surface ocean conditions led to more ecological successions and instability during the warmest interglacial substages than during glacial periods, as supported by the stable isotope records. Besides the GoM relationship to AMOC, as a regulator of heat transport to higher latitudes, we suggest that fluctuations in the LC rely on the migration of atmospheric circulation patterns and astronomical insolation forcing.

Vulnerability of Estuarine Systems in the Contiguous United States to Water Quality Change Under Future Climate and Land‐Use

AbstractChanges in climate and land‐use and land‐cover (LULC) are expected to influence surface water runoff and nutrient characteristics of estuarine watersheds, but the extent to which estuaries are vulnerable to altered nutrient loading under future conditions is poorly understood. The present work aims to address this gap through the development of a new vulnerability assessment framework that accounts for (a) estuarine exposure to projected changes in total nitrogen (TN) and total phosphorus (TP) loads as a function of LULC and climate change under several scenarios, (b) sensitivity, and (c) adaptive capacity. The framework was applied to 112 estuaries and their contributing watersheds across the contiguous U.S., specifically to look at regional variability in estuarine vulnerability to nutrient loading. Study findings revealed that the largest increases in estuarine nutrient loads are expected in the North and South Atlantic regions and eastern Gulf of Mexico, while the lowest increases are expected in the North and South Pacific regions and the western Gulf of Mexico. However, the North Atlantic and the South Pacific had the highest adaptive capacity, which could potentially counteract the effects of LULC and climate change on nutrient loads. Strong variation in predicted estuarine nutrient loads was observed as a function of climate model projections, while projected LULC changes were more consistently associated with elevated loads. Our findings illustrate the benefits of integrating natural and socio‐ecological factors to identify opportunities to develop adaptation plans and policies to mitigate ecological degradation in vitally important estuaries.

Death Assemblages Record Significant Range Contraction in a Molluscan Species of Concern from the Eastern Gulf Of Mexico

Marine habitats are in decline due to increasing anthropogenic pressures, but baseline data on species distributions needed to manage and conserve populations are lacking. Incorporating death assemblages into species assessments can create a more accurate understanding of pre-anthropogenic communities than survey records alone. In this study, we conducted a live-dead analysis on mollusks from a new 2008-2018 dredge survey in the eastern Gulf of Mexico. We selected the predatory banded tulip snail, Cinctura hunteria, as a test case for assessment because this species is one of several designated by the Florida Fish and Wildlife as a species of concern. Using spatial count data for shells in our samples, we estimated density values for each taxonomic grade over the sampled area using IDW spatial interpolation. These maps reveal large areas of occupation across the west Florida shelf for two taxonomic grades of dead shells but loss of offshore occurrence for live records. One explanation for the lack of occurrences in offshore habitats is that, unlike dead shell records, there is no time averaging accumulation of live shells. Time averaging increases detectability of species in habitats where they are rare. However, independent fisheries data from live-only animal surveys not only mirror our live-dead results but suggest that habitat loss in our live-dead comparisons was rapid and occurred in the late 1980s or early 1990s. Thus, live-dead comparisons reveal both natural baselines as well as anthropogenic changes in distribution without being significantly distorted by time-averaging biases. Including live-dead data can greatly improve species assessments when long-term survey records are unavailable and provide a key tool in combatting biodiversity loss across marine ecosystems.

Evaluating red tide effects on the West Florida Shelf using a spatiotemporal ecosystem modeling framework

The West Florida Shelf (WFS), located in the eastern Gulf of Mexico, fosters high species richness and supports highly valuable fisheries. However, red tide events occur regularly that can impact fisheries resources as well as ecosystem state, functioning, and derived services. Therefore, it is important to evaluate and quantify the spatiotemporal impacts of red tides to improve population assessments, mitigate potential negative effects through management, and better understand disturbances to support an ecosystem-based management framework. To model red tide effects on the marine community, we used Ecospace, the spatiotemporal module of the ecosystem modeling framework Ecopath with Ecosim. The inclusion of both lethal and sublethal response functions to red tide and a comprehensive calibration procedure allowed to systematically evaluate red tide effects and increased the robustness of the model and management applicability. Our results suggest severe red tide impacts have occurred on the WFS at the ecosystem, community, and population levels in terms of biomass, catch, and productivity. Sublethal and indirect food-web effects of red tide triggered compensatory responses such as avoidance behavior and release from predation and/or competition.. This study represents a step forward to operationalize spatiotemporal ecosystem models for management purposes that may increase the ability of fisheries managers to respond more effectively and be more proactive to episodic mortality events, such as those caused by red tides.

Genetic connectivity in Twospot flounder (Bothus robinsi) across the Gulf of Mexico, inferred with single nucleotide polymorphisms from larvae and adults

Larval genetic information influences populations’ genetic pools, causing genetic homogenization or structuration. So, knowing about adult and larval genetic information is essential to understand processes such as connectivity. The aims are to evaluate Twospot flounder (Bothus robinsi, a fish with a high dispersal potential) larval pools’ genetic diversity, test if the larvae tend to mix or display collective dispersal, compare genetic information between larvae and adults and evaluate its connectivity. We used ddRADSEQ to genotype 1,034 single nucleotide polymorphic sites from B. robinsi larvae sampled in waters from the Bay of Campeche and the eastern Gulf of Mexico (GOM) and adults sampled on Florida’s continental shelf. Larvae were identified morphologically and by DNA barcoding. We estimated Fst-paired comparations, Principal Components Analysis (PCA), Discriminant Analyses of Principal Components (DAPC), and a Structure analysis to understand genetic trends. With the software COLONY, we made a sibship evaluation. We observed no significant heterogeneity among regions (Fst p-values>0.05). PCA, DAPC, and the Structure Analysis showed one genetic cluster, indicating genetic homogeneity. We did not detect full-sibs or half-sibs. We linked the results with the high dispersal potential of B. robinsi due to a long pelagic larval duration and the potential of ocean dynamics to transport and mix larvae from all GOM shelf areas. These findings suggest that the dispersal potential of B. robinsi is large enough to produce genetic connectivity in all GOM subpopulations and that time spent by its larvae in dispersal pathways is enough to mix larvae from different GOM subpopulations, indicating a panmictic population.

Influence of nearby environment on recreational bycatch of sea turtles at fishing piers in the eastern Gulf of Mexico

Incidental bycatch of sea turtles from recreational fisheries is generally undocumented globally. At Gulf of Mexico fishing piers in the USA, bycatch is a source of injury and potential mortality of sea turtles. Recreational sea turtle bycatch has grown substantially over the last 6 yr, especially at the Navarre Beach Fishing Pier (NW Florida); the reasons for the increase and the impacts this has on the recovery of northern Gulf of Mexico sea turtle populations are largely unknown. In particular, the reasons why fishing piers are attracting sea turtles are not well understood or if the environmental context of other nearby habitats contributes to the bycatch. Using GIS, we analyzed potential environmental predictors of total sea turtle bycatch, across green sea turtles Chelonia mydas, loggerhead sea turtles Caretta caretta, and Kemp’s ridley sea turtles Lepidochelys kempii. We collated bycatch and environmental data from 20 Florida Gulf of Mexico fishing piers. We statistically assessed relationships using generalized additive models and selected the best fit model using the information-theoretic approach. We found that tonnage of nearby artificial reefs (based on defined home range and core use areas) and distance to nearest seagrass bed exhibit positive relationships with green sea turtle bycatch. For combined loggerhead and Kemp’s ridley bycatch, area of preserved water, distance to nearest seagrass bed, tonnage of nearby artificial reefs, and latitude of fishing piers were all predictors in the confidence set, but the shape of the relationships is variable and nonlinear. Further examination of sea turtle bycatch, occupancy of piers, and environmental factors pertaining to sea turtles will likely improve mitigation measures for recreational bycatch.