The west Florida shelf (WFS; Gulf of Mexico, USA) is an important area for commercial and recreational fishing, yet much of it remains unmapped and unexplored, hindering effective monitoring of fish stocks. The goals of this study were to map the habitat at an intensively fished area on the WFS known as “The Elbow”, assess the differences in fish communities among different habitat types, and estimate the abundance of each fish taxa within the study area. High-resolution multibeam bathymetric and backscatter data were combined with high-definition (HD) video data collected from a near-bottom towed vehicle to characterize benthic habitat as well as identify and enumerate fishes. Two semi-automated statistical classifiers were implemented for obtaining substrate maps. The supervised classification (random forest) performed significantly better (p = 0.001; α = 0.05) than the unsupervised classification (k-means clustering). Additionally, we found it was important to include predictors at a range of spatial scales. Significant differences were found in the fish community composition among the different habitat types, with both substrate and vertical relief found to be important with rock substrate and higher relief areas generally associated with greater fish density. Our results are consistent with the idea that offshore hard-bottom habitats, particularly those of higher vertical relief, serve as “essential fish habitat”, as these rocky habitats account for just 4% of the study area but 65% of the estimated total fish abundance. However, sand contributes 35% to total fish abundance despite comparably low densities due to its large area, indicating the importance of including these habitats in estimates of abundance as well. This work demonstrates the utility of combining towed underwater video sampling and multibeam echosounder maps for habitat mapping and estimation of fish abundance.

The West Florida Shelf (WFS) is an extremely important area for both commercial and recreational fisheries. However, the lack of habitat maps in this area makes planning fisheries independent monitoring surveys difficult, and hinders the ability to manage and monitor fish stocks and ecosystems over time. As of 2015, only 5% of the WFS had been mapped in high resolution using a multibeam echosounder with little effort expended to infer and verify habitat type. In 2015, The Continental Shelf Characterization, Assessment, and Mapping Project (C-SCAMP) began using a multibeam echosounder and towed underwater video to map benthic habitats and improve our understanding of fish-habitat relationships on the WFS. For this study, high resolution multibeam bathymetry and co-registered backscatter data were collected and processed. A portion of these areas were then “ground-truthed” using towed video transects to assess habitat type and identify fish. Habitat maps were created using a statistical classification model that predicts benthic habitat type based on the acoustic signature. Progress towards a unified habitat map of the West Florida Shelf will be presented including habitat interpretation of multibeam surfaces collected by other groups prior to this project, particularly focusing on those within Marine Protected Areas. Applications of the resultant habitat maps for fisheries management will be demonstrated and discussed.

Geomorphology and geological processes exert fundamental controls on the occurrence, distribution, and makeup of mesophotic coral ecosystems (MCEs). Two broad geomorphic categories are shelves and slopes. Shelves include outer portions of continental and insular shelves that dip gently into mesophotic depths before reaching the shelf break and have very low gradients (<1 degrees). Other low-gradient habitats include tops of isolated banks. Slope habitats extend from platform breaks down into adjacent basins and can be divided into low-gradient slopes (<30 degrees), steep slopes (similar to 30 to 70 degrees), and walls (>70 degrees). On shelves, MCEs are best developed on positive relief features elevated above the surrounding seafloor. In slope settings, MCE development is typically favored on steep irregular slopes, where coral cover is concentrated on steep-sided buttresses and sediment is channelized into narrow chutes. Relict features related to past sea levels are critically important MCE habitats on both shelves and slopes. Coral and coralline algae remain the primary frame builders in MCEs. However, accretion at mesophotic depths is likely very slow, such that they form only thin biostromal veneers over relict substrates. Sediments in MCEs are dominantly autochthonous skeletal sands and gravels. Although fluxes of sediments to the seafloor in MCEs are typically lower than in shallow reefs, sedimentary dynamics still play an important role. Low-gradient seafloor has an increased potential for accumulation of sediment detrimental to MCEs. In slope settings, downslope bed-load transport of sediment can be orders of magnitude higher than vertical fluxes and likely exerts an important influence on MCEs.

First posted April 3, 2017 For additional information, contact: Director, St. Petersburg Coastal and Marine Science Center U.S. Geological Survey 600 4th Street South St. Petersburg, FL 33701 https://coastal.er.usgs.gov/ Investigations of coastal change at Fire Island, New York (N.Y.), sought to characterize sediment budgets and determine geologic framework controls on coastal processes. Nearshore sediment thickness is critical for assessing coastal system sediment availability, but it is largely unquantified due to the difficulty of conducting geological or geophysical surveys across the nearshore. This study used an amphibious vessel to acquire chirp subbottom profiles. These profiles were used to characterize nearshore geology and provide an assessment of nearshore sediment volume. Two resulting sediment-thickness maps are provided: total Holocene sediment thickness and the thickness of the active shoreface. The Holocene sediment section represents deposition above the maximum flooding surface that is related to the most recent marine transgression. The active shoreface section is the uppermost Holocene sediment, which is interpreted to represent the portion of the shoreface thought to contribute to present and future coastal behavior. The sediment distribution patterns correspond to previously defined zones of erosion, accretion, and stability along the island, demonstrating the importance of sediment availability in the coastal response to storms and seasonal variability. The eastern zone has a thin nearshore sediment thickness, except for an ebb-tidal deposit at the wilderness breach caused by Hurricane Sandy. Thicker sediment is found along a central zone that includes shoreface-attached sand ridges, which is consistent with a stable or accretional coastline in this area. The thickest overall Holocene section is found in the western zone of the study, where a thicker lower section of Holocene sediment appears related to the westward migration of Fire Island Inlet over several hundred years.

First posted March 10, 2017 For additional information, contact: St. Petersburg Coastal and Marine Science Center U.S. Geological Survey 600 4th Street South St. Petersburg, FL 33701 http://coastal.er.usgs.gov/ As part of the Barrier Island Comprehensive Monitoring Program (BICM), scientists from the U.S. Geological Survey (USGS) St. Petersburg Coastal and Marine Science Center conducted a nearshore single-beam bathymetry survey along the south-central coast of Louisiana, from Raccoon Point to Point Au Fer Island, in July 2015. The goal of the BICM program is to provide long-term data on Louisiana’s coastline and use this data to plan, design, evaluate, and maintain current and future barrier island restoration projects. The data described in this report will provide baseline bathymetric information for future research investigating island evolution, sediment transport, and recent and long-term geomorphic change, and will support modeling of future changes in response to restoration and storm impacts. The survey area encompasses more than 300 square kilometers of nearshore environment from Raccoon Point to Point Au Fer Island. This data series serves as an archive of processed single-beam bathymetry data, collected from July 22–29, 2015, under USGS Field Activity Number 2015-320-FA. Geographic information system data products include a 200-meter-cell-size interpolated bathymetry grid, trackline maps, and point data files. Additional files include error analysis maps, Field Activity Collection System logs, and formal Federal Geographic Data Committee metadata.

First posted December 1, 2017 For additional information, contact: St. Petersburg Coastal and Marine Science Center U.S. Geological Survey 600 4th Street South St. Petersburg, FL 33701 As part of the Sea-level and Storm Impacts on Estuarine Environments and Shorelines (SSIEES) project, scientists from the U.S. Geological Survey (USGS) St. Petersburg Coastal and Marine Science Center conducted a single-beam bathymetry survey within the estuarine, open-bay, and tidal creek environments of Grand Bay, Alabama-Mississippi, from May to June 2015. The goal of the SSIEES project is to assess the physical controls of sediment and material exchange between wetlands and estuarine environments along the northern Gulf of Mexico, specifically Grand Bay, Alabama-Mississippi; Vermilion Bay, Louisiana; and, along the east coast, within Chincoteague Bay, Virginia-Maryland. The data described in this report provide baseline bathymetric information for future research investigating wetland-marsh evolution, sediment transport, erosion, recent and long-term geomorphic change, and can also support the modeling of changes in response to restoration and storm impacts. The survey area encompasses more than 40 square kilometers of Grand Bay’s waters.

Shelf-margin carbonate mounds in water depths of 116–135m in the eastern Gulf of Mexico along the central west Florida shelf were investigated using swath bathymetry, side-scan sonar, sub-bottom imaging, rock dredging, and submersible dives. These enigmatic structures, known to fisherman as the “Sticky Grounds”, trend along slope, are 5–15m in relief with base diameters of 5–30m, and suggest widespread potential for mesophotic reef habitat along the west Florida outer continental shelf. Possible origins are sea-level lowstand coral patch reefs, oyster reefs, or perhaps more recent post-lowstand biohermal development. Rock dredging recovered bioeroded carbonate-rock facies comprised of bored and cemented bioclastics. Rock sample components included calcified worm tubes, pelagic sediment, and oysters normally restricted to brackish nearshore areas. Several reef sites were surveyed at the Sticky Grounds during a cruise in August 2010 with the R/V Seward Johnson using the Johnson-Sea-Link II submersible to ground truth the swath-sonar maps and to quantify and characterize the benthic habitats, benthic macrofauna, fish populations, and coral/sponge cover. This study characterizes for the first time this mesophotic reef ecosystem and associated fish populations, and analyzes the interrelationships of the fish assemblages, benthic habitats and invertebrate biota. These highly eroded rock mounds provide extensive hard-bottom habitat for reef invertebrate species as well as essential fish habitat for reef fish and commercially/recreationally important fish species. The extent and significance of associated living resources with these bottom types is particularly important in light of the 2010 Deepwater Horizon oil spill in the northeastern Gulf and the proximity of the Loop Current. Mapping the distribution of these mesophotic-depth ecosystems is important for quantifying essential fish habitat and describing benthic resources. These activities can improve ecosystem management and planning of future oil and gas activities in this outer continental shelf region.

First posted August 1, 2016 For additional information, contact: Director, St. Petersburg Coastal and Marine Science Center U.S. Geological Survey 600 4th Street South St. Petersburg, FL 33701 (727) 502–8000 http://coastal.er.usgs.gov As part of the Barrier Island Monitoring Project, scientists from the U.S. Geological Survey (USGS) St. Petersburg Coastal and Marine Science Center conducted nearshore geophysical surveys off Breton and Gosier Islands, Louisiana, in July and August of 2014. To assist the United States Fish and Wildlife Service (USFWS) with restoration planning efforts, the USGS was tasked with answering fundamental questions about the physical environment of the southern Chandeleur Islands, including the geology, morphology, and oceanography. Baseline data needed to answer these questions were either insufficient or missing. The USGS conducted a comprehensive geologic investigation in the summer of 2014, collecting geophysical and sedimentological data.Breton Island, located at the southern end of the Chandeleur Island chain in southeastern Louisiana, was recognized as a natural, globally significant nesting sanctuary for several bird species and was established as the Breton National Wildlife Refuge (NWR) in 1904. The areal extent of Breton Island has diminished 90 percent since 1920. Land loss is attributed to ongoing relative sea-level rise, diminished sediment supply, and storm impacts. The bird population on Breton Island has also declined over the years, most notably after Hurricane George in 1998 and after Hurricane Katrina in 2015; the latter completely submerged the island. Despite decreasing habitable acreage, migratory seabirds continue to return and nest on Breton Island. To prevent the island from being submerged in the future, and to protect, stabilize, and provide more nesting and foraging areas for the bird population, the USFWS proposed a restoration effort to rebuild Breton Island to its pre-Katrina footprint.This data series serves as an archive of processed interferometric swath and single-beam bathymetry data, and side-scan sonar data, collected in the nearshore of Breton and Gosier Islands, NWR, Louisiana. The data were collected during two USGS cruises (USGS Field Activity Numbers 2014-314-FA and 2014-317-FA) in July and August 2014. Geographic information system data products include a 100-meter-cell-size interpolated bathymetry grid, trackline maps, and point data files. Additional files include error analysis maps, Field Activity Collection System logs, and formal Federal Geographic Data Committee metadata.NOTE: These data are scientific in nature and are not to be used for navigation. Any use of trade names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

Bathymetric and seismic surveys of the Florida Middle Ground area on the West Florida Shelf, aid in identifying the structure and origin of these unusual banks. Recent cores recovered from the area by other workers provide a useful context for interpreting geophysical data. Data indicate that high-relief banks may be largely biohermal, whereas low-relief banks are likely composed of clastic sediments with a vermetid gastropod carbonate caprock. The most seaward ridges reveal subtle internal aggradational stratal geometries indicating a possible origin as a subtidal shoal, or paleoshoreline, deposited during or immediately following the Younger Dryas. Bank locations appear to be related to the antecedent geology, specifically the occurrence of the highly weathered Miocene surface. High-resolution multibeam bathymetry and backscatter data reveal varied morphologies that suggest the influence of karst processes, linear trends suggestive of wave-reworked intertidal hardbottom, poorly lithified and benthic fauna-mantled beach ridges or sand waves, or perhaps surface-water flow patterns during lowstand exposure. Circular depressions on low banks are of the same scale and morphology as modern shallow karst features in the Everglades. An episodically active sand-wave field occurs in the northern study area, and provides sediment to the system. Scoured depressions surrounding carbonate banks also indicate intense, episodic current activity originating from shelf and wave currents. A partial modern analog for some of the morphology of this system may be the Ten Thousand Islands and portions of the Florida Everglades. Data indicate that the banks represent a brief period of reef growth (possibly mixed coral and vermetid) constrained by two rapid sea-level rise events, and impacted by changing water quality and trophic conditions.

This paper presents a general review of the distribution of mesophotic coral ecosystems (MCEs) in relationship to geomorphology in US waters. It was specifically concerned with the depth range of 30–100 m, where more than 186,000 km2 of potential seafloor area was identified within the US Gulf of Mexico/Florida, Caribbean, and main Hawaiian Islands. The geomorphology of MCEs was largely inherited from a variety of pre-existing structures of highly diverse origins, which, in combination with environmental stress and physical controls, restrict the distribution of MCEs. Sea-level history, along with depositional and erosional processes, played an integral role in formation of MCE settings. However, mapping the distribution of both potential MCE topography/substrate and existing MCE habitat is only beginning. Mapping techniques pertinent to understanding morphology and MCE distributions are discussed throughout this paper. Future investigations need to consider more cost-effective and remote methods (such as autonomous underwater vehicles (AUVs) and acoustics) in order to assess the distribution and extent of MCE habitat. Some understanding of the history of known MCEs through coring studies would help understand their initiation and response to environmental change over time, essential for assessing how they may be impacted by future environmental change.

Multiple, spatially restricted, partly enclosed karst sub-basins with as much as 100 m of relief occur on a mid-carbonate platform setting beneath the modern estuaries of Tampa Bay and Charlotte Harbor located along the west-central Florida coastline. A relatively high-amplitude seismic basement consists of the mostly carbonate, upper Oligocene to middle Miocene Arcadia Formation, which has been significantly deformed into folds, sags, warps and sinkholes. Presumably, this deformation was caused during a mid-to-late Miocene sea-level lowstand by deep-seated dissolution of carbonates, evaporites or both, resulting in collapse of the overlying stratigraphy, thus creating palaeotopographic depressions.Seismic sequences containing prograding clinoforms filled approximately 90% of the accommodation space of these western Florida sub-basins. Borehole data indicate that sediment fill is mostly siliciclastic deposited within deltaic depositional systems. The sedimentary fill in the Tampa Bay and Charlotte Harbor sub-basins is mostly assigned to the upper Peace River Formation of late Miocene to early Pliocene age. This fill is part of a > 1000 km long, Tertiary siliciclastic deposit that stretches north-to-south down peninsular Florida. Sediment fill of these two sub-basins is linked to erosion and remobilization of pre-existing, middle Miocene quartz-rich sediments via enhanced sediment transport by local, short-length rivers and discharge into coastal-marine depositional environments. Increased sediment discharge possibly resulted from amplified thunderstorm activity and enhanced runoff during a warm period of the Pliocene.Rather than incised valley fills or reef-margin, backfilled basins, Tampa Bay and Charlotte Harbor represent spatially restricted, sediment-filled karst palaeotopographic lows. The 'dimpling' of a carbonate platform by karst sub-basins provides a previously unrecognized mechanism for the creation of accommodation that can result in the 'drowning' of a carbonate platform by siliciclastics.

Beach nourishment requires large volumes of sand from offshore and new sources are constantly sought for development. The sediment-starved continental shelf off the central-west coast of Florida has traditionally supplied beach-quality sediments from ebb-tidal shoals and nearshore sand sheets, but as these supplies dwindle, sand searches increasingly look farther offshore for resources. Widely spaced sediment ridges, interspersed by karstified limestone seafloor (hard grounds), offer potential as sand resources that can be exploited by dredging to renourish eroded beaches for shore protection. The sand ridges, late Holocene in age, are generally shoreface detached, sediment starved, and clustered in "ridge fields." Six sediment ridge fields identified along 285 km of coast (Anclote, Sand Key, Sarasota, Manasota, Captiva, and Collier) contain about 1.4 billion cubic meters of sediments that are potentially available for dredging. Evaluation of these sediment sources, within the purview of the USMinval Code, requires the determination of resources, reserves, and level of certainty of assessment applied to a rating of resource potential. Present research is attempting to identify the overall resource potential with an eye toward eventually determining sand volumes in reserves, which will be much less than the total sand resource volume.

Understanding relative sea level (RSL) rise during periods of rapid climatic change is critical for evaluating modern sea level rise given the vulnerability of Antarctic ice shelves to collapse [Hodgson et al, 2006], the retreat of the world's glaciers [Oerlemans, 2005], and mass balance trends of the Greenland ice sheet [Rignot and Kanagaratnam, 2006]. The first‐order pattern of global sea level rise following the Last Glacial Maximum (LGM, ∼21,000 years ago) is well established from coral [Fairbanks, 1989], continental shelf [Hanebuth et al, 2000], and other records [Pirazzoli, 2000] and has been integrated into a global ICE‐5G model of glacio‐isostatic adjustment (GIA) [Peltier, 2004]. However, uncertainty introduced by paleo water depth of sea level indicators, radiocarbon chronology (i.e., reservoir corrections for marine shell dates), postglacial isostatic adjustment, and other processes affecting vertical position of former shorelines produces scatter in RSL curves, limiting our knowledge of sea level rise during periods of rapid glacial decay.One example of this limitation is the Gulf of Mexico/Florida region where, despite decades of study, RSL curves produce two conflicting patterns: those showing progressive submergence with a decelerating rate during the past 5000 years [Scholl et al, 1969] and those showing high sea level during the middle of the Holocene [Blum et al, 2001; Balsillie and Donoghue, 2004], where the Holocene represents a geologic epoch that extends from about 10,000 years ago to present times. This discrepancy is emblematic of the uncertainty surrounding Holocene sea level and ice volume history in general.

A Kongsberg Simrad EM 3000 multibeam sonar (Kongsberg Simrad, Kongsberg, Norway) was used to conduct a set of six repeat high-resolution bathymetric surveys west of Indian Rocks Beach (IRB), just to the south of Clearwater, FL, between January and March 2003, to observe in situ scour and burial of instrumented inert mines and mine-like cylinders. Three closely located study sites were chosen: two fine-sand sites, a shallow one located in similar to 13 m of water depth and a deep site located in similar to 14 m of water depth; and a coarse-sand site in similar to 13 m. Results from these surveys indicate that mines deployed in fine sand are nearly buried within two months of deployment (i.e., they sunk 74.5% or more below the ambient seafloor depth). Mines deployed in coarse sand showed a lesser amount of scour, burying until they present roughly the same hydrodynamic roughness as the surrounding rippled bedforms. These data were also used to test the validity of the Virginia Institute of Marine Science (VIMS, Gloucester Point, VA) 2-D burial model. The model worked well in areas of fine sand, sufficiently predicting burial over the course of the experiment. In the area of coarse sand, the model greatly overpredicted the amount of burial. This is believed to be due to the presence of rippled bedforms around the mines, which affect local bottom morphodynamics and are not accounted for in the model, an issue currently being addressed by the modelers. This paper focuses specifically on two instrumented mines: an acoustic mine located in fine sand and an optical instrumented mine located in coarse sand.