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Hydraulic dredging for shellfish is known to create some of the highest levels of disturbance, affecting the benthic microfaunal community and the physical characteristics of the substrate. Properly conducted benthic habitat assessments are complex and time consuming, resulting in assessments not being conducted increasing the uncertainty in post impact studies. Hydraulic dredging for Atlantic surfclams (Spisula soldidissima) took place at Herring Cove, Massachusetts in the winter of 2014–2015 resulting in areas of high impact disturbance of the seafloor. Surveys conducted in the summer of 2015 included hydroacoustics, benthic invertebrate sampling, video, and grain size analysis for the creation of a habitat map of Herring Cove. The four habitats (A–D) identified were a mix of sand, shell, cobble, algae, and eelgrass. Habitat type “D” is a mix of sand, algae and cobble material and occurred at 12 of 18 stations. These 12 stations were distributed across areas of “high” (n = 4), “low” (n = 2), and “no” (n = 6) hydraulic dredge disturbance. Once habitat was accounted for, benthic invertebrate community structure varied significantly (Analysis of similarity; significance level of sample statistic: 0.3%) between areas of “high”, “low” to “no” disturbance. Areas of “low” to “no” dredge track coverage contained high abundances of bivalves, echinoderms, and isopods, whereas highly disturbed areas had highest abundances of polychaetes and oligochaetes. Future mapping efforts, especially surveys with biological components, need to include and quantify the level, type and spatial distribution of anthropogenic alterations. More attention should be given to “reference maps” instead of “baseline maps”. The latter of which omits to acknowledge pre-existing anthropogenic disturbances and has the potential to skew monitoring of restoration and management efforts.

The detection, classification, and localization of targets or features on the seafloor in acoustic data are critical to many disciplines. This is most important in cases where human safety is in jeopardy, such as hazards to navigation, mitigation of mine countermeasures, or unexploded ordnance. This study quantifies the absolute localization of targets, in the form of inert unexploded ordnance, in very shallow waters (2–3 m) on two intertidal bottom types in a meso-tidal environment (tide range = ~3.0 m). The two sites, a sandy intertidal flat and a mixed sand and gravel beach with abundant cobble-sized material, were seeded at low tide with targets (wax-filled 60-, 81-, 105- and 155-mm, projectile and mortar shells). An RTK-GPS was used to collect positional data for the targets and an unoccupied aerial system (UAS) survey was conducted on both sites. At the next high-tide, a vessel-based acoustic survey was performed, and at the subsequent low tide, the targets were re-surveyed with RTK-GPS. We focus here on the sidescan backscatter from a phase-measuring sidescan sonar (PMSS) and the sources of uncertainty for absolute localization. A total of 1426 calls of acoustic targets were made within the sidescan backscatter data, yielding an accuracy of 0.41 ± 0.26 m, with 98.9% of all calls <1 m from their absolute location. Distance from nadir was the most significant source of uncertainty, and targets between 3–7 m had the lowest uncertainty (0.32 ± 0.23 m) with increasing values toward and away from nadir. Bathymetry and bathymetry-mode backscatter were less useful for the detection and classification of targets compared to sidescan backscatter, but once detected, the accuracy of absolute localization were similar. This is likely due to target calls from these two datasets that were orders of magnitude less and that focused on the larger sized targets, thus more work is needed to better understand these differences. Lastly, the absolute localization of targets detected on sandy and cobble bottoms for all datasets were statistically similar. These acoustic instruments, their datasets, and methods presented herein can better document the absolute localization within acoustic data for many uses in very shallow waters. [ABSTRACT FROM AUTHOR]

The Coastal and Marine Ecological Classification Standard (CMECS) was used to create standardized maps of habitats and biotopes by combining CMECS's four stand-alone components: Geoform, Substrate, Biotic, and Water, based on data collected in a shallow New England salt marsh lagoon. East Harbor on Cape Cod, MA, USA, was artificially isolated from tidal flow in the late 1860s. Consequently, estuarine fish and invertebrate populations declined until partial tidal flow was restored in 2002. In early September 2017, we conducted an acoustic survey covering 1.29 km2 (mean depth = 1.27 m) of East Harbor using a vessel mounted phase measuring sidescan sonar. From the acoustic survey data, submerged aquatic vegetation (SAV) was mapped and used for a stratified random sampling scheme. On 2 days in late September 2017, East Harbor was sampled for benthic invertebrates, sediment, and water properties (pH, dissolved oxygen, salinity, and temperature) at sixteen stations (eight bare substrates and eight SAV). As the restoration project develops over time from a newly restored (2002) to a more fully restored (2017) system, links between abiotic and biotic components strengthen. Consequently, we were able to explain 89.39% of species distribution in East Harbor using measured abiotic variables (e.g., sediment characteristics) and show the diminishing influence of "distance to culvert" in explaining species distribution in East Harbor. [ABSTRACT FROM AUTHOR]

Legare, B. and Mace, C., 2017. Mapping and classifying Eastern Oyster ( Crassostrea virginica) habitat in Copano Bay, Texas, by coupling acoustic technologies. The Texas coast is characterized by an extensive array of shallow turbid embayments containing expansive oyster habitats and is home to a large Eastern Oyster ( Crassostrea virginica) fishery. Mapping habitats in shallow (1-10 m), turbid environments is challenging, since direct visual access to the habitats limited. To quantify the extent of habitats, the integration of remote sensing and GIS technologies is used. The Texas Parks and Wildlife Department coupled two acoustic technologies (sidescan sonar and echosounder) to map habitats within Copano Bay, a 181-km2 shallow water embayment along the mid-Texas coast. Data were collected during 17 days from September 2013 to February 2014 and resulted in 159 km2 of sidescan imagery and 375 km of single beam echosounder data. Individual echosounder transmissions were segmented and processed in ArcGIS 10.1 using the 'Unsupervised Classification' tool. Using the classified echosounder data to identify objects located within the sidescan imagery allows for interpolation of habitat using the National Oceanic and Atmospheric Administration's Habitat Digitizer ArcGIS Extension. A total of 25.9 km2 of oyster habitat, 11.6 km2 of shell, 26.4 km2 of sand, and 95.1 km2 of mud were digitized. The resulting habitat map had an overall accuracy of 86% from ground truthing accuracy assessments. This article provides methods for combining sidescan and echosounder acoustic technologies to accurately map habitats in shallow Texas estuaries. [ABSTRACT FROM AUTHOR]

This paper discusses the utility of using seismic-reflection profiling and sediment cores in addition to bottom grab samples and acoustic data to develop shallow-water benthic habitat maps. Currently, the classification system used herein does not provide for the incorporation of stratigraphic data, but we believe that the utility of these maps would improve if such data were included. We conducted vessel-based seafloor-mapping surveys using a phase-measuring sidescan sonar in very shallow waters (mean depth = 3.2 m) covering an area >6.7 km2 in Pleasant Bay in 2014. We collected a total of 192 bottom grab samples to document macro-invertebrates and sediment characteristics. We conducted seismic-reflection profiling surveys to document stratigraphy and determine optimal locations for multiple sediment cores during the 2014 field season; we collected both Kullenberg and Livingstone cores. The seismic-reflection data, though conducted at the reconnaissance scale, proved useful to place the seafloor acoustic data in context. The acoustic and benthic habitat data and mapping products become more valuable when an understanding of the underlying stratigraphy is used as context for the benthic habitat maps. Sediment coring and analysis can provide insights into past and current basin evolution, which can further aid marine natural resource managers. However, we believe that stratigraphic data should be incorporated into standard benthic habitat mapping protocols. These multi-modal datasets provide a better understanding of these habitats for the multidisciplinary teams that typically produce and use these maps as well as coastal managers. [ABSTRACT FROM AUTHOR]