Document Type
Research Data
Publication Date
2015
Keywords
benthic community, sediments, Haverstraw Bay, Hudson River, GIS data
Abstract
High-resolution backscatter and bathymetric maps created by multibeam and sidescan sonar surveys were used to identify five different seafloor bottom types within Haverstraw Bay. Grab samples were collected within these areas to characterize sediment properties and macrofauna. Selected sampling locations were revisited and seafloor images were obtained with an HD underwater camera. Multivariate analysis was used to identify the most important factors explaining variations in community structure. Results indicated that categorical variables defining bottom types, grain size, and water depth can explain about 42% of community structure variation. In addition, shell length data collected for Rangia cuneata, an introduced species, indicated that successful spawning and recruitment occurred for this species during 2011, 2012, and 2013. An attempt to relate 2012-2014 hydrophone location data for Atlantic and Shortnose sturgeon to identified bottom types did not produce clear bottom preferences.
Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.
Recommended Citation
Cerrato, R.M., A.M. Flanagan, R.D. Flood. 2015. Haverstraw Bay Benthic Habitat Characterization. Marine Sciences Research Center Special Report No. 141, Stony Brook University, Stony Brook, NY, 57 pp + GIS
Comments
This .zip file contains ground truth results for the Haverstraw Bay benthic mapping project (Cerrato, R.M., A.M. Flanagan, R.D. Flood. 2015. Haverstraw Bay Benthic Habitat Characterization. Marine Sciences Research Center Special Report No. 141, Stony Brook University, Stony Brook, NY, 57 pp). Sediment and benthic macrofauna were collected to characterize seafloor bottom types. Sampling locations were determined by visual examination of high resolution backscatter and bathymetric maps created by multibeam and side scan sonar surveys.
The principal GIS project file is StationID.mxd in ArcMap and Haverstraw.aprx in ArcGIS Pro. These project files contain groundtruth data layers loaded from a geodatabase called BenthicGrabData.gdb.
The following is a description of the contents of each folder:
1) BenthicGrabData - Contains data files with field, sediment, and faunal summary data in spreadsheet (Excel) format. BenthicGrabData.gdb is an AcgGIS file geodatabase with all of the data loaded as feature classes.
2) Charts - This folder contains a chart of Haverstraw Bay as a raster file.
3) HaverstrawMultiBeam - 300 kHz multibeam backscatter data collected by Roger Flood (SoMAS).
4) Report – contains a copy of Cerrato, R.M., A.M. Flanagan, R.D. Flood. 2015. Haverstraw Bay Benthic Habitat Characterization. Marine Sciences Research Center Special Report No. 141, Stony Brook University, Stony Brook, NY, 57 pp.
5) SedType-SedEnviron – Contains a shoreline shapefile.
6) ShoreTiff – Contains a Haverstraw Bay area raster file.
7) Sidescan - 100 KHz sidescan sonar mosaics for Area B3 collected as part of the Hudson River Mapping Program (R. Bell, W.B.F. Ryan, S.M. Carbotte, F.O. Nitsche, Lamont-Doherty Earth Observatory of Columbia University, NY).
A Brief Summary of Sampling Methods
Sampling Locations
Stratification of the bay into initial bottom type provinces was conducted by visual examination of preliminary 300 kHz multibeam backscatter data collected by Roger Flood (SoMAS) and 100 KHz sidescan sonar mosaics for Area B3 collected as part of the Hudson River Mapping Program (R. Bell, W.B.F. Ryan, S.M. Carbotte, F.O. Nitsche, Lamont-Doherty Earth Observatory of Columbia University, NY). In this process, acoustic backscatter was taken as a proxy for bottom type, and visual examination suggested the presence of six regions or provinces of homogeneous bottom type. These six provinces were arbitrarily assigned a letter code from A-F. Ten grab sampling stations were randomly positioned within each province using the “Create Random Points” tool in ArcGIS 10 (ESRI, Redlands CA), with two exceptions. Province F was small relative to the other bottom types, and only two grab samples were collected within it. Province A was larger than other bottom types, and eleven samples were collected within it. In determining sampling locations, stations within 100 m of a boundary between bottom types or of another station were deleted and replaced by another randomly selected location. The former was to minimize the possibility of inadvertently drifting across a boundary while sampling or sampling in an ecotone or transitional region between provinces. The latter was to maintain independence between sampling stations and to ensure that the sampling results represented the full range of variability within a province.
A subsequent comparison of the grab sampling locations with a more complete, processed version of the 300 kHz backscatter data was carried out after grab samples were collected, but before any data analysis. This visual inspection indicated that several province boundaries required adjusting. These adjustments had several consequences. Stations C03 and C04 were clearly within province A and not province C. While the sample identifiers were not changed, these two samples were assigned to province A for analysis. Several other stations (C02, C05, D07, E05, E06) were located closer (< 100 m) to a boundary than initially planned, and therefore, possibly within an ecotone between bottom types. These stations were included in all analyses anyway, although they may have increased the variability of some of the results.
Fauna and Sediment sampling
Bottom samples for sediments and fauna were collected on October 3-4, 2013 using a modified van Veen grab (0.04 m2). A total of 53 samples were collected. Subsamples of sediments for grain size were drawn from each grab sample. The remaining sediment was washed through a 0.5 mm sieve for fauna. All material left on the sieve was preserved in 10% buffered formalin and stained with rose bengal. Faunal samples were rewashed in the lab and transferred to 70% ethanol before sorting and identification. Individual organisms were identified to species level whenever possible and the total for each taxon enumerated. Unless otherwise noted, all abundances in this report are expressed as the number of individuals per sample (i.e., per 0.04 m2).
Sediment grain size analysis (Folk, R.L. 1964. Petrology of Sedimentary Rocks. Hemphill Pub. Co., Austin, Texas) was used to estimate percent composition by weight of major size-fractions (gravel, sand, silt, clay). Samples were initially partitioned into three size-fractions by adding 50 ml of a 1% Calgon solution to the sample, mixing to disaggregate the particles in the sample, and wet sieving with distilled water through a combination of 2 mm and 63 micron sieves. The >2 mm (gravel) and 2 mm-63 micron (sand) fractions were placed in a drying oven at 60o C for at least 48 hours to obtain dry weights. Water containing the <63 micron fraction (silt-clay or mud) was brought up to 1000 ml total volume by adding distilled water in a graduated cylinder, mixed thoroughly, and subsampled with a 20 ml pipette at a depth of 20 cm, 20 seconds after mixing to obtain an estimate of silt-clay. A clay sample was obtained from a second 20 ml pipette sample collected at a depth of 10 cm, 2 hours and 3 minutes after mixing. Pipette samples were placed in a drying oven at 60o C for at least 48 hours to obtain dry weight estimates of the silt-clay and clay fractions. Weight estimates included a correction for the amount of Calgon introduced to the samples. Silt content was estimated from the difference in weight between the silt-clay and clay fractions.
Bottom images were collected by revisiting at least two sampling locations in provinces A-E on October 10, 2013 and deploying a Seatrex HD (Ocean Systems Inc., Everett WA) industrial grade underwater point of view camera mounted on a tripod. Distance from the camera to the sediment surface had to be decreased to 25 cm because of very high turbidity in the study area, and image size was 14 x 24.5 cm, comparable in size to the dimensions of the modified van Veen grab (20 x 20 cm) used to collect faunal and grain-size samples. For each video, VLC Media Player (VideoLAN, Paris, France) was used to extract a still frame for inclusion.