Ground-truthing images, 2014-2015, Gateway National Recreation Area

Collection of benthic infauna and epifauna used a 0.04 m2 Ted Young Modified Van Veen grab. Three replicate benthic samples were collected at 23 sites to total 69 samples in Year 1. The samples were immediately sieved over a 0.5 mm mesh screen. The residue remaining on the screen was fixed in 3.7% formaldehyde solution in seawater, buffered with sodium borate and containing Rose Bengal to stain organisms. A fourth grab was collected for sediment analysis. Sediment for grain size analysis was wet-sieved through a 63μm-mesh sieve in distilled water with dispersant to disaggregate and separate the silt and clay fraction from the sand-sized fraction. Silt and clay mass was determined by drying a known volume of the water-particle mixture passing through the sieve. The sand fraction was dried and then sieved into the following size fractions: <63 µm (silt), 63-125 µm (very fine sand), 125-250 µm (fine sand), 250-500 µm (medium sand), 500-1000 µm (coarse sand), >1000 µm (very coarse sand). Each fraction was weighed. The mass of the <4φ fraction was further analyzed using a Spectrex model PC-2000 laser particle counter (Spectrex Corporation, Redwood City, CA) Counts of particles were obtained corresponding to these additional size categories: 5φ (4-8 µm very fine silt), and 6φ (16-31 µm, medium silt), 7φ (8-16 µm, fine silt), 8 φ ( 4-8 µm, very fine silt), and 9 φ (2-4 µm, clay). Particle counts were converted to mass by multiplying the fractional volume percent in each size category by the total mass of the <4φ fraction determined during wet sieving.

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