Abstract:
To determine the relative abundances, species number, and composition of macrofauna, all plots were sampled at high tide during the growing season (June and October) in 2015 in the Chandeleur Islands, LA. At each sampling location, water depth was measured and density differences between marsh plants (Spartina shoots) and black mangrove pneumatophores were also quantified. Macrofauna were collected within 1 m of the plant/water interface, which is the area known to harbor high organism abundances in salt marsh systems. We haphazardly tossed three 0.17 m^2 plastic cylinders in each plot, whose lower edge was embedded in the sediment. The contents of the cylinders were collected using a gasoline-powered suction pump and all material was retained in a 0.5 mm mesh collection bag. Following collection, samples were removed from the bag and rinsed over a 0.5 mm sieve to remove any extraneous material, then were placed on ice and frozen. Animals were later identified to the lowest practical taxonomic level. Portunid crabs and penaeid shrimp were measured for total length. Biomass (DW = dry weight, ± 0.0001 g) was determined by drying organisms at 70°C to a constant weight. Samples were then muffled at 500°C to obtain ash weight (AW, ± 0.0001 g). Ash-free dry weight was calculated as DW-AW. Samples were placed in a desiccator to cool before any weights were recorded.
Data Parameters and Units:
Tab 1: Abiotics Date: date samples were collected (2015 only), TOD: time of day that each site was sampled (central time), Site: name assigned to each site at the beginning of the sampling period (Benthic Microbes, Benthic Macroinfauna, Nitrogen Cycling groups use same site names), Oil: the designation of sites as oiled or non-oiled (Yes=Sites A and B; No=C1-S and C2-N), Habitat: habitat type where the suction samples were collected at each site (mangrove, marsh, or mixed), ID: unique identification assigned to each sample item (samplingdate_site_habitat; cross reference between all data tabs), Salinity: salinity recorded mid water column at each site (ppt), Temperature: water temperature recorded mid water column at each site (Celsius), Water depth: recorded within each suction cylinder at each habitat type to estimate tidal height (meters), Dissolved oxygen: dissolved oxygen recorded at mid water column (mg/L); not measured for every site or every sampling event, Latitude (decimal degrees), Longitude (decimal degrees), Notes: any additional comments pertaining to the data collected at each site (character) Tab 2: Raw Abundance Date: date samples were collected (2015 only), Site: name assigned to each site at the beginning of the sampling period (Benthic Microbes, Benthic Macroinfauna, Nitrogen Cycling groups use same site names), Oil: the designation of sites as oiled or non-oiled (Yes=Sites A and B; No=C1-S and C2-N), Suction: replicate number (max=3), Habitat: habitat type where the suction samples were collected at each site (mangrove, marsh, or mixed), ID: unique identifier assigned to each sample item (samplingdate_site_habitat_suctionreplicate; cross reference between all data tabs), Area: the area of the suction sample cylinder (m^2), Amphipoda: number collected in each suction sample replicate, Corophiidae: number collected in each suction sample replicate, Tanaidacea: number collected in each suction sample replicate, Isopoda: number collected in each suction sample replicate, Gastropoda: number collected in each suction sample replicate, Barnacle: number collected in each suction sample replicate, Bivalvia: number collected in each suction sample replicate, Crepidula: number collected in each suction sample replicate, Caridean: number collected in each suction sample replicate, Alpheidae: number collected in each suction sample replicate, Mysidae: number collected in each suction sample replicate, Penaeidae (UNIDED): number collected in each suction sample replicate, Penaeidae (White): number collected in each suction sample replicate, Penaeidae (Brown): number collected in each suction sample replicate, Xanthidae: number collected in each suction sample replicate, Sesarmidae: number collected in each suction sample replicate, Ocypodidae: number collected in each suction sample replicate, Crab megalopae: number collected in each suction sample replicate, Insect larvae: number collected in each suction sample replicate, Chiton: number collected in each suction sample replicate, Portunidae: number collected in each suction sample replicate, Paguroidea: number collected in each suction sample replicate, Gobiidae: number collected in each suction sample replicate, Darter goby: number collected in each suction sample replicate, Naked goby: number collected in each suction sample replicate, Lyre goby: number collected in each suction sample replicate, Sheepshead minnow: number collected in each suction sample replicate, Saltmarsh topminnow: number collected in each suction sample replicate, Rainwater killifish: number collected in each suction sample replicate, Longnose killifish: number collected in each suction sample replicate, Striped mullet: number collected in each suction sample replicate, UNIDED fish: number collected in each suction sample replicate, Total: total number of organisms collected in each suction sample replicate Tab 3: Biomass Pan #: Unique pan number given to each group of organisms (taxonomic group), Project: name of project that funded data collection, ID: unique identifier assigned to each sample item (samplingdate_site_habitat_suctionreplicate; cross reference between all data tabs), Taxonomic Group: species or family name of organism group present in pan, AFDW (g): ash free dry weight for each taxonomic group calculated by subtracting the pan+dry sample weight from the pan+ashed sample weight, AFDW (g m^-2): ash free dry weight for each sample scaled up to density or per m^2 calculated by dividing AFDW (g) by the area sampled (0.17 m^2) Tab 4: Total Length ID: unique identifier assigned to each sample item (samplingdate_site_habitat_suctionreplicate; cross reference between all data tabs), Species: name of species or Family of organisms, Total length: total length (millimeters) recorded for each organism (fish, brown shrimp, white shrimp, blue crab) Tab 5: Plant Density ID: unique identifier assigned to each sample item (samplingdate_site_habitat_suctionreplicate; cross reference between all data tabs), Spartina alterniflora (S. alterniflora): number of shoots/stems present of Spartina alterniflora (smooth cordgrass) within each suction cylinder (sample area) for marsh and mixed habitats, Avicennia germinans (A. germinans): number of pneumatophores present of Avicennia germinans (black mangrove) within each suction cylinder (sample area) for mangrove and mixed habitats, Batis maritima (B. maritima): number of shoots/stems present of Batis maritima (saltwart) within each suction cylinder (sample area) for mangrove, marsh, and mixed habitats, Spartina alterniflora (S. alterniflora) m^-2: number of shoots/stems in terms of density (abundance/0.17 m^2), Avicennia germinans (A. germinans) m^-2: number of pneumatophores in terms of density (abundance/0.17 m^2), Batis martima (B. maritima) m^-2: number of shoots/stems in terms of density (abundance/0.17 m^2)
Methods:
Macrofauna were sampled in mangrove, marsh, and mixed (Spartina/Avicennia) plots at four sampling sites, two oiled and two non-oiled, within the Chandeleur Islands, LA. At each site, three cylinders were haphazardly position approximately 0.5-1 m apart along the shore-water interface to include black mangrove pneumatophores, Spartina alterniflora stems or mixed mangrove and salt marsh habitat (n=9). Before suctioning at a site, water depth was measured as a proxy for tidal inundation stage using a meter stick positioned vertically along the inner edge of each cylinder, and stems and pneumatophores were counted within the sample area to estimate habitat density/complexity. The area within the cylinder was sampled for one minute using a modified gasoline-powered suction pump device (Orth and van Montfrans 1987) and the organisms in the sample were retained in a cod end of 0.5 mm mesh. Once a sample was collected, it was rinsed on a 500-μm sieve to remove fine sediments.
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