Abstract:
Snails, oysters, and mussels were collected in three south Louisiana saltmarshes (Terrebonne Bay, Grand Isle, Port Sulphur) from 2013-04-04 to 2016-04-28. In addition to abundances, an assortment of physical measurements were taken for each mollusk species. Plant coverage and sediment characteristics within each collection quadrat is also reported here for samples collected in 2014-2016. Note that 2013 data from these sites are available under GRIIDC Unique Dataset Identifiers (UDIs) R1.x139.144:0021 (mollusk abundances), R1.x139.144:0022 (sediment properties), and R1.x139.144:0023 (plant cover). Invertebrate measurements (not originally conducted on the 2013 samples) were done later and is included in this dataset.
Suggested Citation:
Robinson, Elizabeth, Rabalais, Nancy N.. 2019. Plant cover, sediment properties, mollusk abundance and morphology from three Louisiana saltmarshes, 2013-04-04 to 2016-04-28. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/n7-q7hb-7d87
Data Parameters and Units:
Worksheet - Site Information: Site: User-defined identifier assigned to the sampling sites, Treatment: User-defined classification of the site at the beginning of the project, in regards to possible Macondo oil exposure (unoiled or oiled). LAT (decimal degrees): Latitude of the transect in the sampling area in decimal degrees, LONG (decimal degrees): Longitude of the transect in the sampling area in decimal degrees, Parameters collected: A summary of the variables collected at each site.
Worksheet - Environmental Data: Site: User-defined identifier assigned to the sampling sites, Transect: Identifier for three individual transects established within each study site, Plot: Plot number assigned based on two sampling distances from the marsh edge (1 m or 10 m from the marsh edge), Season: Season of the year that sampling was conducted. Date Collected: Date the sample was collected in the field (MM/DD/YYYY). Treatment: User-defined classification of the site at the beginning of the project, in regards to possible Macondo oil exposure (unoiled or oiled). Clay (%): percent clay in the sediment, Silt (%): percent silt in the sediment, Sand (%): percent sand in the sediment, Plant Cover (%): plant cover of sampling plot, Sediment Water Content (%): percent water content in the sediment, Sediment Organic Matter (%): percent organic matter in the sediment.
Worksheet - Invertebrate Counts: Site: User-defined identifier assigned to the sampling sites, Transect: Identifier for three individual transects established within each study site, Plot: Plot number assigned based on two sampling distances from the marsh edge (1 m or 10 m from the marsh edge), Season: Season of the year that sampling was conducted. Date Collected: Date the sample was collected in the field (MM/DD/YYYY). Treatment: User-defined classification of the site at the beginning of the project, in regards to possible Macondo oil exposure (unoiled or oiled). Littoraria: mollusk counts for Littoraria irrorata (periwinkle snails), Geukensia: mollusk counts for Geukensia demissa (ribbed mussels), Crassostrea: mollusk counts for Crassostrea virginica (oysters), Neritina: mollusk counts for Neritina usnea (olive nerite snails), Melampus: mollusk counts for Melampus bidentatus (common marsh snails).
Worksheet - Invertebrate Measurements: Site: User-defined identifier assigned to the sampling sites, Transect: Identifier for three individual transects established within each study site, Plot: Plot number assigned based on two sampling distances from the marsh edge (1 m or 10 m from the marsh edge), Season: Season of the year that sampling was conducted. Date Collected: Date the sample was collected in the field. Treatment: User-defined classification of the site at the beginning of the project, in regards to possible Macondo oil exposure (unoiled or oiled). Species: Species of individual being measured (L=Littoraria irrorata, M=Geukensia demissa, V=Crassostrea virginica, O=Neritina usnea, C = Melampus bidentatus), Total whole wet weight (g): total weight in grams of the shell and tissue prior to any drying or measurements. Shell length (mm): Snails=measurement from shell apex to shell aperture, Bivalves=measurement from dorsal (umbro) to ventral (bill) sides of the shell. Aperture length (mm): measurement only for snails, the vertical measurement of the aperture, Aperture width (mm): measurement only for snails, the horizontal measurement of the aperture, Lip thickness (mm): measurement only for snails, the thickness of the aperture lip, Body whorl (mm): snails=height of the body whorl, bivalves=height of the shell between the left and right valves, Tissue wet weight (g): weight of tissue before drying in a drying oven, Tissue dry weight (g): weight of tissue after drying in a drying oven, Shell dry weight (g): weight of shell after air drying, Compression force 1 (N): compression force required to break the shell of a snail or one valve of a bivalve, Compression force 2 (N): compression force required to break the second valve of a bivalve if available.
Methods:
Snails, oysters, and mussels were collected at six field sites within Terrebonne Bay (note: only four sites in 2013; TB5 and TB6 were established in 2014), five sites around Grand Isle, and four sites in the Port Sulphur area. Organisms were collected using 0.5 x 0.5 m (0.25 m2) quadrats placed 1 and 10 m from the marsh edge at three transects perpendicular to the shore, in oiled-unoiled pairs per region. Plant coverage was determined within each quadrat. Sediment percent water content and organic matter were calculated from wet weight, dry weight, and ash-free weights of sediment samples. Sediment grain size analysis was completed on sediment samples using a laser particle counter. An assortment of physical measurements using calipers were taken for each mollusk species. Compression strength of mollusk shells was completed using a Shimpo digital gauge with a chisel tip.
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