## Taxonomic diversity among oyster reefs in 2015-2016 in previously documented oiled and non-oiled areas in Louisiana, Alabama, and the Florida panhandle

**Authors:**Meagan Schrandt, Sean Powers

**Published On:**Jul 13 2017 21:29 UTC

**DOI:**https://doi.org/10.7266/N75B00GP

**UDI:**R4.x262.213:0001

__Funded By:__

Gulf of Mexico Research Initiative

__Funding Cycle:__

RFP-IV

__Research Group:__

Alabama Center for Ecological Resilience (ACER)

Sean Powers

University of South Alabama / Department of Marine Sciences

spowers@disl.org

2015-09-14 to 2016-04-19

Crassostrea virginica, Deep Water Horizon Oil Spill, Gulf of Mexico Research Initiative, oil, oyster reef, community assemblage, Diversity

**Abstract:**

Abundance of live organisms (per 0.25 m2 quadrat) found in oyster reefs sampled in the early fall (September/October) and spring (April/May) from 2015 to 2016. Four embayments were sampled from Louisiana to the Florida panhandle, with sites that were previously oiled or non-oiled after the Deep Water Horizon Oil Spill. Within oiled and non-oiled sites, oyster quadrat samples were taken from intertidal (along the marsh edge) and subtidal areas, and also from mesohaline and high salinity sites. The top 10 cm of material was collected from the quadrats and returned to the lab for enumeration of species.

**Suggested Citation:**

Meagan Schrandt, Sean Powers. 2017. Taxonomic diversity among oyster reefs in 2015-2016 in previously documented oiled and non-oiled areas in Louisiana, Alabama, and the Florida panhandle. Distributed by: Gulf of Mexico Research Initiative Information and Data Cooperative (GRIIDC), Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N75B00GP

**Purpose:**

The purpose of this dataset is to describe the condition of oyster reef communities in areas with documented exposure to oil from the Deepwater Horizon Oil Spill in 2010, as well as control sites (no documented oil exposure). This field sampling, and the associated genetic analyses resulting from field collection of oysters, will help determine the recovery trajectories in genetic, taxonomic, and functional diversity of oyster reefs in the northern Gulf of Mexico, arising from oiling and response activities (e.g., freshwater diversions, dispersants).

**Data Parameters and Units:**

Year = the year of sampling Mo = the calendar month of sampling Day = the calendar day of sampling for any given month Time_CST = the time the oyster reef site was sampled; in Central Standard Time Site = the ID given to the sampled site; the first two letter correspond to the embayment Embayment = the generic sampling embayment where the reef can be found; options (4) include: Mississippi Sound, Barataria Bay, Terrebonne Bay, Florida Basin = location of the oyster reef within the generic sampling embayment: options (26) include: Airport Marsh; Alabama Port; Apalachicola Bay; Barataria Bay, east; Barataria Bay, north; Bay Junop, north; Bay Junop, south; Caillou Lake, north; Coffee Island; Dauphin Island; Dauphin Island Bay; DI Shoals, northwest; East Bay Panama City; East Bay Pensacola; Escambia Bay, Pensacola; Grand Isle; Grand Terre; Hackberry Bay; Heron Bay; Little Dauphin Island; North Bay Panama City; Pensacola Bay, west; Portersville Bay; Terrebonne Bay, north; Terrebonne Bay, west; West Bay Panama City State = the US state where the oyster reef site is located; options (3) include: Louisiana, Alabama, Florida Lat = latitude of oyster reef site (WGS1984) (decimal degrees) Long = longitude of oyster reef site (WGS1984) (decimal degrees) Near_Sub = the tidal regime for the site; options (2) include: nearshore (intertidal, along the marsh edge) and subtidal OilingCat = the oiling category assigned to the site; based on categories assigned by the Natural Resource Damage Assessment and Shoreline Cleanup and Assessment Technique (SCAT) maps for non-NRDA sites; categories (2) include: oiled, not oiled SalinityCat = the salinity group assigned to the oyster site, based on the measurement of salinity taken at the time of sampling in 2015; options (2) include meso and high. For Barataria and Terrebonne Bays, high salinity is considered greater than or equal to 19 ppt. For Mississippi Sound, high salinity is considered to be greater than or equal to 21 ppt. The difference in values is based on the differing salinity regimes in each embayment. WaterTemp_C = water temperature just above the reef at the time of sampling; units are degrees Centigrade Salinity_ppt = salinity just above the reef at the time of sampling; units are ppt (parts per thousand) DO_mgL = dissolved oxygen just above the reef at the time of sampling; reading was taken as close to the oyster reef as possible (surface for intertidal and just above the reef for subtidal reefs); units are mg per L QuadratRep = the quadrat number at the site; a total of 3 quadrats were sampled at each oyster reef site; options (3) include: Q1, Q2, Q3 SampleID = the ID for the quadrat sample taken at the oyster reef; this ID has the format Site-QuadratRep; for example: MS01-Q1 is quadrat 1 from oyster reef number 01 in Mississippi Sound BagMass_kg = the mass of the oyster reef sample collected and placed in a small-mesh bag; bags were measured with a spring scale at the laboratory and the units are kg ProcessTime_CST = the time the oyster reef sample was removed from the collection bag and placed on the table to begin enumerating species and measuring oyster shell heights. This time is typically later in the day on the same day of collection, unless processing extended past midnight. Time is recorded in Central Standard Time *The remaining columns are counts of taxa (species, families, etc). Each is in a group of 3 – each species has one column for the number of that species counted, one column for the multiplier (in case the quadrat was sub-sampled), and the third column is the product of the first times the second and gives the density of each particular species within the 0.25 m-squared quadrat. OysterSpat_Num = the number of live oyster spat counted in the 0.25 m-squared quadrat sample. Oyster spat is defined as oysters with shell heights less than or equal to 25 mm. OysterSpat_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. OysterSpat_Per0.25m2 = density of spat-sized oysters in 0.25 m-squared quadrat OysterSeed_Num = the number of live oyster seed counted in the 0.25 m-squared quadrat sample. Oyster seed is defined as oysters with shell heights greater than 25 mm and less than 75 mm. OysterSeed_Mult = *Can copy from any column ending in “Mult”* the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. OysterSeed_Per0.25m2 = density of seed-sized oysters in 0.25 m-squared quadrat OysterMarket_Num = the number of live market-sized oysters counted in the 0.25 m-squared quadrat sample. Market oysters are those with shell heights great than or equal to 75 mm. OysterMarket_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. OysterMarket_Per0.25m2 = density of market-sized oysters in 0.25 m-squared quadrat OysterPiddock_Num = the number of live oyster piddocks counted in the 0.25 m-squared quadrat OysterPiddock_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. OysterPiddock_Per0.25m2 = density of oyster piddocks in 0.25 m-squared quadrat Ischadium_Num = the number of live Ischadium mussels counted in the 0.25 m-squared quadrat Ischadium_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. Ischadium_Per0.25m2 = density of Ischadium mussels in 0.25 m-squared quadrat Mytilopsis_Num = the number of live Mytilopsis mussels counted in the 0.25 m-squared quadrat Mytilopsis_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. Mytilopsis_Per0.25m2 = density of Mytilopsis mussels in 0.25 m-squared quadrat PaperMussel_Num = the number of live paper mussels counted in the 0.25 m-squared quadrat PaperMussel_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. PaperMussel_Per0.25m2 = density of paper mussels in 0.25 m-squared quadrat PandoraTrilineata_Num = the number of live Pandora Trilineata counted in the 0.25 m-squared quadrat PandoraTrilineata_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. PandoraTrilineata_Per0.25m2 = density of Pandora Trilineata in 0.25 m-squared quadrat Geukensia_Num = the number of live Geukensia mussels counted in the 0.25 m-squared quadrat Geukensia_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. Geukensia_Per0.25m2 = density of Geukensia mussels in 0.25 m-squared quadrat MercenariaClam_Num = the number of live Mercenaria clams counted in the 0.25 m-squared quadrat MercenariaClam_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. MercenariaClam_Per0.25m2 = density of Mercenaria clams in 0.25 m-squared quadrat SurfClam_Num = the number of live surf clams counted in the 0.25 m-squared quadrat SurfClam_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. SurfClam_Per0.25m2 = density of surf clams in 0.25 m-squared quadrat CrossBarredVenusClam_Num = the number of cross barred venus clams counted in the 0.25 m-squared quadrat CrossBarredVenusClam_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. CrossBarredVenusClam_Per0.25m2 = density of cross barred venus clams in 0.25 m-squared quadrat SemelidaeClam_Num = the number of Semelidae clams counted in the 0.25 m-squared quadrat SemelidaeClam_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. SemelidaeClam_Per0.25m2 = density of Semelidae clams in 0.25 m-squared quadrat AbraAequalisClam_Num = the number of Abra Aequalis clams counted in the 0.25 m-squared quadrat AbraAequalisClam_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. AbraAequalisClam_Per0.25m2 = density of Abra Aequalis clams in 0.25 m-squared quadrat TellinClam_Num = the number of Tellin clams counted in the 0.25 m-squared quadrat TellinClam_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. TellinClam_Per0.25m2 = density of Tellin clams in 0.25 m-squared quadrat ArkClam_Num = the number of Ark clams counted in the 0.25 m-squared quadrat ArkClam_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. ArkClam_Per0.25m2 = density of Ark clams in 0.25 m-squared quadrat OysterDrill_Num = the number of live oyster drills counted in the 0.25 m-squared quadrat OysterDrill_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. OysterDrill_Per0.25m2 = density of oyster drills in 0.25 m-squared quadrat Crepidula_Num = the number of live Crepidula counted in the 0.25 m-squared quadrat Crepidula_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. Crepidula_Per0.25m2 = density of Crepidula in 0.25 m-squared quadrat OliveNerite_Num = the number of live olive nerite snails counted in the 0.25 m-squared quadrat OliveNerite_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. OliveNerite_Per0.25m2 = density of olive nerites in 0.25 m-squared quadrat Littorina_Num = the number of live Littorina snails counted in the 0.25 m-squared quadrat Littorina_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. Littorina_Per0.25m2 = density of Littorina snails in 0.25 m-squared quadrat PlicateMangelinaSnail_Num = the number of live Plicate Mangelina snails counted in the 0.25 m-squared quadrat PlicateMangelinaSnail_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. PlicateMangelinaSnail_Per0.25m2 = density of Plicate Mangelina snails in 0.25 m-squared quadrat CommonEasternNassa_Num = the number of live Common Eastern Nassa snails counted in the 0.25 m-squared quadrat CommonEasternNassa_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. CommonEasternNassa_Per0.25m2 = density of Common Eastern Nassa snails in 0.25 m-squared quadrat SnailOther_Num = the number of live unidentified snails counted in the 0.25 m-squared quadrat SnailOther_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. SnailOther_Per0.25m2 = density of other snails in 0.25 m-squared quadrat Xanthidae_Num = the number of live Xanthidae crabs counted in the 0.25 m-squared quadrat Xanthidae_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. Xanthidae_Per0.25m2 = density of Xanthidae in 0.25 m-squared quadrat BlueCrab_Num = the number of live blue crabs (Callinectes sapidus) counted in the 0.25 m-squared quadrat BlueCrab_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. BlueCrab_Per0.25m2 = density of blue crabs in 0.25 m-squared quadrat Porcellanidae_Num = the number of live porcelain crabs counted in the 0.25 m-squared quadrat Porcellanidae_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. Porcellanidae_Per0.25m2 = density of porcelain crabs in 0.25 m-squared quadrat HermitCrab_Num = the number of live hermit crabs counted in the 0.25 m-squared quadrat HermitCrab_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. HermitCrab_Per0.25m2 = density of hermit crabs in 0.25 m-squared quadrat PenaeidShrimp_Num = the number of live Penaeid shrimp counted in the 0.25 m-squared quadrat PenaeidShrimp_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. PenaeidShrimp_Per0.25m2 = density of Penaeid shrimp in 0.25 m-squared quadrat SnappingShrimp_Num = the number of live snapping shrimp counted in the 0.25 m-squared quadrat SnappingShrimp_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. SnappingShrimp_Per0.25m2 = density of snapping shrimp in 0.25 m-squared quadrat Amphipod_Num = the number of live amphipods counted in the 0.25 m-squared quadrat Amphipod_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. Amphipod_Per0.25m2 = density of amphipods in 0.25 m-squared quadrat Isopod_Num = the number of live presumed isopods counted in the 0.25 m-squared quadrat Isopod_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. Isopod_Per0.25m2 = density of presumed isopods in 0.25 m-squared quadrat Barnacle_Num = the number of live barnacles counted in the 0.25 m-squared quadrat Barnacle_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. Barnacle_Per0.25m2 = density of barnacles in 0.25 m-squared quadrat Blennidae_Num = the number of live Blennidae fish counted in the 0.25 m-squared quadrat Blennidae_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. Blennidae_Per0.25m2 = density of blennies in 0.25 m-squared quadrat LongnoseKillifish_Num = the number of live longnose killifish counted in the 0.25 m-squared quadrat LongnoseKillifish_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. LongnoseKillifish_Per0.25m2 = density of longnose killifish in 0.25 m-squared quadrat DarterGoby_Num = the number of live darter gobies counted in the 0.25 m-squared quadrat DarterGoby_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. DarterGoby_Per0.25m2 = density of darter gobies in 0.25 m-squared quadrat NakedGoby_Num = the number of live naked gobies counted in the 0.25 m-squared quadrat NakedGoby_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. NakedGoby_Per0.25m2 = density of naked gobies in 0.25 m-squared quadrat CodeGoby_Num = the number of live code gobies counted in the 0.25 m-squared quadrat CodeGoby_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. CodeGoby_Per0.25m2 = density of code gobies in 0.25 m-squared quadrat GobyNotID_Num = the number of live gobies not identified to species counted in the 0.25 m-squared quadrat GobyNotID_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. GobyNotID_Per0.25m2 = density of gobies not identified to species in 0.25 m-squared quadrat Skilletfish_Num = the number of live skilletfish counted in the 0.25 m-squared quadrat Skilletfish_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. Skilletfish_Per0.25m2 = density of skilletfish in 0.25 m-squared quadrat Polychaeta_Num = the number of live polychaete worm heads counted in the 0.25 m-squared quadrat Polychaeta_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. Polychaeta_Per0.25m2 = density of polychaetes in 0.25 m-squared quadrat Serpulidae_Num = the number of Serpulid worm tubes counted in the 0.25 m-squared quadrat Serpulidae_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. Serpulidae_Per0.25m2 = density of Serpulid worm tubes in 0.25 m-squared quadrat WormOther_Num = the number of non-polychaete nor Serpulidae worms counted in the 0.25 m-squared quadrat WormOther_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. WormOther_Per0.25m2 = density of other worms in 0.25 m-squared quadrat BrittleStar_Num = the number of live brittle stars counted in the 0.25 m-squared quadrat BritStar_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. BrittleStar_Per0.25m2 = density of brittle stars in 0.25 m-squared quadrat Nudibranch?_Num = the number of live presumed nudibranchs counted in the 0.25 m-squared quadrat Nudibranch?_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. Nudibranch?_Per0.25m2 = density of presumed nudibranchs in 0.25 m-squared quadrat Tunicate_Num = the number of live tunicates counted in the 0.25 m-squared quadrat Tunicate_Mult = the multiplier assigned in case the 0.25 m-squared sample was so large that it was sub-sampled. Options (2) include: 1 or 4. 1 means the taxa was counted in the entire 0.25 m-squared quadrat sample; 4 means that the 0.25 m-squared quadrat was divided into 4ths for processing and the previous column will need to be multiplied by 4 in order to calculate a density per 0.25 m-squared area. Tunicate_Per0.25m2 = density of tunicates in 0.25 m-squared quadrat YellowBoringSponge = this column indicates whether the yellow boring sponge was present on any of the oyster shells in the quadat sample. Options (2) include: Present, Absent Bryozoan = this column indicates whether bryozoans were present on any of the oyster shells in the quadat sample. Options (2) include: Present, Absent

**Methods:**

Four embayments were sampled from Louisiana to the Florida panhandle, with sites that were previously oiled or non-oiled after the Deep Water Horizon Oil Spill. Within oiled and non-oiled sites, oyster quadrat samples were taken from intertidal (along the marsh edge) and subtidal areas, and also from mesohaline and high salinity sites. The top 10 cm of material was collected from the quadrats and returned to the lab for enumeration of species.