Macroinfauna and meiofauna abundance and diversity following restoration efforts, Barataria Bay, April 2014 - May 2016

Twenty plots (2.1 m x 2.1 m) were established in April 2014 in northern Barataria Bay Louisiana along a saltmarsh shoreline (29.44105oN, -89.93337oW) that was heavily oiled by the Deepwater Horizon oil spill but for which vegetative recovery had not occurred. Five rectangular blocks (~12 m - 30 m) were established within ~3 m of the shore, and treatments were initiated within each block. The two factors considered here were vegetative planting, with or without Spartina alterniflora, and fertilization, with or without slow-release fertilizer. Treatments were (1) unmanipulated (no transplants and no fertilizer) to serve as controls, (2) transplants only, (3) fertilizer only and (4) a combination of transplants and fertilizer. Spartina plants were transplanted at a density of 3-5 stems/plug, spaced 30 cm apart and planted 10 cm deep. Slow-release fertilizer (15% N, 8% P2O5 and 11% K2O) was applied twice a year at a rate of 326 kg N/ha/yr, 76 kg P/ha/yr and 198 kg K/ha/yr. Biological samples were collected at various times after the plots were initiated. Microalgae: A hand-held corer (inner diameter = 1.2 cm) was used to take two sediment cores to a depth of 3 mm within the sampling quadrat. The two cores were combined in a single sample container and immediately frozen on dry ice. Photosynthetic pigments were extracted from entire sediment samples with 4 ml of 100% acetone. High pressure liquid chromatography was used to examine photosynthetic pigment concentration and composition. Chlorophyll a is used here as a proxy for microalgal biomass. Infauna: A hand-held corer was used to take two sediment cores to a depth of 2 cm from each plot. Both cores were combined into a single sample cup and fixed in 4% formalin in the field. Cups were shaken to break up soil clumps and to mix with formalin. In the laboratory, samples were sieved through a 500 µm sieve stacked on top of a 63 µm sieve. All material, including roots, rhizomes and macrofauna, retained on both sieves was preserved for analysis of macroinfauna and meiofauna.