Recovery of salt marsh benthic microalgae and meiofauna following the Deepwater Horizon oil spill linked to recovery of Spartina alterniflora

We examined the effects of the Deepwater Horizon oil spill on benthic microalgae and meiofauna in Louisiana, USA, salt marshes. Further, we quantified recovery over 4 yr and compared it to recovery of the dominant salt marsh macrophyte Spartina alterniflora. Although impacts were apparent at lightly and moderately oiled sites, negative effects on microalgal biomass and meiofaunal abundance and diversity were strongest in heavily oiled marshes where almost complete mortality of S. alterniflora occurred. However, these metrics, as well as photo synthetic pigment composition and meiofauna community composition, indicated substantial recovery similar to 36 mo post-spill, coincident with recovery of S. alterniflora stem density, even in heavily oiled marshes. Meiofaunal diversity (as measured by copepod species richness) in the earliest stages of recovery was highest where recovering S. alterniflora stems were most dense, and overall, meiofauna recovery was more closely linked to S. alterniflora than to vegetative recovery per se. However, for the polychaete Manayunkia aestuarina, ostracods and kinorhynchs, recovery was still ongoing 4 yr after the spill. These findings suggest that the important ecological services provided in support of food webs by benthic microalgae (a principal basal food resource) and meiofauna (a principal consumer of benthic microalgae and dietary resource to higher trophic levels) largely returned coincident with the recovery of S. alterniflora. S. alterniflora may therefore be a good indicator for the broader recovery of salt marsh infaunal benthos, at least in marshes without accelerated shoreline erosion induced by oiling.