title: Natural dissolved humic substances increase the lifespan and promote transgenerational resistance to salt stress in the cladoceran Moina macrocopa.
abstract: OBJECTIVE
  Evidence has accumulated that humic substances (HS) are not inert biogeochemicals. Rather, they cause stress symptoms and may modulate the life history of aquatic organisms. Nevertheless, it is still not clear how HS interact with additional stressors and if their effects are transgenerational. We tested the interactive effects of HS and salt to cladocerans, discussing their consequences for the persistence in fluctuating environments, such as coastal lagoons.
  
  
  METHODS
  We used life-table experiments to test the effects of natural HS from a polyhumic coastal lagoon (0, 5, 10, 20, 50, and 100 mg dissolved organic carbon (DOC) L(-1)) on the life-history of the cladoceran Moina macrocopa. We further tested the effects of HS (10 mg DOC L(-1)), within and across generations, on the resistance of M. macrocopa to salt stress (5.5 g L(-1)).
  
  
  RESULTS
  HS at 5-20 mg DOC L(-1) extended the mean lifespan of M. macrocopa by ~30%. HS also increased body length at maturity by ~4% at 5-50 mg DOC L(-1) and stimulated male offspring production at all tested concentrations. Exposure to HS (even maternal only) alleviated the salt-induced reduction of somatic growth. Co-exposure to HS increased body volume by 12-22% relative to salt-only treatments, while pre-exposure to HS increased body volume by 40-56% in treatments with salt presence, when compared to non-pre-exposed animals.
  
  
  CONCLUSIONS
  HS at environmentally realistic concentrations, by acting as mild chemical stressors, modify crucial life-history traits of M. macrocopa, favoring its persistence in fluctuating environments. Some of the effects of HS are even transgenerational.
authors.affiliation: Laboratório de Limnologia, Departamento de Ecologia, Universidade Federal do Rio de Janeiro (UFRJ), Ilha do Fundão, CEP 21941-590, PO Box 68020, Rio de Janeiro, Rio de Janeiro, Brazil. suhett@gmail.com
authors.forename: Albert L
authors.initials: AL
authors.lastname: Suhett
authors.forename: Christian E W
authors.initials: CE
authors.lastname: Steinberg
authors.forename: Jayme M
authors.initials: JM
authors.lastname: Santangelo
authors.forename: Reinaldo L
authors.initials: RL
authors.lastname: Bozelli
authors.forename: Vinicius F
authors.initials: VF
authors.lastname: Farjalla
mesh_terms: D000818:Animals; D002244:Carbon / Q000032:analysis; D033361:Cladocera / Q000187:drug effects* / Q000254:growth & development*; D005260:Female; D006812:Humic Substances / Q000032:analysis*; D008136:Longevity; D008297:Male; D023421:Models, Animal; D010641:Phenotype; D012492:Salts; D013312:Stress, Physiological
chemical_list: D006812:Humic Substances; D012492:Salts; D002244:Carbon