FRESSHWATER MEDIATES TOP-DOWN CONTROL OVER SPECIES RANGE LIMITS AND INVASIBILITY IN A MARINE PLANT COMMUNITY

LUCAS M. MOLINA.; LEON NICOLAS; DANIEL BARRIO

Mar del Plata

Congreso; XVIII Congreso Latino-Americano de Ciencias del Mar -XVIIICOLACMAR-; 2019

INIDEP- UNMdP

The saltmarshes are environments exposed to aquatic and terrestrial conditions (both marine and freshwater) and have marked gradients of physical stress (eg anoxia, salinity) that have important effects on the structure and, in particular, zonation of communities. Particularly in the marshes located in estuaries, quantity, quality and temporal variation of freshwater inflows are essential to the abiotic and biotic components. Much of the large spatial and temporal variations of physical, chemical and biological conditions in estuaries occur due to seasonal and interannual variability in freshwater inputs. The objective of this study was to investigate the role of freshwater input variation and herbivory on species range limits, invasion and competitive dominance in Spartina species (Spartina alterniflora and S. densiflora). We tested the hypothesis that plant zonation and growth of Spartina are mediated by crabs and drought stress (water availability) with a fully factorial experiment, that was conducted from September 2017 to april 2019. Forty plots (50x50 cm) with 50% S. alterniflora and 50% of S. densiflora were delimited (in two marshes on both sides of Negro River). The following treatments will be applied randomly (N=8): Control, Crab exclusion (50x50 x75 cm cages buried in the sediments); water (water addition); water + crab exclusions; and Cage Controls (half cages). The results of this work indicates that S. alterniflora dominates plots with water addition treatments, with and without crabs. Predation in S. densiflora was higher in treatment with freshwater addition. Our study reveals that an increase in fresh water input will promote sediment stabilization through the effect of S. alterniflora roots in sediment compaction.