Life in the surf-zone: Variations of faunal assemblage structure in temperate sandy beaches of the Southwestern Atlantic coast

FIORI SANDRA; LOPEZ CAZORLA A.C; MARTINEZ A.; CARCEDO C.; BLASINA G.; MOLINA J; GARZÓN CARDONA JOHN EDISON; MOYANO J.S; MENÉNDEZ C.

CONTINENTAL SHELF RESEARCH

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2022

0278-4343

This study explores the changes of biological descriptors -richness, diversity and abundance-of faunal surf-zoneassemblage along a temperate coastal fringe. Three mesotidal sandy beaches with different morphodynamicstates, adjacent to an estuarine zone, were seasonally sampled during a year. Zooplankton, zoobenthos and fishsamples were taken in the surf-zone and a set of potential explanatory environmental variables were measuredand/or quantified. Generalized linear models (GLM) were employed to compare environmental and biologicalvariables between beaches and seasons. Beaches varied from tide-dominated flat to tide-modified reflective tointermediate. The assemblage included 108 taxa, of which few were numerically dominant. Richness of eachbiological group was similar along the shore and higher values of α-diversity were associated with minimumvalues of total abundance. β-diversity was mainly a consequence of species turnover, mostly due to changes inzoobenthic and zooplanktonic taxa. Results of GLM test showed that seasons and beaches have an interdependenteffect on the abundance of the surf-zone assemblage. All biological groups showed marked seasonal variability inits occurrence, possibly associated with environmental variables, such as temperature and photosyntheticpigment concentrations. Zooplankton and fish groups reached maximum abundance, during autumn and springrespectively, in tide-modified beaches where the surf-zone was well developed and waves reached higherheights. Zoobenthic abundance peaked in beaches with narrower surf-zone and lower wave energy, duringautumn, winter and spring, which could be advantageous for those taxa that escape from predators by burying orfor species that actively swim near the seafloor. The copepod Acartia tonsa, the clupeidae fish Ramnogasterarcuata and the mysids Arthromysis magellanica and Neomysis americana all typical species of the neighboringestuary, were the main responsibles for these distribution patterns. The connection of the surf-zone with theadjacent estuarine area is also evident by its role in enriching the dissolved organic matter of surf-waters.