P. Felisberto, pfelis(at)ualg.pt
O.C. Rodriguez, orodrig(at)ualg.pt
J.P. Silva, joaoparentessilva(at)gmail.com
S.M. Jesus sjesus(at)ualg.pt
LARSys, University of Algarve, Campus de Gambelas, PT-8005-139 Faro, Portugal.
H. Quental-Ferreira hferreira(at)ipma.pt
P. Pousão-Ferreira pedro.pousao(at)ipma.pt
M.E. Cunha micunha(at)ipma.pt
IPMA - Instituto Português do Mar e da Atmosfera, EPPO, Av. 5 de Outubro, 8700-305 Olhão, Portugal
C.B. de los Santos cbsantos(at)ualg.pt
I. Olivé iosamarra(at)ualg.pt
and
R. Santos rosantos(at)ualg.pt
Marine Plant Ecology research group, Center of Marine Sciences of University of Algarve,
Campus de Gambelas, 8005-139 Faro, Portugal
Comments: download pdf.
Ref.: 173rd Meeting of the ASA, Boston, MA, USA, June
2017.
Abstract
Under high irradiance, the photosynthetic activity of dense seagrass meadows saturates the
water forming oxygen bubbles. The diel cycle of bubble production peaks at mid-day, following
light intensity pattern. It is well known that bubbles strongly affect the acoustic propagation,
increasing signal attenuation and decreasing the effective water sound speed, noticeable at low
frequencies. Thus, the diurnal variability of bubbles may show an interference pattern in the
spectrograms of low frequency acoustic signals. In an experiment conducted in July 2016 at
the Aquaculture Research Station of the Portuguese Institute for the Sea and Atmosphere in Olhão,
Portugal, the spectrograms of low frequency (<20kHz) broadband noise produced by water pumps in
a pond of 0.48ha covered by the seagrass Cymodocea nodosa showed interference patterns that can
be ascribed to the variability of the sound speed in the water. Preliminary analysis suggests that
the daily cycle of bubble concentration can be inferred from these interference patterns.