Copepod abundance distribution in relation to a cyclonic eddy in a coastal environment in the southern Gulf of California
Por:
Rocha-Diaz, Franco Antonio, Monreal-Gomez, Maria Adela, Coria-Monter, Erik, Salas-de-Leon, David Alberto, Duran-Campos, Elizabeth, Merino-Ibarra, Martin
Publicada:
1 jun 2021
Resumen:
Marine zooplankton play a pivotal position in the pelagic ecosystem and,
as one of their principal members, copepods represent by far the most
significant direct link between phytoplankton and the higher trophic
levels. In this study, observational evidence of the effect of a
mesoscale cyclonic eddy on the abundance of copepods (adult calanoids,
adult cyclopoids and all copepodite stages) in the Bay of La Paz,
southern Gulf of California, a region recognized as exhibiting high
biodiversity, is presented. During a multidisciplinary research cruise
in February 2006, high-resolution hydrographic profiles were obtained
from a grid of stations throughout the bay, and oblique zooplankton
hauls were made in its north-central portion. The results showed the
presence of a mature mesoscale cyclonic eddy, which extended to 110 m
depth and 30 km diameter, reaching a surface azimuthal velocity of 20 cm
s(-1) at its periphery. Below the mixed layer at 50 m depth this eddy
induced a coldcore water dome (similar to 16.25 degrees C) at its
center. Within this cold water dome, nutrients concentrations were much
higher than outside the eddy. Nitrate reached up to 15 mu M, soluble
reactive phosphorous (SRP) up to 1.6 mu M, and soluble reactive silicate
(SRSi) up to 30 mu M within the eddy. The total abundance of the
organisms analyzed varied according to group: the calanoid copepods
reached values of 8112 ind 100 m(-3), the cyclopoid copepods of 4281 ind
100 m(-3), and the highest abundance was recorded by all copepodite
stages, of 32,076 ind 100 m(-3). The influence of the cyclonic structure
on copepod abundance was to induce the formation of a circular shape
around the eddy periphery, which could be called a `copepod belt shape'.
We suggest that several mechanisms induce this aggregation, including:
1) the affinity of these organisms for waters with a favorable
temperature, and 2) the availability of food (phytoplankton) generated
by the presence of the cyclonic eddy and the sub-mesoscale processes
there, as well as by the presence of a bathymetric sill. These results
represent the first observational report on the influence of a mesoscale
cyclonic eddy in the Bay of La Paz on zooplankton organisms in winter,
which should contribute to a better understanding of the dynamics of
this highly productive area.
Filiaciones:
Posgrado en Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, Av. Universidad 3000, Col. Copilco, Alcaldía Coyoacán, Ciudad de México, 04510, Mexico
Unidad Académica de Ecología y Biodiversidad Acuática, Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, Av. Universidad 3000, Col. Copilco, Alcaldía Coyoacán, Ciudad de México, 04510, Mexico
Unidad Académica Mazatlán, Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, Cap. Joel Montes Camarena, Cerro del Vigía, Mazatlán, Sinaloa CP 82040, Mexico
|