Address biophysical coupling and biogeochemical fluxes is important for us to (1) understand Physical/biological interactions focused on Atlantic/Mediterranean water masses interaction and relation to fish larvae trajectories and accumulation, with focus on bluefin tuna spawning areas and connectivity and MPA design and conservation and (2) study the eddies induced vertical motions relation to phytoplankton size structure and biogeochemical exchanges.
As a first step, to understand the evolution of the physical/biological coupling in Alborán and Balearic sub-basin, we have used a 1D physical-biological model. It is a part of our ongoing efforts for an implementation of an intermediate complexity, well-tested and validated coupled physical-biochemical modeling system for the Western Mediterranean Sea.
In this exploratory study, we bring the available observations together with the findings of one-dimensional version of the model to arrive at a better understanding of the biological characteristics and peculiarities of the region. The related objectives are to come up with an optimum parameter setting for the regional model, and to explore its feasibility for a wide range of contrasting ecological conditions observed in different parts of the South Western Mediterranean Sea. We consider this work as a baseline study for forthcoming three dimensional process-oriented modeling studies.
Abstract:
Controls of plankton production by pelagic fish predation and resource availability in the southwestern Mediterranean Sea
Temel Oguz(1,2); Diego Macias(3); Lionel Renault(1); Javier Ruiz(3); Joaquin Tintoré(1,4)
(1) SOCIB, Balearic Islands Coastal Ocean Observing and Forecasting System, Parc Bit, Naorte, Bloc A, Palma de Mallorca, Spain.
(2) Middle East Technical University, Institute of Marine Sciences, 33731 Erdemli, Mersin, Turkey.
(3) Department of Coastal Ecology and Management, Instituto de Ciencias Marinas de Andalucia (ICMAN-CSIC), Avd. Republica Saharauis/n, CP11510, Puerto Real, Cadiz, Spain.
(4) IMEDEA (CSIC-UIB), Miquel Marquès 21, 07190 Esporles, Spain.
Regional variability of the trophic relationships and food web structure in the Southwestern Mediterranean Sea is evaluated in terms of coupling of the physical environment and primary and secondary productions. The analysis is accomplished by a one-dimensional physical-biochemical model comprising two phytoplankton and zooplankton groups, particulate organic nitrogen, ammonium and nitrate. The study primarily examines the response of regional systems to bottom-up resource supply by the lateral and vertical advective and turbulent nutrient fluxes and top-down control exerted by the predation pressure of planktivorous fish. The model findings suggest an intricate interplay between pelagic fish predation and resource availability to jointly characterize the plankton community structures of different regional systems extending from highly productive upwelling regimes of the northern Balearic and northwestern Alboran Seas to the oligotrophic anticyclonic gyres. In agreement with the observations, a typical annual plankton structure involves a vertically homogeneous biomass of large size groups of phytoplankton and zooplankton within the upper 50-to-100m layer from mid-November to April and a subsurface biomass distributed roughly within 25-75m depths afterwards. Their light and temperature limitations constrain the small size groups mostly into the thermocline zone (25-50 m) during late spring and summer. These results are obtained with the choice of active switching of zooplankton grazing between preys and the Holling Type II (i.e. hyperbolic) grazing function. In the case of no switching of the zooplankton grazing between prey types, the model simulations show spurious dynamical equilibrium solutions for certain range of fish predation rate constant that, for example, involve only the small phytoplankton and mesozooplankton.
