Elsevier

Progress in Oceanography

Volume 74, Issues 2–3, August–September 2007, Pages 397-421
Progress in Oceanography

Mesozooplankton in the Canary Current System: The coastal–ocean transition zone

https://doi.org/10.1016/j.pocean.2007.04.010Get rights and content

Abstract

The Canary Current System (CCS) is one of the largest upwelling areas of the world. Understanding the biogeochemical fluxes and recruitment of fish in relation to changes in climate requires knowledge of the factors influencing mesozooplankton biomass and fluxes. Here, the trophic and metabolic characteristics of mesozooplankton for the oceanic, upwelling and eddy system of the CCS are reviewed. Mesoscale phenomena are of importance in this region as besides upwelling filaments, the eddy system shed from the Canary Islands is unique in comparison with other similar systems such as the Humboldt, California and Benguela. The coupling of production in the coastal area off Northwest Africa with the oceanic zone through filaments and eddies topographically formed in the coast or shed by the islands promotes a continuous transport of organic matter towards the deep ocean. Zooplankton follow the signal of the mesoscale phenomena and are good tracers of advection. The different species, which can be used as targets in the area, are also described from the upwelling region to the open ocean. However, not all the variability in the area is explained by bottom-up controls. The effect of diel vertical migrants feeding on epipelagic zooplankton shows that top-down controls are also important to understanding the structure and fluxes in this oceanic environment.

Introduction

The Canary Current System (CCS) is one of the 49 Large Marine Ecosystems of the world (Sherman, 1993). These are wide geographic regions generally larger than 200,000 km2 characterized by their bathymetry, hydrography and productivity and supporting marine populations which have adapted their feeding, reproductive and growth strategies (Sherman and Alexander, 1989). The CCS is one of the largest upwelling areas of the world and therefore supports important fisheries. However, it is important to distinguish between the North Atlantic subtropical gyre and the eastern coastal biome (Longhurst, 1998). In this work, we will consider this wide geographic area as a system with two clear sides, the oceanic (oligotrophic) waters and the coastal upwelling region. Connections between both areas are one of the most prominent features of the region in comparison with other upwelling areas. The presence of the Canarian Archipelago as a barrier of more than 600 km (Fig. 1) in the path of the Canary current and the consequent mesoscale activity generated promotes a rather different functioning of the system in comparison with similar ecosystems.

During the last two decades, knowledge of the CCS has changed due to the increase in the research effort performed by laboratories working in the region. Most of the research in the past was done by mainland European institutions. During the 1970s, the CINECA program (Cooperative Investigation of the Northern part of the East Central Atlantic) promoted an extraordinary advance in the knowledge of the area (Hempel, 1982). Recently, the European projects “Coastal Transition Zone: Islas Canarias” and “Canary Azores Gibraltar Observations” (CANIGO) added valuable information about the functioning of the exchanges between the coastal zone and the open ocean. One of the key advances in the area was the study of mesoscale phenomena, such as upwelling filaments and eddies shed by the Canary Islands. Remote sensing methods provided an important tool for the study of such structures. The enormous and complex mesoscale variability related with the cyclonic and anticyclonic eddies shed by the islands as well as the upwelling filaments which flow into the open ocean, have prompted a reappraisal of the role of ocean physics (and therefore climate) in the development of marine communities (Bakun, 1998). However, although the growth of populations is intimately related to the effect of physics (upwelling, vertical mixing, etc.) not all the biological variability can be explained by climatic phenomena. Ecosystem structure depends also on strict biological factors. Grazing and predation promote drastic changes in the composition and development of marine populations. In particular, predation has enormous implications in the structure of marine ecosystems, and the oceanic realm is no exception (Verity and Smetacek, 1996).

Zooplankton plays a central role in the food web as a link between the microbial food web and the larger organisms such as small pelagic fishes. Fish larvae feed on phyto- and zooplankton and their biomass and abundance is crucial for the development of their populations. In upwelling areas there is also a relationship between fish and zooplankton of different sizes (Cushing, 1978). Anchovies and sardines feed on copepods and jack mackerel feed on copepods as well as on euphausiids.

In the present work, the mesozooplankton and related components of the food web will be reviewed in the Coastal–Ocean Transition Zone of the Canary Current System. Emphasis will be placed on describing the planktonic components of the web, their variability and factors influencing mesozooplankton development in the oceanic area of the CCS, the upwelling and the effects of the Canary Islands in the path of the main current. These areas and their mesoscale structures will be reviewed beginning in each section with a description of the physical phenomenon, primary productivity and then zooplankton in terms of biomass and taxonomic composition. Copepods, as the main mesozooplankton organisms will be the focus of the review. Top-down effects by predators inhabiting the deep scattering layers will be also reviewed as not all the variability in zooplankton biomass and abundance is driven by physics.

Section snippets

The oceanic area of the Canary Current System

The Canary current is the easternmost branch of the North Atlantic Subtropical Gyre flowing southward. It is a relatively cold current in relation to its latitude due to cooling of the waters of the subtropical gyre during its flow through the westerly winds province at the latitude of the Azores Islands. Temperature at the surface varies from 18 to 23 °C, although off the African coast values can reach only 16 °C (Mittelstaedt, 1991). Salinity varies between 36 and 37 psu. Below the mixed layer

The upwelling system

The upwelling area off Northwest Africa extends from about 15 to 33°N covering a large area of the African coast. However, the upwelling is not continuous and homogeneous along this coast and different spots of strong upwelling are usually observed coinciding with topographic features such as capes as observed from remote sensing (Van Camp et al., 1991). The deep water in the upwelling area circulates through the continental shelf and reaches the surface at the coast where the lowest

The island effect

Plankton biomass increases near islands (Doty and Oguri, 1956). These enhancements are due to the physical perturbations generated by these physical barriers in the path of the oceanic flow. This enrichment is of importance for upper trophic levels as small and medium pelagic fish, which feed on the primary and secondary productivity, are prey for large species such as tuna (Blackburn, 1965, Sund et al., 1981). The presence of the Canary Islands distinguishes the Canary Current System from

Deep scattering layers control on epipelagic zooplankton

An important component of the pelagic fauna, unfortunately scarcely studied, are the organisms inhabiting the deep scattering layers (DSLs). In the Canary current this layer is located between 400 and 600 m depth almost permanently (Boden and Kampa, 1967). A portion of these organisms are interzonal diel vertical migrants (DVMs). Boden and Kampa, 1967, Blaxter and Currie, 1967 observed sharp DSLs to the south of Fuerteventura Island and found that DVMs follow the isolume. They showed that

Summary

The trophic scenario of mesozooplankton was depicted for the oceanic, upwelling and eddy system in the Canary Current System. The effect of mesoscale phenomena in the region is of paramount importance in order to understand the development of zooplankton. In addition to the tremendous increase in production in the coastal area off Northwest Africa, the coupling of this production with the oceanic area through filaments and eddies topographically formed in the coast or shed by the islands

Acknowledgements

The authors are indebted to three anonymous reviewers who helped to improve the manuscript. This study was funded by project ConAfrica (CTM2004-02319) from the Spanish Ministry of Education and the European Union.

References (156)

  • A. Hernández-Guerra et al.

    Temporal variability of mass transport in the Canary Current

    Deep-Sea Res. II

    (2002)
  • A. Hernández-Guerra et al.

    Transport variability in the Lanzarote passage (Eastern Boundary Current of the North Atlantic Subtropical Gyre)

    Deep-Sea Res. I

    (2003)
  • S. Hernández-León et al.

    Vertical distribution of zooplankton in Canary Island waters: implications for export flux

    Deep-Sea Res. I

    (2001)
  • S. Hernández-León et al.

    Zooplankton biomass and indices of feeding and metabolism in island-generated eddies

    J. Mar. Syst.

    (2001)
  • S.A. Huntsman et al.

    Primary production off northwest Africa: The relationship to wind and nutrient conditions

    Deep-Sea Res.

    (1977)
  • D.M. Karl et al.

    Seasonal and interannual variability in primary production and particle flux at Station ALOHA

    Deep-Sea Res. II

    (1996)
  • A. Khripounoff et al.

    Vertical and temporal variations of particle fluxes in the deep Tropical Atlantic

    Deep-Sea Res. I

    (1998)
  • R. Le Borgne et al.

    Net zooplankton and the biological pump: a comparison between the oligotrophic and mesotrophic equatorial Pacific

    Deep-Sea Res. II

    (1997)
  • A. Longhurst et al.

    The biological pump: profiles of plankton production and consumption in the upper ocean

    Progr. Oceanogr.

    (1989)
  • A.R. Longhurst et al.

    Vertical flux of respiratory carbon by oceanic diel migrant biota

    Deep-Sea Res. I

    (1990)
  • F. Machín et al.

    Mass fluyes in the Canary basin

    Progr. Oceanogr.

    (2006)
  • P. Andreu-Puyal

    Contribución al estudio de los eufausiáceos de los alrededores de cabo Blanco (NW Africa)

    Res. Exp. Cient. B7O Cornide

    (1976)
  • Angel, M.V., 1989. Does mesopelagic biology affect the vertical flux? In: Berger, V.S., Smetacek, V.S., Wefer, G....
  • R. Arfi

    Variabilité inter-annuelle d’un indice d’intensité des remontées d’eau dans le secteur du Cap Blanc (Mauritanie)

    Can. J. Fish. Aquat. Sci.

    (1985)
  • J. Arístegui

    La distribución de la clorofila a en aguas de Canarias

    Bol. Inst. Esp. Oceanogr.

    (1990)
  • Arístegui, J., Hernández-León, S., Gómez, M., Medina, L., Ojeda, A., Torres, S., 1989. Influence of the north trade...
  • J. Arístegui et al.

    The seasonal planktonic cycle in coastal waters of the Canary Islands

    Sci. Mar.

    (2001)
  • J. Arístegui et al.

    Organic carbon distribution and water column respiration in the NW Africa–Canaries coastal transition zone

    Aquat. Microb. Ecol.

    (2003)
  • J. Arístegui et al.

    Oceanography and fisheries of the Canary current/Iberian region of the Eastern North Atlantic

  • V. Bainbridge

    Occurrence of Calanoides carinatus in the plankton of the Gulf of Guinea

    Nature

    (1960)
  • A. Bakun

    Ocean Triads and radical interdecadal stock variability: Bane and boon for fishery management science

  • Ballesteros, S., 1994. Influencia de las estructuras mesoescalares sobre la distribución y abundancia de bacterias y...
  • E.D. Barton

    Meanders, eddies and intrusions in the thermohaline front off Northwest Africa

    Oceanol. Acta

    (1987)
  • E.D. Barton et al.

    Lee region of Gran Canaria

    J. Geophys. Res.

    (2000)
  • Basterretxea, G., 1994. Influencia de las estructuras oceanográficas mesoscalares sobre la producción primaria en la...
  • G. Basterretxea et al.

    Mesoscale variability in phytoplankton biomass distribution and photosynthetic parameters in the Canary–NW African coastal transition zone

    Mar. Ecol. Prog. Ser.

    (2000)
  • W. Beckmann et al.

    Cyclonic cold-core eddy in the eastern North Atlantic. III Zooplancton

    Mar. Ecol. Prog. Ser.

    (1987)
  • P. Bécognée et al.

    Annual cycle of clupeiform larvae around Gran Canaria Island, Canary Islands

    Fish. Oceanogr.

    (2006)
  • M. Blackburn

    Oceanography and the ecology of tunas

    Oceanogr. Mar. Biol. A Rev.

    (1965)
  • Blackburn, M., 1977. Studies on pelagic animal biomasses. In: Andersen, N.R., Zahuranec, B.J. (Eds.), Oceanic Sound...
  • J.H.S. Blaxter

    The role of light in the vertical migration of fish, a review

  • J.H.S. Blaxter et al.

    The effects of artificial lights on acoustic scattering layers in the ocean

    Symp. Zool. Soc. Lond.

    (1967)
  • B.P. Boden et al.

    The influence of natural light on the vertical migrations of an animal community in the sea

    Symp. Zool. Soc. Lond.

    (1967)
  • J.G. Braun

    Estudios de producción en aguas de las Islas Canarias. I. Hidrografía, nutrientes y producción primaria

    Bol. Inst. Esp. Oceanogr.

    (1980)
  • J.G. Braun

    Estudios de producción en aguas de las Islas Canarias. II. Producción del zooplancton

    Bol. Inst. Esp. Oceanogr.

    (1981)
  • J.G. Braun et al.

    Variaciones en la producción primaria en aguas canario-africanas

    Bol. Inst. Esp. Oceanogr.

    (1974)
  • J.G. Braun et al.

    Algunas comparaciones entre el nanoplancton y el fitoplancton de red en aguas de as Islas Canarias

    Bol. Inst. Esp. Oceanogr.

    (1981)
  • J.G. Braun et al.

    Estudios de producción en la bahía de Antequera: una comparación con aguas oceánicas

    Bol. Inst. Esp. Oceanogr.

    (1984)
  • J.G. Braun et al.

    Observaciones químicas y biológicas en el NW de Africa, entre Cabo Juby y Cabo Ghir

    Bol. Inst. Esp. Oceanogr.

    (1976)
  • J.G. Braun et al.

    Productividad y biomasa del ultraplancton, nanoplancton y fitoplancton de red en aguas de las Islas Canarias

    Bol. Inst. Esp. Oceanogr.

    (1985)
  • Cited by (62)

    • Modeling investigation of the nutrients and phytoplankton dynamics in the Moroccan Atlantic coast: A case study of Agadir coast

      2021, Ecological Modelling
      Citation Excerpt :

      A coupled modeling system able of comprehensively capturing the cycle of biogeochemical processes occurring in water column could facilitate ecological analysis of ecosystem dynamics, making it a useful tool for investigating nutrient and plankton variability in coastal areas. Although the biogeochemical variables in the coastal areas off the Canary Current System (North-West Africa) has been restrictively discussed in previous studies (e.g., Hernández-León et al., 2007, 2019; Lovecchio et al., 2017, 2018; Arístegui et al., 2020; Santana-Falcón et al., 2020), there is still a lack of knowledge about its biogeochemical functioning of the Agadir coast. To our knowledge, no high-resolution numerical model has yet been implemented to describe the biogeochemical properties of this area.

    View all citing articles on Scopus
    View full text