Copepod communities, production and grazing in the Turkish Straits System and the adjacent northern Aegean Sea during spring

https://doi.org/10.1016/j.jmarsys.2011.02.002Get rights and content

Abstract

The Mediterranean and the Black Seas are connected through Bosphorus, Marmara Sea and Dardanelles (Turkish Straits System, TSS). In this study, we examined the spatial distribution of copepods and investigate their production and grazing. The aim was to understand the transfer of phytoplankton/microzooplankton production up the food chain in TSS and Aegean Sea during spring. The phytoplankton and microzooplankton biomass and production showed a clear decreasing trend from Bosphorus to the Aegean Sea, whereas copepod biomass did not reveal any distinct trend and only the number of copepod species increased from Bosphorus to the Aegean Sea. Production of copepods and egg production showed similar trends except for the Bosphorus, where production of copepods was very low due to the low copepod biomass in this area. In all areas, the copepod carbon demand was largely met by phytoplankton and microzooplankton production. However, only a low amount of primary production was consumed by copepods and production appeared to flow mostly through other pathways (microbial loop) and/or sediment on the bottom. The results of this study confirm the hypothesis that there is a substantial differentiation within pelagic food web structure and carbon flow from Bosphorus to the Aegean Sea.

Research highlights

► We examine the copepod communities, production and grazing in Turkish Strait System and Aegean Sea. ► Carbon flow and microplankton biomass and production are also investigated. ► A substantial differentiation of the pelagic food web structure was found among areas. ► Phytoplankton production pass through other pathways (microbial loop and/or to the bottom).

Introduction

The Mediterranean and the Black Seas, representing the Southern European Seas, are two interconnected semi-enclosed basins, which, however, have distinct and very different characteristics. The two seas are connected through Bosphorus, Marmara Sea and Dardanelles the so-called Turkish Straits System (TSS). Hydrological, meteorological and biological characteristics are combined forming a distinct ecosystem between the Mediterranean and the Black Seas. The TSS is an important structure specifying the hydrology of the Black and Aegean Seas (Özsoy et al., 2002). Flows through the Turkish Straits are driven by density differences between the Black and the Aegean Seas and the maintained net level difference between these seas (Unluata et al., 1990). The TSS controls the exchange of matter (water, passive or active chemical/biological substances, and fish) between the Black and the Mediterranean Seas. Water masses, exiting through the TSS into the northern Aegean, impact nutrient recycling, productivity and feeding of local and migrating species. While the hydrological aspects of the TSS are well documented (Özsoy et al., 2002), biological data remain very limited. Studies on the mesozooplankton have focused mainly on the distribution and composition of the mesozooplankton community concluding that zooplankton abundance is primarily controlled by fluctuations in physical environment, eutrophication and pollution (e.g. Tarkan, 2000, Tarkan et al., 2005, Yilmaz et al., 2005, Svetlichny et al., 2006, Isinibilir et al., 2008). Concerning copepod production and grazing as well as food web structure, information is lacking.

The neighboring northern Aegean Sea receives the modified Black Sea Water mass (BSW). The very light, brackish inflow of this water mass usually occupies the uppermost water layer (20–30 m) and it is well detectable in the northern part of the Aegean Sea (Theocharis and Georgopoulos, 1993). The BSW inflow, enriched in dissolved organic carbon and nitrogen (Polat and Tugrul, 1996, Lykousis et al., 2002) induces hydrological complexity (e.g. gyres and fronts) that can be highly mobile in variable time scales (Zervakis and Georgopoulos, 2002). The consequence of this inflow is a plankton production among the highest in the Eastern Mediterranean for both autotrophs and heterotrophs (Ignatiades et al., 2002, Siokou-Frangou et al., 2002). Mesozooplankton standing stock and species composition are affected by the mesoscale features formed from the advection of the BSW and the formation of the halocline/pycnocline (Zervoudaki et al., 2006, Isari et al., 2006, Siokou-Frangou et al., 2009). The carbon flow in pelagic food web is very efficient and is expected to affect the production of higher trophic levels (Siokou-Frangou et al., 2002, Zervoudaki et al., 2007). Notwithstanding the influence of the BSW in the northern Aegean Sea has already been addressed in the above studies, a concurrent study of mesozooplankton communities and food web structure from Bosphorus, Marmara Sea and Dardanelles to the northern Aegean Sea is crucial for the clarification of the impact of the BSW inflow into the northeastern Mediterranean Sea.

In this study, we have focused on the copepod communities during the spring period. This group consists of the major mesozooplankton fraction in TSS and northern Aegean Sea (Kovalev et al., 2003, Zervoudaki et al., 2006) and it is well known that copepods play the key role in transferring primary production to higher trophic levels in all pelagic ecosystems (Verity and Smetacek, 1996). Knowledge about their rates (production and grazing) is essential in the scope of understanding the flux of carbon and nutrients through the food chain. Thus, here, we examine the spatial distribution of copepods in the TSS and the northern Aegean Sea, compare their production and grazing on phytoplankton and microzooplankton and finally resolve the carbon flow in the above systems.

Section snippets

Sampling and hydrography

This study was undertaken from 10 to 15 April 2008 in the northern Aegean Sea aboard the R/V “Aegaeo” (Hellenic Centre for Marine Research) and in the Turkish Straits System (Dardanelles and Bosphorus Straits and Marmara Sea) aboard the R/V “Bilim” (Middle East Technical University). The study area comprised of one station in the northern Aegean Sea (station: AS), one station in Dardanelles (station: DS), three stations in Marmara Sea (stations: MS1, MS2 and MS3) and one station in Bosphorus

Hydrography, chl a and potential food for copepods

The vertical profiles of temperature and salinity revealed that the water column was characterized by a surface layer (salinity < 35) originated from the brackish Black Sea Water (BSW). Intruding Bosphorus, the BSW is modified along the transect generating a distinct gradient at the surface salinity from Bosphorus (17.6) to the Aegean Sea (33.4). The thickness of this BSW layer was differentiated among stations. At stations in the Marmara Sea the halocline were located between 20 and 30 m. In

Patterns in copepod communities, production and grazing

Due to a positive water balance in the Black Sea, its water masses are transferred into the Marmara Sea through the Bosphorus forming a brackish surface layer (15–20 m) with a salinity of 18 to 24 and temperature ranging from 20 to 24 °C in summer and from 8 to 9 °C in winter. Below this brackish water layer lays more saline (about 39) Mediterranean water veof Levantine origin, with a constant temperature of about 15 °C throughout the year (Besiktepe et al., 1994). These water-mass dynamics have

Conclusions

This study, based on the copepod communities, analyzed the spatial differentiation of the pelagic food web structure and the carbon flow from Bosphorus to the Aegean Sea during spring. The transition area between the Black Sea and the Aegean Sea is characterized by high gradients in salinity and pelagic fauna compositions. The phytoplankton/microzooplankton biomass and production showed a clear decreasing trend from Bosphorus to the Aegean Sea, whereas copepod biomass and production did not

Acknowledgments

We thank the captain and the crew of R/V ‘Aegaeo’ and R/V ‘Bilim’ for shipboard assistance. We also thank T.G. Nielsen for commenting on a draft version of the manuscript and the three anonymous reviewers for their very valuable comments on the manuscript. Research for this paper was supported by the SESAME project (contract no. 036949), supported by the European Commission's Sixth Framework Programme on Sustainable Development, Global Change and Ecosystem.

References (103)

  • V. Lykousis et al.

    Major outputs of the recent multi-disciplinary biogeochemical researches in the Aegean Sea

    Journal of Marine Systems

    (2002)
  • M.G. Mazzocchi et al.

    The temporal variability of Centropages typicus in the Mediterranean Sea: from seasonal to decadal scales

    Progress in Oceanography

    (2007)
  • E. Morkoc et al.

    Towards a clean Izmit Bay

    Environmental International

    (2001)
  • D. Orhon

    Evaluation of the impact from the Black Sea on the pollution of the Marmara Sea

    Water Science and Technology

    (1995)
  • I. Siokou-Frangou et al.

    Variability of mesozooplankton spatial distribution in the North Aegean Sea, as influenced by the Black Sea waters outflow

    Journal of Marine Systems

    (2009)
  • A. Theocharis et al.

    Dense water formation over the Samothraki and Limnos plateaus in the North Aegean Sea (Eastern Mediterranean-Sea)

    Continental Shelf Research

    (1993)
  • I.N. Yilmaz et al.

    Evidence for influence of a heterotrophic dinoflagellate (Noctiluca scintillans) on zooplankton community structure in a highly stratified basin

    Estuaries Coastal Shelf Science

    (2005)
  • U. Båmstedt et al.

    Feeding

  • S.H. Ban et al.

    The paradox of diatom-copepod interactions

    Marine Ecology Progress Series

    (1997)
  • H.A. Benli et al.

    Comparison of the mesozooplankton composition the southwestern Black Sea, Sea of Marmara and eastern Aegean Sea

    Turkish Journal of Marine Science

    (2001)
  • U. Berggreen et al.

    Food size spectra, ingestion and growth of copepod Acartia tonsa, implications for the determination of copepod production

    Marine Biology

    (1988)
  • G.C.R. Bollens et al.

    Feeding dynamics of Acartia spp. copepods in a large, temperate estuary (San Francisco Bay, CA)

    Marine Ecology Progress Series

    (2003)
  • D. Bonnet et al.

    Development and egg production in Centropages typicus (Copepoda: Calanoida) fed different food types: a laboratory study

    Marine Ecology Progress Series

    (2001)
  • E. Broglio et al.

    Trophic impact and prey selection by crustacean zooplankton on the microbial communities of an oligotrophic coastal area (NW Mediterranean Sea)

    Marine Ecology Progress Series

    (2004)
  • A. Calbet et al.

    The ciliate-copepod link in marine ecosystems

    Aquatic Microbial Ecology

    (2005)
  • A. Calbet et al.

    Copepod egg production in the NW Mediterranean: effects of winter environmental conditions

    Marine Ecology Progress Series

    (2002)
  • D. Calliari et al.

    Feeding and reproduction in a small calanoid copepod: Acartia clausi can compensate quality with quantity

    Marine Ecology Progress Series

    (2005)
  • Y. Carotenuto et al.

    Annual cycle of early developmental stage survival and recruitment in the copepods Temora stylifera and Centropages typicus

    Marine Ecology Progress Series

    (2006)
  • G. Cervetto et al.

    Adaptation aux variations de la salinite chez le copepode Acartia clausi

    Journal de la Recherché Océanographique

    (1995)
  • F.E. Chinnery et al.

    The influence of temperature and salinity on Acartia (Copepoda: Calanoida) nauplii survival

    Marine Biology

    (2004)
  • E.D. Christou et al.

    Length, weight and condition factor of Acartia clausi (Copepoda) in the Eastern Mediterranean

    Journal of the Marine Biological Association of the United Kingdom

    (1993)
  • K.R. Clarke et al.

    Change in marine communities: an approach to statistical analysis and interpretation

  • I. Di Capua et al.

    Population structure of the copepods Centropages typicus and Temora stylifera in different environmental conditions

    ICES Journal of Marine Science

    (2004)
  • J. Dutz et al.

    Importance and nutritional value of large ciliates for the reproduction of Acartia clausi during the post spring-bloom period in the North Sea

    Aquatic Microbial Ecology

    (2008)
  • J. Dutz et al.

    Copepod reproduction is unaffected by diatom aldehydes or lipid composition

    Limnology and Oceanography

    (2008)
  • L. Fessenden et al.

    Copepod predation on phagotrophic ciliates in Oregon coastal waters

    Marine Ecology Progress Series

    (1994)
  • J.G. Field et al.

    A practical strategy for analysing multispecies distribution patterns

    Marine Ecology Progress Series

    (1982)
  • B.W. Frost

    Effect of size and concentration of food particles on the feeding behaviour of the marine planktonic copepod Calanus pacificus

    Limnology and Oceanography

    (1972)
  • Y. Fukuda et al.

    Potential dietary effects on the fatty acids composition of the common jellyfish Aurelia aurita

    Marine Biology

    (2001)
  • D.J. Gifford et al.

    The microzooplankton link, consumption of planktonic protozoa by the calanoid copepods Acartia tonsa Dana and Neocalanus plumchrus Murukawa

    Marine Microbial Food Webs

    (1991)
  • A.D. Gubanova et al.

    Dramatic change in the copepod community in Sevastopol Bay (Black Sea) during two decades (1976–1996)

    Senckenbergiana Maritima

    (2001)
  • C. Halsband-Lenk et al.

    Seasonal cycles of egg production of two planktonic copepods, Centropages typicus and Temora stylifera, in the north-western Mediterranean Sea

    Journal of Plankton Research

    (2001)
  • P.J. Hansen et al.

    Zooplankton grazing and growth, scaling within the 2–2000 mm body size range

    Limnology and Oceanography

    (1997)
  • L.J. Hansson et al.

    Release of dissolved organic carbon (DOC) by the scyphozoan jellyfish Aurelia aurita and its potential influence on the production of planktik bacteria

    Marine Biology

    (1995)
  • O. Holm-Hansen et al.

    Fluorometric determination of chlorophyll

    Journal de Conseil pour l'Exploration de la Mer

    (1965)
  • R.R. Hopcroft et al.

    Production of tropical copepods in Kingston Harbour, Jamaica: the importance of small species

    Marine Biology

    (1998)
  • S.E.L. Houde et al.

    Effects of food quality on the functional ingestion response of the copepod Acartia tonsa

    Marine Ecology Progress Series

    (1987)
  • A. Ianora et al.

    Seasonal fluctauations in fecundity and hatching success in the planktonic copepod Centropages typicus

    Journal of Plankton Research

    (1992)
  • S. Isari et al.

    Mesozooplankton distribution in relation to hydrology of the Northeastern Aegean Sea, Eastern Mediterranean

    Journal of Plankton Research

    (2006)
  • M. İşinibilir et al.

    Distribution of the Invasive Ctenophore Mnemiopsis leidyi (Agassiz, 1865) in the North-eastern Aegean Sea in August 1998

    Turkish Journal of Fisheries and Aquatic Sciences

    (2002)
  • Cited by (26)

    • Coupling plankton - sediment trap - surface sediment coccolithophore regime in the North Aegean Sea (NE Mediterranean)

      2019, Marine Micropaleontology
      Citation Excerpt :

      In addition, Souvermezoglou and Krasakopoulou (2002) have detected the North Aegean nutricline at ~150 m depth. This oligotrophic region may display mesotrophic characteristics during the high-productivity spring period, influenced by the BSW influx, with chlorophyll-a (Chl-a) reaching concentrations of 1 μg l−1 (Ignatiades et al., 2002; Zervoudaki et al., 2011; Lagaria et al., 2013; Malinverno et al., 2016). Despite the presence of the surface BSW layer, Chl-a values are lower during fall (~0.2 μg l−1), making the basin an oligotrophic area (Ignatiades et al., 2002; Lagaria et al., 2013, 2017).

    View all citing articles on Scopus
    View full text