Quantification of the Synergistic Effects of Eutrophication, Apex Predator Pressure, and Internal Processes on the Black Sea Ecosystem

In the present study, a model of the lower-trophic pelagic food web of the Black Sea is considered in order to provide a quantitative understanding of the marked changes in the food web structure in response to changing top-down and bottom-up control mechanisms due to eutrophication, overfishing, and climatic changes. The simulations consider three particular parameters controlling the changes in the ecosystem structure due to these stressors; (i) the magnitude of the nitrate flux into the euphotic layer from the chemocline layer (enrichment due to eutrophication), (ii) the magnitude of predation control introduced by the planktivorous fish on mesozooplankton (fishery), (iii) the magnitude of the Q(10) parameter controlling temperature dependence of the Mnemiopsis growth (changing climatic conditions). A simulation assessing the level of enrichment on the ecosystem indicates a shift of the major trophic energy flow towards Noctiluca and Aurelia and thus showing how the ecosystem would degrade when a critical level of enrichment is passed. Increasing predation pressure of the planktivorous fish during the enrichment phase is shown to reduce the mesozooplankton biomass that in turn declines its predation pressure on Noctiluca population and thus allows Noctiluca biomass to increase, considering that mesozooplanton is assumed to feed on Noctiluca (at a level of 15% food preference) in the current model.. Noctiluca then acts as a major consumer and a critical element of the degraded food web structure. The overfishing of planktivorous fish stocks allows Mnemiopsis biomass to increase considerably under changing (warmer) climatic conditions at the end of 1980s, following a decade-long intense cooling phase. Thus, our results suggest that overfishing would not alone be able to promote a Mnemiopsis population outburst in the absence of warming.


A coupled plankton-anchovy population dynamics model assessing nonlinear controls of anchovy and gelatinous biomass in the Black Sea
OĞUZ, Temel; Salihoğlu, Barış; Fach Salihoğlu, Bettina Andrea (2008-01-01)
A coupled model of lower trophic levels and anchovy Engraulis encrasicolus ponticus population dynamics was developed to analyze the mechanisms controlling sharp anchovy and gelatinous zooplankton biomass transitions from the 1960s to the 1980s in the Black Sea. An increase in anchovy stocks from estimated low (similar to 300 kt) to moderate (similar to 700 kt) in the late 1960s was related to weakening piscivore predation pressure, slight nutrient enrichment of the basin during an early eutrophication phas...
Challenges in integrative approaches to modelling the marine ecosystems of the North Atlantic: Physics to fish and coasts to ocean
Holt, Jason; Allen, J. Icarus; Anderson, Thomas R.; Brewin, Robert; Butenschoen, Momme; Harle, James; Huse, Geir; Lehodey, Patrick; Lindemann, Christian; Memery, Laurent; Salihoğlu, Barış; Senina, Inna; Yool, Andrew (2014-12-01)
It has long been recognised that there are strong interactions and feedbacks between climate, upper ocean biogeochemistry and marine food webs, and also that food web structure and phytoplankton community distribution are important determinants of variability in carbon production and export from the euphotic zone. Numerical models provide a vital tool to explore these interactions, given their capability to investigate multiple connected components of the system and the sensitivity to multiple drivers, incl...
Invasion dynamics of the alien ctenophore Mnemiopsis leidyi and its impact on anchovy collapse in the Black Sea
Oğuz, Temel; Fach Salihoğlu, Bettina Andrea; Salihoğlu, Barış (2008-12-01)
The mechanisms governing the unprecedented 1989-90 anchovy-Mnemiopsis shift event in the Black Sea were evaluated with a coupled model of bioenergetic-based anchovy population dynamics and lower trophic food web structure. Simulations showed that a combination of direct and density-dependent effects of overfishing, eutrophication-induced nutrient enrichment, climate-induced over-enrichment and temperature-controlled Mnemiopsis spring production were involved in the shift. Eutrophication made the system vuln...
Modeling the impact of climate variability on Black Sea anchovy recruitment and production
Güraslan, Ceren; Fach Salihoğlu, Bettina Andrea; Oğuz, Temel (2014-09-01)
The connection of climate variability with anchovy spawning and recruitment in the Black Sea in particular, and other ecosystems in general, was studied using a two-way coupled lower trophic level and anchovy bioenergetics model. Climate variability was represented by a 50-yr time series of daily temperature and vertical mixing rates with stochastic variations. Temperature was found to be the dominant factor influencing early life stages and hence population dynamics of Black Sea anchovy as marked by a high...
Yilmaz, Elif; Salihoğlu, Barış; Department of Oceanography (2016-10-12)
Three areas of different ecosystem characteristics in the Northern Levantine Basin is compared using a 1-D multicomponent lower trophic level ecosystem model developed by SALIHOĞLU, B. et al. (2009) (NAGEM). Main focus was to analyze and compare the carrying capacity (PP) and regulatory mechanisms of the nutrients on lower trophic levels. 26 years’ of historical data obtained from METU-IMS data inventory and CORIOLIS was used to form a climatology, to introduce boundary conditions to the model as well as to...
Citation Formats
B. Salihoğlu, “Quantification of the Synergistic Effects of Eutrophication, Apex Predator Pressure, and Internal Processes on the Black Sea Ecosystem,” TURKISH JOURNAL OF FISHERIES AND AQUATIC SCIENCES, pp. 581–592, 2013, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/30806.