Ecosystem indicators-accounting for variability in species' trophic levels

Reed, Jodie
Shannon, Lynne
VELEZ, Laure
Akoğlu, Ekin
BUNDY, Alida
Coll, Marta
FU, Caihong
FULTON, Elizabeth A.
Gruss, Arnaud
HEYMANS, Johanna J.
HOULE, Jennifer E.
John, Emma
LE LOC'H, Francois
Salihoğlu, Barış
VERLEY, Philippe
Shin, Yunne-Jai
Trophic level (TL)-based indicators are commonly used to track the ecosystem effects of fishing as the selective removal of organisms from the food web may result in changes to the trophic structure of marine ecosystems. The use of a fixed TL per species in the calculation of TL-based indicators has been questioned, given that species' TLs vary with ontogeny, as well as over time and space. We conducted a model-based assessment of the performance of fixed TL-based indicators vs. variable TL-based indicators for tracking the effects of fishing pressure. This assessment considered three TL-based indicators (the trophic level of the landed catch (TLc), the marine trophic index (MTI) and the trophic level of the surveyed community (TLsc)), three fishing scenarios that targeted specific model groups (the low TL scenario (LTL), the high TL scenario (HTL) and a scenario encompassing broad-scale exploitation (ALL)) and ten contrasting marine ecosystems with four types of ecosystem modelling approaches that differ in their structure and assumptions. Results showed that, overall, variable TL-based indicators have a greater capacity for detecting the effects of fishing pressure than fixed TL-based indicators. Across TL-based indicators, TLsc displayed the most consistent response to fishing whether fixed or variable species' TLs were used, as well as the highest capacity for detecting fishing effects. This result supports previous studies that promote the use of survey-based indicators over catch-based indicators to explore the impacts of fishing on the structure of marine ecosystems. Across fishing scenarios, the low trophic level fishing scenario (LTL) resulted in the lowest consistency between fixed and variable TL-based indicator responses and the lowest capacity of TL-based indicators for detecting fishing effects. Overall, our results speak to the need for caution when interpreting TL-based indicator trends, and knowledge of the broader context, such as fishing strategies and exploitation history.


Ecosystem and primary production interactions in three contrasting sites in thenorthern levantine basın
Yılmaz, Elif; Salihoğlu, Barış; Uysal, Zahit; Yumruktepe, Veli; Tezcan, Devrim; Örek, Hasan; Tuğrul, Süleyman (null; 2016-09-16)
To determine the effects of different nutrient dynamics in the Levatine Basin a 1-D multi component lower trophic ecosystem model is used and the carrying capacity and regulatory mechanisms of the nutrients on upper trophic levels at three contrasting marine sites in the Northeastern Mediterranean is assessed. Offshore waters of Mersin Bay, coastal sites of Erdemli and Rhodes Gyre is chosen as they represent distinctive characteristics in terms of nutrients dynamics. Model results suggest distinct mechanism...
The specificity of marine ecological indicators to fishing in the face of environmental change: A multi-model evaluation
Shin, Yunne-Jai; Houle, Jennifer E.; Akoğlu, Ekin; Blanchard, Julia L.; Bundy, Alida; Coll, Marta; Demarcq, Herve; Fu, Caihong; Fulton, Elizabeth A.; Heymans, Johanna J.; Salihoğlu, Barış; Shannon, Lynne; Sporcic, Miriana; Velez, Laure (2018-06-01)
Ecological indicators are widely used to characterise ecosystem health. In the marine environment, indicators have been developed to assess the ecosystem effects of fishing to support an ecosystem approach to fisheries. However, very little work on the performance and robustness of ecological indicators has been carried out. An important aspect of robustness is that indicators should respond specifically to changes in the pressures they are designed to detect (e.g. fishing) rather than changes in other driv...
Biomass changes and trophic amplification of plankton in a warmer ocean
Chust, Guillem; et. al. (2014-07-01)
Ocean warming can modify the ecophysiology and distribution of marine organisms, and relationships between species, with nonlinear interactions between ecosystem components potentially resulting in trophic amplification. Trophic amplification (or attenuation) describe the propagation of a hydroclimatic signal up the food web, causing magnification (or depression) of biomass values along one or more trophic pathways. We have employed 3-D coupled physical-biogeochemical models to explore ecosystem responses t...
The Role of Top-Down and Bottom-Up Control for Phytoplankton in a Subtropical Shallow Eutrophic Lake: Evidence Based on Long-Term Monitoring and Modeling
Mao, Zhigang; Gu, Xiaohong; Cao, Yong; Zhang, Min; Zeng, Qingfei; Chen, Huihui; Shen, Ruijie; Jeppesen, Erik (Springer Science and Business Media LLC, 2020-02-03)
Lake ecosystems are exposed to a range of anthropogenic pressures, particularly eutrophication, and in some cases also stocking and/or overfishing of top-predator fish species, all factors that have implications for the food web structure and which could lead to dominance of nuisance cyanobacteria. Restoration of degraded lakes demands insight into the relative role of top-down for bottom-up regulating forces. While knowledge about these forces in temperate lakes is extensive, comparatively little is known ...
Forest management affects saproxylic beetles through tree species composition and canopy cover
Edelmann, Pascal; Ambarlı, Didem; Gossner, Martin M.; Schall, Peter; Ammer, Christian; Wende, Beate; Schulze, Ernst-Detlef; Weisser, Wolfgang W.; Seibold, Sebastian (2022-11-01)
Forest management has been shown to affect biodiversity, but the effects vary among taxa and studies. Due to their host-tree preferences, many saproxylic, i.e. deadwood-dependent, beetle species are likely affected by forest management via changes in tree species composition. However, further structural differences caused by forest management, such as microclimatic conditions, may interfere with effects of tree species. We lack a more detailed understanding of how forest management intensity influences sapr...
Citation Formats
J. Reed et al., “Ecosystem indicators-accounting for variability in species’ trophic levels,” ICES JOURNAL OF MARINE SCIENCE, pp. 158–169, 2017, Accessed: 00, 2020. [Online]. Available: