Case Study for 10/4/00 (Trophic Levels)

Case Study for 10/4/00 (Trophic Levels)

Source: PICES Scientific Report No. 7, 1997

Key authors/ scientists involved in study and report and highlighted in this case study:

-Sinjae Yoo: Korea Ocean Research and Development Institute, Chairman of the Lower Trophic Level Response group under CCCC

-Patricia Livingston: National Marine Fisheries Service, Alaska Fisheries Science Center, Chairwoman of the Upper Trophic Level Response group under CCCC

Summary:

PICES, the North Pacific Marine Science Organization based in British Columbia, Canada has been developing a model to attempt to measure the effects of climate change on the ecosystem of the North Pacific. To measure and predict the effects of climate change, particularly the warming of the oceans caused by an increase of carbon dioxide in the atmosphere, a research group under PICES created a program called Climate Change and Carrying Capacity (CCCC). Through this program, scientists attempted to predict the climatic and ecosystem changes in the North Pacific by focusing specifically on the various trophic levels of the ecosystem, from the primary producers to the higher trophic levels of consumers in the ecosystem. The studies were conducted in basin-scale (open deep) waters as well as coastal ecosystems in the North Pacific (Introduction- Report 7).

The main hypotheses in the study, which also formed the bases upon which to develop models for the ecosystem and prediction of future changes in the ecosystem, suggested that climate change (“atmospheric or physical forcing”) would affect primary production in the ecosystem, and these effects would subsequently transfer indirectly and directly to higher trophic levels (sections 6.2 and 6.3- Report 7). The research groups measured changes in nutrients and amount of chlorophyll in the ecosystem to sensor changes in primary productivity (Section 3- Report 7). They chose to target effects upon the following primary and secondary producers in their study of lower trophic levels in North Pacific ecosystems: nutrients, phytoplankton, zooplankton, microzooplankton, copepods, and euphasids (Section 6.2- Report 7). They measured effects on higher trophic level (primary, secondary and tertiary consumers) by monitoring species such as salmon, mackerel, sardines, anchovies, blue and salmon sharks, tuna, squid, fur seals, and sea birds including shearwaters, common murres, and auklets.

This case study reveals the importance of understanding trophic levels and energy flow in ecosystems, since the main hypothesis of PICES research is that climate variability is affecting primary productivity in the North Pacific. Due to constant interaction between trophic levels in that ecosystem, researchers hypothesize that changes in primary production are influencing all levels of species in the ecosystem.