Rep16 - Bering Sea - Project

## Project Definition

The Bering Sea research program adopted the program design used in the Georges Bank U.S. GLOBEC program. The major focus of the program will be a study of the influence of physical processes on zooplankton populations with a principal interest in the role of secondary production in controlling the abundance of pelagic predators (Fig. 11). Following the PICES/GLOBEC research plan, the Bering Sea program explicitly focuses on the question of climatic effects on the carrying capacity of the ecosystem. Thus, the U.S. GLOBEC scientific program in the Bering Sea is designed to address top down and bottom up controls in the ecosystem. The study will examine the following hypotheses:

1. Zooplankton production in the Bering Sea is primarily directly or indirectly controlled by four physical processes: advection, stratification, sea ice coverage, and water temperature (the extent of the cold pool). Changes in the physical environment may directly influence zooplankton populations by altering their physiology, production, or distribution. Physical processes can also indirectly influence the amount of secondary production by influencing: annual primary production, floristics, or the timing of phytoplankton production events (trophodynamic phasing).

2. Zooplankton production is jointly controlled by physical processes identified in (1) and predation by higher trophic level consumers.

3. Annual zooplankton production is primarily controlled by predation and interannual variability is controlled by the distribution and abundance of higher trophic level predators.

Studies designed to examine these hypotheses will address several related questions:

1. What are the characteristics of climatic variability; can interdecadal patterns be identified; how and when do they arise?

2. How do changes in atmospheric forcing influence the physical dynamics of the Bering Sea?

   - How does physical forcing affect ocean temperature?
   - How does physical forcing affect the timing of the formation of the cold pool?
   - Does variability in the strength and position of the Aleutian low pressure cell influence sea ice or the cold pool?
   - How do physical factors influence the mixed layer depth (MLD), mixed layer temperature (MLT), retention time scales (eddies), turbidity, and shelf/slope exchange?

3. How do life history patterns, distributions, vital rates, and population dynamics of key species respond directly and indirectly to climate variability?

   - Is there a relationship between the cold pool and larval survival or recruitment of important prey species?
   - How does the nature (e.g., timing and magnitude) of the spring bloom affect total primary production and the partition of energy between pelagic and benthic ecosystem components? Specifically, does an early bloom lead to high benthic production and a late bloom lead to high pelagic production?
   - Is there a relationship between the cold pool and larval survival or recruitment of important prey species?

4. How do higher trophic level species respond to climate variability? Are there significant intra-trophic level and top-down effects on lower trophic level production and on energy transfer efficiencies?

   - How variable is the overall productivity of the Bering Sea?
   - Given this change in productivity, has the overall carrying capacity (K) also changed for high trophic level carnivores?