Top-down control on LCZ: Predation

During warm years, there is a decrease in LCZ on the southern shelf.  One explanation is that warmer temperatures increase spatial overlap between predators (i.e. pollock) and prey (LCZ).  Cold water (<2°C) excludes fish (pollock, cod) from the shelf, and thereby reduces grazing pressure on LCZ.  In addition, grazing rates (due to increased metabolic rates) of predators vary between warm and cold years.

Hypothesis 4.1 LCZ biomass and spatial distributions are the result of predation, and vary inversely with the abundance and spatial distribution of predators.

Hypothesis 4.2 LCZ top-down control by predation is greatest during warm years when there is less extensive ice cover in the spring, a smaller cold pool in the summer, and a greater metabolic requirement by many top predators. 

Question 4.1 What is the spatial distribution of LCZ and their top predators in warm and cold years?

Question 4.2 What is the partitioning of LCZ biomass among top predators in each domain, in the northern and southern shelf, and in warm and cold years?

Question 4.3 During winter, do predators continue to consume LCZ, and does warmer water in winter result in higher consumption of LCZ by their main predators?