Quantifying and partitioning spatiotemporal variability in secondary production and trophic transfer efficiency in pelagic marine ecosystems

这项研究旨在测量两个因素，尽管这两个因素对了解海洋食物链至关重要，但在加拿大水域却很少被测量。第一种被称为“二次生产”，即浮游动物的生产速度。浮游动物是一种微小的动物（大多数小于1厘米），它们以单细胞植物（称为“浮游植物”）为食，处于大多数海洋食物链的底部。浮游动物被大型动物吃掉，包括许多幼鱼和成鱼，某些海洋哺乳动物，甚至海鸟。第二个因素被称为“营养转移效率”（TTE）。简而言之，这是对在食物链的不同层次（例如，从浮游植物到浮游动物）之间转移的能量的估计。TTE越高，传递到食物链上游的能量就越多，可以支持的鱼类、海洋哺乳动物等的数量也就越多。

This research aims to measure two factors that, although critically important to understanding marine food chains, have rarely been measured in Canadian waters. The first is known as "secondary production", which is the rate at which zooplankton are produced. Zooplankton are tiny animals (mostly less than 1 cm in size) that feed on single-celled plants (called "phytoplankton") at the base of most marine food chains. Zooplankton are consumed by larger animals - including many young and adult fish, certain marine mammals, and even seabirds. The second factor is referred to as the "trophic transfer efficiency" (TTE). In short, this is an estimate of how much energy is transferred between different levels of the food chain (e.g. from phytoplankton to zooplankton). The higher the TTE the more energy that is transferred up the food chain, and the greater the amount of fish, marine mammals, etc. that can be supported. These two factors are essential components that underlie the mathematical models that oceanographers use to study marine food webs, and to predict how such food webs may change in the future. However, mainly for technical reasons, neither factor is measured directly in the ocean. Instead, modelers have relied on numbers drawn from simplified lab experiments or theoretical studies. My lab has developed a method to directly measure secondary production, based on measuring an enzyme (called chitobiase) that most zooplankton release into the water as they grow. When put together with measures of the rate of phytoplankton growth (known as "primary production" - something that oceanographers have been able to do since the 1960s), we have been able to produce the first direct estimates of TTE in a natural field setting. Over the next five years we will expand our work to begin exploring how secondary production and TTE vary between locations and at different timescale (i.e. seasonally, between years, etc.) off Canada's west coast. The data we generate will be used by researchers at Fisheries and Oceans Canada (and elsewhere) to refine their ecosystem models and improve their ability to forecast how Canada's marine resources may respond to changing ocean climates in the future.