Weird problem with biomass?

Question

In marine systems, the ecological pyramid is often inverted, i.e. there is less biomass of the first trophic level (phytoplankton) than on the second one (zooplankton, small fish, etc). How is that possible if primary producers maintain the rest of the ecosystem?

Answer 1

There's a really good explanation of this at the website listed below, about 3/4 of the way down the site. It has to do with lifespans, standing crop, and turnover rate. The phytoplankton have a short lifespan, but they reproduce quickly and can produce more biomass at a very rapid rate. So they may not be represented by a large standing crop at any one time, but they produce a large amount of biomass overall to support the next trophic level. So the pyramid really only "appears" to be inverted. Have a look at the website for a more thorough explanation.