Living krill, zooplankton and experimental investigations: a discourse on the role of krill and their experimental study in marine ecology

Abstract

Krill occupy critical positions in a many marine ecosystems and have been the subject of a number of concerted studies yet there are large areas of their biology that still remain a mystery. Most species of krill are open ocean animals, which makes direct observation and sampling difficult. Krill also exhibit a number of physiological and behavioural attributes which frustrate attempts to understand their life history. Krill are conceptually difficult to come to terms with; they are obviously different from larger marine organisms such as squid, fish, whales and fish yet they are also quite distinct from those animals classed as zooplankton such as copepods. Despite these differences they have most often been grouped with zooplankton and have been studied using techniques developed for animals which are orders of magnitude smaller than they. This mismatch has affected our view of their interactions with the physical world and also affects their perceived trophic interactions. Their size and mobility also interferes with our ability to sample them effectively and thus to develop our appreciation of their true role in the marine ecosystem. Understanding how intermediate-sized animals, such as krill, function in aquatic ecosystem is critical to better management of the marine environment.

Keywords:

• Krill
• Euphausiid
• Zooplankton
• Sampling
• Krill experimentation

Acknowledgements

The author would like to thank his colleagues, particularly those who attended the Nagoya Workshop, for their stimulating discussions, which led to the production of this article. The two referee's contribution to the final shape of this article was also substantial.