Copepods have developed two distinct behavioral strategies that have different costs and benefits when it comes to feeding, mating and escaping predators. A new PhD thesis analyses these trade-offs.
In the ocean, the millimeter sized copepods have a major role in the marine food web: they are the most important ´grazers´ of the oceans phytoplankton and are the main food source for most fish, and even for whales.
Copepods comprise thousands of species and are among the most abundant and diverse life forms on Earth. Despite their diversity copepods have developed two distinct behavioral strategies that have consequences for their trophic interactions. They either move actively through the water or they remain passive most of the time waiting from prey to pass by.
These strategies have different costs and benefits when it comes to feeding efficiency, the risk being detected by a predator or encountering mating partners and this is the subject of Hans van Someren Greve's PhD thesis. The results of his work contribute to the development of novel marine ecosystem models to improve our understanding and the predictability of marine food web dynamics.
About the defence
Hans van Someren Gréve will defend his thesis "Zooplankton Motile Behavior: Traits and trade-offs in planktonic copepods" at DTU on Friday 23 June 2017.
Supervisor
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Principal supervisor: Thomas Kiørboe, DTU Aqua
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Co supervisor: Rodrigo Almeda, DTU Aqua
Examiners
- Professor Brian R. MacKenzie, DTU Aqua
- Professor Øyvind Fiksen, University of Bergen, Norway
- Senior Researcher Maria Grazia Mazzocchi, Stazione Zoologica Anton Dohrn, Italy
Chairperson
- Senior Researcher Margit Eero, DTU Aqua
In the ocean, copepods - a millimeter sized animal - have a major role in the marine food web: they are the most important ´grazers´ of the oceans primary production (phytoplankton) and are the main food source for most fish, and even for whales.
Copepods have colonized our oceans hundreds of million years ago and today they are found in nearly all marine habitats, from the surface waters to deep-see trenches. They comprise thousands of species and are among the most abundant and diverse life forms on Earth.
Despite this their diversity copepods have developed two distinct behavioral strategies that have consequences for their trophic interactions. They either move ´actively´ through the water or they remain ´passive´ most of the time waiting from prey to pass by. These strategies have different costs and benefits when it comes to feeding efficiency, the risk being detected by a predator or encountering mating partners.
We showed through a combination of behavioral observations, classic grazing and predation experiments, and simple encounter models that these two different behavioral strategies result in a difference in grazing impact on primary production and predation rate by higher trophic levels between species, up to an order of magnitude. Further we show that food availability influences copepod behavior, and ultimately their risk of being eaten. This implies that copepod behavior is a determining factor to the grazing impact, and composition of zooplankton communities in the marine environment and ultimately energy transfer trough the marine food web.
Our results contribute to the development of novel marine ecosystem models to improve our understanding and the predictability of marine food web dynamics, which is pressing as life in our oceans may be affected by our rapidly changing climate.