Andre Visser

Andre Visser


National Institute of Aquatic Resources

Section for Oceans and Arctic

Technical University of Denmark


Building 201, room 164

2800 Kgs. Lyngby

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News from DTU

26 SEP

Trophic interactions drive diel vertical migration patterns

Using a game theoretic and mechanistic model, researchers from the Centre for Ocean Life showed how traits influencing predator-prey interactions shape the diel vertical migrating behavior of copepod communities.

28 AUG

Optimal Salmon Lice Treatment and Tragedy of the Commons

Sea lice on salmon farms are controlled via treatments. Authorities mandate treatments when sea lice infections reach a given threshold. Using a bio-economic model, we show that isolated farms profit most from a high treatment threshold, whereas a low threshold is optimal for farm networks. Operating with a low treatment threshold hence...

Diatoms (Thalassiosira sp.) Photo: Mikael Heldal, University of Bergen
23 APR

PhD defence on linking plankton models to oceanic carbon transport

On 2 May 2019, Agnethe Nøhr Hansen will defend her PhD thesis at DTU, Lyngby.

25 FEB

Competition-defense tradeoff increases the diversity of microbial plankton communities and dampens trophic cascades

Defense mechanisms are very common in unicellular plankton. A wide variety of these mechanisms (toxins, shell etc.) is observed and it is rather difficult to quantify the cost of being defended against predators using laboratory experiments. We show that the implementation of the competition-defense tradeoff in a size based model of unicellular...

22 FEB

Why are diatoms so successful?

A mechanistic model of diatoms reveals a conundrum. The defining physical attributes of diatoms – their silica shell and their large central vacuole – give diatoms an advantage over other phytoplankton taxa from time to time, but cannot in themselves explain why diatoms in general have significantly higher cell division rates...

Copepod. Photo: Erik Selander
14 FEB

Climate change is impacting the ocean’s ability to fix carbon dioxide

Climate change is influencing the distribution of zooplankton in the sea, thereby affecting the contribution made by plankton to removing carbon dioxide from the atmosphere.

Climate change CO2 separation and CO2 storage Marine research Ecosystems
12 FEB

Resource limitation determines temperature response of unicellular plankton communities

Increases in temperature increase enzymatic activity, so one expects growth to also increase. However, this is not always the case. We show that when organisms are resource-limited, an increase in temperature can actually reduce growth, but these physiological effects do not directly translate into a community response.

12 FEB

Climate change-induced shifts in the distribution of plankton alter the global carbon cycle

Changes in the distribution of zooplankton in the North Atlantic during the past 55 years has led to major changes in the biological carbon pump.

04 JAN

Predator prey games in multiple habitats reveal mixed strategies in diel vertical migration

Can we apply economic principles to fish ecology and diel vertical migration? It appears that the way fish and zooplankton behave in the presence of other individuals can be derived from mathematical notions first developed to describe the interactions between several economic players.

18 DEC

The global biogeography of zooplankton foraging traits

Do zooplankton traits matter? Scaling up trade-offs to the global scale. Taxa-transcending traits and trade-offs have been shown through lab experiments and literature analyses. But do they matter for ecology and biogeochemistry on the global scale? 

22 NOV

How does the trait distribution change between oligotrophic and eutrophic pelagic ecosystems?

When we look at nutrient poor (oligotrophic) and nutrient rich (eutrophic) ecosystem, we generally observe different species. We can therefore conclude that these ecosystems are fundamentally different. However, how do the main functional traits of those species vary between the oligotrophic and eutrophic ecosystems?

13 AUG

The trait based approach to Ocean Ecology

Marine ecosystems are overwhelmingly complex. The trait-based method offers a simple way to describe, model, and understand complex marine systems. In a new paper we describe the approach taken by the Centre for Ocean life and illustrate it with examples from our recent work.

06 MAR

Calanus hyperboreus and the lipid pump

A new Ocean Life paper shows that overwintering of the copepod Calanus hyperboreus contributes significantly to the sequestration of carbon.  We propose a general method, based on metabolic theory, as to how a global inventory can be built for observation-poor species in other parts of the world’s oceans.

06 MAR

Trophic trait coupling and seasonal succession in plankton

In a new paper we reveal how the seasonal succession within plankton communities can be characterized in terms of a few key traits that govern the shifting trophic arrangements within the plankton community.

03 SEP

Thermal traits of fish eggs indicate vulnerability of different species and stocks to climate change – new paper.

We conducted a meta-analysis to investigate and compare responses of development time, cumulative degree-days and survival of fish eggs from 32 populations of 17 species in the North Atlantic to different temperatures in order to determine potential consequences of global warming for these species. We demonstrate that present day temperatures...

03 JUL

Life history theory reveals trade-offs in reproductive traits across fish species

New study from the Centre for Ocean Life, DTU Aqua determines the empirical relationship between fish size at maturity, fecundity and spawning type in fish stocks from temperate-boreal environments

Fisheries and fish stocks Marine research
14 JUN

Life history theory reveals trade-offs reproductive traits across fish species

In a new Ocean Life paper, we examine life history traits of fish, and find a consistent empirical relationship between size at maturity, fecundity and spawning type in 29 stocks of bony fish species from temperate-boreal environments.

Photo: Mikal Schlosser
19 APR

Cod unaffected by new laser camera

A 3D-camera based on laser light can see through the murky conditions beneath the waves. DTU have tested cod to see whether they are irritated by being filmed.

Fisheries and fish stocks Lasers
18 JAN

New Ocean Life paper estimates the contribution of vertically migrating zooplankton to the global carbon export flux via...

PhD student Agnethe N. Hansen has recently published a paper in Limnology and Oceanography on the optimal diel vertical migration of zooplankton and its consequences for the global oceanic carbon pump.
22 OCTOBER 2020