Marine biologist Dick van Oevelen studies the food web on the floor and in the water column of estuaries and seas, such as the Eastern Scheldt, the Grevelingen and the North Sea. ‘An important theme within these Dutch coastal ecosystems is the presence of oyster reefs with mainly Japanese oysters. Initially, there was considerable uncertainty years ago when it became clear that these exotic oysters could reproduce in our cold climate. Now that picture has become more nuanced. Nevertheless, it is still unclear what the effect of this invasive exotic species is on indigenous shellfish and the rest of the marine life. To better understand this, we place instruments on an oyster reef at low tide. These instruments allow us to measure how much food the shellfish filter from the water and the quantity of nutrients they excrete again during high tide. Determining the consequences of the encroaching Japanese oysters requires a detailed study of these reefs. The same is true for the reattachment of indigenous oyster reefs on the floor of the North Sea because that also has consequences for the ecosystem.’
‘We also measure the food chain in the water column. For decades, zooplankton has been captured from different depths by pulling a fine net through the water. However, this method has many limitations: by definition, you acquire a collection of organisms from different locations and depths, and these organisms are pulled from the water in a “knocked out” state. We can avoid these problems with a brand-new imaging system. With the help of a camera that photographs the organisms of 500 micrometres to 2 centimetres in size several times per second, we can gain an accurate image to the nearest centimetre of which organisms live at a certain depth and how their occurrence relates to environmental conditions. Eventually, we want to have computers automatically classifying these images and save an enormous amount of manpower behind the microscope. Furthermore, with this technique, we can see the organisms “in action” in their natural environment. That means we can also gain an idea of the predator-prey interactions, for example.’
‘I expect that, in the coming years, this imaging system will enable us to add a new dimension to analysing the marine food web. A dimension we could never have investigated using the old methods and mere manpower.’Read more +
I was recently appointed as senior scientist in the Department of Estuarine and Delta Systems, where I will work on new challenges including the nitrogen cycling in mussel and oyster reefs, reef dynamics and the role of zooplankton in the pelagic food web. In the past years, I have applied inverse models to quantify carbon and nitrogen fluxes in marine food webs going from intertidal mudflats, continental shelves and slopes to the abyssal plains. Many of these studies were done in international collaborations within large EU-projects (e.g. HERMES, HERMIONE and CoralFISH. This food web modelling still continues in the deep-sea mining projects MIDAS and "Ecological aspects of deep-sea mining" (JPI-Oceans), in which we try to determine recovery rates of abyssal food webs by combining (historical and novel) field data and modeling. Another prime interest is the functioning of warm- and cold-water coral reefs, which is primarily focussed on the mechanisms that allow these hotspot ecosystems to flourish, including the interaction of hydrodynamics and organic matter transport. Together with my colleagues Prof. dr. Klaas Timmermans and Prof. dr. Tjeerd Bouma, I enjoy teaching the MSc. course Marine Ecosystem Services and Global Change at Groningen University.
Oyster and mussel reefs play a disproportionately large role in organic matter uptake in estuaries due to their high filtration capacity. Yet, the consequences for carbon and in particular nitrogen cycling remain poorly understood. Using a combination of field and laboratory studies using 15N-labelled substrates (NH4 and NO3) we aim to get grip on the nitrogen cycle associated with oyster reefs.
The deep sea harbours one of the most biodiverse ecosystems on our planet: cold-water coral reefs. Like their tropical counterparts, they form structurally complex habitats that support a diverse community. It is still paradoxical how such a rich ecosystem can thrive in an environment that is considered to be food limited. In the EU-project ATLAS and my NWO-VIDI project we target this paradox by an integrated study on the delivery, uptake and processing of organic matter by cold-water coral reef communities.
The deep seafloor is rich in mineral resources that are a target for the mining industry in the near future. These mining operations will generate large scale disturbances at the seafloor with unknown consequences and potentially slow recovery. Within several international projects, we investigate how food web functions are altered using in situ experimentation and food web modeling.
Below a few links to items that have made it to the media on my work:
Find all my publications, including downloadable PDFs, at ResearchGate. Below, I highlight some personal favorites.
Soetaert K, Mohn C, Rengstorf A, Grehan A and Van Oevelen (2016) Ecosystem engineering creates a direct nutritional link between 600-m deep cold-water coral mounds and surface productivity. Scientific Reports 6:35057 full text
Cold-water corals (CWCs) form large mounds on the sea oor that are hotspots of biodiversity in the deep sea, but it remains enigmatic how CWCs can thrive in this food-limited environment. Here, we infer from model simulations that the interaction between tidal currents and CWC-formed mounds induces downwelling events of surface water that brings organic matter to 600-m deep CWCs. This positive feedback between CWC growth on carbonate mounds and enhanced food supply is essential for their sustenance in the deep sea and represents an example of ecosystem engineering of unparalleled magnitude. This ’topographically-enhanced carbon pump’ leaks organic matter that settles at greater depths. The ubiquitous presence of biogenic and geological topographies along ocean margins suggests that carbon sequestration through this pump is of global importance. These results indicate that enhanced strati cation and lower surface productivity, both expected consequences of climate change, may negatively impact the energy balance of CWCs.
Cathalot C, Van Oevelen D, Cox TJS, Kutti T, Lavaleye M, Duineveld G and Meysman FJR (2015) Cold-water coral reefs and adjacent sponge grounds: hotspots of benthic respiration and organic carbon cycling in the deep sea. Frontier in Marine Science 2: full text
Cold-water coral reefs and adjacent sponge grounds are distributed widely in the deep ocean, where only a small fraction of the surface productivity reaches the seafloor as detritus. It remains elusive how these hotspots of biodiversity can thrive in such a food-limited environment, as data on energy flow and organic carbon utilization are critically lacking. Here we report in situ community respiration rates for cold-water coral and sponge ecosystems obtained by the non-invasive aquatic Eddy Correlation technique. Oxygen uptake rates over coral reefs and adjacent sponge grounds in the Træna Coral Field (Norway) were 9–20 times higher than those of the surrounding soft sediments. These high respiration rates indicate strong organic matter consumption, and hence suggest a local focusing onto these ecosystems of the downward flux of organic matter that is exported from the surface ocean. Overall, our results show that coral reefs and adjacent sponge grounds are hotspots of carbon processing in the food-limited deep ocean, and that these deep-sea ecosystems play a more prominent role in marine biogeochemical cycles than previously recognized.
De Goeij JM, D Van Oevelen, MJA Vermeij, R Osinga R, JJ Middelburg, AFPM de Goeij, and W Admiraal (2013) Surviving in a Marine Desert: The Sponge Loop Retains Resources within Coral Reefs. Science 342(6154): 108-110. full text
Ever since Darwin’s early descriptions of coral reefs, scientists have debated how one of the world’s most productive and diverse ecosystems can thrive in the marine equivalent of a desert. It is an enigma how the flux of dissolved organic matter (DOM), the largest resource produced on reefs, is transferred to higher trophic levels. Here we show that sponges make DOM available to fauna by rapidly expelling filter cells as detritus that is subsequently consumed by reef fauna. This “sponge loop” was confirmed in aquarium and in situ food web experiments, using 13C- and 15N-enriched DOM. The DOM-sponge-fauna pathway explains why biological hot spots such as coral reefs persist in oligotrophic seas—the reef’s paradox—and has implications for reef ecosystem functioning and conservation strategies.
Mueller, CE, T Lundalv, JJ Middelburg, and D van Oevelen (2013) The symbiosis between Lophelia pertusa and Eunice norvegica stimulates coral calcification and worm assimilation. Plos One 8:e58660-e58660. full text
The cold-water coral L. pertusa and the polychaete E. norvegica live together in close association. In this paper we show that the association is beneficial for both species involved. Calcification by the coral is enhanced, which increases reef strength and the worm takes up more food. The high worm abundance suggests that this symbiosis has implications for the ecosystem scale.
Van Oevelen D, K Soetaert, CHR Heip. (2012) Carbon flows in the benthic food web of the Porcupine Abyssal Plain: The (un)importance of labile detritus in supporting microbial and faunal carbon demands. Limnology and Oceanography 7(2): 645–664 full text
Pulses of fresh phytodetritus arriving on the deep seafloor are considered an important food source for organisms living there. Here we merged various data sources from the Porcupine Abyssal Plain (4800 m) and arrive at the conclusion that these fresh pulses are not very important in the diets. Instead, the biota still relies largely on detritus already present in the sediment.
Van Oevelen D, GCA Duineveld, MSS Lavaleye, F Mienis, K Soetaert and CHR Heip (2009) The cold-water coral community as hotspot of carbon cycling on continental margins: a food web analysis from Rockall Bank (northeast Atlantic). Limnology and Oceanography 54:1829–1844 full text
Cold-water corals form large carbonate reef structures on the seafloor, that become home to a associated fauna. We knew that this is a diverse faunal community. In this paper, we show for the first time that the biomass and carbon processing acitivity is substantially higher than that of the surrounding sediments. We speculate that this high activity has implications for the surrounding sediments.
Van Oevelen D, K Van den Meersche, F Meysman, K Soetaert, JJ Middelburg and AF Vézina (2010) Quantitative reconstruction of food webs using linear inverse models. Ecosystems 13:32–45 full text
The food web is a cornerstone concept in modern ecology as it describes the exchange of matter among different compartments within an ecosystem. In this paper, we describe a modeling technique to construct a mass-balanced food web model based on all available data.
Van Oevelen D, JJ Middelburg, K Soetaert and L Moodley (2006) The fate of bacterial carbon in an intertidal sediment: Modeling an in situ isotope tracer experiment. Limnology and Oceanography 51:1302-1314 full text
Biogeochemical cycling in most sediments is dominated by heterotrophic bacteria, yet we understand very little of the factors that control bacterial biomass. A this study, we used intepretated data from an stable isotope tracer data with a model experiment and concluded that grazing by fauna represents only a minor fate, instead mortality (e.g. viral lysis) seemed to be the dominant fate of bacterial carbon production.