Ocean Ecosystems

WELCOME TO OUR RESEARCH DEPARTMENT ! 

(group head: Prof. Dr. Ir. Hein J.W. de Baar)

The General research aim of the Department of Ocean Ecosystems is to unravel bottom-up and top-down control of marine biological productivity and community structure. Emphasis is on marine elemental and energy flows in the context of global climate change, notably in polar regions. At present our research foci include: invasion of antropogenic carbon dioxide in the oceans, climate change effects on marine productivity and diversity, and functional morphology of marine animals. Our research is both field and lab oriented. Field campaigns include oceanographic cruises to the open oceans, as well as land-based coastal studies in polar and temperate regions. Our extensive experimental facilities allow for climate change simulations with marine microalgae, as well as advanced laser-setups to study the interaction between marine animals and their physical environment. At present, we are furthermore developing larger scale culture facilities with a eye towards future applications of marine algal products, Our staff and project researchers include chemical, physical and biological oceanographers, whereas in the latter group zoologists, microbiologists, physiologists and molecular biologists are active. Below we give a short introduction to our five research themes. If you want more information about one of these themes, use the link at the end of each theme description.

1. Marine Biosphere – Atmosphere Interactions. Marine plankton ecosystems play a key role in the global geochemical cycles of elements relevant to climate. Fluxes of CO₂ and cloud-inducing DMS are mediated through the plankton of seas and oceans. In the year 2050 the CO₂ in atmosphere as well as surface waters of the ocean will be doubled compared to the pre-industrial era. The ensuing shifts in pH down by 0.3-0.4 units and carbonate ion concentration, becoming only half of its original value, are thought to affect marine photosynthesis as well as calcification. For calcifying coccolithophorideae (and for that matter coral reefs as well) deficiencies in calcification have already been shown experimentally. For other taxa such as diatoms and Phaeocystis spp., research has yet to begin. We grow key phytoplankton species under controlled conditions of low, moderate, modern and high CO₂ representing the Last Glacial Maximum, the pre-industrial Holocene, the modern Antropocene and the future high-CO2 ocean. Experiments for single species in the home laboratory are combined with shipboard mesocosm studies of natural plankton assemblages. Long term measurements of CO ₂ fluxes are performed in the Dutch Wadden and North Sea, the Ems Dollard Estuary and the Atlantic Ocean.

For more information on this research theme and current projects, click here.

2. Ecophysiology of Marine Phytoplankton. The microscopic marine algae, floating in the surface layers of our oceans, - also called the phytoplankton-, convert approximately 40% of global CO₂ into organic matter. These organisms therefore play an essential role in global carbon cycling and climate. Furthermore, photosynthesis by unicellular algae forms the basic process of open ocean ecosystems, providing nutrition for all higher trophic levels. The wax and wane of phytoplankton blooms is governed by bottom-up (physical and chemical environmental characteristics) and top-down control (grazing by zooplankton, krill, salps and fish). Climate change causes increasing or decreasing sea surface temperatures depending on the region. Partly related to this, either increased thermal stratification or increased wind-driven vertical mixing is expected. In coastal polar regions, local warming causes enhanced glacial melting and land run-off, thereby affecting coastal productivity due to changing salinity, water column stability and water turbidity. At the same time continuing stratospheric ozone depletion causes enhanced incident ultraviolet-B radiation in polar and temperate regions. The photobiology of marine phyto- and bacterioplankton, especially related with climate change, is studied in our lab since a few decades. Consequences of a changing light climate (irradiance levels as well as dynamics), in synergy or antagony with other forcings (temperature, nutrients) on microalgae are studied in various ocean regions.   

In addition, direct and indirect effects of temperature and irradiance changes on bacterial activity and diversity are studied. Regular field campaigns (Antarctic, Arctic, North and South Atlantic) are supplemented with fundamental studies on photoacclimation potential of microalgae and (autotrophic) bacteria, notably species-specific differences, dynamics of damage, and defense induction against excess irradiance. Harmful algae are of particular interest, including the abundant and bloom forming Phaeocystis and the ichthyotoxic raphydophyte Fibrocapsa japonica. Finally, marine microalgae synthesize a variety of compounds that are beneficial to humans, such as pigments, antioxidants, polyunsaturated fatty acids and biogenic silica.Species specific product variability and growth optimization of golden-brown marine microalgae is investigated under controlled laboratory conditions, with an eye towards future algal applications.  

For more information on this research theme and current projects, click here.

3. Energetics and Behavioural Mechanics of Marine Animals . Physical interactions between marine animals and water, substrate and air determine the energetics of locomotion, acquisition of food and reproduction. Energetic costs of dominant behaviour of important species can be determined by studying the interaction between animals and their direct environment in detail. The way that physical constraints affect and determine behavioural performance i.e. during locomotion and the acquisition of food in the marine pelagic realm, is studied and mapped. We focus on the most abundant species and strive for results that can be used in ecosystem models. Novel areas such as filter feeding with actively moving filters that operate partly in the viscous and partly in inertial regimes, are explored and investigated. Another novel project is on the role of volatile chemicals (e.g. DMS) as odour sources in bi-trophic and tri-trophic interactions in marine zoo- and phytoplankton. Results so far already changed insights in the complex interactions among trophic levels. This may have serious implications for understanding the role of volatile marine chemicals in global processes. See also below under trophic interactions

For more information on this research theme and current projects, click here.

4. Marine trophic interactions The structure, functional diversity and stability of pelagic ecosystems is an intriguing fundamental research topic. Moreover it needs to be understood in order to assess the ecosystems responses to climatic and anthropogenic forcing, their effects on global biogeochemistry, and their response to shifts in commercial fish stocks. Within an end-to-end ecosystem approach (from abiotic forcings and viruses to whales) the new paradigm is that the micro- and mesozooplankton and very small fish are the pivotal trophic levels. Their role in grazing top-down control of the algae includes the shifts up and down between a background microbial loop system (bacteria, viruses, small herbivores) and a classical foodweb plankton bloom. Planktonic carnivores have dualistic effects on fish stocks, by predation mortality of fish larvae as well as by serving as food substrate for mature fish. Throughout the trophic interactions there are various effects of temperature, both directly on the rate of cellular processes, and indirectly e.g. via stratification of the upper ocean euphotic zone. For example, several recent findings show that global warming causes mismatches between trophic levels, i.e. the life cycle stages of pivotal zooplankton taxa get out of phase with on the one hand seasonal blooming of algae, and on the other hand the life cycle stages of key commercial fish species. Our major activities include various lines of experimental research at the multi-species or community level, e.g. specific algal blooms directly harmful for specific zooplankton or fish, or chemical signalling between phyto-and zooplankton. Part of our research is executed in the context of integrated ecosystem simulation modeling within the EU Network of Excellence EUROCEANS.

For more information on this research theme and current projects, click here.

5. Marine Polar Ecosystems . The Polar oceans, are relatively unknown territory still awaiting discovery and unraveling of their ecosystem functioning. Moreover both regions are vulnerable to global climate change, where the predicted, if not already ongoing, ecosystem shifts are to be documented and understood, also with an eye to sustainability of highest trophic levels including whales and indigenous high-Arctic peoples. With an ice-covered Antarctic continent virtually without plant growth, the microscopic algae in the Southern Ocean and sea-ice are the sole base of the complete foodweb up to seabirds, leopard seals and whales. Marine productivity in the Southern Ocean is also vital to the global climate system by controling CO₂ budgets and DMS emissions. At present, prominent and irreversible climate change effects are observed in both polar regions. The dramatic temperature increases in the Artic and regionally in the Antarctic cause strong reductions in sea ice extent. Other factors include changes in mean wind patterns, increased meld water input, stratospheric ozone depletion and ocean acidification. These changes will alter polar ecosystem structure, functioning and C-cycling through all trophic levels. Within this research Theme, components of the other themes (notably 1,2 and 4) are integrated.

For more information on this research theme and current projects, click here.

Education

A few years ago, the former Department of Marine Biology split up into two dynamic research Departments: the Department of Marine Benthic Ecology and Evolution (www.marbee.fmns.rug.nl) and our Department of Ocean Ecosystems (OE). Within the Center for Ecological and Evolutionary Studies (CEES), these two research departments jointly organize the well established Marine Biological Education Program on Bachelor and Master levels.

For information on the Marine Biology Education program, click here

For information on Marine Biology/Ocean Ecosystems Master projects, click here.

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