North Sea fisheries show a preference for unusual habitats

New paper published in PlosOne!
A broad analysis of three types of fishing – beam trawling for sole, beam trawling for plaice and otter fishing for Nordic lobster and flatfish – has shown that fisheries frequent very specific habitats in the North Sea. Researchers from the University of Groningen (UG) and Wageningen Marine Research (WMR) published on this topic in the academic journal PLOS One on 18 December. There are just a few habitats in the North Sea that are exploited intensively by fisheries. The majority of these so-called hotspots lie within ‘Natura 2000’ areas, as they are also very valuable for nature.

This study, conducted within the collaborative project DISCLOSE, provides the very first insight into the ecological characteristics of different habitats that are targeted by fisheries in the North Sea. The results emphasize that the fishing pressure on the seabed is not uniformly spread across the North Sea. Fishing hotspots are characterized by a combination of specific environmental characteristics that are possibly very important for nature. This could lead to a conflict of interests. The current regulations do not account for this information.

No big blue lake

On most topographical maps, the North Sea is displayed as a big blue lake, but in reality, it accommodates a variety of sea landscapes. These include, among others, a landscape that was drowned following the last ice age and further shaped by tides, currents and waves. Underwater sand dunes, vast mud planes, flooded deltas such as the Klaverbank and high ‘underwater moraines’ such as the Doggersbank dominate these sea landscapes. By looking at these sorts of structures and the surrounding relief, nine sea landscapes in the southern and central North Sea (see figure: Sea landscapes) were be typified in this study. All of these landscapes in turn have their own specific gradients of environmental variables, such as water depth, temperature, salinity and substrate.

North Sea seascapes

Fishing at the landscape scale

This research looks at how the Dutch North Sea fisheries use these landscapes. An analysis of the satellite position data of the three most important types of Dutch fisheries shows clear ‘fishing hotspots’ – spots that are intensively fished every year (see figure: Fishing hotspots). Some of these hotspots lie in the Dutch exclusive economic zone (EEZ), and one part lies in the EEZ of the United Kingdom, Belgium, Germany and Denmark. By connecting the locations of these hotspots to their environmental factors, the habitats in which the fisheries are most active as well as the ecological characteristics of these preferred spots were deduced. In addition, the study investigates how general the spots with these characteristics are.

Very exact
Head researcher Karin van der Reijden from the UG: ‘The hotspot analysis demonstrated that the three types of fishing studied at different locations in the North Sea are each conducted under unique circumstances. Sole fisheries are active in the southern North Sea, especially in the deeper troughs between the large sand banks. Nordic lobsters are actively fished in the muddiest areas, in the deeper parts of the Dutch part of the North Sea. The plaice fisheries fish more broadly, but still prefer the tops of sand waves, situated on the sides of the Doggersbank, for example.’

These specific preferences are connected to the occurrence of the target species of these fisheries: sole, plaice and lobster. The fisheries know precisely which parts of the sea landscapes they must visit in order to find the right species – and therefore, they indirectly know the environmental variables that these species prefer.

fisheries hotspots
Fisheries hotspots (Dutch fishermen) in the North Sea. Tong = sole, Schol = plaice, Kreeft = lobster

Goal-oriented protection of underwater landscapes

This study has demonstrated that sea landscapes are not all used in the same manner by fisheries and that most fishing hotspots are located in fairly rare habitats, with possibly a specific wealth of marine life. The expectation of rich marine life in exactly these areas was not studied but is supported by the fact that multiple fishing hotspots lie within the bounds of ‘Natura 2000’, a European network of protected habitats. This hotspot study creates an improved knowledge base for the weighing of interests, namely the protection of nature and fishing, as part of the sustainable management of the North Sea.

Publication: Van der Reijden K.J., Hintzen N.T., Govers L.L., Rijnsdorp A.D., Olff H. (2018); North Sea demersal fisheries prefer specific benthic habitats. Plos One, DOI:10.1371/journal.pone.0208338 –


Griend research in the spotlight

My current research project that follows the development of the restored Wadden Sea Island Griend, received quite some media attention last week and this week.

The island of Griend after restoration measures in September 2016 (c) the Fieldwork Company

The project covers 4 research topics: 1) geomorphological development of the island, 2) connectivity between mudflats and the island, 3) breeding ecology of endangered sandwich terns and 4) the importance of Griend for sanderlings and other wading birds. The latter topic is covered by my colleague and PhD-student Emma Penning and I cover the first three topic with the support of many colleagues. More information on this project can be found on my (Dutch) blog

The story of Griend and the research on Griend – which is an uninhabited nature reserve – was covered by multiple journalists and even featured in the national television news (NOS 20h journaal) on September 1st. A list of news items on my research – in Dutch – can be found below.

Trouw: De mossel moet dit vogeleiland redden

Vroege Vogels televisie: Vogelparadijs Griend

Nederlands Dagblad: Griend kan niet zonder hulp

Vroege Vogels Radio: Onderzoek en herstel van vogeleiland Griend

NOS 20u journaal 1 september (laatste item)

NPO radio 1: Onderzoek op Griend

2017-09-01 21.05.26
Explaining about my research in a national television news item

VENI grant awarded

I am happy to announce that I was awarded a competitive VENI-grant for young researchers by the Netherlands Organization for Scientific Research (NWO)! Only 154 young researchers from across all research fields received such a grant this year so I am very happy to be one of them.

My project aims to bring further advancement in the relatively unexplored field of marine disease ecology, see the short summary (for a broader audience), below.

The project will start in 2018 and I will keep you up to date of the findings on this website.

Global change and marine plant diseases
Dr. L.L. (Laura) Govers (v), RUG – GELIFES
Higher marine plants form the foundation of many coastal ecosystems. These economic and ecological valuable habitats are globally declining, with a yet unclear role of plant diseases. The project will unravel the effect of global change on newly-found Phytophthora infection of seagrasses and its consequences for coastal conservation and restoration.

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Seagrass water mold can be treated

We have discovered a method to treat seagrass seed used for restoration against water mold (Phytophthora species). Our previous research showed that these water molds, which are related to potato blight, can infect seagrass seeds and thereby limit seed germination. Infection by these aquatic pseudo-fungi and related seed loss has important consequences for worldwide seagrass restoration. Today, we publish a method to successfully treat eelgrass seeds (Zostera marina) for water mold infection and thus to improve seagrass restoration in Scientific Reports.

Effects of infection on cotyledon coloration: a) non-infected seeds germinate green and b) infected seeds germinate brown and stop developing.

Seagrass restoration

Seagrass beds are among the most rapid disappearing ecosystems in the world with a yearly loss rate of about 7%. To halt and revert these losses, there are many attempts to restore these underwater meadows all across the globe. Seagrass beds promote biodiversity and contribute to coastal protection by wave attenuation and formation of anti-erosional mats. We are currently investigating the potential for seagrass restoration in the Dutch Wadden Sea and Delta (Grevelingen). Restoration projects worldwide use a suite of techniques including planting shoots or seedlings, transplantations of sods or using seeds. The latter method is becoming increasingly popular as this method enables cost-effective large-scale restoration and allows for maintaining high genetic diversity. However, infection by water molds (Phytophthora and Halophytophthora species) was still limiting seed-based restoration success due to high seed losses. That’s why we developed a method to treat seeds that are stored overwinter for restoration purposes.

Copper is the key to…

We are happy to report that we have found a successful disinfection method. We tried to different treatments: using copper sulfate in different concentrations and salinity treatments. Copper sulfate is also used in aquaria to treat fungal infections of fish and copper-compounds are also being used in agriculture (incl. organic) to treat water mold. Copper sulfate was indeed very effective, reducing infection with 86% already at concentrations as low as 0.2 ppm. Although overdosing of copper-containing fungicides is a serious problem in agriculture, the concentrations that we used are also found in potable water flowing through copper water pipes and are 25,000 x lower than concentrations generally found in agriculture. This method is currently applied to treat seeds that are currently stored and will be seeded in spring. Through this, we hope to reduced seed loss due to infection with about 40%, hopefully improving seagrass restoration success.

Read the full publication here

New paper in Proceedings B released last Wednesday

Restoration of seagrass beds threatened by family member potato blight

We discovered that two family members of the potato blight – Phytophthora gemini and Halophytophthora sp. Zostera – strongly reduce germination of seagrass seeds. These two pathogens are new to seagrasses and discovered as a result of disappointing results in seagrass restoration experiments in the Dutch Wadden Sea. Additional research showed that these pathogens not only inhabit Dutch waters, but are also present in many other seagrass beds throughout Europe and even in the US. This means that seagrass restoration by seeds is threatened on a global scale.

 Potato Blight

The most infamous member of the Phytophthora-family, Phytophthora infestans causes late blight in potatoes. This vigorous pathogen causes billions of euros of damage to European agricultural crops and affected 1million Irish due during the great famine in 19th century Ireland. Other family members also affect natural ecosystems, such as Californian oak forests and Australian heathland. In total, about 100 species are known from this family, mostly pathogenic to terrestrial plants. Surprisingly little is known about Phytophthora species in seawater, although marine plants such as seagrasses, mangroves and salt marsh plants form the foundation of many coastal ecosystems. Today, an international team, led by us published a study showing the danger of marine Phytophthora species to seagrasses. The study is published in a renowned journal, Proceedings of the Royal Society B.

 Infected seagrass seeds

Researchers collected seagrass seed material from five European countries (the Netherlands, Germany, Denmark, Sweden, France) and from Chesapeake Bay in the US. Seed from all locations appeared to be infected by either a Phytophthora species or related Halophytophthora species, which, up to now, were only known as a plant decomposer on dead mangrove leaves. Principal Investigator, Laura Govers (Radboud University, University of Groningen) explains: “In a lab experiment we subsequently tested germination of infected seeds. Infected seeds showed 6x reduced germination and only 3-4% of all infected seeds germinated.”

Seagrass restoration

Vegetated coastal ecosystems are rapidly disappearing on a global scale. The Dutch Wadden Sea once harbored vast subtidal seagrass meadows (150 km2) that have completely disappeared after the 1930s and have never recovered. These meadows highly contributed to local biodiversity and functioned as nurseries for herring and anchovies. They also provided coastal protection by wave attenuation and by preventing sediment erosion through root mat formation. Therefore, restoration efforts are trying to restore Dutch seagrass beds. Currently, seed material from the German barrier island Sylt is being used for restoration and almost 100% of all seeds is infected by Phytophthora. Thus, researchers are now looking for a solution to reduce infection in order to improve restoration success.

This study is the result of a collaboration between Radboud University, University of Groningen, Royal Netherlands Institute for Sea Research (NIOZ), the Dutch Food and Safety Authority (NVWA), the Fieldwork Company and the Virginia Institute of Marine Science. The study was funded by Natuurmonumenten, Rijkswaterstaat and the Dutch Food and Safety authority (NVWA).


Halophytophthora sp. Kers (c) Johan Meffert
Halophytophthora isolated from seagrass seed



Knooppunt Waddenzee

I am happy to announce a popular scientific book that I recently co-authored: Knooppunt Waddenzee. For the time being, it is only available in Dutch but the title translates as ‘Wadden Sea Hub’. The book presents the results of a large Wadden Sea project to a broader audience; it tells the stories of five migratory bird species that are using the Wadden Sea as a stopover on their annual migration routes. This involves the stories of the red knot, a molluscivore wader, the bar-tailed godwit, a worm-eater, the brent goose, a herbivore with a preference for seagrass, the sanderling that also lives on beaches (all over the world) and the iconic spoonbill. “Knooppunt Wadden Sea” also formulates tools for management in order to better protect both these species AND the habitats they are using. We conclude that the Wadden Sea should be studied and protected in  an international context since birds (and fish) connect the Wadden Sea to both the Arctic and Africa. If you’re interested, the book can be ordered here (€17.50).


Seagrass-clam partnership enhances resilience of seagrass beds to drought

Today, our new paper on Drought, Mutualism Breakdown, and landscape-scale degradation of seagrass beds is published online in Current Biology!

In this paper, we show that drought, due to climate extremes can trigger landscape-scale seagrass degradation and consequent failure of the facultative feedback between seagrasses and lucinid clams can exacerbate collapse. The study was conducted in the vast intertidal seagrass beds of Banc d’Arguin, Mauritania (West-Africa).

This is the first study that shows how external disturbances may cause sudden breakdown of a facultative marine mutualism.

Read the paper here and on ScienceNews

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New paper in Proceedings B

Today, our new paper is published online on the Proceedings B website. In this paper, we describe how habitat-modifying species in two coastal ecosystems (seagrass beds and salt marshes) not only enhance biodiversity, but also structure and complexity of the food web. This works through facilitation rather than trophic interactions , since habitat-modifying species  provide shelter and suitable attachment sites for other species.

Our work illustrates that not only direct trophic interactions but also non-trophic interactions may shape food webs. Please read our paper here.

This figure illustrates how food webs of finging salt marshes (left) and seagrass beds (right) are structured, also when secondary habitat-modifiers are present (c and f). Node colors represent trophic levels and lines between nodes represent connections between species.