Sander Holthuijsen - Academia.edu (original) (raw)

Papers by Sander Holthuijsen

Cruise report with some preliminary results of the first subtidal sampling campaign covering the ... more Cruise report with some preliminary results of the first subtidal sampling campaign covering the entire Dutch Wadden Sea. The results presented in this cruise report are based on field data.

Remote Sensing in Ecology and Conservation

In soft-bottom marine ecosystems, bedform variation is induced by wind-and tidal-driven hydrodyna... more In soft-bottom marine ecosystems, bedform variation is induced by wind-and tidal-driven hydrodynamics. The resulting megaripples, sand waves and sandbanks form a spatially and temporally heterogeneous seafloor landscape. The strong physical forces imposed by the migration of these bedforms are important determinants for the occurrence of different macrozoobenthic species. Quantifying the effect of these forces can help in differentiating natural-and anthropogenically induced physical stressors. However, large-scale mapping of seabed morphology at high resolution using multibeam echosounder is challenging, costly and time-consuming, especially in shallow seas, prohibiting wide swaths. Instead, their bathymetry is typically studied using single-beam transects that are interpolated to bathymetric grids with a relatively coarse resolution (20 m). However, this leaves out information on smaller scale (<20 m) bedforms that can be ecologically relevant. In the Dutch Wadden sea, a shallow tidal system, we characterized bedform variation at high resolution using single-beam data for the first time. We calculated a 2-D Terrain Ruggedness Index (TRI) at sub-meter resolution along the single-beam transects and interpolated the results to a full 3-D grid. We then validated the result by relating TRI to independently modeled hydrodynamic parameters and to the distribution of macrozoobenthic species. We found that TRI successfully integrates the variation of tidal-driven bed shear stress and wave-driven orbital velocity. In addition, we found TRI to be a good predictor of the occurrence of macrozoobenthic species. The inferred small-scale bedforms provide valuable information for separating the relative importance of natural dynamics versus anthropogenic disturbances such as dredging and bottom trawling activities. We discuss that by repurposing already available single-beam data in this way, bedforms can be characterized at high resolution without the need for additional equipment or mapping campaigns, yielding novel input to decision-making on marine management and conservation.

Tijdens een storm op 1 januari 2019 verloor het containerschip MSC Zoe een deel van haar lading t... more Tijdens een storm op 1 januari 2019 verloor het containerschip MSC Zoe een deel van haar lading ten noorden van de Nederlandse en Duitse Waddeneilanden. In totaal sloegen 342 containers overboord. Een deel van de inhoud kwam in zee terecht, en de volgende dagen spoelde veel materiaal aan op de Waddeneilanden. Hieronder bevonden zich ook grote aantallen drijvende witte plastic pellets van Hoge-Dichtheid-Polyethyleen (HDPE) en bolvormige polystyreen (PS) korreltjes. Rijkswaterstaat Noord-Nederland heeft eind 2019 aan het Koninklijk Nederlands Instituut voor Onderzoek der Zee (NIOZ) en Wageningen Marine Research (WMR) gevraagd, volgende het advies van de Waddenacademie (Philippart e.a., 2019) onderzoek te doen naar de (mogelijke) effecten van de door MSC Zoe verloren materialen op het ecosysteem met een speciale focus op de microplastics, en op de Nederlandse Waddenzee. Dit rapport beschrijft de resultaten van dit onderzoek. Er is gebruik gemaakt van extra monsters genomen tijdens best...

The sensitivity analysis in this study showed that our statistical approach has the power to dete... more The sensitivity analysis in this study showed that our statistical approach has the power to detect changes in macrobenthos abundance. The results from our approach highlighted that total biomass differed, and tended to be lower, in Zuidwal and Groningen, the two areas where production has taken place the longest. In total ten of 76 species showed differences in the IN areas, and most differences tended to be positive. Interestingly, most differences in species abundance were observed at Zuidwal; an area of long-term drilling. Continuation of the SIBES monitoring is a cost-effective way to monitor possible effects of gas production, and subsidence, related changes on the core driver of the Wadden Sea food web, i.e. the macrobenthos of the Wadden Sea. Photo 1. The NIOZ research vessel Navicula is used as a base for the SIBES sampling campaign in the summer months.

To investigate potential effects of gas production, via surface sediment subsidence, on the macro... more To investigate potential effects of gas production, via surface sediment subsidence, on the macrobenthos in the East Frisian production area the synoptic intertidal benthic surveys of the Wadden Sea (SIBES) began in 2008. Gas production began in the East Frisian area in 2007. In the East Frisian area the current predicted subsidence effects on the surface are expected to be minimal as underground subsidence is less than 2 cm. Macrobenthos, organisms larger than 1 mm that live in or on the mud, are commonly used as signalling species for anthropogenic driven changes in tidal flat environments. These species are suitable indicators because many species are sedentary and thus cannot escape adverse situations, and also have strong environmental associations, in combination with relatively short lifespans , such that they show relatively fast responses to adverse conditions. Furthermore, because they form the base of the food chain, changes in macrobenthos could affect the upper levels of the food chain. This progress report will provide an assessment of macrobenthos data collected in the 2012 sampling campaign to examine if the abundance of macrobenthos in the area of the East Frisian production area differs from the remainder of the Dutch Wadden Sea. In addition, we will describe the physical environment of this area and the species that occur in this area. We show that the East Frisian area is characterised by relatively fine sediment types (~107 µm) and long exposure times (0.4 fraction of time). Mean total biomass was lower in the East Frisian area compared to the mean total biomass observed across the remainder of the Wadden Sea. By contrast, the mean total abundance of all species was higher in the East Frisian area relative to the mean total abundance observed across the remainder of the Wadden Sea. On average 9 species were observed in a single core in the East Frisian area, compared to an average of 7 species in a core across the remainder of the Wadden Sea. Although these differences were observed, they were not significant indicating that total

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This project has been funded by the Department of Parks and Wildlife partnership with BHP Billito... more This project has been funded by the Department of Parks and Wildlife partnership with BHP Billiton “Eighty Mile Beach and Walyarta Conservation Program”, with in-kind support from NIOZ and Wetland Research & Management This report was produced at the Broome Bird Observatory in late October 2016. Abstract 1. This is a report on repeat surveys on the state of the benthic invertebrates at two internationally important areas of intertidal mudflats in northwest Australia (Roebuck Bay and Eighty Mile Beach) during October 2016. In the period 6-19 October 2016, we mapped the invertebrate macrobenthic animals (those retained by a 1 mm sieve) at the main intertidal sites of West Kimberley, WA: Eighty Mile Beach and Roebuck Bay. We revisited almost the entire intertidal area along Eighty Mile Beach that was ‘benthically’ mapped in October 1999. The benthic animals of the northern mudflats of Roebuck Bay had been mapped in 1997, 2000, 2002, and 2006; we revisited as many as possible of these p...

2. Kansrijke locaties voor mosselen 24 Voorkomen droogvallende schelpdierbanken Nederlandse Wadde... more 2. Kansrijke locaties voor mosselen 24 Voorkomen droogvallende schelpdierbanken Nederlandse Waddenzee 25 Droogvallende schelpdierbanken westelijke Waddenzee 26 Droogvallende schelpdierbanken oostelijke Waddenzee 27 3. Mosselbank herstel experiment 30 3.1. Foto impressie aanleg mosselbanken en kokosmatten 32 3.2. Resultaten restauratie mosselbanken 34 3.3. Resultaten predatie experiment 36 4. Macrozoöbenthos op droogvallende platen (SIBES) 38 4.1. Monstering methodisch 39 4.2. Foto impressie SIBES bemonstering 40 4.3. Biomassa en variatie 42 4.4. Belangrijke soorten uitgelicht-factsheets 46 5. Het belang van mosselbanken voor het voedselweb 68 5.1. Isotoopbemonstering in de Waddenzee 69 5.2. Foto impressie fuikenbemonstering op de wadplaten 72 5.3. Mosselbanken herbergen een hoger aantal soorten dan habitats daarbuiten 73 6. Het belang van droogvallende wadplaten voor het voedselweb 77 6.1. Bemonstering fytoplankton en zoöplankton 78 6.2. Bemonstering kiezelwieren 80 6.3. Resultaten isotoopanalyse 82 6.4. Benthische bijdrage van verschillende soorten 88 6.5. Voedselweb van de Nederlandse Waddenzee op basis van de verzamelde isotoopmonsters 89 7. Conclusie en aanbevelingen 90 8. Referenties 94 Bijlagen 96 Diepte 97 Droogvalduur 98 Zoutgehalte 99 Korrelgrootte van het sediment 100 Kombergingsgebieden en gesloten gebieden 101 Vaarwegen 102 MZI locaties en kweekpercelen 103 Intensiteit garnalenvisserij 104 Handkokkelgebieden 105 Handkokkelgebieden op basis van Nb-wet vergunning 2013.

Biological Conservation, 2016

In conservation strategies of marine ecosystems, priority is given to habitat-structuring foundat... more In conservation strategies of marine ecosystems, priority is given to habitat-structuring foundation species (e.g. seagrasses, mangroves and reef-building corals, shellfish) with the implicit goal to protect or restore associated communities and their interactions. However, the number and accuracy of community level metrics to measure the success of these strategies are limited. Using intertidal shellfish reefs as a model, we tested to what extent foundation species alter community and food web structure, and explored whether basic metrics of food web structure are useful indicators of ecosystem complexity compared to other often-used indices. We found that shellfish reefs strongly modified community and food web structure by modifying habitat conditions (e.g. hydrodynamics, sediment grain size). Stable isotope-based food web reconstruction captured important differences between communities from bare mudflat and shellfish reefs that did not emerge from classic abundance or diversity measures. On shellfish reefs, link density and the number of top predators were consistently higher, while both connectance and the richness of intermediate species was lower. Species richness (+42%), species density (+79%) and total biomass of benthos, fish and birds (+41%) was also higher on shellfish reefs, but this did not affect the Shannon diversity or Evenness. Hence, our results showed that basic food web metrics such as link density and number of top consumers and intermediate species combined with traditional measures of species richness can provide a robust tool to measure conservation and restoration success. We therefore suggest that these metrics are included as Essential Biodiversity Variables (EBV), and implemented as ecosystem health indicators in legislative frameworks such as the Marine Strategy Framework Directive (MSFD).

Behavior has a predictive power that is often underutilized as a tool for signaling ecological ch... more Behavior has a predictive power that is often underutilized as a tool for signaling ecological change. The burrowing behavior of the deposit feeding bivalve Macoma balthica reflects a typical food-safety trade-off. The choice to live close to the sediment surface comes at a risk of predation and is a decision made when predation danger, food intake rates or future fitness prospects are low. In parts of the Dutch Wadden Sea, Macoma populations declined by 90% in the late 1990s, in parallel with large-scale mechanical cockle-dredging activities. During this decline, the burrowing depth of Macoma became shallow and was correlated with the population decline in the following year, indicating that it forecasted population change. Recently, there has been a series of large recruitment events in Macoma. According to the food-safety trade-off, we expected that Macoma should now live deeper, and have a higher body condition. Indeed, we observed that Macoma now lives deeper and that living de...

ABSTRACT To investigate potential effects of gas production, via surface sediment subsidence, on ... more ABSTRACT To investigate potential effects of gas production, via surface sediment subsidence, on the macrobenthos in the East Frisian production area the synoptic intertidal benthic surveys of the Wadden Sea (SIBES) began in 2008. Gas production began in the East Frisian area in 2007. In the East Frisian area the current predicted subsidence effects on the surface are expected to be minimal as underground subsidence is less than 2 cm. Macrobenthos, organisms larger than 1 mm that live in or on the mud, are commonly used as signalling species for anthropogenic driven changes in tidal flat environments. These species are suitable indicators because many species are sedentary and thus cannot escape adverse situations, and also have strong environmental associations, in combination with relatively short life-spans, such that they show relatively fast responses to adverse conditions. Furthermore, because they form the base of the food chain, changes in macrobenthos could affect the upper levels of the food chain. This progress report will provide an assessment of macrobenthos data collected in the 2012 sampling campaign to examine if the abundance of macrobenthos in the area of the East Frisian production area differs from the remainder of the Dutch Wadden Sea. In addition, we will describe the physical environment of this area and the species that occur in this area. We show that the East Frisian area is characterised by relatively fine sediment types (~107 μm) and long exposure times (0.4 fraction of time). Mean total biomass was lower in the East Frisian area compared to the mean total biomass observed across the remainder of the Wadden Sea. By contrast, the mean total abundance of all species was higher in the East Frisian area relative to the mean total abundance observed across the remainder of the Wadden Sea. On average 9 species were observed in a single core in the East Frisian area, compared to an average of 7 species in a core across the remainder of the Wadden Sea. Although these differences were observed, they were not significant indicating that total biomass, total abundance and species richness, as defined by the number of species in a core, were no different in the East Frisian area relative to the natural variation observed across the entire Dutch Wadden Sea. In total twenty species were observed in the East Frisian area. Species like Pygiospio elegans and Macoma balthica were most common. The Monte Carlo analysis showed that species abundances in this area did not differ relative to what one would expect if this area was not affected by gas production.

Remote Sensing in Ecology and Conservation

Biological Conservation, 2016