Biology subjects

Aarts, G.

Publications and source records attributed to Aarts, G..

3 recordsLinked to original sources

bioRxiv2025

In the face of competition, imperfect knowledge can lead to sustainable exploitation of a shared resource.

Overexploitation of a shared resource is a frequent phenomenon among groups of selfish consumers, known as the tragedy of the commons. To avoid "self-damage through self-interest", humans may either defend exclusive access to resources, or collectively adopt advanced cooperative behaviour and carefully designed spatial harvesting strategies to exploit a shared resource sustainably. However, why do many non-human species that are neither social nor territorial also appear to avoid overexploiting resources? This study shows that, even under highly competitive scenarios, cooperation is not necessary to sustainably exploit shared resources if individuals have imperfect knowledge about the distribution of those resources. Poorly informed individuals are more likely to inadvertently exploit resources in peripheral habitats, which may allow for higher resource renewal in the nearby and low-cost habitats, enhancing the sustainability of resource use. As a result, those consumers can achieve a long-term yield that approaches that of cooperative consumers and is higher than omniscient consumers. Ironically, while there might be an evolutionary drive for individuals to make well-informed decisions, consumers of shared resources may be collectively more prosperous when they make decisions based on less information. These findings might explain why apparently sub-optimal consumer behaviour appears so prevalent in nature.

ecology↗

bioRxiv2023

Gas extraction under intertidal mudflats is associated with changes in sediment structure and macrozoobenthic invertebrate communities

O_LIIn intertidal environments, land subsidence may change the local flooding regime and sediment composition, two main drivers of the macrozoobenthic community structure. In the Dutch Wadden Sea, a UNESCO world heritage site, gas extraction has resulted in an average subsidence of up to 2 mm y-1 of intertidal mudflats. These mudflats support a highly productive macrozoobenthic community, which offers important resources for birds and fishes. To what extent land subsidence due to gas extraction affects sediment and macrozoobenthos remains unknown and increasingly important given sea level rise. C_LIO_LITaking advantage of a monitoring program, we evaluated the effect of anthropogenically caused land subsidence on sediment composition and intertidal macrozoobenthos. Nearly 4600 points were sampled yearly (2008-2020) across the Dutch Wadden Sea, allowing us to compare sediment composition and macrozoobenthos biomass within and outside the subsidence area while controlling for the main drivers of these variables. We also compared population trends within and outside the subsidence area for 31 species with different habitat use in terms of depth and sediment composition. C_LIO_LISediment median grain size decreased in the subsided area at 1 {micro}m y-1 while on average remaining constant in other intertidal mudflats. Mud fraction was 3% higher within the subsided area throughout the studied period. This had no effect on the total biomass of macrozoobenthos. The biomass of species that use deeper areas increased within the subsidence area compared to outside, and the opposite was true for species using shallower places, but comparable patterns were also found in an area not affected by subsidence. C_LIO_LIChanges in median grain size could be happening, and minor changes in macrozoobenthic community composition. For a successful implementation of the "hand on the tap" principle in the Wadden Sea, it is necessary to define beforehand the relevant variables that represent the natural values, implement proper monitoring, and define threshold values above which effects are not acceptable. We propose median grain size, mud fraction and macrozoobenthic biomass as good measures of the natural values of the Wadden Sea, and the methods used here as a way for identifying anthropogenic effects on them. C_LI

ecology↗

bioRxiv2018

Harbour seals are regaining top-down control in a coastal ecosystem

Historic hunting has led to severe reductions of many marine mammal species across the globe. After hunting ceased, some populations have recovered to pre-exploitation levels, and may again act as a top-down regulatory force on marine ecosystems. Also the harbour seal population in the international Wadden Sea grew at an exponential rate following a ban on seal hunting in 1960s, and the current number [~]38,000 is close to the historic population size. Here we estimate the impact of the harbour seal predation on the fish community in the Wadden Sea and nearby coastal waters.\n\nFish remains in faecal samples and published estimates on the seals daily energy requirement were used to estimate prey selection and the magnitude of seal consumption. Estimates on prey abundance were derived from demersal fish surveys, and fish growth was estimated using a Dynamic Energy Budget model. GPS tracking provided information on where seals most likely caught their prey.\n\nHarbour seals from the Dutch Wadden Sea fed predominantly on demersal fish, e.g. flatfish species (flounder, sole, plaice, dab), but also sandeel, cod and whiting. Total fish biomass in the Wadden Sea was insufficient to sustain the estimated prey consumption of the entire seal population year-round. This probably explains why seals also acquire prey further offshore in the adjacent North Sea, only spending 13% of their diving time in the Wadden Sea. Still, seal predation was estimated to cause an average annual mortality of 43% and 60% on fish in the Wadden Sea and adjacent coastal zone, respectively. There were however large sources of uncertainty in the estimate, including the migration of fish between the North Sea and Wadden Sea, and catchability estimates of the fish survey sampling gear, particularly for sandeel and other pelagic fish species.\n\nOur estimate suggested a considerable top-down control by harbour seals on demersal fish. However predation by seals may also alleviate density-dependent competition between the remaining fish, increasing fish growth, and partly compensating for the reduction in fish numbers. This study shows that recovering coastal marine mammal populations could potentially become an important component in the functioning of shallow coastal systems.

ecology↗