Driven to distraction? Behavioural impacts of anthropogenic noise on the European hermit crab Pagurus bernhardus from individual to group level

Human activities are altering the planet at an unprecedented scale and pace, ranging from effects on global systems such as climate and carbon cycles to localised but globally wide-spread exposure to anthropogenic pollution such as noise. Anthropogenic noise is an example of human-induced rapid environmental change (HIREC) which can mask, distract and disrupt natural stimuli and sensory-cognitive processes. Since HIREC can alter the sensory environment of animals, and how they detect and process information from their biotic and abiotic environment to make accurate decisions, this process has been termed sensory pollution. While growing evidence shows detrimental effects on across taxa, behavioural contexts and situations, invertebrates are understudied despite contributing to global faunal biodiversity to a vastly greater extent than vertebrate animals. In this thesis, I study how anthropogenic noise as a form of HIREC affects a marine crustacean using the European hermit crab Pagurus bernhardus as a model organism. For hermit crabs, empty gastropod shells are a crucial resource affecting growth, reproduction and survival. Crabs are known to have a preferred, optimal shell weight (% PSW) relating the occupied shell weight to the crab’s own body weight but the shell size they occupy in nature can diverge from the optimal shell size. First, I exposed hermit crabs over 10 days to low-intensity ship noise playbacks (chapter 2). The sound treatment had no effect on assessment behaviour until the last day of the experiment whereby individuals under noise showed longer latency to assess the new, optimal shell. Crabs in small shells under the noise treatment accepted the new shell more frequently than crabs under ambient sound. This pattern was reversed for crabs in larger shells. This experiment suggests that properties of anthropogenic noise beyond the intensity affect animals. Besides the noise effects, I show that shell assessment is a repeatable behaviour. Next, I demonstrate that the effects of noise are modulated by natural factors (chapter 3). I exposed hermit crabs not only to noise and different sized shells but also to a visual predator cue of the common shore crab Carcinus maenas. Overall, the interaction between noise, predator presence and shell size influenced the mean duration for the final decision to accept or reject the optimal shell. Hermit crabs in shells of 50% optimal size took less time for their final decision when exposed to both ship noise and predator cue while crabs in shells of 80% optimal size showed shorter decision time only when the predator cue was absent. Moreover, crabs are less likely to accept an optimal shell in the presence of ship noise, suggesting that exposure to ship noise disrupted the information gathering ability of the crabs. In addition to the noise effects on solitary animals, I examined its effects on intraspecific behavioural interactions (chapter 4 and 5). Under ambient sound, crabs in optimal shells spent most of their time close to a single crab and crabs in suboptimal shells showed no clear preference. Under ship noise, however, this pattern was reversed (chapter 3). Furthermore, noise reduced the aggregated benefit of the arrival of a new shell resource unit to a group of crabs exposed to noise for 24 h (chapter 5) showing that noise effects can accumulate over time. After crabs have been exposed to noise for 24 h I measured the direct effects on their oxygen consumption. In addition, I accounted for the influence of the % PSW of the occupied shell on the oxygen consumption of crabs. Since crabs obtained those shells during the 24 h group process under ship noise (chapter 5), this measure allows to quantify the indirect physiological costs of decisions made under noise (chapter 6). While there was no direct effect of the sound treatment on oxygen consumption, crabs in shells that were too small in relation to their body size had a higher oxygen consumption than hermit crabs in shells closer to the optimal size. Finally, in a field experiment, I found that the mean startle response duration increased with observation number and that the mean startle response duration was repeatable over the observation period. There was no effect of ship noise, presumably because other natural factors such as wind and water turbulence overrode the effects of noise exposure. My results indicate that noise affects shell assessment decisions and that the effects can be modulated by natural factors such as predation threat, resource quality and potentially abiotic variables. This suggests that noise can disrupt across multiple sensory channels. In addition, noise can alter not only individual behaviour but the disruption of individual decisions go beyond a single exposure and scaled up to population levels. I discuss the implications of my findings and suggest avenues for future research to gain a more complete picture of the effects of anthropogenic noise on animals.European CommissionUniversity of Plymout

Artificial light at night reverses monthly foraging pattern under simulated moonlight

Mounting evidence shows that artificial light at night (ALAN) alters biological processes across levels of organization, from cells to communities. Yet, the combined impacts of ALAN and natural sources of night-time illumination remain little explored. This is in part due the lack of accurate simulations of the complex changes moonlight intensity, timing and spectra throughout a single night and lunar cycles in laboratory experiments. We custom-built a novel system to simulate natural patterns of moonlight to test how different ALAN intensities affect predator–prey relationships over the full lunar cycle. Exposure to high intensity ALAN (10 and 50 lx) reversed the natural lunar-guided foraging pattern by the gastropod mesopredator Nucella lapillus on its prey Semibalanus balanoides. Foraging decreased during brighter moonlight in naturally lit conditions. When exposed to high intensity ALAN, foraging increased with brighter moonlight. Low intensity ALAN (0.1 and 0.5 lx) had no impact on foraging. Our results show that ALAN alters the foraging pattern guided by changes in moonlight brightness. ALAN impacts on ecosystems can depend on lunar light cycles. Accurate simulations of night-time light cycle will warrant more realistic insights into ALAN impacts and also facilitate advances in fundamental night-time ecology and chronobiology

Artificial light at night alters predation on colour-polymorphic camouflaged prey

Artificial light at night (ALAN) disrupts biological processes across taxa and at all levels of organisation. Despite growing interest in this globally pervasive sensory pollutant, its impact on colour-guided processes remains largely unexplored. This is especially concerning given the rapid transition in recent years away from narrow-spectrum lighting and towards broad-spectrum options such as white LEDs, which are rich in the short wavelengths of light to which many taxa are particularly sensitive. Camouflage is particularly likely to be disrupted by broader spectra of ALAN due to changes in conspicuousness in background matching prey, which may alter prey recognition in visually guided predators. We simulated natural intensities of moonlight with and without ALAN, using both broad-spectrum (‘white’) ALAN and ALAN filtered to remove the characteristic short (blue) wavelength peak of broad-spectrum LEDs to test whether filtering might mitigate their effects. We tested how exposure to these light treatments impacted predator-prey interactions, using the intertidal crab Carcinus maenas and contrasting colour morphs of the colour-polymorphic snail Littorina obtusata as a model system. Exposure to broad-spectrum ALAN reduced overall predation and reversed the pattern of colour-based prey selection observed under control conditions. Snails were 55% less likely to be attacked under broad-spectrum ALAN than in control conditions, with likelihood decreasing over 70% for yellow snails. Yellow snails were over 26% more likely to be attacked than brown ones under control conditions, but brown snails were over 40% more likely to be attacked than yellow ones under broad-spectrum ALAN. Exposure to filtered ALAN removed any significant colour-based difference in prey recognition. Our results demonstrate that spectral composition is a crucial aspect of ALAN as a sensory pollutant, capable of instigating profound changes in predator-prey interactions that could drive changes in population demography and increase morphological homogeneity in species that depend on colour polymorphism for camouflage

Disruption of marine habitats by artificial light at night from global coastal megacities

Half of globally significant megacities are situated near the coast, exposing urban marine ecosystems to multiple stressors such as waste-water discharge containing a host of organic and inorganic pollutants, air and noise pollution. In addition to these well recognized sources, artificial light at night (ALAN) pollution is inseparable from cities but poorly quantified in marine ecosystems to date. We have developed a time- and wavelength-resolving hydrological optical model that includes solar (daylight and twilight components), lunar and ALAN source terms and propagates these spectrally through a tidally varying water column using Beer’s Law. Our model shows that for 8 globally distributed cities surface ALAN dosages are up to a factor of 6 greater than moonlight, as ALAN intensities vary little throughout the night, over monthly or seasonal cycles. Moonlight only exceeds ALAN irradiances over the ±3-day period around full moon, and particularly during the brightest moons (mid-latitude winter, at zenith). Unlike the relatively stable surface ALAN, underwater ALAN varies spectrally and in magnitude throughout the night due to tidal cycles. The extent of ALAN in-water attenuation is location-specific, driven by the season, tidal range and cycle, and water clarity. This work highlights that marine ALAN ecosystem pollution is a particularly acute global change issue near some of the largest cities in the world

Influence of High, Disperse API Load on Properties along the Fused-Layer Modeling Process Chain of Solid Dosage Forms

In order to cope with the increasing number of multimorbid patients due to demographic changes, individualized polypill solutions must be developed. One promising tool is fused layer modeling (FLM) of dosage forms with patient-specific dose combinations and release individualization. As there are few approaches reported that systematically investigate the influence of high disperse active pharmaceutical ingredient (API) loads in filaments needed for FLM, this was the focus for the present study. Different filaments based on polyethylene oxide and hypromellose (HPMC) with different loads of theophylline as model API (up to 50 wt.%) were extruded with a twin-screw extruder and printed to dosage forms. Along the process chain, the following parameters were investigated: particle size and shape of theophylline; mechanical properties, microstructure, mass and content uniformity of filaments as well as dosage forms and the theophylline release from selected dosage forms. Especially for HPMC, increasing theophylline load enhanced the flexural strength of filaments whilst the FLM accuracy decreased inducing defects in microstructure. Theophylline load had no significant effect on the dissolution profile of HPMC-based dosage forms. Therefore, a thorough analysis of particle-induced effects is necessary to correlate mechanical properties of filaments, printability, and the dosage-and-release profile adjustment

Biologically important artificial Light at night on the seafloor

Accelerating coastal development is increasing the exposure of marine ecosystems to nighttime light pollution, but is anthropogenic light reaching the seafloor in sufficient quantities to have ecological impacts? Using a combination of mapping, and radiative transfer modelling utilising in situ measurements of optical seawater properties, we quantified artificial light exposure at the sea surface, beneath the sea surface, and at the sea floor of an urbanised temperate estuary bordered by an LED lit city. Up to 76% of the three-dimensional seafloor area was exposed to biologically important light pollution. Exposure to green wavelengths was highest, while exposure to red wavelengths was nominal. We conclude that light pollution from coastal cities is likely having deleterious impacts on seafloor ecosystems which provide vital ecosystem services. A comprehensive understanding of these impacts is urgently needed

A global atlas of artificial light at night under the sea

The impacts of artificial light at night (ALAN) on marine ecosystems have emerged as a focus for ecological light pollution research in recent years, yet the global prevalence of ALAN in underwater marine ecosystems is unknown. We have derived a global atlas of ALAN throughout the marine water column that will accelerate our understanding of its sources and environmental impacts. At a depth of 1 m, 1.9 million km2 of the world’s coastal seas are exposed to biologically important ALAN, which equates to around 3.1% of the global exclusive economic zones.This area decreases to 1.6 million km2 (2.7%) at a depth of 10 m, and to 840,000 km2 (1.4%) at 20 m.The most heavily exposed regions are those that experience intensive offshore development in addition to coastal urbanization.The atlas highlights that ALAN as a global change issue is not exclusive to land but is also widespread in the world’s underwater habitats at irradiances that elicit biological responses in marine organisms