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Kelp forests occur on more than a quarter of the world's coastlines, serving as foundation species supporting high levels of biodiversity. They are also a major source of organic matter in coastal ecosystems, with the majority of primary production released and exported as detritus. Kelp detritus also provides food and shelter for macroinvertebrates, which comprise important components of inshore food-webs. Hitherto, research on kelp detritus-associated macroinvertebrate assemblages remains relatively limited. We quantified spatiotemporal variability in the structure of detritus-associated macroinvertebrate assemblages within Laminaria hyperborea forests and evaluated the influence of putative drivers of the observed variability in assemblages across eight study sites within four regions of the United Kingdom in May and September 2015. We documented 5167 individuals from 106 taxa with Malacostraca, Gastropoda, Isopoda and Bivalvia the most abundant groups sampled. Assemblage structure varied across months, sites, and regions, with highest richness in September compared to May. Many taxa were unique to individual regions, with few documented in all regions. Finally, key drivers of assemblage structure included detritus tissue nitrogen content, depth, sea surface temperature, light intensity, as well as L. hyperborea canopy density and canopy biomass. Despite their dynamic composition and transient existence, accumulations of L. hyperborea detritus represent valuable repositories of biodiversity and represent an additional kelp forest component which influences secondary productivity, and potentially kelp forest food-web dynamics. • Here we investigated the role of kelp detritus, and understudied habitat compartment within kelp forests, in supporting macroinvertebrate diversity across 9° of latitude. • We found kelp detritus supported high levels of diversity, comparable to other better studied kelp habitat compartments, such as kelp holdfasts, as well as other habitats considered to support high levels of biodiversity such as seagrass meadows. • Key drivers of macrofaunal assemblage structure included detritus tissue nitrogen content, depth, SST, light intensity, as well as L. hyperborea canopy density and canopy biomass. [ABSTRACT FROM AUTHOR]

In order to recruit into adult populations juvenile fish must be able to find food, successfully compete with other organisms and avoid predation within a habitat, in other words they must be able to locate favourable and avoid detrimental conditions. Bio-chemical research into fish detection and discrimination between chemical cues is extensive, however whether olfactory mechanisms are critical in habitat selection and avoidance of detrimental conditions within the marine environment remains under-researched. Despite being one of the scientifically most explored seas, studies on the use of olfactory system in the selection of water masses of the Mediterranean fish species are absent. Using a chemical choice flume, the chemically mediated behaviour choices to distinct chemical cues (algae, seagrass, predator and conspecifics) of Symphodus ocellatus , a common Mediterranean fish, were investigated. In addition to the conventional analysis, which relies on the amount of the time spent in the specific water mass as the main indicator of preference, the behavioural response triggered by the detection of a particular cue was also examined, by analysing the mean and variance of speed of the individual fish movements, a complimentary approach previously not considered in the flume experiments. Bayesian statistical method was used to calculate both, proportion of time spent in the specific water mass, as well as to analyse the behavioural response of each individual within the specific water mass. In terms of the time spent, the flume trials conducted resulted in no significant fish selection preference or avoidance for any of the water masses tested, however varied speeds and number of burst speed movements were observed in a number of trials. When no olfactory stimulus was present, no change in behaviour was triggered. Thus, juvenile S. ocellatus undoubtedly has a capacity of change in behaviour to a complex array of olfactory stimuli, nevertheless the response in the flume experiment was more complex than just the differences in time of the occupancy between the water masses. As a result, the analyses of speed could in future prove to be an important complementary tool for studying behavioural responses of fish using this methodology. The findings are coupled with the development of the rigorous novel protocol for behavioural analyses using exclusively publicly available apparatus and software, all described within the manuscript. [ABSTRACT FROM AUTHOR]

Kelp species function as important foundation organisms in coastal marine ecosystems where they provide biogenic habitat and ameliorate environmental conditions, often facilitating the development of diverse understorey assemblages. The structure of kelp forests is influenced by a variety of environmental factors, changes in which can result in profound shifts in ecological structure and functioning. Intense storm-induced wave action in particular, can severely impact kelp forest ecosystems. Given that storms are anticipated to increase in frequency and intensity in response to anthropogenic climate change, it is critical to understand their potential impacts on kelp forest ecosystems. During the 2021/22 northeast Atlantic storm season, the United Kingdom (UK) was subject to several intense storms, of which the first and most severe was Storm Arwen. Due to the unusual northerly wind direction, the greatest impacts of Storm Arwen were felt along the northeast coast of the UK where wind gusts exceeded 90 km/h, and inshore significant wave heights of 7.2 m and wave periods of 9.3 s were recorded. Here, we investigated temporal and spatial variation in the structure of L. hyperborea forests and associated understorey assemblages along the northeast coast of the UK over the 2021/22 storm season. We found significant changes in the cover, density, length, biomass, and age structure of L. hyperborea populations and the composition of understorey assemblages following the storm season, particularly at our most north facing site. We suggest continuous monitoring of these systems to further our understanding of temporal variation and potential recovery trajectories, alongside enhanced management to promote resilience to future perturbations. • Spatio-temporal variation in the structure, abundance, and composition of L. hyperborea forests and their associated understorey macroalgae and macrofauna assemblages along the northeast coast of the UK was assessed between two timepoints spanning the 2021/22 northeast Atlantic storm season. • Storm Arwen, which was characterised by an unusual northerly wind direction, was one of the most impactful storms along the northeast coast with winds gusts exceeding 90 km/h and significant wave heights of over 7m. • We found significant variation in the cover, density, length, biomass, and age structure of L. hyperborea populations and the composition of understorey assemblages between pre and post storm timepoints. • Differences between timepoints were generally most pronounced at the most north facing site. • The results suggest that the storm season likely had an impact on the kelp forest ecosystem, but seasonal variation may also have contributed to observed differences between timepoints. [ABSTRACT FROM AUTHOR]

Using rainbow wrasse as a model species, we evaluate the impact of protection on the relationship between body size and: i) trophic position (TP), based on δ15N; and ii) body condition (BC), based on weight-at-length. We found that the biomass of the rainbow wrasse, their predators and their competitors was higher inside the no-take marine protected area (NTA) than in the area open to fishing. The TP of rainbow wrasse was higher inside the NTA but the BC was lower. A domed relationship between TP and size was observed in both areas: the TP increased with size up to 12.6 cm total length, when all individuals shifted to terminal males, and then decreased. Although other confounding environmental variables may exist, the indirect effects of fishing on competition and predation risk are the most likely explanation for the changes in TP, BC and the ontogenetic dietary shift of the rainbow wrasse. • Biomass of rainbow wrasse, its predators and competitors increases in No-take areas. • Trophic position and body condition of rainbow wrasse change in response to fishing. • An unexpected ontogenetic dietary shift is observed in association to sex change. • Rainbow wrasses select prey of lower trophic position after sex change. [ABSTRACT FROM AUTHOR]