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Experiments in marine behavioural ecology rely heavily on observations made in tanks. However, when studying acoustic behaviours of marine animals in confined volumes, the effects of reverberation must be characterized, something that has been overlooked in parts of the marine ecology literature. In this study, we characterized reverberation in tanks using an artificial sound source and examined the implications for bioacoustic studies using sounds emitted by the European lobster Homarus gammarus during feeding and in response to stress. Broadband and transient sounds commonly produced by crustaceans were severely impacted by reverberation such that their spectral characteristics and pulse width durations could not be assessed. In contrast, low-frequency sounds could be characterized in tanks, but not their source level. Based on these observations, we describe a simple methodology to identify which sound characteristics can be measured in tanks. When feeding, the lobsters produced broadband and transient sounds called ‘rattles’, similar to sounds reported for tropical spiny lobsters Palinurus longipes and P. argus. When stressed, H. gammarus vibrated its carapace, producing a low-frequency sound analogous to the ‘buzzing’ sound of the American lobster H. americanus. The potential role of species-specific sound is discussed; however, although our observations represent the first bioacoustic characterization of H. gammarus, additional behavioural studies are necessary to understand their ecological meaning.

1 - Comprehensive understanding of biological diversity patterns requires quantifying spatial dynamic processes. Mathematical modelling offers an array of techniques to investigate ecosystem processes that cannot be observed directly or tested experimentally. 2 - In the 1990's, a new paradigm for biodiversity studies appeared - cal led metacommunities - combining ecological and biogeographical concepts of species assemblages. A metacommunity is defined as a set of local communities linked by the exchanges of individuals at the regional scale. This relatively simple definition led to the development of theoretical frameworks (e.g. emphasizing neutrality, patch dynamics, species sorting and mass effects) that generated some controversy about the relative importance of the local ecological niche-based processes and regional dispersal processes. Recent studies have demonstrated that several of these proposed theories can lead to similar results when simulating the dynamics of metacommunity systems. 3 - Thus, it does not seem possible to adequately prove whether or not local processes predominate over regional ones from available datasets, even if several evaluation criteria are combined. This is why metacommunity modelling is an important step toward quantifying changes in marine biodiversity. Models can be improved by unifying population dynamics processes and by establishing accurate typologies of parameter estimates. Validation should be performed by carrying out ad hoc experiments, testing dynamic properties; however, the design and implementation of these experiments remain difficult because of the lack of large-scale experimental facilities under control led conditions. 4 - Metacommunity modelling seems however to be promising for a broad range of applications in the domain of conservation of marine biodiversity, and particularly in that it can provide objective criteria to define Marine Protected Areas as a function of regional biodiversity conservation goals. [ABSTRACT FROM AUTHOR]

Woody debris is found in all habitats of the land-sea continuum. While isolated experimental studies of wood degradation exist, few programs have observed the dynamics of wood degradation, in situ across this gradient. Since 2014, we have been conducting a series of long-term observations of wood decay in three characteristic areas of a Mediterranean Sea coastal watershed: forest leaf litter ('Forest'), river bed ('River') and the near-shore marine environment ('Sea'). The study sites are within the Massane River watershed (France) whose headwaters are in a protected beech tree (Fagus sylvatica) dominated forest. Branch sections from a recently fallen beech tree and standardized blocks of Norway spruce (Picea abies) were installed in all three environments. The proportion of remaining mass and volumetric mass of the individual wood samples were determined periodically over 4.2 years. Regardless of wood type, there were marked differences in the decay dynamics. Mass losses at the Forest and River sites were well-described by continuous negative exponential models. At the Sea site, there was a short latency period followed by rapid degradation for the wood fraction exploited by shipworms; in this case, a Weibull-type function was fitted to the data. Integrated mass loss rates at the coastal location were 6 to 20 times faster than in the other two environments. Our study suggests that the early dynamics of wood degradation in a land-sea meta-ecosystem are dominated by the marine invertebrate community. This means woody debris, once it reaches the sea, is likely to break down rapidly within near shore coastal habitats. These results highlight the need to quantify the mass transport dynamics between local ecosystems., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Previous studies have demonstrated that male European lobsters ( Homarus gammarus ) use chemical and visual signals as a means of intraspecific communication during agonistic encounters. In this study, we show that they also produce buzzing sounds during these encounters. This result was missed in earlier studies because low-frequency buzzing sounds are highly attenuated in tanks, and are thus difficult to detect with hydrophones. To address this issue, we designed a behavioural tank experiment using hydrophones, with accelerometers placed on the lobsters to directly detect their carapace vibrations (i.e. the sources of the buzzing sounds). While we found that both dominant and submissive individuals produced carapace vibrations during every agonistic encounter, very few of the associated buzzing sounds (15%) were recorded by the hydrophones. This difference is explained by their high attenuation in tanks. We then used the method of algorithmic complexity to analyse the carapace vibration sequences as call-and-response signals between dominant and submissive individuals. Even though some intriguing patterns appeared for closely size-matched pairs (<5 mm carapace length difference), the results of the analysis did not permit us to infer that the processes underlying these sequences could be differentiated from random ones. Thus, such results prevented any conclusions about acoustic communication. This concurs with both the high attenuation of the buzzing sounds during the experiments and the poor understanding of acoustic perception by lobsters. New approaches that circumvent tank acoustic issues are now required to validate the existence of acoustic communication in lobsters., Competing Interests: Competing interestsThe authors declare no competing or financial interests., (© 2020. Published by The Company of Biologists Ltd.)

The PAH contamination level and biochemical composition of sinking particles and surficial sediments (0-0.5 cm layer) were assessed at a rural coastal site in the northwestern Mediterranean Sea. Surficial sediment contamination (≈20 ng g(-1)) was considerably lower than at other Mediterranean sites, yet particles collected in sediment traps had 6-8 times more PAH. Contaminated particles were mostly marine in origin. Temporal variation of contamination levels correlated with organic content of the particles, but some of the observed variability could be attributed to seasonal changes in pyrolytic PAH production. Sinking organic particles were potentially as readily digestible as surficial sediments for prospective consumers however, transfer of PAHs along the benthic food chain is probably enhanced because of the particles' higher nutritional value., (Copyright © 2012 Elsevier Ltd. All rights reserved.)