Marginopora vertebralis are large benthic foraminifera (LBF) found commonly in the low-lying reef flats on the Great Barrier Reef. They form photo-symbiotic associations with microalgae and through calcification, are essential contributors to reef sediments. While many studies have noted M. vertebralis as being epiphytic, evidence supporting this lifestyle and data on deliberate habitat selection is lacking. Here we investigated M. vertebralis-macroalgal associations and habitat preferences. Through field sampling campaigns, we found significant associations with the calcifying macroalgae Amphiroa foliacea, Halimeda opuntia and H. macroloba on the reef flat. Subsequent preference experiments confirmed A. foliacea and H. opuntia as selected macroalgal habitats of choice. We also found strong aversion toward the calcifying brown algae Padina tenuis, emphasising the deliberate nature of the selection. The clear preference for living, structurally dense, calcifying macroalgae, implies that these associations confer some biological or ecological benefit to M. vertebralis. These findings highlight the need to understand the role of M. vertebralis-macroalgal associations in M. vertebralis ecological resilience and how it may shape the fate of M. vertebralis in a future marine environment.
Species distribution modelling is a widely used approach for studying species’ environmental niches and identifying the main drivers of species distribution. These modelling frameworks have been gaining popularity owing to the growing need among conservation ecologists and nature managers to understand and anticipate the distribution shifts accompanying ongoing environmental changes. To investigate the drivers of marine groundfish community composition in the subarctic, a joint species distribution model (JSDM) was applied to fish community data from the continental shelf and slope of Iceland. In a novel approach, the JSDM was used to compare the ecological niches of demersal and benthopelagic species with the niches of bathydemersal species. Depth and sea bottom temperature resulted as strong predictors of species distribution, with depth being more important for shallow-water species and temperature for deep-water species. Salinity, sea bottom slope, time at trawling, chlorophyll a concentration, and fishing intensity each explained ≤4
Movements of swordfish (Xiphias gladius) typically follow the diel vertical migration of mesopelagic animals, spending daylight hours at 600 m and nights near the surface. However, years of satellite tagging data have also revealed infrequent extreme dives exceeding 1000 m, the motivation for which remains unknown. Here, we investigated the movements of 34 North Atlantic swordfish using data from pop-up satellite archival transmitting tags deployed for one to six months. Statistically “extreme” maximum daily depths were identified on 39 of 3666 deployment days, from which 29 extreme dives were confirmed using depth-time series. These dives were brief, predominantly daytime events, and occurred across the full geographic range of the dataset, spanning temperate to tropical waters and from shelf-break regions to the Mid-Atlantic Ridge. We evaluated competing hypotheses for these dives, including foraging, predator avoidance, and navigation. Dive geometry and mixed-effects models of environmental conditions indicated that extreme dives were most likely to occur in association with elevated sea surface height and variability in sea surface temperature, conditions associated with dynamic oceanographic features such as frontal systems and major currents, with weaker associations with bathymetric and magnetic field features. Together, these findings are most consistent with a role in environmental profiling, whereby swordfish intermittently sample vertical structure or physical cues during large-scale movements. While this profiling may contribute to navigation, the underlying mechanisms for such behavior remain unresolved. Our results highlight the behavioural complexity of swordfish and underscore the importance of the deep ocean in shaping the ecology of highly migratory pelagic predators.
To better understand the distribution of native smooth-shelled blue mussels (genus Mytilus) in the North Pacific region (USA, Canada, Russia, China, Korea) and to quantify the geographic extent of invasion and the degree of hybridisation between native and non-native mussels we analysed mussels from 15 North Pacific sites and 16 global reference sites for variation at 59 single nucleotide polymorphism (SNP) loci. Samples were collected between 2006 and 2014, and some sample sizes were small (< 10 mussels) with the result that some site-specific interpretations are limited. Overall, our SNP-based results confirmed earlier findings based on other marker types and revealed (1) the likelihood of multiple independent invasion events of M. galloprovincialis, (2) the spatially patchy nature of bioinvasion in the USA, Canada, and Russia, (3) that sites in China and Korea exhibited only invasive M. galloprovincialis, and (4) the limited extent of hybridisation between M. trossulus × M. galloprovincialis beyond the F1 generation. The regions of origin of invasive Mediterranean M. galloprovincialis are primarily the central Mediterranean Sea and secondarily the Black Sea and Sea of Azov. The source sites of origin of invasive Atlantic M. galloprovincialis cannot be determined. Whilst we cannot categorically rule out alternative hypotheses, these results support the interpretation of multiple independent invasion events. Our results provide the first large geographic scale SNP-based assessment of smooth-shelled blue mussel genetic variation in the North Pacific region and highlight the positive (development of aquaculture) and negative (hybridisation with the endemic species) impacts of invasive M. galloprovincialis in the North Pacific region.
Temporal and spectral properties of fish sounds can vary across geographic regions, yet the extent to which temporal organisation between sounds (i.e. rhythms) contributes to this variability remains poorly understood. In Mediterranean Posidonia oceanica meadows, the /Kwa/ sound type overwhelmingly dominates the fish soundscape, but its intra‑specific diversity remains largely unresolved. Here, we investigate whether the /Kwa/ rhythmic structure varies spatially and whether rhythmic organisation is associated with previously reported variation in peak-frequency classes within the genus Scorpaena, the confirmed emitter of the /Kwa/ sound type. Eighty /Kwa/ sequences recorded using Passive Acoustic Monitoring (PAM) at four Mediterranean sites (Mallorca, Corsica, Crete, and Cyprus) were analysed. Based on temporal organisation, five rhythm pattern types (Types 1–5) were identified from qualitative spectrogram assessment. Rhythm‑pattern composition differed significantly among sites: Type 1 rhythms dominated western Mediterranean sites, whereas Type 3 rhythms predominated in the eastern basin, with Cyprus additionally exhibiting a high proportion of Type 2 rhythms. These findings reveal geographic variation in the /Kwa/ rhythmic organisation and an association between rhythmic and spectral structure. The results highlight rhythm as a potentially informative but underexplored component of fish acoustic signals and support its inclusion in future studies of fish acoustic diversity and PAM.
