In situ quantification of bioturbation using time-lapse fluorescent sediment profile imaging (f-SPI), luminophore tracers and model simulation

Abstract

In order to link actual biological data on bioturbation to the abstract parameters in bioturbation models, high-resolution data on the frequency and lengths of particle displacements are required. The temporal variation in bioturbation for a subtidal macrofaunal assemblage was studied non-invasively and in situ using an optically modified fluorescence sensitive time-lapse sediment profile imaging camera (f-SPI), fluorescent-dyed sediment particles (luminophores) and mathematical modelling. This combined approach allowed tracer particles to be non-invasively tracked and their displacements monitored at an unprecedented spatial (78 µm) and temporal (every 10 min) resolution for extended periods of time (16 h). The redistribution of luminophores was digitally acquired from sequential images and compared to model predictions, with particle transport modelled as (1) a diffusive process, allowing the biodiffusion coefficient, D b , to be estimated, and (2) a non-local process, allowing a reworking activity constant, a, to be calculated. Model predictions of luminophore particle transport for the final image of the f-SPI sequence gave: D b = 1.26 × 10 2 cm 2 yr -1; a = 5.23 × 10 -2 cm -1 yr -1. Discrete values of a fluctuated widely throughout the sequence and allowed discrete bioturbation events to be identified. Time-lapse movie sequences revealed that most of the bioturbation observed during the deployment could be directly attributed to the behaviour of the brachyuran crab Hyas araneus. Our findings demonstrate that f-SPI provides a rapid and non-invasive means to visualise and quantify, in situ, the extent and influence of discrete infaunal bioturbation events on particle mixing. This technique provides detailed information on the spatial and temporal resolution of such bioturbation events, which could significantly improve existing models of bioturbation.

Mediation of macronutrients and carbon by post-disturbance shelf sea sediment communities

“…Faunal mediated sediment particle reworking was estimated non-invasively using fluorescent sediment profile imaging (f-SPI, following Solan et al 2004b; Canon 400D, 10 s exposure, aperture f5.6, ISO 400, 3888 9 2592 pixels, effective resolution 39 9 39 lm pixel -1 ). Redistribution of fluorescent tracers (215 g aquarium -1 , green colour, size class: \125 lm, mean particle size *80 lm; Brian Clegg Ltd., UK) was determined from stitched composite images (four sides aquarium -1 ; RGB colour, JPEG compression) obtained under UV light illumination (Schiffers et al 2011) after 6 days.…”

Functional effects of the hadal sea cucumber Elpidia atakama (Echinodermata: Holothuroidea, Elasipodida) reflect small-scale patterns of resource availability

“…Feeding tentacles are a positioned to the anterior (the bottom of each image) and raised above the sediment-water interface during locomotion and b lowered to intersect the sediment-water interface during bout of feeding. Frames were selected at random from successive bouts of locomotion and feeding bioturbation which is qualitatively distinct from bioturbation associated with feeding activity , giving credence to the view that epifaunal species can have a substantial effect on the properties of the sediment profile (Solan et al 2004). It is, however, difficult to assess the ecological contribution of E. atakama in the absence of information on the spatial extent and temporal persistence of this species.…”

Habitat structure mediates biodiversity effects on ecosystem properties

“…10, Lee Filters, UK) was mounted in front of the camera lens. Following Solan et al [40], images were saved in RGB colour mode with JPEG compression and analysed using a custom-made semiautomated macro that runs within IMAGEJ (v. 1.40), a Javabased public domain program (available at http://rsb.info. nih.gov/ij/index.html).…”