a-c. Multispecies assessment of emergence (%) in response to sediment burial.

<p>Factors assessed: a) Duration (days); b) Sediment fraction (C = course, M = medium, F = fine) and; c) Depth of burial (cm) above organism.</p

Indicators of mortality used to assess organisms following burial treatments.

<p>Indicators of mortality used to assess organisms following burial treatments.</p

a-c. Multispecies assessment of mortality (%) in response to sediment burial.

<p>Factors tested: a) Duration (days); b) Sediment fraction (C = course, M = medium, F = fine) and; c) Depth of burial (cm) above organism.</p

<i>Sabellaria spinulosa</i> clump with ‘emergence tubes’.

<p>‘Emergence tubes’ constructed during burial by 2 cm fine (0.1–0.25 mm) sand for 16 days. The inset (top left) shows an isolated emergence tube which breaks off the main parent colony easily, and through which an individual animal is clearly visible. The inset (bottom left) shows three tubes emerging from the sediment following burial (Image source: Kim Last).</p

Sediment Burial Intolerance of Marine Macroinvertebrates

<div><p>The marine environment contains suspended particulate matter which originates from natural and anthropogenic sources. Settlement of this material can leave benthic organisms susceptible to smothering, especially if burial is sudden i.e. following storms or activities such as dredging. Their survival will depend on their tolerance to, and their ability to escape from burial. Here we present data from a multi-factorial experiment measuring burial responses incorporating duration, sediment fraction and depth. Six macroinvertebrates commonly found in sediment rich environments were selected for their commercial and/or conservation importance. Assessments revealed that the brittle star (<i>Ophiura ophiura</i>), the queen scallop (<i>Aequipecten opercularis</i>) and the sea squirt (<i>Ciona intestinalis</i>) were all highly intolerant to burial whilst the green urchin (<i>Psammichinus miliaris</i>) and the anemone (<i>Sagartiogeton laceratus</i>), showed intermediate and low intolerance respectively, to burial. The least intolerant, with very high survival was the Ross worm (<i>Sabellaria spinulosa</i>). With the exception of <i>C</i>. <i>intestinalis</i>, increasing duration and depth of burial with finer sediment fractions resulted in increased mortality for all species assessed. For <i>C</i>. <i>intestinalis</i> depth of burial and sediment fraction were found to be inconsequential since there was complete mortality of all specimens buried for more than one day. When burial emergence was assessed <i>O</i>. <i>ophiura</i> emerged most frequently, followed by <i>P</i>. <i>miliaris</i>. The former emerged most frequently from the medium and fine sediments whereas <i>P</i>. <i>miliaris</i> emerged more frequently from coarse sediment. Both <i>A</i>. <i>opercularis</i> and <i>S</i>. <i>laceratus</i> showed similar emergence responses over time, with <i>A</i>. <i>opercularis</i> emerging more frequently under coarse sediments. The frequency of emergence of <i>S</i>. <i>laceratus</i> increased with progressively finer sediment and <i>C</i>. <i>intestinalis</i> did not emerge from burial irrespective of sediment fraction or depth. Finally, and perhaps unsurprisingly, the greatest ability to emerge from burial in all other species was from shallow (2 cm) burial. Although survival was consistently highly dependent on duration and depth of burial as expected, emergence behaviour was not as easily predictable thereby confounding predictions. We conclude that responses to burial are highly species specific and therefore tolerance generalisations are likely to be oversimplifications. These data may be used to inform environmental impact models that allow forecasting of the cumulative impacts of seabed disturbance and may provide mitigation measures for the sustainable use of the seabed.</p></div

Experimental Sediment Total Oxygen Uptake (TOU) rates.

<p>Oxygen flux rates during closed incubations for experimental sediments under varying organic matter treatments (0, 0.1 and 1%) at <b>A</b> ambient (15°C) and <b>B</b> summer maximum temperatures (20°C). Error bars represent standard error.</p

Oxygen Depletion Curves from Sediment Metabolism Incubations.

<p>Depletion curves display mean oxygen concentration values for triplicate samples of each OM treatment (0, 0.1 or 1%) at their respective temperatures. Error bars represent standard error of replicate oxygen concentrations for each time step. Dotted lines between solid lines represent best fit inter/extrapolations. <b>A.</b> Oxygen depletion curve for fine sediment at 15°C. <b>B.</b> Oxygen depletion curve for coarse sediment at 15°C. <b>C.</b> Oxygen depletion curve for fine sediment at 20°C. <b>D.</b> Oxygen depletion curve for coarse sediment at 20°C.</p

Burial Tolerance under Experimental Variables.

<p>Cross tabulation of burial mortality data from <b>A</b> organic matter content, <b>B</b> temperature, <b>C</b> sediment fraction size and <b>D</b> duration of burial treatments.</p

Probability of Mortality under Model Output.

<p>Comparison of mortality probability under all model predictor variables compared to probability at the intercept (baseline for all factor variables and ≤ 2 days burial duration). Error bars represent 95% confidence intervals.</p

Comparative Mortality of Control and Buried Specimens.

<p>Total mortality of buried mussels = 41.7% (all OM, sediment, burial duration and temperature treatments) versus no mortality in controls.</p