Two-way analyses of variance for sediment-water exchanges of O₂ and TCO₂ and for the benthic respiratory coefficient RQ.

<p>Significant values (<i>P</i><0.05) are in bold. Data were not-transformed (<i>P</i>_C-cochran >0.05), except for O_2, which was arc-tangent transformed to homogenise the residual variances. Asterisk indicates pooling of interaction when <i>P</i>>0.25.</p

Mean (+1SE) for (a) benthic oxygen (O₂) consumption and total carbon dioxide (TCO₂) released during 12 hours dark incubation; (b) Respiratory quotient (RQ).

<p>In the graphs, A−: <i>A. marina</i> excluded; A+: procedural control for burial; the legend indicate the levels of detrital addition (0: no addition; 200∶200 g WW were added twice at a 1 week interval; 600∶600 g WW were added twice with a 1 week interval). Data were sampled one month after detrital addition.</p

Two-way analyses of variance for chlorophyll <i>a,</i> macrofauna abundance and number (N) of species.

<p>Significant values (<i>P</i><0.05) are in bold. Data were sqrt-transformed for macrofauna abundance.</p

Repeated measure analyses of variance and sphericity tests for the ¹³C incorporation in macrofauna and bulk sediment, and for the ¹³CO₂ released from the benthos (benthic respiration) during detrital decomposition at an intermediate level of detrital enrichment (200 gWW plot⁻¹added twice).

<p>Significant values (P<0.05) are in bold. Sphericity test was not significant.</p

Decomposing curves for <i>Ulva</i> detritus in lugworm excluded (treatment A−; square symbols in the graphs) or procedural control sediments (treatment A+; triangle symbols in the graph).

<p>Symbols indicate mean (± SE) for macroalgal biomass and are relative to experiments 2.</p

Mean ± SE for (a) T¹³CO₂ released from the sediment to the water column (sum of dry and wet fluxes); (b) amount of ¹³C organic carbon in the bulk sediment (averaged over depth profile) and (c) amount of ¹³C carbon incorporated by macrofauna.

<p>Data are fitted to the LOESS smoothing with an interval of 4 and 1 polynomial degree. Values are averaged over the two plots where <i>A. marina</i> was excluded (treatment A−; square symbols in the graphs) and the two procedural control plots (treatment A+; triangle symbols in the graph). Data refers to the experiment 2. Asterisk indicates significant differences.</p

Comparison of sediment surface appearance after <i>Arenicola marina</i> exclusion at low tide.

<p>A− represent the sediment after 1 month from the burial of net to exclude burrowing species. A+ is the procedural control treatment (see Materials and Methods for details).</p

Mean (+1SE) for (a) bulk sediment organic carbon (OC) and (b) porewater dissolved inorganic carbon (DIC) at different sediment depths (<i>1 cm</i>: surface sediment to 1 cm depth; <i>2 cm</i>: from the depth of 1 to 2 cm; <i>6 cm:</i> from the depth of 2 to 6 cm).

<p>In the graphs, A−: <i>A. marina</i> excluded; A+: procedural control for burial; the legend indicate the levels of detrital addition (0: no addition; 200∶200 g WW were added twice at a 1 week interval; 600∶600 g WW were added twice with a 1 week interval). Data were sampled one month after detrital addition. Asterisk indicates significant differences.</p