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EGU Journal Logos (RGB) Open Access Open Access Open Access Advances in Annales Nonlinear Processes Geosciences Geophysicae in Geophysics Open Access Open Access Natural Hazards Natural Hazards and Earth System and Earth System Sciences Sciences Discussions Open Access Open Access Atmospheric Atmospheric Chemistry Chemistry and Physics and Physics Discussions Open Access Open Access Atmospheric Atmospheric Measurement Measurement Techniques Techniques Discussions icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion Open Access Biogeosciences Discuss., 10, 14333–14438, 2013 Open Access www.biogeosciences-discuss.net/10/14333/2013/ Biogeosciences Biogeosciences BGD doi:10.5194/bgd-10-14333-2013 Discussions © Author(s) 2013. CC Attribution 3.0 License. 10, 14333–14438, 2013 Open Access Open Access This discussion paper is/has been under review for the journal BiogeosciencesClimate (BG). Anoxia and Please refer to the correspondingof the final Past paper in BG if available. of the Past Discussions macrofauna behaviour Open Access Effect of and anoxia on Open Access Earth System Earth System B. Riedel et al. Dynamics Dynamics invertebrate behaviour: ecologicalDiscussions

Title Page Open Access perspectivesGeoscientific from to communityGeoscientific Open Access Instrumentation Instrumentation Abstract Introduction level Methods and Methods and Conclusions References 1 1,2 Data Systems 1 1 Data Systems1,3 B. Riedel , T. Pados , K. Pretterebner , L. Schiemer , A. SteckbauerDiscussions, Open Access 4 4 Open Access 1 Tables Figures A. Haselmair , M. Zuschin , and M. Stachowitsch Geoscientific Geoscientific 1 Model Development University of Vienna,Model Department Development of Limnology and , Vienna, Austria J I 2University of Kiel, Helmholtz-Zentrum für Ozeanforschung, GEOMAR, Kiel,Discussions Germany 3 J I Open Access

IMEDEA (CSIC-UIB), Mediterranean InstituteOpen Access for Advanced Studies, Department of Global Change Research, Esporles,Hydrology Spain and Hydrology and Back Close 4University of Vienna, DepartmentEarth System of , Vienna, Austria Earth System Sciences Sciences Full Screen / Esc Received: 28 June 2013 – Accepted: 6 August 2013 – Published: 27 August 2013 Discussions Open Access Correspondence to: B. Riedel ([email protected])Open Access Printer-friendly Version Science Published by CopernicusOcean Publications Science on behalf of the European Geosciences Union. Discussions Interactive Discussion Open Access Open Access 14333 Solid Earth Solid Earth Discussions Open Access Open Access

The Cryosphere The Cryosphere Discussions icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion Abstract BGD Coastal hypoxia and anoxia have become a global key stressor to marine ecosys- tems, with almost 500 dead zones recorded wordwide. By triggering cascading effects 10, 14333–14438, 2013 from the individual organism to the community and ecosystem-level, oxygen deple- 5 tions threat marine biodiversity and can alter ecosystem structure and function. By Anoxia and integrating both physiological function and ecological processes, behaviour is macrofauna ideal for assessing the stress state of benthic macrofauna to low dissolved oxygen. behaviour The initial response of organisms can serve as an early-warning signal, while the suc- cessive behavioural reactions of key species indicate hypoxia levels and help assess B. Riedel et al. 10 community degradation. Here we document the behavioural responses of a represen- tative spectrum of benthic macrofauna in the natural setting in the Northern Adriatic , Mediterranean. We experimentally induced small-scale anoxia with a benthic Title Page

chamber in 24 m depth to overcome the difficulties in predicting the onset of hypoxia, Abstract Introduction which often hinders full documentation in the field. The behavioural reactions were 15 documented with a time-lapse camera. Oxygen depletion elicited significant and re- Conclusions References peatable changes in general (visibility, locomotion, body movement and posture, lo- Tables Figures cation) and species-specific reactions in virtually all organisms (302 individuals from 32 species and 2 species groups). Most atypical (stress) behaviours were associated with specific oxygen thresholds: arm-tipping in the ophiuroid Ophiothrix quinquemac- J I −1 20 ulata, for example, with the onset of mild hypoxia (< 2 mLO2 L ), the emergence of J I −1 polychates on the sediment surface with moderate hypoxia (< 1 mLO2 L ), the emer- gence of the infaunal sea urchin Schizaster canaliferus on the sediment with severe Back Close −1 hypoxia (< 0.5 mLO2 L ) and heavy body rotations in sea anemones with anoxia. Full Screen / Esc Other species changed their activity patterns, i.e. circadian rhythm in the hermit

25 Paguristes eremita or the bioherm-associated crab Pisidia longimana. Intra- and inter- Printer-friendly Version specific reactions were weakened or changed: decapods ceased defensive and ter- ritorial behaviour, and predator-prey interactions and relationships shifted. This nu- Interactive Discussion anced scale of resolution is a useful tool to interpret present benthic community sta-

14334 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion tus (behaviour) and past mortalities (community composition, e.g. survival of tolerant species). This information on the sensitivity (onset of stress response), tolerance (mor- BGD tality, survival), and characteristics (i.e. life habit, functional role) of key species also 10, 14333–14438, 2013 helps predict potential future changes in benthic structure and ecosystem function- 5 ing. This integrated approach can transport complex ecological processes to the public and decision-makers and help define specific monitoring, assessment and conserva- Anoxia and tion plans. macrofauna behaviour

1 Introduction B. Riedel et al.

The increasing intensity and diversity of anthropogenic stressors is triggering unprece- 10 dented habitat and in marine ecosystems worldwide (Halpern et al., Title Page 2008). The effects, ranging from population depletion to species and com- munity , raise concerns whether ecosystem function and ecosystem Abstract Introduction

goods and services can be maintained (UNEP, 2006; Worm et al., 2006; Cardinale Conclusions References et al., 2012). A key issue is understanding how species respond to such rapid human- 15 induced environmental change (Sih et al., 2011; Tuomainen and Candolin, 2011). Tables Figures is one of the most striking ecological threats to shallow coastal and estuaries (Smith and Schindler, 2009). Excessive nutrient inputs have the potential J I to tip systems into hypoxia (here defined as dissolved oxygen [DO] concentrations < 2 mLL−1, equivalent to 2.8 mgL−1 or 91.4 µM; Diaz and Rosenberg, 2008) and anoxia J I 20 or exacerbate conditions in predisposed areas (Gooday et al., 2009; Howarth et al., Back Close 2011). Currently, the number of coastal eutrophic and hypoxic sites nearly touches the 500 mark (Diaz et al., 2010), with devastating effects for marine biodiversity and Full Screen / Esc ecosystem functioning (Zhang et al., 2010). Ocean warming is expected to additionally increase the frequency, duration, intensity and extent of hypoxia/anoxia in certain zones Printer-friendly Version 25 (Keeling et al., 2010; Gruber, 2011), pushing coastal ecosystems toward tipping points Interactive Discussion (Conley et al., 2009; Rabalais et al., 2010) (Fig. 1).

14335 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion Physiological and metabolic adaptions to hypoxia are the initial organismic re- sponses (Grieshaber et al., 1994; Hagerman, 1998), mortality the endpoint (Vaquer- BGD Sunyer and Duarte, 2008; Riedel et al., 2012). Exposure to oxygen concentrations far 10, 14333–14438, 2013 above the lethal threshold already adversly affects growth, reproduction, locomotion 5 and feeding (e.g. summarized in Gray et al., 2002; Wu, 2002; Levin et al., 2009). Im- portantly, basic behavioural activities are the link between individual responses and Anoxia and population changes (Boyd et al., 2002). Intraspecifically, for example, hypoxia affects macrofauna mate choice or courtship behaviours in fish, impacting reproduction and development behaviour (Wu, 2009). Change in one behaviour may influence the outcome of others, e.g. altered B. Riedel et al. 10 locomotion can affect reproduction and/or food finding behaviour (Boyd et al., 2002). In- terspecifically, shifts in locomotion – migration to a new region, shallower burial depths or exposure atop elevated substrates – may change predator–prey relationships (Pihl Title Page et al., 1992; Riedel et al., 2008a; Long and Seitz, 2008). Behavioural parameters thus integrate direct and indirect responses across several levels of biological organisation, Abstract Introduction 15 from individual fitness to community composition, reflecting cascading changes in bio- diversity, biogeochemical processes and ecosystem function (e.g. Solan et al., 2004; Conclusions References

Middelburg and Levin, 2009; Ekau et al., 2010; Zhang et al., 2010). Tables Figures Such intimately nested responses call for more holistic approaches. Unexpected on- sets of hypoxia, poorly predictable extents and the often rapid course of events are J I 20 a challenge in gaining a better insight into when ecosystems approach critical points. This calls for recognizing perturbations at the earliest possible stage, when adaptive J I capacity and resilience are still functional. The initial short-term reactions and atyp- Back Close ical behaviours of benthic macrofauna are a suitable avenue (summarised in Diaz and Rosenberg, 1995; Rabalais et al., 2001; Levin et al., 2009). For example, avoid- Full Screen / Esc −1 25 ance and altered migration patterns generally start when oxygen falls below 3.0 mgL −1 (equivalent to 2.1 mLL ). Such initial behavioural responses of benthic macrofauna Printer-friendly Version integrate processes in the environment (from the sediment to the water body), yield- ing information beyond prevailing oxygen concentrations and species tolerance ranges Interactive Discussion to encompass overall ecosystem stress (e.g. Xu et al., 2006). This makes behaviour

14336 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion a suitable early-warning indicator that also increases our understanding of longer-term ecosystem consequences (Tuomainen and Candolin, 2011). BGD Our in situ approach complements laboratory experiments, which provide detailed 10, 14333–14438, 2013 information on the individual organism-level (e.g. respiration, growth rate and repro- 5 duction) but typically concentrate on captured of single-species in artificial settings (Biro, 2012). The benthic chamber not only rivals the level of resolution in lab- Anoxia and oratory studies but also documents the complex biological interactions that accompany macrofauna and define ecosystem responses to stress (Adams, 2003). Such multi-species analy- behaviour ses provide a very realistic and more holistic understanding of the complex structural B. Riedel et al. 10 and functional processes and potential species interactions in a community setting – a prerequisite for understanding ecosystem integrity (Culp et al., 2000; Sibley et al., 2000). Title Page We hypothesized that certain (atypical) behaviours of benthic invertebrates are as- sociated with distinct oxygen thresholds and that the behaviour of key species reliably Abstract Introduction 15 indicats the status of benthic communities during hypoxia. We continuously recorded the multiple direct and indirect responses, including altered behaviours, inter- and in- Conclusions References

traspecific interactions and mortality sequences, of a sublittoral macrobenthic assem- Tables Figures blage to hypoxia/anoxia in a realistic scenario. The benthic chamber induced small- scale anoxia in a benthic soft-bottom community setting in 24 m depth in the Northern J I 20 Adriatic Sea. A time-lapse camera and sensors (oxygen, hydrogen sulphide, tempera- ture, pH) enabled continuous documentation of environmental parameters and biolog- J I ical responses. The focus was on the benthic macrofauna as the first component to Back Close visibly react to coastal hypoxia and the compartment that fundamentally defines such ecosystems and their functioning. The sediment-geochemical processes (Koron et al., Full Screen / Esc 25 2013; Metzger et al., 2013), the accompanying meiofauna responses (foraminiferans: Langlet et al., 2013a, b; harpacticoid copepods: Grego et al., 2013a, b; De Troch et al., Printer-friendly Version 2013), and immediate post-anoxia scavenging and longer-term recovery (Blasnig et al., 2013) are treated elsewhere in this special issue. Interactive Discussion

14337 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion 2 Material and methods BGD 2.1 Location and dates 10, 14333–14438, 2013 The Northern Adriatic Sea (Mediterranean) is a recognised area for seasonal low DO events (Malej and Malačič, 1995; Diaz and Rosenberg, 2008), here often as- Anoxia and 5 sociated with massive marine snow events (Danovaro et al., 2009 and references macrofauna therein). The study site is located within and representative for a wide-ranging, behaviour suspension-feeding macroepifauna community consisting of interspecific aggregations (multi-species clumps or bioherms) described as the Ophiothrix-Reniera-Microcosmus B. Riedel et al. (ORM) community by Fedra et al. (1976). 10 Eleven deployments with a specially designed benthic chamber, were made in 2005 (September) and 2006 (August to October) in a soft-bottom habitat (poorly sorted silty Title Page sand) in 24 m depth in the Gulf of Trieste (45◦320 55.6800 N, 13◦330 1.8900 E). This po- Abstract Introduction sition, adjacent to the oceanographic buoy of the Marine Biology Station Piran, is not directly affected by bottom fisheries and has not experienced hypoxia for at least 5 yr Conclusions References 15 (V. Malačič, personal communication, 2005) before our experiment. Tables Figures 2.2 Experimental procedure J I A benthic chamber was used to experimentally create small-scale anoxia and quantify macrobenthic responses to decreasing oxygen concentrations (for a detailed descrip- J I

tion of the method see Stachowitsch et al., 2007). The design involves the successive Back Close 20 use of two interchangeable bases (both 50cm × 50cm × 50 cm): an aluminum frame plus separate instrument lid (“open” configuration) and a plexiglass chamber plus this Full Screen / Esc lid (“closed” configuration). Initially, the open configuration was positioned above a ben- thic assemblage for ca. 24 h to document macrobenthic behaviour during normoxia. Printer-friendly Version Then, in a second step, the closed configuration was positioned for another 3 to 4 Interactive Discussion 25 days above the same assemblage to document the reactions to hypoxia and anoxia. The plexiglass chamber was pressed ca. 4 cm into the sediment and prevented wa- 14338 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion ter exchange with the immediate environment. The instrument lid houses a time-lapse camera, 2 flashes, a datalogger and the microsensor array for dissolved oxygen (DO), BGD hydrogen sulphide (H S) and temperature recording (Unisense®). Oxygen was mea- 2 10, 14333–14438, 2013 sured 2 and 20 cm above the sediment to detect potential stratification, the H2S sensor 5 was positioned in 2 cm height. Bottom pH was measured at the beginning and the end of almost all deployments (WTW TA 197-pH sensor). Images were taken in 6 min Anoxia and intervals, microsensor values logged every minute. macrofauna Overall, ca. 10 000 images were produced, yielding a documentation time of 1003 h behaviour (hypoxia: 331.9 h, anoxia: 336.5 h). The flashes, interrupted current and food input B. Riedel et al. 10 never triggered any visible reaction in the benthic invertebrates and were thus not con- sidered to have altered the course of the short-term experiments. Decreasing oxygen values in the chamber solely reflect natural respiration rates of the enclosed fauna Title Page (i.e. no macroalgae enclosed, photosynthesis by microflora under the low light condi- tions in 24 m depth negligible). The 11 deployments were similarly executed, but their Abstract Introduction 15 durations varied somewhat due to weather/sea conditions. Four deployments started immediately with the closed configuration because of the highly turbid bottom water Conclusions References (for a summary of data and treatments in the 11 deployments see Table A1). After Tables Figures each deployment, living and dead organisms were collected and preserved in a 4 % formalin-seawater solution. The experiments followed the institutional guidelines of the J I 20 University of Vienna, Austria, and the Marine Biology Station Piran, Slovenia. J I 2.3 Macrofauna data analysis Back Close The behaviour in a total of 302 individuals was evaluated, representing 32 species Full Screen / Esc and 2 species groups (i.e. individuals unidentifiable based on the photographs). Time- lapse movies (Adobe Premiere Pro CS4) produced from the still image series pro- Printer-friendly Version 25 vided quick viewing of the overall sequence of events (sample 4 day film available at http://phaidra.univie.ac.at/o:87923). This yielded data on a representative spectrum of Interactive Discussion taxa, life habits, (stress) behaviours, interactions as well as on sensitivities (initial reac- tions) and tolerances (i.e. survival or mortality). Evaluated life habits include substrate 14339 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion relationship (cryptic and non-cryptic epifauna, infauna), mobility (mobile, sessile) and 3 major feeding types (predators, suspension feeders, deposit feeders) (Table A2). BGD Species represented by only 1 or a few individuals were evaluated in full, those by 10, 14333–14438, 2013 many individuals selectively (those individuals most often visible and recognizable, for 5 example the porcellanid crab Pisidia longimana). Each individual was analysed sep- arately, image by image, and the behaviour recorded in categories (key categories of Anoxia and behaviours and responses listed below, for species-specific behaviours see Table A2) macrofauna (in 8 cases until they were predated: see Sect. 3.3.2 Predator-prey interactions). The behaviour terms “typical/normal” behaviour refer to responses observed during normoxia (in this B. Riedel et al. 10 study and earlier observations). Additional information on the hermit crab Paguristes eremita is provided in Pretterebner et al. (2012), on decapods (except Alpheus glaber) in Haselmair et al. (2010). Mortality and/or survival in relation to hypoxia (DO concen- Title Page tration), anoxia (duration) and associated H2S development was evaluated on overall 495 individuals (39 species and 1 species group) based on the images and specimens Abstract Introduction 15 collected after the deployment. The time-point of death was typically unambiguous, e.g. collapse of soft-bodied forms and various combinations of overturning, clear-cut body Conclusions References

postures, discoloration. For more information on mortality/survival and life habits see Tables Figures Riedel et al. (2012).

Key categories of behaviours and responses J I

J I 20 1. Visibility: visible, non-visible (hidden in/under bioherm, in sediment). Back Close 2. Locomotion: change in location (horizontal and/or vertical. Subcategories: minor (displacement < 1 body length), major (> 1 body length), none). Full Screen / Esc 3. Movement (other than locomotion): turn (change in direction), squirm, extremity Printer-friendly Version movement (i.e. legs, antennae, eyes, chelipeds), body movement (i.e. body ro- 25 tation in sea anemones, retraction into or stretching out of shell in hermit , Interactive Discussion body contraction in ascidians).

14340 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion 4. Body posture: normal, atypical (posture never observed under normoxia). BGD 5. Location: bottom (organism on sediment), middle (< 5 cm above sediment, on macroepifauna), high/top (> 5 cm/on top of bioherm). 10, 14333–14438, 2013 6. Intra- and interspecific interaction: all encounters visibly triggering a change in 5 behaviour, with focus on predator–prey relationships, atypical aggregation (> 3 Anoxia and individuals in direct contact), aggression. macrofauna behaviour 7. Species-specific responses (details: Table A2): e.g., pharynx protrusion and acon- tia discharge in Calliactis parasitica, camouflage discarding (i.e. B. Riedel et al. shell fragments) in echinoid Psammechinus microtuberculatus or decorator crab 10 mascarone. Title Page 2.4 Statistical analysis Abstract Introduction −1 Behavioural data were assigned to 5 oxygen categories: normoxia (≥2.0 mLDOL ), Conclusions References mild (< 2.0 mLDOL−1), moderate (< 1.0 mLDOL−1), severe hypoxia (< 0.5 mLDOL−1), and anoxia (no oxygen). For selected behavioural reactions to hypoxia and anoxia see Tables Figures 15 Figs. A1–A33. Error bar graphs show the proportion of behaviours per oxygen category. The number of images evaluated per oxygen category (number below the x-axis) varies J I within and between species, depending on number of individuals evaluated per deploy- ment, turbidity conditions (i.e. individual clearly identifiable), and deployment duration J I (including various oxygen category phases). In the pistol shrimp Alpheus glaber (both Back Close 20 individuals in a deployment with an intermittent oxygen peak, see below in Results), the responses are depicted as histograms (Fig. A15), showing the number of behaviours Full Screen / Esc observed per hour in relation to the oxygen curve (value averaged per hour). Significant Printer-friendly Version H2S refers to concentrations > 14 µM, as defined by Vaquer-Sunyer and Duarte (2010). The non-parametric Kruskal–Wallis test was used to determine potential differences in Interactive Discussion 25 behaviours between oxygen categories, the Mann–Whitney U test to test differences in the means of behaviours across oxygen categories. Categories with < 5 images eval- 14341 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion uated per oxygen category were excluded from statistical analysis. The significance level was p < 0.05. Analyses were performed using SPSS software package 20.0. BGD 10, 14333–14438, 2013 3 Results Anoxia and 3.1 Sensor data macrofauna

5 During the open-frame configuration, oxygen concentrations within a particular deploy- behaviour ment remained relatively constant, although the values across all deployments ranged B. Riedel et al. from 2.8 to 8.9 mLL−1 20 cm above the sediment and 2.6 to 5.6 mLL−1 in 2 cm height, reflecting the respective meteorological/oceanographic conditions. The “20 cm”-values

were typically higher. After closing the chamber, oxygen values fell constantly, with both Title Page 10 curves approximating each other. The in situ approach successfully mimicked the ac- tual time course of oxygen depletion events documented earlier in the Northern Adriatic Abstract Introduction based on macrofauna behaviour (Stachowitsch, 1984): hypoxia was generated within Conclusions References ca. 1.5 days, anoxia within 3 days (Table A1). At the transition from severe hypoxia to anoxia, the sediment colour changed from brown-grey to darker grey and finally black Tables Figures 15 with gradually increasing H2S concentrations. The rapidity of the oxygen decline varied between deployments, reflecting the J I biomass enclosed and initial oxygen concentrations. Accordingly, hypoxia duration ranged from 11.4 to 52.9 h, anoxia 5.2 to 81.8 h. In deployment 2 an intermittent oxygen J I

peak created two phases of oxygen decline (Riedel et al., 2008b). H2S development oc- Back Close 20 curred in 10 of the 11 deployments after onset of anoxia, with final values (average over last hour of deployment) reaching 167.6 µM (except deployment 11 with an intermittent Full Screen / Esc peak of 300 µM). Temperature within a particular deployment remained constant (range ◦ across all experiments 17.6 to 21. 4 C), bottom salinity was 38 psu. Bottom water pH Printer-friendly Version dropped from 8.2 to a mean of 7.8 (minimum 7.5). Figure 2 illustrates the course of Interactive Discussion 25 a representative deployment based on average values from Table A1.

14342 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion 3.2 Macrofauna behaviour BGD Hypoxia elicited clear, visible reactions in all organisms. These reflected increasing re- sponse to decreasing oxygen values and/or increasing duration of anoxia. Three main 10, 14333–14438, 2013 types of reactions were evident: altered activity levels and new (stress) behaviours; 5 altered interactions; distinct sensitivities and tolerances. Anoxia and macrofauna 1. Altered activity levels and atypical behaviours: The first reactions typically involved behaviour an increase and/or decrease in the level of normal activities and/or initiation of atypical stress behaviours. Almost all species showed a sequence of behaviours B. Riedel et al. to decreasing oxygen concentrations. For details see Figs. A1–A33 and text be- 10 low (Sect. 3.2.1–3.2.7), for a synthesis see Fig. 7. Importantly, within a species, almost all individuals’ behaviours showed a nearly identical sequence. Most be- Title Page haviours were clearly related to specific oxygen thresholds/categories (Fig. 3). This was supported by the results from deployment 2, where atypical behaviours Abstract Introduction were interrupted during the temporary re-oxygenation and then resumed again at Conclusions References 15 renewed hypoxia (e.g. Alpheus glaber (Fig. A15); deployment details see Riedel et al., 2008b). Whereas epifauna typically showed first responses at early, mild Tables Figures hypoxia, the first visible response of the macroinfauna (emergence) started at moderate hypoxia (exceptions: bivalve Corbula gibba, brittle star Ophiura spp.). J I

2. Altered intra- and interspecific interactions: This included the weakening of de- J I 20 fensive (i.e. hiding and covering behaviour) and territorial behaviour as well as Back Close altered predator–prey interactions, including unusual interactions and encounters (see Sect. 3.3). Full Screen / Esc 3. Sensitivity and tolerance: our experiments revealed a distinct sequence of mor- Printer-friendly Version tality, reflecting the sensitivity and tolerance of the species and higher taxa to 25 decreasing oxygen concentrations and anoxia duration (see Sect. 3.4). Interactive Discussion

14343 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion 3.2.1 BGD All percent values below refer to mean percent of observations of the respective be- haviour during the 5 oxygen categories. 10, 14333–14438, 2013

Calliactis parasitica (Couch, 1842), N = 6 Anoxia and macrofauna 5 Mutualistic symbiont associated with hermit crabs, with up to 3 specimens per occupied shell; sometimes also on living gastropods (Hexaplex trunculus). Column normally yel- behaviour low/buff with darker vertical stripes. Non-selective omnivorous suspension feeder that B. Riedel et al. also sweeps the sediment with its tentacles; main prey: gastropods and . – Normoxia: tentacle crown typically facing down, tentacles sweeping the sediment Title Page 10 as the crab walks about. – < 2.0 mLDOL−1: significant change in crown orientation from down- to upward Abstract Introduction (51 %; Fig. A1d). Marked increase in opened tentacle crowns in all individuals Conclusions References (90 %; Fig. A1b). Sporadic slight body contractions (i.e. column diameter con- stricted or inflated; Fig. A1f). Tables Figures −1 15 – < 1.0 mLDOL : peak upward orientation, tentacle crowns started to close again more often (Fig. A1c). Mouth occasionally “puckered”; increased pharynx protru- J I

sion (Fig. A1h). J I −1 – < 0.5 mLDOL : significant increase in body contractions and body rotations Back Close (Fig. A1g) (36 and 22 %, respectively); pharynx protrusion reached 43 %. Col- 20 umn turned greyish (Fig. A1a); at near-anoxia, periderm in one individual started Full Screen / Esc to peel off and acontia discharged. Printer-friendly Version – Anoxia: initially (no H2S present), peak body contraction and rotation. With in- creasing H2S (ca. 30 µM), however, visible decrease in these activities: body re- Interactive Discussion laxed, tentacle crowns (either half open or closed) slightly moved/pulsated, rota- 25 tions almost ceased; only weak body contractions. Two individuals detached from 14344 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion shell and fell to sediment, another individual discharged its acontia. Four individ- uals died after 47.4 to 65.6 h of anoxia (H2S range: 56.3–96.1 µM), two survived BGD 25.1 h of anoxia (final H S 124.5 µM). 2 10, 14333–14438, 2013 pedunculatus (Pennant, 1777), N = 17 Anoxia and 5 Sea anemone buried in sediment, with tentacle crown flat on sediment surface; some macrofauna specimens integrated into epifaunal aggregations. Opportunistic omnivorous suspen- behaviour sion feeder on organic detritus but also on mobile prey (mainly amphipods and de- capods) that blunder into its tentacles. B. Riedel et al.

– Normoxia: Specimens touched, e.g. by passing crabs, closed crown and briefly 10 retracted into sediment. Title Page −1 – < 2.0 mLDOL : minor extensions (i.e. slightly above sediment surface; Fig. A2h); Abstract Introduction tentacle crowns increasingly stayed open when touched (57 %, Fig. A2b); retrac- tion into sediment dropped from 33 to 20 % (Fig. A2d). Conclusions References – < 1.0 mLDOL−1: significantly increase in minor extension (21 to 60 %). Crowns Tables Figures 15 largely open, increased body contractions (Fig. A2e). Gradual discolouration (paler) of tentacles and oral disc (Fig. A2a). J I −1 – < 0.5 mLDOL : major extension (parts of column clearly visible) significantly in- J I creased (51 %); strong body contractions and rotations pendulating in all direc- Back Close tions (Fig. A2f); peak pharynx protrusion (29 %, Fig. A2g). Full Screen / Esc 20 – Anoxia: sharp increase in half-open and closed crowns (combined: 61 %; Fig. A2c). Body contractions and rotations continued until end of deployments. Printer-friendly Version All individuals survived (maximum anoxia duration 81.8 h; max. H2S concentra- tion 279 µM). Interactive Discussion

14345 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion 3.2.2 Nemertini and Sipunculida BGD Tubulanus sp., N = 1 10, 14333–14438, 2013 Mobile, infaunal nemertean; predator on muddy sublittoral bottoms.

– Normoxia: not visible on sediment surface. Anoxia and macrofauna −1 5 – < 2.0 mLDOL : not visible. behaviour −1 – < 1.0 mLDOL : not visible. B. Riedel et al. – < 0.5 mLDOL−1: not visible.

Title Page – Anoxia: One large individual (ca. 40 cm) emerged 18 h after onset of anoxia (H2S 33.3 µM) (Fig. A3a) and then moved about on sediment or squirmed in place (75 Abstract Introduction 10 and 21 %, respectively; Fig. A3b). On two occasions the nemertean was under and in direct contact with an emerged infauna sea urchin (Schizaster canaliferus; Conclusions References total interaction time ca. 1 h), and also crawled under a holothurian (Ocnus planci; Tables Figures > 12 min). At 26.4 h of anoxia (H2S 41.7 µM) it disappeared from view (i.e. mortal- ity or survival not determined). J I 15 Sipunculida indet., N = 4 J I

– Normoxia: infaunal animal, not visible on sediment surface. Back Close −1 – < 2.0 mLDOL : not visible. Full Screen / Esc – < 1.0 mLDOL−1: not visible. Printer-friendly Version – < 0.5 mLDOL−1: one individual emerged at transition from severe hypoxia to Interactive Discussion 20 anoxia (hypoxia duration 33.5 h) and showed minor movements and squirming in place.

14346 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion – Anoxia: three individuals emerged 7.6, 17.5 and 34.2 h after onset of anoxia (H2S 34.9, 83.2 and 243.2 µM) (Fig. A4a). Most moved only short distances (5 %; BGD Fig. A4b), tending to then squirm in place (41 %; Fig. A4b) rather than move about. 10, 14333–14438, 2013 Two individuals disappeared from view only 30 and 108 min after emergence (i.e. 5 anoxia 9.5 and 34.8 h) and may have reburied themselves; other two specimens visible on sediment surface until end of deployment (anoxia duration 24.2 and Anoxia and 25.1 h, final H2S 18.2 and 124.5 µM, respectively). macrofauna behaviour 3.2.3 Mollusca B. Riedel et al. Diodora sp., N = 4

10 Keyhole limpets are herbivores and browsing carnivores on hard substrata and typical Title Page inhabitants of multi-species clumps. Abstract Introduction – Normoxia: Only 2 of overall 4 specimens visible because of their cryptic position on multi-species clumps or cover by brittle star aggregations (Fig. A5a). Individu- Conclusions References als quite stationary (Fig. A5b). Tables Figures −1 15 – < 2.0 mLDOL : no significant change in behaviour. J I – < 1.0 mLDOL−1: visibility significantly increased to 72 % (Fig. A5a), with one indi- −1 vidual emerging from under an ascidian at 0.7 mLDOL . Combination of foot ex- J I tension (Fig. A5d) and arm-tipping brittle stars Ophiothrix quinquemaculata (see Back Close below) simplified recognition of limpets. One individual crawled onto a hermit crab 20 (Paguristes eremita) inhabited shell occupied by 3 anemones (Calliactis parasit- Full Screen / Esc ica). The limpet was in direct contact with the column of two of these anemones for 3.3 h. At this point, crab extended from shell and motionless. Then, limpet Printer-friendly Version movement caused crab’s shell to overturn over a period of 48 min. Interactive Discussion – < 0.5 mLDOL−1: fourth specimen visible. All individuals started to flip over or fall 25 off from their substrate, i.e. shell overturned in 33 % of observations (Fig. A5c). 14347 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion Foot extension peaked (37 %; Fig. A5d). One individual climbed atop a sea urchin (Psammechinus microtuberculatus) for 12 min before falling off at border BGD to anoxia. Second individual, on hermit crab shell, remained firmly attached for 10, 14333–14438, 2013 26.2 h, again in contact with both the anemones and the hermit crab, which re- 5 peatedly touched the limpet with its pereopods and claws. First mortality shortly before onset of anoxia (45.7 h of hypoxia). Anoxia and macrofauna – Anoxia: Remaining three individuals flipped over (76 %). The limpet that fell off behaviour the sea urchin uprighted itself 1 h later, before again falling over and remaining so until end of experiment 4.2 h later. Individual on hermit crab gradually loosened its B. Riedel et al. 10 attachment and exposed most of its foot for 5.6 h, before falling off onto sediment, after which it no longer moved despite being touched repeatedly by crab and its anemones. Two individuals died (2.4 and 11 h of anoxia; H2S 46.6 and 5.6 µM), Title Page one specimen survived (albeit in deployment with second shortest anoxia: 8.5 h, Abstract Introduction no H2S). Conclusions References 15 Fusinus rostratus (Olivi, 1792), N = 1 Tables Figures Common predatory fasciolariid gastropod on Northern Adriatic sublittoral soft bottoms.

– Normoxia: The single detected individual well visible on sediment surface J I (Fig. A6a); horizontal locomotion negligible (3 %, Fig. A6c). J I – < 2.0 mLDOL−1: as under normoxia. Back Close −1 20 – < 1.0 mLDOL : as under normoxia, but peak horizontal locomotion (29 %). Full Screen / Esc – < 0.5 mLDOL−1: animal climbed higher on a multi-species clump; after short loco- motion phase, remained stationary. Foot/head alternately extended and retracted. Printer-friendly Version Ultimately fell down and less often visible (Fig. A6b). Interactive Discussion – Anoxia: visibility drops further (to 50 %), with second peak in horizontal locomotion 25 (17 %). In 51 % of observations on top of epifaunal aggregation; during stationary 14348 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion phases, foot/head visible. After 40.6 h of anoxia (H2S 191.6 µM), animal disap- peared from view (mortality or survival not determined). BGD

Hexaplex trunculus (Linnaeus, 1758), N = 23 10, 14333–14438, 2013

Abundant and widespread muricid gastropod in the Northern Adriatic, exhibiting multi- Anoxia and 5 ple strategies on bivalve prey. One of the few species in which the experimen- macrofauna tal design itself played a role in the behavioural response: by crawling up the plexiglas behaviour walls, Hexaplex took advantage of the highest available place (chamber lid) to initially seek refuge; i.e. number of individuals on top is an experimental artefact. Nonetheless, B. Riedel et al. results mirror the species-typical response reaction because at oxygen depletion, mu- 10 ricids climb atop bioherms (Stachowitsch, 1984), i.e. the avoidance reaction per se is the same. Title Page

– Normoxia: animals visible in 40 % of observations (Fig. A7a), mostly on sedi- Abstract Introduction

ment/under bioherms, i.e. do not crawl up plexiglas wall (Fig. A7b). Conclusions References −1 – < 2.0 mLDOL : first animals started to crawl up chamber wall: minimal increase Tables Figures 15 in vertical movement (7 %, Fig. A7c) reflects the few but often major moves, leav- ing animals on chamber lid. J I – < 1.0 mLDOL−1: increased tendency to be higher up in chamber. J I – < 0.5 mLDOL−1: location on top of chamber peaked (71 %); the few individuals Back Close visible at the sediment surface started to protract and/or retract their foot/head 20 (Fig. A7d). Full Screen / Esc – Anoxia: at end of deployments 16 animals not visible on lid, 7 individuals fell Printer-friendly Version to sediment from lid or bioherm, i.e. increase in visibility to pre-hypoxia values (44 %); peak in foot protractions/retractions (11 and 24 %, respectively). H. truncu- Interactive Discussion lus was among the species with the highest survival rates, i.e. only two mortalities 25 at 46.3 and 51.5 h of anoxia (117.1 and 199.9 µM H2S, respectively). Survivors 14349 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion (max. anoxia duration 81.8 h; final H2S 167.6 µM) also included specimens which did not seek refuge at chamber top but remained on sediment surface or bioherms BGD throughout. 10, 14333–14438, 2013 Murex brandaris (Linnaeus, 1758), N = 1 Anoxia and 5 Spiny dye-murex: occurs regularly on Northern Adriatic muddy bottoms. macrofauna – Normoxia: as in Hexaplex trunculus, visible in 43 % of observations (Fig. A8a). As behaviour in all categories, stronger horizontal than vertical movements (Fig. A8c). B. Riedel et al. – < 2.0 mLDOL−1: animal increasingly often visible. −1 – < 1.0 mLDOL : peak horizontal movement (69 %). Title Page −1 10 – < 0.5 mLDOL : significant decrease in horizontal movement to 9 %, but animal Abstract Introduction moved higher up on plexiglass wall (i.e. location high/top: 23 %, Fig. A8b). Conclusions References – Anoxia: animal remained on plexiglass wall with no movement. Specimen sur- Tables Figures vived (albeit in deployment with shortest anoxia: 5.2 h, final H2S 5.5 µM).

Abra alba (Wood, 1802), N = 2 J I

J I 15 Infaunal, deposit-feeding bivalve common in Northern Adriatic. Back Close – Normoxia: not visible. Full Screen / Esc – < 2.0 mLDOL−1: not visible. −1 – < 1.0 mLDOL : not visible. Printer-friendly Version −1 – < 0.5 mLDOL : animals emerged (Fig. A9a) and made a series of short moves Interactive Discussion 20 on the sediment (Fig. A9b). Siphons visible (35 %, Fig. A9c).

14350 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion – Anoxia: animals on surface, locomotion ceased, siphon visible only in 1 individual, which was pushed aside by hermit crab (no predation/scavenging). Both individ- BGD uals died (duration of anoxia 20.6 and 34.6 h, H S 33.3 and 244 µM). 2 10, 14333–14438, 2013 Chlamys varia (Linnaeus, 1758), N = 7 Anoxia and 5 Suspension-feeding, epifaunal bivalve, typically bysally-attached to bioherms. macrofauna – Normoxia: animals in feeding position with normal (open) shell gape and mantle behaviour tissue visible (97 and 99 %, Fig. A10a and c). B. Riedel et al. – < 2.0 mLDOL−1: feeding position maintained, mantle tissue increasingly swollen (Fig. A10d). −1 −1 Title Page 10 – < 1.0 mLDOL : as above. One juvenile died at 0.8 mDOL . Abstract Introduction – < 0.5 mLDOL−1: peak mantle tissue swelling (20 %), first individuals showed tis- −1 sue retraction (Fig. A10e). Second individual died at DO 0.2 mLL . Conclusions References

– Anoxia: wide shell gape (60 %, Fig. A10b) and strongly retracted mantle tissue Tables Figures (64 %). Three individuals died after 14 to 31.7 h of anoxia (median H2S 13.7 µM), 15 two others survived 19.1 and 22.9 h of anoxia (final H S 19.3 and 5.2 µM, respec- 2 J I tively). J I Corbula gibba (Olivi, 1792), N = 37 Back Close Highly abundant, shallow infaunal, suspension-feeding bivalve. Full Screen / Esc – Normoxia: animals started to appear on surface at lower boundary of normoxia 20 category (11 %, Fig. A11a) and showed peak minor and major horizontal move- Printer-friendly Version ment (Fig. A11b; total horizontal locomotion 43 %). Interactive Discussion – < 2.0 mLDOL−1: number of animals appearing at the surface increased, with sig- nificant decrease in horizontal locomotion. 14351 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion – < 1.0 mLDOL−1: overall number of individuals increased, but some re-buried or moved under bioherms. BGD – < 0.5 mLDOL−1: number of animals unchanged. 10, 14333–14438, 2013 – Anoxia: highest number of individuals on surface, no horizontal movement. One Anoxia and 5 individual manipulated by hermit crab Paguristes eremita but then re-buried itself (no predation/scavenging). Another individual raised from sediment surface by macrofauna emerging infaunal sea urchin (Schizaster canaliferus). All animals survived (max. behaviour anoxia duration 78.3 h; max. H S 124.5 µM). 2 B. Riedel et al. Venerupis cf. rhomboides, N = 1

Title Page 10 Suspension-feeding, infaunal bivalve, widely distributed in the Northern Adriatic. – Normoxia: not visible. Abstract Introduction – < 2.0 mLDOL−1: not visible. Conclusions References −1 – < 1.0 mLDOL : not visible. Tables Figures – < 0.5 mLDOL−1: First the sediment bulged, the siphon became visible (Fig. A12c) J I 15 and finally the whole animal emerged (Fig. A12a). Siphon always visible, foot only

occasionally, with peak horizontal locomotion (total 15 %, Fig. A12b). J I

– Anoxia: strong siphon vs. foot visibility points to greater energy investment in seek- Back Close ing more oxygenated water than in locomotion. Mortality after 24.5 h anoxia (H2S 111.4 µM). Full Screen / Esc

20 3.2.4 Polychaeta Printer-friendly Version

Polychaeta indet. including Glycera sp., N = 17 Interactive Discussion

– Normoxia: not visible. 14352 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion – < 2.0 mLDOL−1: not visible. BGD – < 1.0 mLDOL−1: animals started to emerge (Fig. A13a), peak squirming in place (32 %, Fig. A13b). 10, 14333–14438, 2013 – < 0.5 mLDOL−1: overall number of individuals increased, two individuals disap- −1 Anoxia and 5 peared from view (DO < 0.3 mLL ) and may have reburied themselves, two oth- macrofauna ers died at transition from severe hypoxia to anoxia. Peak horizontal locomotion behaviour (19 %) and squirming continued. – Anoxia: peak in animals visible at the surface, some individuals tried to climb B. Riedel et al. up plexiglass wall or along sensors, but locomotion and squirming gradually de- 10 creased. Two animals successfully re-buried, two disappeared from view (i.e. mor- Title Page tality or survival not determined), seven individuals died (median anoxia duration 9.4 h, H2S ranged: 9–34.9 µM) and one survived (max. anoxia duration 25.1 h, Abstract Introduction max. final H2S 124.5 µM). Glycera died 21.3 h after onset of anoxia (H2S 32.8 µM), discolouring the immediate sediment red. Conclusions References

Tables Figures 15 Protula tubularia (Montagu, 1803), N = 8

Solitary tubeworm in calcareous tubes on hard substrate; head bears two sets of red J I slightly spiralled, pinnate tentacles; no operculum. J I

– Normoxia: tentacle crown typically extended in filter-feeding position (Fig. A14a). Back Close Contact with mobile organisms (e.g. crabs crawling on top of tube) caused crown Full Screen / Esc 20 closure and partial or full retraction into tube. −1 – < 2.0 mLDOL : tentacle crowns increasingly extended (80 %), retraction into Printer-friendly Version tube gradually ceased (18 %, Fig. A14b). Interactive Discussion – < 1.0 mLDOL−1: crown condition unchanged.

14353 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion – < 0.5 mLDOL−1: retraction sharply increased from 20 to 68 %. One individual died −1 shortly before onset of anoxia (oxygen concentration 0.2 mLL , no H2S). BGD – Anoxia: Remaining seven individuals died between 2.2 and 42.3 h of anoxia 10, 14333–14438, 2013 (max. H2S 253.2 µM); 2 individuals fully re-emerged from tube (anoxia 24 h, H2S 5 ∼ 40 µM) before mortality (crown relaxation). Anoxia and macrofauna 3.2.5 behaviour

Alpheus glaber (Olivi, 1792), N = 2 B. Riedel et al.

Small deposit feeding pistol shrimp inhabiting burrows in sediment. Predated mainly by

fish and larger decapods, i.e. Nephrops norvegicus. Title Page

10 – Normoxia: images show only one burrow opening of the two pistol shrimps (prob- Abstract Introduction able male–female partners; P. Dworschak, personal communication, 2013). No individual visible at opening or elsewhere on sediment surface. Opening visibly Conclusions References −1 larger shortly before onset of hypoxia (2.4 mLDOL ). Tables Figures – < 2.0 mLDOL−1 (hypoxic phase 1, before intermittent oxygen peak): opening fur- −1 15 ther enlarged after 4 h of hypoxia (oxygen concentration 1.6 mLL ). Shortly be- J I fore onset of moderate hypoxia (1.3 mLDOL−1), one individual partly visible (che- lipeds and carapace; Fig. A15a). The shrimp appeared briefly in irregular intervals J I at the opening before retreating tail-first again (i.e. when disturbed by approach- Back Close ing hermit crab Paguristes eremita). During re-oxygenation (intermittent oxygen Full Screen / Esc 20 peak), no pistol shrimps visible. −1 – < 1.0 mLDOL (hypoxic phase 2, after re-oxygenation): one individual re- Printer-friendly Version appeared at opening. Interactive Discussion – < 0.5 mLDOL−1: one individual left burrow, staying only a few body lengths away from opening. Subsequent burst in activity (i.e. constant horizontal locomotion 14354 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion across whole chamber area; DO < 0.4 mLL−1, Fig. A15b). Fell over on its side (Fig. A15c) after briefly raising body (0.2 mLDOL−1). Extremity movement contin- BGD −1 ued for ca. 1 h, followed by mortality (0.2 mLDOL ). Second individual visible at 10, 14333–14438, 2013 0.4 mLDOL−1, left burrow 7 h later (0.3 mLDOL−1). Shortly thereafter it also fell 5 on its side (but only in 1 image, i.e. < 6 min), followed by a brief locomotion phase on sediment. Anoxia and macrofauna – Anoxia: after ca. 30 min anoxia (H2S 0.6 µM), second individual again fell over and behaviour died (4.5 h after specimen 1). Fragmention visible 6 h later. B. Riedel et al. Ebalia tuberosa (Pennant, 1777), N = 3

10 Cryptic, night-active crab, temporarily embedded in sediment, leaving anteriormost Title Page carapace tip protruding. Feeds on small invertebrates (mainly annelids and small crus- taceans) but also on dead and moribund organisms. Abstract Introduction

Conclusions References – Normoxia: all individuals buried in sediment, i.e. not visible. Tables Figures – < 2.0 mLDOL−1: first individual visible on sediment surface at 1.38 mLDOL−1, 15 moving along plexiglass chamber walls. J I – < 1.0 mLDOL−1: second individual emerged from sediment at 0.63 mLDOL−1, both crabs with strong horizontal locomotion (77 %, Fig. A16c) on sediment. J I – < 0.5 mLDOL−1: all three individuals visible (Fig. A16a). Horizontal locomotion Back Close dropped rapidly to 42 %, small peak in vertical locomotion as crabs start to climb Full Screen / Esc 20 onto higher/top positions on bioherms (Fig. A16c), where they remained almost

inactive (except for extremity movement, data not shown). Printer-friendly Version

– Anoxia: total locomotion dropped to 10 % (Fig. A16b), while body movement Interactive Discussion peaked (40 %, Fig. A16d). Individuals on bioherms in 36 % of observations (Fig A16e). Two individuals survived 14.1 h and 23.6 h of anoxia and H2S values of 14355 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion 12.8 and 19.2 µM, respectively; one individual died after 22.9 h of anoxia (H2S 16.7 µM). BGD

Ethusa mascarone (Herbst, 1785), N = 3 10, 14333–14438, 2013

This crab camouflages its carapace with various objects, typically bivalve shells and Anoxia and 5 living sponges, held in place with last two pairs of pereopods. Can bury itself to hide macrofauna from predators, i.e. demersal fish. behaviour

– Normoxia: partly visible (i.e. including camouflage) in 79 % of observations B. Riedel et al. (Fig. A17a); “moving camouflage” on sediment surface clearly indicated horizontal locomotion (19 %, Fig. A17c). −1 Title Page 10 – < 2.0 mLDOL : hiding behaviour unchanged; total locomotion dropped to 13 %. – < 1.0 mLDOL−1: hiding behaviour unchanged; peak body movements (44 %, Fig Abstract Introduction A17d). Conclusions References −1 – < 0.5 mLDOL : peak total locomotion (27 %); all three individuals succes- Tables Figures sively discarded camouflage (i.e. camouflage still visible in 66 % of observa- 15 tions; Fig. A17b). One individual predated by sea anemone Calliactis parasticia −1 J I (0.4 mLDOL , no H2S) only 1.3 h after dropping its shell fragments (see also Sect. 3.3.2). The two other individuals, discarding their camouflage at 0.23 and J I 0.03 mLDOL−1, initially hid within bioherms. Back Close – Anoxia: One individual climbed up a sensor and disappeared from view; loco- Full Screen / Esc 20 motion and body movement of remaining specimen nearly ceased, with mortality 7.5 h after onset of anoxia (no H S). 2 Printer-friendly Version

Eurynome aspera (Pennant, 1777), N = 2 Interactive Discussion Decorator crab that attaches , sponges etc. onto its carapace. 14356 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion – Normoxia: visible on sediment in 53 % of observations (Fig. A18a); horizontal locomotion clearly dominated over vertical locomotion (38 vs. 11 %; Fig. A18b). BGD – < 2.0 mLDOL−1: no significant change in locomotion; peak body and extremity 10, 14333–14438, 2013 movement (34 and 17 %, respectively; Fig. A18c and d). −1 5 – < 1.0 mLDOL : locomotion largely unchanged, body and extremity movement Anoxia and slightly dropped. macrofauna behaviour – < 0.5 mLDOL−1: in 80 % of observations, individuals on high/top location (Fig. A18e), locomotion and extremity movements almost ceased, only body B. Riedel et al. −1 movements (18 %). One individual died at 0.2 mLDOL (no H2S).

10 – Anoxia: second individual disappeared from view 5.1 h after onset of anoxia (no Title Page H2S; mortality or potential survival not determined). Abstract Introduction Galathea spp., N = 3 Conclusions References

Small, cryptic squat lobsters in rocky subtidal and on secondary hard bottoms. Primarily Tables Figures night-active (hidden in small groups in interstices of bioherms during daytime).

15 – Normoxia: visible in 20 % of observations (Fig. A19a), otherwise hidden; peak J I horizontal locomotion (76 %; Fig. A19b). J I −1 – < 2.0 mLDOL : visibility increased to 50 %. Horizontal locomotion dropped to Back Close 54 %, individuals increasingly moved onto higher substrates (Fig. A19d). One in- dividual disappeared from view after 5.6 h of hypoxia (1.2 mLDOL−1). Full Screen / Esc −1 20 – < 1.0 mLDOL : peak vertical locomotion and body movement (Fig. A19c); two Printer-friendly Version remaining crabs retreated to base of bioherms. Interactive Discussion – < 0.5 mLDOL−1: visibility 59 %, locomotion nearly ceased, body movement dropped to 14 %. One individual died at 0.3 mLDOL−1 (17.8 h of hypoxia), 14357 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion the second individual 3 h later at transition from severe hypoxia to anoxia −1 (0.03 mLDOL , no H2S). BGD

Inachus sp., N = 1 10, 14333–14438, 2013

Spider crab had sponges attached to its carapace and initially hid under tentacles of Anoxia and 5 sea anemone Cereus pedunculatus. macrofauna – Normoxia: Visible in 49 % of observations, mainly on sediment surface behaviour (Fig. A20a). Horizontal locomotion prevailed over vertical (33 vs. 4 %, Fig. A20b); B. Riedel et al. body and extremity movement 38 and 23 %, respectively (Fig. A20c and d). – < 2.0 mLDOL−1: visibility increased to 100 %. Total locomotion remained un- Title Page 10 changed (37 %), but slight shift toward increasing vertical locomotion (crab moved

onto base of a bioherm). Peak body movement (46 %), slight decrease in extrem- Abstract Introduction ity movement (17 %). Conclusions References – < 1.0 mLDOL−1: visibility unchanged. Both horizontal and vertical locomotion dropped (total locomotion decreased to 15 %). Tables Figures −1 15 – < 0.5 mLDOL : visibility unchanged. Crab retreated to top of bioherm (72 %). Body movement decreased to 30 %, extremity movement nearly ceased. J I – Anoxia: sharp decrease in locomotion, body and extremity movement (visible in J I 84 % of observations). Moribund crab then dragged down to sediment by a dying Back Close brittle star and died shortly thereafter (12.1 h of anoxia, no H2S). Full Screen / Esc

20 Macropodia spp., N = 7 Printer-friendly Version The 7 decorator crabs in this study were rarely covered (if so, then with sponges). Interactive Discussion – Normoxia: crabs visible in 50 % of observations (Fig. A21a), mostly lower on a bio- herm rather than on sediment. More horizontal than vertical locomotion (24 vs. 14358 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion 8 %, respectively; Fig. A21b), body movement moderate 33 % (Fig. A21c), ex- tremity movement low (12 %). BGD −1 – < 2.0 mLDOL : sharp increase in visibility (88 %), accompanied by significant in- 10, 14333–14438, 2013 crease in locomotion (horizontal: 30 %, vertical: 24 %) and movement onto higher 5 substrates (25 %, Fig. A21e). Anoxia and – < 1.0 mLDOL−1: crabs increasingly climbed to higher/top positions on bioherms macrofauna (65 %) and stayed there, often in aggregation with/close to other crabs such as behaviour Pisidia longicornis and spinifer (see also Sect. 3.3.1 Aggregation and aggressive behaviour). Total locomotion dropped slightly (from overall 54 to 48 %), B. Riedel et al. 10 body movements peaked (35 %) while extremity movement gradually decreased. −1 – < 0.5 mLDOL : significant drop in horizontal (from 31 to 7 %) and vertical loco- Title Page motion (from 17 to 3 %), body and extremity movement (from 35 and 5 % to 15 and 3 %, respectively). In 69 % of observations, crabs positioned atop bioherms. Abstract Introduction −1 Three individuals died at DO 0.4, 0.3 and 0.1 mLL (14.9, 15.8 and 19.9 h of Conclusions References 15 hypoxia, no H2S), either falling dead to the sediment or being dragged down by moribund brittle stars and dying shortly thereafter on the sediment. Tables Figures – Anoxia: locomotion, body and extremity movement of remaining 4 individuals al- J I most ceased; all individuals died between 3.3 to 9.8 h of anoxia (H2S recorded only once: 0.8 µM). J I

Back Close 20 Nepinnotheres pinnotheres (Linnaeus, 1758), N = 2

Full Screen / Esc Small parasitic pea crab typically inhabiting ascidians (in this study both female speci- mens inhabited Microcosmus spp.) and bivalves, feeding on the particulate food of its host as well as on other filtered organisms. Printer-friendly Version – Normoxia: not visible. Interactive Discussion −1 25 – < 2.0 mLDOL : not visible. 14359 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion – < 1.0 mLDOL−1: not visible. BGD – < 0.5 mLDOL−1: shortly before onset of anoxia, both crabs became visible (Fig. A22a) and moved (Fig. A22b) within the atrial siphon of the ascidians 10, 14333–14438, 2013 (Fig. A22d) but did not leave. Anoxia and 5 – Anoxia: after abandoning their hosts 13.6 and 19.4 h after anoxia onset (H2S 18.3 and 93.9 µM, respectively), both individuals remained at a higher position (63 %) macrofauna or hid for shorter periods elsewhere in bioherm. Locomotion (horizontal: 30 %, behaviour vertical: 28 %) and body movements (22 %, Fig. A22c) occurred throughout the B. Riedel et al. anoxic period. Both individuals survived until the end of the respective deployment 10 (anoxia duration: 24.6 h and 78 h, final H2S: 126.1 and 111.6 µM). Title Page Paguristes eremita (Linnaeus, 1767), N = 25 Abstract Introduction Abundant hermit crab species in this community. Highly mobile, day-active preferring juvenile macrofauna and typically carrying numerous symbionts. Conclusions References

– Normoxia: mainly on sediment or partly hidden under multi-species clumps. Shells Tables Figures 15 oriented with aperture facing down, crabs only partially protruding from shell (ex- cept during intra- and interspecific interactions). More locomotion during day than J I at night (for details on circadian rhythm see Pretterebner et al., 2012). J I – < 2.0 mLDOL−1: locomotion dropped from 23 to 14 % (Fig. A23b) and the day and Back Close night rhythm dampened. The crabs increasingly climbed onto bioherms (47 %, 20 Fig. A23a). Body movement increased almost two-fold to 51 % (Fig. A23c); body Full Screen / Esc posture changed (Fig. A23d), with single individuals starting to extend from shell (Fig. A23e). Printer-friendly Version −1 – < 1.0 mLDOL : number of observations with individuals on sediment and on Interactive Discussion bioherms almost equal. Body movement peaked (70 %); extension from shell in- 25 creased from 15 to 35 %. Typical shell orientation maintained (Fig. A23f). 14360 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion – < 0.5 mLDOL−1: some individuals moved back down to sediment, but locomotion almost ceased (5 %). Marked drop in body movement (from 70 to 40 %). Shell BGD orientation changed significantly, with overturned shells (aperture facing up) in 10, 14333–14438, 2013 17 % of observations.

5 – Anoxia: extension from shell reached 40 %; 13 of 25 individuals emerged from Anoxia and shell (Fig. A23e) and walked around (sediment, bioherms). One specimen re- macrofauna turned to its shell but re-emerged after 15 min and finally climbed on an exposed behaviour infaunal sea urchin Schizaster canaliferus. Overall, 9 crabs died (anoxia duration: 18.4 to 62.1 h, H2S range 116.5 to 248 µM), 8 of which were outside their shell B. Riedel et al. 10 on sediment. Thirteen individuals survived (maximum anoxia duration 25.1 h; H2S 124.5 µM), 9 of which were on sediment and 4 on bioherms. Death or survival of 3 individuals undetermined (i.e. disappeared from view, poor visibility). Title Page

Pilumnus spinifer (H. Milne-Edwards, 1834), N = 17 Abstract Introduction Conclusions References Territorial crab, cryptic resident in sponge-dominated bioherms, hiding during day and 15 searching for prey at night. Feeds mainly on juvenile macroepibenthic organisms but Tables Figures also on small adult crabs (i.e. Pisidia longimana) or brittle stars. – Normoxia: visibility typically reflects night-time activity (16 % of observations, J I Fig. A24a), with peaks in horizontal locomotion (48 %, Fig. A24b) and body move- J I ment (26 %, Fig. A24c). Movement mainly on sediment surface or lower on bio- Back Close 20 herms. – < 2.0 mLDOL−1: visibility increased (49 %) because the normal day–night rhythm Full Screen / Esc waned; horizontal locomotion declined significantly to 36 %, while vertical locomo- tion increased as individuals climbed higher up on bioherms (significant increase Printer-friendly Version from 2 to 25 %, Fig. A24d). Interactive Discussion −1 25 – < 1.0 mLDOL : visibility further rose to 79 %; significant increase in vertical lo- comotion reflected in peak values of individuals atop elevated substrates (51 %). 14361 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion Intra- and interspecific aggression maintained, i.e. dominant individuals chased subordinate individuals or other crabs such as Macropodia spp. away. BGD – < 0.5 mLDOL−1: locomotion and body movement significantly decreased, intra- 10, 14333–14438, 2013 and interspecific aggression ceased and predator–prey relationships changed: 5 Pilumnus no longer attacked closely adjoining prey; instead, they aggregated with Anoxia and other individuals, for example the crab Pisidia longicornis and small invertebrates macrofauna atop bioherms (see also Sect. 3.3.1). Four individuals died at transition from se- behaviour vere hypoxia to early anoxia (no H2S present): they turned over and fell from their elevated positions. B. Riedel et al.

10 – Anoxia: locomotion and body movement of remaining 13 individuals almost

ceased. Twelve individuals died (anoxia duration 1.4 to 23.6 h, H2S from 0 to Title Page 72.8 µM); one individual survived brief anoxia (8.5 h; no H2S). Abstract Introduction Pisidia longimana (Risso, 1816), N = 4 Conclusions References Small porcellanid crab constituting the major component of decapod community abun- Tables Figures 15 dance in bioherms; hides in cavities during daytime; prey for bigger crustaceans (i.e. P. spinifer) and fish. Behavioural reactions are based on 4 larger and conspicuous in- dividuals, mortality on 150 individuals. J I

– Normoxia: visible during night (21 %, Fig. A25a) and, in 44 % of observations, on J I high/top positions of bioherms (Fig. A25d). Initial high locomotion (total locomotion Back Close 20 76 %) reflects night-time activity (for details on circadian rhythm see Haselmair et al., 2010). Full Screen / Esc −1 – < 2.0 mLDOL : day-night rhythm waned, i.e. visibility increased (to 37 %); crabs Printer-friendly Version located in bioherm mid-height (up to 5 cm above sediment, data not shown) rather than at high/top positions. Interactive Discussion

14362 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion – < 1.0 mLDOL−1: daytime hiding abandoned, total locomotion dropped signifi- cantly to 40 % (horizontal: 30 %, vertical 10 %; Fig. A25b), whereas body move- BGD ment peaked (30 %, Fig. A25c). 10, 14333–14438, 2013 – < 0.5 mLDOL−1: increasing aggregation on high/top positions, often atop vagile 5 fauna (e.g. Fig. 4a) such as sea urchins or the holothurian Ocnus planci. 57 % of Anoxia and the individuals died at transition from severe hypoxia to early anoxia (maximum macrofauna H2S 0.7 µM), turning over or falling from bioherms to sediment. behaviour

– Anoxia: activity of remaining moribund 64 individuals ceased; all individuals dead B. Riedel et al. after 11.2 h of anoxia, no significant H2S concentration.

10 3.2.6 Echinodermata Title Page

Ocnus planci (Brandt, 1835), N = 4 Abstract Introduction

Suspension-feeding holothurian commonly attached to bioherms. Conclusions References

– Normoxia: tentacle crowns mostly upward orientated (Fig. A26c) and open (both Tables Figures 56 %), no tentacular movements. Otherwise, sideward/horizontal orientation and

15 closed crown (Fig. A26b) dominated (43 and 40 %, respectively). J I – < 2.0 mLDOL−1: upward orientated crown positions peaked (64 %). Half-open J I tentacle crowns increased markedly from 5 to 18 % (Fig. A26a) and minor body elongation started, i.e. posterior body tapered and started to elongate (38 %, Back Close Fig. A26e). Full Screen / Esc −1 20 – < 1.0 mLDOL : significant drop in upward orientation, crowns predominantly half open or closed (24 and 42 %, respectively). Minor body elongation reached 61 %. Printer-friendly Version −1 – < 0.5 mLDOL : significant increase in major body elongation (64 %), with total Interactive Discussion elongation peaking at 85 % (Fig. A26f). Crowns predominantly side- or downward orientated (51 and 23 %, respectively). 14363 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion – Anoxia: both downward orientation of tentacle crown and crown closure peaked (56 and 65 %). All individuals died: three after ca. 24 h of anoxia (H2S range 56.7 BGD to 91.2 µM), one individual 48.2 h after onset of anoxia. The latter started to de- 10, 14333–14438, 2013 compose ca. 4 h after death (H2S 199 µM): body started to inflate and become 5 covered with vesicles/blisters. Anoxia and Psammechinus microtuberculatus (Blainville, 1825), N = 17 macrofauna behaviour Common epifaunal deposit-feeding sea urchin. B. Riedel et al. – Normoxia: Visible in 54 % of observations (Fig. A27a), the remeinder hidden under bioherms. All visible individuals with camouflage (Fig. A27b). One individual left 10 frame of open configuration. Title Page −1 – < 2.0 mLDOL : peak visibility as animals move out from under bioherms. First Abstract Introduction individuals discard camouflage. One individual returned under bioherm (not visi- ble until end of deployment). Conclusions References – < 1.0 mLDOL−1: visibility decreased (3 individuals hid under bioherms, not visible Tables Figures 15 until end of deployment). J I – < 0.5 mLDOL−1: most animals discarded their camouflage (from 92 to 31 %), one after being climbed upon by predatory crab Pilumnus spinifer. Horizontal locomo- J I tion decreased. Eight individuals died (median DO 0.12 mLL−1). Back Close – Anoxia: No individual was camouflaged, horizontal locomotion ceased, remaining Full Screen / Esc 20 4 individuals died (median anoxia duration 5.9 h, max. H2S 5.6 µM).

Schizaster canaliferus (Lamarck, 1816), N = 22 Printer-friendly Version

Interactive Discussion Infaunal, deposit-feeding echinoid present in high densities in muddy soft-bottoms of the Northern Adriatic. 14364 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion – Normoxia: First sediment bulging visible when oxygen values approached 2 mLL−1. BGD – < 2.0 mLDOL−1: Sediment bulging increased significantly (Fig. A28a). 10, 14333–14438, 2013 – < 1.0 mLDOL−1: Peak sediment bulging (25 %), first animals appeared on sedi- 5 ment surface (Fig. A28b) and peak total locomotion (Fig. A28c), whereby major Anoxia and movements (Fig. A28d) dominated. macrofauna behaviour – < 0.5 mLDOL−1: Strong increase in emerged individuals, drop in total horizontal locomotion, whereby minor movements peaked. Six Schizaster died (median DO B. Riedel et al. 0.09 mLL−1).

10 – Anoxia: peak visibility, significant drop in locomotion. Some animals flipped over Title Page and spines began to droop. Eleven individuals died (median anoxia duration Abstract Introduction 14.3 h, median H2S 12.9 µM), five survived (max. 13.9 h anoxia, max. final H2S 11.8 µM). Conclusions References

Ophiothrix quinquemaculata (Delle Chiaje, 1828), N = 28 Tables Figures

15 The epifaunal brittle star is one of three designating species in this benthic community. Densely aggregated on bioherms; mostly stationary with arms extending upward in J I typical suspension-feeding position. J I

– Normoxia: arms almost only in suspension-feeding habitus (91 %, Fig. A29a); Back Close moderate locomotion on bioherm substrate (Fig. A29d). Full Screen / Esc −1 20 – < 2.0 mLDOL : suspension feeding significantly dropped to 28 %, individuals in- creasingly elevating their discs above substrate and standing on arm-tips (arm- Printer-friendly Version tipping: 49 %, Fig. A29b). Both horizontal and vertical locomotion on bioherms Interactive Discussion increased; single individuals briefly moved down on sediment but then returned to bioherm. 14365 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion – < 1.0 mLDOL−1: arm-tipping peaked (51 %) and, increasingly, motionless/downward-oriented arms were recorded (31 %, Fig. A26c). BGD – < 0.5 mLDOL−1: brittle stars gradually became motionless, clinging moribund to 10, 14333–14438, 2013 bioherm or lying on sediment; occasional arm movement. Fourteen individuals −1 5 died at near anoxia (average DO 0.1 mLL ), with most individuals first turning Anoxia and over. macrofauna behaviour – Anoxia: two individuals predated by sea anemones (Cereus pedunculatus), the remaining 12 died within the first 21.2 h after anoxia onset and before significant B. Riedel et al. H2S development (> 14 µM, Vaquer-Sunyer and Duarte, 2010). No fragmentation 10 visible (see Sect. 3.3.2 for more details on predation of other O. quinquemaculata by sea anemones). Title Page

Ophiura spp., N = 3 Abstract Introduction

Brittle stars shallowly buried in sediment. Conclusions References

Tables Figures – Normoxia: not visible. −1 15 – < 2.0 mLDOL : one individual emerged after 4.1 h of hypoxia (Fig. A30a); loco- J I motion on sediment 47 % (Fig. A30b). J I – < 1.0 mLDOL−1: locomotion of this specimen dropped to 19 %; motionless spec- imen then touched and ingested by C. parasitica (13 h after hypoxia onset, see Back Close Sect. 3.3.2). Full Screen / Esc −1 20 – < 0.5 mLDOL : emergence of second Ophiura individual (after 26 h of hypoxia), locomotion 50 %. Printer-friendly Version

Interactive Discussion – Anoxia: third individual emerged after 10 h of anoxia (H2S 4 µM). Both specimens then gradually became motionless, i.e. drop in locomotion to 14 %. Occasional

14366 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion arm movement visible before death (anoxia duration: 11 and 18.2 h, H2S: 5.1 and 10.3 µM, respectively). BGD

Amphiura chiajei (Forbes, 1843), N = 10 10, 14333–14438, 2013

Disc and arms of this infaunal brittle star positioned in mucus-maintained burrows, only Anoxia and 5 distal ends of arms exposed. macrofauna – Normoxia: not visible. behaviour – < 2.0 mLDOL−1: not visible. B. Riedel et al. – < 1.0 mLDOL−1: arms of one individual visibly extended above the sediment sur- face (Fig. A31a). Title Page −1 10 – < 0.5 mLDOL : four individuals fully emerged, horizontal locomotion increased Abstract Introduction to 16 % (Fig. A31b). One specimen disappeared from view at DO 0.1 mLL−1 and may have re-buried itself. Conclusions References – Anoxia: six more individuals emerged (peaked emergence, 37 %), horizontal lo- Tables Figures comotion increased to 27 %. After ca. 9 h of anoxia, 2 specimens disappeared 15 from view (mortality/survival not determined); the remaining 7 individuals died by J I 19.1 h after onset of anoxia (max. H S 21 µM). 2 J I

3.2.7 Ascidiacea Back Close

Microcosmus spp., N = 10 Full Screen / Esc

Solitary ascidian, often major component of bioherms. Designating genus in this com- Printer-friendly Version 20 munity. Interactive Discussion – Normoxia: oral siphons mostly open (68 %, Fig. A32a).

14367 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion – < 2.0 mLDOL−1: siphons remained open (65 %), but number of half-open siphon increased (20 to 28 %, Fig. A32b). Siphon extension (until end of the respective BGD deployments). Significant increase in body contraction to 15 % (Fig. A32d). 10, 14333–14438, 2013 – < 1.0 mLDOL−1: the number of closed siphons dropped to 7 % (Fig. A32c), body 5 contraction unchanged. Anoxia and −1 macrofauna – < 0.5 mLDOL : no major change in siphon habitus, body contraction peaked at behaviour 21 %. One individual started to droop (Fig. A32e). – Anoxia: number of open siphons significantly dropped and both half-open and B. Riedel et al. closed siphon habitus increased to a combined 58 %. Contraction dropped to 10 10 % after anoxia, ceasing when the individuals became moribund; drooping (in- Title Page terpreted as mortality) increased to 6 %, i.e. two out of 10 individuals died (both specimens at 76.8 h after anoxia, H2S 109.9 and 155.3 µM, respectively), 8 spec- Abstract Introduction imens survived (max. anoxia duration 78.3 h; max. final H2S 124.5 µM). Conclusions References Phallusia mammilata (Cuvier, 1815), N = 9 Tables Figures

15 Solitary ascidian, often substrate for brittle stars and crustaceans. J I – Normoxia: oral siphons predominantly open (86 %, Fig. A33a). J I – < 2.0 mLDOL−1: slight increase in number of half-open and closed siphons (Fig. A33b and c); body contraction increase to 15 % (Fig. A33d). Back Close – < 1.0 mLDOL−1: siphon closure dropped to almost zero, contractions peaked at Full Screen / Esc 20 21 %. Printer-friendly Version – < 0.5 mLDOL−1: open siphon habitus prevailed; contraction remained at 20 %. Interactive Discussion – Anoxia: marked change in siphon habitus: open siphons dropped to 61 % while closed siphons increased to 36 %. Body contractions decreased. Drooping 14368 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion (Fig. A33e) occurred in three individuals (= mortality) between 20.3 and 38.7 h of anoxia (H2S range: 86.6 to 250.7 µM); six individuals survived (max. anoxia BGD duration 24.2 h; max. final H S 19.3 µM). 2 10, 14333–14438, 2013 3.3 Intra- and interspecific interactions Anoxia and 5 Numerous interactions and resulting behavioural reactions were recorded during nor- macrofauna moxic conditions. The tube worm Protula tubularia, for example, retracted its tentacle behaviour crown after a hermit crab touched the tube; brittle stars interrupted their filter-feeding posture and changed position on bioherms when touched by passing hermit crabs (and B. Riedel et al. occasionally by the crabs’ symbiotic sea anemone C. parasitica), while the anemone 10 Cereus pedunculatus retracted into the sediment when approached by other organ- isms. Title Page With decreasing oxygen concentrations, however, “normal” behavioural interactions Abstract Introduction weakened or ceased and atypical interactions and reactions, never observed under normoxia, were documented. Most obvious was the change in decapod defensive and Conclusions References 15 territorial behaviour. Atypical predator–prey interactions involving sea anemones and brittle stars also occurred. Tables Figures

3.3.1 Aggregation and aggressive behaviour J I

Because of the hypoxia-related upward migration of the redox layer towards the sed- J I

iment surface and the often very steep oxygen gradients near the sediment surface, Back Close 20 moving only a few centimetres can mean the difference between tolerable and lethal conditions. Thus, most mobile in- and epifaunal organisms sought refuge from increas- Full Screen / Esc ingly severe bottom hypoxia by moving onto elevated, better-oxygenated substrates above the sediment surface. Macroinfauna typically emerged onto the sediment sur- Printer-friendly Version face (e.g. the sea urchin Schizaster canaliferus, the bivalve Corbula gibba), with many Interactive Discussion 25 polychaetes further moving to elevated positions on the multi-species clumps. Many epifaunal species climbed on adjoining multi-species clumps (e.g. hermit crabs) or 14369 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion higher up on the substrate they inhabited (e.g. see Fig. 4b). Cryptic epifauna, i.e. the bioherm-associated crabs Pilumnus spinifer or Pisidia longimana emerged from BGD hiding and aggregated on top of sponges and ascidians. Other mobile benthic inverte- 10, 14333–14438, 2013 brates positioned themselves on atypical substrates, for example on mobile organisms 5 avoided under normal oxygen conditions (e.g. the brittle star Ophiothrix quinquemacu- lata on hermit crabs, the hermit crab Paguristes eremita on sea urchins). The greatest Anoxia and number of aggregations as well as the greatest number of involved individuals was macrofauna recorded during severe hypoxia (19 % of observations, Fig. 4a). behaviour The search for better oxygen conditions led to atypical aggregations atop the highest B. Riedel et al. 10 substrates. This reduced the safety distance between species and outweighed normal inter- and interspecific aggression. The predatory crab P. spinifer, for example, is soli- tary and highly territorial. The absence of brittle stars on a multi-species clump typically Title Page indicates a resident crab (Wurzian, 1977). During normoxia, all encounters of two P. spinifer or of P. spinifer with other crabs (i.e. Macropodia spp.) ended with the dominant Abstract Introduction 15 individual chasing the subordinate one away. This behaviour ceased at severe hypoxia: Pilumnus specimens were observed close to each other and with heterospecifics with- Conclusions References

out showing any signs of aggressiveness. Tables Figures 3.3.2 Predator-prey interactions J I With ongoing hypoxic stress, common anti-predator strategies such as hiding in multi- J I 20 species clumps, camouflage, or flight response, ceased. The shrimp Alpheus glaber, for example, is a common prey item for both fish and other decapod crustaceans Back Close (Rufino et al., 2006). At severe hypoxia, one Alpheus specimen was closely watched by Full Screen / Esc the fish Gobius niger for 1 h from less than 5 cm distance. Were it not for the chamber’s plexiglass wall, the fish would no doubt have consumed the shrimp, which was clearly Printer-friendly Version 25 unable to flee. After leaving the burrow, the shrimps also had several encounters with an already motionless P. eremita: for up to 12 min both decapods remained side by Interactive Discussion side, the body of Alpheus touching the claws of Paguristes. Similarly, the brittle star O. quinquemaculata or the porcellanid crab P. longimana no longer showed flight reac- 14370 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion tions but aggregated atop bioherms together with potential predators: neither P.spinifer nor E. tuberosa, for example, attacked the brittle stars. In these cases, the search for BGD more oxygenated substrates by both predator and prey species – with similar hypoxia 10, 14333–14438, 2013 tolerance – apparently impeded potential predation events. In the case of dissimilar tol- 5 erances, more tolerant species benefited by taking advantage of prey that were more vulnerable. Anoxia and Overall, 8 predatory interactions (plus one predatory attack) were observed during macrofauna the 11 deployments. These involved two sea anemone species, Cereus pedunculatus behaviour and Calliactis parasitica, and, on prey side, 6 epifaunal brittle stars Ophiothrix quin- B. Riedel et al. 10 quemaculata, 1 infaunal brittle star Ophiura spp., and 1 decorator crab Ethusa mas- carone. Riedel et al. (2008a) describes five predatory interactions (O. quinquemac- ulata) in detail. The other feeding events recorded later in the study support those Title Page previous findings. All predatory interactions occurred within a relatively narrow oxygen concentration Abstract Introduction 15 window, at the transition from severe hypoxia to anoxia (H2S concentration maximum 3.5 µM). At this time, the anemones showed a burst in activity, i.e. extension and body Conclusions References

rotation in all directions. In contrast, the predated organisms were already in a mori- Tables Figures bund state and/or no longer showed flight reactions. O. quinquemaculata, for example, generally maintained a safety distance of at least 1 to 2 cm from nearby anemones J I 20 under normal oxygen concentrations. If contact was made, the brittle stars immediately retracted their arms and quickly moved a few centimetres away. At the time of pre- J I dation, however, most brittle stars (O. quinquemaculata, Ophiura spp.) were already Back Close moribund, either clinging to bioherms or lying on the sediment. Here, the feeding inter- action involved three phases: feeding (contact, pulling in of organism, transfer to mouth Full Screen / Esc 25 and ingestion), digestion, and regurgitation of brittle star remains (the latter observed 3 times; Fig. 5a–e). The feeding process lasted 1.7 to 7.7 h; regurgitation (digestion 2.1 Printer-friendly Version to 12.6 h) took maximally 60 min. Finally, one highly extended and rotating C. pedun- Interactive Discussion culatus made contact with an emerged Ophiura 1.7 h after onset of anoxia (no H2S). The brittle star was attached to the anemone’s tentacle crown for 36 min before it fell

14371 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion on the sediment with all arms fragmented. It moved on the surface a few centimetres by “rolling” from the the aboral to the oral side; 4.1 h after the predatory attack, only BGD weak arm movement was recognizable. The animal died 4.6 h later (H S 2.8 µM). 2 10, 14333–14438, 2013 Another example for reduced responsiveness to predation risk is 5 (Fig. 5f and g). The crab, which shortly before discarded its protective camouflage, moved directly towards the widely opened tentacle crown of C. parasitica and was Anoxia and −1 eaten (0.4 mLDOL , no H2S). 8.3 h later, the anemone regurgitated part of the crab; macrofauna another 4.2 h later the remaining exoskeleton followed (anoxia duration 2.6 h, H2S behaviour 0.6 µM). B. Riedel et al.

10 3.4 Sensitivity and tolerance

While hypoxia primarily affected behaviour and the abundance of individual species, Title Page anoxia significantly reduced the number of species. The overall number of individ- Abstract Introduction uals dropped from initially 495 at normoxia to 362 under hypoxia and ultimately to 196, amounting to a 61 % decrease in individual abundance. The corresponding de- Conclusions References 15 crease on the species level was from 40 to 38 at hypoxia (loss of the two decapod species Eurynome aspera: 1 individual at DO 0.2 mLL−1; Galathea sp.: 2 individuals Tables Figures at DO 0.3 and 0.03 mLL−1; data not shown) to 24 at anoxia (overall decrease 40 %). First mortalities started at severe hypoxia: the most sensitive species was the bivalve J I Chlamys varia (2 individuals at DO 0.8 and 0.2 mLL−1). Mortality then increased rapidly −1 J I 20 at < 0.3 mLDOL and centred at the transition from severe hypoxia to early anoxia (Fig. 6). The species that began to die under hypoxia were predominantly decapods Back Close (Ethusa mascarone, Macropodia spp., Alpheus glaber, Pisidia longimana, Pilumnus Full Screen / Esc spinifer) and specimens of the two echinoid species Psammechinus microtuberculatus and Schizaster canaliferus and the brittle star Ophiothrix quinquemaculata. S. canal- Printer-friendly Version 25 iferus was the first infaunal species to emerge and die (6 out of 17 individuals during −1 hypoxia, median DO 0.09 mLL ; 11 ind. during anoxia, see below). Peak mortality Interactive Discussion (94 individuals) was reached within 10 h of anoxia (e.g. polychaetes, mortalities rang- ing from 7.3 to 13.2 h duration of anoxia) and markedly dropped until 40 h of anoxia. 14372 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion More tolerant species (i.e. mortalities centred after 40 h of anoxia) included Paguristes eremita (median duration of anoxia 42.8 h; median H2S 135 µM), Hexaplex trunculus (2 BGD individuals dying at anoxia h 46.3 and 51.5, H S 117.1 and 199.9 µM), Calliactis para- 2 10, 14333–14438, 2013 sitica (median duration anoxia 52.5 h, median H2S 63 µM) and Microcosmus sulcatus 5 (2 individuals, both dying at 76.8 h of anoxia, H2S 109.9 and 155.3 µM, respectively). The results show a differentiated sequence and range of mortality at the higher taxon Anoxia and level (Fig. 6). Among the most tolerant, i.e. those dying during anoxia only, were mol- macrofauna luscs, anthozoans, and ascidians, with certain individuals surviving up to 80 h of anoxia behaviour and a maximum H2S concentration of about 279 µM. In contrast, survival rates were B. Riedel et al. 10 lowest in polychaetes, decapods and echinoderms. Importantly, all individuals that died during hypoxia, and most of those that died during anoxia, did so before significant hydrogen sulphide development. Thus, the average H2S concentration across all 11 Title Page deployments within the first 10 h of anoxia was low, i.e. 9.3 µM. Accordingly, 229 of the 299 mortalities (77 %) occurred before significant sulphide development. In general, Abstract Introduction 15 species with the highest tolerance to anoxia also tolerated high sulphide values. Overall, 196 individuals representing 24 species (8 higher taxa: Mollusca, Antho- Conclusions References

zoa, Ascidiacea, Polychaeta, Decapoda, Echinodermata, Scaphopoda) survived. In 13 Tables Figures species, of which 9 are molluscs, all individuals survived. These included: the pea crab Nepinnotheres pinnotheres, the sea anemone Cereus pedunculatus, the scaphopod J I 20 Dentalium sp., the bivalves Corbula gibba, Nucula nucleus, Fusinus rostratus, Parvi- cardium papillosum, Timoclea ovata, Tellina serrata, as well as the gastropods Ap- J I porhais pes-pelecani, Murex brandaris and Nassarius cf. pygmaeus. Note, however, Back Close that based on individuals, 77 % of the survivors were represented by only 2 species: the infaunal bivalve Corbula gibba (66 individuals) and the sea anemone Cereus pe- Full Screen / Esc 25 dunculatus (28 individuals). Among the distinguished life habit categories (substrate relationship, mobility, feed- Printer-friendly Version ing type), epifaunal, mobile and predator species were generally more sensitive and affected earlier (i.e. around DO < 0.2 mLL−1) than their infaunal, sessile, deposit and Interactive Discussion suspension-feeding conspecifics. The overall epifauna decrease was 42 % (data not

14373 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion shown), with the cryptic fauna (i.e. the decapods E. mascarone, Galathea sp., Pisidia longinmana) being particularly sensitive to decreasing oxygen (overall decrease 60 %). BGD In contrast, in infauna the overall decrease was 36 %, with a major drop after ∼ 10 h of 10, 14333–14438, 2013 anoxia (e.g. S. canaliferus, indet. polychaeta, Glycera sp., Amphiura chiajei, Ophiura 5 spp., Venerupis cf. rhomboides, Abra alba). The overall decline in mobile life-forms was twice as high (43 %) as in sessile forms during late anoxia (20 %), i.e. > 40 h (mortality Anoxia and of 2 M. sulcatus, 4 C. parasitica, 1 Ocnus planci, 2 Protula tubularia). Finally, among the macrofauna 3 major feeding types, predators (among those particularly decapods, see above) were behaviour generally most vulnerable (overall decrease 53 %), followed by more tolerant deposit- B. Riedel et al. 10 and suspension-feeding species. In the latter two, overall reduction accounted for 36 and 33 % (starting after ∼ 10 and 20 h of anoxia), with loss in echinoderm species mainly responsible for the drop (deposit feeders: A. chiajei, Ophiura spp., P. microtu- Title Page berculatus, S. canaliferus; suspension feeders: O. planci, O. quinquemaculata). Abstract Introduction

4 Discussion Conclusions References

15 The responses to hypoxia/anoxia act at various levels, and in concert, calling for a holis- Tables Figures tic, ecological approach to better understand and respond to this phenomenon. The present study emphasizes two key conceptual points: benthic macrofauna behaviour J I as a visible, integrated tool to monitor the full range of critical oxygen thresholds in the field, and the strong potential of field studies to quantify population- and community- J I 20 level endpoints. Combined, they provide a realistic basis for assessing and predicting Back Close impacts on ecological integrity. The macrobenthos in the North Adriatic Sea reacted rapidly and successively across Full Screen / Esc the entire range of declining oxygen conditions. Overall, the 11 deployments revealed a consistent and predictable pattern of reactions and phases, both within and among Printer-friendly Version 25 species (Fig. 7). Moreover, the results go beyond individual behaviours to document Interactive Discussion sequences of reactions and interactions of representative soft-bottom species. Beyond supporting and refining the reactions to hypoxia/anoxia observed elsewhere, we also 14374 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion report on species whose sensitivities/tolerances are poorly described (i.e. pea crabs: Stauber, 1945) or that have rarely if ever been continuously observed in situ (e.g. the BGD infaunal shrimp Alpheus glaber, P. Dworschak, personal communication, 2013). Most 10, 14333–14438, 2013 behavioural changes and mortalities were attributable solely to oxygen depletion: H2S 5 had not yet developed or was present in negligible concentrations. Anoxia and 4.1 Faunal responses: the individual- to community-level macrofauna behaviour 4.1.1 Macrofauna behaviour B. Riedel et al. The initial reactions of the infauna and epifauna differed considerably compared to behaviour under normoxia, beginning with emergence/exposure and flight/avoidance −1 10 at oxygen values below 2 mLL . This clearly identifies this oxygen concentration as Title Page a critical key threshold for Northern Adriatic communities (Fig. 7). This corresponds to values reviewed in Diaz and Rosenberg (1995) and Wu (2002). It is also in line Abstract Introduction

with Vaquer-Sunyer and Duarte (2008) or Gray et al. (2002), who considered the 2 mg Conclusions References DOL−1 threshold (equivalent to 1.4 mLDOL−1 or 63 µM; e.g. Rabalais et al., 2001) as 15 being potentially too low because certain organisms begin to react beforehand. In this Tables Figures study, the onset of hypoxia triggered reactions in almost half of the species and higher taxa analysed (exceptions: nematodes, sipunculids and polychaetes). This included J I representatives of both the epi- and the infauna i.e. the anemone Cereus peduncu- latus began to extend from the sediment, the buried crab Ebalia tuberosa emerged J I 20 from hiding in the sediment and the bivalve Corbula gibba appeared on the sediment Back Close surface. Also, all three major feeding types were affected: the suspension-feeding brit- tle star Ophiothrix quinquemaculata began arm tipping, the deposit-feeding sea urchin Full Screen / Esc Psammechinus microtuberculatus discarded its camouflage, and the predatory crab Pilumnus spinifer emerged from hiding places and climbed atop bioherms. These visi- Printer-friendly Version 25 ble signs of stress render “internal” physiological adaptions (Hagerman, 1998) into “ex- Interactive Discussion ternal” behavioural reactions. After exposure or emergence, the avoidance strategies aimed at increasing oxygen supply involved, initial peaks in locomotion and movement 14375 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion to higher, more oxygenated areas. This is because oxygen concentrations increase logarithmically with height above the bottom (Jørgensen, 1980; Diaz and Rosenberg, BGD 1995). Accordingly, the infauna typically emerges onto the sediment surface (Nilsson 10, 14333–14438, 2013 and Rosenberg, 1994; Pihl et al., 1992; Hrs-Brenko et al., 1994), the epifauna climbs 5 onto elevated substrates, and sessile species attempt to stretch upward (e.g. Baden et al., 1990; Rosenberg et al., 1991). On the flat sublittoral soft-bottoms of the Northern Anoxia and Adriatic Sea, hypoxia can affect several hundred to thousands of km2 (Stachowitsch, macrofauna 1984). Less mobile benthic invertebrates cannot escape horizontally, potentially ex- behaviour plaining the relatively short phase of increased activity. Multi-species clumps represent B. Riedel et al. 10 the sole refuge from short-term bottom-hypoxia. A few centimetres above the sediment surface can mean the difference between tolerable and lethal conditions. Thus, the as- cidian Microcosmus sulcatus extended its siphons, paralleling observations on Molgula Title Page manhattensis by Sagasti et al. (2001). The anemone Cereus pedunculatus combined body elongation, upward tentacle extension, body rotation, swaying and contraction, Abstract Introduction 15 probably to increase exposure to sea water both through the body wall and coelon- teron, maximize the surface area to volume ratio, minimize the diffusion distance within Conclusions References

the tissues (Sassaman and Mangum, 1972; Shick, 1991), and helping transport oxy- Tables Figures gen back to tissues attached to the bottom (Sagasti et al., 2001). Similar behaviours were observed for Calliactis parasitica (present study), for Cerianthus sp. in the Gulf of J I 20 Mexico (Rabalais et al., 2001), as well as for Diadumine leucolena (Sagasti et al., 2001) and Metridium senile (Wahl, 1984) in laboratory studies. The latter two also released J I their pedal disc from the substrate (D. leucolena: < 1 mgDOL−1; M. senile: anoxia). Back Close In our study, two C. parasitica individuals also detached from the hermit-crab shell at anoxia. In an earlier mortality event in the Northern Adriatic, numerous anemones – in- Full Screen / Esc 25 cluding Cerianthus sp. – were observed on the sediment surface with exposed pedal discs (e.g. Fig. 16 in Stachowitsch, 1984). Printer-friendly Version We interpret several subsequent behaviours as strategies to decrease oxygen de- mand once emergence, increased locomotion or climbing upwards fail. While covering Interactive Discussion the body with shells, stones or algae provides antipredator benefits or protection from

14376 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion desiccation and UV-radiation (e.g. Dumont et al., 2007; Hultgren et al., 2008), estab- lishing and maintaining this camouflage can also be costly (Berke and Woodin, 2008). BGD Thus, discarding of camouflage by sea urchins and crabs (P. microtuberculatus and 10, 14333–14438, 2013 Ethusa mascarone) may represent a cost-benefit trade-off in favour of losing “addi- 5 tional ballast” during ongoing environmental stress (Dumont et al., 2007). Similarly, the hermit crab Paguristes eremita emerged from their shells and moved about fully ex- Anoxia and posed. This was first observed here by Stachowitsch (1984) and is outlined in greater macrofauna detail in Pretterebner et al. (2012). Such behaviour also occurs under thermal stress behaviour and desiccation (Taylor, 1981; Bertness, 1982), when the crabs are pursued (Green- B. Riedel et al. 10 away, 2003) or after sedimentation (Shives and Dunbar, 2010). The responses of macrofauna in one system can support interpretations of benthic health elsewhere, even across large geographical and bathymetric ranges. Thus, lab- Title Page oratory and field observations underline the similarity of key macrofauna responses. A case in point is arm-tipping in ophiuroids, whereby the disc and respiratory struc- Abstract Introduction 15 tures are raised above the sediment surface. The same posture has been observed for Amphiura chiajei, A. filiformis, and Ophiura albida in the Kattegat (Baden et al., Conclusions References

1990; Rosenberg et al., 1991; Vistisen and Vismann, 1997), Ophiura texturata in the Tables Figures (Dethlefsen and von Westernhagen, 1983), Ophiothrix quinquemaculata in the Northern Adriatic (Stachowitsch, 1984, and the present study), Ophiura sp. in the J I 20 Lower St. Lawrence Estuary, Canada (Belley et al., 2010), and brittle stars in the Gulf of Mexico (Rabalais et al., 2001). This would be a new and intriguing extension of the J I early concept of “parallel level-bottom communities” (Thorson, 1957). Thus, the tiered Back Close behavioural shifts we have documented can help draw conclusions about future oxygen conditions and community status – early-, mid-, late-term perturbation and successive Full Screen / Esc 25 community/ecosystem degradation – both in the Northern Adriatic and elsewhere. Printer-friendly Version 4.1.2 Intra- and interspecific interactions Interactive Discussion Community-level changes emerge from processes operating at the individual level that trigger cascading direct and indirect effects (O’Gorman et al., 2011). Weakened or al- 14377 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion tered functionally important biological interactions, such as predator–prey dynamics, can derail community dynamics long before extensive mortalities occur (Brante and BGD Hughes, 2001; Tallqvist, 2001; Seitz et al., 2003). Hypoxia-induced change – shifts in 10, 14333–14438, 2013 spatial distribution on the sediment or atop elevated substrates, abandoned defensive 5 strategies such as decoration – adversely affect survival by increasing the vulnerability to predation. Thus, extended siphons or palps of bivalves and polychaetes above the Anoxia and sediment surface can be bitten off by predators (Sandberg et al., 1996). The relative macrofauna tolerance of predator and prey governs predation efficiency (Breitburg et al., 1994). behaviour Nesterlode and Diaz (1998) hypothesized that relative tolerance may lead to selec- B. Riedel et al. 10 tive predation, whereby the most sensitive prey will be exploited (Sandberg, 1994). In our experiments, the more hypoxia-tolerant sea anemones consumed moribund brittle stars (Ophiothrix quinquemaculata) and stressed decorator crabs Ethusa mascarone. Title Page We attribute this to the predators’ increased activity and radius of activity (elongation and rotation in all directions), to the prey’s reduced flight reaction, and to the chemical Abstract Introduction 15 stimuli released by moribund, damaged and/or dead individuals that initiate a forag- ing response in most cnidarians (Elliott and Cook, 1989; McFarlane and Lawn, 1991). Conclusions References

Chintiroglou and Koukouras (1991, 1992), who studied the diet of Calliactis parasit- Tables Figures ica and Cereus pedunculatus, never identified brittle stars (or other echinoderms) as prey items, perhaps due to high handling and assimilation time and low energy con- J I 20 tent (Thayer et al., 1973). Nonetheless, the time slot for such alternate predation is relatively narrow – at the transition from severe hypoxia to anoxia. Munari and Mistri J I (2011) studied the effect of short-term hypoxia on predation by the muricid gastropod Back Close Rapana venosa (hypoxia-tolerant) on three bivalve species with different tolerances: prey species were switched during hypoxia from the tolerant Scapharca inaequivalvis Full Screen / Esc 25 to the less tolerant and therefore more easily-to-catch (decreased burial depth and siphon extension) Tapes philippinarum. Printer-friendly Version Mutual interference and agonistic behaviour or cooperative foraging between preda- tor species during perturbation can also alter consumption rates and prey density (Tay- Interactive Discussion lor and Eggleston, 2000). The present study revealed a new facet: the aggregation

14378 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion of potential predator-prey partners atop multi-species clumps clearly negated safety distances within and between species. Thus, oxygen deficiency outweighed normal BGD intra- and interspecific aggression: the territory crab Pilumnus spinifer aggregated with 10, 14333–14438, 2013 con-/heterospecifics (see also Haselmair et al., 2010) and did not react to its normal 5 prey (juvenile brittle stars or smaller crabs; Wurzian, 1977). We attribute this largely to the relatively similar hypoxia-tolerance of crustaceans and echinoderms (i.e. Sunyer- Anoxia and Vaquer and Duarte, 2008), represented here by P. spinifer and O. quinquemaculata macrofauna (see also Riedel et al., 2012). The fact that crustaceans compensate for short-term behaviour hypoxia by increasing ventilation at the expense of other energetically demanding ac- B. Riedel et al. 10 tivities such as locomotion and feeding (Taylor et al., 1977) may also play a role. Thus, by changing behaviour, hypoxia can alter trophic pathways and derail community dy- namics. Title Page

4.1.3 Sensitivity and tolerance Abstract Introduction

Beyond disrupting life cycles, altering behaviour and changing biological interactions, Conclusions References 15 hypoxia significantly reduces abundance, biomass and diversity (e.g. Diaz and Rosen- berg, 1995; Levin et al., 2009). Generally, fish are considered to be the most hypoxia- Tables Figures sensitive group, followed by crustaceans, polychaetes, echinoderms, sea anemones, molluscs, hydro-/scyphozoans and ascidians (Gray et al., 2002; Vaquer-Sunyer and J I Duarte, 2008). Our results broadly confirmed this pattern, with ascidians, anthozoans J I 20 and molluscs being distinctly more tolerant than polychaetes, decapods, and echin- oderms. Our in situ approach, however, provided a more nuanced picture by high- Back Close lighting the complex intra- and interspecific variability in sensitivity, for example im- Full Screen / Esc mediate behavioural reactions vs. survival/mortality. The generally more tolerant mol- luscs (metabolic depression and energy utilization; Larade and Storey, 2002) repre- Printer-friendly Version 25 sented 13 of the 24 species with surviving individuals (see also Riedel et al., 2012). Nonetheless, some molluscs reacted immediately (e.g. the infaunal bivalve Corbula Interactive Discussion gibba emerging from the sediment at the onset of hypoxia), others died early (Chlamys varia and Diodora sp. at moderate and severe hypoxia), whereas others showed high 14379 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion survival rates (Hexaplex trunculus). Some species showed broader intraspecific tol- erance. The hermit crab P. eremita tolerated between 18 and 62 h of anoxia. The in- BGD faunal sea urchin Schizaster canaliferus suffered 6 mortalities at hypoxia, starting at 10, 14333–14438, 2013 0.3 mLDOL−1, whereas 11 other individuals died within the first 24 h of anoxia. Such 5 intraspecific ranges probably reflect different weight, size or life stage (e.g. Breitburg, 1992; Shimps et al., 2005) and ability to seek refuge atop elevated substrates. In later Anoxia and mortalities, H2S development might also play a role. Such variability can provide an macrofauna evolutionary advantage by buffering the population against stochastic, extreme events behaviour (e.g. Denny et al., 2011). Finally, the data also showed that high sensitivity and high tol- B. Riedel et al. 10 erance are not necessarily mutually exclusive. Corbula gibba is a case in point: it was among the first to react to hypoxia, but by closing its valves hermetically and lowering its metabolism, it also withstood prolonged anoxia and sulphidic conditions (Hrs-Brenko, Title Page 2006 and references therein): all specimens survived our deployments. The mortality peak at the transition from severe hypoxia to anoxia suggests that Abstract Introduction 15 weak or short-term hypoxia (i.e. 1 to 2 days) primarily involves quantitative losses – in the sense of punctuated, species-specific mortalities – rather than fundamentally Conclusions References

altered overall community structure and composition. Longer-lasting or more intense Tables Figures oxygen depletion, however, depauperizes and taxonomically and functionally homog- enizes the benthic community (Sala and Knowlton, 2006). The fact that most mor- J I 20 talities took place before significant H2S development allowed a clear distinction of the roles played by hypoxia and H2S: low oxygen conditions alone are sufficient to J I cause quick and widespread community collapse in the Northern Adriatic. In a worst- Back Close case scenario, the macrofauna is eliminated entirely (Fedra et al., 1976; Stachowitsch, 1984; Hrs-Brenko et al., 1994). Note that while the bioherms markedly increase habi- Full Screen / Esc 25 tat complexity and provide refuge for mobile species, they also potentially accelerate mortalities and ecosystem collapse in a positive feedback loop (e.g. emergence and Printer-friendly Version death of associated species from decomposing bioherms). This supports the conclu- sions drawn by Metzger et al. (2013, this issue) that the input of organic material by Interactive Discussion decaying macrofauna is partially responsible for the deteriorating biogeochemical en-

14380 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion vironment. Accordingly, the death of major bioherm constituents such as sponges may also help define tipping points (Fig. 1). Such hypoxia-induced community degradation BGD has also been observed in other biogenic habitats (e.g. oyster beds, Lenihan and Peter- 10, 14333–14438, 2013 son, 1998): domino effects lead to widespread ecosystem degradation (Lenihan et al., 5 2001). Beyond extending and complementing earlier field observations (e.g. Jørgensen, Anoxia and 1980; Stachowitsch, 1984; Rabalais et al., 2001), recent reviews (e.g. Levin et al., macrofauna 2009) and meta-analyses (e.g. Vaquer-Sunyer and Duarte, 2008), the detailed sensitiv- behaviour ities and tolerances can provide insight into post-disturbance community compositions. B. Riedel et al. 10 Thus, coupled with additional information (e.g. on growth rates and immigration), the data can help interpret and reconstruct the severity and timing of past oxygen depletion events based on the composition and sizes of remaining species. Title Page

4.2 Biodiversity and ecosystem functioning: the ecological perspective Abstract Introduction

Diversity loss due to oxygen depletion is determined by multiple factors ranging from Conclusions References 15 sensitivity to low DO to the presence of additional stressors (e.g. Vaquer-Sunyer and Duarte, 2010, 2011). The multiple interactions and feedbacks, hidden drivers and emer- Tables Figures gent properties complicate predicting the consequences of species loss for ecosystem function. One assumption has been that high diversity maintains a high complexity of J I interactions and feedbacks among species, supporting stability and resistance to dis- J I 20 turbance (Cardinale et al., 2012). In the case of bioherms and anoxia, however, multi- tiered complexity may actually accelerate community collapse (see above). Moreover, Back Close most key ecosystem processes are performed by particular species (Solan et al., 2004; Full Screen / Esc Hector and Bagchi, 2007). Even rare species can perform key functions and increase the level of functional diversity (Mouillot et al. (2013), sustaining ecosystem processes, Printer-friendly Version 25 Tilman et al., 1997; Mouillot et al., 2011). Clearly, ecosystem performance depends on both the quantity and quality of biodiversity (Thrush et al., 2006). Interactive Discussion Oxygen depletion triggered a significant drop in both individuals (“quantitative” im- pact on function, see below) and species (“qualititative” impact). The unique functional 14381 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion roles of some species (Ellison et al., 2005) become evident when examining major life habit categories (substrate relationship, mobility and feeding type). In the North- BGD ern Adriatic, suspension feeding can be used in a process-orientated interpretation 10, 14333–14438, 2013 of ecosystem status. Particular species typically filter a certain range of sizes 5 (e.g. Ward and Shumway, 2004). When some individuals of that species are missing, other individuals continue to feed on that particle size (quantitative loss of function). Anoxia and When, however, the species itself is lost, then that particle size range may no longer be macrofauna filtered (qualitative loss). The relatively early loss of hypoxia-sensitive sponges and brit- behaviour tle stars (O. quinquemaculata), but survival of the more tolerant ascidian Microcosmus B. Riedel et al. 10 sulcatus, all filtering distinct particle sizes (Gili and Coma, 1998), probably represents a qualitative shift in filter-feeding capacity. Moreover, the loss of two key suspension feeding components at the hypoxia/anoxia transition may markedly compromise the Title Page overall regulatory role of the filter-feeding compartment (natural eutrophication control; Officer et al., 1982). Loss of the stabilizing role of the ORM community – the benthos Abstract Introduction 15 converts pelagic into benthic biomass and serves as a storage compartment (Ott and Fedra, 1977) – no doubt significantly impacts long-term and large-scale ecosystem Conclusions References

functioning. Tables Figures Importantly the impact on ecosystem integrity begins much earlier, long before such functionally important components are missing entirely (e.g. Thrush and Dayton, 2002). J I 20 Here, behaviour is a sentinel. From the suspension-feeding perspective, the change from O. quinquemaculata’s the feeding posture to arm-tipping at mild hypoxia affects J I benthic-pelagic coupling (Graf, 1992) long before the animals die. From the Back Close perspective, the upward movement (i.e. sediment bulging, Fig. 3) and emergence of the infaunal sea urchin Schizaster canaliferus means that particle reworking and burrow Full Screen / Esc 25 ventilation (Schinner et al., 1993; Kristensen et al., 2012) cease long before mortality. In the Northern Adriatic, the complex bioherms create distinct “biodiversity hotspots” Printer-friendly Version that provide substrate for larval settlement and epigrowth, shelter and food on the struc- turally less complex soft-bottom surfaces. The rapid mortality of their long-lived and Interactive Discussion slow-growing component species, such as larger sponges, stands in stark contrast to

14382 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion the slow recovery. The anoxic event in September 1983, for example, destroyed 50 % of the epifaunal biomass in only two days, and over 90 % within four days (Stachowitsch, BGD 1984). The subsequent recolonization process was very slow, with both total biomass 10, 14333–14438, 2013 and the relative contribution of key species (O. quinquemaculata, Microcosmus spp., 5 the sponge Reniera sp.) remaining distinctly below previously recorded values for years (Stachowitsch, 1991). Additionally, benthic recovery was (and presently continues to Anoxia and be) further impaired by harmful fishing activities and renewed oxygen depletions (e.g. macrofauna Stachowitsch and Fuchs, 1995; Kollmann and Stachowitsch, 2001). The overall result behaviour is marked longer-term community degradation and decreased habitat complexity, of- B. Riedel et al. 10 fering new niches for opportunistic colonizers and non-indigenous species (e.g. Jewett et al., 2005; Dumont et al., 2011).

Title Page 5 Conclusions Abstract Introduction

Coastal oxygen depletion raises many questions, among them how these events can Conclusions References be detected early, how their spatial extents, durations and frequencies can be moni- 15 tored, and how the effects ameliorated. This requires knowing the state of the benthic Tables Figures community and the ecological impacts at multiple, organism to ecosystem levels. As an integrative parameter, behavioural reactions and mortality help define criti- J I cal oxygen thresholds and determine the immediate ecological status. The knowledge about sensitive (“losers”; Roberts and Brink, 2010) and more tolerant species (surviv- J I 20 ing post-disturbance “winners”) can help to pinpoint and define the spatial extension Back Close of past mortalities. Finally, the roles individual species play, help better gauge poten- tial effects on ecosystem integrity, function and resilience. Our integrated approach is Full Screen / Esc applicable across communities, habitats and biogeographical zones, and could also provide input into paleoecological interpretations. It also provides a useful tool to trans- Printer-friendly Version 25 port complex ecological processes to the public and decision-makers to define specific Interactive Discussion monitoring, assessment and conservation plans.

14383 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion Acknowledgements. The authors thank R. Machan (electronics), V. Perlinger (workshop), G. Eder (photography) and S. Maringer (chemistry), as well as P.Steiner and I. Gallmetzer (diving) BGD for their support and many years of excellent cooperation. We are also grateful to the directors (V. Malacic, A. Malej) and staff (T. Makovec, J. Forte, G. Polajnar) at the Marine Biology Station 10, 14333–14438, 2013 5 (MBS) Piran, Slovenia, for their hospitality and support during the fieldwork. This study was financed by the Austrian Science Fund (FWF; projects P17655-B03 and P21542-B17) and supported by the OEAD Bilateral Slovenian Austrian Scientific Technical Cooperation project Anoxia and SI 22/2009. macrofauna behaviour

References B. Riedel et al.

10 Adams, S. M.: Establishing causality between environmental stressors and effects on aquatic ecosystems, Hum. Ecol. Risk Assess., 9, 17–35, 2003. Title Page Baden, S. P., Loo, L. O., Pihl, L., and Rosenberg, R.: Effects of eutrophication on benthic com- munities including fish: swedish west coast, Ambio, 19, 113–122, 1990. Abstract Introduction Belley, R., Archambault, P., Sundby, B., Gilbert, F., and Gagnon, J.-M.: Effects of hypoxia on 15 benthic macrofauna and bioturbation in the Estuary and Gulf of St. Lawrence, Canada, Cont. Conclusions References Shelf Res., 30, 1302–1313, 2010. Berke, S. K. and Woodin, S. A.: Energetic costs, ontogenetic shifts and sexual dimorphism in Tables Figures spider crab decoration, Funct. Ecol., 22, 1125–1133, 2008. Bertness, M. D.: Shell utilization, predation pressure, and thermal stress in Panamanian hermit J I 20 crabs: an interoceanic comparison, J. Exp. Mar. Biol. Ecol., 64, 159–187, 1982. Biro, P.A.: Do rapid assays predict repeatability in labile (behavioural) traits?, Anim. Behav., 83, J I 1295–1300, 2012. Blasnig, M., Riedel, B., Zuschin, M., Schiemer, L., and Stachowitsch, M.: Short-term post- Back Close mortality predation and scavenging and longer-term recovery after anoxia in the north- Full Screen / Esc 25 ern Adriatic Sea, Biogeosciences Discuss., 10, 4367–4401, doi:10.5194/bgd-10-4367-2013, 2013. Boyd, W. A., Brewer, S. K., and Williams, P.L.: Altered behavior of invertebrates living in polluted Printer-friendly Version environments, in: Behavioral Ecotoxicology, Ecological and Environmental Toxicology Series, Interactive Discussion editted by: Dell’Omo, G., John Wiley & Sons Ltd, Chichester, UK, 293–336, 2002.

14384 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion Brante, A. and Hughes, R. N.: Effect of hypoxia on the preyhanding behaviour of Carcinus maenas feeding on Mytilus edulis, Mar. Ecol.-Prog. Ser., 209, 301–305, 2001. BGD Breitburg, D.: Episodic hypoxia in : interacting effects of recruitment, behavior, and physical disturbance, Ecol. Monogr., 62, 525–546, 1992. 10, 14333–14438, 2013 5 Breitburg, D. L., Steinberg, N., DuBeau, S., Cooksey, C., and Houde, E. D.: Effects of low dissolved oxygen on predation on estuarine fish larvae, Mar. Ecol.-Prog. Ser., 104, 235–246, 1994. Anoxia and Cardinale, B. J., Duffy, J. E., Gonzalez, A., Hooper, D. U., Perrings, C., Venail, P., Narwani, A., macrofauna Mace, G. M., Tilman, D., Wardle, D. A., Kinzig, A. P., Daily, G. C., Loreau, M., Grace, J. B., behaviour 10 Larigauderie, A., Srivastava, D. S., and Naeem, S.: Biodiversity loss and its impact on hu- manity, Nature, 486, 59–67, 2012. B. Riedel et al. Chintiroglou, C. and Koukouras, A.: Observations on the feeding habits of Calliactis parasitica (Couch, 1842), Anthozoa, , Oceanol. Ac., 14, 389–396, 1991. Chintiroglou, C. and Koukouras, A.: The feeding habits of three Mediterranean sea anemone Title Page 15 species, Anemonia viridis (Forskal), Actinia equina (Linnaeus) and Cereus pedunculatus (Pennant), Helgoländer Meeresun., 46, 53–68, 1992. Abstract Introduction Conley, D. J., Carstensen, J., Vaquer-Sunyer, R., and Duarte, C. M.: Ecosystem thresholds with hypoxia, Hydrobiologia, 629, 21–29, 2009. Conclusions References Culp, J. M., Podemski, C. L., Cash, K. J., and Lowell, R. B.: A research strategy for using Tables Figures 20 stream microcosms in ecotoxicology: integrating experiments at different levels of biological organization with field data, J. Aquat. Ecosyst. Stress Recov., 7, 167–176, 2000. Danovaro, R., Fonda Umani, S., and Pusceddu, A.: and the potential spreading J I of marine mucilage and microbial pathogens in the Mediterranean Sea, PLoS ONE, 4, e7006, 2009. J I 25 Denny, M. W., Wesley Dowd, W., Bilir, L., and Mach, K. J.: Spreading the risk: small-scale Back Close body temperature variation among intertidal organisms and its implications for species per- sistence, J. Exp. Mar. Biol. Ecol., 400, 175–190, 2011. Full Screen / Esc Dethlefsen, V. and von Westernhagen, H.: Oxygen deficiency and effects on bottom fauna in the eastern German Bight, Meeresforschung, 30, 42–53, 1983. Printer-friendly Version 30 De Troch, M., Roelofs, M., Riedel, B., and Grego, M.: Structural and functional responses of harpacticoid copepods to anoxia in the Northern Adriatic: an experimental approach, Bio- Interactive Discussion geosciences, 10, 4259–4272, doi:10.5194/bg-10-4259-2013, 2013.

14385 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion Diaz, R. J. and Rosenberg, R.: Marine benthic hypoxia: a review of its ecological effects and the behavioural responses of benthic macrofauna, Oceanogr. Mar. Biol. Ann. Rev., 33, 245–303, BGD 1995. Diaz, R. and Rosenberg, R.: Spreading dead zones and consequences for marine ecosystems, 10, 14333–14438, 2013 5 Science, 321, 926–929, 2008. Diaz, R., Selman, M., and Chique, C.: Global eutrophic and hypoxic coastal systems, World Re- sources Institute, Eutrophication and hypoxia: in coastal waters, available Anoxia and at: http://www.wri.org/project/eutrophication, 2010. macrofauna Dumont, C. P.,Drolet, D., Deschênes, I., and Himmelman, J. H.: Multiple factors explain the cov- behaviour 10 ering behaviour in the green sea urchin, Strongylocentrotus droebachiensis, Anim. Behav., 73, 979–986, 2007. B. Riedel et al. Dumont, C. P., Gaymer, C. F., and Thiel, M.: Predation contributes to invasion resistance of benthic communities against the non-indigenous tunicate Ciona intestinalis, Biol. Invasions, 13, 2023–2034, 2011. Title Page 15 Ekau, W., Auel, H., Pörtner, H.-O., and Gilbert, D.: Impacts of hypoxia on the structure and pro- cesses in pelagic communities (zooplankton, macro-invertebrates and fish), Biogeosciences, Abstract Introduction 7, 1669–1699, doi:10.5194/bg-7-1669-2010, 2010. Elliott, J. and Cook, C. B.: Diel variation in prey capture behavior by the corallimorpharian Conclusions References Discosoma sanctithomae: mechanical and chemical activation of feeding, Biol. Bull., 176, Tables Figures 20 218–228, 1989. Ellison, A. M., Bank, M. S., Clinton, B. D., Colburn, E. A., Elliott, K., Ford, C. R., Foster, D. R., Kloeppel, B. D., Knoepp, J. D., Lovett, G. M., Mohan, J., Orwig, C. R., Rodenhouse, N. L., J I Sobczak, W. V., Stinson, K. A., Stone, J. K., Swan, C. M., Thompson, J., Von Holle, B., and Webster, J. R.: Loss of foundation species: consequences for the structure and dynamics of J I 25 forested ecosystems, Front. Ecol. Environ., 3, 479–486, 2005. Back Close Fedra, K., Ölscher, E. M., Scherübel, C., Stachowitsch, M., and Wurzian, R. S.: On the ecology of a North Adriatic benthic community: distribution, standing crop and composition of the Full Screen / Esc macrobenthos, Mar. Biol., 38, 129–145, 1976. Gili, J. M. and Coma, R.: Benthic suspension feeders: their paramount role in littoral marine Printer-friendly Version 30 food webs, Trends Ecol. Evol., 13, 316–321, 1998. Gooday, A. J., Jorissen, F., Levin, L. A., Middelburg, J. J., Naqvi, S. W. A., Rabalais, N. N., Interactive Discussion Scranton, M., and Zhang, J.: Historical records of coastal eutrophication-induced hypoxia, Biogeosciences, 6, 1707–1745, doi:10.5194/bg-6-1707-2009, 2009. 14386 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion Graf, G.: Benthic-pelagic coupling: a benthic view, Oceanogr. Mar. Biol. Ann. Rev., 30, 149– 190, 1992. BGD Gray, J. S., Wu, R. S. S., and Or, Y. Y.: Effects of hypoxia and organic enrichment on the coastal marine environment, Mar. Ecol.-Prog. Ser., 238, 249–279, 2002. 10, 14333–14438, 2013 5 Greenaway, P.: Terrestrial adaptations in the Anomura (Crustacea: Decapoda), Mem. Mus. Vic- toria, 60, 13–26, 2003. Grego, M., Stachowitsch, M., De Troch, M., and Riedel, B.: CellTracker Green labelling vs. Anoxia and rose bengal staining: CTG wins by points in distinguishing living from dead anoxia-impacted macrofauna copepods and nematodes, Biogeosciences, 10, 4565–4575, doi:10.5194/bg-10-4565-2013, behaviour 10 2013a. Grego, M., Riedel, B., Stachowitsch, M., and De Troch, M.: Meiofauna winners and losers of B. Riedel et al. coastal hypoxia: case study harpacticoid copepods, Biogeosciences Discuss., 10, 12385– 12416, doi:10.5194/bgd-10-12385-2013, 2013b. Grieshaber, M. K., Hardewig, I., Kreutzer, U., and Pörtner, H- O.: Physiological and metabolic Title Page 15 responses to hypoxia in invertebrates, Rev. Physiol. Biochem. Pharmacol., 125, 43–147, 1994. Abstract Introduction Gruber, N.: Warming up, turning sour, losing breath: ocean biogeochemistry under global change, Philos. T. Roy. Soc. A, 369, 1980–1996, 2011. Conclusions References Hagerman, L.: Physiological flexibility; a necessity for life in anoxic and sulphidic habitats, Hy- Tables Figures 20 drobiologia, 375/376, 241–254, 1998. Halpern, B. S., Walbridge, S., Selkoe, K. A., Kappel, C. V., Micheli, F., D’Agrosa, C., Bruno, J. F., Casey, K. S., Ebert, C., Fox, H. E., Fujita, R., Heinemann, D., Lenihan, H. S., Madin, E. M., J I Perry, M. T., Selig, E. R., Spalding, M., Steneck, R., and Watson, R.: A global map of human impact on marine ecosystems, Science, 319, 948–952, 2008. J I 25 Haselmair, A., Stachowitsch, M., Zuschin, M., and Riedel, B.: Behaviour and mortality of benthic Back Close crustaceans in response to experimentally induced hypoxia and anoxia in situ, Mar. Ecol.- Prog. Ser., 414, 195–208, 2010. Full Screen / Esc Hector, A. and Bagchi, R.: Biodiversity and ecosystem multifunctionality, Nature, 448, 188–190, 2007. Printer-friendly Version 30 Howarth, R., Chan, F., Conley, D. J., Garnier, J., Doney, S. C., Marino, R., Billen, G.: Cou- pled biogeochemical cycles: eutrophication and hypoxia in temperate estuaries and coastal Interactive Discussion marine ecosystems, Front. Ecol. Environ., 9, 18–26, 2011.

14387 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion Hrs-Brenko, M.: The basket shell, Corbula gibba Olivi, 1792 (Bivalve Mollusks) as a species resistant to environmental disturbances: a review, Acta Adriat., 47, 49–64, 2006. BGD Hrs-Brenko, M., Medaković, D., Labura, Ž., and Zahtila, E.: Bivalve recovery after a mass mor- tality in the autumn of 1989 in the northern Adriatic Sea, Period. Biol., 96, 455–458, 1994. 10, 14333–14438, 2013 5 Hultgren, K. M. and Stachowicz, J. J.: Alternative camouflage strategies mediate predation risk among closely related co-occuring kelp crabs, Oecologia, 55, 519–528, 2008. Jewett, E. B., Hines, A. H., and Ruiz, G. M.: Epifaunal disturbance by periodic low levels of Anoxia and dissolved oxygen: native vs. response, Mar. Ecol.-Prog. Ser., 304, 31–44, macrofauna 2005. behaviour 10 Jørgensen, B. B.: Seasonal oxygen depletion in the bottom waters of a Danish fjord and its effect on the benthic community, Oikos, 34, 68–76, 1980. B. Riedel et al. Keeling, R. F., Kortzinger, A., and Gruber, N.: in a warming world, Annu. Rev. Mar. Sci., 2, 199–229, 2010. Kollmann, H. and Stachowitsch, M.: Long-term changes in the benthos of the Northern Adriatic Title Page 15 Sea: a phototransect approach, P. S. Z. N.I: Mar. Ecol., 22, 135–154, 2001. Koron, N., Ogrinc, N., Metzger, E., Riedel, B., and Faganeli, J.: Diagenesis and benthic fluxes Abstract Introduction of nutrients and metals during experimentally induced anoxia in the Gulf of Trieste (northern Adriatic Sea), Biogeosciences Discuss., 10, 11729–11755, doi:10.5194/bgd-10-11729-2013, Conclusions References 2013. Tables Figures 20 Kristensen, E., Penha-Lopes, G., Delefosse, M., Valdemarsen, T., Quintana, C. O., and Banta, G. T.: What is bioturbation? The need for a precise definition for fauna in aquatic sciences, Mar. Ecol.-Prog. Ser., 446, 285–302, 2012. J I Langlet, D., Geslin, E., Baal, C., Metzger, E., Lejzerowicz, F., Riedel, B., Zuschin, M., Pawlowski, J., Stachowitsch, M., and Jorissen, F. J.: Foraminiferal survival after long term J I 25 experimentally induced anoxia, Biogeosciences Discuss., 10, 9243–9284, doi:10.5194/bgd- Back Close 10-9243-2013, 2013a. Langlet, D., Baal, C., Geslin, E., Metzger, E., Zuschin, M., Riedel, B., Risgaard-Petersen, N., Full Screen / Esc Stachowitsch, M., and Jorissen, F. J.: Foraminiferal species responses to in situ experi- mentally induced anoxia in the Adriatic Sea, Biogeosciences Discuss., 10, 12065–12114, Printer-friendly Version 30 doi:10.5194/bgd-10-12065-2013, 2013b. Larade, K. and Storey, K. B.: A profile of the metabolic responses to anoxia in marine inverte- Interactive Discussion brates, in: Sensing, Signaling and Cell Adaptation, edited by: Storey, J. M. and Storey, K. B., Elsevier Science, New York, 27–36, 2002. 14388 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion Lenihan, H. S. and Peterson, C. H.: How habitat degradation through fishery disturbance en- hances impacts of hypoxia on oyster reefs, Ecol. Appl., 8, 128–140, 1998. BGD Lenihan, H. S., Peterson, C. H., Byers, J. E., Grabowski, J. H., Thayer, G. W., and Colby, D. R.: Cascading of habitat degradation: oyster reefs invaded by refuge fishes escaping stress, 10, 14333–14438, 2013 5 Ecol. Appl., 11, 764–782, 2001. Levin, L. A., Ekau, W., Gooday, A. J., Jorissen, F., Middelburg, J. J., Naqvi, S. W. A., Neira, C., Rabalais, N. N., and Zhang, J.: Effects of natural and human-induced hypoxia on coastal Anoxia and benthos, Biogeosciences, 6, 2063–2098, doi:10.5194/bg-6-2063-2009, 2009. macrofauna Long, W. C. and Seitz, R. D.: Trophic interactions under stress: hypoxia enhances foraging in behaviour 10 an estuarine food web, Mar. Ecol.-Prog. Ser., 362, 59–68, 2008. Malej, A. and Malačič, V.: Factors affecting bottom layer oxygen depletion in the Gulf of Trieste B. Riedel et al. (Adriatic Sea), Annales, 7, 33–42, 1995. McFarlane, I. D. and Lawn, I. D.: The senses of sea anemones: response of the SSI nerve net to chemical and mechanical stimuli, Hydrobiologia, 216/217, 599–604, 1991. Title Page 15 Metzger, E., Langlet, D., Viollier, E., Koron, N., Riedel, B., Stachowitsch, M., Faganeli, J., Tharaud, M., Geslin, E., and Jorissen, F.: Artificially induced migration of redox layers in Abstract Introduction a coastal sediment from the Northern Adriatic, Biogeosciences Discuss., 10, 12029–12063, doi:10.5194/bgd-10-12029-2013, 2013. Conclusions References Middelburg, J. J. and Levin, L. A.: Coastal hypoxia and sediment biogeochemistry, Biogeo- Tables Figures 20 sciences, 6, 1273–1293, doi:10.5194/bg-6-1273-2009, 2009. Mouillot, D., Villeger, S., Scherer-Lorenzen, M., and Mason, N. W. H.: Functional structure of biological communities predicts ecosystem multifunctionality, PloS One, 6, e17476, 2011. J I Mouillot, D., Bellwood, D. R., Baraloto, C., Chave, J., Galzin, R., Harmelin-Vivien, M., Kul- bicki, M., Lavergne, S., Lavorel, S., Mouquet, N., Paine, C. E. T., Renaud, J., and Thuiller, W.: J I 25 Rare species support vulnerable functions in high-diversity ecosystems, PLoS Biol., 11, Back Close e1001569, 2013. Munari, C. and Mistri, M.: Short-term hypoxia modulates Rapana venosa (Muricidae) prey pref- Full Screen / Esc erence in Adriatic lagoons, J. Exp. Mar. Biol. Ecol., 407, 166–170, 2011. Nestlerode, J. A. and Diaz, R. J.: Effects of periodic environmental hypoxia on predation of Printer-friendly Version 30 a tethered polychaete, Glycera americana: implications for trophic dynamics, Mar. Ecol.- Prog. Ser., 172, 185–195, 1998. Interactive Discussion Nilsson, H. C. and Rosenberg, R.: Hypoxic response of two marine benthic communities, Mar. Ecol.-Prog. Ser., 115, 209–217, 1994. 14389 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion Officer, C. B., Smayda, T. J., and Mann, R.: Benthic filter feeding: a natural eutrophication control, Mar. Ecol.-Prog. Ser., 9, 203–210, 1982. BGD O’Gorman, E. J., Yearsley, J. M., Crowe, T. P., Emmerson, M. C., Jacob, U., and Petchey, O. L.: Loss of functionally unique species may gradually undermine ecosystems, Proc. R. Soc. 10, 14333–14438, 2013 5 Lond. B, 278, 1886–1893, 2011. Ott, J. and Fedra, K.: Stabilizing properties of a high-biomass benthic community in a fluctuating ecosystem, Helgoländer Wiss. Meeresun., 30, 485–494, 1977. Anoxia and Pearson, T. H. and Rosenberg, R.: Macrobenthic succession in relation to organic enrichment macrofauna and pollution of the marine environment, Oceanogr. Mar. Biol. Ann. Rev., 16, 229–311, 1978. behaviour 10 Pihl, L., Baden, S. P., Diaz, R. J., and Schaffner, L. C.: Hypoxia-induced structural changes in the diet of bottom-feeding fish and , Mar. Biol., 112, 349–361, 1992. B. Riedel et al. Pretterebner, K., Riedel, B., Zuschin, M., and Stachowitsch, M.: Hermit crabs and their sym- bionts: reactions to artificially induced anoxia on a sublittoral sediment bottom, J. Exp. Mar. Biol. Ecol., 411, 23–33, 2012. Title Page 15 Rabalais, N. N., Harper, D. E. Jr., and Turner, R. E.: Responses of nekton and demersal and benthic fauna to decreasing oxygen concentrations, in: Coastal Hypoxia: Consequences for Abstract Introduction Living Resources and Ecosystems, Coastal and Estuarine Studies, edited by: Rabalais, N. N. and Turner, R. E., vol. 58, Am. Geophys. Union, Washington DC, 115–128, 2001. Conclusions References Rabalais, N. N., Díaz, R. J., Levin, L. A., Turner, R. E., Gilbert, D., and Zhang, J.: Dynam- Tables Figures 20 ics and distribution of natural and human-caused hypoxia, Biogeosciences, 7, 585–619, doi:10.5194/bg-7-585-2010, 2010. Riedel, B., Stachowitsch, M., and Zuschin, M.: Sea anemones and brittle stars: unexpected J I predatory interactions during induced in situ oxygen crises, Mar. Biol., 153, 1075–1085, 2008a. J I 25 Riedel, B., Zuschin, M., Haselmair, A., and Stachowitsch, M.: Oxygen depletion under glass: Back Close Behavioural responses of benthic macrofauna to induced anoxia in the Northern Adriatic, J. Exp. Mar. Biol. Ecol., 367, 17–27, 2008b. Full Screen / Esc Riedel, B., Zuschin, M., and Stachowitsch, M.: Tolerance of benthic macrofauna to hypoxia and anoxia in shallow coastal seas: a realistic scenario, Mar. Ecol.-Prog. Ser., 458, 39–52, 2012. Printer-friendly Version 30 Roberts, S. J. and Brink, K.: Managing marine resources sustainably, Environment, 52, 44–52, 2010. Interactive Discussion Rosenberg, R., Hellman, B., and Johansson, B.: Hypoxic tolerance of marine benthic fauna, Mar. Ecol.-Prog. Ser., 79, 127–131, 1991. 14390 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion Rufino, M. M., Maynou, F., Abelló, P., and Sardá, F.: Spatial and environmental factors affecting the distribution of the main decapod crustacean prey species in the NW Mediterranean, BGD Hydrobiologia, 555, 129–141, 2006. Sagasti, A., Schaffner, L. C., and Duffy, J. E.: Effects of periodic hypoxia on mortality, feeding 10, 14333–14438, 2013 5 and predation in an estuarine epifaunal community, J. Exp. Mar. Biol. Ecol., 258, 257–283, 2001. Sala, E. and Knowlton, M.: Global marine biodiversity trends, Annu. Rev. Environ. Resour., 31, Anoxia and 93–122, 2006. macrofauna Sandberg, E.: Does short-term oxygen depletion affect predator–prey relationships in zooben- behaviour 10 thos? Experiments with the isopod Saduria entomon, Mar. Ecol.-Prog. Ser., 103, 73–80, 1994. B. Riedel et al. Sandberg, E., Tallqvist, M., and Bonsdorff, E.: The effects of reduced oxygen content on preda- tion and siphon cropping by the brown shrimp, Crangon crangon, P. S. Z. N.I: Mar. Ecol., 17, 411–423, 1996. Title Page 15 Sassaman, C. and Mangum, C. P.: Adaptions to environmental oxygen levels in infaunal and epifaunal sea anemones, Biol. Bull., 143, 657–678, 1972. Abstract Introduction Schinner, G. O.: Burrowing behavior, substratum preference, and distribution of Schizaster canaliferus (Echinoidea: Spatangoida) in the northern Adriatic Sea, Mar. Ecol., 14, 129– Conclusions References 145, 1993. Tables Figures 20 Seitz, R. D., Marshall, L. S., Hines, A. H., Clark, K. L.: Effects of hypoxia on predator–prey dy- namics of the blue crab Callinectes sapidus and the Baltic clam Macoma balthica in Chesa- peake Bay, Mar. Ecol.-Prog. Ser., 257, 179–188, 2003. J I Shick, J. M. (Ed.): A functional biology of sea anemones, Chapman & Hall, New York, 395 pp., 1991. J I 25 Shimps, E. L., Rice, J. A., and Osborne, J. A.: Hypoxia tolerance in two juvenile estuary- Back Close dependent fishes, J. Exp. Mar. Biol. Ecol., 325, 146–162, 2005. Shives, J. A. and Dunbar, S. G.: Behavioral responses to burial in the hermit crab, Pagurus Full Screen / Esc samuelis: implications for the fossil record, J. Exp. Mar. Biol. Ecol., 388, 33–38, 2010. Sibley, P. K., Chappel, M. J., George, T. K., Solomon, K. R., and Liber, K.: Integrating effects Printer-friendly Version 30 of stressors across levels of biological organization: examples using organophosphorus in- secticide mixtures in field-level exposures, J. Aquat. Ecosyst. Stress Recov., 7, 117–130, Interactive Discussion 2000.

14391 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion Sih, A., Ferrari, M. C. O., and Harris, D. J.: Evolution and behavioral responses to human- induced rapid environmental change, Evol. Appl., 4, 367–387, 2011. BGD Solan, M., Cardinale, B. J., Downing, A. L., Engelhardt, K. A., Ruesink, J. L., and Srivas- tava, D. S.: Extinction and ecosystem function in the marine benthos, Science, 306, 1177– 10, 14333–14438, 2013 5 1180, 2004. Smith, V. H. and Schindler, D. W.: Eutrophication science: where do we go from here?, Trends Ecol. Evol., 24, 201–207, 2009. Anoxia and Stachowitsch, M.: Mass mortality in the Gulf of Trieste: the course of community destruc- macrofauna tion, P. S. Z. N.I: Mar. Ecol., 5, 243–264, 1984. behaviour 10 Stachowitsch, M.: Anoxia in the Northern Adriatic Sea: Rapid death, slow recovery, Geol. Soc. Spec. Publ., 58, 119–129, 1991. B. Riedel et al. Stachowitsch, M. and Fuchs, A.: Long-term changes in the benthos of the Northern Adriatic Sea, Annales, 7, 7–16, 1995. Stachowitsch, M., Riedel, B., Zuschin, M., and Machan, R.: Oxygen depletion and benthic Title Page 15 mortalities: the first in situ experimental approach to documenting an elusive phenomenon, Limnol. Oceanogr. Methods, 5, 344–352, 2007. Abstract Introduction Stauber, L. A.: Pinnotheres ostreum, parasitic on the American oyster, Ostrea (Gryphaea) vir- ginica, Biol. Bull., 88, 269–291, 1945. Conclusions References Tallqvist, M.: Burrowing behaviour of the Baltic clam Macoma balthica: effects of sediment type, Tables Figures 20 hypoxia and predator presence, Mar. Ecol.-Prog. Ser., 212, 183–191, 2001. Taylor, P. R.: Hermit crab fitness: the effect of shell condition and behavioral adaptations on environmental resistance, J. Exp. Mar. Biol. Ecol., 52, 205–218, 1981. J I Taylor, D. L. and Eggleston, D. B.: Effects of hypoxia on an estuarine predator-prey interac- tion: foraging behavior and mutual interference in the blue crab Callinectes sapidus and the J I 25 infaunal clam prey Mya arenaria, Mar. Ecol.-Prog. Ser., 196, 221–237, 2000. Back Close Taylor, E. W., Butler, P. J., and Al-Wassia, A.: Some responses of the shore crab, Carcinus maenas (L.), to progressive hypoxia at different acclimation temperatures and salinities, J. Full Screen / Esc Comp. Physiol., 122, 391–402, 1977. Thayer, G. W., Schaaf, W. E., Angelovic, J. W., and LaCroix, M. W.: Caloric measurements of Printer-friendly Version 30 some estuarine organisms, Fish. Bull., 71, 289–296, 1973. Thorson, G.: Parallel level-bottom communities, their temperature adaptation, and their ‘bal- Interactive Discussion ance’ between predators and food animals, in: Perspectives in Marine Biology, edited by: Buzzata-Traverso, A. A., University of California Press, Berkeley, California, 67–86, 1957. 14392 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion Thrush, S. F. and Dayton, P. K.: Disturbance to marine benthic habitats by trawling and dredg- ing: implications for marine biodiversity, Ann. Rev. Ecol. Syst., 33, 449–473, 2002. BGD Thrush, S. F., Hewitt, J., Gibbs, M., Lundquist, C., and Norkko, A.: Functional role of large or- ganisms in intertidal communities: community effects and ecosystem function, Ecosystems, 10, 14333–14438, 2013 5 9, 1029–1040, 2006. Tilman, D., Knops, J., Wedin, D., Reich, P., Ritchie, M., and Siemann, E.: The influence of functional diversity and composition on ecosystem processes, Science, 277, 1300–1302, Anoxia and 1997. macrofauna Tuomainen, U. and Candolin, U.: Behavioural responses to human-induced environmental behaviour 10 change, Biol. Rev., 86, 640–657, 2011. UNEP.: Marine and Coastal Ecosystems and Human Wellbeing: a Synthesis Report based on B. Riedel et al. the Findings of the Millennium Ecosystem Assessment, UNEP, 76 pp., 2006. Vaquer-Sunyer, R. and Duarte, C. M.: Thresholds of hypoxia for marine biodiversity, P. Natl. Acad. Sci. USA, 105, 15452–15457, 2008. Title Page 15 Vaquer-Sunyer, R. and Duarte, C. M.: Sulfide exposure accelerates hypoxia-driven mortality, Limnol. Oceanogr., 55, 1075–1082, 2010. Abstract Introduction Vaquer-Sunyer, R. and Duarte, C. M.: Temperature effects on oxygen thresholds for hypoxia in marine benthic organisms, Glob. Change Biol., 17, 1788–1797, 2011. Conclusions References Vistisen, B. and Vismann, B.: Tolerance to low oxygen and sulfide in Amphiura filiformis and Tables Figures 20 Ophiura albida (Echinodermata: Ophiuroidea), Mar. Biol., 128, 241–246, 1997. Wahl, M.: The fluffy sea anemone Metridium senile in periodically oxygen depleted surround- ings, Mar. Biol., 81, 81–86, 1984. J I Ward, J. E. and Shumway, S. E.: Separating the grain from the chaff: particle selection in suspension and deposit-feeding bivalves, J. Exp. Mar. Biol. Ecol., 300, 83–130, 2004. J I 25 Wicksten, M. K.: A review and a model of decorating behavior in spider crabs (Decapoda, Back Close Brachyura, Majidae), Crustaceana, 64, 314–325, 1993. Worm, B., Barbier, E. B., Beaumont, N., Duffy, J. E., Folke, C., Halpern, B. S., Jackson, J. B. C., Full Screen / Esc Lotze, H. K., Micheli, F., Palumbi, S. R., Sala, E., Selkoe, K. A., Stachowicz, J. J., and Wat- son, R.: Impacts of biodiversity loss on ocean ecosystem services, Science, 314, 787–790, Printer-friendly Version 30 2006. Wu, R. S. S.: Hypoxia: from molecular responses to ecosystem responses, Mar. Pollut. Bull., Interactive Discussion 45, 35–45, 2002. Wu, R. S. S.: Effects on fish reproduction and development, Fish Physiol., 27, 79–141, 2009. 14393 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion Wurzian, R. S.: Predator – prey interaction between the crab Pilumnus hirtellus (Leach) and the brittle star Ophiothrix quinquemaculata (D.Chiaje) on a mutual sponge substrate, in: Bi- BGD ology of Benthic Organisms, 11th Eur. Mar. Biol. Symp., Galway, edited by: Keegan, B. F., O’Ceidigh, P., and Boaden, P. J. S., Pergamon Press, Oxford, 613–620, 1977. 10, 14333–14438, 2013 5 Xu, J., Liu, Y., Cui, S., and Miao, X.: Behavioral responses of tilapia (Oreochromis niloticus) to acute fluctuations in dissolved oxygen levels as monitored by computer vision, Aquac. Eng., 35, 207–217, 2006. Anoxia and Zhang, J., Gilbert, D., Gooday, A. J., Levin, L., Naqvi, S. W. A., Middelburg, J. J., Scranton, M., macrofauna Ekau, W., Peña, A., Dewitte, B., Oguz, T., Monteiro, P. M. S., Urban, E., Rabalais, N. N., It- behaviour 10 tekkot, V., Kemp, W. M., Ulloa, O., Elmgren, R., Escobar-Briones, E., and Van der Plas, A. K.: Natural and human-induced hypoxia and consequences for coastal areas: synthesis and fu- B. Riedel et al. ture development, Biogeosciences, 7, 1443–1467, doi:10.5194/bg-7-1443-2010, 2010.

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B. Riedel et al. Table A1. Summary of the 11 deployments. No: number of deployment; ww: wet weight; –: no data.

No Date Duration deployment (h) Duration (h) H2S(µM) pH Temp. Biomass (total) Title Page open (frame) closed (chamber) hypoxia anoxia average last h final ◦C gww 0.25m−2 Abstract Introduction 2 17–22 Sep 2005 – 132.8 20.1 81.8 167.6 – 18.5 436.7 3 24–27 Sep 2005 – 69.4 46.1 5.2 5.5 – 17.8 682.1 4 27 Sep–1 Oct 2005 – 101.6 41.6 28.8 36.8 – 17.6 604.7 Conclusions References 6 5–8 Aug 2006 22.4 48.3 12.5 22.9 5.2 7.9 18.8 – 7 17–21 Sep 2006 20.9 72.1 33.8 28.7 124.2 7.7 19.7 839.8 8 21–24 Sep 2006 21.7 41.9 22.7 8.5 0.0 – 20.4 526.3 Tables Figures 9 25–29 Sep 2006 21.9 73 40.5 19.1 19.3 7.8 20.6 648.9 10 29 Sep–2 Oct 2006 22.7 40.3 16.7 13.9 11.8 7.9 21.4 629.2 11 5–10 Oct 2006 23.6 95.4 11.4 78.3 106.7 7.5 21.3 724.0 J I 12 10–14 Oct 2006 25.4 75.2 33.6 24.2 18.2 7.8 21.3 631.6 13 17–21 Oct 2006 – 94.6 52.9 25.1 124.5 7.8 20.4 1042.7 J I

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Table A2. Macrobenthic species (32 species and 2 species groups) recorded. Group abbre- B. Riedel et al. viation: Ant: Anthozoa, Nem: Nemertini, Sip: Sipunculida, Gas: Gastropoda, Biv: Bivalvia, Pol: Polychaeta, Dec: Decapoda, Hol: Holothuroidea, Ech: Echinoidea, Oph: Ophiuroidea, Asc: As- cidiacea. Life habit: epi: epifauna, in: infauna, cry: cryptic fauna; SF: suspension feeder, P: Title Page predator, D: deposit feeder. Behaviour subcategories: 1 visible, non-visible; 2 horizontal, verti- 3 4 cal (both minor, major), no locomotion; open, half open, closed; up-, side-, downward ori- Abstract Introduction entated; 5 bottom, middle (< 5 cm above sediment), high/top (> 5 cm); 6a column; 6b tentacles and oral disc: original, discoloured; 7 normal, “puckered”; 8 normal, protruded; 9 intact, peeled Conclusions References off; 10 minor, major; 11 overturned/moribund; 12 retracted, extended; 13 upright, overturned; 14 Tables Figures closed, half open, normal, widely gaping; 15 normal, swollen, retracted; 16 extended, partially retracted, fully retracted; 17 inside burrow, outside (on sediment); 18 normal, discarded; 19 nor- mal, extended, out of shell; 20 suspension feeding, arm tipping, arms down/moribund; – not J I evaluated/applicable. J I

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1 2 5 Anoxia and Group Species N Life habits Visibility Locomotion Movement Body posture Location Interaction Species-specific responses macrofauna Ant Calliactis 6 epi, ses, SF + – rotation, contraction, – + discolouration6a, mouth7, pharynx8, 3 parasitica detachment crown habitus acontia1, periderm9 behaviour and orientation4 Ant Cereus 17 epi, ses, SF – – rotation contraction, – + discolouration6b, mouth7, pharynx8 peduncu- crown habitus3, B. Riedel et al. latus retraction, extension10 Nem Tubulanus 1 in, mob, P + + squirm – – – – sp. Title Page Sip indet. 4 in, mob, D + + squirm – – – – species Gas Diodora 4 epi, mob, P + + – orientation11, foot ––– Abstract Introduction sp. habitus12 Gas Fusinus 1 epi, mob, P + + – foot habitus12 + –– rostratus Conclusions References Gas Hexaplex 23 epi, mob, P + + turn, shell foot habitus12 + –– trunculus orientation13 Gas Murex 1 epi, mob, P + + turn – + –– Tables Figures brandaris Biv Abra alba 2 in, mob, D + + – siphon1 ––– 14 15 Biv Chlamys 7 epi, mob, SF – + – valve gape – + mantle tissue J I varia Biv Corbula 37 in, mob, SF + + ––––– gibba J I Biv Venerupis 1 in, mob, SF + + – foot habitus12, ––– cf. rhom- siphon1 boides Back Close Pol indet. 17 in, mob, D/P + + squirm – – – – species Pol Glycera 1 in, mob, P + + squirm – – – – Full Screen / Esc sp. Pol Protula 8 epi, ses, SF – – – crown extension16 – + – tubularia Printer-friendly Version

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Table A2. Continued. BGD

1 2 5 10, 14333–14438, 2013 Group Species N Life habits Visibility Locomotion Movement Body posture Location Interaction Species-specific responses Dec Alpheus 2 epi, mob, D + + body and extremity, orientation11 +17 + – glaber turn Dec Ebalia 3 epi, mob, P + + body and extremity, – + + – tuberosa turn Anoxia and Dec Ethusa mas- 3 epi/cryp, + + body and extremity, – + + camouflage18 carone mob, P turn macrofauna Dec Eurynome 2 epi, mob, P + + body and extremity, – + + – aspera turn behaviour Dec Galathea 3 epi/cryp, + + body and extremity, – + + – spp. mob, P turn Dec Inachus sp. 1 epi, mob, P + + body and extremity, – + + – B. Riedel et al. turn Dec Macropodia 7 epi, mob, P + + body and extremity, – + + – spp. turn Dec Nepinnotheres 2 epi/cryp, + + body and extremity, – + + host abandonment pinnotheres mob, P turn Dec Paguristes 25 epi, mob, P + + body, turn posture19 + + shell orientation13 Title Page eremita Dec Pilumnus 17 epi/cryp, + + body and extremity, – + + – spinifer mob, P turn Abstract Introduction Dec Pisidia longi- 4 epi/cryp, + + body and extremity, – + + – mana mob, P turn Hol Ocnus planci 4 epi, mob, SF – + – contraction, – + – Conclusions References elongation10, crown habitus3and Tables Figures orientation4 Ech Psammechi- 17 epi, mob, D + + spine movement – – – camouflage nusmicrotuber- culatus J I Ech Schizaster 22 in, mob, D + + spine movement orientation11 – – sediment bulging canaliferus Oph Ophiothrix 28 epi, mob, SF + + – body + + fragmentation J I quinquemac- habitus20 ulata Oph Ophiura spp. 3 inf, mob, D + + ––– + fragmentation Back Close Oph Amphiura 10 inf, mob, D + + ––– + armtips1, fragmentation chiajei Asc Microcosmus 10 epi, ses, SF – – – siphon – + – Full Screen / Esc spp. habitus3and elongation, contraction, drooping Printer-friendly Version Asc Phallusia 9 epi, ses, SF – – – siphon – + – mammilata habitus3, contraction, Interactive Discussion drooping

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Individual Population Community Ecosystem behaviour Physiology/metabolism Abundance Biomass Ecosystem functions B. Riedel et al. Behaviour Age structure Species diversity Productivity Growth Recruitment Dominance Food web Mortality Social aggregation Functional effects Habitat structure Reproduction Trophic dynamics Title Page Predation rates Abstract Introduction

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Intact ecosystem Chemical pollution Tipping point J I Eutrophication/hypoxia Climate change J I Fig. 1. Conceptual link between hypoxia and the multi-level effects in marine ecosystems. Hy- poxia induces individual responses, which in turn affect population attributes, community dy- Back Close namics and ultimately biodiversity and ecosystem integrity. The interactive and cumulative ef- Full Screen / Esc fects of multiple human stressors increasingly force the system to a critical tipping point and qualitatively altered state. Printer-friendly Version

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Anoxia and Open (frame) Closed (chamber) 5 60 macrofauna Hydrogen sulphide (µM) ) behaviour -1 4 oxygen B. Riedel et al. Normoxia H S 40 3 2 Title Page behavioural reactions 2 Abstract Introduction Mild 20 Conclusions References 1 Moderate hypoxia mortality

Dissolved oxygen (ml l oxygen Dissolved Tables Figures Severe Anoxia 0 0 1 12 21 1 12 24 36 48 60 72 J I Duration (h) J I Fig. 2. Schematic course of all 11 deployments (oxygen, H S, behaviour, mortality) based on 2 Back Close averaged values in Table A1. Hypoxia threshold 2 mL dissolved oxygen [DO]L−1; dashed lines −1 (1 and 0.5 mL DOL ) separate different stages of hypoxia. Full Screen / Esc

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ab BGD 25 10, 14333–14438, 2013 vagile substrate c 1 20 aggregations Anoxia and macrofauna 15 3 behaviour

10 B. Riedel et al. c 4 5 b b d Title Page No. of observations (%) CI 95 a a a a b 0 Abstract Introduction 12691 2753 2193 7668 12749 ≥2 <2 <1 <0.5 0 2 Conclusions References DO category (ml l-1) Tables Figures

Fig. 4. (a) Mean percentage of observations of crustacean aggregations (black squares) and J I of investigated specimens atypically using vagile species as substrates (open squares) in the 5 oxygen categories. Numbers below x-axes: number of photographs evaluated per oxygen J I category. Same letters above error bars: no significant difference between means. (b) Atypical Back Close −1 aggregations during severe hypoxia (0.2 mLDOL ; no H2S): Numerous Pisidia longimana ag- gregate on the ascidians Phallusia mammilata (1) and Microcosmus spp. (2). Stressed brittle Full Screen / Esc stars (Ophiothrix quinquemaculata) cling to the substrate (top arrow), one individual already moribund on sediment surface in lower right corner (bottom arrow). The hermit crab Paguristes Printer-friendly Version eremita (3) with symbiotic sea anemone Calliactis parasitica (third arrow from top) on shell, on a sponge. Note O. quinquemaculata (second arrow from top) using the crab’s shell as elevated Interactive Discussion substrate. Freshly emerged polychaete on ascidian (4).

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Fig. 5. Predation by Cereus pedunculatus on Ophiothrix quinquemaculata (a–e) and Calliactis parasitica on Ethusa Printer-friendly Version mascarone (f–g). (a) Moribund brittle star (white arrow) on sediment, Cereus (black arrow) with elevated tentacle crown, minor extension. (b) Anemone catches arm brittle star arm. (c) Brittle star pulled onto tentacle crown. (d) Prey Interactive Discussion ingested. (e) Regurgitation of remains; note still moving infaunal sea urchin Schizaster canaliferus. (f) Ethusa (white arrow), with recently discarded decoration, moving towards widely opened tentacle crown (black arrow). (g) Calliactis ingests crab, legs still protruding from mouth. 14403 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion BGD 10, 14333–14438, 2013 Mortalities (no. of individuals) 1 149309094 33 17 7 7 3 1 2 Anoxia and 100 Echinodermata macrofauna Decapoda behaviour Polychaeta 80 Dead/total number B. Riedel et al. E: 68/73

60 D: 191/209 P: 18/20 Title Page AS: 5/19 40 A: 4/38 Abstract Introduction M: 13/136 Ascidiacea Mortalities (%) 20 Anthozoa Conclusions References Mollusca Tables Figures 0 <0.8 0.6 0.4 0.2 <10 30 50 70 J I moderate severe hypoxia anoxia DO (ml l-1) Duration (h) J I Back Close Fig. 6. Number of individuals dying (N = 299) across hypoxia (mL dissolved oxygen [DO]L−1) and anoxia duration (h) and mortality curves of higher taxa (%) in all deployments. Rapid in- Full Screen / Esc crease, peak and decrease in mortalities at transition from severe hypoxia to anoxia highlighted. Elongated vertical line on first x-axis separates moderate and severe hypoxia. Printer-friendly Version

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Recovery likelihood behaviour Predation Scavenging B. Riedel et al. effects Moribund Mortalities

Normal Stress Title Page Stretching Water Elevated Atypical column structures aggregations Abstract Introduction Highly mobile Avoid/flee area fauna Vertical Horizontal Species-specific atypical Dead zone Conclusions References behaviours Epifauna More Less ABC movement movement Tables Figures Cryptic epifauna Exposure Behavioural effectsBehavioural Ecological

Infauna Emergence J I Normoxia Increasing hypoxia Anoxia J I Fig. 7. Synthesis of behavioural reactions and accompanying ecological effects. See text for examples of each response category. Back Close

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14405 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion BGD Fig A1 Calliactis parasitica (N = 6) 10, 14333–14438, 2013 (a) discolouration (b) crown open (c) crown closed (d) crown upward 100 c 80 a b Anoxia and c c b b 60 b b macrofauna c behaviour 40 c d a 20 a a a B. Riedel et al. a a a b 0 797 459 361 1667 1776 797 459 361 1667 1776 797 459 361 1667 1776 797 459 361 1667 1776 (e) crown sideward (f) body contraction (g) body rotation (h) pharynx protrusion 100 Title Page

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J I Fig. A1. A1–A33. Species-specific changes in behaviour in the 5 oxygen categories. Numbers below x-axes: number of photographs evaluated per dissolved oxygen [DO] category. Analyses Back Close are by Mann–Whitney U tests (p < 0.05). Same letters above error bars indicate no significant difference between means of the respective oxygen categories. The proportion of subcategory Full Screen / Esc behaviours do not necessarily total 100 % because not all subcategories are depicted. Calliactis parasitica (N = 6). Printer-friendly Version

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Fig A2 Cereus pedunculatus (N = 17) BGD (a) discolouration (b) crown open (c) crown closed (d) retraction 100 10, 14333–14438, 2013 c 80 e d b 60 d a Anoxia and e 40 d a macrofauna b c a 20 c c behaviour a b b bc d d 0 4963 1085 845 2832 6666 4963 1085 845 2832 6666 4963 1085 845 2832 6666 4963 1085 845 2832 6666 B. Riedel et al. (e) body contraction (f) body rotation (g) pharynx protrusion (h) extension 100 minor 80 major e c Title Page 60 d d d 40 d Abstract Introduction c b e e e 20 b d c c b Conclusions References a a a b a a a b c 0 No. of observations (%) CI 95 No. 4963 1085 845 2832 6666 4963 1085 845 2832 6666 4963 1085 845 2832 6666 4963 1085 845 2832 6666 ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 Tables Figures (i) extension (total) 100 DO category (ml l-1) d e 80 J I c 60 J I 40 b 20 Back Close a 0 4963 1085 845 2832 6666 Full Screen / Esc ≥2 <2 <1 <0.5 0 DO category (ml l-1) Printer-friendly Version

Fig. A2. Cereus pedunculatus (N = 17). Interactive Discussion

14407 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion BGD 10, 14333–14438, 2013 Fig A3 Tubulanus sp. (N = 1) Anoxia and (a) visible (b) lomotion & movement macrofauna 100 behaviour horizontal locomotion B. Riedel et al. 80 squirming in place

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40 a Abstract Introduction b 20 Conclusions References a a a a a Tables Figures 0 1060 248 233 138 1415 0 0 0 8/6 293/206

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Anoxia and macrofauna behaviour Fig A5 Diodora sp. (N = 4) (a) visible (b) hor. locomotion (c) overturned (d) foot extended B. Riedel et al. 100 d b c c 80 a Title Page 60 a b c 40 a Abstract Introduction a b b b b ab b 20 a a a a Conclusions References 0 1120 207 179 965 661 585 100 128 949 661 585 100 128 949 661 585 100 128 949 661 Tables Figures No. of observations (%) CI 95 No. ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 DO category (ml l-1) J I

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Anoxia and macrofauna behaviour Fig A6 Fusinus rostratus (N = 1) (a) visible (b) location high/top (c) locomotion (d) foot habitus B. Riedel et al. 100 a a a horizontal retracted 80 a vertical extended Title Page 60 b b b 40 Abstract Introduction b 20 a b b b a a b Conclusions References a a a a a a a a a a a ab ab ab ab 0 295 29 35 94 739 295 29 35 94 739 295 29 35 89 367 295 29 35 89 367 Tables Figures No. of observations (%) CI 95 No. ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 DO category (ml l-1) J I

Fig. A6. Fusinus rostratus (N = 1). J I

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Anoxia and macrofauna behaviour Fig A7 Hexaplex trunculus (N = 23) (a) visible (b) location high/top (c) locomotion (d) foot habitus B. Riedel et al. 100 horizontal retracted 80 d vertical extended Title Page 60 c d b e a a 40 c c Abstract Introduction a c a a 20 a b b b b bc b Conclusions References a c a a a a a a a a 0 6903 1497 1161 3231 9234 6903 1497 1161 3231 9234 2778 546 358 915 4072 2046 377 245 772 4072 Tables Figures No. of observations (%) CI 95 No. 2046 377 245 772 4072 ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 DO category (ml l-1) J I

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Anoxia and macrofauna Fig A8 Murex brandaris (N = 1) behaviour (a) visible (b) location high/top (c) locomotion 100 B. Riedel et al. horizontal a c 80 b b vertical a Title Page 60 a a a b Abstract Introduction 40 b 20 c c Conclusions References a a a a a a a a 0 192 70 45 343 43 82 34 29 316 41 82 34 29 316 41 Tables Figures No. of observations (%) CI 95 No. ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 DO category (ml l-1) J I

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Anoxia and macrofauna Fig A9 Abra alba (N = 2) behaviour (a) visible (b) hori. locomotion (c) siphon visible 100 B. Riedel et al. c minor 80 major

60 Title Page b a 40 Abstract Introduction a 20 a b Conclusions References a a a a a 0 590 58 70 188 1478 0 0 0 68 1168 0 0 0 68 1168 Tables Figures No. of observations (%) CI 95 No. ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 DO category (ml l-1) J I

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14414 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion BGD 10, 14333–14438, 2013 Fig A10 Chlamys varia (N = 7) (a) shell normal (open) (b) shell widely gaping (c) mantle tissue normal (d) mantle tissue swollen 100 Anoxia and a b b a b d macrofauna 80 c c c behaviour 60 d B. Riedel et al. 40 e d 20 c e b a a a b a 0 Title Page 1875 516 374 765 2978 1875 516 374 765 2978 1875 516 374 765 2978 1875 516 374 765 2978

(e) mantle tissue retracted ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 Abstract Introduction 100 DO category (ml l-1) 80 Conclusions References c No. of observations (%) CI 95 No. 60 Tables Figures

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60 Title Page a 40 d Abstract Introduction c c b b b 20 a Conclusions References a a c d b b c Tables Figures 0 12632 2119 1944 6139 13891 1422 388 488 1542 4488 J I No. of observations (%) CI 95 No. ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 J I -1 DO category (ml l ) Back Close

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14416 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion BGD 10, 14333–14438, 2013

Anoxia and macrofauna Fig A12 Venerupis cf. rhomboides (N = 1) behaviour (a) visible (b) hor. locomotion (c) foot habitus & siphon 100 B. Riedel et al. c minor foot extended a a 80 major siphon visible Title Page 60 b 40 Abstract Introduction a a 20 a b a Conclusions References a a a a 0 304 39 24 298 226 0 0 0 130 222 0 0 0 130 222 Tables Figures No. of observations (%) CI 95 No. ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 DO category (ml l-1) J I

Fig. A12. Venerupis cf. rhomboides (N = 1). J I Back Close

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14417 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion BGD 10, 14333–14438, 2013 Fig A13 Indet. Polychaeta (N = 17) & Glycera sp. (N = 1) Anoxia and (a) visible (b) lomotion & movement macrofauna 100 behaviour horizontal locomotion 80 squirming in place B. Riedel et al. e 60 a Title Page d 40 a Abstract Introduction b b Conclusions References 20 c c a b a Tables Figures 0 5250 1366 1174 5135 5235 0 2 92 1708 3068

No. of observations (%) CI 95 No. 0 2 92 1708 3068 J I ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 J I DO category (ml l-1) Back Close

Fig. A13. Indet. Polychaeta (N = 17) and Glycera sp. (N = 1). Full Screen / Esc

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14418 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion BGD 10, 14333–14438, 2013 Fig A14 Protula tubularia (N = 8) Anoxia and (a) crown extended (b) crown fully retracted macrofauna 100 behaviour b b 80 a c B. Riedel et al. d

60 Title Page d 40 c a Abstract Introduction b b 20 Conclusions References Tables Figures 0 2279 467 422 1971 2734 2279 467 422 1971 2734 J I No. of observations (%) CI 95 No. ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 J I -1 DO category (ml l ) Back Close

Fig. A14. Protula tubularia (N = 8). Full Screen / Esc

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14419 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion BGD 10, 14333–14438, 2013

Anoxia and macrofauna behaviour Fig A15 Alpheus glaber (N = 2) B. Riedel et al. (a) visible (b) locomotion (c) overturned

4 25 No. h of observations ) -1 20 3 oxygen peak Title Page (ml l decl.1 2 mortality -1 15 2 Abstract Introduction 10 H S H S H S 1 2 2 2 5 Conclusions References Mean DO h -1 0 0 Tables Figures 0 24 48 72 96 0 24 48 72 96 0 24 48 72 96 Duration (h) J I Fig. A15. Alpheus glaber (N = 2). J I

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14420 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion BGD 10, 14333–14438, 2013 Fig A16 Ebalia tuberosa (N = 3) (a) visible (b) locomotion (total) (c) locomotion (d) body movement Anoxia and 100 d e horizontal macrofauna 80 a vertical behaviour 60 b a b b B. Riedel et al. 40 a a c 20 c c a b ab b a 0 Title Page 1138 229 179 466 655 0 5 22 406 529 0 5 22 406 529 0 5 22 406 529

(e) location high/top ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 Abstract Introduction 100 DO category (ml l-1) Conclusions References 80

No. of observations (%) CI 95 No. 60 Tables Figures b 40 J I 20 a a 0 J I 0 5 22 406 529 ≥2 <2 <1 <0.5 0 Back Close DO category (ml l-1) Full Screen / Esc Fig. A16. Ebalia tuberosa (N = 3). Printer-friendly Version

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14421 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion BGD 10, 14333–14438, 2013

Anoxia and macrofauna behaviour Fig A17 Ethusa mascarone (N = 3) (a) visible (b) camou age (c) locomotion (d) body movement B. Riedel et al. 100 a a a a a a a horizontal 80 b b vertical Title Page 60 b Abstract Introduction 40 a c a a a 20 b a b Conclusions References c a b b c a d 0 820 262 181 381 961 820 262 181 381 961 648 201 138 311 881 648 201 138 311 881 Tables Figures No. of observations (%) CI 95 No. ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 DO category (ml l-1) J I

Fig. A17. Ethusa mascarone (N = 3). J I

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14422 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion BGD 10, 14333–14438, 2013 Fig A18 Eurynome aspera (N = 2) (a) visible (b) locomotion (c) body movement (d) extremity movement 100 Anoxia and horizontal c d c macrofauna 80 b vertical a behaviour 60 a a a b b B. Riedel et al. 40 a a a a a 20 a a a b b b b b c c 0 Title Page 491 133 122 548 291 263 124 84 533 220 263 124 84 533 220 263 124 84 533 220

(e) location high/top ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 Abstract Introduction 100 DO category (ml l-1) b c 80 Conclusions References

No. of observations (%) CI 95 No. 60 Tables Figures

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20 J I a a a 0 J I 263 124 84 533 220 ≥2 <2 <1 <0.5 0 Back Close DO category (ml l-1) Full Screen / Esc Fig. A18. Eurynome aspera (N = 2). Printer-friendly Version

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14423 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion BGD 10, 14333–14438, 2013

Anoxia and macrofauna behaviour Fig A19 Galathea spp. (N = 3) (a) visible (b) locomotion (c) body movement (d) location high/top B. Riedel et al. 100 d a horizontal 80 vertical bd b b Title Page 60 b c b 40 c b ab b Abstract Introduction a a a 20 a d c a ac Conclusions References e d c a a 0 978 183 168 357 228 194 92 46 211 152 194 92 46 211 152 194 92 46 211 152 Tables Figures No. of observations (%) CI 95 No. ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 DO category (ml l-1) J I

Fig. A19. Galathea spp. (N = 3). J I

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14424 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion BGD 10, 14333–14438, 2013 Fig A20 Inachus sp. (N = 1)

(a) visible (b) locomotion (c) body movement (d) extremity movement Anoxia and 100 c b b b horizontal macrofauna 80 vertical a a behaviour 60 a ab a a a B. Riedel et al. 40 a a a bc c 20 a b a a a d b b a 0 Title Page 352 52 33 57 214 173 52 33 57 180 173 52 33 57 180 173 52 33 57 180

(e) location high/top ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 Abstract Introduction 100 DO category (ml l-1) b 80 Conclusions References

No. of observations (%) CI 95 No. 60 Tables Figures

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20 c J I a a ac 0 J I 173 52 33 57 180 ≥2 <2 <1 <0.5 0 Back Close DO category (ml l-1) Full Screen / Esc Fig. A20. Inachus sp. (N = 1). Printer-friendly Version

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14425 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion BGD 10, 14333–14438, 2013 Fig A21 Macropodia spp. (N = 7)

(a) visible (b) locomotion (c) body movement (d) extremity movement Anoxia and 100 b d horizontal macrofauna 80 c bc vertical behaviour 60 a b a b a a B. Riedel et al. 40 a b c b a 20 a c ab b d d e c c d 0 Title Page 1953 435 327 993 2996 982 381 297 899 2919 982 381 297 899 2919 982 381 297 899 2919

(e) location high/top ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 Abstract Introduction 100 DO category (ml l-1) Conclusions References 80 c c

No. of observations (%) CI 95 No. 60 Tables Figures

40 b d J I 20 a

0 J I 982 381 297 899 2919 ≥2 <2 <1 <0.5 0 Back Close DO category (ml l-1) Full Screen / Esc Fig. A21. Macropodia spp. (N = 7). Printer-friendly Version

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14426 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion BGD 10, 14333–14438, 2013

Anoxia and macrofauna behaviour Fig A22 Nepinnotheres pinnotheres (N = 2) (a) visible (b) locomotion (c) body movement (d) location high/top B. Riedel et al. 100 horizontal 80 c vertical a b Title Page 60 a b 40 b Abstract Introduction a a a 20 b Conclusions References a a a 0 460 101 101 523 954 0 0 0 44 604 0 0 0 44 604 0 0 0 44 604 Tables Figures No. of observations (%) CI 95 No. ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 DO category (ml l-1) J I

Fig. A22. Nepinnotheres pinnotheres (N = 2). J I

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14427 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion BGD 10, 14333–14438, 2013 Fig A23 Paguristes eremita (N = 25) (a) location (b) locomotion (total) (c) body movement (d) posture normal 100 Anoxia and bottom b a high a macrofauna 80 c c c c d behaviour 60 b b b d e c c e B. Riedel et al. 40 b b a a a b b 20 c c 0 Title Page 6750 1606 1297 5265 6653 6750 1606 1297 5265 6653 6750 1606 1297 5265 6653 6750 1606 1297 5265 6653

(e) posture atypical (f) shell orientation upright ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 Abstract Introduction 100 DO category (ml l-1) extended c a b b Conclusions References 80 out of shell

No. of observations (%) CI 95 No. c

60 c Tables Figures b c 40 b 20 c J I a a a a b 0 J I 6750 1606 1297 5265 6653 6750 1606 1297 5265 6653 ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 Back Close DO category (ml l-1) Full Screen / Esc Fig. A23. Paguristes eremita (N = 25). Printer-friendly Version

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14428 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion BGD 10, 14333–14438, 2013

Anoxia and macrofauna behaviour Fig A24 Pilumnus spinifer (N = 17) (a) visible (b) locomotion (c) body movement (d) location high/top B. Riedel et al. 100 e c d horizontal 80 vertical c Title Page 60 b a c b c 40 b a a a b Abstract Introduction a a b 20 a d d c Conclusions References e d c a 0 4995 993 760 3515 5619 840 487 600 3373 5608 840 487 600 3373 5608 840 487 600 3373 5608 Tables Figures No. of observations (%) CI 95 No. ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 DO category (ml l-1) J I

Fig. A24. Pilumnus spinifer (N = 17). J I

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14429 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion BGD 10, 14333–14438, 2013

Anoxia and macrofauna behaviour Fig A25 Pisidia longimana (N = 4) (a) visible (b) locomotion (c) body movement (d) location high/top B. Riedel et al. 100 e d horizontal 80 vertical a Title Page 60 c a a b b b ab c Abstract Introduction 40 a a b a c a b b 20 b Conclusions References c d d c d 0 1504 365 322 839 831 316 133 147 816 831 316 133 147 816 831 316 133 147 816 831 Tables Figures No. of observations (%) CI 95 No. ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 DO category (ml l-1) J I

Fig. A25. Pisidia longimana (N = 4). J I

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14430 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion BGD 10, 14333–14438, 2013 Fig A26 Ocnus planci (N = 4) (a) crown half open (b) crown closed (c) crown upward (d) crown downward 100 Anoxia and macrofauna 80 c b a a c behaviour 60 a a b ab B. Riedel et al. 40 b c b b 20 c a d d a a a 0 Title Page 808 278 242 1043 1269 808 278 242 1043 1269 808 278 242 1049 1896 808 278 242 1049 1896

(e) body elongation (f) body elongation (total) ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 Abstract Introduction 100 DO category (ml l-1) minor d Conclusions References 80 major c

No. of observations (%) CI 95 No. b 60 c Tables Figures b c b e 40 d J I 20 b a a a a a 0 J I 632 165 167 938 1162 808 278 242 1049 1896 ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 Back Close DO category (ml l-1) Full Screen / Esc Fig. A26. Ocnus planci (N = 4). Printer-friendly Version

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14431 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion BGD 10, 14333–14438, 2013

Anoxia and Fig A27 Psammechinus microtuberculatus (N = 17) macrofauna (a) visible (b) camou age (c) hori. locomotion behaviour 100 b B. Riedel et al. a minor 80 b c major c c a 60 d Title Page

40 d a Abstract Introduction b b 20 c Conclusions References a d e b b c d 0 Tables Figures 4939 1354 1090 3220 4339 2681 976 684 1666 2607 2528 942 653 1652 2593 No. of observations (%) CI 95 No. ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 J I DO category (ml l-1) J I

Fig. A27. Psammechinus microtuberculatus (N = 17). Back Close

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14432 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion BGD 10, 14333–14438, 2013

Anoxia and macrofauna behaviour Fig A28 Schizaster canaliferus (N = 22) (a) sediment bulging (b) visible (c) hori. locomotion (total) (d) hori. locomotion B. Riedel et al. 100 a minor d 80 major c Title Page 60 b ac a a Abstract Introduction 40 c c d c 20 b e b c Conclusions References a a a b 0 6373 1331 1193 4672 6616 6373 1331 1193 4672 6616 0 0 13 3023 6136 0 0 13 2841 3443 Tables Figures No. of observations (%) CI 95 No. ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 DO category (ml l-1) J I

Fig. A28. Schizaster canaliferus (N = 22). J I

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14433 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion BGD 10, 14333–14438, 2013

Anoxia and macrofauna behaviour Fig A29 Ophiothrix quinquemaculata (N = 28) (a) suspension feeding (b) arm tipping (c) arms down (d) locomotion B. Riedel et al. 100 a d e horizontal 80 vertical Title Page 60 b b

40 b c Abstract Introduction b c c b a 20 c a d d a b b c Conclusions References e a a e d 0 7549 1477 1398 5535 8373 7549 1477 1398 5535 8373 7549 1477 1398 5535 8373 8255 1944 1546 5609 8391 Tables Figures No. of observations (%) CI 95 No. ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 DO category (ml l-1) J I

Fig. A29. Ophiothrix quinquemaculata (N = 28). J I

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14434 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion BGD Fig A30 Ophiura spp. (N = 3) 10, 14333–14438, 2013

(a) visible (b) hori. lomotion Anoxia and 100 macrofauna c behaviour 80 B. Riedel et al. a a 60 Title Page ab 40 Abstract Introduction b b b Conclusions References 20 b a Tables Figures 0 940 249 174 372 492 0 30 26 53 385 J I No. of observations (%) CI 95 No. ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 J I Back Close DO category (ml l-1) Full Screen / Esc Fig. A30. Ophiura spp. (N = 3). Printer-friendly Version

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14435 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion BGD Fig A31 Amphiura chiajei (N = 10) 10, 14333–14438, 2013

(a) visible (b) hori. lomotion Anoxia and 100 macrofauna arms behaviour 80 emerged B. Riedel et al. 60 Title Page d c 40 c Abstract Introduction c b Conclusions References 20 b Tables Figures a a a a b a a 0 3056 984 848 2176 3198 0 0 19 427 1245 J I No. of observations (%) CI 95 No. ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 J I Back Close DO category (ml l-1) Full Screen / Esc Fig. A31. Amphiura chiajei (N = 10). Printer-friendly Version

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14436 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion BGD 10, 14333–14438, 2013 Fig A32 Microcosmus spp. (N = 10) (a) siphons open (b) siphons half open (c) siphons closed (d) body contraction 100 Anoxia and macrofauna 80 a a a a behaviour 60 b bc B. Riedel et al. 40 bc b c c a c a b b 20 b b b d a 0 Title Page 2781 608 496 2325 4237 2781 608 496 2325 4237 2781 608 496 2325 4237 2781 608 496 2325 4237

(e) drooping ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 Abstract Introduction 100 DO category (ml l-1) 80 Conclusions References

No. of observations (%) CI 95 No. 60 Tables Figures

40 J I 20 b a a a a 0 J I 2781 608 496 2325 4237 ≥2 <2 <1 <0.5 0 Back Close DO category (ml l-1) Full Screen / Esc Fig. A32. Microcosmus spp. (N = 10). Printer-friendly Version

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14437 icsinPpr|Dsuso ae icsinPpr|Dsuso ae | Paper Discussion | Paper Discussion | Paper Discussion | Paper Discussion BGD 10, 14333–14438, 2013 Fig A33 Phallusia mammilata (N = 9) (a) siphons open (b) siphons half open (c) siphons closed (d) body contraction Anoxia and 100 a ab a b macrofauna 80 c behaviour 60 c 40 B. Riedel et al. c c b b a b a a 20 a c a b a a 0 Title Page 2872 629 458 1500 2979 2872 629 458 1500 2979 2872 629 458 1500 2979 2872 629 458 1500 2979

(e) drooping ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 ≥2 <2 <1 <0.5 0 Abstract Introduction 100 DO category (ml l-1) 80 Conclusions References

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40

20 J I a a a a b 0 J I 2872 629 458 1500 2979 ≥2 <2 <1 <0.5 0 Back Close DO category (ml l-1) Full Screen / Esc Fig. A33. Phallusia mammilata (N = 9). Printer-friendly Version

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