1

PNAS Classification - BIOLOGICAL SCIENCES:

Larvae from afar colonize deep-sea hydrothermal vents after a

catastrophic eruption

Lauren S. Mullineauxa, Diane K. Adamsa,b, Susan W. Millsa, and Stace E. Beaulieua

aBiology Department, Woods Hole Oceanographic Institution, Woods Hole MA 02543

bCurrently at National Institutes of Health, National Institute of Dental and Craniofacial Research, Bethesda, MD 20982

Corresponding author:

Lauren Mullineaux MS 34, Department Woods Hole Oceanographic Institution Woods Hole, MA 02543 phone: 508 289-2898 fax: 508 457-2134 email: [email protected]

Manuscript information: 21 text pages, 4 figures; SI includes 2 figures and 3 tables 2

Abstract

The planktonic larval stage is a critical component of life history in marine benthic species because it confers the ability to disperse, potentially connecting remote populations and leading to colonization of new sites. Larval-mediated connectivity is particularly intriguing in deep-sea communities, where the habitat is patchy, transient and often separated by tens or hundreds of kilometers. A recent catastrophic eruption at vents near 9°50’N on the East Pacific Rise created a natural clearance experiment and provided an opportunity to study larval supply in the absence of local source populations. Previous field observations have suggested that established vent populations may retain larvae and be largely self-sustaining. If this hypothesis is correct, the removal of local populations should result in a dramatic change in the flux, and possibly species composition, of settling larvae. Fortuitously, monitoring of larval supply and colonization at the site had been established before the eruption and resumed shortly afterward. We detected a striking change in species composition of larvae and colonists after the eruption, most notably the appearance of the gastropod Ctenopelta porifera, an immigrant from possibly >300 km away, and the disappearance of a suite of species that formerly had been prominent. This switch demonstrates that larval supply can change markedly after removal of local source populations, enabling recolonization via immigrants from distant sites with different species composition. Population connectivity at this site appears to be temporally variable, depending not only on stochasticity in larval supply, but also on the presence of resident populations. 3

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Introduction

In marine benthic systems, dispersal in a planktonic larval stage influences the dynamics and spatial structure of populations and can be critical for regional persistence of species. It is informative to consider these systems in the framework of metapopulation theory (1) as a

balance between extinction and dispersal-mediated colonization. The extent to which a local marine population is open (i.e., the proportion of recruits that come from other locales) may increase its resilience to perturbation (2-3), but recruitment of progeny back into the natal site also contributes to persistence (4). Larval dispersal between deep-sea hydrothermal vent communities is an intriguing topic in this context because the habitat is spatially disjunct and populations are subject to local extinctions. A major challenge to solving questions of population openness (connectivity) in marine systems, however, is determining whether the source of each recruit is local or remote because the larvae are difficult to track. Consequently, fundamental questions about how vent populations persist and what physical and biological processes control their connectivity remain unresolved despite more than three decades of research (5).

Population genetic studies indicate that specific currents or topographic features may constitute barriers to dispersal between widely separated vents (6-9), but on scales of tens to even a hundred kilometers, populations of many species show little genetic differentiation (8, 10-11).

On these small scales, the lack of significant increase in genetic differentiation with separation distance has been interpreted to mean that larvae are supplied in a well-mixed pool (12).

Although larvae of some vent species have the potential to disperse long distances (13-14), larval patchiness in the field (15-16), enhanced larval supply directly downstream of source 4

populations (17), and hydrodynamic analyses (18) suggest that larval retention may occur near natal sites. It is possible that these populations are largely self-sustaining on ecological time

scales, and maintain high apparent genetic connectivity through infrequent exchange of

individuals over long periods.

A recent catastrophic eruption at vents near 9°50’N on the East Pacific Rise (EPR) created a natural clearance experiment and allowed us to study larval connectivity after the removal of local populations. Such perturbations are common along the fast-spreading EPR, where tectonic and magmatic events cause vents to open and close on decadal time scales (19). Since the discovery of vents at this site, researchers have detected two major eruptions; one in 1991 (20) and a second (the subject of the present study) in 2006 (21). The latter eruption introduced a major perturbation into local vent communities. New lava emerged between 9°46’ to 9°56’N and reached as far as 2 km off axis (22) (Fig. 1) paving over existing vent communities. The precise timing of lava extrusion is uncertain; estimates vary from late 2005 to January 2006 (21).

Although the lava eradicated invertebrate communities, it did not plug all the vents, and hydrothermal fluids (on which the communities depend) continued to flow from many of the orifices established before the eruption. One community survived at the southern margin of the eruption (V-vent at 9°47’N); the species composition there did not change detectably after the eruption (authors’ visual surveys) and was similar to pre-eruption faunas at the paved-over vents.

To the north, a single colonized vent has been reported at 10°08’N (23), but its status at the time of the eruption is unknown. No other colonized vents are known between 9°56’N and the

Clipperton Transform Fault (10°13’N).

This large-scale removal of vent populations provided us with an opportunity to address questions about larval supply and recolonization at vents where initially there was no local larval 5

source. This was possible only because we had been monitoring larval supply and colonization

near 9°50’N prior to the eruption (24), and were able to mobilize quickly afterward to resume

sampling. If larvae were typically supplied to these EPR vents in a well-mixed, time-invariant larval pool (12), we would expect little influence of the eruption on larval supply, and early recolonization to be determined primarily by responses to conditions in the benthic environment.

If instead, local populations had been an important contributor to supply (17), we would expect a reduction in larval abundance after the eruption and distinct differences in species composition, depending on which remote source populations contributed immigrants. This altered pool of larval immigrants would constitute the pioneer colonists and potentially direct the trajectory of subsequent succession. Our specific objectives in this study were to determine whether larval supply changed significantly after the eruption and to explore the effects of this supply on recolonization.

Results

The species composition of larvae supplied to vents after the eruption differed markedly from that before (Fig. 2; Table S1). Although supply of the abundant larval gastropod species varied substantially between cup intervals, all but one (Gorgoleptis emarginatus) arrived at a

consistently different rate after the eruption than before (P<0.05, MANOVA and ANOVA,

Systat v. 11; Table S2). Supply of Cyathermia naticoides, Lepetodrilus spp., Gorgoleptis

spiralis and Bathymargarites symplector declined significantly after the eruption, despite the continued presence of potential source populations within 6 km to the south at V-vent. In contrast, Ctenopelta porifera, which had been virtually absent before the eruption (only a single individual in the 2004-2005 trap samples, and one in a 2004 pump sample (25)) was supplied in 6

significantly higher numbers afterward. During a few intervals of the larval sampling series, the

change in supply of some species over several weeks was as high, or higher, than the difference

in mean supply between pre- and post-eruption. When such a change occurs simultaneously

across multiple species (e.g., the decrease in supply observed after pre-eruption interval 11, or

after post-eruption interval 1; Fig. 2), it is likely associated with mesoscale hydrodynamic

transport processes (24) that are unrelated to the eruption.

The post-eruption change was detectable in larvae of rare species as well; 14 of 27 larval

gastropod taxa present at East Wall before the eruption were not found at P-vent afterward

(Table S1). These differences in species composition are apparent in a nonmetric

multidimensional scaling analysis (nMDS; Systat v. 11) (Fig. 3a). Other groups also showed

large changes in supply after the eruption (e.g., an increase in crabs Bythograea microps and B.

thermydron; Table S1).

Species composition of colonists also changed distinctly after the eruption. Most

surprising was the appearance of Ctenopelta porifera (Fig. 4a) because it had never been

reported before in the from this segment of the EPR. The limpet Lepetodrilus tevnianus

also was prominent in the hot environment after the eruption, whereas previously common

species including Lepetodrilus elevatus, L. pustulosus, and Rhynchopelta concentrica were

absent. The temperatures at P-vent (post-eruption) were similar to those at Tica (pre-eruption),

so elevated temperatures do not appear to be responsible for these differences, although it is

possible that chemistry differed. On surfaces in the warm environment, L. tevnianus was

prominent after the eruption (Fig. 4b) while diverse species present before the eruption

(Bathymargarites symplector, L. ovalis, L. pustulosus, Clypeosectus delectus, Gorgoleptis spiralis) had disappeared. The distinct differences in overall species composition, including rare 7

species, before and after the eruption are apparent in nMDS analysis of gastropod colonists (Fig.

3b).

The dramatic increase in larval supply of Ctenopelta porifera after the eruption coincided

with its appearance as a colonist (Fig. 4). Other species (e.g., B. symplector, C. naticoides, G.

spiralis, R. concentrica), also showed a post-eruption change in larval supply that corresponded with change in colonist abundance (Tables S1 and S3). Unfortunately, we could not tell whether changes in larvae of individual lepetodrilid species (Lepetodrilus spp.) coincided with changes in the associated colonists because the larvae are not morphologically distinguishable at the species level. We suspect that larvae in this group predominantly represented pre-disturbance species (L. elevatus, L. pustulosus, L. ovalis) before the eruption and the post-disturbance pioneer (L. tevnianus) afterward, but molecular genetic identifications are needed for confirmation.

Discussion

The marked change in species composition of larval supply and colonists after the 2005-

2006 eruption is consistent with a scenario in which pioneer species from remote populations were able to colonize successfully at 9°50’N only after the resident populations (and their larvae) had been eliminated. The observed changes are not consistent with a model of recolonization via a well-mixed larval pool, from which larval supply would be relatively unaffected by elimination of local populations. Clearly, the disturbance strongly affected larval supply in the local region.

Surprisingly, the source of pioneer colonists did not appear to be the nearest established communities, such as V-vent (at 9°47’N) or other sites to the south whose faunal composition resembled the pre-eruption communities at 9°50’N. Instead, at least one prominent pioneer 8

species, Ctenopelta porifera, arrived from possibly > 300 km away, where vents at 13°N host the

only known populations.

The post-eruption change in larvae and colonists could have developed through two

different mechanisms, initiated either by altered larval supply or settlement responses to the

altered environmental conditions. The first case might be expected if larval supply in the

disturbed region declined precipitously directly after the eruption. This ‘larval vacuum’, caused

by elimination of local populations, could open the sites to settlement of highly dispersive, but

perhaps competitively inferior, immigrant species from remote regions that typically are not able

to infiltrate established pre-eruption communities. The particular species of pioneers depends on

which larvae are available in the interval shortly after the eruption, as influenced by time-variant

transport processes (17), or spawning cycles (26). This type of post-disturbance colonization

scenario, contingent on supply of new pioneers, has been observed in a variety of marine and

terrestrial environments (27-29). Our larval flux measurements, initiated roughly six months

after the main seismic event in January 2006, and possibly even longer after the main lava

extrusion, did not measure supply in the first few months after the eruption. A pilot set of larval

samples (Fig. S1) collected in the eruption region during May to June 2006 did reveal very low

fluxes (averaging <1 day-1), but those results must be interpreted carefully because the collectors were located several hundred meters away from vents, where larval abundances are known to be reduced (16). Nevertheless, we think the altered supply scenario is a likely one, given prior evidence of local larval supply at this site (17), and the observations 6 months after the eruption of reduced fluxes of many pre-disturbance species.

An alternative possibility is that environmental conditions changed so drastically after the eruption that pre-disturbance species were not able to settle and survive, even if they were 9

supplied as larvae. In this case, larval supply may or may not have declined directly after the

eruption, but only species adapted to the new thermal or chemical conditions were able to

colonize as pioneers. The chemical composition of hydrothermal fluids at some EPR vent sites

are known to have changed after the eruption (30) and may have altered habitat suitability for select species. The structural habitat also changed, with Tevnia jerichonana replacing Riftia pachyptila as the main foundation tubeworm species, possibly facilitating establishment of associated gastropod species such as L. tevnianus. Environmental conditions at vents are known to correlate with distribution of some species (31-32), and with faunal changes over time (33).

Investigations of species’ tolerances to specific thermal and chemical habitats in the post- eruption sites are underway, but it is not yet known whether the gastropod species that were so prominent before the eruption are able to tolerate the post-eruption conditions. It is quite possible that altered larval supply and environmental tolerances both contributed to the faunal changes observed after the eruption.

The increase in larval supply of post-disturbance species after the eruption suggests that once the pioneers became established and reproductively mature they bolstered overall local larval supply to near pre-eruption levels. Although no broad survey of reproductive maturity was attempted, many of the gastropod colonists collected in November 2006 were larger than the minimum size of reproductive maturity, and mature gonads were observed in C. porifera and L. tevnianus (34).

Continued observations of the vent communities will show whether the post-eruption change in species composition persists and results in an ecological regime shift or is simply an early stage in succession that will transition back to the pre-eruption state. If local populations dominate larval supply, the established species may pre-empt occasional immigrants of other 10

species from remote locales, or from neighboring sites to the south with pre-disturbance faunas.

Alternatively, if fluid chemical conditions revert to pre-eruption levels or if pioneers make the habitat more suitable for other species, the faunal communities may develop through a successional sequence as immigrants outcompete the initial colonists. Successional observations from the previous (1991) eruption cycle described a transition in the large, structure-forming species from the tubeworms T. jerichonana to R. pachyptila, and eventually to the mussel

Bathymodiolus thermophilus (33) that was attributed to changes in environmental conditions.

Prior to the 2006 eruption, most 9°50’N vent sites hosted R. pachyptila, indicating a mid-to-late stage of succession (16). Although changes in gastropod species composition also occur during succession at vents (35-36), no clear sequence of species replacement has been observed, and the pioneer gastropod colonists after the 1991 eruption did not include C. porifera or L. tevnianus

(37). Deterministic succession is found in terrestrial meadows and temperate forests (28, 38), both quite stable systems where disturbance time scales are long relative to species’ generation times. In contrast, the EPR vents are a system where disturbance occurs at intervals approaching species’ generation times. The inclusion of larval measurements through the 2006 eruption will allow future investigation of whether larval/propagule availability influences succession at vents, as it does in many other frequently disturbed marine and terrestrial communities (27, 39-40).

The extensive, coordinated history of observations in the 9°50’N EPR region and the ongoing monitoring there make it a truly unique site for studies of ecosystem response to disturbance.

Our results show that vent populations on the EPR are, as expected, connected by larval dispersal, but specific populations cannot be consistently characterized as open or closed. Once a catastrophic disturbance eliminates the community at a vent, the site becomes open to colonization via larvae from remote populations, possibly as far as 300 km away. After the site 11 has become colonized, however, larvae from the local populations appear to dominate as potential recruits. This alternation between open and closed condition is quite different than the situation in more stable marine environments where inter-disturbance period is long compared to species’ generation times, and connectivity is more likely to depend on population growth rates and transport processes than disturbance.

Although the magnitude of connectivity at these vents appears to depend strongly on the frequency of disturbance, the species composition of pioneer larvae is likely subject to temporally variable currents, as demonstrated for coastal habitats (41). One consequence of stochasticity in larval supply, and episodic opening of vent sites to new colonists, is the potential for occasional exchange between far distant sites, as was observed for C. porifera in the present study. Such an exchange could explain the high genetic connectivity reported for many vent species (12, 42), even in cases where most larvae are retained locally between disturbances.

Studies of immigration and succession at transient, geographically separated, vents on the

EPR contribute to our understanding of vent systems in a metapopulation context (43), as they have in terrestrial volcanic systems (44-45). In these highly disturbed systems, the important question may not be whether populations are open or closed (46), but instead how often they become open and for how long. This temporal variation in connectivity has important implications for predicting effects of natural perturbations, or anthropogenic impacts such as seafloor mineral mining, ecotourism, or bioprospecting.

Materials and Methods

Larvae were collected in McLane PARFLUX Mark 78H-21 time-series sediment traps with a 0.5 m2 collecting area. Particles dropped into collection cups filled with 20% 12 dimethylsulfoxide in saturated salt solution (47) as a preservative. Pre-eruption traps were positioned into the axial trough near vents by lowering on a wire from shipboard into a seafloor navigation network (17). These traps sampled at East Wall and Choo Choo vents (Fig. 1) on 7- day intervals between Nov. 25, 2004 and April 21, 2005 (24). Following the eruption, a rapid- response cruise was launched in July 2006 aboard the R/V Atlantis. A trap was positioned near

P-vent by submersible (Fig. 1), sampling on a 6-day interval between July 1 and Nov. 4, 2006.

P-vent was selected as a nearby alternative to East Wall, which was no longer venting vigorously, and Choo Choo, which had shut down. On recovery, samples from the traps were maintained at ~4°C until the larvae (molluscs, polychaetes and crustaceans) were sorted and identified morphologically (48) under a dissecting microscope to the lowest taxonomic level possible (e.g., species level for most gastropods). The traps collect larvae that are swimming or sinking downward, and flux into the trap is considered an indicator of larval supply to the benthos (25, 49).

The East Wall, Choo Choo and P-vent traps were located directly in the axial trough within 50 m of active vents. Three other traps were deployed after the eruption near Tica and

Bio9 (starting May 16 2006 at 2-day intervals) and Ty/Io (starting Jul. 1 2006 at 6-day intervals)

(Fig. 1), but lacked precise navigation and were positioned out of the trough. Larvae from these traps were not used in primary analyses because larval abundance may be reduced outside the trough (16).

Colonists (larvae that had settled and metamorphosed) were collected on experimental surfaces deployed by the submersible Alvin in vent sites for 4 to 5 mo durations. The surfaces were placed into two distinct environments in inhabited, diffuse-flow vents. The ‘hot’ environment was characterized by the presence of tubeworms, vigorous flow, and maximum 13

temperatures up to 30°C. The ‘warm’ environment lacked tubeworms, and had moderate flow

with temperatures <7°C. These environments correspond respectively to the vestimentiferan and

bivalve/suspension-feeder zones of previous studies at this site (36). In the 9°50’N region,

species composition at different vents typically is similar within a zone, but varies substantially

between zones (33, 36, 50). Surfaces used to quantify pre-eruption colonists were selected from a larger sample set from this region of the EPR (36, 50-51) to match as closely as possible the deployment intervals and environmental and faunal characteristics of the post-eruption sites.

They included surfaces placed at Worm Hole vent from November 1994 to April 1995 in hot

(temperatures at surfaces of 1.9 to 10.9°C) and warm (1.8 to 2.1°C) environments, and at Tica vent from December 1999 to May 2000 in hot (18.0 to 26.3°C) environments (Fig. 1). Neither site supported abundant mussels, which were absent in post-eruption communities and are known to influence colonization (52). Species abundances in the different environments from these pre-eruption colonization samples are representative of those in the larger sample set.

Post-eruption surfaces were deployed between July and November 2006 in the hot (23.2 to

26.7°C) environment at P-vent and warm (2.2 to 6.5°C) environment at a site near Ty/Io vent.

These sites were selected because they were venting vigorously and were sufficiently large to accommodate replicate experimental surfaces; Worm Hole had shut down prior to the eruption and Tica was not visited on the eruption-response cruise due to time limitations. For all colonization surfaces, the thermal environment was measured with a temperature probe on deployment and recovery at the base of the surface. On recovery, they were placed in individual collection compartments for transport back to the ship. On shipboard, surfaces and their attached colonists were preserved in 80% ethanol, as were any detached individuals from the compartment retained on a 63-µm sieve. In the laboratory, each surface was examined under a 14 dissecting microscope and all metazoan colonists (including detached individuals > 1 mm) were enumerated and identified. Gastropods only were used in subsequent analyses because methods of identification and quantification were consistent across all samples for those species.

The colonization surfaces used prior to the eruption were basalt blocks, 10 cm on a side.

Those used after the eruption were ‘sandwiches’ of six Lexan plastic plates, each 0.64 cm thick and separated from each other by 0.95 cm to provide additional surface area within a 1000 cm3 volume. Many vent species settle onto plastic surfaces (53), so we did not expect this change in surface composition to greatly alter species composition of colonists, especially over a period of months. To evaluate this assumption, we compared gastropod colonists between basalt blocks and Lexan sandwiches in a simultaneous, later deployment (Nov 2006 to Jan 2007) at Tica vent.

Non-metric multidimensional scaling (nMDS) analysis showed that dissimilarities based on species composition were no greater between surface types than within a type and that composition on both blocks and sandwiches was similar to that on sandwiches deployed earlier in comparable thermal habitat (Fig. S2). However, the surface area of sandwiches was more than twice the area of basalt blocks; since this difference potentially influences absolute abundance of colonists, we compare relative abundances between pre- and post-eruption deployments.

Larval supply was compared between pre- and post-eruption periods using MANOVA followed by univariate ANOVA (Systat v. 11; Table S2) for the 6 most abundant species at either site that were also found on colonization surfaces. Since sequential intervals in the time series were used as replicates, autocorrelation analysis (Matlab 7.1) was used to evaluate independence. Significant autocorrelation (P < 0.05) with a 1-step lag was detected in at least one record for three taxa (C. naticoides, G. spiralis, and G. emarginatus) and autocorrelation with a 2-step lag was detected for Lepetodrilus spp.. In each of these cases, when the ANOVA 15 was repeated with subsampled records to avoid autocorrelation (every second or every third sample interval as appropriate) no changes in significance were found (P < 0.05 level).

Differences in community composition were examined with nMDS of larval abundance in trap samples (Systat v. 11), using Pearson correlations of 4th root transformed values to emphasize rare taxa. Polychaetes were not included because their preservation was poor in some samples.

For visual clarity, only the East Wall samples were plotted from the pre-eruption collections

(when Choo Choo samples are added, they cluster near East Wall positions). Colonist community composition (gastropods only) was examined similarly with nMDS.

ACKNOWLEDGMENTS. We are grateful for help at sea from K. Buckman, D. Fornari,, A.

Fusaro, I. Garcia Berdeal, B. Govenar, B. Hogue, R. Jackson, C. Strasser, T. Shank, S. Worrilow, and to the Captains and crew, Alvin group, and Chief Scientists (M. Lilley, C. Vetriani, K. Von

Damm, A. Thurnherr) during Atlantis cruises AT11-20, 11-26, 15-06 and 15-12, and the

Captain, crew and Chief Scientist (J. Cowen) of the New Horizon rapid response cruise. S. A.

Soule provided a base topographic map of the eruption area. Principal investigators in the

LADDER project (W. Lavelle, J. Ledwell, D. McGillicuddy, A. Thurnherr) were instrumental in facilitating this project and provided input during numerous discussions. Support was provided by NSF grants OCE-969105, OCE-9712233, and OCE-0424953), WHOI grants from DOEI and the Venture Fund, a NDSEG graduate fellowship to DA, and the WHOI Jannasch Chair for Excellence in to LM.

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22

Figure Legends

Figure 1. Locations of vents and sample sites on the East Pacific Rise in the region of the

eruption. Symbols designate vent sites (yellow circles), sediment traps (inverted triangles) and

colonization experiments (squares) (blue = pre-eruption, red = post-eruption). Blue line outlines the extent of lava extruded in the 2005 – 2006 eruption (22). Bathymetry of ridge (54) is contoured at 10 m intervals. Map courtesy of S. A. Soule.

Figure 2. Larval supply measured in sediment traps. Traps sampled before the eruption (Nov.

25, 2004 to Apr. 21, 2005 at 7-day intervals; blue bars) near East Wall vent and after (Jul. 1 to

Nov. 4, 2006; 6-day intervals; red bars) near P-vent. Supply (daily downward flux of larvae into

0.5m2 trap opening) displayed for the six most abundant species/groups at either site that also

were found as colonists: a) Cyathermia naticoides, b) Lepetodrilus spp; c) Gorgoleptis spiralis, d) Bathymargarites symplector, e) Gorgoleptis emarginatus, f) Ctenopelta porifera. Mean flux of each species except G. emarginatus changed significantly (P<0.05, MANOVA and ANOVA;

Table S2) after the eruption. Larval individuals of the five described lepetodrilid species in this region (L. elevatus, L. pustulosus, L. ovalis, L. cristatus and L. tevnianus) were not distinguishable morphologically.

Figure 3. Non-metric multidimensional scaling analysis (nMDS) of species composition of larvae and colonists. The proximity of samples corresponds to the similarity in their species composition. Analysis conducted on Pearson correlation of fourth-root transformed abundance. a) Larvae (excluding polychaetes) in sediment traps before (blue dots) and after (red dots) eruption; label designates site (E = East Wall, P = P-vent) and cup interval; Kruskal stress = 0.15. b) Colonists (gastropods only) on blocks before the eruption (blue dots) and on 23

sandwiches after (red dots); label designates site (WH = Worm Hole, TA = Tica; TY = Ty/Io, P = P-vent), environment (H = hot, W = warm) and replicate; Kruskal stress = 0.073. Mean species or species-group abundances listed in Table S3.

Figure 4. Species composition of vent gastropod colonists and larvae. All gastropods were

identified to species except larval and small juvenile Lepetodrilus, which could only be identified

to . Jagged line separates pre- (left) and post-eruption (right) samples. a) Colonists in hot vent environment before eruption at Worm Hole and Tica vents and after eruption at P-vent.

Values are average relative abundances (+/- standard error; n=3) of 7 most common species or species groups (those >2% of all vent gastropods at any of 3 sites). b) Colonists in warm vent environment before eruption at Worm Hole and after eruption near Ty/Io vent. Values are average relative abundances (+/- standard error; n=3) of six most abundant species/groups (those

>2% of all vent gastropods at either of two sites). c) Larval supply in sediment traps before eruption at East Wall and Choo Choo vents and after eruption at P-vent. Values are average relative abundances (+/- standard error; n=21) of 6 most common species/groups that are also found as colonists. -104 18' -104 16'

km -2500 9 56' 0 1 2 -2550

-2600

-2650 9 54' -2700

-2750

-2800

9 52'

East Wall Tica Bio9 P-vent 9 50' Ty/Io Choo Choo

Worm Hole

9 48'

V-vent

9 46' Pre-Eruption Post-Eruption 30 30 Cyathermia naticoides Cyathermia naticoides 20 20

10 10

0 0 0 5 10 15 20 0 5 10 15 20

Lepetodrilus spp. Lepetodrilus spp. 10 10

5 5

0 0 0 5 10 15 20 0 5 10 15 20 3 3 Gorgoleptis spiralis Gorgoleptis spiralis 2 2

1 1

0 0 0 5 10 15 20 0 5 10 15 20 3 3 Bathymargarites symplector Bathymargarites symplector Larvae (0.5 m d)   2 2

1 1

0 0 0 5 10 15 20 0 5 10 15 20

30 Gorgoleptis emarginatus 30 Gorgoleptis emarginatus

20 20

10 10

0 0 0 5 10 15 20 0 5 10 15 20 6 6 Ctenopelta porifera Ctenopelta porifera 4 4

2 2

0 0 0 5 10 15 20 0 5 10 15 20 Interval 2 A Larvae

1 P2 P1 P11 E9 P16 P6 P18 P20 E17E11 P15 P3 P12 E1 E10 E14 P17 P10 E15 E5 E7 0 P19 P13 E21E3 E6 P4 P5 E4 E2 E20 E16 E8 P14 E12 Dimension-2 P8 E13 E18 P9 E19 -1 P7 P21

-2 -2 -1 0 1 2 Dimension-1

2 B Colonists

1 WH_W2 TY_W1 WH_W3 TY_W2 TY_W3 WH_H1 WH_H2 0 WH_W2 P_H3 WH_H1 P_H2 TA_H1 Dimension-2 TA_H2 P_H1 TA_H3 -1

-2 -2 -1 0 1 2 Dimension-1 Pre-Eruption Post-Eruption

1 L. elevatus A Colonists-Hot B. symplector 0.8 L.pustulosus L. ovalis 0.6 R. concentrica C.delectus G. spiralis 0.4

Frequency C. naticoides Lepetodrilus spp. 0.2 L. tevnianus C. porifera 0 Worm Hole Tica P-vent

1 B Colonists-Warm 0.8

0.6

0.4 Frequency

0.2

0 Worm Hole Ty/Io

1 C Larvae 0.8

0.6

0.4 Frequency

0.2

0 East Wall Choo Choo P-vent 24

Supplementary Materials

Figure Captions

Figure S1. Total supply of vent larvae measured in all pre- and post-eruption sediment traps.

Supply (daily downward flux of larvae into 0.5m2 trap opening) includes all individuals except

polychaetes that unequivocally (based on identification to species or genus) or probably (based on identification to family) belong to vent species. Traps sampling before the eruption (blue bars) were located at East Wall and Choo Choo vents (starting Nov. 25, 2004 at 7-day intervals),

those sampling afterward (red bars) were near Tica and Bio9 (starting May 16 2006 at 2-day

intervals, pooled here into 6-day intervals) and P-vent and Ty/Io (starting Jul. 1 2006 at 6-day

intervals). Ty/Io sampling was curtailed after the 9th cup because a large gelatinous organism

clogged the cup-changer mechanism. Locations of sites are shown in Fig. 1. The East Wall,

Choo Choo and P-vent traps were located directly in the axial trough within 50 m of active vents.

Precise navigated placement was not possible for the other traps which were located out of the

trough and > 50 m from the closest vents. Prior work has shown that abundance of vent larvae

typically decreases away from the axial trough (16). Trap location may be in part responsible for

the reduced fluxes observed at Tica and Bio9, but if that were the sole cause we would expect

comparable reduction at Ty/Io. Fluxes at Ty/Io were substantially lower than at P-vent, but not

as low as at Tica and Bio9. Therefore we suspect that the reduced fluxes observed at Tica and

Bio9 reflect both an overall reduction in larval supply following the eruption, and the placement

of those traps outside the trough.

Figure S2. Non-metric multidimensional scaling analysis (nMDS) of species composition of

gastropod colonists, comparing blocks and sandwiches. Analysis conducted on Pearson

correlation of fourth-root transformed abundance of >1mm individuals in sieve samples. The 25 proximity of samples corresponds to the similarity in their species composition. Colonists on blocks deployed before eruption are designated by blue filled squares, those on sandwiches deployed shortly after eruption (July to Nov. 2006) are in red striped squares, and those deployed slightly later (Nov. 2006 to Jan 2007) specifically to compare blocks and sandwiches are in yellow filled squares and striped squares, respectively. Label designates site (WH = Worm Hole,

TA = Tica; TY = Ty/Io, P = P-vent) and environment (H = hot, W = warm). Kruskal stress =

0.084. 80 East Wall Tica P vent 60

40

Larvae/day 20

0 0 5 10 15 20 0 5 0 5 10 15 20 80 Choo Choo Bio9 Ty/Io 60

40

Larvae/day 20

0 0 5 10 15 20 0 5 0 5 10 Interval 2 Colonists

WH_W 1 WH_W TA_W TY_W WH_H TA_W TY_W TA_W WH_H TA_W TA_W TY_W WH_H 0 TA_W WH_W

P_H TA_H

Dimension-2 TA_H P_H -1 P_H

-2 -2 -1 0 1 2 Dimension-1 26

Table S1. Larval supply in sediment traps.

East Wall Choo Choo Tica Bio9 P-vent Ty/Io 2004-2005 2004-2005 May-Jun 2006 May-Jun 2006 Jul-Oct 2006 Jul-Sep 2006 x se x se x se x se x se x se Taxon (0.5 m2 d)-1 (0.5 m2 d)-1 (0.5 m2 d)-1 (0.5 m2 d)-1 (0.5 m2 d)-1 (0.5 m2 d)-1 - Gastropoda Bathymargarites symplector 0.55 0.08 0.61 0.14 0 0 0.05 0.05 0.25 0.08 0.04 0.04 Clypeosectus delectus 0.20 0.04 0.09 0.03 0 0 0 0 0 0 0 0 Ctenopelta porifera 0.01 0.01 0 0 0.43 0.15 0.10 0.07 0.56 0.27 0.19 0.11 Cyathermia naticoides 9.56 1.75 7.01 2.40 0.14 0.10 0.14 0.08 1.11 0.55 0.37 0.17 Echinopelta fistulosa 0.18 0.05 0.01 0.01 0 0 0 0 0.02 0.02 0.04 0.04 Eulepetopsis vitrea 0.37 0.09 0.17 0.06 0 0 0.10 0.07 0 0 0.04 0.04 Gorgoleptis emarginatus 1.56 0.16 0.59 0.11 0.38 0.21 0.19 0.11 3.67 1.45 0.63 0.28 Gorgoleptis spiralis 0.65 0.14 0.29 0.09 0 0 0 0 0.06 0.03 0.04 0.04 Gorgoleptis sp. 3 0 0 0.01 0.01 0 0 0 0 0.03 0.03 0 0 Laeviphitus sp. 8.08 1.48 0.21 0.06 0.05 0.05 0.14 0.08 7.52 1.13 0.44 0.16 Lepetodrilus spp. 4.76 0.70 3.48 0.72 0.05 0.05 0.19 0.09 1.14 0.39 0.41 0.12 Lepetodrilus -like 190 µm 0.05 0.03 0 0 0 0 0 0 0 0 0 0 Lirapex granularis 0.03 0.02 0 0 0 0 0 0 0 0 0 0 Lirapex sp. 0.01 0.01 0 0 0 0 0 0 0 0 0 0 Melanodrymia aurantiaca 0.10 0.03 0 0 0 0 0 0 0.02 0.02 0 0 Melanodrymia galeronae 0.03 0.02 0.01 0.01 0 0 0 0 0 0 0 0 Melanodrymia ? sp. A 0 0 0 0 0 0 0 0 0.02 0.02 0 0 Neomphalid sp. B 0 0 0 0 0 0 0 0 0.08 0.04 0.04 0.04 Neomphalid sp. W 0.07 0.03 0.03 0.02 0 0 0 0 0.02 0.02 0 0 Neomphalid sp. 5 2.88 0.40 1.86 0.49 0.05 0.05 0.10 0.07 1.06 0.21 0.26 0.22 Neomphalid 260 µm 0.07 0.03 0.03 0.02 0 0 0 0 0 0 0 0 Neomphalid 290 µm 0.01 0.01 0.01 0.01 0 0 0 0 0 0 0 0 Neomphalus fretterae 0.41 0.10 0.22 0.06 0 0 0 0 0 0 0.04 0.04 Neolepetopsis sp. 0.01 0.01 0 0 0 0 0 0 0 0 0 0 Pachydermia laevis 0.10 0.03 0.07 0.03 0 0 0 0 0 0 0 0 Peltospirid species 0.80 0.12 0.03 0.02 0 0 0.10 0.07 0.19 0.10 0 0 Phymorhynchus sp. 0.01 0.01 0.01 0.01 0 0 0 0 0 0 0 0 Rhynchopelta concentrica 0.32 0.08 0.10 0.04 0 0 0 0 0 0 0.11 0.06 Gastropod, benthic sp. A 6.36 0.74 3.03 0.80 0 0 0 0 0.27 0.06 0 0 Gastropod, pointy apex 0.50 0.12 0.33 0.11 0 0 0 0 0 0 0.15 0.11 Mollusca - Bivalvia Bathymodiolus thermophilus 0 0 0 0 0 0 0.05 0.05 0 0 0 0 Bathypecten vulcani 0 0 0 0 0 0 0.10 0.06 0.02 0.01 0.11 0.07 Crustacea Bythograea microps 0.05 0.02 0.03 0.01 0.10 0.06 0.10 0.04 1.58 0.60 0.24 0.08 Bythograea thermydron 0.04 0.02 0.07 0.02 0.12 0.06 0.07 0.04 0.37 0.17 0.33 0.14

Mean ( x ) and standard error (se) of daily flux, n = 21 samples except at Ty/Io where n=9. Taxa are unequivocally

(based on identification to species or genus) or probably (based on identification to family or other diagnostic taxon) vent inhabitants. Polychaeta not included due to poor preservation in some samples 27

Table S2. Univariate ANOVA of larval supply.

Taxon F P

Bathymargarites symplector 8.40 0.006 Ctenopelta porifera 5.50 0.024 Cyathermia naticoides 52.24 < 0.001 Gorgoleptis emarginatus 1.55 0.220 Gorgoleptis spiralis 20.91 < 0.001 Lepetodrilus spp. 31.25 < 0.001

Supply compared before the eruption (Nov 2004- Dec 2005 at East Wall) and after (July to Nov 2006 at P-vent) (df

= 1, 40). Species were 6 most abundant in either record, also observed as colonists. MANOVA showed Wilks' λ =

0.219, significant at P < 0.001 (F = 22.85, df = 6, 35).

28

Table S3. Gastropod colonist abundance before and after eruption.

Pre-Eruption Post-Eruption Worm Hole Tica Worm Hole P-vent Ty/Io Hot Hot Warm Hot Warm Taxon x se x se x se x se x se

Bathymargarites symplector 0 0 0 0 0.3 0.3 0 0 0 0 Clypeosectus delectus 0.3 0.3 0 0 7.7 0.3 0 0 1.3 1.3 Ctenopelta porifera 0 0 0 0 0 0 25.0 10.4 0.3 0.3 Cyathermia naticoides 30.0 30.0 9.0 5.5 0 0 2.7 1.7 0.3 0.3 Eulepetopsis vitrea 0.3 0.3 0 0 4.3 3.8 0 0 3.0 2.5 Gorgoleptis emarginatus 0 0 0 0 0 0 0 0 0.3 0.3 Gorgoleptis spiralis 0 0 0 0 15.3 9.9 0 0 1.0 0.6 Lepetodrilus elevatus 493.0 278.3 24.3 4.7 0 0 0 0 0.7 0.7 Lepetodrilus ovalis 1.3 1.3 0 0 26.0 25.0 0 0 0 0 Lepetodrilus pustulosus 98.0 56.2 6.7 3.3 0 0 0 0 0 0 Lepetodrilus tevnianus 0 0 0 0 0 0 7.3 6.8 1083.7 357.9 Lepetodrilus spp. 74.7 38.8 0 0 25.3 17.8 1.7 0.9 1624.3 562.3 Neomphalid sp. W 0 0 0 0 0 0 0 0 0.3 0.3 Neomphalus fretterae 0 0 0 0 0 0 0 0 0.3 0.3 Nodopelta rigneae 0 0 0.3 0.3 0 0 0 0 0 0 Pachydermia laevis 0 0 0 0 0 0 0 0 0.7 0.7 Peltospira delicata 0 0 0 0 0 0 0.3 0.3 0 0 Rhynchopelta concentrica 0 0 6.7 3.2 0 0 0 0 0.3 0.3 Gastropod, pointy apex 0 0 0 0 0 0 0 0 4.7 4.7

Number of individuals ( x = mean, se = standard error) on blocks at Worm Hole and Tica, and on sandwiches at P- vent and Ty/Io, placed in hot or warm habitat.