**2. Methods**

Over 100 scuba dives were conducted from 2007 to 2018 at the inshore Defence Island bioherm (**Figure 1**) in Howe Sound, British Columbia (49°34.66 N, 123°16.41 W). Difficulty in relating video frames to individually identifiable sponges led to installation of 12 bar-coded locator stakes [5] in 2014 that also had a mark to indicate the depth of the reef substrate at the time of installation. Growth and death of sponges near these marker stakes were monitored with video recordings. All photographs and videos used for analysis in this chapter include one of these locator stakes or some other landmarks such as a temperature logger, a sonde oceanographic buoy, or a pair of pipes called the "pipe vee" which had been installed in 2009 for camera positioning.

Divers with the Underwater Council of British Columbia inserted temperature loggers in the seabed of various sponge reefs in Howe Sound from 2014 through 2018, including the present site. Loggers were replaced at intervals so that most sites had nearly continuous records. The observations spanned El Niño (2015/2016) and La Niña (2016/2017, 2017/2018) climate events. Beginning in May 2014, Thermochron® iButton temperature loggers (version DS1921Z-F5; accuracy = ±1.0°C) were deployed at six sponge reefs in Howe Sound, data from four of which are presented here. Loggers were placed in among the sponges using PVC pipe holders and left there for up to 1 year, logging at intervals of either 2, 3, or 4 hours. Loggers were collected and data downloaded as often as possible, though weather and boating restricted the collection of some loggers such that gaps in data occurred. Two of the six reefs had significant gaps in data so are not presented here.

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*Formation, Persistence, and Recovery of Glass Sponge Reefs: A Case Study*

Data collected from 2014 to 2018 were summarized as an average temperature per

*Defence Island bioherm, GoPro Black (enhanced), April 27, 2018, full sun with* ≤*30 m visibility at all depths. The lower two video frames show the southwestern side of reef, shot from the southwest (N slope left, S slope right). Middle frame is of mid-reef, shot from southwest on the mid-line ridge of the reef. Top photo is of the* 

In October of 2016, various sponges were found cut off and lying loose after apparent contact with a sport downrigger fishing line that hit the reef. Four complete sponge bushes were fixed to the reef with PVC pipes (uppermost in **Figure 1**), and a sliced section of a sponge head was placed precisely against its intact host sponge, and the healing and reattachment were monitored with video. The transplanted

Surrounding the transplanted sponges at the shallowest ridge at the east side of the reef (**Figure 1**; top), a grid of half-meter spaced measures with an avalanche probe was conducted to measure depth of bioherm over solid rock. Previous transect measures with that probe had established that the shallowest ridge top where the transplants were installed had the least depth of reef substrate, suitable

presented to demonstrate shape and relative size at a given date.

sponges now provide new fixed location identifiers.

Unplanned events led to research opportunities. The pipe vee had been installed in July 2009, prior to the 2009/2010 El Niño which coincided with collapse of many sponges through 2010–2012, including formation of a drift of sponge debris that came to rest just below that pipe vee. Recovery and regrowth of that pipe vee sponge drift has since then been monitored with video recordings. Specific video frames are

*DOI: http://dx.doi.org/10.5772/intechopen.82325*

date and presented graphically.

*northeast end of the ridge.*

**Figure 1.**

*Formation, Persistence, and Recovery of Glass Sponge Reefs: A Case Study DOI: http://dx.doi.org/10.5772/intechopen.82325*

#### **Figure 1.**

*Invertebrates - Ecophysiology and Management*

base of a bioherm.

**2. Methods**

enables living sponges to attach to this substrate.

does not ordinarily occur at sponge gardens.

installed in 2009 for camera positioning.

base that provides stability to the living reef, stabilizes dead sponge skeletons, and

Bioherms are considered "bedrock averse" in terms of underlying geologic substrate [3]; glacial sediments are the normal underlying substrate for bioherm formation. Depth data for the shallowest extent of an inshore bioherm are interpreted as indicating a bedrock substrate for at least a peripheral part of the reef we have studied. Observations at a sponge garden suggest a possible successional community including sediment-accumulating species that could develop the substrate of sedimented dictyonine sponge fragments that constitutes the geomorphologic

The present study spanned climate events that may relate to trends in sponge mortality. The El Niño of 2015/2016 started in November of 2014 and lasted until May of 2016 with anomalies as high as 2.6 (http://tinyurl.com/NOAAONI). Two modest La Niña climate events occurred from August to December 2016 (maximum anomaly of

Over 100 scuba dives were conducted from 2007 to 2018 at the inshore Defence

Divers with the Underwater Council of British Columbia inserted temperature loggers in the seabed of various sponge reefs in Howe Sound from 2014 through 2018, including the present site. Loggers were replaced at intervals so that most sites had nearly continuous records. The observations spanned El Niño (2015/2016) and La Niña (2016/2017, 2017/2018) climate events. Beginning in May 2014, Thermochron® iButton temperature loggers (version DS1921Z-F5; accuracy = ±1.0°C) were deployed at six sponge reefs in Howe Sound, data from four of which are presented here. Loggers were placed in among the sponges using PVC pipe holders and left there for up to 1 year, logging at intervals of either 2, 3, or 4 hours. Loggers were collected and data downloaded as often as possible, though weather and boating restricted the collection of some loggers such that gaps in data occurred. Two of the six reefs had significant gaps in data so are not presented here.

Island bioherm (**Figure 1**) in Howe Sound, British Columbia (49°34.66 N, 123°16.41 W). Difficulty in relating video frames to individually identifiable sponges led to installation of 12 bar-coded locator stakes [5] in 2014 that also had a mark to indicate the depth of the reef substrate at the time of installation. Growth and death of sponges near these marker stakes were monitored with video recordings. All photographs and videos used for analysis in this chapter include one of these locator stakes or some other landmarks such as a temperature logger, a sonde oceanographic buoy, or a pair of pipes called the "pipe vee" which had been

−0.7) and from October 2017 to March 2018 (maximum anomaly of −1.0). The literature indicates that dead sponge skeletons on a bioherm become embedded intact by sediment and that new sponge growth is based on planktonic settlement of sexually produced sponge propagules that settle on dead sponge skeletons [1, 4]. Not all growth is based on newly settled sponges, since recovery of damaged sponge tissue also occurs [5]. As well, fallen fragments of cloud sponge (*Aphrocallistes vastus*) have capacity to reattach and resume growth [6]. The consequences of collapse and potential for recovery, reattachment, and continued growth have not been compared for glass sponge gardens versus glass sponge reefs. This book chapter presents a theory of scree slope drift formation at sponge reefs as a means of relatively rapid growth for bioherms and further posits that such recovery

**132**

*Defence Island bioherm, GoPro Black (enhanced), April 27, 2018, full sun with* ≤*30 m visibility at all depths. The lower two video frames show the southwestern side of reef, shot from the southwest (N slope left, S slope right). Middle frame is of mid-reef, shot from southwest on the mid-line ridge of the reef. Top photo is of the northeast end of the ridge.*

Data collected from 2014 to 2018 were summarized as an average temperature per date and presented graphically.

Unplanned events led to research opportunities. The pipe vee had been installed in July 2009, prior to the 2009/2010 El Niño which coincided with collapse of many sponges through 2010–2012, including formation of a drift of sponge debris that came to rest just below that pipe vee. Recovery and regrowth of that pipe vee sponge drift has since then been monitored with video recordings. Specific video frames are presented to demonstrate shape and relative size at a given date.

In October of 2016, various sponges were found cut off and lying loose after apparent contact with a sport downrigger fishing line that hit the reef. Four complete sponge bushes were fixed to the reef with PVC pipes (uppermost in **Figure 1**), and a sliced section of a sponge head was placed precisely against its intact host sponge, and the healing and reattachment were monitored with video. The transplanted sponges now provide new fixed location identifiers.

Surrounding the transplanted sponges at the shallowest ridge at the east side of the reef (**Figure 1**; top), a grid of half-meter spaced measures with an avalanche probe was conducted to measure depth of bioherm over solid rock. Previous transect measures with that probe had established that the shallowest ridge top where the transplants were installed had the least depth of reef substrate, suitable

for measure with the probe. We used a 3-m avalanche probe to determine the depth of bioherm sediment accumulation on top of the rocky reef. We measured sediment depth within a 300 × 300 cm grid centered on the ridge of transplanted sponges. To ensure the measurements were 50 cm away from one another, we used a 50 × 50 cm quadrat to mark each position before inserting the probe. At each position, we inserted the probe until it hit hard substrate, recorded the bioherm depth to the nearest 5 cm, and recorded the water depth to the nearest 0.1 m. Measurements were taken on August 24, 2018, and September 14, 2018. To correct for variation in tidal height between the 2 days, we measured the water depth at one of the sampling positions twice (i.e., on both days). Because the water was 2.2 m higher on September 14, we subtracted 2.2 m from all water depth measurements taken that day. We then further corrected all measurements to zero tide by subtracting 1.1 m, which was the height of the nearest slack tide on August 24. At 5 of 42 measuring positions within our grid, we could not measure sediment or water depth without risking damage to the sponges. In those instances, we interpolated the measurements by taking the average of the nearest two measurements on either side. Data were plotted using surface plots in Microsoft Excel. The bioherm thickness and the depth of the hard substrate were plotted separately.

A sponge garden on glacial till at west Bowen Island (49°23.26 N, 123°24.76 W) was videotaped in July 2013 and August 2018, capturing images of sedimentation around glass sponges and their dead fragments, along with other marine organisms that accumulated sediment. These videos were reviewed, and all identifiable animal species in the vicinity of glass sponges were recorded. A cluster of cloud sponges (called Baker's Dozen) at this site was videotaped in 2012 and 2015 to document relative growth of various sponge bushes.

### **3. Results**

Temperature logger data for the present study site (inshore Defence Island) and three other sites are detailed in **Figure 2**. All four sites had temperature spikes in late summer of 2015 exceeding 10.0°C, but only the inshore Defence Island site exceeded 9.0°C through spring and summer of 2015 as well, before the intensification of the 2015/2016 El Niño. Note that Passage Island is the only other bioherm site as shallow as the present study site; the location of the Passage site (49°20.27 N, 123°18.89 W) is at the south entry to Howe Sound, whereas the present Defence site is at the inner sill to the north.

At the Defence bioherm, the pipe vee scree drift formed in 2010–2012 and its subsequent recovery, growth, and loss of successive bushes was documented through 2018 (**Figure 3**). The first frame in **Figure 3** (viewed from east end) shows primarily dead sponge tissue in the center of the drift, with small tubes and mittens emerging from the dead tissue. The second frame in **Figure 3** shows the pipe vee and the drift from the east; the third is an overhead shot that includes two transplanted tubes of sponge at the downhill east and west sides (both transplants perished within 2 years). The last frame shows the central portion of the drift continuing to grow, whereas the western cluster of sponge in the foreground had fallen over in the downhill direction. That fallen cluster had grown as vertical tubes without any sideways mittens contacting the surrounding substrate. The eastern head of sponge had been hit by fishing gear in fall of 2016 and had subsequently collapsed and perished.

At the distant Passage Island bioherm site, possible debris drift formation is evident on the east slope of the reef (**Figure 4**). The lower edges of those apparent drifts in **Figure 4** have well-developed sponges, but above the middle drift in the

**135**

**Figure 3.**

**Figure 2.**

*British Columbia, May 2014–September 2018.*

*Formation, Persistence, and Recovery of Glass Sponge Reefs: A Case Study*

*Temperature at the inshore Defence Island bioherm and three similarly shallow bioherms in Howe Sound,* 

*Pipe vee sponge debris scree drift. Growth and subsequent tissue loss: top left—July 10, 2013; top right—May 1, 2014; bottom left—October 26, 2015; and bottom right—April 27, 2018. Circles identify same sponge. Note* 

*foreground center of lowest photo (arrow) shows fallen sponge from debris drift (W end).*

*DOI: http://dx.doi.org/10.5772/intechopen.82325*

*Formation, Persistence, and Recovery of Glass Sponge Reefs: A Case Study DOI: http://dx.doi.org/10.5772/intechopen.82325*

#### **Figure 2.**

*Invertebrates - Ecophysiology and Management*

depth of the hard substrate were plotted separately.

relative growth of various sponge bushes.

is at the inner sill to the north.

collapsed and perished.

**3. Results**

for measure with the probe. We used a 3-m avalanche probe to determine the depth of bioherm sediment accumulation on top of the rocky reef. We measured sediment depth within a 300 × 300 cm grid centered on the ridge of transplanted sponges. To ensure the measurements were 50 cm away from one another, we used a 50 × 50 cm quadrat to mark each position before inserting the probe. At each position, we inserted the probe until it hit hard substrate, recorded the bioherm depth to the nearest 5 cm, and recorded the water depth to the nearest 0.1 m. Measurements were taken on August 24, 2018, and September 14, 2018. To correct for variation in tidal height between the 2 days, we measured the water depth at one of the sampling positions twice (i.e., on both days). Because the water was 2.2 m higher on September 14, we subtracted 2.2 m from all water depth measurements taken that day. We then further corrected all measurements to zero tide by subtracting 1.1 m, which was the height of the nearest slack tide on August 24. At 5 of 42 measuring positions within our grid, we could not measure sediment or water depth without risking damage to the sponges. In those instances, we interpolated the measurements by taking the average of the nearest two measurements on either side. Data were plotted using surface plots in Microsoft Excel. The bioherm thickness and the

A sponge garden on glacial till at west Bowen Island (49°23.26 N, 123°24.76 W) was videotaped in July 2013 and August 2018, capturing images of sedimentation around glass sponges and their dead fragments, along with other marine organisms that accumulated sediment. These videos were reviewed, and all identifiable animal species in the vicinity of glass sponges were recorded. A cluster of cloud sponges (called Baker's Dozen) at this site was videotaped in 2012 and 2015 to document

Temperature logger data for the present study site (inshore Defence Island) and three other sites are detailed in **Figure 2**. All four sites had temperature spikes in late summer of 2015 exceeding 10.0°C, but only the inshore Defence Island site exceeded 9.0°C through spring and summer of 2015 as well, before the intensification of the 2015/2016 El Niño. Note that Passage Island is the only other bioherm site as shallow as the present study site; the location of the Passage site (49°20.27 N, 123°18.89 W) is at the south entry to Howe Sound, whereas the present Defence site

At the Defence bioherm, the pipe vee scree drift formed in 2010–2012 and its subsequent recovery, growth, and loss of successive bushes was documented through 2018 (**Figure 3**). The first frame in **Figure 3** (viewed from east end) shows primarily dead sponge tissue in the center of the drift, with small tubes and mittens emerging from the dead tissue. The second frame in **Figure 3** shows the pipe vee and the drift from the east; the third is an overhead shot that includes two transplanted tubes of sponge at the downhill east and west sides (both transplants perished within 2 years). The last frame shows the central portion of the drift continuing to grow, whereas the western cluster of sponge in the foreground had fallen over in the downhill direction. That fallen cluster had grown as vertical tubes without any sideways mittens contacting the surrounding substrate. The eastern head of sponge had been hit by fishing gear in fall of 2016 and had subsequently

At the distant Passage Island bioherm site, possible debris drift formation is evident on the east slope of the reef (**Figure 4**). The lower edges of those apparent drifts in **Figure 4** have well-developed sponges, but above the middle drift in the

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*Temperature at the inshore Defence Island bioherm and three similarly shallow bioherms in Howe Sound, British Columbia, May 2014–September 2018.*

#### **Figure 3.**

*Pipe vee sponge debris scree drift. Growth and subsequent tissue loss: top left—July 10, 2013; top right—May 1, 2014; bottom left—October 26, 2015; and bottom right—April 27, 2018. Circles identify same sponge. Note foreground center of lowest photo (arrow) shows fallen sponge from debris drift (W end).*

#### **Figure 4.**

*Passage Island bioherm with possible debris drifts at lower elevations on the east slope. Note debris fragments with recent growth (circled) above central sponge row at lower center.*

center of the frame, there are disorganized, collapsed sponge fragments and small outgrowths of sponge that may represent tissue recovery rather than rapid growth of newly settled sponges.

The fishing gear damage to the Defence bioherm in fall of 2016 led to opportunistic transplanting of four sponge bushes at the shallowest ridge top (**Figure 5**). A loose fragment of sponge sliced from an otherwise intact host sponge bush was replaced against the host tissue and secured with stakes (**Figure 6**). By 2018 the transplants were growing and had attached to the stakes and to the underlying bioherm substrate (**Figure 5**). The staked slice of tissue was completely healed, and no sign of the slice location was evident. In September 2018, the westernmost transplant was about half dead, possibly indicating the onset of a 2018/2019 El Niño that is not confirmed on the Ocean Niño Index at the time of writing (**Figure 7**). Another

#### **Figure 5.**

*Ridge top transplants (conducted October 2016), February 13, 2018. Top left photo viewed from north; top right photo viewed from south. Note attachments (circled) of sponge mittens to substrate (bottom right photo) and to stake (bottom left photo).*

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had largely died by 2017.

*Formation, Persistence, and Recovery of Glass Sponge Reefs: A Case Study*

*Loose slice of sponge replaced against host tissue and secured with pipe stakes in October 2016.*

loose sponge head that had been staked in place at another part of the reef also died

*Upper photo: west transplant at ridge top dying, October 9, 2018. Lower left photo, transplant by 2-blue with* 

At the west Bowen Island sponge garden, four sponge heads labeled (A), (B), (C), and (D) in **Figure 8** grew relatively rapidly between September 2012 and May 2015. During fall of 2015, these sponges suffered tissue loss during the record

Examples of rapid mortality at the inshore Defence bioherm were identified by means of the bar-coded locator stakes (**Figures 9**–**11**). At the stake with 1-black stripe (at stake top), we saw rapid necrosis of part of a sponge head over a 3-month period during spring 2015, with no subsequent spread of mortality over the next 3 years (**Figure 9**). **Figure 10** shows the sponge tissue marked at the 2-black stake in 2014 that had died adjacent to the stake by May 2015; tissue growth was evident upslope from that dead sponge by 2018. In **Figure 11** the sponge tissue at 1-green

Upright dead sponges were observed to collapse after some period of time. At the 2-yellow stripe stake (**Figure 12**), a group of intact, dead sponges observed

2015/2016 El Niño. Growth has been negligible in the subsequent 3 years.

*dead core on July 24, 2017. Lower right, October 9, 2018, same transplant largely dead.*

suddenly in the August/September period of 2018.

*DOI: http://dx.doi.org/10.5772/intechopen.82325*

**Figure 6.**

**Figure 7.**

#### **Figure 6.**

*Invertebrates - Ecophysiology and Management*

of newly settled sponges.

**Figure 4.**

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**Figure 5.**

*stake (bottom left photo).*

*Ridge top transplants (conducted October 2016), February 13, 2018. Top left photo viewed from north; top right photo viewed from south. Note attachments (circled) of sponge mittens to substrate (bottom right photo) and to* 

center of the frame, there are disorganized, collapsed sponge fragments and small outgrowths of sponge that may represent tissue recovery rather than rapid growth

*Passage Island bioherm with possible debris drifts at lower elevations on the east slope. Note debris fragments* 

*with recent growth (circled) above central sponge row at lower center.*

The fishing gear damage to the Defence bioherm in fall of 2016 led to opportunistic transplanting of four sponge bushes at the shallowest ridge top (**Figure 5**). A loose fragment of sponge sliced from an otherwise intact host sponge bush was replaced against the host tissue and secured with stakes (**Figure 6**). By 2018 the transplants were growing and had attached to the stakes and to the underlying bioherm substrate (**Figure 5**). The staked slice of tissue was completely healed, and no sign of the slice location was evident. In September 2018, the westernmost transplant was about half dead, possibly indicating the onset of a 2018/2019 El Niño that is not confirmed on the Ocean Niño Index at the time of writing (**Figure 7**). Another

*Loose slice of sponge replaced against host tissue and secured with pipe stakes in October 2016.*

#### **Figure 7.**

*Upper photo: west transplant at ridge top dying, October 9, 2018. Lower left photo, transplant by 2-blue with dead core on July 24, 2017. Lower right, October 9, 2018, same transplant largely dead.*

loose sponge head that had been staked in place at another part of the reef also died suddenly in the August/September period of 2018.

At the west Bowen Island sponge garden, four sponge heads labeled (A), (B), (C), and (D) in **Figure 8** grew relatively rapidly between September 2012 and May 2015. During fall of 2015, these sponges suffered tissue loss during the record 2015/2016 El Niño. Growth has been negligible in the subsequent 3 years.

Examples of rapid mortality at the inshore Defence bioherm were identified by means of the bar-coded locator stakes (**Figures 9**–**11**). At the stake with 1-black stripe (at stake top), we saw rapid necrosis of part of a sponge head over a 3-month period during spring 2015, with no subsequent spread of mortality over the next 3 years (**Figure 9**). **Figure 10** shows the sponge tissue marked at the 2-black stake in 2014 that had died adjacent to the stake by May 2015; tissue growth was evident upslope from that dead sponge by 2018. In **Figure 11** the sponge tissue at 1-green had largely died by 2017.

Upright dead sponges were observed to collapse after some period of time. At the 2-yellow stripe stake (**Figure 12**), a group of intact, dead sponges observed

#### **Figure 8.**

*Baker's Dozen center sponges from north, September 26, 2012 (left); and same center sponges from north, May 4, 2015 (right). Letters identify same specific sponges.*

**Figure 9.** *Top left—Defence 1-black: February 20, 2015; top right—May 31, 2015 (Paul Sim photo); and bottom: April 27, 2018.*

during 2013 and 2014 had collapsed by 2018. The actual time required for collapse is probably very brief, as upright, dead sponges filmed on the bioherm ridge top on June 17, 2013, had collapsed by July 10, 2013.

Bioherm base layer depth at the upper ridge of the inshore Defence Island sponge reef varied from 0.30 to 1.45 m deep over an area of 3 × 3 m, with adjacent measures usually varying on the order of 0.1–0.2 m between adjacent probings at distances of 0.5 m (**Table 1**). The plot of hard bottom depth is consistent with bedrock (**Figure 13**) rather than glacial till, in which much more variation in depth would be expected on a recurring basis.

Detailed observations were made at the shallow-sloped west Bowen Island sponge garden with attention to sedimentation around dictyonine hexactinellid sponges on glacial till. Taxonomy of the community occurring at this site in 2013 and 2018 in association with the glass sponges included moderate abundances of rough patch shrimp (*Pandalus stenolepis*), galatheid crab (*Munida quadrispina*),

**139**

**Figure 11.**

**Figure 12.**

**Figure 10.**

*Formation, Persistence, and Recovery of Glass Sponge Reefs: A Case Study*

bristly tunicate (*Halocynthia igaboja*), fan bryozoan (*Dendrobeania murrayana*), vermilion star (*Mediaster aequalis*), white blood star (*Henricia* sp.), giant sea cucumber (*Apostichopus californicus*), and blackeye goby (*Rhinogobius nicholsii*), plus lesser abundances of 40 other animal species, not including sponges. Sponges included over 1000 cloud sponges (*Aphrocallistes vastus*) and over 1000

*Rapid necrosis of sponge adjacent to stake with 2-black stripes, intact February 20, 2015 (top), dead May 31, 2015 (middle—Paul Sim photo) and subsequent growth upslope (circled) from dead tissue, April 27, 2018 (note* 

*Marker stake (1-green stripe): May 1, 2014 (left) and July 25, 2017 (right).*

*Dead sponges upright at 2-yellow stake in 2014 (left) and collapsed in 2018 (right).*

*DOI: http://dx.doi.org/10.5772/intechopen.82325*

*Metridium anemone and rockfish at top of stake).*

*Formation, Persistence, and Recovery of Glass Sponge Reefs: A Case Study DOI: http://dx.doi.org/10.5772/intechopen.82325*

#### **Figure 10.**

*Invertebrates - Ecophysiology and Management*

*May 4, 2015 (right). Letters identify same specific sponges.*

during 2013 and 2014 had collapsed by 2018. The actual time required for collapse is probably very brief, as upright, dead sponges filmed on the bioherm ridge top on

*Top left—Defence 1-black: February 20, 2015; top right—May 31, 2015 (Paul Sim photo); and bottom: April* 

*Baker's Dozen center sponges from north, September 26, 2012 (left); and same center sponges from north,* 

Bioherm base layer depth at the upper ridge of the inshore Defence Island sponge reef varied from 0.30 to 1.45 m deep over an area of 3 × 3 m, with adjacent measures usually varying on the order of 0.1–0.2 m between adjacent probings at distances of 0.5 m (**Table 1**). The plot of hard bottom depth is consistent with bedrock (**Figure 13**) rather than glacial till, in which much more variation in depth

Detailed observations were made at the shallow-sloped west Bowen Island sponge garden with attention to sedimentation around dictyonine hexactinellid sponges on glacial till. Taxonomy of the community occurring at this site in 2013 and 2018 in association with the glass sponges included moderate abundances of rough patch shrimp (*Pandalus stenolepis*), galatheid crab (*Munida quadrispina*),

June 17, 2013, had collapsed by July 10, 2013.

would be expected on a recurring basis.

**138**

**Figure 9.**

**Figure 8.**

*27, 2018.*

*Rapid necrosis of sponge adjacent to stake with 2-black stripes, intact February 20, 2015 (top), dead May 31, 2015 (middle—Paul Sim photo) and subsequent growth upslope (circled) from dead tissue, April 27, 2018 (note Metridium anemone and rockfish at top of stake).*

**Figure 11.** *Marker stake (1-green stripe): May 1, 2014 (left) and July 25, 2017 (right).*

**Figure 12.** *Dead sponges upright at 2-yellow stake in 2014 (left) and collapsed in 2018 (right).*

bristly tunicate (*Halocynthia igaboja*), fan bryozoan (*Dendrobeania murrayana*), vermilion star (*Mediaster aequalis*), white blood star (*Henricia* sp.), giant sea cucumber (*Apostichopus californicus*), and blackeye goby (*Rhinogobius nicholsii*), plus lesser abundances of 40 other animal species, not including sponges. Sponges included over 1000 cloud sponges (*Aphrocallistes vastus*) and over 1000


*Row and column labels correspond to the coordinates in* **Figure 13***. Numbers in brackets were interpolated based on adjacent values because live sponges growing at these locations prevented the use of the avalanche probe.*

#### **Table 1.**

*Bioherm base thickness (cm) as measured with an avalanche probe.*

#### **Figure 13.**

*Depth of the hard substrate beneath the bioherm basal layer at the Defence Island bioherm ridge. Depth was calculated by summing the water depth at zero tide and the bioherm depth, which was determined using an avalanche probe inserted into the sediment at 50 cm increments. North is toward the top and left-most position of the figure.*

boot sponges (*Rhabdocalyptus dawsoni*) in each year, plus about 10 vase sponges (*Heterochone calyx*) in 2013 and over 500 in 2018, the increase in apparent numbers owing to the inability to distinguish small cloud and vase sponges in 2013. The yellow boring sponge (*Cliona californiana*) was moderately abundant, and the white meandering sponge (*Haliclona* cf. *mollis*) was at high abundance in both years. Algae included moderate abundance of red rock crust (*Hildenbrandia* spp.) and crustose corallines (*Clathromorphum*, *Lithothamnion*). Video frames in **Figure 14** lead to the hypothesis that the non-reef-forming lyssacine Hexactinellid boot sponge as well as the bristly tunicate may sequester sediment that eventually stabilizes the fallen dictyonine cloud sponge or vase sponge skeletons lying in the same vicinity. Thus, new sponges can settle on sediment-stabilized sponge fragments as well as on rock until eventually all growth might be on a bioherm-type of sedimented base composed of dictyonine sponges and their fragments.

**141**

**4. Discussion**

**Figure 14.**

soon affect shallow bioherms.

*Formation, Persistence, and Recovery of Glass Sponge Reefs: A Case Study*

Glass sponge mortalities occurred at various times throughout the period of dive surveys from 2007 to 2018. Particularly extensive mortalities were associated with the El Niño climate events of 2009/2010 and 2015/2016. Note that the episode of mortality in sponge at the 1-black and 2-black stake sites occurred during the onset of the 2015/2016 El Niño during early spring of 2015 (anomalies of 0.6–1.0). This was during a period when temperatures were higher at this site than at the other three sites (**Figure 2**), whereas other sponge mortalities seemed to coincide with the heightening of that climate event during August/September 2015 (anomalies reaching 1.8 and 2.1). The coincidence of several mortality events during August/ September of 2018 may enable a prediction for testing by subsequent Ocean Niño Index records for 2018/2019 if another El Niño occurs. The onset of increased mortalities in August and September of 2018 (**Figure 7**) may relate to temperature spikes associated with the onset of an El Niño climate phase at the shallow bioherms in Howe Sound. It should also be mentioned that the pH of local seawater hit low extreme levels of 7.3 in 2009 and 7.4 in 2015, compared to modal levels of about 7.7 through that period [7]; thus, low pH may interact with elevated temperature in stressing glass sponges. Interaction of climate warming and ocean acidification may

*Sedimentation around cloud sponges and boot sponges at the west Bowen Island sponge garden. Note sponge side* 

*attachment to both rock and dead sponge fragments in the middle photo.*

It needs to be emphasized that, without the deployment of markers [5], it would not have been possible to identify specific sponge clusters or the changes that occurred to them over time. Considerable confusion existed in trying to orient to the reef in 2012 after a period of absence during which the damage from the 2009/2010 El Niño reshaped the appearance of the reef; it was in the aftermath of that period that stakes were deployed in winter of 2013/2014. Similarly, the episode of fishing gear damage in fall of 2016 resulted in disorientation on the reef until videos of marker stakes were scrutinized and certain bushes of sponge were identified as loose and others were spotted with cuts through them. The staking of

*DOI: http://dx.doi.org/10.5772/intechopen.82325*

#### **Figure 14.**

*Invertebrates - Ecophysiology and Management*

**Table 1.**

**A B C D E F G**

 110 145 140 (125) 110 115 120 75 70 85 (95) 105 95 95 70 70 60 (70) 80 90 70 80 70 75 (82.5) 90 70 55 55 65 80 (70) 60 45 55 80 75 65 60 55 30 40 *Row and column labels correspond to the coordinates in* **Figure 13***. Numbers in brackets were interpolated based on* 

*adjacent values because live sponges growing at these locations prevented the use of the avalanche probe.*

boot sponges (*Rhabdocalyptus dawsoni*) in each year, plus about 10 vase sponges (*Heterochone calyx*) in 2013 and over 500 in 2018, the increase in apparent numbers owing to the inability to distinguish small cloud and vase sponges in 2013. The yellow boring sponge (*Cliona californiana*) was moderately abundant, and the white meandering sponge (*Haliclona* cf. *mollis*) was at high abundance in both years. Algae included moderate abundance of red rock crust (*Hildenbrandia* spp.) and crustose corallines (*Clathromorphum*, *Lithothamnion*). Video frames in **Figure 14** lead to the hypothesis that the non-reef-forming lyssacine Hexactinellid boot sponge as well as the bristly tunicate may sequester sediment that eventually stabilizes the fallen dictyonine cloud sponge or vase sponge skeletons lying in the same vicinity. Thus, new sponges can settle on sediment-stabilized sponge fragments as well as on rock until eventually all growth might be on a bioherm-type of

*Depth of the hard substrate beneath the bioherm basal layer at the Defence Island bioherm ridge. Depth was calculated by summing the water depth at zero tide and the bioherm depth, which was determined using an avalanche probe inserted into the sediment at 50 cm increments. North is toward the top and left-most position* 

sedimented base composed of dictyonine sponges and their fragments.

*Bioherm base thickness (cm) as measured with an avalanche probe.*

**140**

**Figure 13.**

*of the figure.*

*Sedimentation around cloud sponges and boot sponges at the west Bowen Island sponge garden. Note sponge side attachment to both rock and dead sponge fragments in the middle photo.*
