**2. Environmental influences on the distribution and magnitude of benthic blue carbon around polar seabeds**

Sediment cores taken by geological scientists around the polar regions have shown very considerable patchiness in the both the amount and proportion of carbonate (CaCO<sup>3</sup> ) in polar sediments [8]. Benthic biological work over the last century has similarly demonstrated a huge variety in the carbon stocks held in biota on the seabed [10]. The source of these is the dissolved carbon (dioxide) in water masses and huge, but intensely seasonal productivity by phytoplankton and dependent consumers, such as copepods and euphausiid crustaceans. The variability in the blue carbon component, despite being complex in both time and space, is predictable on some scales, but knowledge levels are also very patchy. The interface of the water column and the underlying sediments, the seabed, is a very dynamic environment for carbon [11]. Primary productivity, fecal pellets and dead organisms rain down to the seabed where they are mainly broken down by the 'microbial loop', thus recycling much of the carbon from near surface waters.

#### **2.1. Carbonate in sediments**

Remarkably it was not until 2012 that the first circum-southern polar data set of carbonate in sediments was compiled (from just over 200 sediments cores from Antarctica's shelf seas [8]). Low-Magnesium calcite is the dominant phase of sediment carbonate, but high-Magnesium calcite, pure calcite and aragonite are also present. The study found that the proportion of carbonate in sediments was typically low, but could be above 15% in some shallow Weddell and deep Amundsen and Bellingshausen shelf areas. The magnitude of values found was very patchy, but most of the highest values were close to the edge of shelf (termed 'shelf break'). Even at the shelf break in the same sea carbonate could vary an order of magnitude between adjacent sites, so clearly local factors are very important as well. Notably sediments in regions of high primary production (surface microalgae productivity) such as the West Antarctic Peninsula and Ross Sea were generally below 5% carbonate. The authors concluded that the evidence in their meta-analysis was that benthic animals were not significant contributors to sediment carbonate content. Their core and data spatial coverage, although sparse around East Antarctica (as most marine data sets are), seemingly represented the spectrum of most shelf environments. However the conclusions based on existing samples could be underestimating faunal contributions for several reasons. 1) Across depths, faunal biomass and production is typically highest in the shallows (top 100 m) which were not represented. 2) Across habitats, faunal biomass and production is typically highest in difficult to core situations, such as glacial moraines, sea mounts and steep surfaces. 3) Much faunal production close to shelf breaks may be bulldozed over the edge to cascade down steep continental slopes and canyons – these are heavily iceberg scoured environments (**Figure 2**). However most blue carbon, the totality of carbon captured by organisms, is not in the form of carbonate but organic carbon as tissue.

slope depths, on young or ice scoured surfaces, underneath Antarctic ice shelves or in other

**Figure 2.** Iceberg scouring tracks recorded by the NERC-Conicyt ICEBERGS voyage of RRS James Clark Ross, Marguerite

Blue Carbon on Polar and Subpolar Seabeds http://dx.doi.org/10.5772/intechopen.78237 41

Some organism types are very much more important than others in terms of carbon and carbonate capture and storage. Some entire animal groups are poorly represented or absent altogether in the polar waters so clearly contribute little to carbon budgets. Typically variability in carbon contribution can be because of population and individual size (biomass), growth rates, ubiquity and the body structure and chemistry of different organisms. For example amongst the plankton the tiny foraminifera *Neogloboquadrina pachyderma* is both very abundant and ubiquitous around the Southern Ocean, and superabundant in sea ice, making it the single biggest carbonate producer [12]. A very different type and size of animal, the pelagic mollusk, pteropods (**Figure 3**) is next most important. As with foraminifers, around the Antarctica one species, *Limacina helicina*, dominates biomass [13]. Blue carbon captured and stored on the seabed by benthos is much less dominated by any one species or even any one type of animal. Sponges, echinoderms (such as sea stars and sea urchins), bryozoans (**Figure** 1**a**), polychaete worms (**Figure** 1**b**), molluscs

extreme environmental situations.

Bay, West Antarctic peninsula, 2017.

*2.2.1. Organism identity*

#### **2.2. Carbon held by marine animals (blue carbon)**

Carbon captured by, and stored in, benthic organisms varies (within a set amount of space) over several orders of magnitude. Standing stocks peak in the kelp forests of the subpolar shallows with many kilograms per m2 but decreases to less than a few grams by continental

**Figure 2.** Iceberg scouring tracks recorded by the NERC-Conicyt ICEBERGS voyage of RRS James Clark Ross, Marguerite Bay, West Antarctic peninsula, 2017.

slope depths, on young or ice scoured surfaces, underneath Antarctic ice shelves or in other extreme environmental situations.

#### *2.2.1. Organism identity*

**2. Environmental influences on the distribution and magnitude of**

by the 'microbial loop', thus recycling much of the carbon from near surface waters.

erable patchiness in the both the amount and proportion of carbonate (CaCO<sup>3</sup>

Sediment cores taken by geological scientists around the polar regions have shown very consid-

[8]. Benthic biological work over the last century has similarly demonstrated a huge variety in the carbon stocks held in biota on the seabed [10]. The source of these is the dissolved carbon (dioxide) in water masses and huge, but intensely seasonal productivity by phytoplankton and dependent consumers, such as copepods and euphausiid crustaceans. The variability in the blue carbon component, despite being complex in both time and space, is predictable on some scales, but knowledge levels are also very patchy. The interface of the water column and the underlying sediments, the seabed, is a very dynamic environment for carbon [11]. Primary productivity, fecal pellets and dead organisms rain down to the seabed where they are mainly broken down

Remarkably it was not until 2012 that the first circum-southern polar data set of carbonate in sediments was compiled (from just over 200 sediments cores from Antarctica's shelf seas [8]). Low-Magnesium calcite is the dominant phase of sediment carbonate, but high-Magnesium calcite, pure calcite and aragonite are also present. The study found that the proportion of carbonate in sediments was typically low, but could be above 15% in some shallow Weddell and deep Amundsen and Bellingshausen shelf areas. The magnitude of values found was very patchy, but most of the highest values were close to the edge of shelf (termed 'shelf break'). Even at the shelf break in the same sea carbonate could vary an order of magnitude between adjacent sites, so clearly local factors are very important as well. Notably sediments in regions of high primary production (surface microalgae productivity) such as the West Antarctic Peninsula and Ross Sea were generally below 5% carbonate. The authors concluded that the evidence in their meta-analysis was that benthic animals were not significant contributors to sediment carbonate content. Their core and data spatial coverage, although sparse around East Antarctica (as most marine data sets are), seemingly represented the spectrum of most shelf environments. However the conclusions based on existing samples could be underestimating faunal contributions for several reasons. 1) Across depths, faunal biomass and production is typically highest in the shallows (top 100 m) which were not represented. 2) Across habitats, faunal biomass and production is typically highest in difficult to core situations, such as glacial moraines, sea mounts and steep surfaces. 3) Much faunal production close to shelf breaks may be bulldozed over the edge to cascade down steep continental slopes and canyons – these are heavily iceberg scoured environments (**Figure 2**). However most blue carbon, the totality of carbon captured by organisms, is not in the form of carbonate but organic carbon as tissue.

Carbon captured by, and stored in, benthic organisms varies (within a set amount of space) over several orders of magnitude. Standing stocks peak in the kelp forests of the subpolar

but decreases to less than a few grams by continental

) in polar sediments

**benthic blue carbon around polar seabeds**

40 Carbon Capture, Utilization and Sequestration

**2.2. Carbon held by marine animals (blue carbon)**

shallows with many kilograms per m2

**2.1. Carbonate in sediments**

Some organism types are very much more important than others in terms of carbon and carbonate capture and storage. Some entire animal groups are poorly represented or absent altogether in the polar waters so clearly contribute little to carbon budgets. Typically variability in carbon contribution can be because of population and individual size (biomass), growth rates, ubiquity and the body structure and chemistry of different organisms. For example amongst the plankton the tiny foraminifera *Neogloboquadrina pachyderma* is both very abundant and ubiquitous around the Southern Ocean, and superabundant in sea ice, making it the single biggest carbonate producer [12]. A very different type and size of animal, the pelagic mollusk, pteropods (**Figure 3**) is next most important. As with foraminifers, around the Antarctica one species, *Limacina helicina*, dominates biomass [13]. Blue carbon captured and stored on the seabed by benthos is much less dominated by any one species or even any one type of animal. Sponges, echinoderms (such as sea stars and sea urchins), bryozoans (**Figure** 1**a**), polychaete worms (**Figure** 1**b**), molluscs

of their resources, such as food. For example very steep surfaces are nearly always bedrock and associated with high current flow whereas very gently sloping, flat seabeds are usually sediment and associated with lower flow. So-called infauna require soft sediments to burrow into or eat to extract microbes whereas hard surfaces are required by many anchored sessile organisms, such as kelp algae and encrusting animals. The spectrum from bed rock to muds and clays can all potentially hold high and low carbon standing stock biodiversity in the polar regions. Investigation of blue carbon by substratum type is often confounded by interaction with other variables, such as depth, geography, history and functional traits (e.g. feeding type). Nevertheless hard surfaces typically have high densities of rich biota, particularly those which are carbonaceous (bryozoans, brachiopods, corals, sponges and some molluscs). Stones which have been embedded in glacier ice, fall out on melting (termed drop-stones) to form blue carbon hotspots of suspension feeders on otherwise less diverse, sediment plains (**Figure** 4**a**) [14]. As a

Blue Carbon on Polar and Subpolar Seabeds http://dx.doi.org/10.5772/intechopen.78237 43

**Figure 4.** Blue carbon with substratum type and history. Drop-stones are blue carbon rich oases in the Arctic Barents Sea (A). Highest burial rates of zoobenthic carbon are associated with mixed substrata of boulders in sediments at South

Georgia (B). Estimates of Carbon immobilization (circle size) and sequestration (star size) (C) [15].

**Figure 3.** Pteropod shells are superabundant on the seabed around some Atlantic Ocean seamounts, here collected on a National Geographic Pristine Seas expedition in 2017.

(such as clams and snails), brachiopods (lampshells) are all typically important, and can each by dominant at particular sites but lots of other taxa can be important depending on the situation (environmental characteristics). Nevertheless organism identity can still qualify much information about the nature of blue carbon at a site, because of differences in the rate and timing of carbon capture, time to first reproduction and life span, chemical form of carbon stored (e.g. skeletal aragonite vs. calcite) vulnerability and other variables.

#### *2.2.2. Substratum type and profile as a factor*

The nature of the seabed often shapes and is shaped by the energy of the environment and thus has a major role in structuring which organisms live there and the quality and quality of their resources, such as food. For example very steep surfaces are nearly always bedrock and associated with high current flow whereas very gently sloping, flat seabeds are usually sediment and associated with lower flow. So-called infauna require soft sediments to burrow into or eat to extract microbes whereas hard surfaces are required by many anchored sessile organisms, such as kelp algae and encrusting animals. The spectrum from bed rock to muds and clays can all potentially hold high and low carbon standing stock biodiversity in the polar regions. Investigation of blue carbon by substratum type is often confounded by interaction with other variables, such as depth, geography, history and functional traits (e.g. feeding type). Nevertheless hard surfaces typically have high densities of rich biota, particularly those which are carbonaceous (bryozoans, brachiopods, corals, sponges and some molluscs). Stones which have been embedded in glacier ice, fall out on melting (termed drop-stones) to form blue carbon hotspots of suspension feeders on otherwise less diverse, sediment plains (**Figure** 4**a**) [14]. As a

(such as clams and snails), brachiopods (lampshells) are all typically important, and can each by dominant at particular sites but lots of other taxa can be important depending on the situation (environmental characteristics). Nevertheless organism identity can still qualify much information about the nature of blue carbon at a site, because of differences in the rate and timing of carbon capture, time to first reproduction and life span, chemical form of carbon stored (e.g.

**Figure 3.** Pteropod shells are superabundant on the seabed around some Atlantic Ocean seamounts, here collected on a

The nature of the seabed often shapes and is shaped by the energy of the environment and thus has a major role in structuring which organisms live there and the quality and quality

skeletal aragonite vs. calcite) vulnerability and other variables.

*2.2.2. Substratum type and profile as a factor*

National Geographic Pristine Seas expedition in 2017.

42 Carbon Capture, Utilization and Sequestration

**Figure 4.** Blue carbon with substratum type and history. Drop-stones are blue carbon rich oases in the Arctic Barents Sea (A). Highest burial rates of zoobenthic carbon are associated with mixed substrata of boulders in sediments at South Georgia (B). Estimates of Carbon immobilization (circle size) and sequestration (star size) (C) [15].

result accumulation of blue carbon by zoobenthos is often most associated with hard surfaces such as boulder scree and glacial moraines [15]. The same work showed that hard surfaces facilitate immobilization of carbon, which is when organic carbon is held within tight matrices of skeleton, such as stony coral polyps (e.g. heavily skeletalized animals are much more likely to fossilize, thus sequestering carbon rather than it being broken down in the microbial loop). However burial conditions, which lead to sequestration are considerably stronger on sediments. Thus highest burial and sequestration rates are found at the interface of hard and soft substrata (**Figure** 4**b,c**). Such a combination is hard to investigate because it is a challenging environment to try and obtain cores from (e.g. the hard rocks break the plastic multi-cores and jam box core closing mechanisms).

accumulation, increased depth also reduces the probability and frequency of iceberg scouring on the seabed, thereby increasing the potential life span of benthos and burial chances. The effect of these confounding depth-correlates are complex biological responses to climate change with depth. For example, climate-forced reductions in sea ice, as is happening around the Arctic and parts of the West Antarctic, can reduce blue carbon in the shallows because of increased ice scour but increase it in deep water because of longer phytoplankton blooms [4]. Substratum type and profile, temperature and geographic factors also change with depth. An example of the latter is that benthos become more geographically separated in time and space (not just bathymetrically) from the origin point of their food because of water current

Blue Carbon on Polar and Subpolar Seabeds http://dx.doi.org/10.5772/intechopen.78237 45

Most, though not all, shallows and shelf are associated with coast in the polar regions, just like elsewhere in the world. This drives an onshore-offshore gradient in polar blue carbon, but it is further exacerbated by most physical change (e.g. melt runoff, glacier retreat and ice shelf collapse) also being coast-associated. There is major temperature, sea ice duration and productivity variability associated with different regions around and between the polar seas, as is reflected in strongly contrasting biomass [10] and sediment carbonate values [8]. Within a distinct area the separation of different habitats and zoobenthic blue carbon performance can be geographically predictable factors, which also reflect regional history. A clear example of this can be seen in the continental shelf around the South Georgia archipelago. Blue carbon accumulation is highest on the glacial moraines, which are generally found close to the shelf break, the furthest extent of grounded ice in the Last Glacial Maximum [15]. However such moraines can also be found at the head of canyons and part way along some coastal fjords. The oldest sediments beyond these moraines have the highest sediment blue carbon values, whereas the sediments within these moraines (which were covered by grounded ice just 20 kya are blue carbon poor (**Figure** 4**c**). The highest blue carbon burial and estimated sequestra-

Zoobenthic blue carbon levels also reflect more recent historical and geographic factors, such as invasion of seabed following glacier retreat, ice shelf collapses and recovery from iceberg impacts. At South Georgia depressed blue carbon values have been measured nearly a decade after giant (thousands of square km in size) iceberg impact [17]. The same study showed there are distinct macrogeographic hotspots of giant iceberg grounding, but the same is true within regions, where shelf breaks are most likely to be impacted. The hotspots of smaller icebergs are more associated with retreating glaciers and longer periods of open water, such as the West Antarctic Peninsula [16, 17]. As with biodiversity succession, the seabed blue carbon within the shallowest hundred meters probably strongly reflects the duration of recovery since the last iceberg scour at any one location. The lowest continental shelf values of blue carbon are those underneath the thick floating ice shelves [18]. However collapse of these can lead to major new phytoplankton blooms and the highest blue carbon capture rates and benthic growth (blue carbon storage levels) [19]. Ice shelf collapses have been most associated with the Weddell and Bellingshausen seas, most recently the major breakout of the 6000 km<sup>2</sup> iceberg from Larsen C. Such events are very important in terms of blue carbon budgets and

tion rates were at the interface of these moraines and sediments.

velocities and directions.

*2.2.4. Geography and history as factors*

#### *2.2.3. Depth as a factor*

Many physical and biological characteristics alter with depth so unsurprisingly it can correlate strongly with benthic carbon accumulation [4]. Increased depth away from the near-surface photic zone progressively separates fauna from their main food supply, phytoplankton, so it reduces growth, densities and biomass [1, 3, 10, 16]. The values of carbon accumulation, immobilization and sequestration can be an order of magnitude lower on the deep continental shelf than in the shallows (**Figure 5**). In deeper water blue carbon values are probably at least an order of magnitude lower again. Conversely to negative depth influences on blue carbon

**Figure 5.** Zoobenthic blue carbon storage fluctuation with time and depth on the West Antarctic peninsula, modified from [4]. Note the apparent phase shift since 2006 coincident with low sea ice levels and high iceberg scouring levels.

accumulation, increased depth also reduces the probability and frequency of iceberg scouring on the seabed, thereby increasing the potential life span of benthos and burial chances. The effect of these confounding depth-correlates are complex biological responses to climate change with depth. For example, climate-forced reductions in sea ice, as is happening around the Arctic and parts of the West Antarctic, can reduce blue carbon in the shallows because of increased ice scour but increase it in deep water because of longer phytoplankton blooms [4]. Substratum type and profile, temperature and geographic factors also change with depth. An example of the latter is that benthos become more geographically separated in time and space (not just bathymetrically) from the origin point of their food because of water current velocities and directions.

#### *2.2.4. Geography and history as factors*

**Figure 5.** Zoobenthic blue carbon storage fluctuation with time and depth on the West Antarctic peninsula, modified from [4]. Note the apparent phase shift since 2006 coincident with low sea ice levels and high iceberg scouring levels.

result accumulation of blue carbon by zoobenthos is often most associated with hard surfaces such as boulder scree and glacial moraines [15]. The same work showed that hard surfaces facilitate immobilization of carbon, which is when organic carbon is held within tight matrices of skeleton, such as stony coral polyps (e.g. heavily skeletalized animals are much more likely to fossilize, thus sequestering carbon rather than it being broken down in the microbial loop). However burial conditions, which lead to sequestration are considerably stronger on sediments. Thus highest burial and sequestration rates are found at the interface of hard and soft substrata (**Figure** 4**b,c**). Such a combination is hard to investigate because it is a challenging environment to try and obtain cores from (e.g. the hard rocks break the plastic multi-cores and

Many physical and biological characteristics alter with depth so unsurprisingly it can correlate strongly with benthic carbon accumulation [4]. Increased depth away from the near-surface photic zone progressively separates fauna from their main food supply, phytoplankton, so it reduces growth, densities and biomass [1, 3, 10, 16]. The values of carbon accumulation, immobilization and sequestration can be an order of magnitude lower on the deep continental shelf than in the shallows (**Figure 5**). In deeper water blue carbon values are probably at least an order of magnitude lower again. Conversely to negative depth influences on blue carbon

jam box core closing mechanisms).

44 Carbon Capture, Utilization and Sequestration

*2.2.3. Depth as a factor*

Most, though not all, shallows and shelf are associated with coast in the polar regions, just like elsewhere in the world. This drives an onshore-offshore gradient in polar blue carbon, but it is further exacerbated by most physical change (e.g. melt runoff, glacier retreat and ice shelf collapse) also being coast-associated. There is major temperature, sea ice duration and productivity variability associated with different regions around and between the polar seas, as is reflected in strongly contrasting biomass [10] and sediment carbonate values [8]. Within a distinct area the separation of different habitats and zoobenthic blue carbon performance can be geographically predictable factors, which also reflect regional history. A clear example of this can be seen in the continental shelf around the South Georgia archipelago. Blue carbon accumulation is highest on the glacial moraines, which are generally found close to the shelf break, the furthest extent of grounded ice in the Last Glacial Maximum [15]. However such moraines can also be found at the head of canyons and part way along some coastal fjords. The oldest sediments beyond these moraines have the highest sediment blue carbon values, whereas the sediments within these moraines (which were covered by grounded ice just 20 kya are blue carbon poor (**Figure** 4**c**). The highest blue carbon burial and estimated sequestration rates were at the interface of these moraines and sediments.

Zoobenthic blue carbon levels also reflect more recent historical and geographic factors, such as invasion of seabed following glacier retreat, ice shelf collapses and recovery from iceberg impacts. At South Georgia depressed blue carbon values have been measured nearly a decade after giant (thousands of square km in size) iceberg impact [17]. The same study showed there are distinct macrogeographic hotspots of giant iceberg grounding, but the same is true within regions, where shelf breaks are most likely to be impacted. The hotspots of smaller icebergs are more associated with retreating glaciers and longer periods of open water, such as the West Antarctic Peninsula [16, 17]. As with biodiversity succession, the seabed blue carbon within the shallowest hundred meters probably strongly reflects the duration of recovery since the last iceberg scour at any one location. The lowest continental shelf values of blue carbon are those underneath the thick floating ice shelves [18]. However collapse of these can lead to major new phytoplankton blooms and the highest blue carbon capture rates and benthic growth (blue carbon storage levels) [19]. Ice shelf collapses have been most associated with the Weddell and Bellingshausen seas, most recently the major breakout of the 6000 km<sup>2</sup> iceberg from Larsen C. Such events are very important in terms of blue carbon budgets and dynamics, both in the water column [20] and the seabed [17]. As a result there is strong connectivity between temperature, ice changes and blue carbon.

#### *2.2.5. Temperature as a factor*

The polar regions, particularly the Southern Ocean, are typically the most thermally constant surface regions of our planet. Annual polar sea temperature variability is generally less than 4°C in the Southern hemisphere but more geographically variable around the Arctic. A major source of variability has been Milankovitch 41 and 101 kyr Earth orbital cycles but this has been overshadowed in the Arctic by rapid, recent, regional climate change. Temperature can theoretically influence blue carbon through influences of ocean chemistry, sea ice formation and duration and physical constraints on enzyme performance, effecting food processing, carbonate synthesis and biomass growth rates. Ashton et al. [21] recently attempted to manipulate polar seabed temperature, whilst leaving other factors unchanged. Their study at Rothera Research Station (WAP), which established a series of temperature controlled artificial substrata, found that temperature had a stronger and more complex influence on growth than expected. A 1°C increase led to a significant increase in blue carbon (but measured as growth increment) whereas responses to a 2°C increase resulted in increased variance of assemblages. The major surprise was the extent of the increased growth (approximately double), which far exceeded that predicted by calculations of a pure temperature effect. The experimental infrastructure has now been transferred to the Canadian Arctic station of Cambridge Bay to compare the response of raised temperature of northern to southern polar nearshore fauna.

#### *2.2.6. Other factors (sedimentation and water chemistry)*

Many environmental factors are likely to influence blue carbon capture and storage rates around polar seas but our knowledge and understanding of these is patchy. Amongst the best studied locations are King George Island (South Shetland Islands, Antarctic Peninsula) in the south and West Spitsbergen (Svalbard) in the North. Multinational, interdisciplinary efforts to study biotic interactions to a multitude of environmental parameters at such places are enabling scientists to examine which factors are most important, to which organism types and to which stages of the carbon pathway. In contrast to Ryder Bay, adjacent to Rothera Research Station, where ice scouring [16, 17] and temperature [21] seem to be most important to carbon storage, at Potter Cove, King George Island, sedimentation mainly dictates the composition and performance of benthos. Sahade et al.'s [22] monitoring of that cove since 1998 showed that amongst the many varying factors for benthic life close to a retreating glacier, it was sediment levels and tolerance to this which drove drastic shifts in organism type. However sedimentation is not only co-linked to other variability such as salinity and nutrients but also varies in several different aspects, such as particle density and particle size distributions.

**2.3. Seasonal and annual increment (growth)**

Sea.

Organisms incrementally capture and store carbon with distinct seasonal and annual variation (mainly caused by feeding reduction or cessation in winter). These temporal signals in carbon accumulation are externally visible in some organisms and observable in others by section (like tree rings) or through isotopic analyses. Thus one of the easiest approaches to measure carbon capture and storage on the seabed is to sequentially sample benthic growth to establish its variance. Because of the multitude of environmental factors influencing the magnitude of these (Section 2.2 above), simultaneous measurement of many local parameters needs to be made, in order to detect and understand any organismal performance trends. Growth (along with other processes, e.g. development) is typically considered to be slow in polar ectotherm organisms, in comparison with those at lower latitudes in the world [10]. However there is considerable variability in blue carbon captured in that organismal growth,

**Figure 6.** Continental shelf monitoring sites of the changing Arctic Ocean seabed (ChAOS) project, through the Barents

Blue Carbon on Polar and Subpolar Seabeds http://dx.doi.org/10.5772/intechopen.78237 47

A new multi-year, multi-project investigation of the Atlantic sector of the Arctic, 'Changing Arctic Ocean', should elucidate the nature and dynamics of hyperboreal carbon pathways. Of these the Changing Arctic Ocean Seabed (ChAOS) project lead by Leeds University, UK is monitoring oceanography, geochemistry and biology at a latitudinal series of sites along the Barents Sea trough (**Figure 6**). Results from new initiatives like these should greatly increase our ability to estimate the value and variability of Arctic blue carbon ecosystem services [5, 9] and crucially how it is likely to respond to the very considerable, recent physical changes.

**Figure 6.** Continental shelf monitoring sites of the changing Arctic Ocean seabed (ChAOS) project, through the Barents Sea.

#### **2.3. Seasonal and annual increment (growth)**

dynamics, both in the water column [20] and the seabed [17]. As a result there is strong con-

The polar regions, particularly the Southern Ocean, are typically the most thermally constant surface regions of our planet. Annual polar sea temperature variability is generally less than 4°C in the Southern hemisphere but more geographically variable around the Arctic. A major source of variability has been Milankovitch 41 and 101 kyr Earth orbital cycles but this has been overshadowed in the Arctic by rapid, recent, regional climate change. Temperature can theoretically influence blue carbon through influences of ocean chemistry, sea ice formation and duration and physical constraints on enzyme performance, effecting food processing, carbonate synthesis and biomass growth rates. Ashton et al. [21] recently attempted to manipulate polar seabed temperature, whilst leaving other factors unchanged. Their study at Rothera Research Station (WAP), which established a series of temperature controlled artificial substrata, found that temperature had a stronger and more complex influence on growth than expected. A 1°C increase led to a significant increase in blue carbon (but measured as growth increment) whereas responses to a 2°C increase resulted in increased variance of assemblages. The major surprise was the extent of the increased growth (approximately double), which far exceeded that predicted by calculations of a pure temperature effect. The experimental infrastructure has now been transferred to the Canadian Arctic station of Cambridge Bay to compare the response of raised temperature of northern to southern polar nearshore fauna.

Many environmental factors are likely to influence blue carbon capture and storage rates around polar seas but our knowledge and understanding of these is patchy. Amongst the best studied locations are King George Island (South Shetland Islands, Antarctic Peninsula) in the south and West Spitsbergen (Svalbard) in the North. Multinational, interdisciplinary efforts to study biotic interactions to a multitude of environmental parameters at such places are enabling scientists to examine which factors are most important, to which organism types and to which stages of the carbon pathway. In contrast to Ryder Bay, adjacent to Rothera Research Station, where ice scouring [16, 17] and temperature [21] seem to be most important to carbon storage, at Potter Cove, King George Island, sedimentation mainly dictates the composition and performance of benthos. Sahade et al.'s [22] monitoring of that cove since 1998 showed that amongst the many varying factors for benthic life close to a retreating glacier, it was sediment levels and tolerance to this which drove drastic shifts in organism type. However sedimentation is not only co-linked to other variability such as salinity and nutrients but also varies in several different aspects, such as particle density and particle size distributions.

A new multi-year, multi-project investigation of the Atlantic sector of the Arctic, 'Changing Arctic Ocean', should elucidate the nature and dynamics of hyperboreal carbon pathways. Of these the Changing Arctic Ocean Seabed (ChAOS) project lead by Leeds University, UK is monitoring oceanography, geochemistry and biology at a latitudinal series of sites along the Barents Sea trough (**Figure 6**). Results from new initiatives like these should greatly increase our ability to estimate the value and variability of Arctic blue carbon ecosystem services [5, 9] and crucially how it is likely to respond to the very considerable, recent physical changes.

nectivity between temperature, ice changes and blue carbon.

*2.2.6. Other factors (sedimentation and water chemistry)*

*2.2.5. Temperature as a factor*

46 Carbon Capture, Utilization and Sequestration

Organisms incrementally capture and store carbon with distinct seasonal and annual variation (mainly caused by feeding reduction or cessation in winter). These temporal signals in carbon accumulation are externally visible in some organisms and observable in others by section (like tree rings) or through isotopic analyses. Thus one of the easiest approaches to measure carbon capture and storage on the seabed is to sequentially sample benthic growth to establish its variance. Because of the multitude of environmental factors influencing the magnitude of these (Section 2.2 above), simultaneous measurement of many local parameters needs to be made, in order to detect and understand any organismal performance trends. Growth (along with other processes, e.g. development) is typically considered to be slow in polar ectotherm organisms, in comparison with those at lower latitudes in the world [10]. However there is considerable variability in blue carbon captured in that organismal growth, within and between regions, organisms, environments and time. Partitioning out the causes and effects of variability is key to meaningful estimates of blue carbon stocks and how they are likely to change. For example, young animals are likely to have higher specific growth rates (thus have high carbon capture but low storage values) whereas older animals would typically be larger but grow slower (and thus be associated with low carbon capture but high carbon storage values). Thus an event influencing population demographics (e.g. iceberg scour) could change carbon capture relative to storage rates, and this could alter depend on which season it occurred in.

which have also increased carbon capture in the water column through ocean fertilization [20]. Duprat et al. [20] estimated the increases in water column blue carbon of a number of such icebergs. Those estimates were later built upon in terms of their total blue carbon impact (trade-offs of creating new sink areas and ocean fertilization versus scouring potential) to

shelf losses, iceberg production and arctic forest increases [2] are not the only sources of blue

Sea ice extent, particularly 'fast ice' (the freezing of the sea surface, anchored to land) has been one of the most drastic physical changes in the polar regions, particularly throughout the Arctic. Sea ice changes and primary production responses have been more complex around Antarctica [25], but crucially most sea ice losses have been over productive continental shelf whereas most of the sea ice gains have been over deeper slope and abyssal ocean depths [16]. Historical expedition zoobenthic collections and modern samples of longer lived animals with relevant information in skeletons has shown that blue carbon capture rates may have doubled over the last 25 years around West Antarctica [26]. The mechanism for this seems to be that reduced extent (in time and space) of sea ice leads to longer (but not necessarily larger biomass) phytoplankton blooms, resulting in longer meal times for primary consumers resulting in more carbon storage as growth (**Figure 7**). The total blue carbon increases driven by sea ice losses [17, 26] probably greatly exceed those caused by ice shelf collapse/giant iceberg formation [17–20]. However, from what we currently know, change in polar blue carbon is a complex of increases

**Figure 7.** Schematic showing influence of ozone losses on phytoplankton carbon capture and zoobenthic carbon storage

tons of carbon per year [17]. Ice

Blue Carbon on Polar and Subpolar Seabeds http://dx.doi.org/10.5772/intechopen.78237 49

iceberg contributes a net positive of 10<sup>6</sup>

show a 5000 km<sup>2</sup>

on polar seabeds.

carbon change around the polar regions.

Recent work in the Ross, Weddell and Bellingshausen seas have shown rapid growth rates, and changes in growth rates, are possible in polar organisms. Such blue carbon change has happened in response to wind-driven or ice shelf collapse promoted increased food availability [18, 19, 23] respectively, or increase in temperature [21]. With carbon sinks, sources and flux values being so important to global climate as well as projecting trends and predicting future scenarios it is clear that quantification of blue carbon has an important role in this, and the polar regions are the most poorly known. Understanding biological response to polar change has become even more important since it has become apparent that amongst the most severe physical changes have been associated with these areas.
