149
open ocean, deep and shallow water (Vader et al. 2015),
which is particularly interesting as our knowledge regarding
processes during the dark season was limited for a long time
due to logistic difficulties with conducting research in winter. It should be taken into account that temperature increase
and decrease in sea ice cover may influence the community
structure of microorganisms and this effect has the potential
to be translated to all upper trophic levels (Berge et al. 2015).
One of the most common methods used in the analysis of
microorganisms, is barcoding based on the comparison of
DNA and RNA derived OTU. While DNA is a very stable
molecule and able to persist outside of the source organism for
a long time, RNA is less stable and degrades rapidly. RNA
analysis is therefore useful in informing about the current situation in the water column. In Svalbard waters, 4000 OTUs
were differentiated based on DNA and only 2000 OTUs based
on RNA (Marquardt et al. 2016). Differences can be explained
by the fact that DNA is stable and may be present in the water
column even after the death of an organism, but may also be
caused by the high number copies of rRNA genes (Gong et al.
2013). The result of this research based on molecular data, has
shown a high activity of heterotrophic groups during the polar
night. It also revealed that species considered as autotrophic
can become mixotrophic during winter. Based on a seasonal
analysis of DNA and RNA, a succession of different microbial
groups was demonstrated and their presence explained by particular environmental preferences, which may suggest that
increasing temperatures will significantly influence community composition (Marquardt et al. 2016). Another study, in
which microorganism communities were compared before
and after the Record Sea Ice Minimum in the Arctic in 2007
(next were observed in 2012 and 2016), the genetic diversity
of microorganisms appeared to be much lower (Comeau et al.
2011). This may be the result of particular adaptations to the
sea-ice environment, as some are known to belong to the sympagic community. Differences in the community composition
of Bacteria and Archaea, responsible for carbon and nutrient
cycles, may influence productivity, but also the release of CO 2
from the Arctic Ocean (Legendre and Le Fèvre 1995). These
findings underline the importance of future research focusing
on the ecology and functions of microorganisms to predict
consequences of forthcoming changes.
Benthos
Some areas of the Arctic Ocean, especially the continental
shelves, are well-recognized for their tight bentho-pelagic
coupling, inferred from the high amount of carbon fixed near
the oceans’ surface that sinks ungrazed to the seafloor, where
it fuels benthic communities (Ambrose Jr. and Renaud 1995;
Renaud et al. 2008). In the Arctic, biogenic sedimentation is
far greater than at lower latitudes, thus explaining the high
biomass of benthos thriving there (Petersen and Curtis 1980;
Ambrose Jr. and Renaud 1995). Even with winter-limited
primary production these benthic communities are relatively
stable (Dunton et al. 2005).
The Arctic benthos is composed of a relatively young
community that acquired lot of its current form during
Quaternary glaciations (Zenkevitch 1963). The ice-mediated
inflow and -outflow of mature organisms and their offspring,
the isolation in refugia, and species extinctions led to the
present day state of the Arctic benthic biodiversity (Hardy
et al. 2011; Ronowicz et al. 2015). Although much is known
about the current state of the Arctic benthos, a higher spatial
and taxonomic resolution for biodiversity data is needed for
an improved inferring of its future.
High phenotypic plasticity (e.g., in body pigmentation)
further impedes species identification and hence the understanding of environmentally-dependent spatial diversification of benthic communities (Hardy et al. 2011).
Bottom-dwelling polychaetes of the Arctic properly portray
this trend. Until recently, this speciose group was perceived
as lacking geographic structure on the global scale (Fauchald
1984). However, the use of molecular methods revealed
numerous phenotypically indistinctive sibling species whilst
it confirmed the presumed cosmopolitism of others (Carr
et al. 2011). Hence, morphology-based taxonomy coupled
with COI barcoding better resolved the diversity of Arctic
polychaetes, showing that almost 25% of the over 300 “species” examined, were in fact complexes of two or more
divergent lineages (Carr et al. 2011). Using COI sequences,
Carr et al. (2011), were also able to retrace possible historical changes in distribution ranges of polychaetes found on
Canadian coast of the Arctic, suggesting the Pleistocene glaciation as the main factor responsible of the increased diversification observed in this taxon.
Similar studies were conducted on echinoderms of the
Canadian Arctic (Layton et al. 2016). Out of 141 taxa examined, 118 constituted morphologically distinctive species,
while the remaining 23 were taxa assigned to different genera but not representing recognized species (Layton et al.
2016). It may suggest that in this area 23 morphologically
indistinctive species new to science, or new for this region,
may exist. Interestingly, with the sole usage of COI
sequences, these authors also discussed various aspects of
the phylogeography of echinoderms. For example, they
pointed out that all species, where no pronounced spatial
genetic structure could be observed between specimens collected in two or three oceanic regions of Canada, possessed a
planktonic larval stage, which may justify the high levels of
gene flow (Layton et al. 2016).
The above examples illustrate the utility of barcoding in
delineation of the species composing the benthic communities of shallow shelf areas of the Arctic. Unfortunately, similar studies, focusing on the deep ocean assemblage remain
uncommon, mostly because of the obvious difficulties of
sampling below certain depths (Layton et al. 2016). One of
Arctic Ocean Biodiversity and DNA Barcoding – A Climate Change Perspective
open ocean, deep and shallow water (Vader et al. 2015),
which is particularly interesting as our knowledge regarding
processes during the dark season was limited for a long time
due to logistic difficulties with conducting research in winter. It should be taken into account that temperature increase
and decrease in sea ice cover may influence the community
structure of microorganisms and this effect has the potential
to be translated to all upper trophic levels (Berge et al. 2015).
One of the most common methods used in the analysis of
microorganisms, is barcoding based on the comparison of
DNA and RNA derived OTU. While DNA is a very stable
molecule and able to persist outside of the source organism for
a long time, RNA is less stable and degrades rapidly. RNA
analysis is therefore useful in informing about the current situation in the water column. In Svalbard waters, 4000 OTUs
were differentiated based on DNA and only 2000 OTUs based
on RNA (Marquardt et al. 2016). Differences can be explained
by the fact that DNA is stable and may be present in the water
column even after the death of an organism, but may also be
caused by the high number copies of rRNA genes (Gong et al.
2013). The result of this research based on molecular data, has
shown a high activity of heterotrophic groups during the polar
night. It also revealed that species considered as autotrophic
can become mixotrophic during winter. Based on a seasonal
analysis of DNA and RNA, a succession of different microbial
groups was demonstrated and their presence explained by particular environmental preferences, which may suggest that
increasing temperatures will significantly influence community composition (Marquardt et al. 2016). Another study, in
which microorganism communities were compared before
and after the Record Sea Ice Minimum in the Arctic in 2007
(next were observed in 2012 and 2016), the genetic diversity
of microorganisms appeared to be much lower (Comeau et al.
2011). This may be the result of particular adaptations to the
sea-ice environment, as some are known to belong to the sympagic community. Differences in the community composition
of Bacteria and Archaea, responsible for carbon and nutrient
cycles, may influence productivity, but also the release of CO 2
from the Arctic Ocean (Legendre and Le Fèvre 1995). These
findings underline the importance of future research focusing
on the ecology and functions of microorganisms to predict
consequences of forthcoming changes.
Benthos
Some areas of the Arctic Ocean, especially the continental
shelves, are well-recognized for their tight bentho-pelagic
coupling, inferred from the high amount of carbon fixed near
the oceans’ surface that sinks ungrazed to the seafloor, where
it fuels benthic communities (Ambrose Jr. and Renaud 1995;
Renaud et al. 2008). In the Arctic, biogenic sedimentation is
far greater than at lower latitudes, thus explaining the high
biomass of benthos thriving there (Petersen and Curtis 1980;
Ambrose Jr. and Renaud 1995). Even with winter-limited
primary production these benthic communities are relatively
stable (Dunton et al. 2005).
The Arctic benthos is composed of a relatively young
community that acquired lot of its current form during
Quaternary glaciations (Zenkevitch 1963). The ice-mediated
inflow and -outflow of mature organisms and their offspring,
the isolation in refugia, and species extinctions led to the
present day state of the Arctic benthic biodiversity (Hardy
et al. 2011; Ronowicz et al. 2015). Although much is known
about the current state of the Arctic benthos, a higher spatial
and taxonomic resolution for biodiversity data is needed for
an improved inferring of its future.
High phenotypic plasticity (e.g., in body pigmentation)
further impedes species identification and hence the understanding of environmentally-dependent spatial diversification of benthic communities (Hardy et al. 2011).
Bottom-dwelling polychaetes of the Arctic properly portray
this trend. Until recently, this speciose group was perceived
as lacking geographic structure on the global scale (Fauchald
1984). However, the use of molecular methods revealed
numerous phenotypically indistinctive sibling species whilst
it confirmed the presumed cosmopolitism of others (Carr
et al. 2011). Hence, morphology-based taxonomy coupled
with COI barcoding better resolved the diversity of Arctic
polychaetes, showing that almost 25% of the over 300 “species” examined, were in fact complexes of two or more
divergent lineages (Carr et al. 2011). Using COI sequences,
Carr et al. (2011), were also able to retrace possible historical changes in distribution ranges of polychaetes found on
Canadian coast of the Arctic, suggesting the Pleistocene glaciation as the main factor responsible of the increased diversification observed in this taxon.
Similar studies were conducted on echinoderms of the
Canadian Arctic (Layton et al. 2016). Out of 141 taxa examined, 118 constituted morphologically distinctive species,
while the remaining 23 were taxa assigned to different genera but not representing recognized species (Layton et al.
2016). It may suggest that in this area 23 morphologically
indistinctive species new to science, or new for this region,
may exist. Interestingly, with the sole usage of COI
sequences, these authors also discussed various aspects of
the phylogeography of echinoderms. For example, they
pointed out that all species, where no pronounced spatial
genetic structure could be observed between specimens collected in two or three oceanic regions of Canada, possessed a
planktonic larval stage, which may justify the high levels of
gene flow (Layton et al. 2016).
The above examples illustrate the utility of barcoding in
delineation of the species composing the benthic communities of shallow shelf areas of the Arctic. Unfortunately, similar studies, focusing on the deep ocean assemblage remain
uncommon, mostly because of the obvious difficulties of
sampling below certain depths (Layton et al. 2016). One of
Arctic Ocean Biodiversity and DNA Barcoding – A Climate Change Perspective