Difference between revisions of "Effects of climate change on the North Atlantic benthos"

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In the North Atlantic, temporal changes in deep-sea communities at the Porcupine Abyssal
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== The Amperima event ==
Plain (PAP), at 4,850m water depth, have been studied since 1989. Recently it has been studied within the [http://www.marbef.org/ MarBEF] [http://www.marbef.org/projects/deepsets/index.php DEEPSETS] project.
 
  
Shifts in the [[benthic]] biota of the deep-sea communities at the Porcupine Abyssal Plain have been recorded over decadal as well as shorter (seasonal) time-scales and attributed to the North Atlantic Oscillation.
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In the [[:Category:North Atlantic|North Atlantic]], temporal changes in [[Deep sea habitat|deep-sea]] communities at the Porcupine Abyssal Plain (PAP), at 4,850m water depth, have been studied since 1989. In the period 2005-2008 it has been studied within the MarBEF project DEEPSETS.  
  
While [[intra-annual]] changes reflect seasonal productivity cycles, the decadal-scale changes at the PAP are believed to be linked to the [[North Atlantic Oscillation]], a climatic phenomenon that affects winds, precipitation and storm intensity and frequency.  
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While [[intra-annual]] changes reflect seasonal [[Biological productivity|productivity]] cycles, the decadal-scale changes at the PAP are believed to be linked to the [[North Atlantic Oscillation]], a climatic phenomenon that affects winds, precipitation and storm intensity and frequency.  
  
These oscillations lead to changes in upper ocean biology and in the export of particulate organic carbon (POC) from the [[euphotic zone]] (i.e., the export flux) and to the
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These oscillations lead to changes in the amount and quality of particulate organic carbon (POC) that is exported from the surface layer to the sea floor. These changes in food quantity and quality probably explain the ‘boom-bust’ cycles (rapid abundance increases followed by declines) observed in the [[megafauna]] [http://www.marinespecies.org/aphia.php?p=taxdetails&id=123456 holothurians] [http://www.marinespecies.org/aphia.php?p=taxdetails&id=124723 ''Amperima rosea''] and ''Ellipinion molle'', during the period from 1996 to 2005. The rise to dominance of ''A. rosea'' during 1996 has been called the ‘Amperima event.’  
sea floor, as well as in the quality (biochemistry)
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of the material that reaches the sea floor. These
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Two larger holothurian species, [http://www.marinespecies.org/aphia.php?p=taxdetails&id=124778 ''Psychropotes longicauda''] and [http://www.marinespecies.org/aphia.php?p=taxdetails&id=389029 ''Pseudostichopus aemaulatus''], increased more slowly, while a third, [http://www.marinespecies.org/aphia.php?p=taxdetails&id=124720 ''Oneirophanta mutabilis''], underwent a significant decrease over the entire observation period. Increases in holothurian densities led to a dramatic increase in the extent to which surface sediments, and particularly deposits of phytodetritus (organic detritus derived from surface primary production), were reworked. Probably as a result, there was little phytodetritus on the seafloor between 1997 and 1999<ref name="ma">[https://www.researchgate.net/publication/306030378_Marine_Biodiversity_and_Ecosystem_Functioning Heip, C., Hummel, H., van Avesaath, P., Appeltans, W., Arvanitidis, C., Aspden, R., Austen, M., Boero, F., Bouma, TJ., Boxshall, G., Buchholz, F., Crowe, T., Delaney, A., Deprez, T., Emblow, C., Feral, JP., Gasol, JM., Gooday, A., Harder, J., Ianora, A., Kraberg, A., Mackenzie, B., Ojaveer, H., Paterson, D., Rumohr, H., Schiedek, D., Sokolowski, A., Somerfield, P., Sousa Pinto, I., Vincx, M., Węsławski, JM., Nash, R. (2009). Marine Biodiversity and Ecosystem Functioning. Printbase, Dublin, Ireland ISSN 2009-2539]</ref>.
changes in food quantity and quality (for
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<P>
example, the content of pigments necessary for
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<BR>
reproduction) probably underlie the ‘boombust’
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<P>
cycles observed in the holothurians
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===Impact on foraminifera===
Amperima rosea and Ellipinion molle. Vastly
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increased populations of these small surfacefeeding
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The densities of foraminifera were significantly higher in the post-Amperima event period (1996- 2002) compared to the pre-Amperima event period (1989-1994). Their species composition also changed over this period. In 1996, following a phytodetritus pulse, the [http://www.marinespecies.org/aphia.php?p=taxdetails&id=111898 miliolid] [http://www.marinespecies.org/aphia.php?p=taxdetails&id=112040 ''Quinquiloculina sp.'']  migrated to the sediment surface, grew and reproduced before migrating back into deeper layers as the phytodetrital food became exhausted. A substantial increase in the abundance of [http://www.marinespecies.org/aphia.php?p=taxdetails&id=111975 trochamminaceans] was observed. This may have reflected the qualitative change in the phytodetrital food, the repackaging of food by megafauna, the increased megafaunal disturbance, or a combination of these factors.
organisms may, in turn, have affected
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foraminiferal and meiofaunal populations
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Thus, the PAP time-series suggests that the decadal-scale changes among the shallow-[[infauna|infaunal]] foraminifera, more or less coincided with changes in the megafauna, as well as with shorter term events related to seasonally-pulsed phytodetrital inputs<ref name="ma"/>.
through depletion of food resources and
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sediment disturbance. A similar relationship
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[[Image:16.JPG|thumb|centre|700px| <div>
between climate, sea-surface processes and
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Schematic diagram illustrating forcing factors that influence temporal processes in ’normal’ sedimented parts of the deep-sea and in chemosynthetic systems. In the first case, temporal changes are forced ultimately by climatic oscillations. In the second case, they are forced by geological processes that affect fluid flow.</div>]]
deep-sea benthos appears to exist in the
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<P>
NE Pacific Ocean.
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<BR>
The most obvious changes at the PAP were seen
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<P>
among the megafauna (animals visible in seabottom
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photographs and trawls), notably the
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===Meiofauna===
holothurians Amperima rosea and Ellipinion
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Densities of animal [[meiofauna]] increased significantly between 1989 and 1999, mainly because of increases in the dominant [[taxon]], the [http://www.marinespecies.org/aphia.php?p=taxdetails&id=799 nematodes], and to a lesser extent the [http://www.marinespecies.org/aphia.php?p=taxdetails&id=883 polychaetes]. [http://www.marinespecies.org/aphia.php?p=taxdetails&id=1078 Ostracods] showed a significant decrease while most other taxa, including the [http://www.marinespecies.org/aphia.php?p=taxdetails&id=1080 copepods], did not exhibit significant temporal changes in abundance.  
molle. These relatively small species both
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exhibited ‘boom-bust’ cycles - rapid
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The proportion of nematodes and copepods (but not polychaetes) which inhabited the 0-1cm layer of the sediment also increased in time. The vertical distribution of nematodes also showed seasonal variations during the intensively sampled 1996-97 period<ref name="ma"/>.
abundance increases followed by declines –
+
<P>
during the period from 1996 to 2005. The rise
+
<BR>
to dominance of A. rosea during 1996 has been
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<P>
termed the ‘Amperima event.’ Two larger
+
 
holothurian species, Psychropotes longicauda
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===Macrofauna===
and Pseudostichopus aemulatus, exhibited
+
 
more modest increases while a third,
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[[Macrofauna|Macrofaunal]] polychaetes exhibited a more muted response to changes at the Porcupine Abyssal Plain (PAP). Although their abundance increased significantly before and during the Amperima event, it was not on the same scale as that observed in the megafauna. Moreover, only certain taxa and [[trophic level|trophic]] groups responded.  
Oneirophanta mutabilis, underwent a significant
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decrease over the entire time-series. Increases
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Only six of the twelve most abundant species showed a significant response (increased abundance ) during the Amperima event. The fact that only some polychaete species responded may be related to the efficient foraging by megafaunal [[Functional_diversity#Classification_by_functional_feeding_mechanism|deposit feeders]], leaving less available for smaller organisms.  
in holothurian densities led to a dramatic
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<P>
increase in the extent to which surface
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The polychaetes indicate that changes in the upper ocean which affect the ocean floor may operate in a complex way and that high [[taxonomy|taxonomic]] resolution is needed to establish how the fauna responds<ref name="ma"/>.
sediments, and particularly deposits of
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<P>
phytodetritus (organic detritus derived from
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<BR>
surface primary production), were reworked.
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<P>
Probably as a result of these activities, there
+
 
was little sign of phytodetritus on the seafloor
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== The deep Arctic ==
between 1997 and 1999.
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Among smaller organisms, densities of
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In the [[:Category:Arctic|Arctic]], work by the [http://www.awi.de/en Alfred-Wegener Institute] in Bremerhaven demonstrated a small but important temperature increase between 2000 and 2008 at 2.500m depth in the Fram Strait between Svalbard and Greenland. Within DEEPSETS, a five-year (2000-2004) time-series study of nematodes at this site revealed shifts in nematode abundance and community composition, reflecting changes in food availability. For the larger organisms, a towed camera system revealed a significant decrease in megafauna densities at 2.500m water depth<ref name="ma"/>.
foraminifera were significantly higher in 1996-
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<P>
2002 (post-Amperima event) compared to
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<BR>
1989-1994 (pre-Amperima event). The
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<P>
species-level composition of the assemblages
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changed over this period, reflecting fluctuations
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==References==
in the densities of higher taxa and species. In
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<references/>
1996, following a phytodetritus pulse, the
+
<P>
miliolid Quinquiloculina sp. migrated to the
+
<BR>
sediment surface, grew and reproduced before
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[[Category:Climate change, impacts and adaptation]]
migrating back into deeper layers as the
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[[Category:North Atlantic‎]]
phytodetrital food became exhausted. A
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[[Category: MarBEF Wiki]]
substantial increase in the abundance of
 
trochamminaceans, notably one small,
 
undescribed species, may have reflected
 
qualitative change in the phytodetrital food,
 
repackaging of food by megafauna, increased
 
megafaunal disturbance of the surficial
 
sediment, or a combination of these factors.
 
Thus, the PAP time-series suggests that
 
decadal-scale changes have occurred among
 
shallow-infaunal foraminifera at this site, more
 
or less coincident with changes in the
 
megafauna, as well as indications of shorterterm
 
events related to seasonally-pulsed
 
phytodetrital inputs.
 
Densities of metazoan meiofauna increased
 
significantly between 1989 and 1999, driven
 
mainly by the dominant taxon, the nematodes,
 
and to a lesser extent the polychaetes.
 
Ostracods showed a significant decrease while
 
most other taxa, including the second-ranked
 
group, the copepods (harpacticoids and
 
nauplii), did not exhibit significant temporal
 
changes in abundance. MDS ordination of
 
higher taxon composition showed a significant
 
shift from the earlier (pre-Amperima, 1989-
 
1994) to the later (1996-1999, post-Amperima)
 
periods. There were also significant increases
 
over time in the proportion of total meiofauna,
 
nematodes and copepods (but not polychaetes)
 
inhabiting the 0-1cm layer. In addition,
 
seasonal changes in the vertical distribution
 
patterns of total meiofauna and nematodes
 
within the sediment were apparent during the
 
intensively sampled period, 1996-97.
 
Macrofaunal polychaetes exhibited a more
 
muted response to changes at the Porcupine
 
Abyssal Plain. Although the abundance of the
 
whole assemblage increased significantly before
 
and during the Amperima event, the increase
 
was not on the same scale as that observed in
 
the megafauna, and only certain taxa and trophic
 
groups responded. The same dominant species
 
occurred throughout the study period, with the
 
exception of the Paraonidae, where the dominant
 
species declined prior to the Amperima event
 
and was replaced by two other species. Only six
 
of the 12 most abundant species showed a
 
significant response (abundance increase) during
 
the Amperima event. The fact that only some
 
polychaete species responded may be related to
 
efficient foraging by megafaunal deposit feeders
 
that sequestered and repackaged organic matter,
 
leaving less available for smaller organisms. Yet
 
there did not appear to be an impact from
 
physical disturbance caused by megafaunal
 
feeding activities. For example, surface deposit
 
feeders increased during the Amperima event at
 
the same time as disturbance of the surficial
 
sediment by holothurians and ophiuroids was
 
also increasing. The polychaetes indicate that
 
changes in the upper ocean which affect the
 
ocean floor may operate in a complex way and
 
that high taxonomic resolution is needed to
 
establish how the fauna responds.
 
Temporal changes in the deep sea are
 
not confined to the deep Abyssal Plains;
 
changes have also been recorded in the
 
Arctic and the Mediterranean.
 
In the Arctic, work by the Alfred-Wegener
 
Institute in Bremerhaven demonstrated a small
 
but important temperature increase between
 
2000 and 2008 at 2,500m depth in the Fram
 
Strait between Svalbard and Greenland. Within
 
DEEPSETS, a five-year (2000-2004) time-series
 
study of nematodes at this site revealed shifts
 
in nematode abundance and community
 
composition, reflecting changes in food
 
availability.
 
Although depth-related changes were more
 
prominent than shifts relating to sampling year,
 
interannual variability in nematode community
 
structure was clearly apparent, particularly at
 
the 4,000m station. Parallel observations at
 
several water depths indicated that most of the
 
variation over the time-series was the result of
 
real temporal changes, driven by shifts in food
 
availability as measured by sediment-bound
 
phaeopigment and chlorophyll a
 
concentrations. For the larger organisms, a
 
towed camera system revealed a significant
 
decrease in megafauna densities at 2,500m
 
water depth.
 

Latest revision as of 17:30, 22 February 2021

The Amperima event

In the North Atlantic, temporal changes in deep-sea communities at the Porcupine Abyssal Plain (PAP), at 4,850m water depth, have been studied since 1989. In the period 2005-2008 it has been studied within the MarBEF project DEEPSETS.

While intra-annual changes reflect seasonal productivity cycles, the decadal-scale changes at the PAP are believed to be linked to the North Atlantic Oscillation, a climatic phenomenon that affects winds, precipitation and storm intensity and frequency.

These oscillations lead to changes in the amount and quality of particulate organic carbon (POC) that is exported from the surface layer to the sea floor. These changes in food quantity and quality probably explain the ‘boom-bust’ cycles (rapid abundance increases followed by declines) observed in the megafauna holothurians Amperima rosea and Ellipinion molle, during the period from 1996 to 2005. The rise to dominance of A. rosea during 1996 has been called the ‘Amperima event.’

Two larger holothurian species, Psychropotes longicauda and Pseudostichopus aemaulatus, increased more slowly, while a third, Oneirophanta mutabilis, underwent a significant decrease over the entire observation period. Increases in holothurian densities led to a dramatic increase in the extent to which surface sediments, and particularly deposits of phytodetritus (organic detritus derived from surface primary production), were reworked. Probably as a result, there was little phytodetritus on the seafloor between 1997 and 1999[1].


Impact on foraminifera

The densities of foraminifera were significantly higher in the post-Amperima event period (1996- 2002) compared to the pre-Amperima event period (1989-1994). Their species composition also changed over this period. In 1996, following a phytodetritus pulse, the miliolid Quinquiloculina sp. migrated to the sediment surface, grew and reproduced before migrating back into deeper layers as the phytodetrital food became exhausted. A substantial increase in the abundance of trochamminaceans was observed. This may have reflected the qualitative change in the phytodetrital food, the repackaging of food by megafauna, the increased megafaunal disturbance, or a combination of these factors.

Thus, the PAP time-series suggests that the decadal-scale changes among the shallow-infaunal foraminifera, more or less coincided with changes in the megafauna, as well as with shorter term events related to seasonally-pulsed phytodetrital inputs[1].

Schematic diagram illustrating forcing factors that influence temporal processes in ’normal’ sedimented parts of the deep-sea and in chemosynthetic systems. In the first case, temporal changes are forced ultimately by climatic oscillations. In the second case, they are forced by geological processes that affect fluid flow.


Meiofauna

Densities of animal meiofauna increased significantly between 1989 and 1999, mainly because of increases in the dominant taxon, the nematodes, and to a lesser extent the polychaetes. Ostracods showed a significant decrease while most other taxa, including the copepods, did not exhibit significant temporal changes in abundance.

The proportion of nematodes and copepods (but not polychaetes) which inhabited the 0-1cm layer of the sediment also increased in time. The vertical distribution of nematodes also showed seasonal variations during the intensively sampled 1996-97 period[1].


Macrofauna

Macrofaunal polychaetes exhibited a more muted response to changes at the Porcupine Abyssal Plain (PAP). Although their abundance increased significantly before and during the Amperima event, it was not on the same scale as that observed in the megafauna. Moreover, only certain taxa and trophic groups responded.

Only six of the twelve most abundant species showed a significant response (increased abundance ) during the Amperima event. The fact that only some polychaete species responded may be related to the efficient foraging by megafaunal deposit feeders, leaving less available for smaller organisms.

The polychaetes indicate that changes in the upper ocean which affect the ocean floor may operate in a complex way and that high taxonomic resolution is needed to establish how the fauna responds[1].


The deep Arctic

In the Arctic, work by the Alfred-Wegener Institute in Bremerhaven demonstrated a small but important temperature increase between 2000 and 2008 at 2.500m depth in the Fram Strait between Svalbard and Greenland. Within DEEPSETS, a five-year (2000-2004) time-series study of nematodes at this site revealed shifts in nematode abundance and community composition, reflecting changes in food availability. For the larger organisms, a towed camera system revealed a significant decrease in megafauna densities at 2.500m water depth[1].


References