168 research outputs found
Spatial self-organization as a new perspective on cold-water coral mound development
Cold-water corals build extensive reefs on the seafloor that are oases of biodiversity, biomass, and organic matter processing rates. The reefs baffle sediments, and when coral growth and sedimentation outweigh ambient sedimentation, carbonate mounds of tens to hundreds of meters high and several kilometers wide can form. Because coral mounds form over ten-thousands of years, their development process remains elusive. While several environmental factors influence mound development, the mounds also have a major impact on their environment. This feedback between environment and mounds, and how this drives mound development is the focus of this paper. Based on the similarity of spatial coral mound patterns and patterns in self-organized ecosystems, we provide a new perspective on coral mound development. In accordance with the theory of self-organization through scale-dependent feedbacks, we first elicit the processes that are known to affect mound development, and might cause scale-dependent feedbacks. Then we demonstrate this concept with model output from a study on the Logachev area, SW Rockall Trough margin. Spatial patterns in mound provinces are the result of a complex set of interacting processes. Spatial self-organization provides a framework in which to place and compare these processes, so as to assess if and how they contribute to pattern formation in coral mounds
On the paradox of thriving cold-water coral reefs in the food-limited deep sea
The deep sea is amongst the most food-limited habitats on Earth, as only a small fraction (<4%) of the surface primary production is exported below 200âm water depth. Here, cold-water coral (CWC) reefs form oases of life: their biodiversity compares with tropical coral reefs, their biomass and metabolic activity exceed other deep-sea ecosystems by far. We critically assess the paradox of thriving CWC reefs in the food-limited deep sea, by reviewing the literature and open-access data on CWC habitats. This review shows firstly that CWCs typically occur in areas where the food supply is not constantly low, but undergoes pronounced temporal variation. High currents, downwelling and/or vertically migrating zooplankton temporally boost the export of surface organic matter to the seabed, creating âfeastâ conditions, interspersed with âfamineâ periods during the non-productive season. Secondly, CWCs, particularly the most common reef-builder Desmophyllum pertusum (formerly known as Lophelia pertusa), are well adapted to these fluctuations in food availability. Laboratory and in situ measurements revealed their dietary flexibility, tissue reserves, and temporal variation in growth and energy allocation. Thirdly, the high structural and functional diversity of CWC reefs increases resource retention: acting as giant filters and sustaining complex food webs with diverse recycling pathways, the reefs optimise resource gains over losses. Anthropogenic pressures, including climate change and ocean acidification, threaten this fragile equilibrium through decreased resource supply, increased energy costs, and dissolution of the calcium-carbonate reef framework. Based on this review, we suggest additional criteria to judge the health of CWC reefs and their chance to persist in the future.publishedVersio
Tiger reefs: Selfâorganized regular patterns in deepâsea coldâwater coral reefs
Complexity theory predicts that self-organized, regularly patterned ecosystems store more biomass and are more resilient than spatially uniform systems. Self-organized ecosystems are well-known from the terrestrial realm, with âtiger bushesâ being the archetypical example and mussel beds and tropical coral reefs the marine examples. We here identify regular spatial patterns in cold-water coral reefs (nicknamed âtiger reefsâ) from video transects and argue that these are likely the result of self-organization. We used variograms and LombâScargle analysis of seven annotated video transects to analyze spatial patterns in live coral and dead coral (i.e., skeletal remains) cover at the Logachev coral mound province (NE Atlantic Ocean) and found regular spatial patterns with length scales between 62 and 523âm in live and dead coral distribution along these transects that point to self-organization of cold-water coral reefs. Self-organization theory shows that self-organized ecosystems can withstand large environmental changes by adjusting their spatial configuration. We found indications that cold-water corals can similarly adjust their spatial configuration, possibly providing resilience in the face of climate change. Dead coral framework remains in the environment for extended periods of time, providing a template for spatial patterns that facilitates live coral recovery. The notion of regular spatial patterns in cold-water coral reefs is interesting for cold-water coral restoration, as transplantation will be more successful when it follows the patterns that are naturally present. This finding also underlines that anthropogenic effects such as ocean acidification and bottom trawling that destroy the dead coral template undermine cold-water coral resilience. Differences in the pattern periodicities of live and dead coral cover further present an interesting new angle to investigate past and present environmental conditions in cold-water coral reefs
Tiger reefs: Self-organized regular patterns in deep-sea cold-water coral reefs
Abstract Complexity theory predicts that self-organized, regularly patterned ecosystems store more biomass and are more resilient than spatially uniform systems. Self-organized ecosystems are well-known from the terrestrial realm, with âtiger bushesâ being the archetypical example and mussel beds and tropical coral reefs the marine examples. We here identify regular spatial patterns in cold-water coral reefs (nicknamed âtiger reefsâ) from video transects and argue that these are likely the result of self-organization. We used variograms and LombâScargle analysis of seven annotated video transects to analyze spatial patterns in live coral and dead coral (i.e., skeletal remains) cover at the Logachev coral mound province (NE Atlantic Ocean) and found regular spatial patterns with length scales between 62 and 523âm in live and dead coral distribution along these transects that point to self-organization of cold-water coral reefs. Self-organization theory shows that self-organized ecosystems can withstand large environmental changes by adjusting their spatial configuration. We found indications that cold-water corals can similarly adjust their spatial configuration, possibly providing resilience in the face of climate change. Dead coral framework remains in the environment for extended periods of time, providing a template for spatial patterns that facilitates live coral recovery. The notion of regular spatial patterns in cold-water coral reefs is interesting for cold-water coral restoration, as transplantation will be more successful when it follows the patterns that are naturally present. This finding also underlines that anthropogenic effects such as ocean acidification and bottom trawling that destroy the dead coral template undermine cold-water coral resilience. Differences in the pattern periodicities of live and dead coral cover further present an interesting new angle to investigate past and present environmental conditions in cold-water coral reefs
Reef communities associated with âdeadâ cold-water coral framework drive resource retention and recycling in the deep sea
Cold-water coral (CWC) reefs create hotspots of metabolic activity in the deep sea, in spite of the limited supply
of fresh organic matter from the ocean surface (i.e. phytodetritus). We propose that âdeadâ coral framework,
which harbours diverse faunal and microbial communities, boosts the metabolic activity of the reefs, through
enhanced resource retention and recycling. Analysis of a video transect across a 700-540 m-deep CWC mound
(Rockall Bank, North-East Atlantic) revealed a high benthic cover of dead framework (64%). Box-cored fragments
of dead framework were incubated on-board and showed oxygen consumption rates of 0.078â0.182 ÎŒmol
O2 (mmol organic carbon, i.e. OC)-1 h-1, indicating a substantial contribution to the total metabolic activity of
the CWC reef. During the incubations, it was shown that the framework degradation stage influences nitrogen
(re)cycling, corresponding to differences in community composition. New (less-degraded) framework released
ammonium (0.005 ± 0.001 Όmol NH4+ (mmol OC) 1 h 1), probably due to the activity of ammonotelic macrofauna.
In contrast, old (more-degraded) framework released nitrate (0.015 ± 0.008 Όmol NO3- (mmol OC)- 1
h- 1), indicating that nitrifying microorganisms recycled fauna-excreted ammonium to nitrate. Furthermore, the
framework community removed natural dissolved organic matter (DOM) from the incubation water
(0.005â0.122 ÎŒmol C (mmol OC)- 1 h- 1). Additional feeding experiments showed that all functional groups and
macrofauna taxa of the framework community incorporated 13C-enriched (âlabelledâ) DOM, indicating widespread
DOM uptake and recycling. Finally, the framework effectively retained 13C-enriched phytodetritus, (a) by
physical retention on the biofilm-covered surface and (b) by biological filtration through suspension-feeding
fauna. We therefore suggest that the dead framework acts as a âfiltration-recycling factoryâ that enhances the
metabolic activity of CWC reefs. The exposed framework, however, is particularly vulnerable to ocean acidification,
jeopardizing this important aspect of CWC reef functioning
The global correlation between internal-tide generation and the depth-distribution of cold-water corals
Internal tides are known to be an important source of mixing in the oceans, especially in the bottom boundary layer. The depth of internal-tide generation therefore seems important for benthic life and the formation of cold-water coral mounds, but internal-tidal conversion is generally investigated in a depth-integrated sense. Using both idealized and realistic simulations on continental slopes, we found that the depth of internal-tide generation increases with increasing slope steepness and decreases with intensified shallow stratification. The depth of internal-tide generation also shows a typical latitudinal dependency. Using a global database of cold-water corals, we found that the depth-pattern of internal-tide generation is remarkably similar to the depth-pattern of cold-water corals globally: shallowest near the poles and deepest around the equator with a shoaling around 25 degrees South and North and shallower north of the equator than south of the equator. We further found that cold-water corals are, more than what would be expected by chance, associated to the (super)critical reflection of internal tides (i.e., situated on topography that is steeper than the internal tidal beam) and to trapped internal tides (i.e., above the critical latitude of 70 degrees for semidiurnal tides and 30 degrees for diurnal tides). The (super)critical reflection of internal tides and trapped internal tides therefore provide an interesting new angle of food supply mechanisms that has not yet been considered in cold-water coral studies. With climate change, stratification is expected to increase. Based on our results, this would cause a shoaling of internal-tide generation, possibly creating new shallower suitable habitat for cold-water corals on continental slopes
Building your own mountain: the effects, limits, and drawbacks of cold-water coral ecosystem engineering
Framework-forming cold-water corals (CWCs) are ecosystem engineers that build mounds in the deep sea that can be up to several hundred metres high. The effect of the presence of cold-water coral mounds on their surroundings is typically difficult to separate from environmental factors that are not affected by the mounds. We investigated the environmental control on and the importance of ecosystem engineering for cold-water coral reefs using annotated video transect data, spatial variables (MEMs), and hydrodynamic model outputs in a redundancy analysis and with variance partitioning. Using available hydrodynamic simulations with cold-water coral mounds and simulations where the mounds were artificially removed, we investigated the effect of coral mound ecosystem engineering on the spatial configuration of reef habitat and discriminated which environmental factors are and which are not affected by the mounds.
We find that downward velocities in winter, related to non-engineered environmental factors, e.g. deep winter mixing and dense-water cascading, cause substantial differences in reef cover at the broadest spatial scale (20â30âkm). Such hydrodynamic processes that stimulate the food supply towards the corals in winter seem more important for the reefs than cold-water coral mound engineering or similar hydrodynamic processes in summer. While the ecosystem-engineering effect of cold-water corals is frequently discussed, our results also highlight the importance of non-engineered environmental processes.
We further find that, due to the interaction between the coral mound and the water flow, different hydrodynamic zones are found on coral mounds that likely determine the typical benthic zonations of coral rubble at the mound foot, the dead coral framework on the mound flanks, and the living corals near the summit. Moreover, we suggest that a so-called Massenerhebung effect (well known for terrestrial mountains) exists, meaning that benthic zonation depends on the location of the mound rather than on the height above the seafloor or water depth. Our finding that ecosystem engineering determines the configuration of benthic habitats on cold-water coral mounds implies that cold-water corals cannot grow at deeper depths on the mounds to avoid the adverse effects of climate change.</p
Biomass mapping for an improved understanding of the contribution of cold-water coral carbonate mounds to C and N cycling
This study used a novel approach combining biological, environmental, and ecosystem function data of the Logachev cold-water coral carbonate mound province to predictively map coral framework (bio)mass. A more accurate representation and quantification of cold-water coral reef ecosystem functions such as Carbon and Nitrogen stock and turnover were given by accounting for the spatial heterogeneity. Our results indicate that 45% is covered by dead and only 3% by live coral framework. The remaining 51%, is covered by fine sediments. It is estimated that 75,034â93,534 tons (T) of live coral framework is present in the area, of which âŒ10% (7,747â9,316 T) consists of Cinorg and âŒ1% (411â1,061 T) of Corg. A much larger amount of 3,485,828â4,357,435 T (60:1 dead:live ratio) dead coral framework contained âŒ11% (418,299â522,892 T) Cinorg and <1% (0â16 T) Corg. The nutrient turnover by dead coral framework is the largest, contributing 45â51% (2,596â3,626 T) C yearâ1 and 30â62% (290â1,989 T) N yearâ1 to the total turnover in the area. Live coral framework turns over 1,656â2,828 T C yearâ1 and 53â286 T N yearâ1. Sediments contribute between 1,216â1,512 T C yearâ1 and 629â919 T N yearâ1 to the areaâs benthic organic matter mineralization. However, this amount is likely higher as sediments baffled by coral framework might play a much more critical role in reefs CN cycling than previously assumed. Our calculations showed that the area overturns 1â3.4 times the C compared to a soft-sediment area at a similar depth. With only 5â9% of the primary productivity reaching the corals via natural deposition, this study indicated that the supply of food largely depends on local hydrodynamical food supply mechanisms and the reefs ability to retain and recycle nutrients. Climate-induced changes in primary production, local hydrodynamical food supply and the dissolution of particle-baffling coral framework could have severe implications for the survival and functioning of cold-water coral reefs
Biomass mapping for an improved understanding of the contribution of cold-water coral carbonate mounds to C and N cycling
This study used a novel approach combining biological, environmental, and ecosystem function data of the Logachev cold-water coral carbonate mound province to predictively map coral framework (bio)mass. A more accurate representation and quantification of cold-water coral reef ecosystem functions such as Carbon and Nitrogen stock and turnover were given by accounting for the spatial heterogeneity. Our results indicate that 45% is covered by dead and only 3% by live coral framework. The remaining 51%, is covered by fine sediments. It is estimated that 75,034â93,534 tons (T) of live coral framework is present in the area, of which âŒ10% (7,747â9,316 T) consists of Cinorg and âŒ1% (411â1,061 T) of Corg. A much larger amount of 3,485,828â4,357,435 T (60:1 dead:live ratio) dead coral framework contained âŒ11% (418,299â522,892 T) Cinorg and <1% (0â16 T) Corg. The nutrient turnover by dead coral framework is the largest, contributing 45â51% (2,596â3,626 T) C yearâ1 and 30â62% (290â1,989 T) N yearâ1 to the total turnover in the area. Live coral framework turns over 1,656â2,828 T C yearâ1 and 53â286 T N yearâ1. Sediments contribute between 1,216â1,512 T C yearâ1 and 629â919 T N yearâ1 to the areaâs benthic organic matter mineralization. However, this amount is likely higher as sediments baffled by coral framework might play a much more critical role in reefs CN cycling than previously assumed. Our calculations showed that the area overturns 1â3.4 times the C compared to a soft-sediment area at a similar depth. With only 5â9% of the primary productivity reaching the corals via natural deposition, this study indicated that the supply of food largely depends on local hydrodynamical food supply mechanisms and the reefs ability to retain and recycle nutrients. Climate-induced changes in primary production, local hydrodynamical food supply and the dissolution of particle-baffling coral framework could have severe implications for the survival and functioning of cold-water coral reefs
Isolated limb perfusion for local gene delivery: efficient and targeted adenovirus-mediated gene transfer into soft tissue sarcomas
OBJECTIVE: To evaluate the potential of isolated limb perfusion (ILP) for
efficient and tumor-specific adenovirus-mediated gene transfer in
sarcoma-bearing rats. SUMMARY BACKGROUND DATA: A major concern in
adenovirus-mediated gene therapy in cancer is the transfer of genes to
organs other than the tumor, especially organs with a rapid cell turnover.
Adjustment of the vector delivery route might be an option creating tumor
specificity in therapeutic gene expression. METHODS: Rat hind limb
sarcomas (5-10 mm) were transfected with recombinant adenoviruses.
Intratumoral luciferase expression after ILP was compared with systemic
administration, regional infusion, or intratumoral injection using a
similar dose of adenoviruses carrying the luciferase marker gene.
Localization studies using lacZ as a marker gene were performed to
evaluate the intratumoral distribution of transfected cells after both ILP
and intratumoral injection. RESULTS: Intratumoral luciferase activity
after ILP or intratumoral administration was significantly higher compared
with regional infusion or systemic administration. After ILP, luciferase
gene expression was minimal in extratumoral organs, whether outside or
inside the isolated circuit. Localization studies demonstrated that
transfection was confined to tumor cells lying along the needle track
after intratumoral injection, whereas after ILP, lacZ expression was found
in viable tumor cells and in the tumor-associated vasculature.
CONCLUSIONS: Using ILP, efficient and tumor-specific gene transfection can
be achieved. The ILP technique might be useful for the delivery of
recombinant adenoviruses carrying therapeutic gene constructs to enhance
tumor control
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